chapter 5 link layer
DESCRIPTION
CPE 400 / 600 Computer Communication Networks. Lecture 23. Chapter 5 Link Layer. slides are modified from J. Kurose & K. Ross. Ethernet. bus topology popular through mid 90s all nodes in same collision domain (can collide with each other) today: star topology prevails - PowerPoint PPT PresentationTRANSCRIPT
Chapter 5Link Layer
slides are modified from J Kurose amp K Ross
CPE 400 600Computer Communication Networks
Lecture 23
DataLink Layer 2
Ethernet bus topology popular through mid 90s
all nodes in same collision domain (can collide with each other)
today star topology prevails active switch in center each ldquospokerdquo runs a (separate) Ethernet protocol (nodes
do not collide with each other)
bus coaxial cable
switch
star
DataLink Layer 3
Ethernet Frame Structure
Sending adapter encapsulates IP datagram (or other network layer protocol packet) in Ethernet frame
Preamble 7 bytes with pattern 10101010 followed by one
byte with pattern 10101011 used to synchronize receiver sender clock
rates
DataLink Layer 4
Ethernet Frame Structure (more) Addresses 6 bytes
if adapter receives frame with matching destination address or with broadcast address (eg ARP packet) it passes data in frame to network layer protocol
otherwise adapter discards frame
Type indicates higher layer protocol (mostly IP but others possible eg Novell IPX AppleTalk)
CRC checked at receiver if error is detected frame is dropped
DataLink Layer 5
Ethernet CSMACD algorithm1 NIC receives datagram from network layer creates
frame
2 If NIC senses channel idle starts frame transmission If NIC senses channel busy waits until channel idle then transmits
3 If NIC transmits entire frame without detecting another transmission NIC is done with frame
4 If NIC detects another transmission while transmitting aborts and sends jam signal
5 After aborting NIC enters exponential backoff after mth collision NIC chooses K at random from 012hellip2m-1 NIC waits K512 bit times returns to Step 2
DataLink Layer 6
CSMACD efficiency Tprop = max prop delay between 2 nodes in LAN
ttrans = time to transmit max-size frame
efficiency goes to 1 as tprop goes to 0
as ttrans goes to infinity
better performance than ALOHA and simple cheap decentralized
transprop ttefficiency
51
1
DataLink Layer 7
8023 Ethernet Standards Link amp Physical Layers
many different Ethernet standards common MAC protocol and frame format
different speeds 2 Mbps 10 Mbps 100 Mbps 1Gbps 10G bps
different physical layer media fiber cable
application
transport
network
link
physical
MAC protocoland frame format
100BASE-TX
100BASE-T4
100BASE-FX100BASE-T2
100BASE-SX 100BASE-BX
fiber physical layercopper (twisterpair) physical layer
DataLink Layer 8
Hubshellip physical-layer (ldquodumbrdquo) repeaters
bits coming in one link go out all other links at same rate all nodes connected to hub can collide with one another no frame buffering no CSMACD at hub host NICs detect collisions
twisted pair
hub
DataLink Layer 9
Switch link-layer device smarter than hubs take active
role store forward Ethernet frames examine incoming framersquos MAC address selectively
forward frame to one-or-more outgoing links when frame is to be forwarded on segment uses CSMACD to access segment
transparent hosts are unaware of presence of switches
plug-and-play self-learning switches do not need to be configured
DataLink Layer 10
Switch allows multiple simultaneous transmissions
hosts have dedicated direct connection to switch
switches buffer packets Ethernet protocol used on
each incoming link but no collisions full duplex each link is its own collision
domain
switching A-to-Arsquo and B-to-Brsquo simultaneously without collisions not possible with dumb hub
A
Arsquo
B
Brsquo
C
Crsquo
switch with six interfaces(123456)
1 23
45
6
DataLink Layer 11
Switch frame filteringforwardingWhen frame received
1 record link associated with sending host
2 index switch table using MAC dest address
3 if entry found for destination then
if dest on segment from which frame arrived then drop the frame
else forward the frame on interface indicated
else floodforward on all but the interface on which the frame arrived
DataLink Layer 12
Self-learning forwarding example A
Arsquo
B
Brsquo
C
Crsquo
1 23
45
6
A Arsquo
Source ADest Arsquo
MAC addr interface TTL
Switch table (initially empty)
A 1 60
A ArsquoA ArsquoA ArsquoA ArsquoA Arsquo
frame destination unknown flood
Arsquo A
destination A location known
Arsquo 4 60
selective send
DataLink Layer 13
Interconnecting switches
switches can be connected together
A
B
Q sending from A to G - how does S1 know to forward frame destined to F via S4 and S3
A self learning (works exactly the same as in single-switch case)
S1
C D
E
FS2
S4
S3
H
I
G
DataLink Layer 14
Switches vs Routers both store-and-forward devices
routers network layer devices (examine network layer headers)
switches are link layer devices
routers maintain routing tables implement routing algorithms
switches maintain switch tables implement filtering learning algorithms
DataLink Layer 15
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 16
Point to Point Data Link Control one sender one receiver one link easier than
broadcast link no Media Access Control no need for explicit MAC addressing eg dialup link ISDN line
popular point-to-point DLC protocols PPP (point-to-point protocol) HDLC High level data link control (Data link
used to be considered ldquohigh layerrdquo in protocol stack)
DataLink Layer 17
PPP Design Requirements [RFC 1557] packet framing encapsulation of network-layer
datagram in data link frame carry network layer data of any network layer
protocol (not just IP) at same time ability to demultiplex upwards
bit transparency must carry any bit pattern in the data field
error detection (no correction)
connection liveness detect signal link failure to network layer
network layer address negotiation endpoint can learnconfigure each otherrsquos network address
DataLink Layer 18
PPP non-requirements
no error correctionrecovery
no flow control
out of order delivery OK
no need to support multipoint links (eg polling)
Error recovery flow control data re-ordering all relegated to higher layers
DataLink Layer 19
PPP Data Frame Flag delimiter (framing)
Address does nothing (only one option)
Control does nothing in the future possible multiple control fields
Protocol upper layer protocol to which frame delivered (eg IP PPP-LCP IPCP etc)
info upper layer data being carried
check cyclic redundancy check for error detection
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 2
Ethernet bus topology popular through mid 90s
all nodes in same collision domain (can collide with each other)
today star topology prevails active switch in center each ldquospokerdquo runs a (separate) Ethernet protocol (nodes
do not collide with each other)
bus coaxial cable
switch
star
DataLink Layer 3
Ethernet Frame Structure
Sending adapter encapsulates IP datagram (or other network layer protocol packet) in Ethernet frame
Preamble 7 bytes with pattern 10101010 followed by one
byte with pattern 10101011 used to synchronize receiver sender clock
rates
DataLink Layer 4
Ethernet Frame Structure (more) Addresses 6 bytes
if adapter receives frame with matching destination address or with broadcast address (eg ARP packet) it passes data in frame to network layer protocol
otherwise adapter discards frame
Type indicates higher layer protocol (mostly IP but others possible eg Novell IPX AppleTalk)
CRC checked at receiver if error is detected frame is dropped
DataLink Layer 5
Ethernet CSMACD algorithm1 NIC receives datagram from network layer creates
frame
2 If NIC senses channel idle starts frame transmission If NIC senses channel busy waits until channel idle then transmits
3 If NIC transmits entire frame without detecting another transmission NIC is done with frame
4 If NIC detects another transmission while transmitting aborts and sends jam signal
5 After aborting NIC enters exponential backoff after mth collision NIC chooses K at random from 012hellip2m-1 NIC waits K512 bit times returns to Step 2
DataLink Layer 6
CSMACD efficiency Tprop = max prop delay between 2 nodes in LAN
ttrans = time to transmit max-size frame
efficiency goes to 1 as tprop goes to 0
as ttrans goes to infinity
better performance than ALOHA and simple cheap decentralized
transprop ttefficiency
51
1
DataLink Layer 7
8023 Ethernet Standards Link amp Physical Layers
many different Ethernet standards common MAC protocol and frame format
different speeds 2 Mbps 10 Mbps 100 Mbps 1Gbps 10G bps
different physical layer media fiber cable
application
transport
network
link
physical
MAC protocoland frame format
100BASE-TX
100BASE-T4
100BASE-FX100BASE-T2
100BASE-SX 100BASE-BX
fiber physical layercopper (twisterpair) physical layer
DataLink Layer 8
Hubshellip physical-layer (ldquodumbrdquo) repeaters
bits coming in one link go out all other links at same rate all nodes connected to hub can collide with one another no frame buffering no CSMACD at hub host NICs detect collisions
twisted pair
hub
DataLink Layer 9
Switch link-layer device smarter than hubs take active
role store forward Ethernet frames examine incoming framersquos MAC address selectively
forward frame to one-or-more outgoing links when frame is to be forwarded on segment uses CSMACD to access segment
transparent hosts are unaware of presence of switches
plug-and-play self-learning switches do not need to be configured
DataLink Layer 10
Switch allows multiple simultaneous transmissions
hosts have dedicated direct connection to switch
switches buffer packets Ethernet protocol used on
each incoming link but no collisions full duplex each link is its own collision
domain
switching A-to-Arsquo and B-to-Brsquo simultaneously without collisions not possible with dumb hub
A
Arsquo
B
Brsquo
C
Crsquo
switch with six interfaces(123456)
1 23
45
6
DataLink Layer 11
Switch frame filteringforwardingWhen frame received
1 record link associated with sending host
2 index switch table using MAC dest address
3 if entry found for destination then
if dest on segment from which frame arrived then drop the frame
else forward the frame on interface indicated
else floodforward on all but the interface on which the frame arrived
DataLink Layer 12
Self-learning forwarding example A
Arsquo
B
Brsquo
C
Crsquo
1 23
45
6
A Arsquo
Source ADest Arsquo
MAC addr interface TTL
Switch table (initially empty)
A 1 60
A ArsquoA ArsquoA ArsquoA ArsquoA Arsquo
frame destination unknown flood
Arsquo A
destination A location known
Arsquo 4 60
selective send
DataLink Layer 13
Interconnecting switches
switches can be connected together
A
B
Q sending from A to G - how does S1 know to forward frame destined to F via S4 and S3
A self learning (works exactly the same as in single-switch case)
S1
C D
E
FS2
S4
S3
H
I
G
DataLink Layer 14
Switches vs Routers both store-and-forward devices
routers network layer devices (examine network layer headers)
switches are link layer devices
routers maintain routing tables implement routing algorithms
switches maintain switch tables implement filtering learning algorithms
DataLink Layer 15
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 16
Point to Point Data Link Control one sender one receiver one link easier than
broadcast link no Media Access Control no need for explicit MAC addressing eg dialup link ISDN line
popular point-to-point DLC protocols PPP (point-to-point protocol) HDLC High level data link control (Data link
used to be considered ldquohigh layerrdquo in protocol stack)
DataLink Layer 17
PPP Design Requirements [RFC 1557] packet framing encapsulation of network-layer
datagram in data link frame carry network layer data of any network layer
protocol (not just IP) at same time ability to demultiplex upwards
bit transparency must carry any bit pattern in the data field
error detection (no correction)
connection liveness detect signal link failure to network layer
network layer address negotiation endpoint can learnconfigure each otherrsquos network address
DataLink Layer 18
PPP non-requirements
no error correctionrecovery
no flow control
out of order delivery OK
no need to support multipoint links (eg polling)
Error recovery flow control data re-ordering all relegated to higher layers
DataLink Layer 19
PPP Data Frame Flag delimiter (framing)
Address does nothing (only one option)
Control does nothing in the future possible multiple control fields
Protocol upper layer protocol to which frame delivered (eg IP PPP-LCP IPCP etc)
info upper layer data being carried
check cyclic redundancy check for error detection
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 3
Ethernet Frame Structure
Sending adapter encapsulates IP datagram (or other network layer protocol packet) in Ethernet frame
Preamble 7 bytes with pattern 10101010 followed by one
byte with pattern 10101011 used to synchronize receiver sender clock
rates
DataLink Layer 4
Ethernet Frame Structure (more) Addresses 6 bytes
if adapter receives frame with matching destination address or with broadcast address (eg ARP packet) it passes data in frame to network layer protocol
otherwise adapter discards frame
Type indicates higher layer protocol (mostly IP but others possible eg Novell IPX AppleTalk)
CRC checked at receiver if error is detected frame is dropped
DataLink Layer 5
Ethernet CSMACD algorithm1 NIC receives datagram from network layer creates
frame
2 If NIC senses channel idle starts frame transmission If NIC senses channel busy waits until channel idle then transmits
3 If NIC transmits entire frame without detecting another transmission NIC is done with frame
4 If NIC detects another transmission while transmitting aborts and sends jam signal
5 After aborting NIC enters exponential backoff after mth collision NIC chooses K at random from 012hellip2m-1 NIC waits K512 bit times returns to Step 2
DataLink Layer 6
CSMACD efficiency Tprop = max prop delay between 2 nodes in LAN
ttrans = time to transmit max-size frame
efficiency goes to 1 as tprop goes to 0
as ttrans goes to infinity
better performance than ALOHA and simple cheap decentralized
transprop ttefficiency
51
1
DataLink Layer 7
8023 Ethernet Standards Link amp Physical Layers
many different Ethernet standards common MAC protocol and frame format
different speeds 2 Mbps 10 Mbps 100 Mbps 1Gbps 10G bps
different physical layer media fiber cable
application
transport
network
link
physical
MAC protocoland frame format
100BASE-TX
100BASE-T4
100BASE-FX100BASE-T2
100BASE-SX 100BASE-BX
fiber physical layercopper (twisterpair) physical layer
DataLink Layer 8
Hubshellip physical-layer (ldquodumbrdquo) repeaters
bits coming in one link go out all other links at same rate all nodes connected to hub can collide with one another no frame buffering no CSMACD at hub host NICs detect collisions
twisted pair
hub
DataLink Layer 9
Switch link-layer device smarter than hubs take active
role store forward Ethernet frames examine incoming framersquos MAC address selectively
forward frame to one-or-more outgoing links when frame is to be forwarded on segment uses CSMACD to access segment
transparent hosts are unaware of presence of switches
plug-and-play self-learning switches do not need to be configured
DataLink Layer 10
Switch allows multiple simultaneous transmissions
hosts have dedicated direct connection to switch
switches buffer packets Ethernet protocol used on
each incoming link but no collisions full duplex each link is its own collision
domain
switching A-to-Arsquo and B-to-Brsquo simultaneously without collisions not possible with dumb hub
A
Arsquo
B
Brsquo
C
Crsquo
switch with six interfaces(123456)
1 23
45
6
DataLink Layer 11
Switch frame filteringforwardingWhen frame received
1 record link associated with sending host
2 index switch table using MAC dest address
3 if entry found for destination then
if dest on segment from which frame arrived then drop the frame
else forward the frame on interface indicated
else floodforward on all but the interface on which the frame arrived
DataLink Layer 12
Self-learning forwarding example A
Arsquo
B
Brsquo
C
Crsquo
1 23
45
6
A Arsquo
Source ADest Arsquo
MAC addr interface TTL
Switch table (initially empty)
A 1 60
A ArsquoA ArsquoA ArsquoA ArsquoA Arsquo
frame destination unknown flood
Arsquo A
destination A location known
Arsquo 4 60
selective send
DataLink Layer 13
Interconnecting switches
switches can be connected together
A
B
Q sending from A to G - how does S1 know to forward frame destined to F via S4 and S3
A self learning (works exactly the same as in single-switch case)
S1
C D
E
FS2
S4
S3
H
I
G
DataLink Layer 14
Switches vs Routers both store-and-forward devices
routers network layer devices (examine network layer headers)
switches are link layer devices
routers maintain routing tables implement routing algorithms
switches maintain switch tables implement filtering learning algorithms
DataLink Layer 15
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 16
Point to Point Data Link Control one sender one receiver one link easier than
broadcast link no Media Access Control no need for explicit MAC addressing eg dialup link ISDN line
popular point-to-point DLC protocols PPP (point-to-point protocol) HDLC High level data link control (Data link
used to be considered ldquohigh layerrdquo in protocol stack)
DataLink Layer 17
PPP Design Requirements [RFC 1557] packet framing encapsulation of network-layer
datagram in data link frame carry network layer data of any network layer
protocol (not just IP) at same time ability to demultiplex upwards
bit transparency must carry any bit pattern in the data field
error detection (no correction)
connection liveness detect signal link failure to network layer
network layer address negotiation endpoint can learnconfigure each otherrsquos network address
DataLink Layer 18
PPP non-requirements
no error correctionrecovery
no flow control
out of order delivery OK
no need to support multipoint links (eg polling)
Error recovery flow control data re-ordering all relegated to higher layers
DataLink Layer 19
PPP Data Frame Flag delimiter (framing)
Address does nothing (only one option)
Control does nothing in the future possible multiple control fields
Protocol upper layer protocol to which frame delivered (eg IP PPP-LCP IPCP etc)
info upper layer data being carried
check cyclic redundancy check for error detection
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 4
Ethernet Frame Structure (more) Addresses 6 bytes
if adapter receives frame with matching destination address or with broadcast address (eg ARP packet) it passes data in frame to network layer protocol
otherwise adapter discards frame
Type indicates higher layer protocol (mostly IP but others possible eg Novell IPX AppleTalk)
CRC checked at receiver if error is detected frame is dropped
DataLink Layer 5
Ethernet CSMACD algorithm1 NIC receives datagram from network layer creates
frame
2 If NIC senses channel idle starts frame transmission If NIC senses channel busy waits until channel idle then transmits
3 If NIC transmits entire frame without detecting another transmission NIC is done with frame
4 If NIC detects another transmission while transmitting aborts and sends jam signal
5 After aborting NIC enters exponential backoff after mth collision NIC chooses K at random from 012hellip2m-1 NIC waits K512 bit times returns to Step 2
DataLink Layer 6
CSMACD efficiency Tprop = max prop delay between 2 nodes in LAN
ttrans = time to transmit max-size frame
efficiency goes to 1 as tprop goes to 0
as ttrans goes to infinity
better performance than ALOHA and simple cheap decentralized
transprop ttefficiency
51
1
DataLink Layer 7
8023 Ethernet Standards Link amp Physical Layers
many different Ethernet standards common MAC protocol and frame format
different speeds 2 Mbps 10 Mbps 100 Mbps 1Gbps 10G bps
different physical layer media fiber cable
application
transport
network
link
physical
MAC protocoland frame format
100BASE-TX
100BASE-T4
100BASE-FX100BASE-T2
100BASE-SX 100BASE-BX
fiber physical layercopper (twisterpair) physical layer
DataLink Layer 8
Hubshellip physical-layer (ldquodumbrdquo) repeaters
bits coming in one link go out all other links at same rate all nodes connected to hub can collide with one another no frame buffering no CSMACD at hub host NICs detect collisions
twisted pair
hub
DataLink Layer 9
Switch link-layer device smarter than hubs take active
role store forward Ethernet frames examine incoming framersquos MAC address selectively
forward frame to one-or-more outgoing links when frame is to be forwarded on segment uses CSMACD to access segment
transparent hosts are unaware of presence of switches
plug-and-play self-learning switches do not need to be configured
DataLink Layer 10
Switch allows multiple simultaneous transmissions
hosts have dedicated direct connection to switch
switches buffer packets Ethernet protocol used on
each incoming link but no collisions full duplex each link is its own collision
domain
switching A-to-Arsquo and B-to-Brsquo simultaneously without collisions not possible with dumb hub
A
Arsquo
B
Brsquo
C
Crsquo
switch with six interfaces(123456)
1 23
45
6
DataLink Layer 11
Switch frame filteringforwardingWhen frame received
1 record link associated with sending host
2 index switch table using MAC dest address
3 if entry found for destination then
if dest on segment from which frame arrived then drop the frame
else forward the frame on interface indicated
else floodforward on all but the interface on which the frame arrived
DataLink Layer 12
Self-learning forwarding example A
Arsquo
B
Brsquo
C
Crsquo
1 23
45
6
A Arsquo
Source ADest Arsquo
MAC addr interface TTL
Switch table (initially empty)
A 1 60
A ArsquoA ArsquoA ArsquoA ArsquoA Arsquo
frame destination unknown flood
Arsquo A
destination A location known
Arsquo 4 60
selective send
DataLink Layer 13
Interconnecting switches
switches can be connected together
A
B
Q sending from A to G - how does S1 know to forward frame destined to F via S4 and S3
A self learning (works exactly the same as in single-switch case)
S1
C D
E
FS2
S4
S3
H
I
G
DataLink Layer 14
Switches vs Routers both store-and-forward devices
routers network layer devices (examine network layer headers)
switches are link layer devices
routers maintain routing tables implement routing algorithms
switches maintain switch tables implement filtering learning algorithms
DataLink Layer 15
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 16
Point to Point Data Link Control one sender one receiver one link easier than
broadcast link no Media Access Control no need for explicit MAC addressing eg dialup link ISDN line
popular point-to-point DLC protocols PPP (point-to-point protocol) HDLC High level data link control (Data link
used to be considered ldquohigh layerrdquo in protocol stack)
DataLink Layer 17
PPP Design Requirements [RFC 1557] packet framing encapsulation of network-layer
datagram in data link frame carry network layer data of any network layer
protocol (not just IP) at same time ability to demultiplex upwards
bit transparency must carry any bit pattern in the data field
error detection (no correction)
connection liveness detect signal link failure to network layer
network layer address negotiation endpoint can learnconfigure each otherrsquos network address
DataLink Layer 18
PPP non-requirements
no error correctionrecovery
no flow control
out of order delivery OK
no need to support multipoint links (eg polling)
Error recovery flow control data re-ordering all relegated to higher layers
DataLink Layer 19
PPP Data Frame Flag delimiter (framing)
Address does nothing (only one option)
Control does nothing in the future possible multiple control fields
Protocol upper layer protocol to which frame delivered (eg IP PPP-LCP IPCP etc)
info upper layer data being carried
check cyclic redundancy check for error detection
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 5
Ethernet CSMACD algorithm1 NIC receives datagram from network layer creates
frame
2 If NIC senses channel idle starts frame transmission If NIC senses channel busy waits until channel idle then transmits
3 If NIC transmits entire frame without detecting another transmission NIC is done with frame
4 If NIC detects another transmission while transmitting aborts and sends jam signal
5 After aborting NIC enters exponential backoff after mth collision NIC chooses K at random from 012hellip2m-1 NIC waits K512 bit times returns to Step 2
DataLink Layer 6
CSMACD efficiency Tprop = max prop delay between 2 nodes in LAN
ttrans = time to transmit max-size frame
efficiency goes to 1 as tprop goes to 0
as ttrans goes to infinity
better performance than ALOHA and simple cheap decentralized
transprop ttefficiency
51
1
DataLink Layer 7
8023 Ethernet Standards Link amp Physical Layers
many different Ethernet standards common MAC protocol and frame format
different speeds 2 Mbps 10 Mbps 100 Mbps 1Gbps 10G bps
different physical layer media fiber cable
application
transport
network
link
physical
MAC protocoland frame format
100BASE-TX
100BASE-T4
100BASE-FX100BASE-T2
100BASE-SX 100BASE-BX
fiber physical layercopper (twisterpair) physical layer
DataLink Layer 8
Hubshellip physical-layer (ldquodumbrdquo) repeaters
bits coming in one link go out all other links at same rate all nodes connected to hub can collide with one another no frame buffering no CSMACD at hub host NICs detect collisions
twisted pair
hub
DataLink Layer 9
Switch link-layer device smarter than hubs take active
role store forward Ethernet frames examine incoming framersquos MAC address selectively
forward frame to one-or-more outgoing links when frame is to be forwarded on segment uses CSMACD to access segment
transparent hosts are unaware of presence of switches
plug-and-play self-learning switches do not need to be configured
DataLink Layer 10
Switch allows multiple simultaneous transmissions
hosts have dedicated direct connection to switch
switches buffer packets Ethernet protocol used on
each incoming link but no collisions full duplex each link is its own collision
domain
switching A-to-Arsquo and B-to-Brsquo simultaneously without collisions not possible with dumb hub
A
Arsquo
B
Brsquo
C
Crsquo
switch with six interfaces(123456)
1 23
45
6
DataLink Layer 11
Switch frame filteringforwardingWhen frame received
1 record link associated with sending host
2 index switch table using MAC dest address
3 if entry found for destination then
if dest on segment from which frame arrived then drop the frame
else forward the frame on interface indicated
else floodforward on all but the interface on which the frame arrived
DataLink Layer 12
Self-learning forwarding example A
Arsquo
B
Brsquo
C
Crsquo
1 23
45
6
A Arsquo
Source ADest Arsquo
MAC addr interface TTL
Switch table (initially empty)
A 1 60
A ArsquoA ArsquoA ArsquoA ArsquoA Arsquo
frame destination unknown flood
Arsquo A
destination A location known
Arsquo 4 60
selective send
DataLink Layer 13
Interconnecting switches
switches can be connected together
A
B
Q sending from A to G - how does S1 know to forward frame destined to F via S4 and S3
A self learning (works exactly the same as in single-switch case)
S1
C D
E
FS2
S4
S3
H
I
G
DataLink Layer 14
Switches vs Routers both store-and-forward devices
routers network layer devices (examine network layer headers)
switches are link layer devices
routers maintain routing tables implement routing algorithms
switches maintain switch tables implement filtering learning algorithms
DataLink Layer 15
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 16
Point to Point Data Link Control one sender one receiver one link easier than
broadcast link no Media Access Control no need for explicit MAC addressing eg dialup link ISDN line
popular point-to-point DLC protocols PPP (point-to-point protocol) HDLC High level data link control (Data link
used to be considered ldquohigh layerrdquo in protocol stack)
DataLink Layer 17
PPP Design Requirements [RFC 1557] packet framing encapsulation of network-layer
datagram in data link frame carry network layer data of any network layer
protocol (not just IP) at same time ability to demultiplex upwards
bit transparency must carry any bit pattern in the data field
error detection (no correction)
connection liveness detect signal link failure to network layer
network layer address negotiation endpoint can learnconfigure each otherrsquos network address
DataLink Layer 18
PPP non-requirements
no error correctionrecovery
no flow control
out of order delivery OK
no need to support multipoint links (eg polling)
Error recovery flow control data re-ordering all relegated to higher layers
DataLink Layer 19
PPP Data Frame Flag delimiter (framing)
Address does nothing (only one option)
Control does nothing in the future possible multiple control fields
Protocol upper layer protocol to which frame delivered (eg IP PPP-LCP IPCP etc)
info upper layer data being carried
check cyclic redundancy check for error detection
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 6
CSMACD efficiency Tprop = max prop delay between 2 nodes in LAN
ttrans = time to transmit max-size frame
efficiency goes to 1 as tprop goes to 0
as ttrans goes to infinity
better performance than ALOHA and simple cheap decentralized
transprop ttefficiency
51
1
DataLink Layer 7
8023 Ethernet Standards Link amp Physical Layers
many different Ethernet standards common MAC protocol and frame format
different speeds 2 Mbps 10 Mbps 100 Mbps 1Gbps 10G bps
different physical layer media fiber cable
application
transport
network
link
physical
MAC protocoland frame format
100BASE-TX
100BASE-T4
100BASE-FX100BASE-T2
100BASE-SX 100BASE-BX
fiber physical layercopper (twisterpair) physical layer
DataLink Layer 8
Hubshellip physical-layer (ldquodumbrdquo) repeaters
bits coming in one link go out all other links at same rate all nodes connected to hub can collide with one another no frame buffering no CSMACD at hub host NICs detect collisions
twisted pair
hub
DataLink Layer 9
Switch link-layer device smarter than hubs take active
role store forward Ethernet frames examine incoming framersquos MAC address selectively
forward frame to one-or-more outgoing links when frame is to be forwarded on segment uses CSMACD to access segment
transparent hosts are unaware of presence of switches
plug-and-play self-learning switches do not need to be configured
DataLink Layer 10
Switch allows multiple simultaneous transmissions
hosts have dedicated direct connection to switch
switches buffer packets Ethernet protocol used on
each incoming link but no collisions full duplex each link is its own collision
domain
switching A-to-Arsquo and B-to-Brsquo simultaneously without collisions not possible with dumb hub
A
Arsquo
B
Brsquo
C
Crsquo
switch with six interfaces(123456)
1 23
45
6
DataLink Layer 11
Switch frame filteringforwardingWhen frame received
1 record link associated with sending host
2 index switch table using MAC dest address
3 if entry found for destination then
if dest on segment from which frame arrived then drop the frame
else forward the frame on interface indicated
else floodforward on all but the interface on which the frame arrived
DataLink Layer 12
Self-learning forwarding example A
Arsquo
B
Brsquo
C
Crsquo
1 23
45
6
A Arsquo
Source ADest Arsquo
MAC addr interface TTL
Switch table (initially empty)
A 1 60
A ArsquoA ArsquoA ArsquoA ArsquoA Arsquo
frame destination unknown flood
Arsquo A
destination A location known
Arsquo 4 60
selective send
DataLink Layer 13
Interconnecting switches
switches can be connected together
A
B
Q sending from A to G - how does S1 know to forward frame destined to F via S4 and S3
A self learning (works exactly the same as in single-switch case)
S1
C D
E
FS2
S4
S3
H
I
G
DataLink Layer 14
Switches vs Routers both store-and-forward devices
routers network layer devices (examine network layer headers)
switches are link layer devices
routers maintain routing tables implement routing algorithms
switches maintain switch tables implement filtering learning algorithms
DataLink Layer 15
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 16
Point to Point Data Link Control one sender one receiver one link easier than
broadcast link no Media Access Control no need for explicit MAC addressing eg dialup link ISDN line
popular point-to-point DLC protocols PPP (point-to-point protocol) HDLC High level data link control (Data link
used to be considered ldquohigh layerrdquo in protocol stack)
DataLink Layer 17
PPP Design Requirements [RFC 1557] packet framing encapsulation of network-layer
datagram in data link frame carry network layer data of any network layer
protocol (not just IP) at same time ability to demultiplex upwards
bit transparency must carry any bit pattern in the data field
error detection (no correction)
connection liveness detect signal link failure to network layer
network layer address negotiation endpoint can learnconfigure each otherrsquos network address
DataLink Layer 18
PPP non-requirements
no error correctionrecovery
no flow control
out of order delivery OK
no need to support multipoint links (eg polling)
Error recovery flow control data re-ordering all relegated to higher layers
DataLink Layer 19
PPP Data Frame Flag delimiter (framing)
Address does nothing (only one option)
Control does nothing in the future possible multiple control fields
Protocol upper layer protocol to which frame delivered (eg IP PPP-LCP IPCP etc)
info upper layer data being carried
check cyclic redundancy check for error detection
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 7
8023 Ethernet Standards Link amp Physical Layers
many different Ethernet standards common MAC protocol and frame format
different speeds 2 Mbps 10 Mbps 100 Mbps 1Gbps 10G bps
different physical layer media fiber cable
application
transport
network
link
physical
MAC protocoland frame format
100BASE-TX
100BASE-T4
100BASE-FX100BASE-T2
100BASE-SX 100BASE-BX
fiber physical layercopper (twisterpair) physical layer
DataLink Layer 8
Hubshellip physical-layer (ldquodumbrdquo) repeaters
bits coming in one link go out all other links at same rate all nodes connected to hub can collide with one another no frame buffering no CSMACD at hub host NICs detect collisions
twisted pair
hub
DataLink Layer 9
Switch link-layer device smarter than hubs take active
role store forward Ethernet frames examine incoming framersquos MAC address selectively
forward frame to one-or-more outgoing links when frame is to be forwarded on segment uses CSMACD to access segment
transparent hosts are unaware of presence of switches
plug-and-play self-learning switches do not need to be configured
DataLink Layer 10
Switch allows multiple simultaneous transmissions
hosts have dedicated direct connection to switch
switches buffer packets Ethernet protocol used on
each incoming link but no collisions full duplex each link is its own collision
domain
switching A-to-Arsquo and B-to-Brsquo simultaneously without collisions not possible with dumb hub
A
Arsquo
B
Brsquo
C
Crsquo
switch with six interfaces(123456)
1 23
45
6
DataLink Layer 11
Switch frame filteringforwardingWhen frame received
1 record link associated with sending host
2 index switch table using MAC dest address
3 if entry found for destination then
if dest on segment from which frame arrived then drop the frame
else forward the frame on interface indicated
else floodforward on all but the interface on which the frame arrived
DataLink Layer 12
Self-learning forwarding example A
Arsquo
B
Brsquo
C
Crsquo
1 23
45
6
A Arsquo
Source ADest Arsquo
MAC addr interface TTL
Switch table (initially empty)
A 1 60
A ArsquoA ArsquoA ArsquoA ArsquoA Arsquo
frame destination unknown flood
Arsquo A
destination A location known
Arsquo 4 60
selective send
DataLink Layer 13
Interconnecting switches
switches can be connected together
A
B
Q sending from A to G - how does S1 know to forward frame destined to F via S4 and S3
A self learning (works exactly the same as in single-switch case)
S1
C D
E
FS2
S4
S3
H
I
G
DataLink Layer 14
Switches vs Routers both store-and-forward devices
routers network layer devices (examine network layer headers)
switches are link layer devices
routers maintain routing tables implement routing algorithms
switches maintain switch tables implement filtering learning algorithms
DataLink Layer 15
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 16
Point to Point Data Link Control one sender one receiver one link easier than
broadcast link no Media Access Control no need for explicit MAC addressing eg dialup link ISDN line
popular point-to-point DLC protocols PPP (point-to-point protocol) HDLC High level data link control (Data link
used to be considered ldquohigh layerrdquo in protocol stack)
DataLink Layer 17
PPP Design Requirements [RFC 1557] packet framing encapsulation of network-layer
datagram in data link frame carry network layer data of any network layer
protocol (not just IP) at same time ability to demultiplex upwards
bit transparency must carry any bit pattern in the data field
error detection (no correction)
connection liveness detect signal link failure to network layer
network layer address negotiation endpoint can learnconfigure each otherrsquos network address
DataLink Layer 18
PPP non-requirements
no error correctionrecovery
no flow control
out of order delivery OK
no need to support multipoint links (eg polling)
Error recovery flow control data re-ordering all relegated to higher layers
DataLink Layer 19
PPP Data Frame Flag delimiter (framing)
Address does nothing (only one option)
Control does nothing in the future possible multiple control fields
Protocol upper layer protocol to which frame delivered (eg IP PPP-LCP IPCP etc)
info upper layer data being carried
check cyclic redundancy check for error detection
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 8
Hubshellip physical-layer (ldquodumbrdquo) repeaters
bits coming in one link go out all other links at same rate all nodes connected to hub can collide with one another no frame buffering no CSMACD at hub host NICs detect collisions
twisted pair
hub
DataLink Layer 9
Switch link-layer device smarter than hubs take active
role store forward Ethernet frames examine incoming framersquos MAC address selectively
forward frame to one-or-more outgoing links when frame is to be forwarded on segment uses CSMACD to access segment
transparent hosts are unaware of presence of switches
plug-and-play self-learning switches do not need to be configured
DataLink Layer 10
Switch allows multiple simultaneous transmissions
hosts have dedicated direct connection to switch
switches buffer packets Ethernet protocol used on
each incoming link but no collisions full duplex each link is its own collision
domain
switching A-to-Arsquo and B-to-Brsquo simultaneously without collisions not possible with dumb hub
A
Arsquo
B
Brsquo
C
Crsquo
switch with six interfaces(123456)
1 23
45
6
DataLink Layer 11
Switch frame filteringforwardingWhen frame received
1 record link associated with sending host
2 index switch table using MAC dest address
3 if entry found for destination then
if dest on segment from which frame arrived then drop the frame
else forward the frame on interface indicated
else floodforward on all but the interface on which the frame arrived
DataLink Layer 12
Self-learning forwarding example A
Arsquo
B
Brsquo
C
Crsquo
1 23
45
6
A Arsquo
Source ADest Arsquo
MAC addr interface TTL
Switch table (initially empty)
A 1 60
A ArsquoA ArsquoA ArsquoA ArsquoA Arsquo
frame destination unknown flood
Arsquo A
destination A location known
Arsquo 4 60
selective send
DataLink Layer 13
Interconnecting switches
switches can be connected together
A
B
Q sending from A to G - how does S1 know to forward frame destined to F via S4 and S3
A self learning (works exactly the same as in single-switch case)
S1
C D
E
FS2
S4
S3
H
I
G
DataLink Layer 14
Switches vs Routers both store-and-forward devices
routers network layer devices (examine network layer headers)
switches are link layer devices
routers maintain routing tables implement routing algorithms
switches maintain switch tables implement filtering learning algorithms
DataLink Layer 15
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 16
Point to Point Data Link Control one sender one receiver one link easier than
broadcast link no Media Access Control no need for explicit MAC addressing eg dialup link ISDN line
popular point-to-point DLC protocols PPP (point-to-point protocol) HDLC High level data link control (Data link
used to be considered ldquohigh layerrdquo in protocol stack)
DataLink Layer 17
PPP Design Requirements [RFC 1557] packet framing encapsulation of network-layer
datagram in data link frame carry network layer data of any network layer
protocol (not just IP) at same time ability to demultiplex upwards
bit transparency must carry any bit pattern in the data field
error detection (no correction)
connection liveness detect signal link failure to network layer
network layer address negotiation endpoint can learnconfigure each otherrsquos network address
DataLink Layer 18
PPP non-requirements
no error correctionrecovery
no flow control
out of order delivery OK
no need to support multipoint links (eg polling)
Error recovery flow control data re-ordering all relegated to higher layers
DataLink Layer 19
PPP Data Frame Flag delimiter (framing)
Address does nothing (only one option)
Control does nothing in the future possible multiple control fields
Protocol upper layer protocol to which frame delivered (eg IP PPP-LCP IPCP etc)
info upper layer data being carried
check cyclic redundancy check for error detection
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 9
Switch link-layer device smarter than hubs take active
role store forward Ethernet frames examine incoming framersquos MAC address selectively
forward frame to one-or-more outgoing links when frame is to be forwarded on segment uses CSMACD to access segment
transparent hosts are unaware of presence of switches
plug-and-play self-learning switches do not need to be configured
DataLink Layer 10
Switch allows multiple simultaneous transmissions
hosts have dedicated direct connection to switch
switches buffer packets Ethernet protocol used on
each incoming link but no collisions full duplex each link is its own collision
domain
switching A-to-Arsquo and B-to-Brsquo simultaneously without collisions not possible with dumb hub
A
Arsquo
B
Brsquo
C
Crsquo
switch with six interfaces(123456)
1 23
45
6
DataLink Layer 11
Switch frame filteringforwardingWhen frame received
1 record link associated with sending host
2 index switch table using MAC dest address
3 if entry found for destination then
if dest on segment from which frame arrived then drop the frame
else forward the frame on interface indicated
else floodforward on all but the interface on which the frame arrived
DataLink Layer 12
Self-learning forwarding example A
Arsquo
B
Brsquo
C
Crsquo
1 23
45
6
A Arsquo
Source ADest Arsquo
MAC addr interface TTL
Switch table (initially empty)
A 1 60
A ArsquoA ArsquoA ArsquoA ArsquoA Arsquo
frame destination unknown flood
Arsquo A
destination A location known
Arsquo 4 60
selective send
DataLink Layer 13
Interconnecting switches
switches can be connected together
A
B
Q sending from A to G - how does S1 know to forward frame destined to F via S4 and S3
A self learning (works exactly the same as in single-switch case)
S1
C D
E
FS2
S4
S3
H
I
G
DataLink Layer 14
Switches vs Routers both store-and-forward devices
routers network layer devices (examine network layer headers)
switches are link layer devices
routers maintain routing tables implement routing algorithms
switches maintain switch tables implement filtering learning algorithms
DataLink Layer 15
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 16
Point to Point Data Link Control one sender one receiver one link easier than
broadcast link no Media Access Control no need for explicit MAC addressing eg dialup link ISDN line
popular point-to-point DLC protocols PPP (point-to-point protocol) HDLC High level data link control (Data link
used to be considered ldquohigh layerrdquo in protocol stack)
DataLink Layer 17
PPP Design Requirements [RFC 1557] packet framing encapsulation of network-layer
datagram in data link frame carry network layer data of any network layer
protocol (not just IP) at same time ability to demultiplex upwards
bit transparency must carry any bit pattern in the data field
error detection (no correction)
connection liveness detect signal link failure to network layer
network layer address negotiation endpoint can learnconfigure each otherrsquos network address
DataLink Layer 18
PPP non-requirements
no error correctionrecovery
no flow control
out of order delivery OK
no need to support multipoint links (eg polling)
Error recovery flow control data re-ordering all relegated to higher layers
DataLink Layer 19
PPP Data Frame Flag delimiter (framing)
Address does nothing (only one option)
Control does nothing in the future possible multiple control fields
Protocol upper layer protocol to which frame delivered (eg IP PPP-LCP IPCP etc)
info upper layer data being carried
check cyclic redundancy check for error detection
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 10
Switch allows multiple simultaneous transmissions
hosts have dedicated direct connection to switch
switches buffer packets Ethernet protocol used on
each incoming link but no collisions full duplex each link is its own collision
domain
switching A-to-Arsquo and B-to-Brsquo simultaneously without collisions not possible with dumb hub
A
Arsquo
B
Brsquo
C
Crsquo
switch with six interfaces(123456)
1 23
45
6
DataLink Layer 11
Switch frame filteringforwardingWhen frame received
1 record link associated with sending host
2 index switch table using MAC dest address
3 if entry found for destination then
if dest on segment from which frame arrived then drop the frame
else forward the frame on interface indicated
else floodforward on all but the interface on which the frame arrived
DataLink Layer 12
Self-learning forwarding example A
Arsquo
B
Brsquo
C
Crsquo
1 23
45
6
A Arsquo
Source ADest Arsquo
MAC addr interface TTL
Switch table (initially empty)
A 1 60
A ArsquoA ArsquoA ArsquoA ArsquoA Arsquo
frame destination unknown flood
Arsquo A
destination A location known
Arsquo 4 60
selective send
DataLink Layer 13
Interconnecting switches
switches can be connected together
A
B
Q sending from A to G - how does S1 know to forward frame destined to F via S4 and S3
A self learning (works exactly the same as in single-switch case)
S1
C D
E
FS2
S4
S3
H
I
G
DataLink Layer 14
Switches vs Routers both store-and-forward devices
routers network layer devices (examine network layer headers)
switches are link layer devices
routers maintain routing tables implement routing algorithms
switches maintain switch tables implement filtering learning algorithms
DataLink Layer 15
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 16
Point to Point Data Link Control one sender one receiver one link easier than
broadcast link no Media Access Control no need for explicit MAC addressing eg dialup link ISDN line
popular point-to-point DLC protocols PPP (point-to-point protocol) HDLC High level data link control (Data link
used to be considered ldquohigh layerrdquo in protocol stack)
DataLink Layer 17
PPP Design Requirements [RFC 1557] packet framing encapsulation of network-layer
datagram in data link frame carry network layer data of any network layer
protocol (not just IP) at same time ability to demultiplex upwards
bit transparency must carry any bit pattern in the data field
error detection (no correction)
connection liveness detect signal link failure to network layer
network layer address negotiation endpoint can learnconfigure each otherrsquos network address
DataLink Layer 18
PPP non-requirements
no error correctionrecovery
no flow control
out of order delivery OK
no need to support multipoint links (eg polling)
Error recovery flow control data re-ordering all relegated to higher layers
DataLink Layer 19
PPP Data Frame Flag delimiter (framing)
Address does nothing (only one option)
Control does nothing in the future possible multiple control fields
Protocol upper layer protocol to which frame delivered (eg IP PPP-LCP IPCP etc)
info upper layer data being carried
check cyclic redundancy check for error detection
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 11
Switch frame filteringforwardingWhen frame received
1 record link associated with sending host
2 index switch table using MAC dest address
3 if entry found for destination then
if dest on segment from which frame arrived then drop the frame
else forward the frame on interface indicated
else floodforward on all but the interface on which the frame arrived
DataLink Layer 12
Self-learning forwarding example A
Arsquo
B
Brsquo
C
Crsquo
1 23
45
6
A Arsquo
Source ADest Arsquo
MAC addr interface TTL
Switch table (initially empty)
A 1 60
A ArsquoA ArsquoA ArsquoA ArsquoA Arsquo
frame destination unknown flood
Arsquo A
destination A location known
Arsquo 4 60
selective send
DataLink Layer 13
Interconnecting switches
switches can be connected together
A
B
Q sending from A to G - how does S1 know to forward frame destined to F via S4 and S3
A self learning (works exactly the same as in single-switch case)
S1
C D
E
FS2
S4
S3
H
I
G
DataLink Layer 14
Switches vs Routers both store-and-forward devices
routers network layer devices (examine network layer headers)
switches are link layer devices
routers maintain routing tables implement routing algorithms
switches maintain switch tables implement filtering learning algorithms
DataLink Layer 15
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 16
Point to Point Data Link Control one sender one receiver one link easier than
broadcast link no Media Access Control no need for explicit MAC addressing eg dialup link ISDN line
popular point-to-point DLC protocols PPP (point-to-point protocol) HDLC High level data link control (Data link
used to be considered ldquohigh layerrdquo in protocol stack)
DataLink Layer 17
PPP Design Requirements [RFC 1557] packet framing encapsulation of network-layer
datagram in data link frame carry network layer data of any network layer
protocol (not just IP) at same time ability to demultiplex upwards
bit transparency must carry any bit pattern in the data field
error detection (no correction)
connection liveness detect signal link failure to network layer
network layer address negotiation endpoint can learnconfigure each otherrsquos network address
DataLink Layer 18
PPP non-requirements
no error correctionrecovery
no flow control
out of order delivery OK
no need to support multipoint links (eg polling)
Error recovery flow control data re-ordering all relegated to higher layers
DataLink Layer 19
PPP Data Frame Flag delimiter (framing)
Address does nothing (only one option)
Control does nothing in the future possible multiple control fields
Protocol upper layer protocol to which frame delivered (eg IP PPP-LCP IPCP etc)
info upper layer data being carried
check cyclic redundancy check for error detection
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 12
Self-learning forwarding example A
Arsquo
B
Brsquo
C
Crsquo
1 23
45
6
A Arsquo
Source ADest Arsquo
MAC addr interface TTL
Switch table (initially empty)
A 1 60
A ArsquoA ArsquoA ArsquoA ArsquoA Arsquo
frame destination unknown flood
Arsquo A
destination A location known
Arsquo 4 60
selective send
DataLink Layer 13
Interconnecting switches
switches can be connected together
A
B
Q sending from A to G - how does S1 know to forward frame destined to F via S4 and S3
A self learning (works exactly the same as in single-switch case)
S1
C D
E
FS2
S4
S3
H
I
G
DataLink Layer 14
Switches vs Routers both store-and-forward devices
routers network layer devices (examine network layer headers)
switches are link layer devices
routers maintain routing tables implement routing algorithms
switches maintain switch tables implement filtering learning algorithms
DataLink Layer 15
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 16
Point to Point Data Link Control one sender one receiver one link easier than
broadcast link no Media Access Control no need for explicit MAC addressing eg dialup link ISDN line
popular point-to-point DLC protocols PPP (point-to-point protocol) HDLC High level data link control (Data link
used to be considered ldquohigh layerrdquo in protocol stack)
DataLink Layer 17
PPP Design Requirements [RFC 1557] packet framing encapsulation of network-layer
datagram in data link frame carry network layer data of any network layer
protocol (not just IP) at same time ability to demultiplex upwards
bit transparency must carry any bit pattern in the data field
error detection (no correction)
connection liveness detect signal link failure to network layer
network layer address negotiation endpoint can learnconfigure each otherrsquos network address
DataLink Layer 18
PPP non-requirements
no error correctionrecovery
no flow control
out of order delivery OK
no need to support multipoint links (eg polling)
Error recovery flow control data re-ordering all relegated to higher layers
DataLink Layer 19
PPP Data Frame Flag delimiter (framing)
Address does nothing (only one option)
Control does nothing in the future possible multiple control fields
Protocol upper layer protocol to which frame delivered (eg IP PPP-LCP IPCP etc)
info upper layer data being carried
check cyclic redundancy check for error detection
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 13
Interconnecting switches
switches can be connected together
A
B
Q sending from A to G - how does S1 know to forward frame destined to F via S4 and S3
A self learning (works exactly the same as in single-switch case)
S1
C D
E
FS2
S4
S3
H
I
G
DataLink Layer 14
Switches vs Routers both store-and-forward devices
routers network layer devices (examine network layer headers)
switches are link layer devices
routers maintain routing tables implement routing algorithms
switches maintain switch tables implement filtering learning algorithms
DataLink Layer 15
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 16
Point to Point Data Link Control one sender one receiver one link easier than
broadcast link no Media Access Control no need for explicit MAC addressing eg dialup link ISDN line
popular point-to-point DLC protocols PPP (point-to-point protocol) HDLC High level data link control (Data link
used to be considered ldquohigh layerrdquo in protocol stack)
DataLink Layer 17
PPP Design Requirements [RFC 1557] packet framing encapsulation of network-layer
datagram in data link frame carry network layer data of any network layer
protocol (not just IP) at same time ability to demultiplex upwards
bit transparency must carry any bit pattern in the data field
error detection (no correction)
connection liveness detect signal link failure to network layer
network layer address negotiation endpoint can learnconfigure each otherrsquos network address
DataLink Layer 18
PPP non-requirements
no error correctionrecovery
no flow control
out of order delivery OK
no need to support multipoint links (eg polling)
Error recovery flow control data re-ordering all relegated to higher layers
DataLink Layer 19
PPP Data Frame Flag delimiter (framing)
Address does nothing (only one option)
Control does nothing in the future possible multiple control fields
Protocol upper layer protocol to which frame delivered (eg IP PPP-LCP IPCP etc)
info upper layer data being carried
check cyclic redundancy check for error detection
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 14
Switches vs Routers both store-and-forward devices
routers network layer devices (examine network layer headers)
switches are link layer devices
routers maintain routing tables implement routing algorithms
switches maintain switch tables implement filtering learning algorithms
DataLink Layer 15
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 16
Point to Point Data Link Control one sender one receiver one link easier than
broadcast link no Media Access Control no need for explicit MAC addressing eg dialup link ISDN line
popular point-to-point DLC protocols PPP (point-to-point protocol) HDLC High level data link control (Data link
used to be considered ldquohigh layerrdquo in protocol stack)
DataLink Layer 17
PPP Design Requirements [RFC 1557] packet framing encapsulation of network-layer
datagram in data link frame carry network layer data of any network layer
protocol (not just IP) at same time ability to demultiplex upwards
bit transparency must carry any bit pattern in the data field
error detection (no correction)
connection liveness detect signal link failure to network layer
network layer address negotiation endpoint can learnconfigure each otherrsquos network address
DataLink Layer 18
PPP non-requirements
no error correctionrecovery
no flow control
out of order delivery OK
no need to support multipoint links (eg polling)
Error recovery flow control data re-ordering all relegated to higher layers
DataLink Layer 19
PPP Data Frame Flag delimiter (framing)
Address does nothing (only one option)
Control does nothing in the future possible multiple control fields
Protocol upper layer protocol to which frame delivered (eg IP PPP-LCP IPCP etc)
info upper layer data being carried
check cyclic redundancy check for error detection
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 15
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 16
Point to Point Data Link Control one sender one receiver one link easier than
broadcast link no Media Access Control no need for explicit MAC addressing eg dialup link ISDN line
popular point-to-point DLC protocols PPP (point-to-point protocol) HDLC High level data link control (Data link
used to be considered ldquohigh layerrdquo in protocol stack)
DataLink Layer 17
PPP Design Requirements [RFC 1557] packet framing encapsulation of network-layer
datagram in data link frame carry network layer data of any network layer
protocol (not just IP) at same time ability to demultiplex upwards
bit transparency must carry any bit pattern in the data field
error detection (no correction)
connection liveness detect signal link failure to network layer
network layer address negotiation endpoint can learnconfigure each otherrsquos network address
DataLink Layer 18
PPP non-requirements
no error correctionrecovery
no flow control
out of order delivery OK
no need to support multipoint links (eg polling)
Error recovery flow control data re-ordering all relegated to higher layers
DataLink Layer 19
PPP Data Frame Flag delimiter (framing)
Address does nothing (only one option)
Control does nothing in the future possible multiple control fields
Protocol upper layer protocol to which frame delivered (eg IP PPP-LCP IPCP etc)
info upper layer data being carried
check cyclic redundancy check for error detection
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 16
Point to Point Data Link Control one sender one receiver one link easier than
broadcast link no Media Access Control no need for explicit MAC addressing eg dialup link ISDN line
popular point-to-point DLC protocols PPP (point-to-point protocol) HDLC High level data link control (Data link
used to be considered ldquohigh layerrdquo in protocol stack)
DataLink Layer 17
PPP Design Requirements [RFC 1557] packet framing encapsulation of network-layer
datagram in data link frame carry network layer data of any network layer
protocol (not just IP) at same time ability to demultiplex upwards
bit transparency must carry any bit pattern in the data field
error detection (no correction)
connection liveness detect signal link failure to network layer
network layer address negotiation endpoint can learnconfigure each otherrsquos network address
DataLink Layer 18
PPP non-requirements
no error correctionrecovery
no flow control
out of order delivery OK
no need to support multipoint links (eg polling)
Error recovery flow control data re-ordering all relegated to higher layers
DataLink Layer 19
PPP Data Frame Flag delimiter (framing)
Address does nothing (only one option)
Control does nothing in the future possible multiple control fields
Protocol upper layer protocol to which frame delivered (eg IP PPP-LCP IPCP etc)
info upper layer data being carried
check cyclic redundancy check for error detection
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 17
PPP Design Requirements [RFC 1557] packet framing encapsulation of network-layer
datagram in data link frame carry network layer data of any network layer
protocol (not just IP) at same time ability to demultiplex upwards
bit transparency must carry any bit pattern in the data field
error detection (no correction)
connection liveness detect signal link failure to network layer
network layer address negotiation endpoint can learnconfigure each otherrsquos network address
DataLink Layer 18
PPP non-requirements
no error correctionrecovery
no flow control
out of order delivery OK
no need to support multipoint links (eg polling)
Error recovery flow control data re-ordering all relegated to higher layers
DataLink Layer 19
PPP Data Frame Flag delimiter (framing)
Address does nothing (only one option)
Control does nothing in the future possible multiple control fields
Protocol upper layer protocol to which frame delivered (eg IP PPP-LCP IPCP etc)
info upper layer data being carried
check cyclic redundancy check for error detection
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 18
PPP non-requirements
no error correctionrecovery
no flow control
out of order delivery OK
no need to support multipoint links (eg polling)
Error recovery flow control data re-ordering all relegated to higher layers
DataLink Layer 19
PPP Data Frame Flag delimiter (framing)
Address does nothing (only one option)
Control does nothing in the future possible multiple control fields
Protocol upper layer protocol to which frame delivered (eg IP PPP-LCP IPCP etc)
info upper layer data being carried
check cyclic redundancy check for error detection
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 19
PPP Data Frame Flag delimiter (framing)
Address does nothing (only one option)
Control does nothing in the future possible multiple control fields
Protocol upper layer protocol to which frame delivered (eg IP PPP-LCP IPCP etc)
info upper layer data being carried
check cyclic redundancy check for error detection
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 20
Byte Stuffing ldquodata transparencyrdquo requirement data field must
be allowed to include flag pattern lt01111110gt
Q is received lt01111110gt data or flag
Sender adds (ldquostuffsrdquo) special control escape lt01111101gt byte before each lt01111110gt data byte
Receiver 01111101 discard control escape byte continue data reception
Q what if data contains lt01111101gt add extra lt01111101gt byte before each
lt01111101gt data byte
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 21
Byte Stuffing
flag bytepatternin datato send
flag byte pattern plusstuffed byte in transmitted data
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 22
PPP Data Control ProtocolBefore exchanging network-
layer data data link peers must
configure PPP link (max frame length authentication)
learnconfigure network layer information for IP carry IP Control
Protocol (IPCP) msgs (protocol field 8021) to configurelearn IP address
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 23
Lecture 23 Outline
55 Ethernet
56 Link-layer switches
57 Point to Point Protocol
58 Link Virtualization ATM MPLS
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 24
Virtualization of networks
Virtualization of resources powerful abstraction in systems engineering
computing examples virtual memory virtual devices Virtual machines eg java IBM VM os from 1960rsquos70rsquos
layering of abstractions donrsquot sweat the details of the lower layer only deal with lower layers abstractly
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 25
The Internet virtualizing networks
1974 multiple unconnected nets ARPAnet data-over-cable networks packet satellite network (Aloha) packet radio network
hellip differing in addressing conventions packet formats error recovery routing
ARPAnet satellite net
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 26
The Internet virtualizing networks
ARPAnet satellite net
gateway
Internetwork layer (IP) addressing internetwork
appears as single uniform entity despite underlying local network heterogeneity
network of networks
Gateway ldquoembed internetwork
packets in local packet format or extract themrdquo
route (at internetwork level) to next gateway
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 27
Cerf amp Kahnrsquos Internetwork ArchitectureWhat is virtualized two layers of addressing internetwork and local
network new layer (IP) makes everything homogeneous at
internetwork layer underlying local network technology
cable satellite telephone modem today ATM MPLS
hellip ldquoinvisiblerdquo at internetwork layer Looks like a link layer technology to IP
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 28
ATM and MPLS
ATM MPLS separate networks in their own right different service models addressing routing
from Internet
viewed by Internet as logical link connecting IP routers just like dialup link is really part of separate
network (telephone network)
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 29
Asynchronous Transfer Mode ATM 1990rsquos00 standard for high-speed (155Mbps
to 622 Mbps and higher) Broadband Integrated Service Digital Network architecture
Goal integrated end-end transport of carry voice video data meeting timingQoS requirements of voice
video (versus Internet best-effort model) ldquonext generationrdquo telephony technical roots in
telephone world packet-switching (fixed length packets called
ldquocellsrdquo) using virtual circuits
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 30
ATM architecture
adaptation layer only at edge of ATM network data segmentationreassembly roughly analagous to Internet transport layer
ATM layer ldquonetworkrdquo layer cell switching routing
physical layer
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 31
ATM network or link layerVision end-to-end
transport ldquoATM from desktop to desktoprdquo ATM is a network
technology
Reality used to connect IP backbone routers ldquoIP over ATMrdquo ATM as switched link
layer connecting IP routers
ATMnetwork
IPnetwork
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 32
ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ldquoadaptsrdquo upper
layers (IP or native ATM applications) to ATM layer below
AAL present only in end systems not in switches
AAL layer segment (headertrailer fields data) fragmented across multiple ATM cells analogy TCP segment in many IP packets
physical
ATM
AAL
physical
ATM
AAL
physical
ATM
physical
ATM
end system end systemswitch switch
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 33
ATM Adaptation Layer (AAL) [more] Different versions of AAL layers depending on ATM
service class AAL1 for CBR (Constant Bit Rate) services eg circuit
emulation
AAL2 for VBR (Variable Bit Rate) services eg MPEG video
AAL5 for data (eg IP datagrams)
AAL PDU
ATM cell
User data
small payload -gt short cell-creation delay for digitized
voice
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 34
ATM LayerService transport cells across ATM network
analogous to IP network layer
very different services than IP network layer
NetworkArchitecture
Internet
ATM
ATM
ATM
ATM
ServiceModel
best effort
CBR
VBR
ABR
UBR
Bandwidth
none
constantrateguaranteedrateguaranteed minimumnone
Loss
no
yes
yes
no
no
Order
no
yes
yes
yes
yes
Timing
no
yes
yes
no
no
Congestionfeedback
no (inferredvia loss)nocongestionnocongestionyes
no
Guarantees
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 35
ATM Layer Virtual Circuits VC transport cells carried on VC from source to
dest call setup teardown for each call before data can flow each packet carries VC identifier (not destination ID) every switch on source-dest path maintain ldquostaterdquo for
each passing connection linkswitch resources (bandwidth buffers) may be
allocated to VC to get circuit-like perf
Permanent VCs (PVCs) long lasting connections typically ldquopermanentrdquo route between to IP routers
Switched VCs (SVC) dynamically set up on per-call basis
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 36
ATM VCs
Advantages of ATM VC approach
QoS performance guarantee for connection mapped to VC (bandwidth delay delay jitter)
Drawbacks of ATM VC approach
Inefficient support of datagram traffic
one PVC between each sourcedest pair) does not scale (N2 connections needed)
SVC introduces call setup latency processing overhead for short lived connections
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 37
ATM cell header
5-byte ATM cell header
VCI virtual channel ID will change from link to link thru net
PT Payload type (eg RM cell versus data cell)
CLP Cell Loss Priority bit CLP = 1 implies low priority cell can be discarded if
congestion
HEC Header Error Checksum cyclic redundancy check
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 38
ATM Physical Layer Transmission Convergence Sublayer (TCS) adapts
ATM layer above to PMD sublayer below Header checksum generation 8 bits CRC Cell delineation With ldquounstructuredrdquo PMD sublayer transmission of idle
cells when no data cells to send
Physical Medium Dependent depends on physical medium being used SONETSDH (like a container carrying bits) TDM
OC3 = 15552 Mbps OC12 = 62208 Mbps OC48 = 245 Gbps OC192 = 96 Gbps
T1T3 (old telephone hierarchy) 15 Mbps 45 Mbps unstructured just cells (busyidle)
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 39
IP-Over-ATMClassic IP only 3 ldquonetworksrdquo (eg LAN
segments) MAC and IP addresses
IP over ATM replace ldquonetworkrdquo (eg LAN
segment) with ATM network ATM addresses IP
addresses
EthernetLANs
ATMnetwork
EthernetLANs
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 40
IP-Over-ATM
AALATMphyphy
Eth
IP
ATMphy
ATMphy
apptransport
IPAALATMphy
apptransport
IPEthphy
IP datagrams into ATM AAL5
PDUs
IP addresses to ATM addresses
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 41
Datagram Journey in IP-over-ATM Network
at Source Host IP layer maps between IP ATM dest address (using ARP) passes datagram to AAL5 AAL5 encapsulates data segments cells passes to ATM
layer
ATM network moves cell along VC to destination
at Destination Host AAL5 reassembles cells into original datagram if CRC OK datagram is passed to IP
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 42
Multiprotocol label switching (MPLS)
initial goal speed up IP forwarding by using fixed length label (instead of IP address) to do forwarding borrowing ideas from Virtual Circuit (VC) approach
but IP datagram still keeps IP address
PPP or Ethernet header
IP header remainder of link-layer frameMPLS header
label Exp S TTL
20 3 1 5
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 43
MPLS capable routers
aka label-switched router
forwards packets to outgoing interface based only on label value (donrsquot inspect IP address) MPLS forwarding table distinct from IP forwarding tables
signaling protocol needed to set up forwarding RSVP-TE forwarding possible along paths that IP alone would not
allow (eg source-specific routing) use MPLS for traffic engineering
must co-exist with IP-only routers
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 44
R1R2
D
R3R4
R50
1
00
A
R6
in out outlabel label dest interface 6 - A 0
in out outlabel label dest interface10 6 A 1
12 9 D 0
1
in out outlabel label dest interface 8 6 A 0
0
in out outlabel label dest interface 10 A 0
12 D 0 8 A 1
MPLS forwarding tables
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-
DataLink Layer 45
Chapter 5 Summary principles behind data link layer services
error detection correction sharing a broadcast channel multiple access link layer addressing
instantiation and implementation of various link layer technologies Ethernet switched LANS PPP virtualized networks as a link layer ATM MPLS
- Slide 1
- Ethernet
- Ethernet Frame Structure
- Ethernet Frame Structure (more)
- Ethernet CSMACD algorithm
- CSMACD efficiency
- 8023 Ethernet Standards Link amp Physical Layers
- Hubs
- Switch
- Switch allows multiple simultaneous transmissions
- Switch frame filteringforwarding
- Self-learning forwarding example
- Interconnecting switches
- Switches vs Routers
- Lecture 23 Outline
- Point to Point Data Link Control
- PPP Design Requirements [RFC 1557]
- PPP non-requirements
- PPP Data Frame
- Byte Stuffing
- Slide 21
- PPP Data Control Protocol
- Slide 23
- Virtualization of networks
- The Internet virtualizing networks
- Slide 26
- Cerf amp Kahnrsquos Internetwork Architecture
- ATM and MPLS
- Asynchronous Transfer Mode ATM
- ATM architecture
- ATM network or link layer
- ATM Adaptation Layer (AAL)
- ATM Adaptation Layer (AAL) [more]
- ATM Layer
- ATM Layer Virtual Circuits
- ATM VCs
- ATM cell header
- ATM Physical Layer
- IP-Over-ATM
- Slide 40
- Datagram Journey in IP-over-ATM Network
- Multiprotocol label switching (MPLS)
- MPLS capable routers
- MPLS forwarding tables
- Chapter 5 Summary
-