18. may. 2006 1inf-3190: overview connecting networks by relays layer 1: repeater / hub layer 2:...
TRANSCRIPT
18. May. 2006 1 INF-3190: Overview
Connecting Networks by Relays Layer 1: Repeater / Hub Layer 2: Bridge / Switch
Self-learning bridges Spanning-tree algorithm
Source routing bridges Remote bridges
Layer 3: Router / Layer 3 Gateway / Intermediate Systems
Types Circuit switching Message switching Packet switching Virtual circuit switching
Services Connection-oriented
Connection setup QoS negotation Flow control
Connectionless Unreliable connections No flow control
Layer 4 - 5: Gateway / Protocol Converter
1
2
3
4
5
1
2
3
4
5
Physical layer
Data link layer
Network layer
Transport layer
Application layer
Repeater
Bridge
Router
Gateway
End system End systemIntermediatesystem
A
HC
H
B
H
E
H
F
H
D
H
IMP
Host
H 0 B 0H 1 E 0B 0 E 1H 2 B 1H 3 E 2H 4 E 3
A 0 C 0H 0 C 1H 1 A 0A 1 F 0H 2 F 1F 0 H 0
C 0 H 0C 1 H 1F 0 H 2F 1 H 3C 2 F 0
B 0 D 0B 1 D 1E 0 H 0E 1 D 2
A 0 F 0A 1 H 0A 2 C 0A 3 C 1
E 0 D 0B 0 D 1B 1 H 0D 0 B 0
A
B
C
D
E F
IN OUT
Virtual circuit setup
18. May. 2006 2 INF-3190: Overview
Internet Address resolution
ARP Use broadcast to
search for an IP address
ARP and routing RARP
Use broadcast to acquire own IP address
DHCP RARP improvement
H H H H H
@IP: 9.228.50.3@HW: 0xa3e
target
ARP Response
@IP: 9.228.50.3@HW: 0xa3e
@IP: 9.228.50.8@HW: 0xaa
source
H
target
ARP Request
@IP: 9.228.50.8@HW: 0xaa
@IP: 9.228.50.3@HW:
source
H H H H H
@IP: 9.228.50.3@HW: 0xa3e
target
RARP Response
@IP: 9.228.50.3@HW: 0xa3e
@IP: 9.228.50.8@HW: 0xaa
source
@IP: unknown@HW: 0xaa
target
RARP Request
@IP:@HW: 0xaa
@IP:@HW: 0xaa
source
H
18. May. 2006 3 INF-3190: Overview
Internet Routing
Routing tables Direct routing / interior
protocols Indirect routing /
exterior protocols Autonomous systems AS, AS backbone area,
area Router classes
AS boundary routers Backbone routers Area border routers Internal routers
EGP Open Shortest Path First
Link state routing Border Gateway Protocol
Distance path mechanism
Multicast routing Spanning tree
Link state routing Reverse path forwarding
with pruning Core-based tree Reverse path broadcast Truncated reverse path
broadcast
18. May. 2006 4 INF-3190: Overview
Routing Routing
define the route of packets through the network
Routing algorithm Defines on which outgoing
line an incoming packet will be transmitted
Desired properties Correctness Simplicity Robustness Stability Fairness Optimality
Optimality principle Sink trees
Route determination Datagram Virtual circuit
desti-nation
link
A 0B 3C 1D 4
RoutingProcess
Topology, link utilization, etc.information
Fills & Updates
Uses & Looks upData packets
Incominglines
Outgoinglines
ForwardingProcess
Routingtable
Router
Routing table andpacket forwarding
18. May. 2006 5 INF-3190: Overview
Routing Classes of routing
algorithm Non-adaptive
Non-adaptive shortest path routing
Flooding and selective flooding
Adaptive Centralized routing Isolated routing
Backward learning Distributed routing
Distance vector routing Count-to-infinity
problem Split-horizon
Link state routing Definitions of
distance Oscillations (route
flapping)
2
7
2
2
6
1 2
4
3
3
2
A
C (●,-)
D (●,-)
E (●,-)
F (●,-)
H (●,-)
B (2,A)
G (6,A)
A B CD
EF
GH
I J K L
A 0B 12C 25D 40E 14F 23G 18H 17I 21J 9K 24L 29
A243618277
2031200
112233
I2031198
301960
147
229
H2128362422403119221009
K
2820173018
0
15
8 A20 A
IHIIH
12 H10 I
-6 K
K
line
JA8
delay JI10
JH12
JK6
B C
E F
A D61
2
8
5 7
4 3A
Seq.Age
B C D E F
B 4E 5
Seq.AgeA 4C 2
Seq.AgeB 2D 3
Seq.AgeC 3F 7
Seq.AgeA 5C 1
Seq.AgeB 6D 7
F 6 E 1 F 8 E 8
Link S tate Packets:
Link State Routing
Distance VectorRouting
Dijkstra shortest path
18. May. 2006 6 INF-3190: Overview
Internet Internet Protocol Stack
IP Connectionless
datagram server Segmentation /
reassembly Route recording and
source routing IP networks
IPv4 Addressing Network classes Subnetworks
Netmasks to find subnetworks
CIDR Longest match prefix
to find subnetworks IPv4 vs IPv6
Data link andPhysical layer
Networklayer
Transportlayer
Applicationlayer
WANs
ATM
LLC & MAC
physical
LANs
MANs
IP+ ICMP+ ARP
TCP UDP
SMTP
HTTP
FTP
TE
LNET N
FS RTP
10 Network Host14 16
Subnet Host6 10
10000001000010000000011100000010e.g. address
129.8.7.2:11111111111111111111110000000000Subnet mask:
subnet addresswith netmask use either 129.8.4.0/255.255.252.0or 129.8.4.0/22
10000001000010000000010000000000Subnet address:
& &
Internet Protocols
IPv4 address, netmask andsubnet address
18. May. 2006 7 INF-3190: Overview
Transport Protocols & Network Services
Transport layer protocol
ISO Transport layer
protocol depends on the quality of the network layer service
ISO Network types A, B, C
Transport protocol classes 0 – 4
Internet protocols User Datagram
Protocol Transmission Control
Protocol
CLOSED
LISTEN
SYN RCVD SYN SENT
ESTABLISHED
FIN WAIT 1
FIN WAIT 2
CLOSING
TIME WAIT
CLOSE WAIT LAST ACK
Send SYN
Recv SYN ACK
Send ACK
Send FIN
Recv ACK
Recv FIN Send ACK
Timeout
Send FIN
Recv SYN
Send SYN ACK
Recv FINSend ACK
Recv ACK
Timeout
Recv RST
Recv SYN Send SYN ACK
Send FIN
Recv FIN Send ACKRecv FIN ACKSend ACK
Recv ACK
Send SYN
TCP state machine
18. May. 2006 8 INF-3190: Overview
TCP Features
IP fragmentation vs TCP segmentation RTT estimation for timer management Initial sequence number allocation
Reuse of session identifiers High bandwidth or long-lived slow sessions
Limit transmission rate Both needed Flow Control
Receiver capacity Congestion Control
Network capacity
18. May. 2006 9 INF-3190: Overview
Flow Control Approaches
Sliding window / static buffer allocation
Sliding window / no buffer allocation
Credit mechanism
TCP’s flow control Sliding window and
credit mechanism Nagle’s algorithm Silly window problem
Sender Receiver
time time
<req 8 buffers>
<cred=4>
<seq=0, data=m0>
<seq=1, data=m1>
<seq=2, data=m2>
<ack=1, cred=3>
<seq=3, data=m3>
<seq=4, data=m4>
<seq=2, data=m2>
<ack=4, cred=0>
<ack=4, cred=1>
<ack=4, cred=2>
<seq=5, data=m5>
<seq=6, data=m6>
<ack=6, cred=0>
<ack=6, cred=4>
A wants 8 buffers
A has 3 buffers left
A has 2 buffers left
Message lost but A thinks it has 1 left
A has 1 buffer left
A has 0 buffer left, must stop
A times out and retransmits
A still blocked
A may now send next msg.
A has 1 buffer left
A is now blocked again
A still blocked
B grants messages 0-3 only
Message lost
B acknowledges 0 and 1permits 2-4
Everything acknowledgedbut no free buffers
B found a new buffersomewhere
A has 1 buffer left
A is now blocked again
TCP credit mechanism
18. May. 2006 10 INF-3190: Overview
Congestion Control Congestion control
Can worsen without care
Approaches Repair
Packet dropping Max buffer, min
buffer, content related
Choke packets Threshold and
history, several levels
Fair queueing Avoid
Traffic shaping Leaky bucket Token bucket
Reservation
A
B C
D
E F
Smoothed streamPeak rate
Original packet arrival
time
Choke packets
Traffic shaping
18. May. 2006 11 INF-3190: Overview
Congestion Control and Avoidance Congestion control with TCP
Additive increase, multiplicative decrease
Congestion Window Development
Slow start Congestion window threshold Congestion avoidance phase
Decrease Missing ACKs Timeout
Congestion avoidance with RED and ECN
Random Early Detection Drop packets randomly when
IS queues fill up Early Congestion Notification
Mark packets instead of dropping when IS queues fill up
sender receiver
time
40
20
105
80
15
3025
35
75
55
4550
6560
70
Tail drop
RED
ECN
TCP congestion control
Router queues with RED and ECN
18. May. 2006 12 INF-3190: Overview
Quality of Service QoS: Characterizes the well defined, controllable behavior of a
system with regard to quantitatively measurable parameters
Techniques to Fulfill Requirements Delay and jitter
Reservation, Buffering, Scaling Continuity
Real-time packet re-ordering, Loss detection and compensation, Retransmission, Forward error correction, Stream switching
Synchronity Fate-sharing and route-sharing, Time-stamped packets, Multiplexing,
Buffering, Smoothing QoS negotiation
Resource reservation Styles
Sender-oriented Receiver-oriented combined
18. May. 2006 13 INF-3190: Overview
Multimedia Protocols Multimedia
Time-independent media discrete media Time-dependent media continuous media Interdependent media multimedia
Application level framing Applications know their needs, e.g. ordering and loss Application defines data unit size Try to avoid segmentation
Integrated layer processing Process several layers at once Ordering constraints exist
18. May. 2006 14 INF-3190: Overview
Multimedia Protocols RTP/RTCP
Real-time Transport Protocol ALF and ILP
RTP Profiles Sequencing, synchronization,
payload identification, quality feedbackand session information
Multicast, mixers, translators No reliability, no QoS support
Signaling protocols RTSP
Useful for Video-on-Demand, Near Video-on-Demand, live broadcasts
SIP Useful for internet
telephony andconferencing
Application
RTCP RTP
DecodingEncoding
Application
UDP/IP UDP/IP
RTCPRTP
Decoding Encoding
RTSP signalling
SIP signalling
RTP/RTCP interaction