ch04-core network qos
TRANSCRIPT
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Chapter 1: Network QoSInternet todayQoS definition,QoS parameters
Application : Voice, Video and VPNChapter 2: Per-hop QoSPacket classification: ToS, Traffic Classs, DSCP,Policing, Marking, Shaping
Queue managementSchedulingCall Admission Control (CAC)
Content
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Chapter 3: Edge-to-Edge Network ModelsIntegrated Service modelDifferential Service modelEdge-to-edge IP QoSQoS and end-to-end TCP performance
Chapter 4: QoS in Core NetworksQoS in ATM networksQoS in MPLS networks
Chapter 5: QoS in Wireless NetworksQoS in WLANQoS in 3G Cellular networksQoS in Ad-hoc networks
Content
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Chapter 6: Traffic EngineeringM/M/1, M/M/c modelsM/G/1, M/D/1 modelsQueuing networks
Application of queuing theory in Network QoSChapter 7: Computer simulation
TCP performance evaluation
Simulation of QoS in MPLS networksSimulation of QoS in ATM networkQoS evaluation of multimedia traffic in IP networks
Content
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Rudimentary ATM Concepts
Physical layer
Signaling
Cell formatConnection types
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ATM Building Blocks
ATM signalingUNI and NNI
Virtual connectionsVCC, VP, and VC
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ATM Signaling
UNI = User-to-Network InterfaceNNI = Network-to-Network InterfaceCell header content varies dependingon whos talking to whom
TokenRing
Public UNI
UNI
Public ATMNetwork
NNI
NNI
NNI
Private ATM Network
Public ATMNetwork
B-ICI
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Virtual Path and Virtual Channels
ATM Physical LinkVirtual Channel Connection (VCC)
Virtual Path(VP)
Contains Multiple VCs
Virtual Channel Connection(VCC)
Contains Multiple VPs
Virtual Channel(VC)
Logical PathBetween ATM End Points
Virtual Channels (VC)
Virtual Channels (VC)
E3
OC12 Virtual Path (VP)
Virtual Path (VP)
Connection Identifier = VPI/VCI
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VP and VC Switching
VCI 1 VCI 2 VCI 3 VCI 4
VPI 2VPI 3VPI 1
VPI 2
VPI 3
VPI 5
VPI 1
VPI 4
Port 1
Port 2
Port 3
VCI 1
VCI 2
VCI 1
VCI 2
VP Switch
VC Switch
VCI 3
VCI 4
VCI 1
VCI 2
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Virtual Channels & Virtual Paths
This hop-by-hop forwarding is known as cell relay
Virtual Channel Connection (VCC)
Virtual PathConnection (VPC)
VPSwitch
VCSwitch
VCSwitch
NNI NNI
VPI = 2VCI = 44
VPI = 1VCI = 1
VPI = 26VCI = 44
VPI = 20VCI = 30
UNIUNI
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NQoS2013HCMUT
Rudimentary ATM Concepts
Physical layer
Signaling
Cell formatConnection types
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NQoS2013HCMUT
Creating Cells from PacketsDest.
AddressSource
Address DataFrameCheck
PayloadHeader
Packet
Cells
PayloadHeader
PayloadHeader
PayloadHeader
SARSegmentation and Reassembly
Segmentation Happens at Source
Reassembly Happens at Destination
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NQoS2013HCMUT
ATM Cell Header
5 ByteHeader
48 BytePayload
ATM Cell
53 Bytes
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ATM Cell Header Details
GFC Generic Flow ControlUNI Cells Only!
VPI/VCI Identifies VirtualPaths and Channels
PTI Payload Type Identifier 3 Bits:
1. User/Control Data2. Congestion3. Last Cell
CLP Cell Loss Priority Bit
HEC Header Error Check8 Bit CRCATM NNI Cell
48 BytePayload
VPI (12) VCI (16)
PTI CLP
HEC
ATM UNI Cell
48 BytePayload
GFC (4)VPI (8)
VCI (16)
PTI CLP
HEC
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Rudimentary ATM Concepts
Physical layer
Signaling
Cell formatConnection types
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NQoS2013HCMUT
ATM Connection Types
PVC
SVC
Soft PVC
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Connection Types
Connectionless: Packet Routing
Path 1 = S1, S2, S6, S8Path 2 = S1, S4, S7, S8
Data can take different pathand can arrive out of order
Connection Oriented: Cell Switching
VC = S1, S4, S7, S8Data takes the same pathand arrives in sequence
S2 S6
S4 S7
S3 S5
S1 S8
1
1
1
2 2
2
S2 S6
S4 S7
VC
S1 S8S3 S5
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Permanent Virtual Circuit (PVC)
VPI/VCI tables in network equipment updated by administrator
A
B
D
C
Input OutputPort VPI/VCI Port VPI/VCI
1 33 3 022 15 3 14
1 64 3 29
3 29 1 64
Input OutputPort VPI/VCI Port VPI/VCI
1 29 3 452 52 4 15
1 64 3 29
3 29 1 64
Input OutputPort VPI/VCI Port VPI/VCI
1 45 2 16
2 52 1 291 64 3 29
3 29 1 64
29
52
10
16
15
4514
43
Input OutputPort VPI/VCI Port VPI/VCI
1 16 2 43
3 14 4 101 64 3 29
3 29 1 64
1
2
4 2
3
3
2
4
12
3
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NQoS2013HCMUT
Switched Virtual Circuit (SVC)
Dynamically set up connections via signaling
B
D
1
2
4 1
3
3
2
4
12
UNISignaling
NNISignaling C
UNISignaling
Input OutputPort VPI/VCI Port VPI/VCI
1 64 3 29
3 29 1 64
Input OutputPort VPI/VCI Port VPI/VCI
2 52 1 291 64 3 29
3 29 1 64
Input OutputPort VPI/VCI Port VPI/VCI
1 29 3 45
1 64 3 29
3 29 1 64
Input OutputPort VPI/VCI Port VPI/VCI
1 64 3 29
3 29 1 64A
3
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NQoS2013HCMUT
Switched Virtual Circuit (SVC)
Dynamically tear down connections via signaling
B
D
1
2
4 1
3
3
2
4
12
NNISignaling C
UNISignaling
Input OutputPort VPI/VCI Port VPI/VCI
1 64 3 29
3 29 1 64
Input OutputPort VPI/VCI Port VPI/VCI
2 52 1 291 64 3 29
3 29 1 64
Input OutputPort VPI/VCI Port VPI/VCI
1 29 3 45
1 64 3 29
3 29 1 64
Input OutputPort VPI/VCI Port VPI/VCI
1 64 3 29
3 29 1 64A
3
UNISignaling
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NQoS2013HCMUT
Soft PVC
PVC established manually across UNI and dynamically across NNI
B
D
1
1
2
NNISignaling
UNISignaling
Input OutputPort VPI/VCI Port VPI/VCI
1 64 3 29
3 29 1 64
Input OutputPort VPI/VCI Port VPI/VCI
2 52 1 291 64 3 29
3 29 1 64
Input OutputPort VPI/VCI Port VPI/VCI
1 29 3 45
1 64 3 29
3 29 1 64
Input OutputPort VPI/VCI Port VPI/VCI
1 64 3 29
3 29 1 64
3
UNISignaling
1 29 3 45
1 16 2 43
C
A
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NQoS2013HCMUT
ATM Reference model
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NQoS2013HCMUT
ATM Layer
Provides VPI/VCI values in headerEnsures that cells stay in the correct order
ATMAdaptation Layer
(AAL)
ATM Layer
Virtual Channel
Connection (VCC)
Virtual PathConnection (VPC)
VPSwitch
VCSwitch
VCSwitch
NNI NNI
VPI = 12VCI = 44
VPI = 0VCI = 38
VPI = 26VCI = 44
VPI = 0VCI = 36
UNI UNI
Physical Layer
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NQoS2013
HCMUT
AALThe AAL segments larger packets from Frame Relay, X.25, Ethernet etc.into cells and back again. In addition it takes care of applications thatneed Constant Bit Rates (CBR) and Variable Bit Rates (VBR) . The twosublayers within the AAL that perform these functions arethe Convergence Sublayer (CS) and the Segmentation and ReassemblySublayer (SAR) . These are detailed in the adaptation layer header that sits
between the ATM cell header and the payload data.The CS provides the timing relationships between source and destinationfor CBRs and VBRs, plus it provides the correct mode for connectionoriented or connectionless services. The Common Part (CP) works withthe SAR and provides management information and the Service Specific
(SS) sublayer is specific to the type of service.The SAR examines the packets, determines the number of cells requiredfor each packet and creates SAR-PDUs which are the 48-byte payloads.The 5-byte header is then added to form the ATM cell
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NQoS2013
HCMUT
SAR
CS
AAL
ATM Adaptation LayerAAL
AAL = CS + SARCScell taxSARcell packet
PBXATMAdaptation Layer (AAL)
ATM Layer
Physical Layer
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NQoS2013
HCMUT
AAL2
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NQoS2013
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AAL3/4
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NQoS2013
HCMUT
AAL5
ATM S i C t i
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NQoS2013
HCMUT
ATM Service Categories
Service CriteriaTraffic descriptors
QoS parameters
Service CategoriesConstant Bit Rate (CBR)
Variable Bit Rate (VBR)Unspecified Bit Rate (UBR)
Available Bit Rate (ABR)
ATM S i C it i
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NQoS2013
HCMUT
Contract
ATM Service Criteria
Contract
ContractTraffic Descriptors
Peak cell rate
Sustainable cell rateMaximum burst sizeMinimum Cell Rate
Quality of ServiceDelayCell loss
ATM Network
ATM S i C it i
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NQoS2013
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ATM Service Criteria
Peak Cell Rate PCRMaximum data ratea connection can handle without losing dataSustainable Cell Rate SCRAverage ATMcell throughput the application is permittedMaximum Burst Size MBSSize of themaximum burst of contiguous cells that
can be transmittedMinimum Cell Rate MCRRate of anapplications ability to handle latency
Traffic Descriptors
ATM Service Criteria
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NQoS2013
HCMUT
ATM Service Criteria
Maximum Cell Transfer Delay MCTDHow long the network can take to transmit a cell
from one endpoint to anotherCell Delay Variation Tolerance CDVTLine distortion caused by change in interarrival
times between cells aka jitter
QoSDelay
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ATM Service Categories
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NQoS2013
HCMUT
ATM Service Categories
Service CriteriaTraffic parameters
QoS parameters
Service CategoriesConstant Bit Rate (CBR)
Variable Bit Rate (VBR)Unspecified Bit Rate (UBR)
Available Bit Rate (ABR)
ATM Service Categories
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NQoS2013
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ATM Service Categories
QoSTraffic Descriptor
Application
Constant Bit Rate (CBR)
Real Time Voice and Video
LOW HIGH
Tolerance
Cell DelayCell Loss
PCRPeak Cell Rate
ATM Service Categories
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ATM Service CategoriesVariable Bit Rate (VBR-RT/VBR-NRT)
QoSTraffic Descriptor
LOW HIGH
Tolerance
Cell Delay(NRT)Cell Delay (RT)
PCR
SCR
Peak Cell Rate
Sustainable Cell Rate
MBSMaximum Burst Size Cell Loss
Packetized Voice/Video, SNA
Application
ATM Service Categories
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NQoS2013
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ATM Service Categories
QoSTraffic Descriptor
Application
Unspecified Bit Rate (UBR)
Data Transfer
LOW HIGHNo GuaranteesSend and Pray
Tolerance
Cell LossCell Delay
ATM Service Categories
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NQoS2013
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ATM Service CategoriesAvailable Bit Rate (ABR)
Also usesCongestionFeedback
Mechanisms
LAN Interconnect for Data
QoSTraffic Descriptor
LOW HIGHPCR
MCRPeak Cell Rate
Minimum Cell Rate
Tolerance
Cell Loss Cell Delay
Application
Traffic Management
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Faculty of EEE
NQoS2013
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Traffic Management
Why traffic management?Traffic control techniquesABR congestion feedback
Why Traffic Management?
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NQoS2013
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Why Traffic Management?
Proactively combat congestionProvision for priority control
Maintain well-behaved traffic
Why Traffic Management?
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NQoS2013
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Ethernet (1500 Bytes) = 32 CellsFDDI (4470 Bytes) = 96 Cells
IP over ATM1577 (9180 Bytes) = 192 Cells
Why Traffic Management?
Lose one cell and the rest are uselessNeed to re-transmit 32+ cells for one cell lostCongestion collapse is the result
TCP/IP Packet
X
Cell Loss Datas Critical Enemy
Traffic Control Techniques
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NQoS2013
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Traffic Control Techniques
Connection management Acceptance
Traffic management PolicingTraffic smoothing Shaping
Traffic Control Techniques
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NQoS2013
HCMUT
Contract
Traffic Control Techniques
Contract
Contract
Traffic ParametersPeak cell rateSustainable cell rateBurst toleranceEtc.
Quality of ServiceDelay
Cell loss
ATM Network
Connection Management
Traffic Control Techniques
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NQoS2013
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Traffic Control Techniques
Connection Admission Control (CAC)
ATM Network
I want a VC:X Mbps
Y DelayZ Cell Loss
CACCan I Support thisReliably without
Jeopardizing OtherContracts?
Noor
Yes, Agree to aTraffic Contract
Guaranteed QoS Request
Contract
Connection Management
Traffic Control Techniques
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Traffic Control Techniques
ATM Network
You areNot in Conformance
with the Contract.What Should the
Penalty Be??
PASS MARK CLP BIT DROP
?DECISION?
Contract
Usage Parameter Control (UPC) aka Policing
REBELAPPLICATION
Traffic Management
Traffic Control Techniques
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Traffic Control Techniques
CLP ControlWhen congested, drop marked cellsPublic UNIGeneric Cell Rate Algorithm (GCRA)
0 0 0 0 1 0Marked
UPC
PASS MARK CLP BIT DROP
?DECISION?
Traffic Management
Dr op
Traffic Control Techniques
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q
Tail Packet Discard (TPD)Discard cells from same bad packet
0 0 0 0 1 0Marked
UPC
Traffic Management
3 2
Dr op
Traffic Control Techniques
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ATM/Switch
6
1 0
5
4
Output Buffer EOM
UPC
7 3 2 1
X
Intelligent Tail Packet Discard
Output Queue
EOM
EPD Threshold
EOM
Early Packet Discard
aka UBR+
qTraffic Management
Traffic Control Techniques
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Switch without Packet Discard
Switch with Intelligent Packet Discard
Maximize Goodput
qTraffic Management
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Traffic Control Techniques
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RMResource Management cells
Rate-based feedback mechanisms:EFCI markingRelative rate marking
Explicit rate markingVS/VD
ABR Congestion Feedback
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Traffic Control Techniques
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Relative rate markingSwitches can set congestion flagin backward RM cells
Source
Forward
BackwardCongestionExperiencedSlow Down
RM X
RM
ABR Congestion Feedback
Destination
Traffic Control Techniques
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ABR Congestion Feedback
Explicit rate markingSwitches can tell source at exactly what rate to transmit
Source
Destination
Forward
Backward
RM
RM
Congestion ExperiencedSlow Down X Amount
CongestionExperienced
Slow Down
Traffic Control Techniques
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VS/VDVirtual source/virtual destinationBreaks the feedback loop into separate segmentsShortens length of feedback loop
Source
Destination
Forward
Backward
CongestionExperienced
Slow Down
ABR Congestion Feedback
Traffic Control Techniques
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Absorb traffic bursts from simultaneous connectionsSwitches schedule traffic based on priorityof traffic according to QoSSwitch must reallocate buffers as the traffic mixchangesEffective buffering maximizes throughput
of usable cells as opposed to raw cells(aka goodput)
Buffers Are Your Friend
IP/ATM Model
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Mapping cells into SONET/SDH
Using logical IP subnet (LIS) instead of using regular IPsubnetTwo models: Classical IP/ATM (CIP) and LAN Emulation(LANE) for IP/ATMClassical IP/ATM (CIP): link driver has two concerns:
Address resolution: discovering the link-level next-hopcorresponding to a given IP next-hop address known to be onthe linkPacket Transport: actually establishing link-level resources totransfer the packet to the indicated next-hop
AAL5 is used for encapsulation of IP packets For GS use CBR or rt-VBR For CL use non-rt VBR or ABR with a minimum cell rate For BE use UBR or ABR
IP/ATM QoS
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Controlling QoS in IP/ATM involves 2 aspects:Upgrading the IP node with sufficient CQS architecture toprovide differentiated scheduling of traffic toward any next-hopDefining rules for establishing and using parallel ATM VCstoward a given next-hop
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Internet core network
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Router based core network
Internet core network (cont)
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NQoS2013HCMUT
Processing can not meet bandwidth demands
Bottle-neck in software-based routersAvailable router interfaces not provide trafficaggregation
Metric-based routing was no longer scalableDensely connected networks lead to inefficient use ofnetwork resourcesDestination based routing tends to aggregate alltraffic to the same destination: not utilize links
Internet core network (1)
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Switch based core network
Internet core network (cont)
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Faster and simpler forwarding, better traffic aggregation
Fix size cells can be handled in hardware to speed upConnection-oriented forwarding algorithm improves
performance gain: based on short fix length connectionidentifiers
The ASIC technology : IP packets can be forwarded with highspeed. ATM interfaces have even fallen behind the latestincreases of optical network (packet over SDH/SONET)
Waste of bandwidth : 5/48 bytes of header.
Complex network management: physical ATM switchedinfrastructure and logical IP network topology. Each layer usesits own addressing scheme and routing protocol
Internet core network (cont)
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The n-squared problem : when adding or shutting
down any router will create enormous signaling loadIGP stress : intra-domain routing is not conceived for
fully meshed topology. With high number of routingpeer routers: too much routing information has to beexchanged
Multi-Protocol Label Switching (MPLS) can offer
solutions that create a combination of the advantagesfrom both of these worlds
MPLS NGN
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MPLS NGN (cont)
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NQoS2013HCMUT
Forwarding based on label: speed up processing at node
Forwarding mechanism: label (explicit routing) or IP header(hop-by-hop routing)
Operating on any layer 2 technologies: ATM, Ethernet, FR
Allows for both traffic aggregation and disaggregation
Support VPN : using 64-bit VPN address (total 92 bits)Allow SPs embed into the IP network : TE and traditional QoS of
layer 2 : using DSCP and processing queues based on its packetspriority
Easy management and operation
Traditional IP Routing
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Choosing the next hop
Open Shortest Path First (OSPF) to populate the routingtable
Route look up based on the IP addressFind the next router to which the packet has to be sent
Replace the layer 2 address
Each router performs these steps
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Distributing Routing Information(1)
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3
1
0125.50
145.40
2
AddressPrefix
Address
Prefix
AddressPrefix
Path Path
Path
125.50
145.40
125.50
145.40
125.50
13
3 0
2
Data 125.50.33.85Data 125.50.33.85
Disadvantages
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Header analysis performed at each hop
Increased demand on routersUtilizes the best available pathSome congested links and some underutilized links!
Degradation of throughputLong delays
More losses
No QoSNo service differentiation
Not possible with connectionless protocols
Need for MPLSR id th f I t t
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Rapid growth of Internet
New latency dependent applicationsQuality of Service (QoS)
Less time at the routers
Traffic EngineeringFlexibility in routing packets
Connection-oriented forwarding techniques withconnectionless IP
Utilizes the IP header information to maintain interoperability with IP
based networksDecides on the path of a packet before sending it
What is MPLS?l l l h h
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Multi Protocol supports protocols even other than IP
Supports IPv4, IPv6, IPX, AppleTalk at the network layerSupports Ethernet, Token Ring, FDDI, ATM, Frame Relay, PPPat the link layer
Label short fixed length identifier to determine a
routeLabels are added to the top of the IP packetLabels are assigned when the packet enters the MPLSdomain
Switching forwarding a packetPackets are forwarded based on the label valueNOT on the basis of IP header information
MPLS BackgroundIntegration of layer 2 and layer 3
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Integration of layer 2 and layer 3Simplified connection-oriented forwarding of layer 2
Flexibility and scalability of layer 3 routing
MPLS does not replace IP; it supplements IP
Traffic can be marked, classified and explicitly routed
QoS can be achieved through MPLS
IP/MPLS comparison
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Routing decisions
IP routing based on destination IP addressLabel switching based on labels
Entire IP header analysis
IP routing performed at each hop of the packets path in the network
Label switching performed only at the ingress router
Support for unicast and multicast data
IP routing requires special multicast routing and forwarding
algorithmsLabel switching requires only one forwarding algorithm
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Forwarding Equivalence Class (FEC)A f k h i h f di
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A group of packets that require the same forwarding
treatment across the same pathPackets are grouped based on any of the following
Address prefixHost addressQuality of Service (QoS)
FEC is encoded as the label
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FEC example (contd)Assume packets have the destination address and QoS
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NQoS2013HCMUT
Assume packets have the destination address and QoSrequirements as124.48.45.20 qos = 1143.67.25.77 qos = 1143.67.84.22 qos = 3124.48.66.90 qos = 4143.67.12.01 qos = 3
FEC 1 label a FEC 2 label b FEC 3 label c FEC 4 label d143.67.25.77 124.48.45.20 143.67.84.22 124.48.66.90
143.67.12.01
Example of a MPLS network
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Label Switching Router (LSR)A router/switch that supports MPLS
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NQoS2013HCMUT
A router/switch that supports MPLS
Can be a routerCan be an ATM switch + label switch controller
Label swapping
Each LSR examines the label on top of the stackUses the Label Information Base (LIB) to decide theoutgoing path and the outgoing label
Removes the old label and attaches the new label
Forwards the packet on the predetermined path
Label Switched Path(LSP)LSP defines the path through LSRs from ingress to
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NQoS2013HCMUT
LSP defines the path through LSRs from ingress to
egress routerFEC is determined at the LER-ingressLSPs are unidirectional
LSP might deviate from the IGP shortest path
LSP
LSP
LDP
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NQoS2013HCMUT
Label Distribution Protocol
LDP
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NQoS2013HCMUT
LDP
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NQoS2013HCMUT
LDP - AdvantagesExplicit routing
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NQoS2013HCMUT
p g
Set up a LSP between Ingress Router and EgressRouterLabel request for each hop on down-streamLabel mapping : up-streamErrors occur: router sends a alarm message toneighbors or operating routers to re-direct for currentLSP
Less resources (compared with RSVP)
LDP - DisadvantagesSlow error recovery
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NQoS2013HCMUT
y
Not support dynamically re-optimization of trafficflowsTransient periods: efficiency of Resource Location
could be influenced by routing traffic.Require means to restore the LSP to the original
routes once congestion has subsidedFATE : using dynamic reroute mechanism
Shim HeaderA short, fixed length identifier (32 bits)
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, g ( )
Sent with each packetLocal between two routersCan have different labels if entering from different routersOne label for one FEC
Decided by the downstream routerLSR binds a label to an FECIt then informs the upstream LSR of the binding
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Time To Live (TTL)TTL value decremented by 1 when it passes through an
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NQoS2013HCMUT
y p g
LSRIf TTL value = 0 before the destination, discard thepacket
Avoids loops may exist because of somemisconfigurations
Multicast scoping limit the scope of a packetSupporting the traceroute command
TTL (contd)Shim header
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NQoS2013HCMUT
Has an explicit TTL fieldInitially loaded from the IP header TTL fieldAt the egress LER, value of TTL is copied into the TTL field ofthe IP header
Data link layer header (e.g VPI/VCI)No explicit TTL fieldIngress LER estimates the LSP lengthDecrements the TTL count by the LSP lengthIf initial count of TTL less than the LSP length, discard the
packet
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Label stack (contd)
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NQoS2013HCMUT
Labels scope and uniquenessLabels are local between two LSRs
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NQoS2013HCMUT
Rd might give label L1 for FEC F and distribute it to Ru1At the same time, it might give a label L2 to FEC F anddistribute it to Ru2L1 might not necessarily be equal to L2
Can there be a same label for different FECs?Generally, NOBUT no such specificationLSR must have different label spaces to accommodate bothSHIM header specifies that different label spaces used forunicast packets and multicast packets
Invalid labelsWhat should be done if an LSR receives an invalidl b l?
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NQoS2013HCMUT
label?Should it be forwarded as an unlabeled IP packet?
Should it be discarded?
MUST be discarded!
Forwarding it can cause a loopSame treatment if there is no valid outgoing label
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Route selection (contd)Hop by Hop
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NQoS2013HCMUT
Allows each LSR to individually choose the next hopThis is the usual mode today in existing IP networks
No overhead processing as compared to IP
Explicit routingA single router, generally the ingress LER, specifies severalor all of the LSRs in the LSP
Provides functionality for traffic engineering and QoSo Several: loosely explicitly routed
o All: strictly explicitly routed
E.g. CR-LDP, TE-RSVP
Label Information Base (LIB)Table maintained by the LSRs
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NQoS2013HCMUT
Contents of the tableIncoming label
Outgoing labelOutgoing path
Address prefixIncominglabel Address Prefix
OutgoingPath
Outgoinglabel
LSR Forwarding Engine
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NQoS2013HCMUT
MPLS forwardingExisting routing protocols establish routes
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NQoS2013HCMUT
LDP establishes label to route mappingsLDP creates LIB entries for each LSR
Ingress LER receives packet,adds a labelLSRs forward labeled packets using label swapping
Egress LER removes the label and delivers the packet
FEC in MPLS
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NQoS2013HCMUT
MPLS forwarding (contd)
AddressPrefix
OutPath
InLabel
OutLabel
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NQoS2013HCMUT
Use label 8 for 145.40
Use label 9 for 125.50
Use label 2 for 125.50 andlabel 1 for 145.40
3
1
0125.50
145.40
2
AddressPrefix
OutPath
InLabel
OutPath
InLabel
OutLabel
OutLabel
125.50 125.50
125.50
145.40 145.40
3
3
2
1
2
1 8
9
9
0
1
2Address
Prefix
MPLS forwarding (contd)
AddressPrefix
OutPath
InLabel
OutLabel
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NQoS2013HCMUT
3
1
0125.50
145.40
2
AddressPrefix AddressPrefixOutPath InLabel OutPath InLabelOutLabel OutLabel
125.50 125.50
125.50
145.40 145.40
3
3
2
1
2
1 8
9
9
0
1
2
Data 125.50.33.85 2
Data 125.50.33.85 9
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NQoS2013HCMUT
DiffServ & MPLS
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DiffServ Architecture
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NQoS2013HCMUT
Differentiated ServicesThe IETF DiffServ Model
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NQoS2013HCMUT
Use 6 bits in IP header to sort traffic intoBehavior AggregatesAKA Classes!Defines a number of Per Hop Behaviors - PHBsTwo-Ingredient Recipe:
Condition the Traffic at the Edges Invoke the PHBs in the Core
Use PHBs to Construct Services such as VirtualLeased Line!
Defined PHBs
Expedited Forwarding (EF): RFC2598
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NQoS2013HCMUT
p g ( )dedicated low delay queueComparable to Guaranteed B/W in IntServ
Assured Forwarding (AF): RFC2597
4 queues 3 drop preferencesComparable to Controlled Load in IntServClass Selector: Compat. with IP PrecDefault (best effort)
AF PHB Group DefinitionAF Class 1: 001 dd 0
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NQoS2013HCMUT
4 independently-forwarded AF classesWithin each AF class, 3 levels of drop priority! This is very useful to protectconforming to a purchased, guarantee rate, while increasing chances ofpackets exceeding contracted rate being dropped if congestion isexperienced in the core.
AF Class 2: 010 dd 0
AF Class 3: 011 dd 0
AF Class 4: 100 dd 0
Eg. AF12 = Class 1, Drop 2, thus 001100
dd = drop preference
DiffServ Scalability via Aggregation
1000sof flows
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NQoS2013HCMUT
DiffServ scalability comes from:- aggregation of traffic on Edge- processing of Aggregate only in Core
Diff-Serv:
Aggregated Processing inCore
Scheduling/Dropping (PHB)based on DSCP
Diff-Serv:
Aggregated Processing inCore
Scheduling/Dropping (PHB)based on DSCP
Diff-Serv:
Aggregation on Edge
Many flows associated witha Class (marked with DSCP)
Diff-Serv:
Aggregation on Edge
Many flows associated witha Class (marked with DSCP)
MPLS Scalability via Aggregation
1000sof flows
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NQoS2013HCMUT
MPLS scalability comes from:- aggregation of traffic on Edge- processing of Aggregate only in Core
MPLS:
Aggregated Processing inCore
Forwarding based on label
MPLS:
Aggregated Processing inCore
Forwarding based on label
MPLS:
Aggregation on Edge
Many flows associated witha Forwarding EquivalentClass (marked with label)
MPLS:
Aggregation on Edge
Many flows associated witha Forwarding EquivalentClass (marked with label)
MPLS & DiffServ - The Perfect Match!
1000sof flows
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NQoS2013HCMUT
Because of same scalability goals, both models do:- aggregation of traffic on Edge- processing of Aggregate only in Core
MPLS: flowsassociated withFEC, mapped
into one label
MPLS: flowsassociated withFEC, mapped
into one label MPLS:Switchingbased onLabel
MPLS:Switchingbased onLabel
DS:Scheduling/Droppingbased on DSCP
DS:Scheduling/Droppingbased on DSCP
DS: flows associatedwith Class, mappedto DSCP
DS: flows associatedwith Class, mappedto DSCP
Non-MPLSDiff-Serv Domain
MPLSDiff-Serv Domain
MPLS - The Shim Header!!
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NQoS2013HCMUT
DSCPfield is not directly visible to MPLS Label Switch Routers (theyforward based on MPLS Header)
Information on DiffServ must be made visible to LSR in MPLS Header(using EXP field / Label)
0 1 2 30 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label | EXP |S| TTL |
DSCP
IPv4 Packet MPLS Header
DSCP
Driving PHB at Core LSR
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NQoS2013HCMUT
Driving PHB at Core LSRQoS consideration
Each distinct queuing and
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122Telecomm. Dept.Faculty of EEE
NQoS2013HCMUT
scheduling behavior may beencoded as a new FEC (LSP),ignoring the EXP fieldThe EXP field encodes up to 8
queuing and schedulingbehaviors for the same FEC (LSP)
The EXP field encodes up to 8queuing and scheduling
behaviors independent of FEC(LSP)
Driving PHB at Core LSRSome possible approaches:
Using Label to select a queue (Service Class) and using one or
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NQoS2013HCMUT
more EXP bits to encode different drop precedence levelsUsing Label to select a group of four queues, using 2 bitsfrom EXP to select one of those 4 queues and using theremaining bit from EXP to encode the drop precedence
Ignoring the Label and using four shared queues per outputinterface. 2 bits from EXP to select one of those 4 queues,and the remaining bit from EXP encodes the dropprecedence
Using Label to select a group of N queues (N
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NQoS2013HCMUT
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NQoS2013HCMUT
MPLS Traffic Engineering
125
MPLS TE & QoS The RelationshipMPLS TE designed as tool to improve backboneefficiency independently of core QoS
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NQoS2013HCMUT
techniques:MPLS TE compute routes for aggregates across all PHBs. A Single Chunk of Bandwidth requested for the Tunnel
MPLS TE performs admission control over a global b/w pool. Un-aware of bandwidth allocated to each Class / PHB
MPLS TE and MPLS DiffServ:Can run simultaneously in a network.Can provide their own individual benefits TE distributes aggregate load DiffServ provides differentiation
Are unaware of each other
Traffic Aggregate in IP networks
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NQoS2013HCMUT
Traffic Aggregate in MPLS networks
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NQoS2013HCMUT
Traffic Aggregate in MPLS networks
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NQoS2013HCMUT
TE Fast Reroute - Tunneling
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NQoS2013HCMUT
TE Global Fast Reroute (Makam)
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NQoS2013HCMUT
TE Region Fast Reroute
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NQoS2013HCMUT
TE Local Fast Reroute
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NQoS2013HCMUT
TE Haskin Fast Reroute
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NQoS2013HCMUT