Differentiated Services MPLS

Doug Young Suhsuh@khu.ac.kr

Last updated : Aug 1, 2009

diffServ/RSVP

intServ vs. diffServ

QoS resolution intServ > diffServ

per flow serviceEach accepted flow is guaranteed.Scalability problem

per class service (aggregation service)

diffServ/RSVP

Diffserv/RSVP Architecture

diffServ/RSVP

Edge router:- per-flow service (intServ/RSVP)- marks packets of in- or out-profile

Core router:- per class service- buffering and scheduling - preference to in-profile packets- Expedited/Assured Forwarding

CR scheduling

...

r

b

ER markingBandwidth Broker

SLA

SLA-Service level agreement-Interaction between domains-Static or dynamic

Service metrics for SLA

QuantitativeDelay, jitter, bandwidthe.g. 90% of the packets will receive 75 msec delay

Qualitativee.g. ‘low loss’ service

Proportionale.g. AF1 will receive twice the bandwidth of AF2.

Yet, there exist open questions for topology or end-to-end services????

diffServ/RSVP

Header formats of IPv4/IPv6

Version(4)

TrafficClass (8)

Flow Label (20)

Payload Length (16)Next

Header (8)Hop

Limit (8)

Source Address (128)

Destination Address (128)

Version(4)

HLEN(4)

Type ofService (8)

Total Length (16)

Identification (16)Flags(3)

FragmentOffset (3)

TTL (8) Protocol (8)Header Checksum

(16)

Source IP Address (32)

Destination IP Address (32)

0 1 2 D T R 6 7

Precedence

level

For routing CU

delaythroughput

reliability

DSCP (diffServ CodePoint)

Assignment of DSCPs to PHBs

Used for Bits 0, 1, 2(class)

Bits 3, 4(drop precedence)

Bit 6

EXP/LU(local use)

xxx xx 1

BECSC

000xxx(≠000)

0000

00

AF1AF2AF3AF4

001010011100

01, 10, 1101, 10, 1101, 10, 1101, 10, 11

0000

EF 101 11 0

Per Hop Behaviors (PHB) Forwarding behavior (bandwidth, buffer)

EF (Expedited Forwarding), AF (Assured Forwarding)

Edge Router : Traffic Conditioning

diffServ/RSVP

Per-flow per-classClassifier of micro-flow w.r.t. agreed traffic profileMarker : low, medium, high drop precedence

CR : traffic management

Core Router : per-class BA (behavior aggregate) classifier

PHBEF : guaranteed service, WFQ (weighted fair queuing)AF : 4 classes with 3 levels (high, medium, low drop procedure levels), RED (random early discard)

diffServ/RSVP

Buffer management

Polling

BA

Classifier

EF

AF1

BE

CR : buffer managing and polling

Buffer managementTail drop (traditional)RED (Random Early Drop)RIO : RED with drop precedence level

SchedulingPriority queuingWeighted fair queuing

Round robin scheduling with weightsNo starvation of low priority classes

diffServ/RSVP

goldbronze

silver

Dropprobability

Buffer occupancy

Expedited Forwarding

Departure rate < configured rate(#bits Tx during MTU/aW) / (MTU/aW) > aWW : link bandwidth, a : portion of the flow

Priority queuing or WFQEF aggregation possible“Virtual wire” : a dedicated line e.g. VoIP

diffServ/RSVP

MTU/aW

MTU/W

Assured Forwarding

(4 AFs) ⅹ(3 drop levels) = 12 code pointsAF vs. EF

AF EF

Reserved bandwidth Yes Yes

Limited input rate No Yes

Drop precedence inside one class

Yes No

Implementation using WFQ PQ, WFQ

Conclusion

Per-class diffServ < per-flow intServIn QoS resolutionSolve scalability problem of intServ

Classes of network QoSDSCP(DiffServ Code Point) in IP headerEF > AF with different scheduling policy

How to relate toScalable video coding?UEP/ULP in transport layer?and lower layers (IEEE802.11&16, UMTSLTE)

23年 4月 20日 MediaLab , Kyunghee University

12

diffServ/RSVP

MPLSMulti-protocol Label Switching

(L2 : datalink protocol)

diffServ/RSVP

Scalability Problem in intServintServ for a packet includes,

Identification of intServ packets for classifier

5 tuples : (SA, DA), (source port, receiver port), protocol

Searching for the service spec. for the packet

Traffic policing and scheduling

Admission control

Packetscheduler

classifier

data

SA DA SP DP Pr TSpec1SA DA SP DP Pr TSpec2SA DA SP DP Pr TSpec3SA DA SP DP Pr TSpec4SA DA SP DP Pr TSpec5

intServ routing table

diffServ/RSVP

Label switching (path, resource)

5 tuple during CAC 1 label for packet switchingTo reduce identification time i.e. switching (routing) delay

LABEL swapping

diffServ only for ‘resource’, not for ‘path’

SA DA SP DP Pr data

Admission control

Packetscheduler

classifier

data

TSpec14TSpec22TSpec32TSpec45TSpec56

MPLS switching

Label 1

R3R2R4R6R6

SA DALabel 4

diffServ/RSVP

Motivations of MPLSScalability problemVirtual circuit routing (circuit as for voice service)

Connection oriented, guaranteed QoSSwitching by simple VC table lookupNot shortest path routing, but QoS routing with provisioning

lmpq

mnqt

VC#l

VC#p

VC#mVC#q

VC#n

VC#t

diffServ/RSVP

Label Switching in a MPLS domain

Labeled at the ingress to identify its FECFEC : Forwarding Equivalent Class

Forwarded by LSRs along LSP in a MPLS domain

LSR : Label Switching RouterLSP : Label Switching PathLabel swapping with QoS treatment

Path typesPoint-to-point, multipoint-to-point, point-to-multipoint, multipoint-to-multipoint

diffServ/RSVP

Applying MPLS (1)

Constraint-based routingA path can be set up given certain QoS constraints.Explicit routing ∈ constraint-based routing

Traffic engineeringTo optimize network performance, TE is used instead of the shortest path routingFor explicit path, RSVP extension for MPLS can be used

diffServ/RSVP

Applying MPLS (2)

RSVP over MPLSSignaling between pair of routers, rather than pair of hostsCollection of flows sharing a common path and network resources

diffServ over MPLSAggregated behavior can be mapped onto MPLS labels.The precedence / class of service can be inferred from the label.

diffServ/RSVP

Benefits of MPLS

Simplified forwarding, simpler than intServHeavy processing on the edge, pure label based forwarding in the core

Facilitates mapping from IP packets to FECQoS routing, explicit routing

Traffic engineering : optimize network performance

Virtual Private Networks (VPN)

Multi-protocols on the same networkIP, frame relay, ATM, VPNs, IP tunneling

Future topic: IPv6 flow label and MPLS