differentiated services mpls doug young suh [email protected] last updated : aug 1, 2009 diffserv/rsvp
TRANSCRIPT
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
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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