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Differentiated Services MPLS

Differentiated Services MPLS. Doug Young Suh suh@khu.ac.kr Last updated : Aug 1, 2009. intServ vs. diffServ. QoS resolution intServ > diffServ per flow service Each accepted flow is guaranteed. Scalability problem per class service (aggregation service). Diffserv/RSVP Architecture.

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Differentiated Services MPLS

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  1. Differentiated Services MPLS Doug Young Suh suh@khu.ac.kr Last updated : Aug 1, 2009 diffServ/RSVP

  2. intServ vs. diffServ • QoS resolution intServ > diffServ • per flow service • Each accepted flow is guaranteed. • Scalability problem • per class service (aggregation service) diffServ/RSVP

  3. Diffserv/RSVP Architecture r b ER marking Edge router: - per-flow service (intServ/RSVP) - marks packets of in- or out-profile Bandwidth Broker Core router: - per class service - buffering and scheduling - preference to in-profile packets - Expedited/Assured Forwarding SLA • SLA • Service level agreement • Interaction between domains • Static or dynamic CR scheduling . . . diffServ/RSVP

  4. Service metrics for SLA • Quantitative • Delay, jitter, bandwidth • e.g. 90% of the packets will receive 75 msec delay • Qualitative • e.g. ‘low loss’ service • Proportional • e.g. AF1 will receive twice the bandwidth of AF2. • Yet, there exist open questions for topology or end-to-end services???? diffServ/RSVP

  5. Version (4) Traffic Class (8) Flow Label (20) Version (4) HLEN (4) Type of Service (8) Total Length (16) Payload Length (16) Next Header (8) Hop Limit (8) Identification (16) Flags (3) Fragment Offset (3) TTL (8) Protocol (8) Header Checksum (16) Source Address (128) Source IP Address (32) Destination IP Address (32) Destination Address (128) Header formats of IPv4/IPv6 DSCP (diffServ CodePoint) Precedence level For routing CU 0 1 2 D T R 6 7 delay reliability throughput

  6. Assignment of DSCPs to PHBs • Per Hop Behaviors (PHB) • Forwarding behavior (bandwidth, buffer) • EF (Expedited Forwarding), AF (Assured Forwarding)

  7. Edge Router : Traffic Conditioning • Per-flow  per-class • Classifier of micro-flow w.r.t. agreed traffic profile • Marker : low, medium, high drop precedence diffServ/RSVP

  8. CR : traffic management • Core Router : per-class • BA (behavior aggregate) classifier • PHB • EF : guaranteed service, WFQ (weighted fair queuing) • AF : 4 classes with 3 levels (high, medium, low drop procedure levels), RED (random early discard) Buffer management EF Polling BA Classifier AF1 BE diffServ/RSVP

  9. CR : buffer managing and polling • Buffer management • Tail drop (traditional) • RED (Random Early Drop) • RIO : RED with drop precedence level • Scheduling • Priority queuing • Weighted fair queuing • Round robin scheduling with weights • No starvation of low priority classes Drop probability bronze silver gold Buffer occupancy diffServ/RSVP

  10. Expedited Forwarding • Departure rate < configured rate • (#bits Tx during MTU/aW) / (MTU/aW) > aW • W : link bandwidth, a : portion of the flow • Priority queuing or WFQ • EF aggregation possible • “Virtual wire” : a dedicated line e.g. VoIP MTU/W MTU/aW diffServ/RSVP

  11. Assured Forwarding • (4 AFs) ⅹ(3 drop levels) = 12 code points • AF vs. EF

  12. Conclusion • Per-class diffServ < per-flow intServ • In QoS resolution • Solve scalability problem of intServ • Classes of network QoS • DSCP(DiffServ Code Point) in IP header • EF > AF with different scheduling policy • How to relate to • Scalable video coding? • UEP/ULP in transport layer? • and lower layers (IEEE802.11&16, UMTSLTE) MediaLab , Kyunghee University

  13. MPLSMulti-protocol Label Switching(L2 : datalink protocol) diffServ/RSVP

  14. Scalability Problem in intServ SA DA SP DP Pr data • intServ 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 intServ routing table 1 SA DA SP DP Pr TSpec 2 SA DA SP DP Pr TSpec 3 SA DA SP DP Pr TSpec 4 SA DA SP DP Pr TSpec 5 SA DA SP DP Pr TSpec Admission control classifier Packet scheduler data diffServ/RSVP

  15. Label switching (path, resource) SA DA SP DP Pr data • 5 tuple during CAC  1 label for packet switching • To reduce identification time i.e. switching (routing) delay • LABEL swapping • diffServ only for ‘resource’, not for ‘path’ MPLS switching 14 R3 TSpec 22 R2 TSpec 32 TSpec R4 45 TSpec R6 56 TSpec R6 Admission control classifier Packet scheduler Label 1 data SA DA Label 4 diffServ/RSVP

  16. Motivations of MPLS • Scalability problem • Virtual circuit routing (circuit as for voice service) • Connection oriented, guaranteed QoS • Switching by simple VC table lookup • Not shortest path routing, but QoS routing with provisioning VC#n VC#l VC#m lm pq mn qt VC#q VC#p VC#t diffServ/RSVP

  17. Label Switching in a MPLS domain • Labeled at the ingress to identify its FEC • FEC : Forwarding Equivalent Class • Forwarded by LSRs along LSP in a MPLS domain • LSR : Label Switching Router • LSP : Label Switching Path • Label swapping with QoS treatment • Path types • Point-to-point, multipoint-to-point, point-to-multipoint, multipoint-to-multipoint diffServ/RSVP

  18. Applying MPLS (1) • Constraint-based routing • A path can be set up given certain QoS constraints. • Explicit routing ∈ constraint-based routing • Traffic engineering • To optimize network performance, TE is used instead of the shortest path routing • For explicit path, RSVP extension for MPLS can be used diffServ/RSVP

  19. Applying MPLS (2) • RSVP over MPLS • Signaling between pair of routers, rather than pair of hosts • Collection of flows sharing a common path and network resources • diffServ over MPLS • Aggregated behavior can be mapped onto MPLS labels. • The precedence / class of service can be inferred from the label. diffServ/RSVP

  20. Benefits of MPLS • Simplified forwarding, simpler than intServ • Heavy processing on the edge, pure label based forwarding in the core • Facilitates mapping from IP packets to FEC • QoS routing, explicit routing • Traffic engineering : optimize network performance • Virtual Private Networks (VPN) • Multi-protocols on the same network • IP, frame relay, ATM, VPNs, IP tunneling • Future topic: IPv6 flow label and MPLS diffServ/RSVP

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