Differentiated Services MPLS Doug Young Suh Last updated : Aug 1, 2009 diffServ/RSVP

intServ vs. diffServ QoS resolution intServ > diffServ per flow service Each 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 marking Bandwidth Broker SLA -Service level agreement -Interaction between domains -Static or dynamic

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

Header formats of IPv4/IPv6 Version (4) Traffic Class (8) Flow Label (20) Payload Length (16) Next Header (8) Hop Limit (8) Source Address (128) Destination Address (128) Version (4) HLEN (4) Type of Service (8) Total Length (16) Identification (16) Flags (3) Fragment Offset (3) TTL (8)Protocol (8) Header Checksum (16) Source IP Address (32) Destination IP Address (32) 012DTR67 Precedence level For routingCU delay throughput reliability DSCP (diffServ CodePoint)

Assignment of DSCPs to PHBs Used forBits 0, 1, 2 (class) Bits 3, 4 (drop precedence) Bit 6 EXP/LU (local use) xxxxx1 BE CSC 000 xxx(≠000) AF1 AF2 AF3 AF , 10, EF  Per Hop Behaviors (PHB)  Forwarding behavior (bandwidth, buffer)  EF (Expedited Forwarding), AF (Assured Forwarding)

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

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) diffServ/RSVP Buffer management Polling BA Classifier EF AF1 BE

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 diffServ/RSVP goldbronzesilver Drop probability Buffer occupancy

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 diffServ/RSVP MTU/aW MTU/W

Assured Forwarding (4 AFs) ⅹ (3 drop levels) = 12 code points AF vs. EF AFEF Reserved bandwidthYes Limited input rateNoYes Drop precedence inside one classYesNo Implementation usingWFQPQ, WFQ

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 University12

diffServ/RSVP MPLS Multi-protocol Label Switching (L2 : datalink protocol)

diffServ/RSVP Scalability Problem in intServ 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 SADASPDPPrdata Admission control Packet scheduler classifier data SADASPDPPr TSpec1 SADASPDPPr TSpec2 SADASPDPPr TSpec3 SADASPDPPr TSpec4 SADASPDPPr TSpec5 intServ routing table

diffServ/RSVP Label switching (path, resource) 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’ SADASPDPPrdata Admission control Packet scheduler classifier data TSpec1414 2222 3232 4545 5656 MPLS switching Label 1 R3 R2 R4 R6 SADA Label 4

diffServ/RSVP 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 lmpqlmpq mnqtmnqt VC#l VC#p VC#m VC#q VC#n VC#t

diffServ/RSVP 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 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 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 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