Implementing QoSOutlineWhat?What? (continued)Slide 5Where?Where? (continued)MechanismsMechanisms (continued)Slide 10Slide 11Slide 12Slide 13PricingUCBImplementing QoSJean WalrandEECSUCBOutlineWhat?Bandwidth, DelayWhere?End-to-End, Edge-to-Edge, Edge-to-End, OverlayMechanismsAccess ControlPacket MarkingVegasIncentive-Compatible ProtocolsDiffServ, MPLSPricingFlat, Usage, CongestionUCBWhat?Throughput: R MbpsFlow: e.g., TCP connectionPipe: e.g., (IP source, IP destination)Possibly, class (e.g., VoIP)Hose: Aggregate rate out of portTimescale1 Mbps over every ms1 Mbps over every secondUCBWhat? (continued)Latency:Upper bound: T Dmax[e.g., conference => Dmax 200ms]Jitter: Tmax – Tmin Jitter [Playback buffer => CBR]UCBWhat? (continued)Other:Security: e.g., VPN. Measure of security? [Physical: Fiber; Link: VLAN; IP: Ipsec; …]Availability: e.g., except for 1 hour every 10 years … [MTBF, MTBR]UCBWhere?End-to-endEdge-to-edgeEdge-to-edgeUCBWhere? (continued)Overlay Network= QoS box= edge-to-edge with QoS ..UCBMechanismsAccess ControlExample: MAN1 Gbps(bi-dir)RPolice R to 1 Gbps/N => GuaranteedUCBMechanisms (continued)Packet Marking (Frank Kelly)Mark with probability that the extra packet creates a loss;User pays per mark and slows down when pay rate reaches budget Revenues = Loss rate (times unit cost) Distributed according to “willingness to pay”By choosing unit cost, adjust loss rate. Throughput is then divided according to user utilities.=> Single class, but differentiated services.UCBMechanisms (continued)Vegas + Window = rate x Prop + backlogTry to maintain a fixed backlogEqual backlogs => Equal throughputs (B. Davie)Extension to multiple bottleneck case (J. Mo)Difficulty: Not compatible with RenoUCBMechanisms (continued)Incentive-Compatible ProtocolsProblem: If QoS is free, users will ask for bestAs result, wasted resourcesSolution?: Design protocols that discourage wasteAttempt:Voice: Low delay, larger lossData: Larger delay, small loss[E.g., differentiated RED with priority …]Shortcoming: Can cheat with FEC for dataUCBMechanisms (continued)DiffServTypically three classes:Expedited Forwarding (Low lagency, e.g., VoIP)Assured Forwarding (Guaranteed rate) Best EffortMPLSTypically long-term SLAsProtection switching is possibleTraffic Engineering to “optimize” networkUCBMechanisms (continued)Proposal:Overlay NetworkNetwork domains implement AF or MPLSQoS Boxes implementClassificationPolicingPricingQoS Transport (e.g., Vegas +)UCBPricingFlat Fee: $30.00/monthPros: Simple, predictable, boundedCons: Wasteful (cannot provide 10Mbps on demand)Usage-Based: $0.01/MbytePro: Encourages rational useCons: Unpredictable (can learn), risky (can cap), requires sophisticationCongestion-Based: time-of-day, spot pricePro: Most rational, leads to best utilizationCons: Sophisticated (requires software agents)Mechanisms?Heavy infrastructure
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