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Implementing QoS

Implementing QoS. Jean Walrand EECS. Outline. What? Bandwidth, Delay Where? End-to-End, Edge-to-Edge, Edge-to-End, Overlay Mechanisms Access Control Packet Marking Vegas Incentive-Compatible Protocols DiffServ, MPLS Pricing Flat, Usage, Congestion. What?. Throughput: R Mbps

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Implementing QoS

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  1. Implementing QoS Jean WalrandEECS

  2. Outline • What? • Bandwidth, Delay • Where? • End-to-End, Edge-to-Edge, Edge-to-End, Overlay • Mechanisms • Access Control • Packet Marking • Vegas • Incentive-Compatible Protocols • DiffServ, MPLS • Pricing • Flat, Usage, Congestion

  3. What? • Throughput: R Mbps • Flow: e.g., TCP connection • Pipe: e.g., (IP source, IP destination) • Possibly, class (e.g., VoIP) • Hose: Aggregate rate out of port • Timescale • 1 Mbps over every ms • 1 Mbps over every second

  4. What? (continued) • Latency: • Upper bound: T  Dmax[e.g., conference => Dmax 200ms] • Jitter: Tmax – Tmin Jitter [Playback buffer => CBR]

  5. What? (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]

  6. Edge-to -edge Edge-to -edge End-to-end Where?

  7. Overlay Network = QoS box = edge-to-edge with QoS .. Where? (continued)

  8. Mechanisms • Access Control • Example: MAN R 1 Gbps (bi-dir) Police R to 1 Gbps/N => Guaranteed

  9. Mechanisms (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.

  10. Mechanisms (continued) • Vegas + Window = rate x Prop + backlog Try to maintain a fixed backlog Equal backlogs => Equal throughputs (B. Davie) Extension to multiple bottleneck case (J. Mo) Difficulty: Not compatible with Reno

  11. Mechanisms (continued) • Incentive-Compatible Protocols • Problem: If QoS is free, users will ask for bestAs result, wasted resources • Solution?: Design protocols that discourage waste • Attempt: • Voice: Low delay, larger loss • Data: Larger delay, small loss • [E.g., differentiated RED with priority …] • Shortcoming: Can cheat with FEC for data

  12. Mechanisms (continued) • DiffServ • Typically three classes: • Expedited Forwarding (Low lagency, e.g., VoIP) • Assured Forwarding (Guaranteed rate) • Best Effort • MPLS • Typically long-term SLAs • Protection switching is possible • Traffic Engineering to “optimize” network

  13. Mechanisms (continued) • Proposal: • Overlay Network • Network domains implement AF or MPLS • QoS Boxes implement • Classification • Policing • Pricing • QoS Transport (e.g., Vegas +)

  14. Pricing • Flat Fee: $30.00/month • Pros: Simple, predictable, bounded • Cons: Wasteful (cannot provide 10Mbps on demand) • Usage-Based: $0.01/Mbyte • Pro: Encourages rational use • Cons: Unpredictable (can learn), risky (can cap), requires sophistication • Congestion-Based: time-of-day, spot price • Pro: Most rational, leads to best utilization • Cons: Sophisticated (requires software agents) • Mechanisms? • Heavy infrastructure necessary?

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