UCB Implementing QoS Jean Walrand EECS

UCB 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

UCB 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

UCB What? (continued) Latency: Upper bound: T  D max [e.g., conference => D max  200ms] Jitter: T max – T min  Jitter [Playback buffer => CBR]

UCB 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]

UCB Where? End-to-end Edge-to -edge Edge-to -edge

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

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

UCB 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.

UCB 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

UCB Mechanisms (continued) Incentive-Compatible Protocols Problem: If QoS is free, users will ask for best As 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

UCB 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

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

UCB 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?