Transcript Implementing QoS

UCB
Implementing QoS
Jean Walrand
EECS
Outline
UCB
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What?
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Where?
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End-to-End, Edge-to-Edge, Edge-to-End, Overlay
Mechanisms
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Bandwidth, Delay
Access Control
Packet Marking
Vegas
Incentive-Compatible Protocols
DiffServ, MPLS
Pricing
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Flat, Usage, Congestion
What?
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Throughput: R Mbps
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Flow: e.g., TCP connection
Pipe: e.g., (IP source, IP destination)
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Possibly, class (e.g., VoIP)
Hose: Aggregate rate out of port
Timescale
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1 Mbps over every ms
1 Mbps over every second
What?
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(continued)
Latency:
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Upper bound: T  Dmax
[e.g., conference => Dmax  200ms]
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Jitter: Tmax – Tmin  Jitter
[Playback buffer => CBR]
What?
UCB
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(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]
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UCB
Where?
Edge-to
-edge
Edge-to
-edge
End-to-end
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Where?
(continued)
Overlay Network
= QoS box
= edge-to-edge with QoS ..
Mechanisms
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Access Control
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Example: MAN
R
1 Gbps
(bi-dir)
Police R to 1 Gbps/N => Guaranteed
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Mechanisms
Packet Marking
(continued)
(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.
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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
Mechanisms
UCB
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(continued)
Incentive-Compatible Protocols
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Problem: If QoS is free, users will ask for best
As result, wasted resources
Solution?: Design protocols that discourage waste
Attempt:
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Voice: Low delay, larger loss
Data: Larger delay, small loss
[E.g., differentiated RED with priority …]
Shortcoming: Can cheat with FEC for data
Mechanisms
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DiffServ
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Typically three classes:
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(continued)
Expedited Forwarding (Low lagency, e.g., VoIP)
Assured Forwarding (Guaranteed rate)
Best Effort
MPLS
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Typically long-term SLAs
Protection switching is possible
Traffic Engineering to “optimize” network
Mechanisms
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(continued)
Proposal:
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Overlay Network
Network domains implement AF or MPLS
QoS Boxes implement
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Classification
Policing
Pricing
QoS Transport (e.g., Vegas +)
Pricing
UCB
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Flat Fee: $30.00/month
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Usage-Based: $0.01/Mbyte
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Pro: Encourages rational use
Cons: Unpredictable (can learn), risky (can cap), requires
sophistication
Congestion-Based: time-of-day, spot price
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Pros: Simple, predictable, bounded
Cons: Wasteful (cannot provide 10Mbps on demand)
Pro: Most rational, leads to best utilization
Cons: Sophisticated (requires software agents)
Mechanisms?
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Heavy infrastructure necessary?