breaking the single-path barrier brad smith jack baskin soe research review day 10/20/2011

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Breaking the Single- Path Barrier Brad Smith Jack Baskin SoE Research Review Day 10/20/2011

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Breaking the Single-Path Barrier

Brad SmithJack Baskin SoE Research Review Day

10/20/2011

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Outline

• Research• Corporate Partnership• Open Source Network Lab

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The Internet is Single-Path

• Compute best path per destination• Destination-based (“hop-by-hop”) forwarding• 2 problems– Quality-of-Service– Congestion

S

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Problem – Quality-of-Service

• Requires multiple paths per destination• Example – 2 paths

• 2Mbps, 200ms• 100Kbps, 20ms

• Depends on application!– Video streaming– Voice over IP (VoIP)

b/w = 100Kbpslatency = 20ms

b/w = 2Mbpslatency = 200ms

Next hop for D?S

a

b

D

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Problem – Congestion

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Strong tendency for paths to share links…

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Previous Work

• Circuit switch – special path per flow• Solve part of the problem– Congestion – only need a small number (≤ 4)– Minimum delay– Partial solutions - disjoint widest and shortest

• In practice - over-provision a single path• Challenge – what are enough paths?

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Best Set of Paths• Paths as points in multi-dimensional space• Some paths are “better” than others• Best set of paths are those with none better• Paths that provide the full range of performance

100Kbps, 20ms100Kbps, 20ms 100Kbps, 20ms

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Using the Best Set of Paths

• Assign flows to paths that satisfy QoS• In general, there is more than one…• …choose one that minimizes congestion

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100Kbps, 20ms

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Simulations

• Generate random networks• Compute routing tables at all nodes– Total bandwidth– Delay

• Generate random stream of flows• Use oracle to assign flows to paths– Satisfies QoS– Has bandwidth

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Simulations (cont)

• Measure Call Acceptance Ratio– % flow requests successfully routed

• Across range of networks– Size – number of vertices– Connectivity – average degree (# neighbors)

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CAR: 350 Vertices, Degree 32

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CAR: 350 Vertices, Degree 16

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CAR: 350 Vertices, Degree 4

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• Converge when lightly loaded and over-loaded

• Multipath does better in-between

• Fewer resources poorer and less distinct performance

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Target CAR Flow Rate

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95%

600

Load supported by given infrastructure & routing architecture.

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95% CAR Rate: Degree 32

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Multipath provides dramatic capacity increase with same infrastructure.

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MP @ 95% CAR Rate – # Vertices

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Solid gains with increasing infrastructure.

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Ratio MP:SP 95% CAR – # Vertices

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4 to 11x gains… with opportunities for improvement(!).

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From 1 to many layers…

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Future Work

• Routing protocols (path computation)– Link state– Distance vector

• Congestion management (path selection)– Routing– Network feedback

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Thank you!