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Breaking the Single-Path Barrier. Brad Smith Jack Baskin SoE Research Review Day 10/20/2011. Outline. Research Corporate Partnership Open Source Network Lab. The Internet is Single-Path. Compute best path per destination Destination-based (“hop-by-hop”) forwarding 2 problems
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Breaking the Single-Path Barrier Brad Smith Jack Baskin SoE Research Review Day 10/20/2011
Outline • Research • Corporate Partnership • Open Source Network Lab Jack Baskin SoE Research Review Day
The Internet is Single-Path • Compute best path per destination • Destination-based (“hop-by-hop”) forwarding • 2 problems • Quality-of-Service • Congestion S Jack Baskin SoE Research Review Day
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 = 2Mbps latency = 200ms a Next hop for D? D S b b/w = 100Kbps latency = 20ms Jack Baskin SoE Research Review Day
Problem – Congestion 32 32 45 32 16 16 32 7 7 7 4 7 16 18 16 4 4 45 18 18 45 7 4 7 16 16 18 7 7 16 32 16 32 32 32 45 Strong tendency for paths to share links… Jack Baskin SoE Research Review Day
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? Jack Baskin SoE Research Review Day
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, 20ms 100Kbps, 20ms 100Kbps, 20ms Jack Baskin SoE Research Review Day
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 100Kbps, 20ms Jack Baskin SoE Research Review Day
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 Jack Baskin SoE Research Review Day
Simulations (cont) • Measure Call Acceptance Ratio • % flow requests successfully routed • Across range of networks • Size – number of vertices • Connectivity – average degree (# neighbors) Jack Baskin SoE Research Review Day
CAR: 350 Vertices, Degree 32 Jack Baskin SoE Research Review Day
CAR: 350 Vertices, Degree 16 Jack Baskin SoE Research Review Day
CAR: 350 Vertices, Degree 4 Jack Baskin SoE Research Review Day
Converge when lightly loaded and over-loaded • Multipath does better in-between • Fewer resources poorer and less distinct performance Jack Baskin SoE Research Review Day
Target CAR Flow Rate 95% 600 Load supported by given infrastructure & routing architecture. Jack Baskin SoE Research Review Day
95% CAR Rate: Degree 32 Multipath provides dramatic capacity increase with same infrastructure. Jack Baskin SoE Research Review Day
MP @ 95% CAR Rate – # Vertices Solid gains with increasing infrastructure. Jack Baskin SoE Research Review Day
Ratio MP:SP 95% CAR – # Vertices 4 to 11x gains… with opportunities for improvement(!). Jack Baskin SoE Research Review Day
From 1 to many layers… Jack Baskin SoE Research Review Day
Future Work • Routing protocols (path computation) • Link state • Distance vector • Congestion management (path selection) • Routing • Network feedback Jack Baskin SoE Research Review Day
