Compact Routing on the Internet AS-Graph Stephen Strowes, - - PowerPoint PPT Presentation

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Compact Routing on the Internet AS-Graph Stephen Strowes, - - PowerPoint PPT Presentation

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Compact Routing on the Internet AS-Graph Stephen Strowes, University of Glasgow Graham Mooney, Cisco Systems Ltd. Colin Perkins, University of Glasgow 15 April 2011 Stephen Strowes, Global Internet 2011 Context Previous work:

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15 April 2011 Stephen Strowes, Global Internet 2011

  • Compact Routing
  • n the Internet
  • AS-Graph

Stephen Strowes, University of Glasgow Graham Mooney, Cisco Systems Ltd.

  • Colin Perkins, University of Glasgow
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15 April 2011 Stephen Strowes, Global Internet 2011

Context

Previous work:

Compact routing has shown promise for reducing forwarding state Previous work has evaluated synthetic “Internet- like” graphs

We use Internet topologies spanning 14 years

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15 April 2011 Stephen Strowes, Global Internet 2011

Compact routing?

Shortest-path routing:

Space: linear space Stretch: 1

Compact routing:

Space: sublinear space Stretch: 3

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15 April 2011 Stephen Strowes, Global Internet 2011

Previous work showed actual performance to be much closer to stretch-1

(on synthetic graphs at least)

We perform systematic experimental analysis

  • f two algorithms on Internet topologies

Stretch-3 sounds bad!

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15 April 2011 Stephen Strowes, Global Internet 2011

Overview

Two compact routing algorithms:

Thorup-Zwick (TZ) Brady-Cowen (BC)

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Overview: Thorup-Zwick

Routes via landmark nodes Defines forwarding entries using proximity to landmarks Nodes forward packets destination's landmark if destination not in local forwarding table

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TZ Asymmetry

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Overview: Brady-Cowen

Builds a primary spanning tree Then, builds additional, smaller spanning trees

  • n the periphery

Uses a distance labelling to select, at source, best tree to forward packets to desination

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Experimental Methodology

Generate AS topologies

Route Views BGP tables from 1997 through 2010

Run TZ & BC algorithms on all graphs to generate appropriate node labels/landmarks Determine path lengths

TZ: Simulate forwarding from all nodes to 1% (random) of rest of network, and back BC: Deterministic, and known after pre-computation

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Results

In the paper, we evaluate:

Tweaks/parameters for each algorithm Multiplicative path stretch Additive path stretch Forwarding table sizes TZ landmark selection frequency and distribution of landmark set sizes

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Results: TZ, multiplicative stretch

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Results: TZ, additive stretch

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Results: BC multiplicative stretch

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Results: BC, additive stretch

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Table sizes

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TZ Table sizes

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TZ landmark selection

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Conclusions

Experimental validation of:

… strong performance on Internet graphs … consistent performance over long periods of time

Insight into why the TZ algorithm performs well

  • n this type of graph
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15 April 2011 Stephen Strowes, Global Internet 2011

Future Work

There is scope for further analysis how a decentralised protocol based on the TZ algorithm behaves in a dynamic network … and how this works at the router level rather than the AS level

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  • Questions?
  • Stephen Strowes
  • sds@dcs.gla.ac.uk