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The Impact of Internet Policy and Topology on Delayed Routing convergence

This study investigates the problem of delayed routing convergence in the internet due to inter-domain path failures. The research demonstrates that the time for internet convergence depends on the length of backup paths and larger ISPs have faster convergence. The study also highlights the presence of "vagabond" paths and software errors in internet routes. The findings emphasize the need for mechanisms to handle these issues and reduce convergence latencies.

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The Impact of Internet Policy and Topology on Delayed Routing convergence

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  1. The Impact of Internet Policy and Topology on Delayed Routing convergence C. Labovitz, A. Ahuja, R. Wattenhofer and S. Venkatachary. IEEE INFOCOM 2001. (c) Anirban Banerjee, Winter 2005, CS-240, 2/1/2005.

  2. Roadmap • The “Problem” • The “Contribution” • Motivation • Background • Testbed • Experimental Results • Conclusions • Future Work

  3. The “Problem” • The internet lacks inter-domain path fail over. • How soon can convergence be expected when path(s) fail. • What is the effect of path failures on different ISPs, large and small.

  4. The “Problem” The “Contribution” Motivation Background Testbed Experimental Results Conclusions Future Work Roadmap

  5. The “Contribution” • Demonstrate that the time for end-to-end internet convergence depends on the length of the length of the longest possible back-up AS path between source and destination node. • Show clearly, larger ISPs have faster convergence latencies.

  6. The “Contribution”..more specifically • Time complexity of for internet fail-over convergence is upper bounded by 30n sec. • Show that, routes from customers of larger ISPs exhibit faster convergence. • Presence of “vagabond” paths, s/w errors. • Most default free Internet routes exhibit multiple alternate secondary paths.

  7. The “Problem” The “Contribution” Motivation Background Testbed Experimental Results Conclusions Future Work Roadmap

  8. Motivation • There is a relative lack of reliability in the internet vis-à-vis the PSTN network. • Multi-homed internet sites often experience long connectivity latencies after faults(s) occur.

  9. The “Problem” The “Contribution” Motivation Background Testbed Experimental Results Conclusions Future Work Roadmap

  10. Background • BGP, a path vector protocol, uses an ASPath sequence of intermediate ASs. • Uses this ASPath for loop detection and policy decisions. • Most vendor implementations of BGP fall back on the best path selection based on ASPath length after fault.

  11. Background..contd. • BGP includes a MinRouteAdver timer. • This provides a buffer between BGP updates and also allows for aggregation of routes containing common information. • T. Griffin and G. Wilfong, “An analysis of BGP convergence properties”, ACM SIGCOM, 1999. {possible to implement mutuall unsatisfiable policies in BGP} • L. Gao and J. Rexford,”Stable Internet Routing without Global Coordination”, ACM SIGMETRICS, 2000.{adherence to common policies guarantees convergence}

  12. The “Problem” The “Contribution” Motivation Background Testbed Experimental Results Conclusions Future Work Roadmap

  13. TestBed • Unix, probe machineswith peering sessions with more than 20 ISPs (geographically and topologically diverse). • Inject faults into more than 10 ISPs. • Software from MRT & IPMA projects, running on FreeBSD systems. • Observation spread over 6 months.

  14. Routing Policy Most ISPs simply resort to trusting their peers. ! ! ! !

  15. The “Problem” The “Contribution” Motivation Background Testbed Experimental Results Conclusions Future Work Roadmap

  16. Experimental Results • Effect of topology on Convergence • Analyzed routing topologies between more than 200 pair of ISPs. • Focus on MinRouteAdver Timers and length of ASPaths on convergence.

  17. Experimental Results Routes from ISP1

  18. Experimental Results Routes from ISP2

  19. Experimental Results Routes from ISP3

  20. Experimental Results

  21. Experimental Results

  22. The “Problem” The “Contribution” Motivation Background Testbed Experimental Results Conclusions Future Work Roadmap

  23. Conclusions • Shown conclusively that the internet currently lacks high levels of reliability and fault tolerance. • Current internet convergence latencies, upto 15 min. is very high. • Complexity of multi homed internet path fail over scales with the longest possible back up path for that route. • Customers sensitive to fail overs, should multi home to larger ISPs. • There remains a chasm in formulating nechanisms to handle “vagabond” paths.

  24. The “Problem” The “Contribution” Motivation Background Testbed Experimental Results Conclusions Future Work Roadmap

  25. Future Work • Evolve mechanism to handle “vagabond” paths. • Implement necessary changes to BGP in order to reduce convergence latencies.

  26. That’s all folks…. Comments : anirban@cs.ucr.edu

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