(c) Anirban Banerjee, Winter 200 5, CS-240, 2/1/2005. 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. The Impact of Internet Policy and Topology on Delayed Routing convergence C. Labovitz, A. Ahuja, R.
Dec 20, 2015
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(c) Anirban Banerjee, Winter 2005, CS-240, 2/1/2005.
The Impact of Internet Policy and Topology on Delayed
Routing convergence
C. Labovitz, A. Ahuja, R. Wattenhofer and S. Venkatachary.
IEEE INFOCOM 2001.
Roadmap
The “Problem” The “Contribution” Motivation Background Testbed Experimental Results Conclusions Future Work
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.
Roadmap
The “Problem” The “Contribution” Motivation Background Testbed Experimental Results Conclusions Future Work
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.
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.
Roadmap
The “Problem” The “Contribution” Motivation Background Testbed Experimental Results Conclusions Future Work
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.
Roadmap
The “Problem” The “Contribution” Motivation Background Testbed Experimental Results Conclusions Future Work
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.
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}
Roadmap
The “Problem” The “Contribution” Motivation Background Testbed Experimental Results Conclusions Future Work
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.
Routing Policy
Most ISPs simply resort to trusting their peers. ! ! ! !
Roadmap
The “Problem” The “Contribution” Motivation Background Testbed Experimental Results Conclusions Future Work
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.
Experimental ResultsRoutes from ISP1
Experimental ResultsRoutes from ISP2
Experimental ResultsRoutes from ISP3
Experimental Results
Experimental Results
Roadmap
The “Problem” The “Contribution” Motivation Background Testbed Experimental Results Conclusions Future Work
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.
Roadmap
The “Problem” The “Contribution” Motivation Background Testbed Experimental Results Conclusions Future Work
Future Work
Evolve mechanism to handle “vagabond” paths.
Implement necessary changes to BGP in order to reduce convergence latencies.
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