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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical 2006.06.05 NANOG-NOTES interdomain routng via Wiser, Ratul Mahjan
2006.06.05 A simple coordination mechasims for interdomain routing [slides are at: http://www.nanog.org/mtg-0606/pdf/ratul-mahajan.pdf Ratul Mahjan David Wetherall Tom Anderson University of Washington now @ Microsoft Research the nature of internet routing within a contractual framework, ISPs select routes that are best for themselves. Potential downsides higher BW provisioning requires manual tweaking to fix egregious problems inefficient end-to-end paths An alternative approach: coordinated routing ISPs have joint control path selection is based on the preferences of both ISPs Potential benefits lower BW provisioning no egregious cases that need manual tweaking efficient end-to-end paths basis for interdomain QoS Existing mechanisms cannot implement coordinated routing route optimization boxes help (stub) ISPs pick better routs from those available MEDS implement receiver's preferences. Cannot create better paths that don't already show up in the routing table. What makes for a good coordination mechanism? MEDS have some nice properties ISPs can express their own metrics ISPs are not required to disclose sensitive info lightweight requires only pairwise contracts Provides joint control and benefits all ISPs. Our solution: Wiser operates in a lowest-cost routing framework downstream ISPs advertise their cost upstream ISPs select paths based on both their own and received costs. Problems with vanilla lowest-cost routing ISP costs are incomparable Can be easily gamed When you bring incomparable costs together, the ISPs that use higher costs win out. Cost normalization Normalize costs such that both ISPs have "equal say" Normalize such that sum of costs is the same. Makes the system harder to game. Bounds on cost usage Downstreams log cost usage of the upstream ISPs Compute the ratio of avg. cost of paths used and announced Contractually stipulate a bound on the ratio. Similar to existing ratio requirements. Wiser in action Announce costs in routing messages. normalization occurs between ISP pairs. Example results using major ISP topologies for experiments Wiser provides better control under link failure. Wiser produces shorter path lengths Implementation XORP prototype Simple, backward-compatible extensions to BGP embed costs in non-transitive BGP communities border routers jointly compute normalization factors and log cost usage a slightly modified BGP decision process Benefits even the first two ISPs that deploy it. Summary Wiser is a simple mechanism to coordinate interdomain routing may lower provisioning, reduce manual tweaking, produce more efficient paths and help with interdomain QoS Feedback: [email protected] http://www.cs.washington.edu/research/networking/negotiation/ Danny McPhereson: Q: how do you normalize across multiple ISPs? A: routing advertisements happen on the sum of the costs announced from me to you, and from you to me. He derived it from different values in his experimentation; utilization and latency in general. Q: Randy Bush: Whatever metrics are, you just normalize by summing them up. But Danny notes if you have multiple ISPs, how do you normalize them together? Q: Danny: where was the 20ms of control plane savings seen that he claimed in slide 11? A: That was based on default ISP policy, prefer customers over peers, etc. So the delay was control plane plus data plane; it wasn't control plane alone. He based it on the old rockefuel equation. Randy Bush: vendors--this is cool stuff, open your ears. Break time now. |