1. Next steps in interdomain routing research (why measurements are not enough to decide about it) Steve Uhlig Université catholique de Louvain, Belgium suh@info.ucl.ac.be suh@info.ucl.ac.be

2. Internet-wide BGP behavior -Claim: BGP convergence can be slow [Labovitz et al. SIGCOMM’98&00] -Causes of routing dynamics: network engineering, flapping links, traffic engineering, misconfigurations,... -Causes of “slow” BGP convergence: Internet size, CPU load, BGP timers, route flap damping [Agarwal et al. PAM’04, Feldman et al. PAM’04] We don’t really know how well BGP performs

3. AS-wide BGP behavior -Impact of eBGP on traffic in tier-1 [Agrawal et al. SIGMETRICS’05]: not much dynamics inside AS due to external dynamics -Dynamics of hot-potato routing [Teixeira et al. SIGMETRICS’04] and impact on traffic [Teixeira et al. PAM’04]: high sensitivity of inside AS due to routing AS routing behavior depends on chosen AS and measured period [Teixeira et al. CCR 2005]

4. Inherent limitations of measurements -Even multiple vantage points give poor view of what’s going on [Feldmann et al. SIGCOMM’04] -Locating instabilities is hard, finding out what happened even harder -Studying individual ASes does not help much quantifying AS-wide routing dynamics -Studying interactions between ASes is one next step towards understanding Internet-wide BGP behavior (mentioned by Christophe already)

5. Inherent limitations of measurements -Can measurements alone help us decide whether interdomain routing should be changed? I don’t think so ! But... -Trying to make sense of all available BGP data might give some better idea if what is right or wrong with BGP -Thinking about new routing protocols (HLP, metarouting) also helps understand what are the alternatives to BGP

6. Building models to go beyond measurements limitations -Building models of Internet route propagation can help understand what matters to explain what we see (next step) -But simply reproducing AS paths is hard [M ü hlbauer et al. SIGCOMM ’ 06] -How do you deal with: -What is a policy? -What is a routing domain?

7. Building models to go beyond measurements limitations -Building models of Internet requires reverse- engineering the Internet! -What is the right granularity for: -Topology: ASes, routing domains, and routers -Policies: multiple peerings, filtering performed on peerings -Granularity of Internet model will depend on what you want to do with it.