1. BGP topics to be discussed in the next few weeks: –Excessive route update –Routing instability –BGP policy issues –BGP route slow convergence problem –Interaction between BGP/IGP and among BGP components –Anti-IP-spoofing with BGP –New EGP proposals

2. BGP Routing Stability of Popular Destinations Jennifer Rexford, Jia Wang, Zhen Xiao, and Yin Zhang

3. Some causes of BGP route changes: –Equipment failures. –Policy changes –Intra-domain topology changes Potential problems caused BGP route changes: One “event” triggers a long sequence of updates –CPU –Changing paths with traffic can cause congestion Transient loops Make it hard to direct (engineer) the traffic

4. What is the current situation: –A large fraction of prefixes have stable BGP routes –A small fraction of prefixes are responsible for the majority of Internet traffic –Are prefixes receiving a large volume of traffic more or less stable than prefixes receiving a lower volume of traffic? Intuitively, more traffic can cause more changes Popular sites have well managed multiple connections to the Internet.

5. How the study is done? –BGP routes and updates in RouteViews and RIPE NCC are publicly available –This study adds one monitor in the ATT backbone –The anomalies are removed: Burst updates due to router failure Redundant advertisements: –Multiple updates for the same route –Withdraw before announce –Updates or events An event can cause a lot of updates Routing stability is better reflected by events How to get events from updates? –Updates spaced close together in time are counted as one event –This may not be accurate.

6. Grouping events: 45seconds/75seconds

7. Event duration: mostly < 5 mins

8. A small number of prefixes are responsible for most updates events

9. Update event vs. traffic volume –Most traffic goes to a small number of prefixes

10. Update event vs. traffic volume –Prefixes responsible for most update events do not receive a lot of traffic

11. Explanations: –Unstable prefixes tend to be unpopular Unstable BGP routes make it different for other hosts to reach the destinations. They cannot be popular.

12. Popular prefixes do not experience many events

13. Top websites cause very few update events

14. Conclusion: –The majority of the update events are concentrated in a few prefixes that do not receive much traffic –Popular sites almost have no updates –Implications: suppressing updates mostly likely will not cause disruption of the Internet. Who are the prefixes that cause most of the updates? How long does the instability last? Can we do something about it?