Collateral Damage in the Last Big Internet Storm

The Internet is in a transition phase. Migrating to IPv6 is currently the centre of many studies, since the IPv4 address space exhaustion is starting to be noticeable by facts like the slowdown in the growth of the IPv4 routing table. Another less advertised but equally important challenge for the Internet is the exhaustion of the current 16 bit Autonomous System Numbers. The solution adopted by the IETF has to introduce 32-bit Autonomous System Numbers in order to get a reasonable breathing space. This implies another transition process, which is less public because it has no direct impact on the end users. But this process is not being as smooth as many people would desire and is at the root of several routing storms, which have lately shaken the Internet. This paper analyses the last Internet routing storm, which occurred on August, 2009 from a location which is geographically and topographically distant from the storm's epicentre. The data captured by RIPE'S BGP probes at the London Internet Exchange are decomposed for this study and the traffic profiles of the different probes is analysed separately. This study looks at traces produced by BGP-4 traffic engineering techniques based on changes in the ASPATH attribute and discovers one probe which mainly collected traffic which was induced by a change in the ASPATH prepending behaviour of a neighbouring Autonomous System.