Characterisation of AS-level path deviations and multipath in Internet routing

Although significant efforts have been devoted in the literature to measurements of the Internet topology, little attention has been given to the qualification of routing deviations and multipath dynamics at the Autonomous System (AS) routing level. We observed Internet AS-level routes toward thousands of destinations for several weeks between 2009 and 2010 to have a better understanding of these phenomena, nowadays. Using a modified form of traceroute at the state of the art called paris-traceroute, able to detect load-balancing, we sampled thousands of AS-level routes for several weeks. By an extensive analysis, we found that between 15% and 17% of the monitored destinations experiences AS-path deviations, and that load balancing at the AS-level (i.e., forms of BGP multipath) is not widespread at all, and, when frequently used, it is limited to a sort of AS confederation.