Estimating the AS path to the source and destination addresses for each packet requires a core routing table as close to the measurement location as possible. We used the routing information advertised from the peer of the U.O. Route Views server that was closest to packet sampling point. This routing table included 49,074 routes originating from 3526 different ASes. In the histograms below, we plot the sum of the source and destination AS path lengths as the estimated number of ASes traversed.
Note that although we estimate AS path lengths using a methodology quite different from that used in http://moat.nlanr.net/ASPL (no longer available), the results are strikingly similar. The previous work was based exclusively on topological information derived from BGP routing tables. This new result confirms the previously predicted result with an analysis based on actual Internet traffic flows rather than the static topology of routing table snapshots
references1. [Meyer97], University of Oregon Route Views Project, http://www.routeviews.org, Advanced Network Technology Center, David Meyer (now at Cisco Systems).
Thanks to Hans-Werner Braun and NLANR/MOAT for supplying the packet trace data, and David Meyer for maintaining the Route Views project. Sean McCreary and kc claffy, 5/25/98