Archive for July, 2010

IP-AS mappings

Wednesday, July 28th, 2010 by Amogh Dhamdhere

We have performed an analysis of the IP-AS mapping obtained from Routeviews/RIPE collectors.

A crucial step in various research efforts that study the Internet infrastructure is to map an IP address to the Autonomous System (AS) to which it is assigned. The most common approach to map IP addresses to ASes is by using BGP table dumps from public repositories such as Routeviews and RIPE. We assign “ownership” of an IP address to the AS that originates the longest BGP prefix that matches the IP address. Routeviews and RIPE, however, have multiple collectors, each of which peers with a diverse set of ASes. Consequently, the IP-AS mapping obtained by using the BGP table dump from one collector could be different from that obtained from a different collector. The obvious solution is to aggregate views from as many vantage points as possible to obtain the most complete IP-AS mapping possible. In practice, however, it is common to use data from just one or two collectors, as it greatly simplifies the process of collecting and pre-processing data. The goal of our analysis is to compare different collectors, in terms of the different metrics that we are interested in, viz. address space coverage, IP-AS mapping, unique ASes, unique prefixes, unique more specific prefixes, AS links, and AS paths. Further, we study the utility of adding data from more collectors, in terms of the resulting change in the aforementioned metrics. Finally, we compare the IP-AS mapping from Routeviews and RIPE tables with that obtained from Team Cymru’s whois service.