On the incompleteness of the AS-level graph: a novel methodology for BGP route collector placement

In the last decade many studies have used the Internet AS-level topology to perform several analyses, from discovering its graph properties to assessing its impact on the effectiveness of worm-containment strategies. Yet, the BGP data typically used to reveal the topologies are far from being complete. Our contribution is three-fold. Firstly, we analyse BGP data currently gathered by RouteViews, RIS and PCH route collectors, and investigate the reasons for its incompleteness. We found that large areas of the Internet are not properly captured due to the geographic placement of the current route collector feeders and due to BGP filters, such as BGP export policies and BGP decision processes. Secondly, we propose a methodology to select the optimal number of ASes that should join a route collector project to obtain a view of the Internet AS level topology closer to reality. We applied this methodology to the global AS-level topology and to five regional AS-level topologies, highlighting that the particular characteristics of the Internet at a regional level cannot be ignored during this process. Thirdly, we provide a characterization of the ASes that we found to be part of at least one optimal solution set. By analysing these ASes we found that the current route collector infrastructure is rarely connected to them, highlighting that much more effort should be made in devising a route collector infrastructure that ideally would be able to capture a complete view of the Internet.