Towards capturing representative AS-level Internet topologies

Recent studies on AS-level Internet connectivity have attracted considerable attention. These studies have exclusively relied on BGP data from the Oregon route-views [University of Oregon Route Views Project, http:// www.routeviews.org] to derive some unexpected and intriguing results. The Oregon route-views data sets reflect AS peering relationships, as reported by BGP, seen from a handful of vantage points in the global Internet. The possibility that these data sets may provide only a very sketchy picture of the complete inter-AS connectivity of the Internet has received little scrutiny. By augmenting the Oregon route-views data with BGP summary information from a large number of Internet Looking Glass sites and with routing policy information from Internet Routing Registry (IRR) databases, we find that (1) a significant number of existing AS peering relationships remain hidden from most BGP routing tables, (2) the AS peering relationships with tier-1 Ass are in general more easily observed than those with nontier-1 Ass, and (3) there are at least about 40% more AS peering relationships in the Internet than commonly-used BGP-derived AS maps reveal (but only about 4% more ASs). These findings point out the need for continuously questioning the applicability and completeness of data sets at hand when establishing the generality of any particular Internet-specific observation and for assessing its (in)sensitivity to deficiencies in the measurements. (C) 2003 Elsevier B.V. All rights reserved.