On inferring autonomous system relationships in the Internet
Authors:	L. Gao
Published:	Proc. IEEE Global Internet Symposium, 2000
URL:	http://www-unix.ecs.umass.edu/~lgao/ton.ps
Entry Date:	2003-6-12
Abstract:	The Internet consists of rapidly increasing number of hosts interconnected by constantly evolving networks of links and routers. Interdomain routing in the Internet is coordinated by the Border Gateway Protocol (BGP). BGP allows each autonomous system (AS) to choose its own administrative policy in selecting routes and propagating reachability information to others. These routing policies are constrained by the contractual commercial agreements between administrative domains. For example, an AS sets its policy so that it does not provide transit services between its providers. Such policies imply that AS relationships are an important aspect of Internet structure. We propose an augmented AS graph representation that classifies AS relationships into customer-provider, peering, and sibling relationships. We classify the types of routes that can appear in BGP routing tables based on the relationships between the ASes in the path and present heuristic algorithms that infer AS relationships from BGP routing tables. The algorithms are tested on publicly available BGP routing tables. We verify our inference results with AT&T internal information on its relationship with neighboring ASes. As much as 99.1% of our inference results are con rmed by the AT&T internal information. We also verify our inferred sibling relationships with the information acquired from the WHOIS lookup service [1]. More than half of our inferred sibling-to-sibling relationships are confirmed by the WHOIS lookup service. To the best of our knowledge, there has been no publicly available information about AS relationships and this is the first attempt in understanding and inferring AS relationships in the Internet. We show evidence that some routing table entries stem from router misconfigurations.
Results:	Presents heuristic algorithms that infer an augmented AS graph from BGP tables. The graph classifies AS relationships into customer-provider, peering, and sibling relationships. Out of connected AS pairs seen from RouteViews, classifies more than 90.5% into provider-customer relationships, less than 1.5% into sibling relationships, and less than 8% into peering relationships. Before tuning a crucial parameter, 96.5% of inferred relationships between AT&T and its neighbouring ASes (3.32% of RouteViews edges) are confirmed by AT&T internal information. 100% of inferred customers were confirmed, 77.4% of inferred peers were confirmed and 25% of inferred siblings were confirmed. Of the AT&T neighbours not seen (20% of AT&T neighbours), 95.6% were customers and the remainder peers. Note that AT&T has no providers. After tuning a crucial parameter, 99.1% of inferred relationships between AT&T and its neighbouring ASes are confirmed by AT&T internal information. 100% of inferred peers are now confirmed. More than 50% of inferred sibling pairs can be confirmed by data from the WHOIS lookup service.
Datasets:	BGP routing tables from RouteViews of 1999/9/27, 2000/1/2 and 2000/3/9. AT&T internal information of 2000/3/9. WHOIS lookup service (2000/1/2?).
References:	G. Huston, "Interconnection, peering and settlements - Part I," in Internet Protocol Journal, March 1999. G. Huston, "Interconnection, peering and settlements - Part II," in Internet Protocol Journal, June 1999.