On inferring autonomous system relationships in the Internet

Interdomain routing in the Internet is coordinated by the border gateway protocol (BGP). BGP allows each autonomous system (AS) to choose its own policy in selecting routes and propagating reachability information to others. These routing policies are constrained by the contractual commercial agreements between administrative domains. Such policies imply that connectivity alone can not fully characterize the structural properties of the Internet. We propose an augmented AS graph representation that classifies AS relationships into customer-to-provider, peer-to-peer, and sibling to-sibling relationships. We classify the types of routes that can appear in BGP routing tables based on the relationships between the ASs 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 that contains dose to 1 million route entries. The algorithms infer that more than 90.5% of the connected AS pairs have customer-to-provider relationships, less than 1.5% of the connected AS pairs have sibling-to-sibling relationships, and less than 8% of the connected AS pairs have peer-to-peer relationships. We verify our inference results with AT&T internal information on its relationship with neighboring ASs. 99% of our inference results are confirmed by the AT&T internal information. We also verify our inferred sibling-to-sibling relationships with the information acquired from the WHOIS lookup service. More than half of our inferred sibling-to-sibling relationships are confirmed by the WHOIS lookup service. To the best of our knowledge this is the first attempt in understanding and inferring AS relationships in the Internet. We show evidence that some routing table entries stem from unusual AS relationships or router misconfiguration