Automatic Inference of BGP Location Communities

The Border Gateway Protocol (BGP) orchestrates Internet communications between and inside Autonomous Systems. BGP's flexibility allows operators to express complex policies and deploy advanced traffic engineering systems. A key mechanism to provide this flexibility is tagging route announcements with BGP communities, which have arbitrary, operator-defined semantics, to pass information or requests from router to router. Typical uses of BGP communities include attaching metadata to route announcements, such as where a route was learned or whether it was received from a customer, and controlling route propagation, for example to steer traffic to preferred paths or blackhole DDoS traffic. However, there is no standard for specifying the semantics nor a centralized repository that catalogs the meaning of BGP communities. The lack of standards and central repositories complicates the use of communities by the operator and research communities. In this paper, we present a set of techniques to infer the semantics of BGP communities from public BGP data. Our techniques infer communities related to the entities or locations traversed by a route by correlating communities with AS paths. We also propose a set of heuristics to filter incorrect inferences introduced by misbehaving networks, sharing of BGP communities among sibling autonomous systems, and inconsistent BGP dumps. We apply our techniques to billions of routing records from public BGP collectors and make available a public database with more than 15 thousand location communities. Our comparison with manually-built databases shows our techniques provide high precision (up to 93%), better coverage (up to 81% recall), and dynamic updates, complementing operators' and researchers' abilities to reason about BGP community semantics.