BGP AS Paths: Shorter Is Not Always Better

The Border Gateway Protocol (BGP) is the Internet's de facto routing protocol, responsible for exchanging reachability information between Autonomous Systems (ASes). As a policy-based protocol, BGP is implemented on the border routers of ASes. It is commonly assumed in research that routers withing ASes use the same BGP policies and AS paths for the same prefix. However, each border router seperately maintains multiple BGP sessions and selects the best route for a prefix by evaluating all learned routes.