Reasoning on BGP routing filters using tree automata

The Border Gateway Protocol (BGP) is the protocol used to distribute Internet routes between different organizations. BGP routing policies are very important because they enable organizations to enforce their business relationships by controlling route redistribution and route selection. In this paper, we investigate the semantic of BGP policies. We aim to determine whether two policies are equivalent, that is, if given the same set of incoming routes, they will generate the same set of outgoing routes. We show how this problem can be solved using the tree automata theory and describe several optimizations. We also propose a prototype implementing this approach. The experimental results are very promising. They show the efficiency of our approach and the interest of using the tree automata theory in the context of BGP routing policies.