Enforcing convergence in inter-domain routing

The stable-paths problem is an abstraction of the basic functionality of the Internet´s BGP (border gateway protocol) routing protocol. This abstraction has received considerable attention, due to the instabilities observed in BGP. In this abstraction, each node informs its neighboring nodes of its current path to the destination node. From the paths received from its neighbors, each node chooses the best path according to some locally chosen routing policy. However, since routing policies are chosen locally, conflicts may occur between nodes, resulting in unstable behavior. Current solutions either require expensive path histories, or prevent nodes from locally choosing their routing policy. We present a solution with small overhead, and furthermore, each node has the freedom to choose any routing policy. However, to avoid instabilities, the possibility of divergence is measured using an efficient cost metric exchanged between nodes. If the cost metric indicates that divergence is occurring, steps are taken to ensure convergence.