A Fast Re-Route Method

We present a method to find an alternate path, after a link failure, from a source node to a destination node, before the Interior Gateway Protocol (e.g., OSPF or IS-IS) has had a chance to reconverge in response to the failure. The target application is a small (up to tens of nodes) regional access subnetwork of a service provider's network, which is a typical access scale encountered in practice. We illustrate the method and prove that it will find a path if one exists.