Patent ID: 8264955

Claim:
A computer-implemented method for determining failure recovery information, given a source node, a destination node, and a shared risk group failure on a next hop from the source node to the destination node, the computer-implemented method comprising: a) accepting a graph representing network topology information including the source node and the destination node; b) determining an exit node which is able to reach the destination node using a route which does not include the source node, by 1) determining a shortest path from the source node to the destination node avoiding any link belonging to the shared risk group failure, 2) for each node of the determined shortest path, except for the source node, A) determining if a path from the source node to the node of the determined shortest path under consideration is the shortest path between the source node and the node of the determined shortest path under consideration using any link in the network topology, even those links belonging to the shared risk group failure, B) if it is determined that the path from the source node to the node of the determined shortest path under consideration is the shortest path using any link in the network topology, even those links belonging to the shared risk group failure, then processing a next node of the determined shortest path by act (b)(2), otherwise, if it is determined that the path from the source node of the determined to the node shortest path, under consideration is not the shortest path using any link in the network topology, even those links belonging to the shared risk group failure, then setting the node of the determined shortest path, previously under consideration as the exit node; and c) storing, at the source node and in association with the shared risk group failure, both (1) a network address associated with the exit node and (2) an alternative output port of the source node using the shortest path from the source node to the exit node that does not include the shared risk group failure.