Single backup table schemes for shortest-path routing

We introduce a new recovery scheme that needs only one extra backup routing table for networks employing shortest-path routing. By precomputing this backup table, the network recovers from any single link failure immediately after the failure occurs. To compute the backup routing table for this scheme, we use an almost linear time algorithm to solve the {r,v}-problem, which is a variation of the best swap problem presented by Nardelli et al. We further show that the same solution can be computed in exactly linear time if the underlying graph is unweighted.