Robust routing for minimum worst-case expected delay in unreliable networks

The authors consider the problem of finding a routing strategy that minimizes the worst-case expected delay from every source to a single destination in an unreliable network, given a constraint on the number of outgoing links at each node that can be inoperational at any point in time. Subject to this constraint, links can fail and recover arbitrarily often. A node having a packet to forward must choose a single link on which to transmit the packet, but does not know in advance which links will be inoperational during the transmission. If a transmission fails, the packet is retransmitted (not necessarily on the same link) after some fixed amount of time. It is shown that the optimal routing strategy is a stationary randomized strategy in which each node selects the forwarding link according to a fixed probability distribution. An efficient algorithm that computes an ε-optimal solution in O(|E|log(|V|/ε)) time, for any positive number ε, is presented