Fault recovery for guaranteed performance communications connections

Fault recovery techniques must be reexamined in the light of the new guaranteed performance services that high-speed packet/cell switched networks will support. We investigate the rerouting of guaranteed performance service connections on the occurrence of link faults, focusing on the aspects of route selection and establishment in the network. We model the rerouting mechanism in terms of three orthogonal components: locus of reroute, reroute timing, and retry model, and explore the effect of variations in each component on the recovery process, in the presence of single- and multiple-link faults in the network. Our schemes are simulated on a cross section of network workloads, and compared using several performance criteria quantifying speed and efficacy. Our results show that global (or end-to-end) rerouting performs well as a locus of reroute selection mechanism, and that randomization is a powerful technique to determine reroute timing. We find that retrying along a new path is less effective than rerouting at a different time, and use this result to develop a new delayed retry technique. Randomization in the retry mechanism obviates the need for randomization in the initial reroute timing, so global rerouting with immediate timing and randomized retries performs well for all our performance criteria in a spectrum of network topologies and workloads for both single and multiple failures. We observe that this combination moves most of the complexity of rerouting to the edge of the network, leading to a very lightweight recovery model