Impact Zone Analysis of p-Cycle

Pre-configured cycle (p-Cycle) method has been studied in literature extensively for optical network protection. A large p-cycle has high capacity efficiency and can protect a large number of nodes against the single link failure scenarios. All the links protected by such a p-cycle lose protection when the p-cycle is consumed to restore traffic after a failure. As the probability of multiple link failure is high for a large network, it also means that with higher probability, on the second failure, protection may not be there for the failed link. Thus, if the number of links protected by a p-cycle is large, it makes the network unprotected with high probability on the advent of the second failure. In this paper, we study the impact zone due to a first link failure in the various configurations of the p-cycles. The study gives insight into how to choose the p-cycle configuration to reduce the impact zone while using minimum spare capacity. We propose few methods and compare them to show how the impact zone analysis can be used to improve the fault tolerance in an optical network.