Partition inequalities for capacitated survivable network design based on directed p-cycles

We study the design of capacitated survivable networks using directed p-cycles. A p-cycle is a cycle with at least three arcs, used for rerouting disrupted flow during edge failures. Survivability of the network is accomplished by reserving sufficient slack on directed p-cycles so that if an edge fails, its flow can be rerouted along the p-cycles. We describe a model for designing capacitated survivable networks based on directed p-cycles. We motivate this model by comparing it with other means of ensuring survivability, and present a mixed-integer programming formulation for it. We derive valid inequalities for the model based on the minimum capacity requirement between partitions of the nodes and give facet conditions for them. We discuss the separation for these inequalities and present results of computational experiments for testing their effectiveness as cutting planes when incorporated in a branch-and-cut algorithm. Our experiments show that the proposed inequalities reduce the computational effort significantly.