Supplementing Non-Simple p-Cycles with Preconfigured Lines

This paper considers link based protection where backup capacity is preconfigured into various patterns. When the amount of backup capacity available on a link is constrained, the choice of patterns under consideration can determine if a given network is protectable. This paper gives an ILP that can be used in calculating preconfigurations, even when p-Cycles with p-lines or non-simple p-Cycles alone may not be able to. This ILP includes constraints that will cause backup capacity to be distributed in a somewhat even fashion when possible. When considering networks with dynamic traffic, this may offer the advantage of lower blocking probability over schemes that concentrate backup capacity on a few links. The advantage is demonstrated by a simulation of NSFnet comparing blocking probability of a distribution computed by this ILP vs. a Hamiltonian p-Cycle which is a capacity optimal way to protect the network.