Establishment of survivable connections in WDM networks using partial path protection

As a generalization of the traditional path protection scheme in WDM networks where a backup path is needed for each active path, the partial path protection scheme uses a collection of backup paths to protect an active path, where each backup path in the collection protects one or more links on the active path such that every link on the active path is protected by one of the backup paths. While there is no known polynomial time algorithm for computing an active path and a corresponding backup path using the path protection scheme for a source-destination node pair, we show that an active path and a corresponding collection of backup paths using the partial path protection scheme can be computed in polynomial time, whenever they exist, under each of the following two network models: (a) dedicated protection in WDM networks without wavelength converters; and (b) shared protection in WDM networks without wavelength converters. Under each of the two models, we prove, that for any given source s and destination d in the network, if one candidate active path connecting s and d is protectable using partial path protection, then any candidate active path connecting s and d is also protectable using partial path protection. This fundamental property leads to efficient shortest active path algorithms that can find an active path and its corresponding partial path protections whenever they exist. Simulation results show that shared partial path protection outperforms shared path protection in terms of blocking probability.