Finding Routing Paths for Alternate Routing in All-Optical WDM Networks

An alternate routing algorithm requires a set of predetermined routing paths between each source-destination pair. To reduce the connection blocking probability, it is desirable that the predetermined routing paths between each source-destination pair be link-disjoint. The predetermined routing paths used in previous works on alternate routing are the -shortest link-disjoint paths in terms of hop count. The shared links among the -shortest link-disjoint paths between different source-destination pairs may cause high connection blocking probability. Thus, depending on the traffic requirements of all source-destination pairs, hop-count based -shortest link-disjoint paths may not be the best choice for the predetermined routing paths. This paper proposes a method to find a set of link-disjoint routing paths between each source-destination pair to be used by an alternate routing algorithm in order to reduce the connection blocking probability. The key idea is to find a set of link-disjoint routing paths based on the routing paths that are utilized by the optimal traffic pattern in the network. Then, for each source-destination pair, we select a set of link-disjoint routing paths from the routing paths that are utilized by the optimal traffic pattern such that the selected set of link-disjoint routing paths carries the most of the traffic between the source-destination pair. Simulations are performed to compare the performance of using the link-disjoint routing paths found by the proposed method as the predetermined routing paths and those of using the hop-count based -shortest link-disjoint paths and employing the routing paths found by the capacity-balanced alternate routing method proposed method by Ho and Mouftah (in 2002) as the predetermined routing paths. Our simulation results show that using the link-disjoint routing paths found by the proposed method yields significantly lower connection blocking probability than employing the hop-count based -shortest link-disjoint paths and using the routing paths found by the capacity-balanced alternate routing method (Ho and Mouftah, 2002).