Segment shared protection for survivable meshed WDM optical networks

In this paper, we investigate the protection design for survivable meshed WDM optical networks, and propose a novel heuristic algorithm, which is called segment shared protection (SSP), to completely protect the dual-link failures. For each connection request, first SSP computes a least-cost working path, second SSP divides the working path into several un-overlapped segment paths according to a parameter M, and finally SSP computes two least-cost and linkdisjoint backup paths for each segment path. If two segment paths do not traverse the same fiber links, then their corresponding backup paths can shared the common reserved backup wavelengths. When computing the paths, we suggest two dynamic link-cost functions to adjust the resource sharing degree according to the current state of the network, and then our routing algorithm, which computes the least-cost paths, has higher resource utilization ratio and lower blocking ratio than those routing algorithms that merely compute the shortest paths. We describe our scheme of dividing the segment path and the method of assigning the reserved backup wavelengths. We also study the procedure of the protection switching time, which had not been studied by previous algorithms, for the dual-link failures, and calculate the formulas of the protection switching time. Under dynamic traffic with different load, the simulation results show that: SSP provides 100% reliable protection for the dual-link failures; with respect to the previous algorithm, SSP, adds a valuable elasticity between the resource utilization and the protection switching time, and is able to perform higher resource utilization ratio, lower blocking ratio, and faster protection switching time. 2005 Elsevier B.V. All rights reserved. PACS: 42.79.Sz; 42.81.Uv