A multicast protection algorithm for optical WDM networks

Supporting multicast applications has drawn increased attention in the development of WDM based optical networks. To provide a high level of availability in the face of node or link failure for multicast traffic, pre-assigned spare capacity in the networks is needed. This paper studies the problem of constructing a minimum-cost, two-connected subgraph, satisfying the wavelength conversion constraint, for a multicast request in a WDM network. It is known that the problem of finding the minimum cost of a two-connected graph is NP-hard. We prove that the problem of the optimal wavelength assignment for a given graph is also NP-hard. We propose a routing and wavelength assignment heuristic which aims not only to minimize the cost of the subgraph but also to reduce the number of wavelength conversions in the networks. Simulation experiments show that our proposed algorithm achieves performance close to the optimal solution when the average number of wavelengths in the networks is not low.