Survivability of multicast requests in mesh optical networks

The problem of provisioning survivable multicast requests in mesh optical networks is investigated in the current paper. In practice, these requests arrive in the network and stay for some time, holding resources of it. Therefore, some arcs may not have free wavelengths to be used, leading to a directed-graph network for the upcoming requests. A directed graph is defined as the one having both unidirectional and bidirectional connections between its nodes. However, all segment-based approaches outlined in the literature for provisioning survivable multicast requests, ignore the fact that the routing must be performed on a directed graph. This leads to excessive use of network resources and, consequently, to a high blocking ratio of the arriving requests as well as high average cost of the established ones. In this paper, a new segment-based method is proposed for the aforementioned problem, that was especially designed in order to have improved performance for directed-graph networks. It is shown through simulations that the proposed technique outperforms the existing relevant methods. A comparison with the optimal solution calculated using integer linear programming for the case of establishing a single multicast request at a time, shows that the average cost (of the established multicast requests) obtained by the proposed technique is close to the optimal.