Provisioning fault-tolerant scheduled lightpath demands in WDM mesh networks

In this paper, we consider the problem of routing and wavelength assignment (RWA) of fault-tolerant scheduled lightpath demands (FSLDs) in all optical wavelength division multiplexing (WDM) networks under single component failure. In scheduled traffic demands, besides the source, destination, and the number of lightpath demands between a node-pair, their set-up and tear-down times are known, in this paper, we develop integer linear programming (ILP) formulations for dedicated and shared scheduled end-to-end protection schemes under single link/node failure for scheduled traffic demand with two different objective functions: 1) minimize the total capacity required for a given traffic demand while providing 100% protection for all connections; and 2) given a certain capacity, maximize the number of demands accepted while providing 100% protection for accepted connections. The ILP solutions schedule both the primary and end-to-end protection routes and assign wavelengths for the duration of the traffic demands. As the time disjointness that could exist among fault-tolerant scheduled lightpath demands is captured in our formulations, it reduces the amount of global resources required. The numerical results obtained from CPLEX indicate that dedicated scheduled (with set-up and tear-down times) protection provides significant savings (up to 33 %) in capacity utilization over dedicated conventional (without set-up and tear-down times) end-to-end protection scheme; shared scheduled protection provides considerable savings (up to 21 %) in capacity utilization over shared conventional end-to-end protection schemes. Also the numerical results indicate that shared scheduled protection achieves the best performance followed by dedicated scheduled protection scheme, and shared conventional end-to-end protection in terms of the number of requests accepted, for a given network capacity.