Scheduling file transfers in WDM optical networks

We address the problem of non-preemptive scheduling of arbitrary sized file transfers in wavelength division multiplexed networks. We wish to assign a wavelength and a starting time to each path corresponding to a file in such a way that no two paths are assigned the same wavelength if concurrent transfer of files share a directed physical link. The objective is to minimize the total time spent transferring files across the network by the path set. In this paper, we obtain lower bounds on the time required for an optimal schedule and show the NP-completeness of the problem under various conditions. We then develop a scheme to produce a polynomial time approximation schedule that can be applied to arbitrary network topologies when the length of each path is bounded by two. Using this algorithm, we discuss the problem when the network topologies are rings, stars, trees, and meshes, and present near-optimal solutions.