In a wavelength division multiplexing (WDM)-based network, lightpaths are established between router pairs to form a virtual topology residing on top of the underlying physical topology. The ability to reconfigure its virtual topology upon dynamically changing traffic patterns has been identified as one of the most important features of WDM-based networks. Given a multifiber WDM network with limited fiber and wavelength resources, an existing virtual topology, and a new set of traffic demands, this paper addresses the problem of finding the new virtual topology that maximizes the carried traffic of connections, while absolutely guaranteeing that ongoing connections are not disrupted. We introduce conditions under which the new virtual topology has the intrinsic property of no service disruption. Then, we use these conditions to formulate the reconfiguration problem as an integer linear program (ILP). We also present a heuristic reconfiguration algorithm that is based on partitioning the traffic demands, so as to maintain wavelength loads as balanced as possible, followed by solving a sequence of single-wavelength problems. We theoretically verify the correctness of the algorithm, and illustrate its efficiency in terms of solution quality and computational cost via numerical experiments.
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