The survivable logical topology routing problem in an IP-over-WDM optical network is to map each link in the logical topology (at the IP layer) into a lightpath between the nodes and in the physical topology (at the optical layer) such that failure of a physical link does not cause the logical topology to become disconnected. It is assumed that both the physical and logical topologies are at least two-edge connected. For this problem, two lines of investigation have been pursued in the literature: one pioneered by Modiano and Narula-Tam [Proc. IEEE INFOCOM, 2001, p. 348] and the other pioneered by Kurant and Thiran [Proc. Int. Conf. on Broadband Networks (BROADNETS), 2004, p. 44]. Since then there has been a great deal of research on this problem. Most of the works have not considered limitations imposed on the routings by physical capacity limits and other metrics in addition to survivability. In this paper, we first introduce two concepts: weakly survivable routing and strongly survivable routing. We then provide mathematical programming formulations for two problems. The first problem is to design a survivable lightpath routing that maximizes the logical demand satisfaction before and after a physical link failure. The second problem is to add spare capacities to the physical links to guarantee routability of all logical link demands before and after a physical link failure. We conclude with heuristics that mitigate the computational complexity of the mathematical programming formulations and with simulation results comparing these heuristics with the mathematical programming formulations.
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