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Reroute sequence planning in multiprotocol label switching networks

Özbilgin, İzzet Gökhan
The growth of the Internet has caused the development of new protocols that enable IP networks to be engineered efficiently. One such protocol, Multiprotocol Label Switching (MPLS) enables IP datagrams in backbone networks to be forwarded based on the label switching forwarding paradigm. In MPLS networks, rerouting of Label Switching Paths (LSPs) can be needed in order to attain a better resource utilization in the network. In this case, a sequence of LSPs has to be found for their one by one reconfiguration without service interruption, involving the constraint that the link capacities should not be violated at any time during the rerouting process. This reroute sequence planning problem for LSPs is NP-complete. In previous works, the conditions of existence of any feasible reroute sequence are examined and algorithms are described for solving the problem, but it was shown that the problem is computationally hard in real-world situations because of the large amount of routers and LSPs in the network. In this work, we deal with the problem of reroute sequence planning problem of LSPs and present alternative solutions for the case when there is no feasible solution. We introduce a tool for the post-processing phase when a capacity violation is occurred during the sequence planning. We present an algorithm trying to reconfigure LSPs while allowing some interruption or degradation of traffic during the rerouting process.