Implementation of a traffic engineering technique that preserves IP Fast Reroute inCOMET

Ho, Trong Viêt [UCL] François, Pierre [UCL] Deville, Yves [UCL] Bonaventure, Olivier [UCL]

With Intradomain Routing Protocols, by optimizing the configuration (Trafic Engineering -TE) of link weights, operators can significantly improve the load of their links, which is known to be an NP-hard problem. Another emerging issue for ISP networks is the fast restoration of IP services in the case of failures. Recently, Fast Reroute techniques have been proposed for pure IP networks. The Loop Free Alternates (LFA) is one of the most promising technique. An LFA for a router A, for a destination d, is a neighbor C of A which does not use A to reach d, so that A can prepare itself to directly reroute the traffic destined to d along its link with C upon the failure of the link that A is using to reach d. Our objective is to provide a TE technique that takes the coverage of LFAs into account during the network resource usage optimization. Constraint Programming and Constraint-Based Local Search are well suited for solving such complex combinatorial problems. Especially in COMET, some classical problems can be modeled in only about a dozen lines of code. So, we have chosen a local search algorithm implemented in COMET for solving our traffic engineering problem.