Distributed algorithm for dynamic logical topology reconfiguration in IP over WDM networks

In this paper, we present a novel distributed algorithm to solve the logical topology reconfiguration problem for IP over WDM networks under dynamic traffic. From the optimization model proposed in, we apply the Lagrangian relaxation to eliminate the capacity constraint and form a dual problem whose optimal solution is the lower bound of the original one. The dual problem is then decomposed into subproblems, which can be solved in a distributed manner. Based on the solution of the dual problem, a heuristic algorithm is proposed to obtain a good feasible solution for the original reconfiguration problem. Our distributed algorithm fulfils all requirements of the reconfiguration process, such as no service disruption, load balancing in the new logical topology while allowing to add and to delete multiple lightpaths. Moreover, the distributed approach offers a high scalability. Not limited to small or medium-sized networks as the centralized model in, this distributed algorithm can be applied to large networks with the computation time increasing linearly with the network size. The performance of the proposed distributed algorithm, which lends itself to a protocol implementation, is investigated and compared with the corresponding centralized approach.