Robust routing in wide-area WDM networks

This paper considers the problem of establishing robust routes for user connection requests in an WDM network dynamically. The problem is to find two edge-disjoint routes with satisfying certain given properties. One route will serve as the primary path, and another will serve as the backup path which will replace the primary path if there is any link failure in the primary path. Two versions of the problem are studied: one is to find two edge-disjoint paths such that the total cost of the two paths is minimized, in terms of the network resources consumption; the other is to find two edge-disjoint paths to minimize both the network load (link congestion) and the total cost of the two paths. The exact and approximate algorithms for the problem are proposed, and the solutions delivered consist of selecting routes, assigning wavelengths to the links, and setting switches of wavelength conversion at intermediate nodes on the routes. The performance ratio between the approximate solution and the exact solution is also analyzed. The key technique used in the design of the approximate algorithms, is to transform the corresponding version into a well solved optimization problem on an auxiliary graph. To the best of our knowledge, this is the first time that in the design of routing protocols for WDM networks, the network load and the route finding and wavelength assignment are taken into account simultaneously. As results, it not only finds cheap routes but also reduces the number of network re-configurations, thereby improving the performance of the network through utilizing its resources effectively.