Wavelength requirement for survivable routing in WDM networks

Abstract

In IP over WDM networks, when a failure (a link failure) occurs, the service restoration can be implemented by dynamic routing in IP layer. But it needs the virtual topology remains connected after any physical link failure. Otherwise, IP layer cannot find an alternate path to restore the service. The problem of routing logical links (lightpaths) on a physical network in a way that the logical topology remains connected in the event of single physical link failure is called survivable routing. Our aim is to find out the minimum wavelength requirement for survivable routing. In short, we address the survivable routing problem by proposing a new ILP algorithm which works well with sparse-connected logical topologies. The necessary and sufficient conditions for survivable routing are simplified, which greatly reduces the number of survivable constraints. Based-on the simplified conditions, a new ILP formulation with K-shortest paths as alternate paths for a logical link is presented, which mainly reduces the number of variables needed to be solved. It will be demonstrated that the time needed to solve such an ILP is relatively small. Finally, numerical results are given and discussed to show the effectiveness of our algorithm.