Routing Policy on Robustness in WDM Optical Networks

Path protection and link protection schemes are the main means of protecting wavelengthdivision multiplexed (WDM) networks from the losses caused by a link failure such as a fiber cut. We propose a new protection scheme, which we term partial path protection (PPP), to select end-to-end backup paths using local information about network failures. PPP designates a different restoration path for every link failure of every primary path. PPP allows the re-use of operational segments of the original primary path in the protection path. Our study also consider to assign different protection paths to every segment, instead of every link, of a primary path to reduce the computational complexity. The result demonstrates that the network efficiency can be improved by using the local information of network failure. A novel approach used in this paper is that of a dynamic call-by-call model with blocking probability as the performance metric. This is in contrast with traditional approaches to restoration, which consider capacity-efficiency for batch call arrivals. Since optimizing the blocking probability is a large dynamic optimization problem, we present two heuristics for implementing PPP. We show that a simple method based on shortest path routing for which primary paths are selected first is more effective than a greedy approach that minimizes, for each call arrival, the number of wavelengths used by the primary and backup path jointly. The network reliability issues on the interconnection policy is investigated in our study. We will show that employing better protection schemes will intensify the competition in the industry. Thesis Supervisor: Muriel Medard Title: Assistant Professor Thesis Supervisor: Eytan Modiano Title: Assistant Professor