Capacity Utilization versus Congestion Levels in Wavelength Routing for Large Scale WDM Networks

Wavelength routing (WR) has been a key issue in WDM optical networks which carry huge amount of traffic aggregated from Internet protocol (IP), asynchronous transfer mode (ATM) and SDH/SONET layers. The problem, however, has been proved NP-hard. The time complexity and the optimality of solutions are two conflicting metrics. In addition, for optimization purposes, capacity utilization and network congestion level can be compromised to reduce the blocking probability of future connections. In this paper, we propose a heuristic approach for WR in large scale networks based on a balanced model developed for the capacity utilization and the congestion level. This is a two step approach, i.e K shortest paths (KSP) algorithm and a path selection algorithm (PSA), and is applicable not only at network design phase but also for online provisioning where a number of traffic connections may be requested simultaneously. We investigate the time complexity and the optimality of solutions as metrics for comparing our approach and the ILP formulation for wavelength routing. Simulation results show that our approach yields very promising results in terms of the optimality of solutions whilst also applicable to very large scale networks, say 500 nodes or more