Routing and Wavelength Assignment for Prioritized Demands Under a Scheduled Traffic Model

In the scheduled traffic model, the design problem is to allocate resources to a set of demands whose setup and teardown times are known in advance. A number of integer linear program (ILP) solutions for this problem have been presented in the literature. In this paper we present a new ILP formulation for routing and wavelength allocation, under the scheduled traffic model that minimizes the congestion of the network. We propose two levels of service, where idle backup resources can be used to carry low priority traffic, under fault-free conditions. When a fault occurs, and resources for a backup path need to be reclaimed, any low priority traffic on the affected channels is dropped. The results demonstrate that this can lead to significant improvements over single service level models. We are able to generate optimal solutions for moderate sized networks, within a reasonable amount of time. Finally, we present a simple and fast heuristic that can quickly generate good solutions for much larger networks.