Journals Proceedings

Abstract

This problem of traffic grooming, routing, and wavelength assignment (GRWA) is considered with the objective of minimizing the number of transponders in the network. We first formulate the GRWA problem as an integer linear programming (ILP) problem. Unfortunately, the resulting ILP problem is usually very hard to solve computationally, in particular for large networks. To overcome this difficulty, a decomposition method is proposed that divides the GRWA problem into two smaller problems: the traffic grooming and routing (GR) problem and the wavelength assignment (WA) problem. In the GR problem, we only consider how to groom and route traffic demands onto light paths and ignore the issue of how to assign specific wavelengths to light paths. Similar to the GRWA problem, we can formulate the GR problem as an ILP problem. The size of the GR ILP problem is much smaller than its corresponding GRWA ILP problem. Once we solve the GR problem, we can then consider the WA problem, in which our goal is to derive a feasible wavelength assignment solution. In this paper, we implemented the fault tolerance technique to the load balanced Routing and Wavelength Assignment (RWA) problem in which the wavelength is allocated by using an advanced reservation algorithm. The primary path is set by applying Max-flow and load balancing techniques. A backup path is then computed for handling the failures by checking the class of the request as protection or restoration. Based on the class, we find the available bandwidth for each backup path. An auxiliary graph is constructed based upon the link cost. The backup path is computed using these link costs and the wavelength assignment is performed using the first fit wavelength assignment technique. From our simulation results, we show that by establishing the backup path, fault tolerance in routing and wavelength assignment become effective.