Dynamic Grooming Algorithms

Abstract

The emergence of Wavelength Division Multiplexing (WDM) technology provides the capability for increasing the bandwidth of Synchronous Optical Network (SONET) rings by grooming low-speed traffic streams onto different high-speed wavelength channels. Since the cost of SONET add-drop multiplexers (SADM) at each node dominates the total cost of these networks, how to assign the wavelength, groom the traffic and bypass the traffic through the intermediate nodes has received a lot of attention from researchers recently. Moreover, the traffic pattern of the optical network changes from time to time. How to develop dynamic reconfiguration algorithms for traffic grooming is an important issue. For dynamic traffic grooming (DTG) at the network operation stage, connection requests arrive and depart dynamically. As resources have already been deployed in the network and will remain unchanged for some time, the objective of a DTG algorithm is to maximize network throughput, or minimize the blocking probability of connection requests. To achieve this objective, the grooming algorithm must provision resource-efficient routes for both lightpaths and connections. In this chapter, we describe, in detail, dynamic traffic grooming algorithms for two cases (best-fit and full-fit) for handling reconfigurable SONET over WDM networks. For each approach, an integer linear programming model and heuristic algorithms (based on the tabu search method) are given. The results demonstrate that the tabu search heuristic can yield better solutions but has a greater running time than the greedy algorithm for the best-fit case. For the full-fit case, the tabu search heuristic yields competitive results compared with an earlier simulated annealing based method and is more stable for the dynamic case. We also highlight related work on dynamic traffic grooming algorithms in other scenarios. SONET rings have performed well as telecommunication backbone networks for a long time [1]. Using WDM technology, multiple rings can be