In synchronous optical networks (SONETs) and WDM networks, low-rate traffic demands are usually multiplexed to share a high-speed wavelength channel. The multiplexing-demultiplexing is known as traffic grooming and is performed by SONET add-drop multiplexers (SADM). The grooming factor, denoted by k, is the maximum number of low-rate traffic demands that can be multiplexed into one wavelength channel. SADMs are expensive, and thus an important optimization problem for traffic grooming is to maximize the number of accommodated traffic demands subject to a given number of SADMs. We focus on the unidirectional path-switched ring (UPSR) networks with unitary duplex traffic demands. We assume that each network node is equipped with a limited number L of SADMs, and our objective is to maximize the number of accommodated traffic demands in a given set. We prove the NP-hardness of this maximum throughput traffic grooming problem and propose a (k+1)-approximation algorithm. Extensive simulations are conducted to validate the performance of the algorithm. We also study the all-to-all traffic pattern for the maximum throughput traffic grooming problem and propose an algorithm that accommodates at least (nL⌊k⌋)/2 demands for a UPSR with n nodes. We also prove that any optimal solution can accommodate at most (nLk)/2 demands. Thus the solution of our algorithm is at most a constant factor (approximately 2) away from the optimum.
© 2008 Optical Society of AmericaPDF Article