On factors affecting the performance of dynamically groomed optical WDM mesh networks

In this paper, we consider the problem of traffic grooming in optical wavelength division multiplexed (WDM) mesh networks under dynamic traffic conditions. Grooming can be done at each node by using electronic SONET add-drop multiplexers (SADMs) to multiplex several low-rate connections on to the high-capacity wavelength channel, and provision them as a single lightpath. However, SADMs are costly devices and it is expensive to equip each port and wavelength in every node with grooming capabilities. This leads to the concept of limited grooming that uses fewer SADMs at the nodes: only a subset of the ports and wavelengths are equipped with SADMs. The paper presents a systematic performance evaluation of a limited grooming optical network supporting dynamic traffic requests. Four different limited grooming node architectures and related grooming policies are presented. We consider the effect of several important factors including: connection granularity, traffic grooming policy, number of grooming ports per node, grooming port tunability, and wavelength conversion. Simulation results indicate that limited grooming at each node is sufficient to obtain the performance obtained with full grooming, especially when connections occupy a small fraction of the wavelength capacity. Further, the connection granularity, the grooming policy and the number of wavelengths used per link for a connection are also seen to have a significant effect on the performance. The tunability of the SADMs and the port-sharing architecture are not seen to have a significant impact on the performance.