Dynamic Virtual Topology Reconfiguration Algorithms for Groomed WDM Networks

Abstract

In a Wavelength Division Multiplexing (WDM) optical network, in which the traffic changes dynamically, the virtual topology designed for an old traffic set needs to be reconfigured for a new demand set in order to route more connections. Though reconfiguration increases the throughput, the resulting disruption in traffic is a cause for concern. We present a simple and flexible framework to evaluate the gain achieved by reconfiguration, based on the two conflicting objectives of increasing throughput and reducing disruption. We present adaptive reconfiguration algorithms which determine the change in the virtual topology with a corresponding change in the demand set. These algorithms incrementally add lightpaths to a given virtual topology and delete a minimum number of lightpaths to facilitate their addition. One of the algorithms improves throughput by making changes to the existing virtual topology and another one reduces disruption by making changes to the virtual topology suited for the new demand set. However, in order to reduce the gap in bandwidths between what a wavelength channel can provide and what an individual connection requires, several low-speed connections need to be groomed onto a single wavelength. As our algorithms aim at increasing the throughput with as few lightpath changes as possible, more connections will be accepted without considerable increase in number of lightpaths. This means, more connections are groomed onto the lightpaths. One nice feature of our approach is that it fits not only for groomed networks where traffic demands are at the sub wavelength level, but also for networks where connection demands are at the wavelength level. The extensive simulation studies, wherein we compared the performance of our algorithms with that of two other possible schemes, demonstrated their flexibility and robustness.