Performance analysis of a backward reservation protocol in networks with sparse wavelength conversion

In sparse wavelength conversion networks only a few nodes support wavelength conversion. The optical paths in the network consist of a group of segments where each segment independently must meet the wavelength continuity constraint when setting up lightpaths across them. In this paper, we propose a distributed control algorithm called First-Available that can efficiently be used to assign wavelengths in networks with sparse wavelength conversion. The wavelength reservation protocol described is a backward reservation protocol. In previous research it has been found that backward reservation algorithms do not offer much improvement in the case where optical converters are used. First-Available was compared to other backward reservation algorithms such as First-Fit and Random and was shown to outperform those in the case of sparse wavelength conversion. Also, compared to the case of no conversion in the network the use of the First-Available algorithm in combination with using converters gives a lower average blocking probability. In previous papers, we have outlined a method called OBGP to support lightpath setup and management. We have used OBGP to implement and simulate the First-Available algorithm in OPNET. From our simulation results we also collected nodal statistics, and based on these we studied where should be the optimal placement of the converters using the First-Available algorithm.