A New Contention Avoidance Scheme in Optical Burst Switch Network

Abstract

Optical burst switching (OBS) is developed as an alternative switching technology, which combines advantages of both optical circuit switching (OCS) and optical packet switching (OPS) and avoids the disadvantages. In OBS control packet called control burst is separated from data packet called data burst. A control burst is sent in advance, which configures the switches in the path for the data burst. Due to lack of adequate contention resolution technique data burst loss is high in OBS. Schemes such as fiber delay line (FDL), wavelength conversion, deflection routing are the solution to prevent network congestion. But they have their own limitations. So a contention resolution technique is needed in OBS. In this paper we propose a scheme to minimize contention and to control traffic flow in the network. The proposed scheme logically divides a given network to clusters and selects a node as cluster head from each cluster. Cluster head keeps track of the resources available in the network and exchange the status of the resources among themselves to maintain up-to-date information. A node within a cluster that wishes to send a burst make request to its cluster head for a available wavelength on the path to destination. If a unused wavelength is available on the path to its destination, then it send a reply message with the available wavelength else send a reply no wavelength is available. Node after receiving a reply from the cluster head send a control burst followed by data burst on the wavelength that it has received from cluster head. If the reply says no wavelength is available then it waits for some specified time and sends another request. Since the cluster heads maintain the status of the resources at any time, t, it will minimize the contention of bursts. We made a comparison between the different techniques using simulation. Our simulation result shows propose method gives lower burst loss.