Research On Routing And Wavelength Assignment Algorithm In OBS

Optical Burst Switching (OBS) is a promising solution for all-optical WDM networks. It combines the benefits of optical packet switching and wavelength routing while taking into account the limitations of the current all-optical technology. The one-way reservation protocol adopted by OBS makes the routing and wavelength assignment (RWA) in OBS uncertain, hence, the high burst drop rate. The paper studies the RWA algorithms in OBS. Generally, the shortest paths between the source and the destination pairs are used as the routes of the bursts while the wavelengths are assigned in a hop-by-hop manner. These algorithms suffer from high burst drop rate, especially in an unsymmetrical network. The paper proposes a RWA algorithm. For a source-destination pair, the bursts will be poured into the shortest path, the second shortest path, the third shortest path in turn. Meanwhile, the wavelengths are assigned based on a algorithm derived from the ant system. In order to testify the performance of our proposed algorithm, we develop an OBS simulator based on NS-2. The numerical results from simulation show that our algorithm can not only decrease the burst drop rate, but also balance the traffic load on the links.