Optical Burst Switching in WDM Ring Networks

摘要

Optical Burst Switching (OBS) is being envisaged as the next generation switching tech-nology to transmit Internet traffic directly over WDM networks with a fine granularity between Optical Circuit Switching (OCS) and Optical Packet Switching (OPS). It has higher bandwidth-efficiency than OCS. OBS is usually characterized by burstification, burst header packet (BHP) generation and data burst (DB) transmission. The burst header packet is transmitted first by the source to the destination followed by the data burst. Each intermediate node processes the header electronically so that the data burst corre-sponding to that BHP is transparently switched without requiring any O/E/O conversion. This unique feature of OBS requires a strict coordination between DB and BHP and thereby making it a challenging task. OBS has been implemented in WDM ring networks for FT-TR (Fixed tuned Transmitter and Tunable Receiver) systems and TT-FR (Tunable Transmitter and Fixed tuned Receiver) systems. In FT-TR systems, the number of chan-nel and destination collisions is higher whereas there is no source collision due to the fixed tuned nature of the transmitter. In TT-FR systems the number of channel collisions is large as multiple nodes communicate using the same channel but there is no destination collision. In this work I have implemented OBS in WDM ring networks for TT-TR (Tunable Transmitter and Tunable Receiver) systems. It has been shown that the pro-posed protocol is free from source and channel collisions, as well as reduces destination collision to a greater extent. The tunable transmitter and tunable receiver node architec-ture has been described. We compared the performance of TT-TR system with that of TT-FR system with respect to number of packets lost, average queuing delay and average propagation delay. It is found that the proposed protocol is more effective in avoiding collisions than the TT-FR.