Due to the recent outstanding advancement of optical networking technology, pervasive Grid computing will be a feasible option in the near future. As Grid infrastructure, optical networks must be able to handle different Grid traffic patterns with various traffic characteristics as well as different QoS requirements. With current optical switching technology, optical circuit switching is suitable for data-intensive Grid applications while optical burst switching is suitable to submit small Grid jobs. However, there would be high bandwidth short-lived traffic in some emerging Grid applications such as multimedia editing. This kind of traffic couldn't be well supported by both OCS and conventional OBS because of considerable path setup delay and bandwidth waste in OCS and inherent loss in OBS. Quasi-Circuit OBS (QCOBS) is proposed in this paper to address this challenge, providing one-way reserved, nearly lossless, instant provisioned wavelength service in OBS networks. Simulation results show that QCOBS achieves lossless transmission at low and moderate loads, and very low loss probability at high loads with proper guard time configuration.
The most critical challenge in the design of burst optical networks is burst contention, which occurs when multiple bursts contend for the same wavelength on the same link at a certain node simultaneously. The techniques to address this problem include contention resolutions as well as contention avoidance. In contention resolution approaches, conflicts are resolved in wavelength, time or space domain when they have occurred. In contention avoidance approaches, bursty traffic is distributed through routes that are dynamically re-computed or selected according to network congestion status to avoid potential conflicts in advance. Current dynamic routing schemes for OBS are all based on global information, resulting in bandwidth consumption at signaling channels and a considerable delay between network status change and adaptation of the routing tables. In this paper, we propose a novel dynamic routing selection mechanism based on local statistical information, namely <i>dynamic alternative routing</i>, to balance load and avoid contentions in OBS networks. In this mechanism, a route is dynamically selected from the primary path and the alternative route for an incoming burst. The simulation results show the blocking probability of the proposal is significantly reduced and load balancing is efficiently achieved compared to the general OBS.