Research Of QoS Scheme In Optical Burst Switching Network And Key Parameters Optimizing

The rapidly-growing Internet is driving the demands for higher transmission capacity and high-speed IP routers at an unprecedented rate. With the deployment of WDM technology in existing optical backbone networks to meet the bandwidth requirement of Internet traffic, the routers are likely to be the bottleneck of future Internet backbones. To reduce the burden of electronic devices (potential bottleneck), the coming optical Internet is bound to develop towards IP over Optical structure. In the three switching technologies proposed to implement IP over WDM, OBS takes advantage of OCS and OPS while successfully bypassing defects of them. Thus, OBS is considered a promising solution to provide terabit optical routing and to build an all-optical WDM layer for the next-generation optical Internet. This paper introduces the principle and basic conceptions of OBS, and the pivotal technologies of OBS are formulated. The issue of providing quality of service(QoS) in an optical burst-switching network is addressed , on which a new scheme is based. QoS is provided by introducing a composite burst-assembly technique at the edge core and prioritized contention resolution policies in the network core. In the composite burst-assembly technique, the confirmation of burst priority is discussed in detail. Besides the former algorithm of burst priority confirmation, a modified algorithm named proportional priority conformation is put forward. This proportional priority conformation can reflect the difference of upper layer date' quality of service on time and exactly. What is more, it can less the packet lost probability effectively and make the flow of network data more reposefully. As for prioritized contention resolution policies, the basic protocol is investigated and a simple algorithm, supporting QoS to set offset-time based on JET protocol is brought forward. The packet losing probability can be lessed a lot if a burst drop policy is added. So, the whole prioritized contention resolution policies include additional offset-time and burst drop policy. OBSns is built upon the widely used network simulator ns2.1b9 in order to incorporate the key components of burst assemblers. By this means, Simulations are conducted to evaluate the performance of QoS schemes in OBS and make the parameters optimized. Initial results and analysises on the burst loss probability show that using the proposed schemes can greatly improve the QoS performance, less the packet probability and give some theoretic and practical instruction on the construction of OBS network.