Study On Several Key Technologies Of Resource Assignment In Optical Burst Switching Network

OBS (Optical Burst Switching) is a promising solution for future IP over WDM network. It has got the advantage of low transmission delay, supporting bursty traffic and so on. However, due to the limited number of data channels and the lack of mature optical buffer and optical logic device, data bursts may be occasionally lost at the core nodes by collision. Besides, the offset time configuration mechanism, the route selection strategy and the characteristics of applications in OBS network are closely related to the performance of burst loss, transmission delay and so on. So, relevant resource assignment technologies need to be studied, so as to efficiently and fairly schedule limited OBS network resources. In this thesis, we study further on several key technologies of resource assignment in OBS network.As for the burst scheduling algorithms, a traffic tree based burst scheduling algorithm is proposd to efficiently schedule limited data channels for bursts. It adopts greedy algorithm and split algorithm respectively to minize the number of burst overlaps in core network, which can cause possible burst collisions. The proposed scheduling algorithm can achieve lower burst loss ratio compared with traditional LAUC-VF algorithm. To fairly schedule data channels for bursts, a pre-emption based burst scheudling mechanism is also accordingly designed to improve the fairness performance among TCP flows and UDP flows in OBS network.To efficienly assign OBS paths for different traffic flows, we proposed an efficiency first routing selection stragegy that considers the utility of traffic flows when selecting routes path for them, and the cost on the lost burst throughput after making the selection. The proposed strategy can reduce burst loss ratio when the background traffic is unbalanced compared with the traditional shortest path and least burst los ratio strategies.We also studied the impact of the offset time configuration mechanism on the performance of burst loss ratio and delay in OBS network. Receiving, forwarding, scheduling and sending modules in the control plane are modeled by queuing models, respectively. A distribution function based offset time configuration mechanism is accordingly designed based on these models, where central limit, large deivation, PH distribution methods are adopted respectively to derive the distribution function of total BHP processing time. The mechanism can effectively meet the trade off between the burst transmission delay and the burst loss ratio caused by insufficient offset time.Finally, a centralized OBS based grid architecture is proposed by taking the advantages of OBS network and the requirements of the grid applications into account. The architecture is easy to apply and able to achieve the global optimal resource assignment results. Three resource scheduling strategies for the architecture are accordingly designed from the grid level, network level and OBS network level, respectively.