Performance Evaluation Of TCP Over OBS Networks With Multiple TCP Input Flows

In this thesis, the performance of Transport Control Protocol (TCP) over Optical Burst Switching (OBS) network is evaluated. Several novel mechanisms, which are used for improving TCP throughput on OBS network with multiple TCP flows input, are also proposed and discussed in detail. This thesis is organized as follows:In section 1, the OBS networks, especially the network architectures and key technologies, are summarized and discussed.In section 2, three important factors, which probably effect TCP performance over OBS network with multiple TCP flows input, are theoretically analyzed. Included are burst loss probability, delay penalty and correlation benefit. The analysis results show that the burst loss probability will result in obvious degradation of TCP throughput, the delay penalty will also introduce negative effect on TCP performance, and correlation benefit always provides positive effect on TCP performance enhancement. These conclusions are further verified by simulations.In section 3, the burst assembly algorithm in OBS network is investigated, considering the scenario that OBS network is connected with multiple TCP flows. The relationship between the burst assembly algorithm and the TCP traffic load are also evaluated by extensive simulations. Assuming the mixed time/burst length assembly algorithm is adopted in the OBS network, the results show that if TCP traffic load is high, TCP throughput will increase firstly and then decrease with the increase of burst length threshold; if TCP traffic load is low, TCP throughput will not decrease with the burst length threshold increasing. Finally, in section 4, based on the assembly algorithm investigated in section 3, the impact of assembly queue numbers on TCP performance is studied. The simulation results show that reasonable number of assembly queues can improve the TCP performance over OBS significantly. When the burst length threshold is small, TCP throughput will be improved with the increasing of the assembly queue numbers. On the contract, when the burst length threshold is large, TCP throughput will be higher when using less burst assembly queues. For example, when the burst length threshold is 50KByte, TCP throughput of OBS network with two assembly queues is 69% higher than that with five queues, and 340% higher than that with ten assembly queues. Furthermore, TCP throughput will be changed with the increase of link drop rate. The more the assembly queues, the faster degradation of TCP throughput performance.