Study Of Burst Assembly In OBS Network

Optical Burst Switching (OBS), combing the benefit of Optical Circuit Switching (OCS) and Optical Packet Switching (OPS), is a promising method for the next generation optical Internet. Given that TCP almost occupy 90 percent of applications on the Internet, services in common use (Ftp, Http and etc.) are all based on TCP, which will still prevail in the future, TCP performance over OBS is an interesting issue. The effect of burst assembly parameters on TCP performance is studied in this paper for TCP performance is sensitive to burst assembly delay and loss rate.The relationship between TCP congestion window size and packet loss is analyzed by introducing the congestion control mechanism of TCP. Then the impact of loss rate and assembly delay on the network performance is qualitatively analyzed by introducing a module of send rate. When the loss rate of the network is not so high (less than 1%), the Optimal Maximum Assembly Length of Max-Time-Min-Max-Length Assembly Algorithm is proposed through investigating abundant simulation results, which is in proportion to the sum of receive buffer with the ratio of MTU/MSS.Finally, an Assembly Algorithm with EN Differentiation based on unsymmetrical traffic is proposed and simulated, which takes any assembly algorithm on the SEN and the corresponding algorithm with EN Differentiation on the CEN. It improves assembly algorithm from the view of assembly parameters design over the asymmetry of traffic but not grounds on any specific assembly algorithm. The results from simulation of different propagation delay and loss rate, taking Max-Time-Min-Max-Length Assembly Algorithm as an example, show that the end-to-end performance will increase from 7% to 54%. This algorithm can be used not only in the Max-Time-Min-Max-Length Assembly Algorithm, but also in any other assembly algorithms with both assembly length and time threshold as parameters.