Research Of Contention Resolution In Optical Burst Switching Networks

With the rapid increase of business volume in optical communication network, thedemand for network bandwidth is much higher than before. Since wavelength divisionmultiplexing (WDM) can provide a huge bandwidth for optical networks, it has become thecore transmission technology of backbone network. How to make full use of the bandwidth ofnetwork in all-optical network, optical switching technology is playing a crucial role. Opticalburst switching (OBS) is considered as the most promising optical switching technologybecause of it has many advantages such us moderate exchange of size, all-opticaltransparently transmission, higher bandwidth utilization etc.In the OBS network, when two or more bursts require occupy the same network resourceat the same time will cause burst competition. Competition will lead to burst packet loss,thereby reduce network resource utilization. So this paper studies on one of the problems inthe OBS network--the optical burst data packet (BDP) competition issues. Firstly, it has acomprehensive and systematic elaboration aiming to the basic principle and system structureof OBS. And on this basis, the several key technologies of OBS network are discussedin-depth for providing theoretical basis of burst competition solution. Then, several traditionalcompetition resolution mechanisms are analyzed in detail and compared. Finally, the solutionhas been proposed respectively from the avoid conflict resource reservation protocol andcompetition based on priority. And through analysis, confirm the effectiveness of the twoschemes.This paper presents an improved of JET protocol to achieve maximum avoid burstscompetition. The protocol combines with optical buffering strategy based on DoD(Delay-on-Demand) protocol. In this agreement, when burst control packet occurscompetition of reservation resource in the first half of the routing, it can adjust the offset timeto avoid burst competition; and if the burst control packet in the last half of the routing, it canbe avoided by optical buffer for BDP. The analysis and simulation show that the protocolavoids the problem of burst competition in the OBS network in an effective way, thusreducing the network packet loss rate.To solve the problem of different priorities burst contention, a novel priority-basedcontention solution strategy for OBS network is proposed in this paper. When the contention occurs, considering the burst priority firstly, and then the burst segmentation method is usedfor the low-priority burst in this strategy. Under the ensuring integrity of high priority burst,the part of the segmented can be transmitted to the destination node via combiningwavelength conversion and optical buffers method. Simulation results show that the proposedscheme not only ensures the integrity of high-priority burst, but also reduces the packet lossrate of the low priority burst maximally, so that it can support good QoS for the network.