Research On Burst Assembly Mechanism Based On Priority In Optical Burst Switching Networks

With the development of informationization and networkization, internet traffic isgrowing briskly. Along with the demand of network interaction and flexibility, theimprovements in transmission capacity and exchanged rate is a burning issue. Thetransmission efficiency has been increased greatly since WDM technology was proposed onthe basis of research in optical multiplexing instead of electrical multiplexing technology.Optical burst switching is an emerging technology that can efficiently utilize the hugebandwidth resources provided by WDM. Based on the current technologies and costrestriction, OBS take advantage of OCS (Optical Circuit Switching) and OPS (Optical PacketSwitching) while avoiding the disadvantages of them. Because of overcoming the electronicbottleneck in the traditional exchange technology and greatly improving network bandwidthutilization, optical burst switching is considered as the most promising optical switchingtechnology in the next generation of all-optical network.Burst assembly in edge node is the first step in business access of OBS networks, it is theprocess of aggregating and assembling IP packets into a burst at edge nodes in OBS networks.It affects the valid implementation of conflict resolution and the character of traffic, soconcerns the efficiency of entire network to a large extent. In view of these facts, design areasonable assembly scheme has great significance for the effective implementation of theconflict resolution methods, reducing the end-to-end delay and improving the networkthroughput. The OBS networks fundamental and architecture are studied firstly in this paper.Then the operating principle and relative merits of several traditional assembly mechanisms inOBS networks are comprehensively expounds.Secondly, considering the problem of waste of bandwidth resources mainly caused bypadding in invalid date to satisfy the minimum assembly burst length, an improved hybridassembly algorithm is put forward. When the length of real-time business is lower than theminimum threshold, use offset time to delay the burst generation time first, because thisapproach can reduce the number of “short burst” generated due to their lengths don’t meet theminimum value. For the small amount of “short burst” at last, filled with the lower-class IPpackets with same destination address rather than invalid packets. By doing so, not only theassembling burst length is met, but also more date information can be transmitted. Analysisand simulation result shows that the method can effectively improve the channel resourcesutilization rate and reduce network packet loss rate.At last, to ensure the integrity of burst data packet and provide differentiated quality of service (QoS) for different classes of packets, meanwhile, reduce the packet loss probability, anovel priority-based composite burst assembly scheme for optical burst switching (OBS)networks is proposed. The low and high packets classes are aggregated into a single burstsimultaneously and the highest-priority packets are placed in the middle while low-prioritypackets at the tail and head of the burst. The priority lowers gradually from the middle to theends. Simulation results demonstrate that the proposed assembly strategy not only guaranteethe integrity of high-priority bursts, but also significantly reduce the end-to-end delay andimprove the loss performance of network, so could adapt to the flexible network with QoSrequirement.