Burst Assembly Algorithm In Obs Networks

With the progress of society, the rising data services (such as broadband video, multimedia service and realtime/quasi-realtime service, which take more bandwidth resource) have been increasing rapidly. To build a high-speed all-optical WDM (Wavelength Division Multiplexing) network has been the trend of the development of communication network in this century. OBS (Optical Burst Switching) is one of the optional switching technologies proposed to implement all-optical network, in which the transmission unit is the burst composed by some IP packets with the same addresses and properties. Taking advantage of OCS (Optical Circuit Switching) and OPS (Optical Packet Switching) while avoiding the defects of them, OBS offers a feasible and effective way for realizing all-optical communication networks at present.Connected by multi-channel optical links, the edge routers and the core OSN can compose the OBS network. The basic exchanging unit is the burst which can be combined by two parts: BHP (Burst Head Packet, which is similar to the packet head in packet switching) and data burst. IP packet data is assembled into data burst at ingress router, and then the data burst is classified and queued according to the destination address, QoS (Quality of Service) type and priority etc. And the deburstification is performed at egress. The core OSN (Optical Switching Node) performs only forwarding, routing and exchanging of BHP and data burst. Consequently the key design issues related to OBS include burst assembly algorithm, contention resolutions, resource reservation schemes, QoS support etc.In order to meet the future need of real-time and quasi-realtime applications, the OBS network design requires short latency time. FRR (Forward Resource Reservation) algorithm is an efficient method to reducethe end-to-end data burst delay, but it still has some defections in bandwidth availability.Aiming at the potential problems in the FRR algorithm, this thesis is trying to make some improvements and innovations in the following aspects:(1) A new burst assembly algorithm named PA-FRR (Precision Assembly with Forward Resource Reservation) is proposed. Through using the dual-buffer structure, FRR and precision assembly scheme, PA-FRR can not only reduce the end-to-end delay effectively, but also avoid the bandwidth wastage caused by unsuccessful BHP pre-transmissions.(2) An extension to ns-2.26 is given, which can correct the mistakes of obs-0.9a released by Maryland University. In addition, some new simulation modules and objects are added, and the assembly algorithms and scheduling scheme used in obs-0.9a are revised, So a new simulation package- obs-0.9b is proposed, which offers a perfect simulation environment to prove the validity of PA-FRR algorithm.(3) By utilizing ns-2.26 and obs-0.9b, the FRR and PA-FRR algorithm are simulated in OBS network. And some researches on the performance and improvement of bandwidth usage efficiency of PA-FRR relative to FRR algorithm were done. Both theoretic analysis and simulation results demonstrate the advantages of the PA-FRR as compared to the FRR scheme.