Burst Assembly Algorithm In Obs Networks

With the development of internet and the appearance of many new businesses such as multimedia netpage,multimedia games ,multimedia meeting and electron-commerce etc ,the rising internet services have increasing rapidly.As the multiformity and the multichange of the internet services,the traditional core-exchange-network has already not been suitable for the development of internet. By this position,the investigators are working hard in the field of WDM (Wavelength Division Multiplexing)network and the optional switching technologies of all-optical network to fit to the development of the explosing increase of internet runoff, the multiformity and the multichange of the internet services.The OBS is catching our eyes because it takes advantage of OCS(Optical Circuit Switching) and OPS(Optical Packet Switching) while avoiding the defects of them.In OBS,the burst data transmit throught the obligated bandwith resourse by the BHP(Burst Head Packet, which is similar to the packet head in packet switching ) ,the burst data pass cut-throught the OSN(Optical Switching Node) without any memory.Compare to OCS,The OBS is higher in the field of bandwidth usage efficiency because in the OBS,every wavelength may be multiplexed by burst data.On the other side,because the offsettime is far shorter than the time that the wavelength channels will be founded,the ETE delay is relativity short.So OBS offers a feasible and effective way for realizing all-optical communication networks at present.Connected by multi-channel optical links, the edge routers that work in electricity field and the core OSN that work in optical field can compose the OBS network. The burst data is compoded of IP packet which may come from different IP routers in tradition IP internet.The BHP is passed throught the individual channels that is independent of the data channels,and every burst data contains one BHP.The BHP contain all necessary contron information,such as burstlength,offsettime etc.The BHP needs O/E exchange in the OSN and estimate the routes in the field of electricity to assure to all the data burst must be passed through the OSN in the optical field.The objective to form the data burst is to augment the grain of exchange. 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 the shortter latency time and the higher effective in bandwidth usage . FRR (Forward Resource Reservation) algorithm and PA-FRR(Precision Assembly with Forward Resource Reservation) is an efficient method to reduce the end-to-end data burst delay and improve the effective in bandwidth availability, but they still have some defections in fixed burst assembly periods.Aiming at the potential problems in the FRR,PA-FRR algorithm, this thesis is trying to make some improvements and innovations in the following aspects:(1) A new burst assembly algorithm named ADC (Assembly Duration Forecasting ) is proposed. Through using the dual-buffer structure, the forword period forecasting and precision assembly scheme, ADC can not only keep the higher effective in bandwidth availabilitybut also reduce the end-to-end delay effectively.(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, theADC, FRR and PA-FRR algorithm are simulated in OBS network. And some researches on the performance and reducement of end-to-end delay and improvement of bandwidth usage efficiency of ADC relative to FRR and PA-FRR algorithm were done. The results coming from the simulation demonstrate the advantages of the ADC as compared to the FRR and PA-FRR scheme.