Research Of Contention Resolution For OBS Networks

In recent years, with the fast development of Internet, network traffic increases rapidly. The tremendous demands on capacity of transmission and switching have urged people to engage in the research of WDM and optical switching technology. Presently there are three kinds of technology to realize all optical transmission: optical circuit switching(OCS), optical packet switching(OPS) and optical burst switching(OBS). OBS combines the virtues of optical circuit switching and packet switching while avoiding their shortcomings, which is one of the best way to realize all optical transmission.To reduce DB(Data Burst) dropping probability, the contention resolution scheme is necessary for an OBS networks. Optical buffering, wavelength conversion, burst retransmission, burst segmentation and deflectionrouting are typical technologies which can be used in OBS to resolve contention. Optical buffering and retransmission will increase end-to-end delay; The wavelength conversion is a good mechanism, but the cost of the wavelength conversion is too expensive; The burst segmentation can reduce the loss of the DB, however, the implement of burst segmentation is complex and difficult; so the deflection routing protocol is an effective contention resolution in Optical Burst Switching network at present time. However, it will lead to high loss of the normal traffic on reflected routing when the traffic load is large.Two kinds of contention resolution schemes including deflecting routing and burst retransmission, is studied in this paper. Furthermore, a new contention control scheme- hybrid algorithm considering deflection routing and retransmission, is proposed ,which combines the advantages and disadvantages of above schemes. According to certain predefined checking condition, the algorithm make the operation as retransmission or deflecting routing conditionally, in order to guarantee the QOS of data burst as well as improving network performance. Simulation results show that the proposed algorithm can efficiently control the contention effect on network,, and effectively improve the burst loss performance of entire networks.