Limited Deflection Routing Studies In The Obs

With rapid development of computer network technology, the information industry and its applications have made tremendous progress. There is increasing dependence on network for individual users and enterprise units, such as governments, financial institutions, telecom industry, etc. especially with rapid of increasing of point-to-point multimedia information and IP-based real-time service, which lead to the rapid growing exponentially of internet traffic. The traditional network can no longer meet traffic, operational and the change of performance, And with the rapid development of optical technology, at the same time, the quick evolution of optical technologies has allowed the transmission of huge amount of data on optical fiber. Under the existing structure of the optical transmission system, Optical burst switching (OBS) have the potential to became an efficient and flexible switching paradigm for the next-generation optical internet. As OBS relies on one-way reservation it easily occur contention, in order to achieve a low burst loss probability and efficient performance. Efficient contention resolution is significant, therefore how to resolve the burst conflict is key issue.Contention situations in OBS can be resolved in FDL, Wavelength conversion, Deflection routing ,Burst Segmentation and their combination .Because FDL only referred to relatively small delay and limited flexibility. It can not provide with the RAM cache capacity, so it rarely used alone to resolve the burst confliction. Wavelength conversion requires advanced optical technology, nowadays it must be at the large of cost, if wavelength conversion can be carried out. Burst segmentation can divide bursts into several parts, and it only dropping the actually contending parts of a burst, but the dropped parts can conflict with other bursts, it reduce the network utilization, also requires additional functionality in the core nodes to control and signal the segmentation process. Therefore, Deflection routing will be considered for the remainder of this thesis. Making using of more easily achieved limited deflection routing reduce burst loss probability and improve network performance.The limited deflection routing improves the performance of shortest path prioritized random deflection routing by adding a deflection check function and OBS edge nodes sender retransmission. In the case of confliction, deflection check function can make a choice whether to deflect the burst, consequently it can prevent the deflected burst from being dropped, economize network resources and improve network performance. The sender retransmission in OBS edge node ensure that the dropped burst can be retransferred in OBS layer but not in higher layers such as TCP layer, which reduces the time that the burst be transmitted in OBS network, increases the network throughout. By adding a deflection check function and OBS edge nodes sender retransmission, the shortest path prioritized random deflection routing can be turned to the limited deflection routing from a passive algorithm to active and dynamic algorithm, the limited routing not only achieve a low burst loss probability and efficient performance but also improve network throughout and the utilization of network resources.Chapter one introduces the research background, the development of optical networks, OBS network Research Status and the content of this paper. Chapter two discusses the basic principle of OBS, control protocols and algorithm implementation, the functions of core and edge nodes and deflection routing. The algorithm and the idea of the shortest path priority deflection routing are mainly analyzed in chapter three. In chapter four we propose a new restricted deflection routing algorithm together with the simulation results which shows that the technologies proposed in this paper achieve a better network performance than traditional ones. Conclusion and forecasting comes last.