Research On The Rerouting Algorithm In Elastic Optical Network

With the continuous progress and development of Internet Technology, the network has gradually penetrated into all areas of society, and the demand of network bandwidth increases step by step. At this stage, because of WDM Network is very difficult to get greatly increased, so there is an urgent need for new technology to use the network bandwidth resources more fully and reasonably. Therefore the Elastic Optical Network(EON) came to being. Nowadays Researching on the Elastic Optical Network technology is the hotspot of core networks.In EON, a complete wavelength bandwidth is divided into a number of equal sized fragments, called the frequency slot block. So that the suitable bandwidth resources can be distributed for the different sizes of traffics and also the utilization of spectrum resources can be improved. However, in the spectrum of a flexible optical network environment, the fragmentation is unavoidable. Due to the constraints on the spectrum consistency and the continuity, the traffic blocking probability of the network is increased in a certain extent, which will lead to that the network performance is not as expected. If the fragmentations of EON were organized, it can reduce the blocking ratio and also can improve the utilization rate of bandwidth in the network. The main work of this thesis is to put forward rerouting algorithms and try to use few rerouting operation to reduce the spectrum fragmentation problems, and then improve the utilization ratio of spectrum resources of networks. The main work of this thesis is as follows:(1) The rerouting algorithm based on sliding window mechanism is proposed. For the traffic being reached, if it reroutes failed, then the number of t he frequency slot block of this traffic is used as the size of the window. The window is sliding one by one frequency slot in the two-dimensional light link, so that we can find out the spectrum to produce traffic congestion directly. Shifting of the spectrum block, we can use the KSP+BF/FF RSA algorithm, in order to spare the available idle spectrum segment to rerouting the traffic. The simulation results show that the algorithm of the network blocking probability than that before is reduced, but under the higher traffic load, the value of reducing is not obvious. On the other hand, the rerouting ratio of this algorithm is a little high because of the timing of staring the rerouting operation, but under the low traffic load, it is acceptable.(2) The rerouting algorithm based on the important link is proposed. The size of node is distinguished according to the degree of importance of the nodes in the network, then the links between the big nodes are ca lled important links. With the conception of the Available Spectrum Consecutiveness implying the fragmentation degree of links, the rerouting traffic is routed by going through as little important links as possible and is ensured that the new important links are less than that before. It is convenient for the incoming traffics to pass the light. The simulation results show that the blocking probability of this algorithm is smaller than that before, but also the rerouting ratio is less, and it is these characteristics that determine the superiority of the algorithm.