Research On Multicast Adaptive Routing Algorithms In Elastic Optical Networks

With the rapid growth of Internet traffic,flexible-grid elastic optical networks(EONs)have attracted intensive research for the agile spectrum management in the optical layer.This thesis proposes two types of novel algorithms which focus on multicast routing and spectrum allocation(MC-RSA)in EONS.First,the thesis proposes a fragment-aware multicast routing algorithm by considering the link's fragment degree into the routing decision.The algorithm selects the links which have low level fragment degree to route the multicast request.Therefore,the thesis adopts three approaches describing the degree of link's fragment: external-fragment,entropy and spectrum continuity.The Static Link Weight Reassign algorithm and Dynamic Link Weight Reassign algorithm based on the three approaches are developed.The Static Link Weight Reassign algorithm reassigns the link's weight that can reflect the link's spectrum utilizing state to each link of the network and build the multicast light-tree,then it allocates the spectrum to each link of the multicast light-tree.The Dynamic Link Weight Reassign algorithm selects the links whose spectrum utilizing states are familiar to the light-tree which has been partially built.By doing this,it can avoid that the available spare frequency slot numbers decrease urgently when a new link is added into the light-tree.So,it can improve the probability to serve the multicast request.The simulation results show that the fragment-aware multicast routing algorithms can achieve lower blocking ratio than traditional Shortest Path Tree(SPT)and Minimum Spanning Tree(MST).Then,a new auxiliary graph model to address the multicast routing and spectrum allocation problem is designed.The new auxiliary graph is called Priority Graph.The Priority Graph is consisted of links which have some common frequency slots located in the same position of link's spectrum space.The multicast routing algorithm based on the Priority Graph is designed.it prefers to utilize the links in the Priority Graph to build the light-tree,then it adopts the First-Fit approach to allocate spectrum to the multicast request.The simulation results show that the proposed algorithm achieves lower blocking probability.