Research On Multicast Routing Algorithm Based On Multi-tree In Elastic Optical Network

The traditional WDM optical network is based on fixed grid,which has disadvantages such as low spectrum utilization and poor flexibility,and it is difficult to meet the increasing demand of network traffic.In this case,elastic optical network emerges as the times require,and has become the mainstream architecture of next generation optical network.Compared with WDM optical network,elastic optical network has the advantages of smaller spectrum granularity,higher flexibility and adaptive modulation,which can greatly improve the utilization of network spectrum resources.However,due to the fundamental difference between elastic optical networks and WDM optical networks,many problems based on WDM optical networks need to be further studied in combination with new conditions.As a key issue in flexible optical networks,multicast routing and spectrum allocation are critical to improving the application performance of flexible optical networks.This paper makes a deep study on multicast routing in elastic optical networks from various perspectives.Firstly,this paper studies the multicast routing problem based on transit node.When spectrum allocation for a multicast service fails,it may be due to the poor relative position of the source node and the destination node,resulting in the poor shape of the built multicast tree,and ultimately no available free frequency slot in the multicast tree.Therefore,the service that fails to allocate spectrum is given the second opportunity to build a tree.That is,select a transit node as the new source to re-establish a multicast tree and connect the source node to the newly-built multicast tree,and try to allocate spectrum on the new multicast tree again.This paper introduces three different strategies for selecting transit nodes,which are minimizing cost,maximizing spectrum continuity and minimizing weighted sum.According to the concept of spectrum continuity and weighted sum,this paper also makes corresponding improvements to the MPH algorithm.Simulation results show that these three multicast routing algorithms can effectively reduce the network blocking rate and improve the network performance.Among them,the strategies of maximizing spectrum continuity and minimizing weighted sum take into account both the cost and spectrum availability,and the performance is better than that of the strategy of minimizing the cost..Secondly,this paper studies multicast routing from the idea of branch of multicast tree and destination node classification.Due to the restricted conditions of spectrum allocation and the complexity of the multicast tree,it is particularly difficult to process multicast services.On the one hand,in order to weaken the constraints of spectrum allocation,this paper proposes a multicast routing algorithm based on multicast tree branch classification.By decomposing the multicast tree into multiple branches and using different frequency gaps for each branch,the probability of the service being successfully carried by the network is greatly improved.In order to reduce the cost of equipment,an algorithm is proposed to classify the branches of multicast tree,so that each class can use the same frequency slot.On the other hand,this paper proposes a multicast routing algorithm based on node classification,which separates the nodes that make the multicast tree have no available free frequency gaps,and establishes subtrees for these nodes by combining with the idea of transit node.The subtree can use different frequency slots from the original tree.The simulation results show that these two algorithms can greatly reduce the network blocking rate and improve the network performance.However,both of these algorithms require the use of more network equipment and consume higher costs.