Research On Load Balancing Among Multiple Controllers In Software Defined Network

Software defined network,as an innovative model of future network,achieves the decoupling of control plane and data plane,and effectively solves the problem of network structure complexity by providing open programming interface,which cause the continuous expansion of traditional network function and application.With the increasing number of users and the diversity of SDN deployment scenarios,the network composed of a single SDN controller can no longer meet people's needs.Therefore,the distributed deployment of multiple controllers has been paid close attention to academia and industry.As the deployment of multiple controllers in SDN network is affected by the number of controllers and the deployment location of controllers.It is easy to lead to the phenomenon of overload or light load among controllers,which make the cost of network equipment and the waste of a large number of network resources.Therefore,in large-scale SDN,how to balance the load among controllers has become a key topic for researchers in recent years..In the thesis,load balancing among multiple controllers is realized from two aspects: The first one is aiming at the controller deployment level,the existing controller deployment schemes have the problems of unstable connection between switch and controller and high network cost.A multiple controllers deployment method based on network cost optimization is improved.Firstly,the bidirectional matching lists of the controller and the switch are built according to the influences of the flow request rate of the switch and distances between switch and controller on controller and the influence of residual capacity of controller on switch.Secondly,the network overhead is taken as the optimization goal,and the simulated annealing algorithm is used to optimize the matching relationship,which finally achieve the load balance among multiple controllers and stable device connection.The simulation results show that the method can effectively reduce the network overhead and improve the stability of network equipment connection.The last one is aiming at the multiple domains division level,the existing multiple domains planning schemes have the problems of network communication extension and unreasonable multiple domains division of SDN.A multiple controllers deploymentmethod based on delay and load is improved.Firstly,the network topology is mapped to undirected graph,and the similarity matrix is constructed by using the distance between the switch and the controller,and then the random walk Laplace matrix is obtained.Next the undirected graph is cut by standard cut,and the indicator vector is introduced.Based on the idea of spectrum clustering,the problem of multiple controllers deployment is transformed into the problem of solving the characteristic vector of random walk Laplace matrix,and the improved k-medoids algorithm is used to cluster the row vector of the indicator vector matrix,which is composed of the characteristic vector.The simulation results show that the method can effectively reduce the network delay and divide the SDN domains reasonably.