Strategy On Multi-controller Placement And Switch Migration For Load Balancing In SDN

Software Defined Network(SDN),which separates forwarding and controlling functions about traffic,is more flexible.For this reason,SDN has quickly been used in small scale networks.The effect of SDN in the network like data center or company WLAN is remarkable.In the environment of increasing network scale,a single central controller in SDN can't meet the demand of rapid increase of traffic,so multi-controller architecture comes into being and is used to control the traffic of the network.However,the unreasonable design in the initial stage of constructing SDN network and the volatility of traffic during the operation of the SDN network will cause the phenomenon of unbalanced load in the multi-controller architecture.In response to this issue,this article conducts research from two aspects:the first one is multi-controller placement;the other one is switch migration.The research is reflected from the following three aspects:(1)In the initial stage of constructing SDN network,existing method about subdomain division of the controllers can't handle the problem of the time delay and load balancing when placing multiple controllers in SDN.An algorithm for placing multiple controllers has been proposed to solve this problem.This work begins with deciding the position of the controllers.Then,we determine the number of the switches managed by the subdomain of the controller.After that,we start to construct the subnet of the network by adopting the way of the closest distance.The experimental results demonstrate this algorithm could bring down the time delay of the network while ensure more balanced load performance.(2)In allusion to the issue that the optimal placement position of the controllers in the network is unknown,a scheme based on the optimized PSO algorithm and the multi-controller placement algorithm is proposed.Firstly,an optimized PSO algorithm,which introduces the convergence factor,is used on ameliorating the weakness of PSO about the tardy convergence speed.Then,the optimization goal in the model about placing the controllers is taken as the fitness of the optimized PSO algorithm.After that,the scheme based on the optimized PSO algorithm and the multi-controller placement algorithm is used to iteratively optimize the optimal position of the controllers in SDN.The experimental results demonstrate this scheme could determine the optimal position of the controllers in the network topology and could have better consequent in the running time of the algorithm.(3)In view of the distributed architecture,a switch migration decision algorithm which solves the question of volatility about traffic in the dynamic SDN network is proposed.When the load of the controller in the cluster exceeds the critical threshold,the appropriate switches are selected in the subdomain of the controller and migrated to the subdomain of the underload controller.At the same time,the selection of the migrated switchs and the migrating process of the switchs are optimized.The experimental results demonstrate this algorithm could effectively bring down the response time of the controller.More importantly,this algorithm could counterpoise the load between the clusters in SDN.