Research And Implementation Of Multi-Controller Load Balancing Strategy In Software Defined Networking

Software Defined Networking(SDN)realizes the separation of control layer and forwarding layer.Due to the limited management scale of a single controller,multiple controllers are usually deployed in large-scale networks to process message forwarding.However,the dynamic changes of network traffic have caused the problem of uneven load distribution among multiple controllers,which seriously affected network performance and caused serious waste of some controller resources.In view of the problem of SDN multi-controller load balancing in wide area networks,this paper researches the SDN multi-controller load balancing technology as well as proposes a switch migration strategy based on new flow density.What is more,it designs and implements an SDN multi-controller load balancing system.Main research contents and contributions of this paper are as follows:A SDN multi-controller load balancing strategy named SMBNFD(Switch Migration Based on New Flow Density)is proposed.First,edge switches controlled by the overload controller are added to a queue,and one is taken out as the initial node of the migration switch set.Then,the switches which are controlled by the overload controller and are adjacent to the set are filtered out.The switch which maximizes the new flow density of the set is selected to join it and we add the set as well as the neighboring controller to the list of migration alternatives.Continue to expand the set until the sum of Packet-In messages sent by the switches in the set per second is greater than the difference between the load of the overload controller and the average load of controllers.Empty the set and repeat the above steps until the queue is empty.Secondly,calculate and normalize two target values of controller load variance and average propagation delay of each alternative,which maps them to the range from 0 to 1.Combine the minimum and maximum values of each target in the list of migration alternatives into the positive and negative ideal solutions,and then calculate the Euclidean distance between each alternative and the positive ideal solution other than the Euclidean distance between each alternative and the negative ideal solution.Finally,the similarity between each alternative and the positive ideal solution is calculated according to the distance from the positive and negative ideal solutions,and the one with the largest similarity is selected as the final migration scheme.Experimental results show that this algorithm reduces the average transmission delay between controllers and switches while reducing the controller load variance.A SDN multi-controller load balancing system is designed and implemented based on SMBNFD.The load balancing system includes a load collecting module,a load calculating module,a delay calculating module,a strategy searching module,a migration decising module,as well as a switch migrating module.The management system contains a controller query module,a topology query module and a load management module.All of them have passed the system function test.