Research On Controller Placement Tactics Based On Software Defined Network

The Internet is an indispensable infrastructure in people's production and life.With the growth of its scale,the original network system has been unable to meet the needs of development.Therefore,the Software Defined Network(SDN)technology arises at the historical moment and becomes one of the main research directions of the new generation of Internet.The emergence of multi-controller architecture solves the scalability problem of the control layer of classic SDN architecture in large-scale network.In a multi-controller architecture,since the task of generating forwarding rules and populating them into the switch is delegated to the controller,the performance of the network is largely determined by the placement of the controller.In addition,the deployed controller will inevitably fail in the operation process,which will cause serious impact on the whole network if it is not handled in time.Therefore,this thesis mainly studies the deployment of controllers in SDN network and the treatment methods when the deployed controllers fail,as follows:(1)A multi-controller deployment algorithm based on subnet partition is proposed.Firstly,the improved spectral clustering algorithm divides the network into a specified number by measuring the total delay and the controller load and finds the optimal controller deployment point in each subnet.Secondly,the outlier detection algorithm is used to detect whether there are isolated nodes.If there are,the proximity method is used to redistribute to ensure that all the switch nodes are assigned to the corresponding controller.Then,the load balancing algorithm is added to ensure that the load difference between each controller is not too big when all controllers are not loaded.Finally,the simulation experiment proves that the algorithm can effectively divide the network and balance the load between controllers while ensuring the total network delay is low.(2)In order to avoid the failure of the deployed controller changing the subnet structure and affecting the reliability of the deployment strategy,a controller fault handling strategy based on delay and load balancing was proposed.Firstly,a timeout mechanism is adopted to detect the control node.If no response from the controller is received by all switches in the region,the controller is judged to have a fault.Secondly,the switch nodes in the fault region are transferred to other normal controller domains by using the time-delay and loadconstrained switch migration algorithm,and the new control relationship is transformed to realize the fault recovery in the control domain.Finally,the simulation results show that this strategy can find and deal with the controller fault effectively and restore the network communication in time.In addition,for the isolated switch problem caused by link failure or other factors,a method based on the Link Layer Discovery Protocol(LLDP)message processing is proposed.