Research On Strategy Of Controller Deployment In Software Defined Network

Software Defined Network(SDN)is a new open hierarchical architecture,which breaks the vertical structure of traditional network and realizes the programmability of network,thus improving the flexibility and controllability of network.Early SDN implementations relied on a single controller.However,with the spread and application of SDN in different scale networks,single controller is faced with problems such as insufficient performance,single point failure and poor scalability.Distributed multi-controller deployment mode is one of the effective ways to solve this problem,but how to deploy multi-controllers reasonably is a problem to be solved.In this thesis,the controller deployment strategy is designed for WAN and data center network scenarios respectively.For wide area SDN networks,the communication delay between the controller and the switch is the primary consideration,because the controller needs to respond quickly to network incidents and send flow tables to the switch in time.At the same time,as the core of the whole SDN network architecture,the reliability of the control layer cannot be ignored.Considering that link failure may lead to a sharp deterioration of the communication delay between controller and switch and the failure of some control paths,the worst-case delay between controller and switch is taken as a measure of delay,and the number of control path failures caused by single link failure is taken as a reliability measure.The effects of single link failure on the two performance indicators under different controller numbers are studied.At the same time,two indicators are modeled as optimization objectives,and a heuristic controller deployment algorithm based on particle swarm optimization is proposed.The effectiveness of the proposed strategy is verified by experimental simulation.Compared with the wide area SDN network,the data center network is smaller and the forwarding devices in the network are more centralized.The communication delay between the controller and the switch is too small to be neglected.At this time,the reliability of the whole control layer becomes the focus of research.For data center network,a master and backup controller deployment strategy based on reliability is proposed.In order to ensure the reliability of the control nodes,each switch in the network should be connected with two controllers.At the same time,the correlation and difference between master and backup control paths are taken as the research focus,and the reliability of control paths is ensured by defining a reliability factor.A master-backup controller deployment algorithm is proposed for the model established.The simulation results show that the proposed strategy is effective,and the proposed algorithm is superior to other algorithms in network reliability.