Research On Multi-Controller Load-balancing Technology In Software-Defined Networking

OpenFlow-based Software-Defined Networking(SDN)is a new type of network architecture that effectively solves the problems of complex equipment management,difficult network configuration and slow deployment of new network services in traditional networks.It greatly improves the openness of the network and the flexibility of managing and controlling network devices and traffic by separating forwarding control,employing centralized management control and providing open programmable interfaces.There are some inherent challenges and problems in the SDN control plane of a typical single controller:first,the reliability and scalability of the performance bottleneck of the control plane;second,the safety problem of single point failure of a single controller.The distributed control plane of SDN multi-controller improves the reliability,scalability and security of the control plane with independent management and control of network equipment and traffic in different areas.However,the static matching between the controller and the switch and the difference of traffic patterns in different network domains lead to the impossibility of load-balancing among multiple controllers,Multi-controller load-balancing based on switch migration has become an important research topic.This thesis focuses on the problem of extensive overload detection mechanism and load-balancing processing with low-efficiency and high-cost in SDN multi-controller load-balancing,and proposes two SDN multi-controller load-balancing schemes from different aspects:1)SDN Multi-Controller Load-Balancing based on Response Time(SMCLBRT).The scheme monitors and calculates the average response time of the controller to Packet-in message requests in real time.The appropriate response time threshold is selected according to the characteristics of the average response time changing with the processing load of the controller.It can achieve more accurate and fine-grained judgment of the controller overload.For the problem of multiple controllers overloading at the same time,this scheme realizes the simultaneous processing of multiple overload controllers in one load unbalance judgment,and improves the efficiency of load-balancing processing of multiple overloaded controllers.The simulation results show that SMCLBRT can effectively balance the SDN control plane load,reduce the network delay with a lower load-balancing cost,and a higher overall balance rate.2)SDN Multi-Controller Load-Balancing based on Flow Prediction(SMCLBFP).This scheme combines Taylor's formula and historical real-time load value to judge the controllers that may be overloaded by the prediction algorithm,and preprocesses them for load-balancing during switch migration,so as to avoid overload controllers and their impact on network services as far as possible.At the same time,the method of "overload preprocessing" instead of "overload post-processing" can effectively reduce the migration cost of multi-controller load-balancing.The simulation results show that SMCLBFP can effectively balance the SDN control plane load,reduce the controller overload rate of SDN control plane.It can implement pre-processing of the overload controller and reduce the processing cost after the control plane is unbalanced.