Rule Placement and Switch Migration-based Scheme for Controller Load Balancing in SDN

In software-defined networks, due to the limited flow table capacity, unreasonable rule placement will cause the flow table overflow problem. These flows without flow rules installed need to be processed by controller, which increases and even unbalances controller load. Based on the average packet end-to-end delay, we propose a rule placement and switch migration-based scheme for controller load balancing. In the routing and rule placement phase, the Cost-Aware Routing (CAR) algorithm takes into account the flow table occupancy while utilizing the installed rules to alleviate flow table overflow and preliminarily balance the controller load. In the switch migration phase, the Benefit-Cost Switch Migration (BCSM) algorithm obtains the migration option with the maximum total benefit. Numerical results show that the CAR algorithm reduces and balances controller load to achieve lower delay than Random and FlowStat. And the BCSM algorithm balances the controller load and reduces packet delay than SMCS and ESMLB.