Balance-Based SDN Controller Placement and Assignment with Minimum Weight Matching

Given a software defined wide-area network (WAN), how to choose location of controllers and how to assign the controllers to forwarding devices are two significant issues. Previously, most of solutions to these two problems focus on the propagation delay but ignore the balance of controllers, because it's difficult to solve them with consideration of balance of controllers. In this paper, a novel approach which can efficiently and accurately solve SDN controller placement problem and assignment problem for WAN is proposed. The SDN controller assignment problem is formulated as a minimum weight matching of bipartite graph, and it also considers the balance of controllers. The Kuhn- Munkres algorithm based solution is used to find optimal matching between switches and controllers. Then, a genetic algorithm is proposed to solve the controller placement problem based on the controller assignment scheme. The performance shows that our approach has good performance in reducing the average propagation delay between SDN forwarding devices and controllers, and it also achieves better balance of controllers.