Resolving Load Imbalance State for SDN by Minimizing Maximum Load of Controllers

Abstract

This paper proposes a scheme to practically resolve the load imbalance state for orchestrated multiple controllers architecture in software-defined networks (SDN). Multiple controllers architecture is crucial to SDN implementation in large scale networks because this architecture provides efficient performance for end-to-end services, such as reliability and scalability in SDN networks. However, when there are multiple SDN controllers in the network, a load imbalance state may occur. The load imbalance problem can notably degrade service level in some parts of the network because the SDN controllers in those network areas have much higher amount of processing load. Existing works solved the load imbalance problem by migrating the load to multiple SDN controllers in order to maintain an acceptable level of load in all SDN controllers. Nevertheless, most of these works did not consider propagation delay and processing time in their load definition. In large-scale networks, high propagation delay is likely to cause late response from the SDN controller, which may result in a degraded performance in the SDN networks. In this paper, a new load balancing scheme is proposed. The proposed scheme is formulated as an integer linear programming problem (ILP). It defines SDN controller’s load based on propagation delay, processing time at the controller and the number of request messages in order to provide an accurate representation of load in practical environments. Generally, ILP may take a long period of time to process. Therefore, a heuristic algorithm that bases on the proposed load balancing scheme is also developed to provide shorter processing time. Computer simulations and practical implementation in Pica8 switch show that the proposed scheme reduces the average maximum load by at least 9.85%, compared to a conventional scheme.