Flow setup time aware minimum cost switch-controller association in Software-Defined Networks

Software Defined Networks (SDN) emerged as a new network paradigm to address the customization and flexibility problems in traditional computer networks. In SDNs, a logical centralized programmable controller manages the whole networks by installing rules onto switches. It is widely regarded that one controller is restricted on both performance and scalability. To address these limitations, pioneering researchers advocate deploying multiple controllers in SDNs where each controller is in charge of a set of switches. This raises the switch-controller association problem on one switch shall be managed by which controller. In this paper, we specially investigate minimum cost switch-controller association (MC-SCA) problem on how to minimize the number of controllers needed in an SDN while guaranteeing the flow setup time. A quadratic integer programming model is first proposed and then transformed into an equivalent integer linear programming model to describe the MC-SCA problem, which is then proved as NP-Hard. We further propose a heuristic algorithm and extensively prove its high efficiency via simulations.