Joint Latency and Reliability-Aware Controller Placement

In network architectures based on Software Defined Networking (SDN) the control plane (control logic) is separated from the network data plane (forwarding plane) while traditional network routers combine both. Software Defined networks facilitates a centralized networking system where a logical controller manages the global view of the network. In this paper, we first propose a new metric on the controller placement problem (CPP) that simultaneously considers the communication latency and communication reliability both between switches and controllers and between controllers. Reliability is considered for single-link failure. We model the problem of determining the optimal controller placement to provide low latencies in the control plane traffic. The objective of this study is to minimize the average accumulated latency by jointly taking into account the latency between controller to switches and inter-controller while optimizing their placement for achieving an optimal balance simultaneously. The optimization problem is formulated as a mixed-integer linear programming (MILP) model under the constraints of latency and reliability. We evaluated the performance of our proposed metric by using the Internet2 OS3E network topology. Different from previous work, we focus on the control traffic exchanged among controllers to synchronize their shared data structure. Results demonstrate that the proposed method is promising.