Minimal Coverage Model for Fault-Tolerant Controller Placement in Software Defined Networks

In order to deploy fault-tolerant Software-Defined Networks(SDN), many controllers must be physically distributed among different network devices. However, a large number of controllers bring huge costs, which limits severely the application of the fault-tolerant control plane to the real networks. In order to solve the above problems, the fault-tolerant control plane is analyzed and a mathematical model that covers all switches using the least number of controllers is constructed. Then, a heuristic controller placement algorithm based on the local search strategy is proposed to avoid the local optimal solution. The experimental results show that compared with other algorithms, the proposed algorithm can effectively reduce the number of required controllers while ensuring network fault tolerance requirements in different scale networks.