Abstract: Software Defined Network (SDN) is an emerging technology in the field of cloud computing and networking, which simplifies the tasks of the network administrators, by providing centralized management of networking devices,by separation of data and control planes. Various cloud computing environments, enterprise data centres and service providers are utilizing this essential feature. In this work we have employed mininet to illustrate the aptness of SDN for different scalability. We examined the performance of SDN controllers such as Ryu, POX and Floodlight controllers utilizing mininet and qperf, a network performance measurement tool. During this study we have utilized different network topologies with different number of switches and hosts to assess the performance of the controllers. The performance parameters used were network latency and bandwidth. Experimental results demonstrated that Ryu provides better bandwidth and minimum latency in all the topologies, except single topology. POX controller outperformed Ryu and Floodlight controllers in single topology Keywords: SDN, Mininet, Ryu, POX, Floodlight, qperf.