The term Software Defined Network or SDN is one of the many emerging technologies that has been revolutionizing the concept of networking. By decoupling the Data and Control plane, it has lot to offer in the field of information technology. The Control Plane is regarded as the brain of the network, which is a centralized unit of SDN network along with the controller. Selection of SDN controller is one of the most important task in designing of SDN based Network. Through this paper, we intend to compare two eminent controllers: OpenDayLight and ONOS controllers, according to their efficacy. Mininet, which is meant for demonstrating the simulation of switching and end-devices, has been taken into account. Apart from this, we have used Wireshark Packet Analyser and iperf, which provides real-time traffic flow between Mininet and the Controller. Performance of the controller plays an important role in the network and answers question like how it is going to perform. There are the various factors that helps in evaluating the performance of SDN controller. After analysing, it has been found that ONOS has better performance, with respect to throughput, TCP Window Scaling, TCP/UDP Bandwidth, Burst Rate, Jitter, Goodput, TCP Stevens Graph, Round Trip Time (RTT), and its usability. This paper helps us to understand performance abilities between ONOS and ODL in medium-to-large scale SDN Networks.