In recent years, SDN has gained a lot of popularity. There is a basic principle behind the growth of SDN which states the separation of the control plane from the data plane. In the data plane, all the network devices constitute whereas in the control plane the core element is situated known as SDN controller. The controller is the integral element of SDN based network. It manages the entire network and maintains the overall functionality. In the last years, there are many SDN controllers came into existence. This paper aims to provide the experimental comparison among the seven most used SDN controllers both in research and industry. The comparison and experimentation analysis is carried out in an emulator tool known as Mininet with four different network topologies (single, linear, tree, custom) and the varied number of nodes (10, 50, 100, 500, 1000). The parameters for comparison are Round Trip Time (minimum, maximum, average) and standard deviation. This paper will prove to be beneficial for the researchers and industry people who are making use of these SDN controllers, it will help them to choose a particular controller and analyze their performance against the selected network topologies and number of hosts.