Paper Title
SDN Controllers Comparison

This paper presents about Software Defined Network (SDN) which is a new networking paradigm where the architecture moves from the traditional fully distributed model to a more centralized approach. Software Defined Networking (SDN) is a new networking arch type and is also the most discussed topic of networking technology of recent years as it brings a lot of new capabilities and allows to solve many hard problems of legacy networks. This approach is also characterized by the separation of the data and control planes. The SDN proposed an approach which involves in moving network's intelligence out from the packet switching devices and putting it into a centralized logical controller. Controllers act as the control point for networks to manage flow between the Application layer and the Data layer through the Southbound API's and the Northbound API's to create a more flexible network. The forwarding decisions are primarily done in the controller and then moves down to the switches where it directly executes the logical decisions. Advantages like global controlling and viewing the whole network at a time are being provided, which is helpful for automating several tasks like Operation of a network, better server and network utilization, etc. Index terms - SDN Controller; Software Defined Network.