ed from https://www.sdxcentral.com/sdn/definitions/sdn-controllers/ What Is Ryu Controller? (n.d.). Retrieved from https://www.sdxcentral.com/sdn/ definitions/sdn-controllers/open-source-sdn-controllers/what-is-ryu-controller/ Wilkins, S. (2014, November 25). A Guide To Software Defined Networking (SDN) Solutions - Software DefinedNetworking. What It Is And Isn't. Retrieved from http:// www.tomsitpro.com/articles/software-defined-networking-solutions,2-835.h Downloaded 4/15/2022 9:44:49 AM Nova Southeastern University IP Address: 137.52.76.29 Chapter 5 The Heart and Brain of SDN: SDN Controllers Pranav Arora University of Petroleum and Energy Studies, India ABSTRACT The chapter explores the various types and functionalities of controllers present in the field of software-defined networking. It is responsible for providing a bridge between various application interfaces. It enables smart networking and is solely responsible for having an authority over the network. It takes input from one API, processes it, and returns output for the high-level interface or API. They instruct the switch as to what functions to perform and can be of two types: either pure or hybrid. The controller at the central layer performs all the functions of the "evergreen" existing switches. The data plane of the router is solely the foreground for the switch to apply all its powers, while in hybrid switch software-defined networking and existing technologies work hand in hand. An administrator can build up the SDN tools to manage the traffic, whereas the existing network protocols progressively move the various incoming packets onto the network. This engenders hybrid network. Here the existing and SDN technologies or switches, work under the similar conditions. INTRODUCTION The need of the present scenario is to give a general overview of the industry-specific as well as open source SDN technologies. As the IT industry is still thriving and is ambiguous of the role of software defined networking in the market, the solutions which are presen