In software-defined networking (SDN), the SDN controller is the “brains” of the network, managing flow control to switches or routers (via southbound APIs) and to the applications and business (via northbound APIs). Essentially a single pane of glass from which network administrators have a clear overview of the entire network topology, the SDN controller enables automated network management, with network traffic directed according to centrally defined policies. When a change is needed, i.e. to handle higher traffic load, these policies can be changed centrally and the change is applied automatically to all relevant network devices. This minimizes the need to manually configure network resources.
Some common networking terms clearly explained