Introducing network planes

In a traditional switch/router, routing and packet forwarding is ideally done on the same device. What does this mean? Let's take a classic example of configuring a router. We might configure SSH for managing the router and later configure routing protocols to exchange the routes with its neighbors. All these common tasks are done specifically on the same hardware device. So, in a nutshell, each and every router will take a forwarding decision based on the configuration of routers. The power of software-defined networking is decoupling the forwarding and control plane functionality to a centralized device called a controller and the end result is the controller maintaining the forwarding information and taking decisions rather than going via hop by hop in the traditional way. As shown in the following figure, the three functional planes of a network are the management plane, the control plane, and the data plane:

The three functional planes of a network...