Controller-based network fabric

As we come out of the legacy hardware era in which each physical path was connected and designed to take traffic from one point to another, and where a packet had limited availability to reach from one device to another, SDN is ensuring that we have a network fabric for our data to reach between different sources and destinations.

A network fabric is a collection of different network devices connected to each other by a common controller ensuring that each component in the network is optimized to send traffic among each of the nodes. The underlying switch fabric, which is a physical switchboard with ports (like Ethernet, ATM, and DSL), is also controlled and programmed by a controller which can ensure (by creating a path or specific port(s)) that a particular type of data can traverse through to reach its destinations.

In a typical network design we have Layer 2 (or switching domains) and Layer 3 (or routing domains). If we do not have a controller-based approach...