Many people don't understand the difference between OpenFlow and software defined networking (SDN). This isn't surprising because the two technologies are closely related. However, they aren't interchangeable. OpenFlow is protocol that configures network switches using a process like an API. SDN is a term that describes providing programmable interfaces within a network infrastructure to enable a high degree of automation in provisioning network services. The SDN term is being abused by marketers who want to apply it to a wide range of technologies.

In fact, SDN can be explicitly defined. There are three architectural layers to an SDN network: the physical network, the SDN applications and the SDN controller. Let's look at each.

Physical Network. The lowest layer consists of the physical devices in your network that form the foundation of all IT infrastructure. We use the term "switch" because OpenFlow changes the way Ethernet switches work.