Let's start with an honest statement: OpenFlow is not SDN, and SDN is not OpenFlow. People often interchanged the two terms in the early days, but they are certainly not the same. OpenFlow is a very important building block of SDN, and many credit it to be the origin of the SDN movement. OpenFlow originally started at Stanford University as a research project, which eventually jump-started the startups of Nicira and Big Switch Networks. Nicira was acquired by VMWare and is now part of the company's network-virtualization product line. Big Switch Networks leads a number of OpenFlow open source projects such as Floodlight Controller, Switch Light OS for bar-metal Ethernet switches, and Switch Light vSwitch for virtual switches. ...