Software-defined networking (SDN) is a network management technique that centralizes control of network appliances in software. SDN makes network management easier in two ways: it allows networks to be administered as a whole, rather than on a device-by-device basis, and it allows for administrative work to be automated and conducted on the fly in response to changing network needs and conditions.
The first SDN system to gain traction was the open source OpenFlow protocol, which rolled out in 2011. There are now a number of possible SDN models, each providing significant benefits when compared to traditional networking.
