The instruction set in software-defined networking (SDN) routers and switches. Governed by the Open Networking Foundation (www.opennetworking.org), OpenFlow devices are programmed by one or more OpenFlow controllers residing in servers in the network. See software-defined networking. OpenFlow History Standardized in 2009, OpenFlow responsibility moved to the OFN in 2011 from Stanford University, where it was invented. Nox, Beacon and Floodlight are some of the first OpenFlow controllers that emerged from the early work. Nox is considered the first (www.noxrepo.org), and Beacon and Floodlight share a common heritage. Both written in Java, Beacon's focus is research applications, while Floodlight is intended as a production deployment (http://openflow.stanford.edu/display/Beacon and www.projectfloodlight.org).