SDN controllers are integral to NV and often included in the leading NV platforms. As the central control point for the virtualized network, an SDN controller can simplify and automate the orchestration of the network, enabling organizations to improve the intelligence, agility, scalability and cost-effectiveness of their overall infrastructure. It does this by using the programmable control APIs that are exposed in an SDN environment; these APIs enable the controller to communicate to the switches/routers ‘below’ (via southbound APIs) and applications/services ‘above’ (via northbound APIs).
As SDN fever took hold in the 2010-2012 timeframe, the SDN controller market landscape started to expand. This included the ODL project from the Linux Foundation, which was first announced in 2013 and got its first release, named Hydrogen, in 2014. At the same time, many network vendors scrambled to put together an SDN strategy – which included picking a controller. Many vendors opted to develop their own commercial controller solutions, either basing it on an open source offering such as ODL or by building something different. The degree to which networking vendors use open source code such as ODL and market an SDN business model can vary greatly.
To date, ODL appears to have the most momentum of the controller ecosystem. ODL has more than 100 deployments, including Orange, China Mobile, AT&T, T-Mobile, Comcast, KT Corporation, Telefonica, TeliaSonera, China Telecom, Deutsche Telekom, and Globe Telecom.
Contributing individuals recently exceeded 500, vendors contributing including Big Switch Networks, Cisco, Ericsson, HPE, NEC, and many others, making it one of the fastest growing open source projects ever. The fourth release, Beryllium, came out earlier this year. The controller supports a wide variety of protocols including OpenFlow, Netconf, BGP, PCEP, and OVSDM.