Does SDN require a controller?
A specialized SDN controller, whether or not it uses the OpenFlow protocol, is not required to implement a software-defined network. A controller enables SDN functionality by allowing network users to "control" or modify network flows independently from physical network devices.
SDN architectures are taking many different approaches, and technology vendors will have a unique take on how to implement SDN, particularly using their own company's product lines.
In the OpenFlow community, for example, with standards developed by the Open Networking Foundation, the answer is yes. Most OpenFlow implementations will include an OpenFlow controller from providers that include Big Switch, HP, IBM, NEC, DELL (and many others), or via open source software.
Other SDN options don't necessarily include a controller. VMware 's Nicira acquisition, for example, will enable the company to implement SDN protocols in its vSwitch software, which does not require an OpenFlow controller. Cisco' s SDN architecture -- Open Network Environment (ONE) -- supports OpenFlow, but Cisco does not require an SDN controller, preferring to embed intelligence in its Ethernet switches and network management software. Similarly, Brocade supports OpenFlow, but does not require its use. Embrane provides a different example of SDN functionality that does not require OpenFlow or a controller. Embrane's Heleos platform has Layer 4-7 software including load balancers, firewalls, VPNs and WAN optimization. ADARA, Pertino and LineRate are additional examples of SDN start-ups that do not require OpenFlow or a controller.
Dig Deeper on SDN control plane
Related Q&A from Lee Doyle
The OpenFlow protocol isn't required for SDN, although the Open Network Foundation recommends it, which means networking vendors have options.continue reading
SDN is valuable, but uses extend to other parts of the network for increased network flexibility, dynamic traffic flow, decreased latency and QoS.continue reading
An SDN controller, with or without OpenFlow, is not required for a software-defined network, and SDN architecture vendors take different approaches.continue reading
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