A Brief Introduction To OpenFlow, November 14, 2011 OpenFlow is a specification now managed by the Open Networking Foundation, which defines the functions and protocols used to centrally manage switches via a centralized controller.
While OpenFlow has a centralized controller, that doesn't mean that each new flow has to result in a controller lookup. If a new flow matches an existing rule, it will be processed according to that rule's actions. Rules can be pre-populated, reducing the number of lookups that occur. Intelligent policy development should mean a reduced number of controller lookups. In addition, rules have a time to live associated, so if the switch is disconnected from the controller for some reason, it can still process existing and new flows. Only those flows that result in a controller lookup would fail.
Controller technology is not new either. Enterprises have been using controller-based wireless and network access control for years successfully.