A system for frame peeking at a node of a data network includes a controller, a forwarding engine and an interface. The interface includes a subscribe/publish interface for allowing the controller to request (or subscribe) to receive a selected portion of a flow (a group of packets), and a facility access interface for allowing the controller to control each frame or packet. By providing only a selected portion of received packets to the controller rather than the entire packet, the controller can operate on the incoming data without significantly degrading the forwarding performance of the system. Frame peeking can also be used in an end-system to minimize packet processing.