Stream Reservation Protocol (SRP) is an enhancement to Ethernet that implements admission control. In September 2010 SRP was standardized as IEEE 802.1Qat which has subsequently been incorporated into IEEE 802.1Q-2011. SRP defines the concept of streams at layer 2 of the OSI model. Also provided is a mechanism for end-to-end management of the streams' resources, to guarantee Quality of Service (QoS).
SRP is part of the IEEE Audio Video Bridging (AVB) / Time-Sensitive Networking (TSN) group of standards. The SRP technical group started work in September 2006 and finished meetings in 2009.
SRP registers a stream and reserves the resources required through the entire path taken by the stream, based on the bandwidth requirement and the latency which are defined by a stream reservation traffic class.
Listener (stream destination) and Talker (stream source) primitives are utilized. Listeners indicate what streams are to be received, and Talkers announce the streams that can be supplied by a bridged entity. Network resources are allocated and configured in both the end nodes of the data stream and the transit nodes along the data streams' path. An end-to-end signaling mechanism to detect the success/failure of the effort is also provided.
SRP "talker advertise" message includes QoS requirements (e.g., VLAN ID and Priority Code Point (PCP) to define traffic class, rank (emergency or nonemergency), traffic specification (maximum frame size and the maximum number of frames in a traffic class), measurement interval, and accumulated worst-case latency).