COPS (Common Open Policy Service Protocol) is a proposed standard protocol for exchanging network policy information between a policy decision point (PDP) in a network and policy enforcement points (PEPs) as part of overall Quality of Service (QoS) - the allocation of network traffic resources according to desired priorities of service. The policy decision point might be a network server controlled directly by the network administrator who enters policy statements about which kinds of traffic (voice, bulk data, video, teleconferencing, and so forth) should get the highest priority. The policy enforcement points might be routers or layer 3 switches that implement the policy choices as traffic moves through the network. Currently, COPS is designed for use with the Resource Reservation Protocol (RSVP), which lets you allocate traffic priorities in advance for temporary high-bandwidth requirements (for example, video broadcasts or multicasts). It is possible that COPS will be extended to be a general policy communications protocol.
In operation, RSVP makes two determinations when an RSVP request arrives at a router or layer 3 switch. First, it determines whether there are enough resources to satisfy the bandwidth reservation request. If there are, RSVP determines whether the user is authorized to make the reservation. The first determination is known as the admission control decision; the second is known as the policy control decision. COPS allows the router or layer 3 switch to communicate with the policy decision point about whether the request for the bandwidth reservation should be permitted. Without COPS, all resources would be reserved on a first come-first served basis only, and one or more requesters could easily take all the bandwidth.
The current COPS protocol is specified in an Internet-Draft working document of the Internet Engineering Task Force (IETF).