RSVP refers to Resource Reservation Protocol, a protocol used in VoIP to manage Quality of Service or QoS. QoS pertains to a set of algorithms that aim to provide different quality levels to different types of network traffic. RSVP is a part of the IIS or Internet Integrated Service model, which provides controlled-link sharing and real-time services.

Essentially, RSVP functions by making a request to reserve a specific bandwidth and latency. These resources are requested by the RSVP through the VoIP telephone call. RSVP makes this request to every network device between the two VoIP units. Using RSVP, an individual can reserve bandwidth prior to a specific program via the Internet. He is then able to receive the program at a higher rate.

RSVP is a protocol that supports unicast (one source to one receiver) and multicast (one source to many receivers) signaling. It is capable of setting up and maintaining information about reservation states. These pieces of information are located at each router through which a specific stream of data is being transferred.

RSVP is used by a number of systems for specific purposes. Host computers use RSVP to request Qualities of Service from the network. The Quality of Service will then be used by the host for specific application data streams. Routers also use RSVP to request Quality of Service requests to all nodes where the data flow will pass through. This in turn allows routers to establish and maintain the proper network state. Through RSVP, each node on the path of the data flow will reserve an amount of resource from the system.