RSVP (Resource Reservation Protocol) is a set of communication rules that allows paths on the Internet to be reserved for the multicast (one source to many receivers) transmission of video and other high-bandwidth messages.

With RSVP, people who want to receive a particular Internet "program" (think of a television program broadcast over the Internet) can reserve bandwidth through the Internet in advance of the program and be able to receive it at a higher data rate and in a more dependable data flow than usual. When the program starts, it will be multicast to those specific users who have reserved routing priority in advance.

Resource Reservation Protocol (RSVP) is a transport layer protocol used to reserve network resources and enable running Internet applications to gain quality of service (QoS).

Some old networks were required to provide reliability of data. However, in today's era of network systems, time is often more important than reliability. Instead, RSVP is supported by a QoS network, providing both the quality of service and insured data.

Working of RSVP

• Let's assume that a particular video program is to be multicast at a certain time on Monday evening. Expecting to receive it, you send an RSVP request before the broadcast (you'll need a special client program or perhaps your browser includes one) to allocate sufficient bandwidth and priority of packet scheduling for the program. This request will go to your nearest Internet gateway with an RSVP server.

• It will determine whether you are eligible to have such a reservation set up and, if so, whether sufficient bandwidth remains to be reserved to you without affecting earlier reservations. Assuming you can make the reservation and it is entered, the gateway then forwards your reservation to the next gateway toward the destination (or source of multicast). In this manner, your reservation is ensured all the way to the destination. (If the reservation can't be made all the way to the destination, all reservations are removed.)

The two important types of RSVP messages are:

1. Path messages:

• The receivers in a flow make the reservation in RSVP, but the receivers do not know the path traveled by the packets before the reservation. The path is required for reservation To solve this problem the RSVP uses the path messages.

• A path message travels from the sender and reaches to all receivers by multi-casting and path message stores the necessary information for the receivers.

2. Resv messages:

After receiving path message, the receiver sends a Resv message. The Resv message travels to the sender and makes a resource reservation on the routers which supports for RSVP.