What Is RSVP?
RSVP is a signaling protocol that makes reservations of resources (bandwidth and
so on) for client applications to guarantee a certain QoS. It is considered a signaling
protocol because these reservations are negotiated by communication
between end stations. Furthermore, it is an out-of-band signaling protocol. RSVP
packets are not used to transmit bulk data; they coexist on the network with other
packets and are used to reserve resources for typical IP packets or, more specifically,
the IP packets that make up the flows that are to get specialized QoS. For
this reason, RSVP seems like a natural choice when implementing AVVID solutions—
since your voice and video traffic have specific requirements, including that
for bandwidth—whereas your data traffic might be a bit more forgiving.
RSVP makes reservations of resources for data flows across a network.These
reserved flows are usually referred to as sessions. A session is defined as packets
having the same destination address (unicast or multicast), IP protocol ID, and
destination port. Resources could be considered such things as allocated bandwidth,
CPU cycles, or queuing priority. Clients use RSVP to request a guarantee
of QoS across the network. Routers participate in RSVP by allocating resources
to particular flows, or denying resources if there are none available, and by forwarding
RSVP information to other routers.