RSVP: Resource ReSerVation Protocol
RSVP is a resource reservation setup protocol designed for quality
integrated services on Internet. RSVP is used by a host to request specific
qualities of service from the network for particular application data streams
or flows. RSVP is also used by routers to deliver quality-of-service (QoS)
requests to all nodes along the path(s) of the flows and to establish and
maintain state to provide the requested service. RSVP requests will generally
result in resources being reserved in each node along the data path.
RSVP requests resources in only one direction. Therefore, RSVP
treats a sender as logically distinct from a receiver, although the same
application process may act as both a sender and a receiver at the same time.
RSVP operates on top of IPv4 orIPv6 , occupying the
place of a transport protocol in the protocol stack. However, RSVP does not
transport application data but is rather an Internet control protocol,
like ICMP , IGMP , or routing
protocols. Like the implementations of routing and management protocols, an
implementation of RSVP will typically execute in the background, not in the
data forwarding path.
RSVP is not a routing protocol by itsself; RSVP is designed to operate
with current and future unicast and multicast routing protocols. An RSVP
process consults the local routing database(s) to obtain routes. In the
multicast case, for example, a host sends IGMP messages to join a multicast
group and then sends RSVP messages to reserve resources along the delivery
path(s) of that group. Routing protocols determine where packets get forwarded;
RSVP is only concerned with the QoS of those packets that are forwarded in
accordance with routing.
Protocol Structure - RSVP Resource
ReSerVation Protocol
4
|
8
|
16
|
32 bit
|
Version
|
Flags
|
Message type
|
RSVP checksum
|
Send TTL
|
(Reserved)
|
RSVP length
|
|
- Version -- The protocol version
number, the current version is 1.
- Flags -- No flag bits are
defined yet.
- Message type -- Possible values
are: 1 Path, 2 Resv, 3 PathErr, 4 ResvErr,, 5 PathTear, 6 ResvTear, and 7
ResvConf.
- RSVP checksum -- The checksum.
- Send TTL -- The IP TTL value
with which the message was sent.
- RSVP length -- The total length
of the RSVP message in bytes, including the common header and the variable
length objects that follow.
