The different states

An RSVP process has three different RSVP states, plus an additional state for traffic control, described in table .

Table: RSVP states

State	Description
Path state	Records information given by Path messages
Reservation state	Holds reservation requests
Blockade state	Records reservations failing Admission Control
Traffic control state	Holds the reservations specification handed to Traffic Control

When a Path message is received by a node, an entry is added in the path state. When a reservation is made with a Resv message, an entry describes it in the reservation state.

Now suppose that a reservation $Q_{1}$ is made on a node $\EuScript{N}$ and then fails Admission Control on another node $\EuScript{M}$. If another receiver wants to make a reservation $Q_{0}$ ($Q_{0} < Q_{1}$), this reservation may be merged at node $\EuScript{N}$ with $Q_{1}$ so that the reservation requested at node $\EuScript{M}$ will fail, even if $\EuScript{M}$ would have made the reservation $Q_{0}$. In order to avoid this ``killer reservation problem'', a reservation's failure is recorded in the blockade state thanks to Resv Error messages, and then merging will take this into account.

Even if it is not part of the specification, an RSVP implementation needs an additional state: the traffic control state. It holds the information about reservations handed to Traffic Control for each outgoing interface.