Before a session can be created, the session identification (DestAddress, ProtocolId [, DstPort]) must be assigned and communicated to all the senders and receivers by some out-of-band mechanism. When an RSVP session is being set up, the following events happen at the end systems.
There are several synchronization considerations.
The receiver may simply choose to ignore such error messages, or it may avoid them by waiting for Path messages before sending Resv messages.
A specific application program interface (API) for RSVP is not defined in this protocol spec, as it may be host system dependent. However, Section 3.11.1 discusses the general requirements and outlines a generic interface.