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- gatekeeper discovery (GRQ)
- endpoint registration
- endpoint location
- admission control
- access tokens
The RAS messages are carried on a RAS channel that is unreliable. Hence, RAS message exchange may be associated with timeouts and retry counts.
Gatekeeper Discovery
The gatekeeper discovery process is used by the H.323 endpoints to determine the gatekeeper with which the endpoint must register. The gatekeeper discovery can be done statically or dynamically. In static discovery, the endpoint knows the transport address of its gatekeeper a priori. In the dynamic method of gatekeeper discovery, the endpoint multicasts a GRQ message on the gatekeeper's discovery multicast address: "Who is my gatekeeper?" One or more gatekeepers may respond with a GCF message: "I can be your gatekeeper."
Endpoint Registration
Registration is a process used by the endpoints to join a zone and inform the gatekeeper of the zone's transport and alias addresses. All endpoints register with a gatekeeper as part of their configuration.
Endpoint Location
Endpoint location is a process by which the transport address of an endpoint is determined and given its alias name or E.164 address.
Other Control
The RAS channel is used for other kinds of control mechanisms, such as admission control, to restrict the entry of an endpoint into a zone, bandwidth control, and disengagement control, where an endpoint is disassociated from a gatekeeper and its zone.
