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Embedded Gatekeeper MultiVOIP User Guide
484
•Gatekeeper services
Built-in services such as call forward, zones and exit zone; and custom
services.
The Gatekeeper Protocols
H.323 is an umbrella standard that consists of many subordinate protocols.
Three protocols, Q.931, H.225, and H.245, are particularly relevant to
gatekeepers.
The Q.931 protocol pertains to the setup and teardown of call connections
between network endpoints.
The H.225 Call Signaling Protocol pertains to Registration, Admission, and
Status (RAS). (Note that RAS in H.323 has nothing to do with the Remote
Access Service that is used in ordinary TCP/IP networks.) H.323 RAS
messages are concerned with general participation on the network
(registration), specific involvement in particular calls between endpoints within
and perhaps outside of the network zone (admission), and the status of
endpoints (e.g., are they still “alive” or participating?).
H.245 is the conference control protocol. It pertains to negotiation between
endpoints to establish a compatible set of media capabilities.
Because many user-settable parameters of the MultiTech gatekeeper software
refer directly or indirectly to the H.225 protocol, we present a summary of
common H.225 messages below.