H3C XE 200 IP, Operation Manual

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Operation Manual – Process Server Configuration
H3C XE 200/2000 IP PBX
Chapter 2 H.323 Overview
2-6
2.1.3 H.323 Operating Fundamentals
I. Gatekeeper discovery
Gatekeeper discovery refers to the process that an endpoint looks for a gateway ready
to serve and control it. RAS signaling is used between endpoints and gatekeepers. The
endpoint unicasts or multicasts a Gatekeeper Request (GRQ) message and the
gatekeeper or gatekeepers respond with a Gatekeeper Confirm (GCF) or Gatekeeper
Reject (GRJ).
II. Registration
If an endpoint sends a registration request (RRQ) message to a discovered or static
gatekeeper for joining the zone the gatekeeper governs, it may receive a registration
confirm (RCF) or registration reject (RRJ) message to accept or reject the registration
request.
After registration, either side can ask for canceling registration by sending an
Unregistration Request (URQ) message. However, whether to cancel registration is up
to the gatekeeper: the endpoint can only respond with an Unregistration Confirm (UCF)
message to cancel registration.
III. Address translation
If the calling endpoint knows the alias of the called endpoint but not the call signaling
address, it sends a Location Request (LRQ) message to the gatekeeper.
IV. Access control
If the address of the called endpoint is available, the calling endpoint sends an
Admissions Request (ARQ) message, based on which the gatekeeper decides
whether to allow this endpoint to join a call process. This is how the gatekeeper controls
admission. In the ARQ message sent to the gatekeeper, the calling endpoint may ask
for direct call signaling (see Figure 2-4 ) or gatekeeper-routed call signaling (see Figure
2-5 ). Which method is used however, is decided by the gatekeeper in the Admissions
Confirm (ACF) message.