R2511-HP MSR Router Series Voice Configuration Guide(V5)

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• Zone administration and security control
• Call control signaling and call management
• Routing control and accounting
Figure 66 sh
ows a simple H.323 network. For all calls, a gatekeeper is the call service control and central
control unit in its administrative zone.
Gateway entities are usually deployed on routers. Configure the IP voice gateway function on the router
at CLI. They interact with the gatekeeper by sending H.225.0 RAS messages.
In the current implementation, the gatekeeper is usually deployed on SUN stations or servers while
gateways are deployed on routers. For the reliability’s sake, a backup gateway is configured. In the event
communication with a primary gatekeeper becomes abnormal (for example, timeout occurs) or the
primary gatekeeper becomes unavailable, gateways can turn to the backup gatekeeper for registration.
Figure 66 H.323 network
H.323 fundamentals
This section provides a brief description of how an H.323 network functions.
Gatekeeper discovery
When an endpoint wants to establish a call with another endpoint, it first looks for a gatekeeper with
which it can register for services. This process is called gatekeeper discovery. An RAS signaling message
exchange occurs between endpoints and the gatekeeper. The calling endpoint unicasts or broadcasts a
Gatekeeper_Request (GRQ) message. After receiving the request, the gatekeeper replies with a
Gatekeeper_Confirm (GCF) or Gatekeeper_Reject (GRJ) message.
Registration
When the calling endpoint receives a GCF message from the gatekeeper, it sends a Registration_Request
(RRQ) message, requesting to join the zone governed by the gatekeeper. The gatekeeper replies with a
Registration_Confirm (RCF) or Registration_Reject (RRJ) message to accept or reject the registration
request.
After registration, either the endpoint or the gatekeeper sends an Unregister_Request (URQ) message.
However, it is up to the gatekeeper to determine whether to cancel registration, while the endpoint can
only reply with an Unregister_Confirm (UCF) message to cancel registration.
Address translation
If the calling endpoint knows the alias, but not the call signaling address of the called endpoint, it sends
a Location_Request (LRQ) message to the gatekeeper.
IP network
Telephone Telephone Gateway Gateway
Gatekeeper