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Universal Network Terminal TAU-32M.IP 263
Algorithm description:
Connection establishment (via ITU-Q.931/H.225 protocol):
1.
Subscriber A gateway rings up Subscriber B (sends 'setup' message).
2.
Subscriber B gateway sends a message, stating the possibility of process continuation.
3.
Subscriber B gateway sends 'Alerting' notification message
.
Subscriber B is free. In this moment, 'ringing'
tone is sent to the Subscriber B phone, and 'ringback' tone to Subscriber A phone.
4.
Subscriber B gateway answers the call.
Logic channel establishment (via H.245 protocol):
1.
Subscriber A gateway informs Subscriber B gateway on its supported capabilities
(TerminalCapabilitySet).
2.
Subscriber B gateway confirms the request (TerminalCapabilitySetAck). The same procedure is repeated
in reverse direction from Subscriber B to Subscriber A.
3.
Operation mode is defined—which gateway will be the 'master', and which will be the 'slave'.
4.
Each gateway sends a message for a logic channel opening (OpenLogicalChannel). If gateways are ready
to receive the data, they send confirmation messages on logic channel opening
(OpenLogicalChannelAck). Call RTP sessions opens.
8.5
Algorithm of a Successful Call via H.323 Protocol with Gatekeeper
Gatekeeper performs address translation and manages H.323 terminals' access to network resources.
This section describes an example of a basic connection initiation scenario via H.323 protocol with a
gatekeeper.
Fig. 25—Gatekeeper call algorithm