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148 TAU-72.IP/TAU-36.IP Universal Network Terminal
8.2
Call Algorithm Involving SIP Proxy Server
This section describes a connection initiation scenario between two gateways involving SIP proxy server.
In this case, caller gateway (Subscriber A) should know subscriber's permanent address and proxy server IP
address. SIP proxy server processes messages received from Subscriber A, discovers Subscriber B, prompts the
communication session and performs router functions for two gateways.
Fig. 13—Call algorithm involving SIP proxy server
Algorithm description:
1
Subscriber A and Subscriber B register at SIP server.
2
SIP server prompts for authorization.
3
Subscriber A and Subscriber B register at SIP server with authorization.
4
SIP server responses on successful registration.
5
Subscriber A rings up Subscriber B.
6
SIP server requests authentication.
7
Subscriber A gateway confirms received authorization request command.
8
Subscriber A rings up Subscriber B.
9
SIP server receives the command for processing.
10
SIP server translates Subscriber A call request directed at Subscriber B.
11
Subscriber B gateway receives the command for processing.
12
Subscriber B is free. In this moment, 'ringing' tone is sent to the Subscriber B phone, and
'ringback' tone to Subscriber A phone.
