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

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As shown in Figure 36, a SIP UA sends its registrar a REGISTER request at startup or in response to an
administrative registration operation, carrying all the information that must be recorded. Upon receipt of
the request, the registrar sends back a response notifying receipt of the request, and a 200 OK
(SUCCESS) message if the registration is accepted.
Figure 36 Message exchange for a UA to register with a Registrar
Call setup
SIP operates in the Client/Server mode and sets up calls through communication between UA and proxy
server.
Figure 37 Network diagram
In the above figure, Telephone A will call Telephone B, and Router A and Router B work as SIP endpoints
(UAs).
The following is the procedure for connecting a call from Telephone A to Telephone B:
1. Telephone A sends the number of Telephone B.
2. Upon receipt of the call, Router A sends a session request (INVITE) to the proxy server.
3. The proxy server consults its database for information corresponding to the number of Telephone
B. If such information is available, it forwards the request to Router B.
4. Router B, after receiving the request, responds to the proxy server and makes Telephone B ring if
Telephone B is available.
5. The proxy server forwards the response to Router A. The response discussed here includes two
provisional response messages (100 Trying and 180 Ringing) and one success response (200
OK).
Figure 38 i
llustrates the complete call setup procedure.