Yealink Yealink SIP-T46G, Administrator'S Manual

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Appendix
575
The call flow scenario is as follows:
1. User A calls User B.
2. User B does not answer the call.
3. User A hangs up.
The call cannot be set up successfully.
User A Proxy Server User B
F1. INVITE B
F2. INVITE B
F3. 180 Ringing
F4. 180 Ringing
F8. 200 OK
F7. 200 OK
F5. CANCEL
F6. CANCEL
Step Action Description
F1
INVITE—User A to Proxy
Server
User A sends an INVITE message to a
proxy server. The INVITE request is an
invitation to User B to participate in a
call session.
In the INVITE request:

The IP address of User B is
inserted in the Request-URI
field.

User A is identified as the
call session initiator in the
From field.

A unique numeric identifier
is assigned to the call and
is inserted in the Call-ID
field.

The transaction number
within a single call leg is