Yealink SIP-T2 Series Administrator's Manual page 505

Step
The following figure illustrates the scenario of an unsuccessful call caused by the called
user's no answering. In this scenario, the two end users are User A and User B. User A
and User B are located at Yealink SIP IP phones.
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
F1. INVITE B
F4. 180 Ringing
F5. CANCEL
F8. 200 OK
Action
received.
Proxy Server
Description
F2. INVITE B
F3. 180 Ringing
F6. CANCEL
F7. 200 OK
Appendix
User B
493