Yealink SIP-T4X Administrator's Manual page 428

Administrator's Guide for SIP-T4X IP Phones
The following figure illustrates the scenario of a successful call. 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 answers the call.
3. User B hangs up.
User A
412
Proxy Server
F1. INVITE B
F4. 100 Trying
F6. 180 Ringing
F8. 200 OK
F9. ACK
2-way RTP channel established
F12. BYE
F13. 200 OK
User B
F2. INVITE B
F3. 100 Trying
F5. 180 Ringing
F7. 200 OK
F10. ACK
F11. BYE
F14. 200 OK