Yealink SIP-T2XP

Appendix
203
User A Proxy Server User B
F1. INVITE B
F4. 180 Ringing
F6. 200 OK
F7. ACK
2-way RTP channel established
F23. 180 Ringing
F11. REFER
F12. 202 Accepted
F14. NOTIFY
F26. 200 OK
F2. INVITE B
F3. 180 Ringing
F5. 200 OK
F8. ACK
F22. INVITE C
F19. 200 OK
F27. ACK
F18. BYE
2-way RTP channel established
F9. REFER
F10. 202 Accepted
F13. NOTIFY
F15. 200 OK
F17. BYE
F20. 200 OK
F21. INVITE C
F24. 180 Ringing
F25. 200 OK
F28. ACK
F16. 200 OK
User C