Yealink SIP-T2 Series

Appendix
1011
Call is established between User B and User C.
User A Proxy Server User B
F1. INVITE B
F4. 180 Ringing
F6. 200 OK
F7. ACK
2-way RTP channel established
F9. INVITE B （sendonly）
F12. 200 OK
F13. ACK
F15. INVITE C
F17. 180 Ringing
F19. 200 OK
F21. ACK
F23. REFER
F24. 202 Accepted
User C
F2. INVITE B
F3. 180 Ringing
F5. 200 OK
F8. ACK
F10. INVITE B （sendonly）
F11. 200 OK
F14. ACK
F16. INVITE C
F18. 180 Ringing
F20. 200 OK
F22. ACK
2-way RTP channel established
F25. REFER
F26. 202 Accepted
F31. BYE
F32. BYE
F33. 200 OK
F34. 200 OK
2-way RTP channel established
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