Yealink Yealink SIP-T28P, Administrator'S Manual

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Administrator’s Guide for SIP-T2xP and SIP-T19P IP Phones
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The following figure illustrates successful call forwarding between Yealink SIP IP phones
in which User B has enabled no answer call forward. The incoming call is forwarded to
User C when User B does not answer the incoming call after a period of time. In this call
flow scenario, the end users are User A, User B, and User C. They are all using Yealink
SIP IP phones, which are connected via an IP network.
The call flow scenario is as follows:
1. User B enables no answer call forward, and the destination number is User C.
2. User A calls User B.
3. User B does not answer the incoming call.
4. User B forwards the incoming call to User C.
5. User C answers the call.
Call is established between User A and User C.
User A Proxy Server User B User C
F1. INVITE B
F2. INVITE B
F3. 180 Ringing
F8. ACK
F9. INVITE C
F10. INVITE C
F11. 180 Ringing
F12. 180 Ringing
F13. 200 OK
F14. 200 OK
F15. ACK
F16. ACK
F4. 180 Ringing
F5. 302 Move Temporarily
F6. ACK
F7. 302 Move Temporarily
2-way RTP channel established