Yealink T27P - Page 584

Administrator’s Guide for SIP-T2_Series_T4_Series IP Phones
570
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 Proxy Server User B
F1. INVITE B
F2. INVITE B
F3. 100 Trying
F9. ACK
F10. ACK
F5. 180 Ringing
2-way RTP channel established
F8. 200 OK
F7. 200 OK
F6. 180 Ringing
F4. 100 Trying
F11. BYE
F12. BYE
F13. 200 OK
F14. 200 OK
Step
Action
Description
F1
INVITE—User A to Proxy
Server
User A sends a SIP 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 initiator in the
From field.