Yealink SIP-T2 Series

Administrator’s Guide for SIP-T2 Series/T19(P) E2/T4 Series IP Phones
1018
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
Step
Action
Description
F1
INVITE—User A to Proxy Server
User A sends the 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.
 A unique numeric identifier is
assigned to the call and is inserted in
the Call-ID field.
 The transaction number within a
single call leg is identified in the CSeq
field.
 The media capability User A is ready
to receive is specified.