Yealink SIP-T2 Series, Administrator'S Manual

Page: 997 / 1009

Appendix
975
Step Action Description
Ringing response indicates that the user
is being alerted.
F12
180 Ringing—Proxy Server to
User A
The proxy server forwards the 180
Ringing response to User A. User A
hears the ring-back tone indicating that
User C is being alerted.
F13
200OK—User C to Proxy
Server
User C sends a SIP 200 OK response to
the proxy server. The 200 OK response
notifies User A that the connection has
been made.
F14
200OK—Proxy Server to User
A The proxy server forwards the SIP 200
OK response to User A.
F15 ACK— User A to Proxy Server
User A sends a SIP ACK to the proxy
server. The ACK confirms that User A
has received the 200 OK response. The
call session is now active.
F16 ACK—Proxy Server to User C
The proxy server sends the ACK
message to User C.
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.