Yealink SIP-T2XP Administrator's Manual page 576

Administrator's Guide for SIP-T2xP IP Phones
Step
200OK—User C to Proxy
F11
Server
200OK—Proxy Server to User
F12
A
F13 ACK—User A to Proxy Server
F14 ACK—Proxy Server to User C
The following figure illustrates successful call forwarding between Yealink SIP IP phones
in which User B has enabled busy call forward. The incoming call is forwarded to User C
when User B is busy. 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 busy call forward, and the destination number is User C.
2. User A calls User B.
3. User B is busy.
4. User B forwards the incoming call to User C.
5. User C answers the call.
558
Action
User C is being alerted.
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.
The proxy server forwards the SIP 200
OK response to User A. The 200 OK
response notifies User A that the
connection has been made.
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.
The proxy server forwards the ACK
message to User C. The ACK confirms
that the proxy server has received the
200 OK response. The call session is
now active.
Description