Call Conference - Yealink SIP-T54S Administrator's Manual

Administrator's Guide for SIP-T2 Series/T19(P) E2/T4 Series/T5 Series/CP860/CP920 IP Phones
Step
180 Ringing—Proxy Server to
F12
User A
F13 200OK—User C to Proxy Server
F14 200OK—Proxy Server to User A
F15 ACK— User A to Proxy Server
F16 ACK—Proxy Server to User C

Call Conference

The following figure illustrates successful three-way calling between Yealink IP phones in which
User A mixes two RTP channels and therefore establishes a conference between User B and
User C. 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:
User A calls User B.
1.
User B answers the call.
2.
User A places User B on hold.
3.
User A calls User C.
4.
User C answers the call.
5.
1092
Action
alerted.
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.
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 sends the ACK message
to User C. The ACK confirms that the
proxy server has received the 200 OK
response.
Description