Yealink SIP-T19 E2 T4 Series, Administrator'S Manual

Page: 973 / 981

Appendix
951
Step Action Description
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. The 200 OK response
notifies User A that the connection has
been made.
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 ACK confirms that the proxy
server has received the 200 OK response.
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:
1.
User A calls User B.
2.
User B answers the call.
3.
User A places User B on hold.
4.
User A calls User C.
5.
User C answers the call.