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

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Administrator’s Guide for SIP-T2 Series/T19(P) E2/T4 Series/T5 Series IP Phones
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Step Action Description
User A that the INVITE is successfully
processed.
F12 200 OK—Proxy Server to User A
The proxy server forwards the 200 OK
response to User A. The 200 OK response
notifies User B is successfully placed on
hold.
F13 ACK—User A to Proxy Server
User A sends an ACK message to the proxy
server. The ACK confirms that User A has
received the 200 OK response. The call
session is now temporarily inactive. No RTP
packets are being sent.
F14 ACK—Proxy Server to User B
The proxy server sends the ACK message to
User B. The ACK confirms that the proxy
server has received the 200 OK response.
Successful Call Setup and Call Waiting
The following figure illustrates a successful call between Yealink SIP IP phones in which two
parties are in a call, one of the participants receives and answers an incoming call from a third
party. 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 C calls User B.