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
F21 200OK—User C to Proxy Server
User C sends a SIP 200 OK response to the
proxy server. The 200 OK response notifies
the proxy server that the connection has
been made.
F22 200OK—Proxy Server to User A
The proxy server forwards the SIP 200 OK
response to User A.
F23 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.
F24 ACK—Proxy Server to User C
The proxy server forwards the ACK message
to User C. The ACK confirms that User A has
received the 200 OK response. The call
session is now active.
Call Transfer with Consultation
The following figure illustrates a successful call between Yealink SIP IP phones in which two
parties are in a call and then one of the parties transfers the call to the third party with
consultation. This is called attended transfer. 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 calls User C.
4.
User C answers the call.
5.
User A transfers the call to User C.