Yealink Yealink SIP-T42G, Administrator'S Manual

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Administrator’s Guide for SIP-T2 Series/T19(P) E2/T4 Series/CP860 IP Phones
854
Step Action Description
alerted.
F4
180 Ringing—Proxy Server to
User A
The proxy server forwards the 180
Ringing response to User A. User A
hears the ring-back tone indicating that
User B is being alerted.
F5
200 OK—User B to Proxy
Server
User B sends a SIP 200 OK response to
the proxy server. The 200 OK response
notifies User A that the connection has
been made.
F6
200 OK—Proxy Server to User
A
The proxy server forwards the 200 OK
message to User A. The 200 OK
response notifies User A that the
connection has been made.
F7 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.
F8 ACK—Proxy Server to User B
The proxy server sends the SIP ACK to
User B. The ACK confirms that the proxy
server has received the 200 OK
response. The call session is now active.
F9 REFER—User B to Proxy Server
User B sends a REFER message to the
proxy server. User B performs a blind
transfer of User A to User C.
F10
202 Accepted—Proxy Server
to User B
The proxy server sends a SIP 202 Accept
response to User B. The 202 Accepted
response notifies User B that the proxy
server has received the REFER
message.
F11
REFER—Proxy Server to User
A The proxy server forwards the REFER
message to User A.
F12
202 Accepted—User A to
Proxy Server
User A sends a SIP 202 Accept response
to the proxy server. The 202 Accepted
response indicates that User A accepts
the transfer.
F13 BYE—User B to Proxy Server
User B terminates the call session by
sending a SIP BYE request to the proxy
server. The BYE request indicates that