Yealink SIP-T2XP

Appendix
205
Step
Action
Description
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
NOTIFY—User A to Proxy
Server
User A sends a SIP Notify message to
the proxy server. The Notify message
informs User B the state of User A.
F14
NOTIFY—Proxy Server to User
B
The proxy server forwards the Notify
message to User B.
F15
200 OK—User B to Proxy
Server
User B sends a SIP 200 OK response to
the proxy server. The 200 OK response
notifies the proxy server that User B has
received the Notify message.
F16
200 OK—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 User B has
received the Notify message.
F17
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