User Manual

Yealink Skype for Business HD IP Phones Administrator Guide
410
Step
Action
Description
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 User
B wants to release the call.
F14
BYE—Proxy Server to User A
The proxy server forwards the BYE request
to User A.
F15
200OK—User A to Proxy Server
User A sends a SIP 200 OK response to the
proxy server. The 200 OK response confirms
that User A has received the BYE request.
F16
200OK—Proxy Server to User B
The proxy server forwards the SIP 200 OK
response to User B.
F17
INVITE—User A to Proxy Server
User A sends a SIP INVITE request to the
proxy server. In the INVITE request, a
unique Call-ID is generated and the
Contact-URI field indicates that User A
requests the call.
F18
INVITE—Proxy Server to User C
The proxy server maps the SIP URI in the To
field to User C.
F19
180 Ringing—User C to Proxy
User C sends a SIP 180 Ringing response to
the proxy server. The 180 Ringing response