User Manual

Appendix
415
Step
Action
Description
F18
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 C is
being alerted.
F19
200OK—User C to Proxy Server
User C sends a SIP 200 OK response to the
proxy server. The 200 OK response notifies
User A that the connection has been made.
F20
200OK—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 the connection has
been made.
F21
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.
F22
ACK—Proxy Server to User C
The proxy server forwards the ACK message
to User C. The ACK confirms that the proxy
server has received the 200 OK response.
The call session is now active.
F23
REFER—User A to Proxy Server
User A sends a REFER message to the proxy
server. User A performs a transfer of User B
to User C.
F24
202 Accepted—Proxy Server to
User A
The proxy server sends a SIP 202 Accepted
response to User A. The 202 Accepted
response notifies User A that the proxy
server has received the REFER message.
F25
REFER—Proxy Server to User B
The proxy server forwards the REFER
message to User B.
F26
202 Accepted—User B to Proxy
Server
User B sends a SIP 202 Accept response to
the proxy server. The 202 Accepted
response indicates that User B accepts the
transfer.
F27
BYE—User A to Proxy Server
User A terminates the call session by
sending a SIP BYE request to the proxy
server. The BYE request indicates that User
A wants to release the call.
F28
BYE—Proxy Server to User B
The proxy server forwards the BYE request
to User B.