Yealink SIP-T2 Series, Administrator'S Manual

Page: 975 / 1009

Appendix
953
Step Action Description
F3
180 Ringing—User B to Proxy
Server
User B sends a SIP 180 Ringing response
to the proxy server. The 180 Ringing
response indicates that the user is being
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
CANCEL—User A to Proxy
Server
User A sends a SIP CANCEL request to
the proxy server after not receiving an
appropriate response within the time
allocated in the INVITE request. The SIP
CANCEL request indicates that User A
wants to disconnect the call.
F6
CANCEL—Proxy Server to
User B
The proxy server forwards the SIP
CANCEL request to notify User B that
User A wants to disconnect the call.
F7
200 OK—User B to Proxy
Server
User B sends a SIP 200 OK response to
the proxy server. The SIP 200 OK
response indicates that User B has
received the CANCEL request.
F8
200 OK—Proxy Server to User
A
The proxy server forwards the SIP 200
OK response to notify User A that the
CANCEL request has been processed
successfully.
The following figure illustrates a successful call setup and call hold. In this scenario, the
two end users are User A and User B. User A and User B are located at Yealink SIP IP
phones.
The call flow scenario is as follows:
1. User A calls User B.
2. User B answers the call.