Unsuccessful Call Setup-Called User Does Not Answer - Yealink CP969 Administrator's Manual

Step
100 Trying—Proxy Server to User
F4
A
486 Busy Here—User B to Proxy
F5
Server
486 Busy Here—Proxy Server to
F6
User A
F7 ACK—User A to Proxy Server
F8 ACK—Proxy Server to User B
Unsuccessful Call Setup—Called User Does Not Answer
The following figure illustrates the scenario of an unsuccessful call caused by the called user's no
answering. 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:
User A calls User B.
1.
User B does not answer the call.
2.
User A hangs up.
3.
Action
indicates that the INVITE request has been
received by User B.
The proxy server forwards the SIP 100
Trying to User A to indicate that the INVITE
request has already been received.
User B sends a SIP 486 Busy Here response
to the proxy server. The 486 Busy Here
response is a client error response
indicating that User B is successfully
connected but User B is busy on the IP
phone and unable or unwilling to take the
call.
The proxy server forwards the 486 Busy
Here response to notify User A that User B
is busy.
User A sends a SIP ACK to the proxy server.
The SIP ACK message indicates that User A
has received the 486 Busy Here message.
The proxy server forwards the SIP ACK to
User B to indicate that the 486 Busy Here
message has already been received.
Appendix
Description
811