Yealink Yealink SIP-T46G, Administrator'S Manual

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Administrator’s Guide for SIP-T2_Series_T4_Series IP Phones
576
Step Action Description
identified in the CSeq
field.

The media capability User
A is ready to receive is
specified.

The port on which User B is
prepared to receive the
RTP data is specified.
F2
INVITE—Proxy Server to User
B
The proxy server maps the SIP URI in the
To field to User B. Proxy server forwards
the INVITE message to User B.
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.