Appendix
449
Step
Action
Description
F1
INVITE—User A to Proxy
Server
User A sends an INVITE message to a
proxy server. The INVITE request is an
invitation to User B to participate in a
call session.
In the INVITE request:
The IP address of User B is inserted
in the Request-URI field.
User A is identified as the call
session initiator in the From field.
A unique numeric identifier is
assigned to the call and is inserted
in the Call-ID field.
The transaction number within a
single call leg is 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
The proxy server forwards the SIP
CANCEL request to notify User B that
Summary of Contents for Yealink SIP-T28P
Page 1: ......
Page 28: ...Administrator s Guide for SIP T2xP and SIP T19P IP Phones 12 ...
Page 76: ...Administrator s Guide for SIP T2xP and SIP T19P IP Phones 60 ...
Page 226: ...Administrator s Guide for SIP T2xP and SIP T19P IP Phones 210 ...
Page 238: ...Administrator s Guide for SIP T2xP and SIP T19P IP Phones 222 ...
Page 253: ...Configuring Security Features 237 ...
Page 265: ...Resource Files 249 ...
Page 279: ...Troubleshooting 263 ...