Appendix
433
Step
Action
Description
F1
INVITE—User A to Proxy
Server
User A sends the 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. The proxy server
sends 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
302 Move Temporarily—User
B to Proxy Server
User B sends a SIP 302 Moved
Temporarily message to the proxy
server. The message indicates that User
B is not available at SIP phone B. User B
rewrites the contact-URI.
F6
ACK—Proxy Server to User B
The proxy server sends a SIP ACK to
User B, the ACK message notifies User B
that the proxy server has received the
Summary of Contents for SIP-T4X
Page 1: ...T 4 XI PP h o n e A d mi n i s t r a t o r G u i d e...
Page 2: ......
Page 15: ...Administrator s Guide for SIP T4X IP Phones xiv...
Page 23: ...Administrator s Guide for SIP T4X IP Phones 8...
Page 217: ...Administrator s Guide for SIP T4X IP Phones 202...
Page 233: ...Administrator s Guide for SIP T4X IP Phones 218...
Page 245: ...Administrator s Guide for SIP T4X IP Phones 230...
Page 257: ...Administrator s Guide for SIP T4X IP Phones 242...
