Successful Call Setup And Call Waiting - Yealink SIP-T2XP Administrator's Manual

Administrator's Guide for SIP-T2xP IP Phones
Step
F7 ACK—User A to Proxy Server
F8 ACK—Proxy Server to User B
F9 INVITE—User A to Proxy Server
F10 INVITE—Proxy Server to User B
F11 200 OK—User B to Proxy Server
200 OK—Proxy Server to User
F12
A
F13 ACK—User A to Proxy Server
F14 ACK—Proxy Server to User B

Successful Call Setup and Call Waiting

The following figure illustrates a successful call between Yealink SIP IP phones in which
parties are in a call, one of the participants receives a call from a third party, then
answers the incoming call. In this call flow scenario, the end users are User A, User B, and
412
Action
User A sends a SIP ACK to the proxy
server. The ACK confirms that User A has
received the 200 OK response. The call
session is now active.
The proxy server sends the SIP ACK to
User B. The ACK confirms that the proxy
server has received the 200 OK
response. The call session is now active.
User A sends a mid-call INVITE request to
the proxy server with new SDP session
parameters, which are used to place
the call on hold.
The proxy server forwards the mid-call
INVITE message to User B.
User B sends a SIP 200 OK response to
the proxy server. The 200 OK response
notifies User A that the INVITE is
successfully processed.
The proxy server forwards the 200 OK
response to User A. The 200 OK response
notifies User B is successfully placed on
hold.
User A sends an ACK message to the
proxy server. The ACK confirms that User
A has received the 200 OK response.
The call session is now temporarily
inactive. No RTP packets are being
sent.
The proxy server sends the ACK
message to User B. The ACK confirms
that the proxy server has received the
200 OK response.
Description