Yealink T46G Administrator's Manual page 412

Yealink Skype for Business HD IP Phones Administrator Guide
Step
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
F12 200 OK—Proxy Server to User A
F13 ACK—User A to Proxy Server
F14 ACK—Proxy Server to User B
F15 INVITE—User A to Proxy Server
F16 INVITE—Proxy Server to User C
180 Ringing—User C to Proxy
F17
Server
398
Action
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 was 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.
User A sends a SIP INVITE request to the
proxy server. In the INVITE request, a
unique Call-ID is generated and the
Contact-URI field indicates that User A
requests the call.
The proxy server maps the SIP URI in the To
field to User C. The proxy server sends the
INVITE request to User C.
User C sends a SIP 180 Ringing response to
the proxy server. The 180 Ringing response
indicates that the user is being alerted.
Description