Yealink SIP-T48G

Administrator’s Guide for SIP-T2 Series/T19(P) E2/T4 Series/CP860 IP Phones
852
Step
Action
Description
F13
INVITE—User A to Proxy
Server
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.
F14
INVITE—Proxy Server to User
B
The proxy server forwards the mid-call
INVITE message to User B.
F15
200 OK—User B to Proxy
Server
User B sends a 200 OK to the proxy
server. The 200 OK response indicates
that the INVITE was successfully
processed.
F16
200 OK—Proxy Server to User
A
The proxy server forwards the 200 OK
response to User A. The 200 OK
response notifies User B is successfully
placed on hold.
F17
ACK—User A to Proxy Server
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.
F18
ACK—Proxy Server to User B
The proxy server sends the ACK
message to User B. The ACK confirms
that the proxy server has received the
200 OK response.
F19
200 OK—User A to Proxy
Server
User A sends a 200 OK response to the
proxy server. The 200 OK response
notifies that the connection has been
made.
F20
200 OK—Proxy Server User C
The proxy server forwards the 200 OK
message to User C.
F21
ACK—User C to Proxy Server
User C sends a SIP ACK to the proxy
server. The ACK confirms that User C
has received the 200 OK response. The
call session is now active.
F22
ACK—Proxy Server to User A
The proxy server forwards the SIP ACK
to User A to confirm that User C has
received the 200 OK response.