User Manual

Yealink Skype for Business HD IP Phones Administrator Guide
408
Step
Action
Description
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.
Call Transfer without Consultation
The following figure illustrates a successful call between Yealink Skype for Business phones in
which two parties are in a call and then one of the parties transfers the call to a third party
without consultation. This is called a blind transfer. In this call flow scenario, the end users are
User A, User B, and User C. They are all using Yealink Skype for Business phones, which are
connected via an IP network.
The call flow scenario is as follows:
1. User A calls User B.
2. User B answers the call.
3. User B transfers the call to User C.
4. User C answers the call.