Call Transfer Without Consultation - Yealink SIP-T2 SERIES Administrator's Manual

Administrator's Guide for SIP-T2 Series/T19(P) E2/T4 Series/CP860 IP Phones
Step
F17 ACK—User A to Proxy Server
F18 ACK—Proxy Server to User B
F19 200 OK—User A to Proxy Server
F20 200 OK—Proxy Server User C
F21 ACK—User C to Proxy Server
F22 ACK—Proxy Server to User A

Call Transfer without Consultation

The following figure illustrates a successful call between Yealink SIP IP 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 SIP IP phones, which are connected via an IP
network.
1038
Action
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 200 OK response to the
proxy server. The 200 OK response notifies
that the connection has been made.
The proxy server forwards the 200 OK
message to User C.
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.
The proxy server forwards the SIP ACK to
User A to confirm that User C has received
the 200 OK response.
Description