Call Transfer With Consultation - Cisco 7960G Administrator's Manual

Appendix B SIP Call Flows
Step Action
13. INVITE—Phone A to Phone C
14. 100 Trying—Phone C to
Phone A
180 Ringing—Phone C to
15.
Phone A
200 OK—Phone C to Phone A
16.
ACK—Phone A to Phone C
17.
A two-way RTP channel is established between Phone A and Phone C.

Call Transfer with Consultation

Figure B-9
one of the participants contacts a third party, and then that participant transfers the call to the third party.
This is called an attended transfer. In this call flow scenario, the end users are User A, User B, and
User C. They are all using Cisco SIP IP phones, which are connected via an IP network.
The call flow scenario is as follows:
1.
2.
3.
4.
5.
6.
Description
Phone A sends a SIP INVITE request to Phone C. The request is an invitation to
User C to participate in a call session. The request contains the following
information:
Requested-By: B
•
The message indicates that the INVITE was requested by Phone B.
Phone C sends a SIP 100 Trying response to Phone A. The response indicates that
the INVITE request has been received.
Phone C sends a SIP 180 Ringing response to Phone A.
Phone C sends a SIP 200 OK response to Phone A. The response notifies Phone A
that the connection has been made.
Phone A sends a SIP ACK to Phone C. The ACK confirms that Phone A has
received the 200 OK response from Phone C.
illustrates a successful call between Cisco SIP IP phones in which two parties are in a call,
User A calls User B.
User B answers the call.
User B calls User C, and User C consents to take the call.
User B transfers the call to User C.
User B disconnects with User C.
User C and User A connect to each other.
Call Flow Scenarios for Successful Calls
Cisco SIP IP Phone Administrator Guide, Release 6.x and 7.x
B-23