Cisco Sip Ip Phone-To Cisco Sip Ip Phone Three-Way Calling - Cisco SIP IP Phone Administrator's Manual

Call Flow Scenarios for Successful Calls
Step Action
13. ACK—Cisco SIP IP phone A to
SIP proxy server
14. ACK—SIP proxy server to Cisco
SIP IP phone C

Cisco SIP IP Phone-to Cisco SIP IP Phone Three-Way Calling

Figure B-12
two RTP channels and therefore establishes a conference bridge between User A and User C. 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.
Cisco SIP IP Phone Administrator Guide
B-42
Description
Cisco SIP IP phone A sends a SIP ACK to the SIP proxy server. The ACK
confirms that Cisco SIP IP phone A has received the 200 OK response from
Cisco SIP IP phone C.
SIP proxy server forwards the SIP ACK to the Cisco SIP IP phone C. The ACK
confirms that Cisco SIP IP phone A has received the 200 OK response from
Cisco SIP IP phone C.
illustrates successful three-way calling between Cisco SIP IP phones in which User B mixes
User A calls User B.
User B answers the call.
User B puts User A on hold.
User B calls User C.
User C answers the call.
User B takes User A off hold.
Appendix B SIP Call Flows