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Cisco SIP IP Phone 7960 Administrator Guide
78-10497-02
Appendix B SIP Call Flows
Call Flow Scenarios for Successful Calls
Cisco SIP IP Phone-to-Cisco SIP IP Phone Call Transfer with
Consultation
Figure B-8 illustrates a successful call between Cisco SIP IP phones in which two
parties are in a call, 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.
User A calls User B.
2.
User B answers the call.
3.
User B calls User C and User C consents to take the call.
4.
User B transfers the call to User C.
7
INVITE—Cisco SIP IP phone A
to Cisco SIP IP phone C
(Requested by Cisco SIP IP
phone B)
At the request of Cisco SIP IP phone B, Cisco SIP IP
phone A sends a SIP INVITE request to Cisco SIP IP
phone C. The INVITE request is an invitation to User C to
participate in a call session.
8
180 Ringing—Cisco SIP IP
phone C to Cisco SIP IP phone A
Cisco SIP IP phone C sends a SIP 180 Ringing response to
Cisco SIP IP phone A.
9
200 OK—Cisco SIP IP phone C
to Cisco SIP IP phone A
Cisco SIP IP phone C sends a SIP 200 OK response to
Cisco SIP IP phone A. The 200 OK response notifies Cisco
SIP IP phone A that the connection has been made.
10
ACK—Cisco SIP IP phone A to
Cisco SIP IP phone C
Cisco SIP IP phone A sends a SIP ACK to 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.
A two-way RTP channel is established between Cisco SIP IP phone A and Cisco SIP IP phone C.
Step Action Description