B-21
Cisco SIP IP Phone Administrator Guide
Appendix B SIP Call Flows
Call Flow Scenarios for Successful Calls
Cisco SIP IP Phone-to-Cisco SIP IP Phone Call Transfer Without Consultation
Using Failover to Bye/Also
Figure B-6
illustrates a successful call between Cisco SIP IP phones in which two parties are in a call
and then one of the participants transfers the call to a third party without first contacting the third party.
This is called a blind or unattended 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 transfers the call to User C.
18.
NOTIFY—Cisco SIP IP phone A
to Cisco SIP IP phone B
Cisco SIP IP phone A sends a NOTIFY message to Cisco SIP IP phone B. The
NOTIFY message notifies Cisco SIP IP phone C of the REFER event.
19.
200 OK—Cisco SIP IP phone B
to Cisco SIP IP phone A
Cisco SIP IP phone B sends a SIP 200 OK response to Cisco SIP IP phone A. The
200 OK response notifies Cisco SIP IP phone A that the NOTIFY message was
received.
A two-way RTP channel is established between Cisco SIP IP phone A and Cisco SIP IP phone C.
Step
Action
Description
