B-13
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 Waiting
Figure B-5
illustrates a successful call between Cisco SIP IP phones in which two parties are in a call,
one of the participants receives a call from a third party, and then returns to the original call. 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 C calls User B.
4.
User B accepts the call from User C.
5.
User B switches back to User A.
6.
User B hangs up, ending the call with User A.
7.
User B is notified of the remaining call with User C.
8.
User B answers the notification and continues the call with User C.
16.
ACK—Cisco SIP IP phone B to
Cisco SIP IP phone A
Cisco SIP IP phone B sends a SIP ACK to Cisco SIP IP phone A. The ACK
confirms that Cisco SIP IP phone B has received the 200 OK response from
Cisco SIP IP phone A.
A two-way RTP channel is reestablished between Cisco SIP IP phone A and Cisco SIP IP phone B.
Step
Action
Description
