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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 Network Call Forwarding (No
Answer)
Figure B-12
illustrates successful call forwarding between Cisco SIP IP phones in which User B has
requested call forwarding from the network in the event that there is no answer. When User A calls
User B, the proxy server tries to place the call to Cisco SIP IP phone B and, if there is no answer, the
call is transferred to Cisco SIP IP phone 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.
User B requests that if the phone (Cisco SIP IP phone B) is not answered within a set amount of
time, the network should forward incoming calls to Cisco SIP IP phone C.
2.
User A calls User B.
3.
User B’s phone is not answered.
4.
The network transfers the call to Cisco SIP IP phone C.
11.
ACK—Cisco SIP IP phone A to
SIP proxy server
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.
12.
ACK—SIP proxy server to
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.
Step
Action
Description
