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Call Flow Scenarios for Failed Calls
Step
Action
6.
180 Ringing—Gateway to
Cisco SIP IP phone (User A)
7.
Connect—PBX to gateway
8.
200 OK—Gateway to Cisco SIP
IP phone (User A)
ACK—Cisco SIP IP phone
9.
(User A) to gateway
Connect ACK—Gateway to
10.
PBX
BYE—Cisco SIP IP phone
11.
(User A) to gateway
Disconnect—Gateway to PBX
12.
13.
Release—PBX to gateway
14.
200 OK—Gateway to Cisco SIP
IP phone (User A)
15.
Release Complete—Gateway to
PBX
Call from a Cisco SIP IP Phone to a Cisco SIP IP Phone via Emergency Proxy
Figure B-23
proxy. User B is the extension of the dial template with the "Route" attribute as "emergency" in the
dialplan.xml file.
Cisco SIP IP Phone Administrator Guide
B-60
Description
The gateway sends a SIP 180 Ringing response to User A. The 180 Ringing
response indicates that the gateway is being alerted.
PBX sends a Connect message to gateway. The Connect message notifies the
gateway that the connection has been made.
Gateway sends a SIP 200 OK response to the User A. The 200 OK response
notifies User A that the connection has been made.
User A sends a SIP ACK to the gateway. The ACK confirms that User A has
received the 200 OK response. The call session is now active.
Gateway acknowledges PBX's Connect message.
User A terminates the call session and sends a SIP BYE request to gateway. The
BYE request indicates that User A wants to release the call.
Gateway sends a Disconnect message to PBX.
PBX sends a Release message to the gateway.
Gateway sends a SIP 200 OK response to User A. The 200 OK response notifies
User A that the gateway has received the BYE request.
Gateway sends a Release Complete message to the PBX and the call session is
terminated.
illustrates a successful call from a Cisco SIP IP phone to a Cisco SIP IP phone via emergency
Appendix B
SIP Call Flows
- Quick Links:
- Using the Command-Line Interface
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