Cisco SIP IP Phone User Manual

B-48
Cisco SIP IP Phone Administrator Guide
AppendixB SIP Call Flows
Call Flow Scenarios for Failed Calls
Gateway-to-Cisco SIP IP Phone—Called User Does Not Answer
Figure B-15 illustrates the call flow in which User A initiates a call to User B but User B does not answer.
Figure B-15 Gateway-to-Cisco SIP IP Phone—Called User Does Not Answer
6.
Disconnect (Busy)—Gateway 1
to PBX A
Gateway 1 sends a Disconnect message to PBX A.
7. Release—PBX A to Gateway 1 PBX A sends a Release message to Gateway 1.
8. ACK—Gateway 1 to Cisco SIP
IP phone
Gateway 1 sends a SIP ACK to the Cisco SIP IP phone. The ACK confirms that
User A has received the 486 Busy Here response. The call session attempt is now
being terminated.
9. Release Complete—Gateway 1
to PBX A
Gateway 1 sends a Release Complete message to PBX A and the call session
attempt is terminated.
Step Action Description
IP
SIP IP Phone
User B
3. Call Proceeding
11. Release Complete
8. Disconnect
6. Alerting
1. Setup
PBX A
User A
GW1 IP Network
4. 100 Trying
10. 200 OK
5. 180 Ringing
7. CANCEL
2. INVITE
9. Release
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Cisco SIP IP Phone Specifications

General

Brand	Cisco
Model	SIP IP Phone
Category	IP Phone
Language	English