Appendix B SIP Call Flows
Call Flow Scenarios for Failed Calls
Call Flow Scenarios for Failed Calls
This section describes call flows for the following scenarios, which illustrate unsuccessful calls:
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•
•
•Cisco SIP IP
•Cisco SIP IP
•Cisco SIP IP
Gateway-to-Cisco SIP IP Phone—Called User is Busy
Figure B-13 illustrates an unsuccessful call in which User A initiates a call to User B but User B is on the phone and is unable or unwilling to take another call.
Figure B-13 Gateway-to-Cisco SIP IP Phone—Called User is Busy
User A PBX A | GW1 |
| IP Network | |
|
|
|
|
|
SIP IP Phone
User B
IP
1. Setup
3. Call Proceeding
6.Disconnect (Busy)
7.Release
9. Release Complete
2.INVITE
4.100 Trying
5.486 Busy Here
8. ACK
41725
