Appendix B SIP Call Flows
Call Flow Scenarios for Failed Calls
Step | Action | Description |
|
|
|
7 | CANCEL (Ring | Because Gateway 1 did not return an appropriate response |
| within the time allocated in the INVITE request, Gateway | |
| SIP IP phone | 1 sends a SIP CANCEL request to Gateway 2. A CANCEL |
|
| request cancels a pending request with the same |
|
| To, From, and CSeq header field values. |
|
|
|
8 | Gateway 1 sends a Disconnect message to PBX A. | |
| A |
|
|
|
|
9 | Release | Gateway 1 sends a Release Complete message to PBX A |
| to PBX A | and the call session attempt is terminated. |
|
|
|
10 | 200 | The Cisco SIP IP phone sends a SIP 200 OK response to |
| Gateway 1 | Gateway 1. The 200 OK response confirms that User A has |
|
| received the 486 Busy Here response. The call session |
|
| attempt is now being terminated. |
|
|
|
11 | Release | Gateway 1 sends a Release Complete message to PBX A |
| to PBX A | and the call session is terminated. |
|
|
|
| Cisco SIP IP Phone 7960 Administrator Guide |
|
