Appendix B SIP Call Flows
Call Flow Scenarios for Failed Calls
Cisco SIP IP
Figure B-18 illustrates an unsuccessful call in which User A initiates a call to User B but is prompted for authentication credentials by the proxy server. User A’s SIP IP phone then reinitiates the call with an SIP INVITE request that includes it’s authentication credentials.
Figure B-18 Cisco SIP IP Phone-to-Cisco SIP IP Phone—Authentication Error
SIP IP | Proxy |
| SIP IP | |
Server | IP Network | |||
Phone User A | Phone User B | |||
|
IP
IP
1.INVITE B
2.407 Authentication Error
3.ACK
4.Resend INVITE B
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