B-42
Cisco Unified IP Phone 7960G and 7940G Administration Guide for Release 8.0 (SIP)
OL-7890-01
Appendix B SIP Call Flows
Call Flow Scenarios for Successful Calls
Figure B-15 Call from a Cisco SIP IP Phone to a Gateway Acting As a Backup Proxy
Step
Action
Description
1.
INVITE—Cisco SIP IP phone to
primary proxy
The phone tries to connect to the proxy by sending out the INVITE message.
2.
INVITE—Cisco SIP IP phone to
primary proxy (second try)
The phone retries a second time to connect to the proxy by sending out the
INVITE message.
3.
INVITE—Cisco SIP IP phone to
primary proxy (third try)
The phone retries a third time to connect to the proxy by sending out the
INVITE message.
4.
INVITE—Cisco SIP IP phone to
primary proxy (fourth try)
The phone retries a fourth time to connect to the proxy by sending out the
INVITE message.
IP
SIP IP Phone
User A
Primary
1. INVITE
2. INVITE (retry)
3. INVITE (retry)
4. INVITE (retry)
5. INVITE (retry)
6. INVITE (retry)
7. INVITE (retry)
8. INVITE (retry)
9. Setup
10. Call Proceeding
11. 100 Trying
12. Alerting
13. 180 Ringing
14. Connect
15. 200 OK
16. ACK
17. Connect ACK
18. BYE
2-way voice path
19. Disconnect
20. Release
22. Release Complete
21. 200 OK
GW
PBX
User B
62069