Cisco 7960G Administrator's Manual page 142

Call Flow Scenarios for Successful Calls
Figure B-17 Successful Call from a Cisco IP Phone to a Cisco IP Phone Using a SIP Emergency Proxy
SIP IP Phone
User A
Step Action
INVITE—Cisco SIP IP phone
1.
(A) to emergency proxy
100 Trying—Emergency proxy
2.
to Cisco SIP IP phone (A)
INVITE—Emergency proxy to
3.
Cisco SIP IP phone (B)
100 Trying—Cisco SIP IP phone
4.
(B) to emergency proxy
180 Ringing—Cisco SIP IP
5.
phone (B) to emergency proxy
6. 180 Ringing—Emergency proxy
to Cisco SIP IP phone (A)
200 OK—Cisco SIP IP phone
7.
(B) to emergency proxy
8. 200 OK—Emergency proxy to
Cisco SIP IP phone (A)
Cisco SIP IP Phone Administrator Guide, Release 6.x and 7.x
B-46
Primary Proxy
IP
1. INVITE (Matches dial template for emergency route)
2. 100 Trying
6. 180 Ringing
8. 200 OK
9. ACK
11. BYE
14. 200 OK
Description
The phone tries to connect to the emergency proxy by sending out the INVITE
message. The dial template for the emergency route is matched.
The emergency proxy sends a SIP 100 Trying response to A. The response
indicates that the INVITE request has been received.
The backup proxy tries to connect to B by sending out the INVITE message.
User B sends a SIP 100 Trying response to the emergency proxy. The response
indicates that the INVITE request has been received.
User B sends a SIP 180 Ringing response to the emergency proxy. The response
indicates that User B is being alerted.
The emergency proxy sends a SIP 180 Ringing response to User A. The response
indicates that the emergency proxy is being alerted.
User B sends a SIP 200 OK response to the emergency proxy. The response
notifies the emergency proxy that the connection has been made.
The emergency proxy sends a SIP 200 OK response to User A. The response
notifies User A that the connection has been made.
Emergency Proxy
2-way voice path
Appendix B SIP Call Flows
SIP IP Phone
User B
IP
3. INVITE
4. 100 Trying
5. 180 Ringing
7. 200 OK
10. ACK
12. BYE
13. 200 OK