Cisco SIP IP Phone User Manual

B-61
Cisco SIP IP Phone Administrator Guide
Appendix B SIP Call Flows
Call Flow Scenarios for Failed Calls
Figure B-23 A Successful Call from a Cisco SIP IP Phone to a Cisco SIP IP Phone via Emergency Proxy
Step Action Description
1. INVITE—Cisco SIP IP phone
(User A) to emergency proxy
Cisco SIP IP phone tries to connect to the emergency proxy by sending out the
INVITE message. The dial template for the emergency route is matched.
2. 100 Trying—Emergency proxy
to Cisco SIP IP phone (User A)
Emergency proxy sends a SIP 100 Trying response to User A. The 100 Trying
response indicates that the INVITE request has been received by the emergency
proxy.
3. INVITE—Emergency proxy to
Cisco SIP IP phone (User B)
Backup proxy tries to connect to User B by sending out the INVITE message.
4. 100 Trying—Cisco SIP IP phone
(User B) to emergency proxy
User B sends a SIP 100 Trying response to the emergency proxy. The 100 Trying
response indicates that the INVITE request has been received by User B.
5. 180 Ringing—Cisco SIP IP
phone (User B) to emergency
proxy
User B sends a SIP 180 Ringing response to the emergency proxy. The
180 Ringing response indicates that User B is being alerted.
6. 180 Ringing—Emergency proxy
to Cisco SIP IP phone (User A)
The emergency proxy sends a SIP 180 Ringing response to User A. The
180 Ringing response indicates that the emergency proxy is being alerted.
7. 200 OK—Cisco SIP IP phone
(User B) to emergency proxy
User B sends a SIP 200 OK response to the emergency proxy. The 200 OK
response notifies the emergency proxy that the connection has been made.
IP IP
SIP IP Phone
User A
SIP IP Phone
User B
Primary Proxy
Emergency Proxy
2. 100 Trying
3. INVITE
4. 100 Trying
5. 180 Ringing
6. 180 Ringing
7. 200 OK
8. 200 OK
9. ACK
10. ACK
11. BYE
12. BYE
13. 200 OK
14. 200 OK
2-way voice path
62071
1. INVITE (Matches dial template for emergency route)

Cisco SIP IP Phone Specifications

General

Brand	Cisco
Model	SIP IP Phone
Category	IP Phone
Language	English