Call From A Cisco Sip Ip Phone To A Cisco Sip Ip Phone Using A Sip Emergency Proxy - Cisco 7960G Administration Manual

Appendix B SIP Call Flows
Step Action
INVITE—Cisco SIP IP phone
6.
(A) to primary proxy (sixth try)
INVITE—Cisco SIP IP phone
7.
(A) to primary proxy (seventh
try)
INVITE—Cisco SIP IP phone
8.
(A) to backup proxy
100 Trying—Backup proxy to
9.
Cisco SIP IP phone (A)
INVITE—Backup proxy to
10.
Cisco SIP IP phone (B)
100 Trying—Cisco SIP IP phone
11.
(B) to backup proxy
12. 180 Ringing—Cisco SIP IP
phone (B) to backup proxy
180 Ringing—Backup proxy to
13.
Cisco SIP IP phone (A)
200 OK—Cisco SIP IP phone
14.
(B) to backup proxy
200 OK—Backup proxy to
15.
Cisco SIP IP phone (A)
ACK—Cisco SIP IP phone (A)
16.
to backup proxy
ACK—Backup proxy to
17.
Cisco SIP IP phone (B)
BYE—Cisco SIP IP phone
18.
(A) to backup proxy
19. BYE—Backup proxy to
Cisco SIP IP phone (B)
200 OK—Cisco SIP IP phone
20.
(B) to backup proxy
200 OK—Backup proxy to
21.
Cisco SIP IP phone (A)

Call from a Cisco SIP IP Phone to a Cisco SIP IP Phone Using a SIP Emergency Proxy

Figure B-17
emergency proxy. B is the extension of the dial template with the "Route" attribute as "emergency" in
the dialplan.xml file.
OL-7890-01
Description
The phone retries a sixth time to connect to the primary proxy by sending out the
INVITE message.
The phone retries a seventh time to connect to the primary proxy. If the connection
is not successful after this trial, the "Network Delay, Trying Backup" message
displays on the Phone.
The phone tries to connect to the backup proxy by sending out the INVITE
message.
The backup proxy sends a SIP 100 Trying response to the phone. The response
indicates that the INVITE request has been received.
The backup proxy tries to connect to B by sending out the INVITE message.
Phone B sends a SIP 100 Trying response to the backup proxy. The response
indicates that the INVITE request has been received.
Phone B sends a SIP 180 Ringing response to the backup proxy. The response
indicates that B is being alerted.
The backup proxy sends a SIP 180 Ringing response to A. The response indicates
that the backup proxy is being alerted.
Phone B sends a SIP 200 OK response to the backup proxy. The response notifies
the backup proxy that the connection has been made.
The backup proxy sends a SIP 200 OK response to Phone A. The response notifies
Phone A that the connection has been made.
Phone A acknowledges the backup proxy Connect message.
The backup proxy acknowledges the Phone B Connect message.
A terminates the call session and sends a SIP BYE request to the backup proxy.
The request indicates that User A wants to release the call.
The backup proxy terminates the call session and sends a SIP BYE request to
User B. The request indicates that the backup proxy wants to release the call.
User B sends a SIP 200 OK response to the backup proxy. The response notifies
the backup proxy that B has received the BYE request.
The backup proxy sends a SIP 200 OK response to User A. The response notifies
User A that the backup proxy has received the BYE request.
illustrates a successful call from a Cisco SIP IP phone to a Cisco SIP IP phone via an
Cisco Unified IP Phone 7960G and 7940G Administration Guide for Release 8.0 (SIP)
Call Flow Scenarios for Successful Calls
B-45