Call To A Gateway Acting As An Emergency Proxy From A Cisco Sip Ip Phone - Cisco 7960G Administration Manual

Appendix B SIP Call Flows
Step Action
ACK—Cisco SIP IP phone to Gateway 1
13.
INVITE—Cisco SIP IP phone to Gateway 1
14.
200 OK—Gateway 1 to Cisco SIP IP phone
15.
ACK—Cisco SIP IP phone to Gateway 1
16.

Call to a Gateway Acting As an Emergency Proxy from a Cisco SIP IP Phone

Figure B-3
proxy.
Figure B-3
SIP IP Phone
OL-7890-01
illustrates a successful call from a Cisco SIP IP phone to a gateway acting as an emergency
Successful Call from Cisco SIP IP Phone to SIP Gateway (Emergency Proxy)
Proxy
User A
IP
1. INVITE (Matches dial template for emergency route)
4. 100 Trying
6. 180 Ringing
8. 200 OK
9. ACK
11. BYE
14. 200 OK
Cisco Unified IP Phone 7960G and 7940G Administration Guide for Release 8.0 (SIP)
Description
The phone sends a SIP ACK to Gateway 1. The ACK confirms that
the phone has received the 200 OK response. The call session is now
temporarily inactive. No RTP packets are being sent.
User B takes User A off hold. Phone B sends a SIP INVITE request
to Phone A with the same call ID as the previous INVITE and a new
SDP attribute parameter (sendrecv), which is used to reestablish the
call.
Gateway 1 sends a SIP 200 OK response to the phone. The response
notifies the phone that the INVITE was successfully processed.
The phone sends a SIP ACK to Gateway 1. The ACK confirms that
the phone has received the 200 OK response. The call session is now
active.
GW
2. Setup
3. Call Proceeding
5. Alerting
7. Connect
10. Connect ACK
2-way voice path
12. Disconnect
13. Release
15. Release Complete
Call Flow Scenarios for Successful Calls
User B
PBX
B-7