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B-4
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
Call Setup and Hold
Figure B-2
illustrates a successful phone-call setup and call hold. In this scenario, the two end users are
User A and User B. User A is located at PBX A. PBX A is connected to Gateway 1 (SIP gateway) via a
T1/E1. User B is located at a Cisco SIP IP phone. Gateway 1 is connected to the Cisco SIP IP phone over
an IP network.
The call flow is as follows:
1.
User A calls User B.
2.
User B answers the call.
3.
User B puts User A on hold.
4.
User B takes User A off hold.
4.
100 Trying—Cisco SIP IP phone to
Gateway 1
The phone sends a SIP 100 Trying response to Gateway 1. The
response indicates that the INVITE request has been received.
5.
180 Ringing—Cisco SIP IP phone to
Gateway 1
The phone sends a SIP 180 Ringing response to Gateway 1. The
response indicates that the user is being alerted.
6.
Alerting—Gateway 1 to PBX A
Gateway 1 sends an Alert message to User A. The message indicates
that Gateway 1 has received a 180 Ringing response from the phone.
User A hears the ringback tone that indicates that User B is being
alerted.
7.
200 OK—Cisco SIP IP phone to Gateway 1
The phone sends a SIP 200 OK response to Gateway 1. The response
notifies Gateway 1 that the connection has been made.
8.
Connect—Gateway 1 to PBX A
Gateway 1 sends a Connect message to the PBX A. The message
notifies PBX A that the connection has been made.
9.
Connect ACK—PBX A to Gateway 1
PBX A acknowledges Gateway 1’s Connect message.
10.
ACK—Gateway 1 to Cisco SIP IP phone
Gateway 1 sends a SIP ACK to the phone. The ACK confirms that
Gateway 1 has received the 200 OK response. The call session is now
active.
11.
BYE—Cisco SIP IP phone to Gateway 1
User B terminates the call session. The phone sends a SIP BYE
request to Gateway 1. The request indicates that User B wants to
release the call.
12.
Disconnect—Gateway 1 to PBX A
Gateway 1 sends a Disconnect message to PBX A.
13.
Release—PBX A to Gateway 1
PBX A sends a Release message to Gateway 1.
14.
200 OK—Gateway 1 to Cisco SIP IP phone
Gateway 1 sends a SIP 200 OK response to the phone. The response
notifies the phone that Gateway 1 has received the BYE request.
15.
Release Complete—Gateway 1 to PBX A
Gateway 1 sends a Release Complete message to PBX A, and the call
session terminates.
Step
Action
Description