D-1
Cisco ATA 186 and Cisco ATA 188 Analog Telephone Adaptor Administrator’s Guide (H.323)
OL-4008-01
APPENDIX
D

H.323 Signaling

This section describes some basic call flows for the Cisco ATA:
•Supported H.323 Messages, page D-1
•H.323 Signaling Scenarios, page D-2
Note The term Cisco ATA is used throughout this manual to refer to both the Cisco ATA 186 and the
Cisco ATA188, unless differences between the Cisc o ATA 186 and Cisco ATA 188 are explicitly stated.

Supported H.323 Messages

The Cisco ATA supports the following H.323 request methods:
•Request—When registering with an H.323 gatekeeper or Gateway, an individual H.323 endpoint
must begin the process by sending a request message.
•Confirm—H.323 gatekeepers and Gateways authorize individual H.323 endpoints to access and
send data over the H.323 network with explicit confirmation messages.
•Reject—In the event that an H.323 gatekeeper or Gateway in unable to grant access permission to
an H.323 endpoint, a rejection message is sent and call setup is halted.
•Setup—Once access to the H.323 network has been granted, H.323 components contact remote
H.323 components via setup messages, initiating two-way voice, video, or data communication.
•Proceeding—When a remote H.323 component acknowledges receipt of ca ll initiation information
and agrees to perform necessary subsequent setup for two-way voice, video, or data communic ation,
it responds with a proceeding message.
•Alerting—When a remote H.323 endpoint has begun to notify th e called party of an incoming call
(the phone begins to ring at the far end), an alerting message is sent back to the calling party.
•Connect—When the called party answers the call (the phone goes off hook), the remote H.323
endpoint transmits a connecting message notifying the calling party that two-way communication is
ready to commence.