D-2
Cisco ATA 186 and Cisco ATA 188 Analog Telephone Adaptor Administrator’s Guide (H.323)
OL-4008-01
AppendixD H.323 Signaling
H.323 Signaling Scenarios
H.323 Signaling Scenarios
This section describes call flows for the following scenarios:
•H.323 Endpoint-to-Gatekeeper Registration, page D-2
•H.323 Endpoint-to-Endpoint Call Setup with a Common Gatekeeper, page D-5
•H.323 Call Setup from H.323 Network to Circuit Switched Network, page D-14
Each of the call flows includes a call diagram, action descriptions table, and a sample log file.

H.323 Endpoint-to-Gatekeeper Registration

Figure D-1 illustrates the Cisco ATA registering with an H.323 gatekeeper. This scenario features
registration with no authentication.
Figure D-1 Cisco ATA-to-H.323 Gatekeeper Registration
TableD-1 Action Descriptions
Step Action Description
1. Gatekeeper Request (GRQ)—Cisco ATA to
H.323 gatekeeper
Cisco ATA sends a GRQ message to the H.323 gatekeeper to see if
any gatekeepers are available for registration.
2. Gatekeeper Confirmation (GCF) or
gatekeeper Rejection (GRJ)—H.323
gatekeeper to Cisco ATA
H.323 gatekeeper returns a GCF or GRJ message, indic ating whether
or not the responding gatekeeper is able to register new Cisco ATA
devices.
3. Registration Request (RRQ)—Cisco ATA to
H.323 gatekeeper
Cisco ATA sends a RRQ message to the H.323 gatekeeper in an
attempt to register as part of that gatekeeper’s zone.
4. Registration Confirmation (RCF) or
Registration Rejection (RRJ)—H.323
gatekeeper to Cisco ATA
H.323 gatekeeper returns a RCF or RRJ message, indicating whether
or not the gatekeeper will add the CiscoATA to its zone.
GRQ
GCF/GRJ
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RRQ
RCF/RRJ
Endpoint Gatekeeper