D-16
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
6. Gateway Admission Request
(ARQ)—SCN/PSTN Gateway to H.323
gatekeeper
(Somewhat simultaneous, chronologically, to call setup and call
proceeding) Gateway contacts the common H.323 gatekeeper,
seeking authorization to complete the two-way H.323
network-to-CSN/PSTN Gateway call.
7. Gateway Admission Confirm (ACF) or
Admission Reject (ARJ)—H.323 gatekeeper to
CSN/PSTN Gateway
H.323 gatekeeper returns a ACF or ARJ message, indicating
whether or not the responding gatekeeper is going to al low the
Gateway access to the network.
8. Q.931 Alerting—Gateway endpoint to local
H.323 endpoint
Status message is sent to calling H.323 endpoint advising that the
called party has been notified (phone ringing).
9. Q.931 Connect—Gateway to local H.323
endpoint
Status message is sent to calling H.323 endpoint advising that the
called party has answered the call (phone off hook).
10. Open TCP Channel for H. 245 Dynamically assigned TCP port is opened on both the local H.323
endpoint and the Gateway, allowing for subsequent call setup
activities (transmission and reception capability exchange,
master-slave relationship determination, and so on).
11. H.245 Terminal Capabilities Various endpoint transmission and reception capabilities defining
operation of voice, video, and data are exchanged and
acknowledged to ensure consistent, reliable two-way
communication between the H.323 endpoint and the Gateway.
12. H.245 Terminal Capabilities
13. H.245 Terminal Capabilities
14. H.245 Terminal Capabilities
15. Exchange of Master-Slave Determination
Messages—Remote H.323 endpoint to local
H.323 endpoint
Determines master and slave assignments between the H.323
endpoint and the Gateway.
16. H.245 Open Audio Logical Channel—Local
H.323 endpoint to remote H.323 endpoint
Before actual transmission or reception of voice, video, or data,
notification that the primary logical channel for the local H.323
endpoint has been opened, ensuring clear two-way
communication.
17. H.245 Open Audio Logical Channel
Acknowledgement—Remote H.323 endpoint to
local H.323 endpoint
Gateway acknowledges readiness.
18. H.245 Open Audio Logical Channel—Remote
H.323 endpoint to local H.323 endpoint
Before actual transmission or reception of voice, video, or data,
notification that the primary logical channel for the Gateway has
been opened, ensuring clear two-way communication.
19. H.245 Open Audio Logical Channel
Acknowledgement—Local H.323 endpoint to
remote H.323 endpoint
Local H.323 endpoint acknowledges readiness.
20. Bi-Directional Audio with Transcoding Between
Endpoint and Gateway
Two-way communication ensues between the local H.323
endpoint and the CSN/PSTN Gateway.
TableD-5 Action Descriptions (continued)
Step Action Description