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Spirent KB Article
Doc ID: FAQ12499
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Abacus: When testing H.323 we are only seeing H.225 call control signaling, does Abacus support H.245 multimedia control signaling?
Yes. Abacus supports H.245 Multimedia Control Signaling.
By default, H.323 won’t use H.245, but you can change that in "Dial Settings" in the SUT Configuration window.
SUT Settings can be accessed from the CONFIGURE menu (
) or from the SUT settings button on the Navigation Bar (
By default, Abacus is configured for Faststart signaling with No H.245 (
); it Q.931 signaling.
With Faststart Signaling selected, it is possible to change H.245 Mode to:
Tunneled: All H.245 messages will be "tunneled" through the H.225 - Q.931 messages
Parallel: SETUP message will contain the H.245 "TerminalCapabilitySet" and MasterSlaveDetermination" messages along with the proposed "OpenLogicalChannel" messages in the "fastStart" element. The H.245 capability negotiation and master-slave determination are done in "parallel" with the faststart procedure.
Separate: H.245 addresses are exchanged within the H.225 - Q.931 messages, and then a separate H.245 TCP channel is opened through which all messages will then be exchanged.
Note: The available H.225 - Q.931 messages for embedding the H.245 address are CONNECT, ALERTING, and SETUP, selected from the Address Stage pull-down menu.
Note: With Faststart signaling selected, you may configure the media to be streamed after receipt of the CONNECT message by checking the "Media Wait for CONNECT" checkbox.
You may also select H.245 Mode “Tunneled” (
) which will ensure that an H.245 TCP connection is not opened. The various H.245 messages are "tunneled" through the H.225-Q.931 messages. Use of network resources is minimized using Tunneled Mode.
It is also possible to select H.245 Mode Separate (
) in which This is the only active button when Basic is selected under Call Modes. In this scenario, the H.245 addresses are exchanged within the H.225 - Q.931 messages, as described above (
If you would like the option to automatically detect tunneled/fast start modes, you can change the default H.323 protocol settings in Protocol Development:
To open the H.323 Protocol Development window, choose PROTOCOL DEVELOPMENT from the CONFIGURE menu (
) and scroll to the H.323 tab on the bottom of the window (
Default protocols used by Abacus are read-only, so you must create a new protocol.
To create a new H.323 Protocol, click NEW (
) and give your new protocol a unique name (
When your new H.323 protocol is created, Select “Use H.225/H.245 Mode in Incoming Call” (
). When this checkbox is selected, the signaling mode will switch automatically between Faststart and Tunneled. When this checkbox is not selected, the signaling mode will be determined by the setting in the H.323 SUT Dial Settings window (configured above).
If you have questions about any of the fields or functionality in the Abacus GUI, highlight the field you’re working with (by left mouse clicking in it) and press the F1 key to open context sensitive help.
Product : Abacus,Voice,6.20,6.11 and below,H323