This Recommendation specifies syntax and semantics of terminal information messages as well as procedures to use them for in-band negotiation at the start of or during communication. The messages cover receiving and transmitting capabilities as well as mode preference from the receiving end, logical channel signalling, and Control & Indication. Acknowledged signalling procedures are specified to ensure reliable audiovisual and data communication.

Products claiming compliance with Version 9 of H.245 shall comply with all of the mandatory requirements of this Recommendation. Version 9 products can be identified by H.245 TerminalCapabilitySet messages containing a protocolIdentifier value of {itu-t (0) recommendation (0) h (8) 245 version (0) 9}.

In view of the coming publication of version 10 of this Recommendation, version 9 is published showing only the differences relative to version 8.