The International Telecommunications Union (ITU) T.120 standard is an umbrella standard that contains a suite of communications and application protocols. T.120-based programs let multiple users participate in conferencing sessions over different types of networks and connections. Depending on the T.120 application, programs can use T.120-compatible data-conferencing features such as file transfer, program sharing, and whiteboard conferencing to make connections and collaborate. Developers can create applications using only T.120 or combining T.120 and other ITU standards, such as the H.323 standard for video and audio conferencing.
The H.323 standard defines specifications for products that package audio and video information for transmission over a network. ITU based this standard on the Internet Engineering Task Force (IETF) Real Time Protocol (RTP) and Real Time Control Protocol (RTCP). H.323 also includes protocols for call signaling and audiovisual and data communications. Users can use products that support the H.323 standard to connect over a network or the Internet. More than 100 companies, including Microsoft, support the development of products that use both of these standards.