The T.120 Standard
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The T.120 Standard

The ITU T.120 standard is composed of a suite of communication and application layer protocols developed and approved by the international computer and telecommunications industries. These protocols enable developers to create compatible products and services for real-time, multipoint data connections and conferencing. T.120-based applications let many users participate in conferencing sessions over different types of networks and connections. Depending on the type of T.120 product, users can:

  • Make connections.
  • Transmit and receive data.
  • Collaborate using compatible data conferencing features, such as application sharing, conferencing white board, and file transfer.

T.120 Components

T.120 is an umbrella standard that encompasses a series of communication and application standards. The following standards and components make up the T.120 infrastructure.

T.120Data protocols for multimedia conferencing which provide an overview of the T.120 series.
T.121This standard provides a generic application template (GAT), which specifies a common set of guidelines for building application protocols. To ensure application consistency, T.121 is a required standard for products developed under T.120.
T.122The T.122 standard defines the multipoint services that enable one or more participants to send data as part of a conference. These multipoint services are implemented by T.125, which provides the mechanism for transporting the data. Together, the T.122 and T.125 standards make up the T.120 Multipoint Communication Services (MCS).
T.123The T.123 standard is responsible for transporting and sequencing data, and for controlling the flow of data across networks, including connect, disconnect, send, and receive functions. For data transport, T.123 defines a series of network interface profiles. T.123 also provides an error-correcting mechanism that ensures accurate and reliable data delivery.
T.123 Annex B also defines the protocol for secure data conferencing.
T.124Generic Conference Control (GCC): The definition of the application protocol supporting reservations and basic conference control services for multipoint teleconferences.
T.125This standard specifies how data is transmitted within a conference. T.125 defines the private and broadcast channels that transport the data and ensures accurate and efficient communication among multiple users. T.125 implements the multipoint services defined by T.122.
T.126Multipoint still-image and annotation protocol: Definitions for collaborative data sharing, image sharing, graphic display information, and image exchange in a multipoint conference.
T.127This standard defines how files are transferred simultaneously among conference participants. T.127 enables one or more files to be selected and transmitted in compressed or uncompressed form to all or selected participants during a conference.
T.128This standard defines how application sharing orders are transmitted.


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