| T.120 OVERVIEW |
| Multimedia
Teleconferencing Standards
The ITU-T T.120, H.320, H.323, and H.324 standards comprise the core technologies for multimedia teleconferencing. The T.120 standards address Real Time Data Conferencing (Audiographics), the H.320 standards address ISDN Videoconferencing, the H.323 standard addresses Video (Audiovisual) communication on Local Area Networks, and the H.324 standard addresses video and audio communications over low bitrate connections such as POTS modem connections. The IMTC expects to continue to contribute, through its members, to the future enhancement of the standards to incorporate new functionality and capabilities.
The T.120 standards cover the document conferencing and application sharing (sometimes called data conferencing) portion of a multimedia teleconference. The recommendations specify how to efficiently and reliably distribute files and graphical information in real-time during a multipoint multimedia meeting. The objective of the T.120 standards is to assure interoperability between terminals without either participant assuming prior knowledge of the other system; permit data sharing among participants in a multimedia teleconference, including white board image sharing, graphic display information, and image exchange, application sharing, and, specify infrastructure protocols for audiographic or audiovisual applications. The T.120 series governs the audiographic portion of the H.320, H.323, and H.324 series and operates either within these or by itself. The T.120 suite consists of a series of recommendations, which are summarized, along with their current ITU status in Table 1. |
| Table 1: ITU T.120 Standard | ||
| Recommendation | Description | ITU Status (as of Oct. '98) |
| T.120 | Data protocols for multimedia conferencing: This provides an overview of the T.120 series. | Ratified |
| T.121 | Generic Application Template: This provides a guide for development of T.120 application protocols. | Ratified |
| T.122 | Multipoint Communication Service (MCS) Service Description: This describes the multi-point services available to developers | Ratified |
| T.123 | Protocol stacks for audiographic and audiovisual teleconference applications: This specifies transport protocols for a range of networks. | Ratified |
| T.124 | Generic Conference Control (GCC): This defines the application protocol supporting reservations and basic conference control services for multipoint teleconferences. | Ratified |
| T.125 | Multipoint Communication Service (MCS) Protocol specification: This specifies the data transmission protocol for multipoint services. | Ratified |
| T.126 | Multipoint still image and annotation protocol: This defines collaborative data sharing, including white board and image sharing, graphic display information, and image exchange in a multipoint conference. | Ratified |
| T.127 | Multipoint Binary File Transfer Protocol: This defines a method for applications to transmit files in a multipoint conference. | Ratified |
| T.128 | Multipoint application sharing protocol: This defines how participants in a T.120 conference can share local applications such that other conference participants can see the image of the shared application, and use the mouse and keyboard to take control of the shared application as if it were running locally. | Ratified |
| T.134 | Text chat application entity: A T.121 APE definition for a text chat protocol. | Ratified |
| T.135 | User-to-reservation system transactions within a T.120 conference: This defines conferencing reservation protocols in a T.120 environment, typically between a client application and a scheduling systems which reserves resources for multipoint control units (MCUs or "bridges"). | Ratified |
| T.136 | How Remote Device Control and configuration may be performed using T.120 as the transport protocol. | Draft, for decision 4/99 |
| T.140 | Protocol for multimedia application text conversation. The protocol for text chat within T.120, goes with T.134. | Ratified |
| T.VMR | Virtual Meeting Room control. Contains some material from previous T.13x drafts, concentrates on audio + dataconferencing. | Draft |
| As noted in
Table 1, the core T.120 standards are ratified. This includes the Application
or Upper Level Layers (T.126, T.127) and the Infrastructure or Lower Level
Layers (T.122/125, T.123, T.124, T.128, T.134, T.135, T.140).
Work on other recommendations continues in the ITU. Within the IMTC, the Multipoint/Multiparty activity group, Data Conferencing, and API and Protocols activity groups are coordinating submissions. Additionally, the T.120 Interoperability activity group is coordinating and implementing test sessions to verify the interworking of products and services based on these standards. |