The H.323 StandardNetMeeting features support for industry standards set by the International Telecommunications Union (ITU) and the Internet Engineering Task Force (IETF), as well as other standards organizations.
Standards enable products from different vendors to communicate. The broad industry support for the standards used by NetMeeting (over 60 leading vendors have announced products and services that work with and enhance use of NetMeeting) enables you to connect and communicate with products from different vendors just as people using different makes and models of telephones can communicate.
Among the standards NetMeeting supports are the ITU H.323 standard for audio and video conferencing, the ITU T.120 standard for multipoint data conferencing, and the IETF LDAP standard for directory services. Overview information for these standards is provided in the sections below. For those seeking greater detail, links to conferencing standards organizations are also provided.
Lightweight Directory Access Protocol
Additional conferencing standards information
H.323 is an ITU standard that specifies how terminals (PCs), equipment, and services for multimedia communicate over networks that do not provide a guaranteed quality of service (such as the internet). H.323 terminals and equipment can carry real-time video, voice, and data, or any combination of these elements. Products that use H.323 for audio and video let you connect and communicate with other people over the Internet, just as people using different makes and models of telephones can communicate using the telephone.
H.323 is actually a series of standards that define:
For low bandwidth use, the H.323 standard specifies standard codecs for audio (G.723) and for video (H.263) that enable H.323 products to send and receive voice and video images. H.323 also specifies use of the T.120 standard for data conferencing. More than 120 leading companies in the industry publicly announced their intent to support and implement H.323 in their products and services. This broad support establishes H.323 as the leading solution for audio and video conferencing over the Internet.
The H.323 standard includes the following components:
| H.225.0 | This standard defines a layer that formats the transmitted video, audio, data, and control streams for output to the network and retrieves the received video, audio, data, and control streams from the network. H.225.0 uses the packet format specified by IETF RTP and RTCP specifications for logical framing, sequence numbering, and error detection as part of audio and video transmissions. Support for RTP and RTCP enables the receiving node to synchronize the received packets in the proper order so the user hears or sees the information correctly. |
| H.245 | The H.245 standard provides the call control mechanism that enables H.323-compatible terminals to connect to each other. |
| H.261 | The H.261 standard specifies the format and algorithm for an alternative, higher bandwidth, video codec used to send or receive video images over network connections. |
| H.263 | This standard specifies the format and algorithm for the default video codec used to send or receive video over low-bandwidth network connections. |
| G.711 | The G.711 standard specifies the format and algorithm for an alternative, higher bandwidth, audio codec used to send or receive voice over network connections. |
| G.723 | Audio codec, for 5.3 and 6.3 Kbps modes. |
| G.723.1 | This standard specifies the format and algorithm for the default audio codec used to send or receive voice over low-bandwidth network connections. |
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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:
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.120 | Data protocols for multimedia conferencing which provide an overview of the T.120 series. |
| T.121 | This 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.122 | The 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.124 | Generic Conference Control (GCC): The definition of the application protocol supporting reservations and basic conference control services for multipoint teleconferences. |
| T.125 | This 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.126 | Multipoint still image and annotation protocol: Definitions for collaborative data sharing, image sharing, graphic display information, and image exchange in a multipoint conference. |
| T.127 | This 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.128 | This standard defines how application sharing orders are transmitted. |
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The Lightweight Directory Access Protocol (LDAP), as its name implies, is a standard method for application clients to query and access information stored on directory servers over TCP/IP connections. Typically, a published directory contains data about people or other entities that users can access. The most common examples of paper-based directories are the yellow and white pages of telephone books, which enable a customer to look up the telephone number for a person or company. An example of an electronic directory is a published e-mail address book, which enables an e-mail user to look up a person's e-mail address and other details, such as office location and internal phone extension.
LDAP is derived from the X.500 global directory and the Directory Access Protocol (DAP), a complex access protocol for performing a wide variety of directory functions. LDAP is a lightweight offspring of DAP, shedding the unnecessary features of client-server access scenarios. The result of the weight loss is LDAP, a protocol that greatly simplifies implementation, reduces software complexity, improves performance, and in the process, encourages wider adoption.
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The NetMeeting 2.1 Resource Kit provides detailed information about the conferencing standards used by NetMeeting. You can download the resource kit from the Microsoft NetMeeting web site.
There are also several organizations in the industry responsible for defining, approving, and communicating standards. Some of these organizations are:
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Last Updated: November 1, 1997
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