Asynchronous Transfer Mode

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Related to Asynchronous Transfer Mode: Frame relay

asynchronous transfer mode

[‚a¦siŋ·krə·nəs ′tranz·fər ‚mōd]
A high-speed packet-switching technology based on cell-oriented switching and multiplexing that uses 53-byte packets to transfer different types of information, such as voice, video, and data, over the same communications network at different speeds. Abbreviated ATM.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

Asynchronous Transfer Mode

(ATM, or "fast packet") A method for the dynamic allocation of bandwidth using a fixed-size packet (called a cell).

See also ATM Forum, Wideband ATM.

ATM acronyms.

Indiana acronyms.

This article is provided by FOLDOC - Free Online Dictionary of Computing (


(1) See also ATM machine and Adobe Type Manager.

(2) (ATMosphere) A measure of pressure. See atmosphere.

(3) "At the moment." See digispeak.

(4) (Asynchronous Transfer Mode) A local area and wide area network technology stemming from the telephone world that supports quality of service (QoS) for real-time voice and video. In the early 1990s, ATM was touted as the future multimedia transport starting at the desktop. A decade later, ATM was being replaced by Internet protocols (see IP and MPLS). Adapters for PCs were expensive, and standards for connecting legacy networks were confusing. When Gigabit Ethernet debuted at the end of the 1990s with a familiar technology and 10-fold speed increase, ATM's demise as a LAN was assured. However, ATM was deployed as a backbone technology in major telcos and ISPs.

Fixed-Size Cells and Logical Circuits
ATM transmits 53-byte cells that can be processed very quickly, and the small cell ensures that voice and video can be inserted into the stream for real-time transmission. ATM uses switches that establish a logical circuit from end to end. However, unlike the dedicated circuits of legacy telephone switches, unused bandwidth in ATM's circuits can be appropriated as needed. For example, idle bandwidth in a videoconference can be used to transfer data.

Five Service Levels
Constant Bit Rate (CBR) guarantees bandwidth. Real-time Variable Bit Rate (rt-VBR) supports multimedia, and non-real-time Variable Bit Rate (nrt-VBR) is used for bursty traffic. Available Bit Rate (ABR) adjusts bandwidth according to LAN congestion levels, and Unspecified Bit Rate (UBR) provides the best effort for non-critical data. See MPOA.

ATM in the Large Enterprise
ATM was used as a network backbone ("switch fabric") in some large enterprises. The edge device is an Ethernet switch, and the LANE (LAN Emulation) driver converts Ethernet frames into ATM cells. See LANE.

ATM in the Internet
ATM has been used by carriers and ISPs as the backbone between points of presence (POPs) and at interconnecting points (see NAP and MAE). Highly scalable, ATM supports transmission speeds up to 10 Gbps but can run as slow as 9.6 Kbps between ships at sea. When a new ATM switch is added, it is automatically updated using ATM's PNNI routing protocol.

Where ATM Fits In
ATM functions at layer 2 of the OSI model and converts its cells into SONET frames (see OC) or T-carrier frames (see DS).
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References in periodicals archive ?
Asynchronous Transfer Mode (ATM) -- High-speed networking technology that allows transport of fixed-length cells without allocating physical channels for specific connections.
These tests were designed to test and evaluate the new asynchronous transfer mode (ATM) interfaces, the signal/data processor and the REC.
In addition, Sprint is planning a digital telephone network called ION; it is based on a technology called ATM (asynchronous transfer mode), which will carry data, video and voice communications over a standard phone line.
High-performance networking including support for Gigabit Ethernet and Asynchronous Transfer Mode (ATM OC12);
As a systems integrator, this means that the company is responsible in the first construction phase for setting up the central database, a Asynchronous Transfer Mode (ATM) network, and the incorporation of around 30 subsystems.
The company is also acquiring Ascend's GX 500 ATM core switches for its carrier-class network and is using fiber from a variety of vendors and employing a network design that will support wave division multiplexing, asynchronous transfer mode and other high-capacity methodologies.
The data networking environment offers Internet access and the capacity to install an asynchronous transfer mode (ATM) network for future increased bandwidth demands.
The interior includes generous space for each department and executive offices, a health and fitness center, a CTI (Computer Telephone Integration) system, and a fiber-optic ATM (Asynchronous Transfer Mode) cable for speedy and efficient retrieval and processing of information.
Asynchronous transfer mode (ATM) networks simultaneously can transport multimedia data -- the digital components of text, graphics, audio, and video that create an interactive on-line experience -- from one computer to another at very high speed.
The Alcatel 1603/12 SM can operate at both the 155 Mbit/s and 622 Mbit/s line rates from a single shelf and features a range of configurations and applications, such as, simultaneous grooming of VT (virtual tributary), STS, and ATM (asynchronous transfer mode) circuits.
Although asynchronous transfer mode (ATM) will ultimately replace modern-type connections, integrated services digital network (ISDN) technology will be more easily available and affordable in more places sooner.

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