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Asynchronous Transfer Mode
Asynchronous Transfer Mode (ATM) is a telecommunications standard defined by the American National Standards Institute and International Telecommunication Union Telecommunication Standardization Sector (ITU-T, formerly CCITT) for digital transmission of multiple types of traffic. ATM was developed to meet the needs of the Broadband Integrated Services Digital Network as defined in the late 1980s,[1] and designed to integrate telecommunication networks. It can handle both traditional high-throughput data traffic and real-time, low-latency content such as telephony (voice) and video.[2][3] ATM provides functionality that uses features of circuit switching and packet switching networks by using asynchronous time-division multiplexing.[4][5] ATM was seen in the 1990s as a competitor to Ethernet and networks carrying IP traffic as, unlike Ethernet, it was faster and designed with quality-of-service in mind, but it fell out of favor once Ethernet reached speeds of 1 gigabits per second.[6]
In the Open Systems Interconnection (OSI) reference model data link layer (layer 2), the basic transfer units are called frames. In ATM these frames are of a fixed length (53 octets) called cells. This differs from approaches such as Internet Protocol (IP) (OSI layer 3) or Ethernet (also layer 2) that use variable-sized packets or frames. ATM uses a connection-oriented model in which a virtual circuit must be established between two endpoints before the data exchange begins.[5] These virtual circuits may be either permanent (dedicated connections that are usually preconfigured by the service provider), or switched (set up on a per-call basis using signaling and disconnected when the call is terminated).
The ATM network reference model approximately maps to the three lowest layers of the OSI model: physical layer, data link layer, and network layer.[7] ATM is a core protocol used in the synchronous optical networking and synchronous digital hierarchy (SONET/SDH) backbone of the public switched telephone network and in the Integrated Services Digital Network (ISDN) but has largely been superseded in favor of next-generation networks based on IP technology. Wireless and mobile ATM never established a significant foothold.
- ^ Cite error: The named reference
bisdnwas invoked but never defined (see the help page). - ^ Telcordia Technologies, Telcordia Notes on the Network, Publication SR-2275 (October 2000)
- ^ ATM Forum, The User Network Interface (UNI), v. 3.1, ISBN 0-13-393828-X, Prentice Hall PTR, 1995, page 2.
- ^ "Recommendation I.150, B-ISDN Asynchronous Transfer Mode functional characteristics". ITU.
- ^ a b McDysan (1999), p. 287.
- ^ An Introduction to ATM Networks. John Wiley & Sons. 28 November 2001. ISBN 978-0-471-49827-8.
- ^ McDysan, David E. and Spohn, Darrel L., ATM : Theory and Application, ISBN 0-07-060362-6, McGraw-Hill series on computer communications, 1995, page 563.
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