Editing Asynchronous Transfer Mode (section)

{{short description|Digital telecommunications protocol for voice, video, and data}}
{{Use dmy dates|date=July 2020}}
{{Use American English|date=July 2023}}

[[File:IBM Turboways ATM 155.jpg|thumb|[[IBM]] Turboways ATM 155 [[Peripheral Component Interconnect|PCI]] network interface card]]

'''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,<ref name="bisdn" /> and designed to integrate telecommunication networks. It can handle both traditional high-throughput data traffic and [[Real-time computing|real-time]], [[low-latency]] content such as [[telephony]] (voice) and video.<ref>Telcordia Technologies, ''Telcordia Notes on the Network'', Publication SR-2275 (October 2000)</ref><ref name="ATMF-INTRO">ATM Forum, The User Network Interface (UNI), v. 3.1, {{ISBN|0-13-393828-X}}, Prentice Hall PTR, 1995, page 2.</ref> ATM is a [[cell switching]] technology,<ref>{{cite journal |title=Asynchronous Transfer Mode: An Emerging Network Standard for High-Speed Communications |author=Ronald J. Vetter |journal=Advances in Computers |volume=44 |year=1997| quote=ATM is based on the concept of cell switching. ATM combines the benefits of traditional packet switching (used in today’s data networks) and circuit switching (used in the telephone network). |doi=10.1016/S0065-2458(08)60341-1}}</ref><ref>{{cite web |url=https://www.ibm.com/docs/en/aix/7.1?topic=adapters-atm-technology |title=ATM technology |date=27 August 2024 |publisher=[[IBM]] |quote=Asynchronous Transfer Mode (ATM) is a cell-switching, connection-oriented technology.}}</ref> providing functionality that combines features of [[circuit switching]] and [[packet switching]] networks by using [[asynchronous communication|asynchronous]] [[time-division multiplexing]].<ref>{{cite web|url= http://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-I.150-199902-I!!PDF-E&type=items|title=Recommendation I.150, B-ISDN Asynchronous Transfer Mode functional characteristics |publisher=ITU}}</ref><ref name="McDysan 1999 287">McDysan (1999), p. 287.</ref> 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.<ref>{{cite book | url=https://books.google.com/books?id=ghy9BOw6svMC&dq=atm+network&pg=PP1 | isbn=978-0-471-49827-8 | title=An Introduction to ATM Networks | date=28 November 2001 | publisher=John Wiley & Sons }}</ref>

In the [[OSI model|Open Systems Interconnection (OSI) reference model]] [[data link layer]] (layer 2), the basic transfer units are called ''[[Frame (networking)|frames]]''. In ATM these frames are of a fixed length (53 [[Octet (computing)|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.<ref name="McDysan 1999 287"/> 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 (telecommunications)|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]].<ref name="McDysan-Spohn">McDysan, David E. and Spohn, Darrel L., ''[[iarchive:atmtheoryapplica00mcdy/page/n9/mode/2up|ATM : Theory and Application]]'', {{ISBN|0-07-060362-6}}, McGraw-Hill series on computer communications, 1995, page 563.</ref> ATM is a core protocol used in the [[SONET/SDH|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 network]]s based on IP technology. Wireless and mobile ATM never established a significant foothold.