Asynchronous Transfer Mode

Asynchronous Transfer Mode (ATM) is a <a href="/facts/Telecommunications/vxoj1cxR">telecommunications</a> standard defined by the <a href="/facts/American_National_Standards_Institute/p3d1TQCb">American National Standards Institute</a> and <a href="/facts/International_Telecommunication_Union_Telecommunication_Standardization_Sector/9nJwkPYx">International Telecommunication Union Telecommunication Standardization Sector</a> (ITU-T, formerly CCITT) for digital transmission of multiple types of traffic. ATM was developed to meet the needs of the <a href="/facts/Broadband_Integrated_Services_Digital_Network/3Tu3NtXj">Broadband Integrated Services Digital Network</a> as defined in the late 1980s, and designed to integrate telecommunication networks. It can handle both traditional high-throughput data traffic and <a href="/facts/Real-time_computing/p9HxgL4L">real-time</a>, <a href="/facts/Low-latency/6Bjhn30H">low-latency</a> content such as <a href="/facts/Telephony/2GwTTepw">telephony</a> (voice) and video. ATM provides functionality that uses features of <a href="/facts/Circuit_switching/fJ3vdmAB">circuit switching</a> and <a href="/facts/Packet_switching/olDlDP1R">packet switching</a> networks by using <a href="/facts/Asynchronous_communication/sz5DacK8">asynchronous</a> <a href="/facts/Time-division_multiplexing/tv7bMh1v">time-division multiplexing</a>. ATM was seen in the 1990s as a competitor to <a href="/facts/Ethernet/nMfhU8tU">Ethernet</a> 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.
In the <a href="/facts/OSI_model/oxN9Xhjz">Open Systems Interconnection (OSI) reference model</a> <a href="/facts/Data_link_layer/K9yPufbt">data link layer</a> (layer 2), the basic transfer units are called <a href="/facts/Frame_(networking)/ltGCbJIq">frames</a>. In ATM these frames are of a fixed length (53 <a href="/facts/Octet_(computing)/dqCHsuUF">octets</a>) called cells. This differs from approaches such as <a href="/facts/Internet_Protocol/Qq6VeEal">Internet Protocol</a> (IP) (OSI layer 3) or <a href="/facts/Ethernet/nMfhU8tU">Ethernet</a> (also layer 2) that use variable-sized packets or frames. ATM uses a <a href="/facts/Connection-oriented_model/2yAhgueh">connection-oriented model</a> in which a <a href="/facts/Virtual_circuit/8HqpnTxl">virtual circuit</a> must be established between two endpoints before the data exchange begins. 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 <a href="/facts/Signaling_(telecommunications)/6d4zgUj7">signaling</a> and disconnected when the call is terminated).
The ATM network reference model approximately maps to the three lowest layers of the OSI model: <a href="/facts/Physical_layer/WuATCrVw">physical layer</a>, data link layer, and <a href="/facts/Network_layer/L2jAtJzQ">network layer</a>. ATM is a core protocol used in the <a href="/facts/SONET/SDH/G3LgtGS6">synchronous optical networking and synchronous digital hierarchy</a> (SONET/SDH) backbone of the <a href="/facts/Public_switched_telephone_network/eVrCTDU7">public switched telephone network</a> and in the <a href="/facts/Integrated_Services_Digital_Network/zcV99rUb">Integrated Services Digital Network</a> (ISDN) but has largely been superseded in favor of <a href="/facts/Next-generation_network/AS01E5Tg">next-generation networks</a> based on IP technology. Wireless and mobile ATM never established a significant foothold.

Asynchronous Transfer Mode open-in-new

Asynchronous Transfer Mode