Asynchronous Transfer Mode (ATM) is a standardized digital data transmission technology. ATM is implemented as a network protocol and was first developed in the mid 1980s.[1] The goal was to design a single networking strategy that could transport real-time video conference and audio as well as image files, text and email.[2] The International Telecommunications Union, American National Standards Institute, European Telecommunications Standards Institute, ATM Forum, Internet Engineering Task Force, Frame Relay Forum and SMDS Interest Group were involved in the creation of the standard.[3]
Asynchronous Transfer Mode is a cell-based switching technique that uses asynchronous time division multiplexing.[4][5] It encodes data into small fixed-sized cells (cell relay) and provides data link layer services that run over OSI Layer 1 physical links. This differs from other technologies based on packet-switched networks (such as the Internet Protocol or Ethernet), in which variable sized packets (known as frames when referencing Layer 2) are used. ATM exposes properties from both circuit switched and small packet switched networking, making it suitable for wide area data networking as well as real-time media transport.[6] ATM uses a connection-oriented model and establishes a virtual circuit between two endpoints before the actual data exchange begins.[7]
ATM is a core protocol used over the SONET/SDH backbone of the Integrated Services Digital Network.
STM-1 (Synchronous Transport Module level-1) is the SDH ITU-T fiber optic network transmission standard. It has a bit rate of 155.52 Mbit/s. The other levels are STM-4, STM-16 and STM-64. Beyond this we have wavelength-division multiplexing (WDM) commonly used in submarine cabling.
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