Asynchronous Transfer Mode
(ATM, or "fast packet", "Asynchronous Transfer Mode Protocol", ATMP) A network protocol that dynamically allocates bandwidth between incoming channels and multiplexes them onto a stream of fixed 53-byte packets (called "cells"). A fixed-size packet simplifies switching and multiplexing. ATM is a connection-oriented protocol. It can use different physical layer transports including SONET, DS3, fiber or twisted pair.