ATM (Asynchronous Transfer Mode) is network technology that appeared at the beginning of the 1990s to handle voice, video and data transport with a guaranteed quality of service.
ATM uses a switching technique that is midway between circuit switching (telephony) and packet switching (X25). The cells are switched within the hardware, defining virtual circuits.
The information is sent in fixed length packets called "cells". 53 bits of which 5 header bits.
Current switches support 16 ports at 155Mbit/s or 24 ports at 100Mbit/s, giving a total of 2.4Gbit/s.