Asynchronous Transfer Mode. For most of us, ATM stands for Automatic Teller Machine, the place where you go withdraw money in the middle of the night, but ATM in the networking world is altogether a different kettle offish! ATMs use 53-byte cells to transmit data which due to its extremely small size and when coupled with appropriate ATM switches results in transmission speeds of600 Mbps. This kind of transmission speed can be used to send all types of bandwidth hungry applications like videos and high resolution graphics.