ATM asynchronous transfer mode This standard packet-switching protocol for transmitting and receiving data uses uniform 53-byte cells. (Each cell has a 5-byte address header and 48 bytes of data.) These short, standardized cells can be processed through a digital ATM switch very quickly, allowing for data transmission speeds surpassing 600 mbps. ATM was designed to support multiple services, including voice, graphics, data, and full-motion video. It also allows telephone and cable TV companies to dynamically assign bandwidth to individual customers.