ATM is a high bandwidth, low-delay, connection-oriented, packet-like switching and multiplexing technique.

Usable capacity is segmented into 53-byte fixed-size cells, consisting of header and information fields, allocated to services on demand. The term "asynchronous" applies, as each cell is presented to the network on a "start-stop" basis, in other words, asynchronously. The access devices, switches and interlinking transmission facilities, of course, are all highly synchronized. ATM is a very high speed transmission technology.