A very high speed, connection-oriented (only PVC initially), fixed-length
48-byte (plus 5 bytes of overhead) cell-Switching scheme that is suitable for data as well as digitized voice and video.
Was initially to be used with Synchronous Optical NETwork (SONET) to be the basis for B-ISDN but is now considered a separate technology. Asynchronous because each cell can be independently addressed to allocate bandwidth
between many virtual channels as needed.
Could eliminate the distinction between LAN and WAN, since ATM can be used for
both. WANs will probably first be implemented as private ATM networks, then
become a public offering.
Data are formatted as fixed-length cells so that it is easier to handle them
in hardware (which can juggle cells faster than software). Also fixed-length
cells enable networks to have predictable response times (since you know when the
current cell will finish because you know its length). This isochronous capability is required to handle multimedia traffic (such as digitized voice
and video).
The cells are relatively small to provide short store-and-forward delays per
switch (to reduce network delays, as required for interactive services such as
video conferencing).
Will likely be used as the switching fabric to support frame relay (which currently uses access speeds up to T1) and possibly B-ISDN (which has accesses starting at OC-3).