ATM

ATM

ATM (Asynchronous Transfer Mode) attempts to combine the best of packet switching and circuit switching protocols to get fast and reliable transmissions - especially of video and audio - in real-time.

The TCP/IP, Ethernet, Token Ring, X.25 and Frame Relay protocols all use packet switching to send network messages. Messages are broken up into small packets, or frames, before they are sent, and the packets travel individually to their destination, where they are reassembled into the original message.

This strategy is fine for most network traffic because slight delays in a packet's arrival do not matter as long as they arrive in the right order.

For some messages, however, such as video and voice, packets must arrive in real time, and in their proper order for the information to make sense at the other end. This requires circuit switching, as used in traditional telephone systems, where a dedicated channel is established for the duration of the transmission.

By combining packet and circuit switching, ATM achieves fast and reliable transport of time-critical data.