An international high-speed, high-volume, packet-switch-ing transmission protocol standard. ATM uses short, uniform, 53-byte cells to divide data into efficient, manageable packets for ultrafast switching through a high-per-formance communications network. ATM is the first packet-switched technology designed from the ground up to support integrated voice, video, and data communication applications. High costs often make this transmission mode impractical for K-12 I-TV networks.