In asynchronous transfer mode (ATM), referring to a frame of data presented to an ATM interface for switching. ATM Adaptation Layer 3/4 (AAL3/4) supports message mode service, in which only one IDU is passed. AAL3/4 also supports streaming mode service, in which multiple interface data units (IDUs) are passed in a data stream. An IDU can be up to 65,535 octets in length, with a cyclic redundancy check (CRC) added as part of the trailer. See also AAL3/4, ATM, CRC, frame, IDU, message mode service, octet, streaming mode service, and trailer.