In asynchronous transfer mode (ATM) a type of service for framed data in which only one interface data unit (IDU) is passed. In other words, it is a single-frame message. Message mode service is supported by ATM Adaptation Layer 3/4 (AAL 3/4). AAL 3/4 also supports streaming mode service, which is used for framed data in which multiple IDUs are passed in a data stream. See also AAL3/4, ATM, IDU, and streaming mode service.