AAL Service Types
Type 1: A connection-oriented CBR (constant bit rate) service with timing for audio and video applications
Type 2: A connection-oriented VBR (variable bit rate) service for real-time applications where minor loss is acceptable, and for non-real-time VBR, such as transaction processing
Type 3/4: An ABR (available bit rate) service for non-time-critical applications such as LAN internetworking and LAN emulation
Type 5: A UBR (unspecified bit rate) service that provides spare bandwidth to noncritical services such as file transfers