Supports Class A traffic, which is connection-oriented constant bit rate (CBR) traffic timed between the source and the sink. Such traffic is stream-oriented and intolerant of latency. Isochronous traffic such as digitally encoded, uncompressed voice is supported via AAL 1, which essentially supports the emulation of a T/E-carrier circuit. All such traffic is carefully timed and must depend on a guaranteed rate of network access, transport, and delivery. Such traffic is marked as high-priority in the cell header, as transmission delays could considerably impact presentation quality. See also ATM, CBR, cell, compression, connection-oriented, E-carrier, emulation, header, isochronous, latency, sink, source, stream-oriented, and T-carrier.