ATM Service Classes
Constant Bit Rate (CBR) - specifies a fixed bit rate for Circuit Emulation (CE)
Variable Bit Rate - Real Time (VBR RT), provides a specified throughput with end-to-end synchronization but data is not sent evenly, used for real-time voice and video
Variable Bit Rate - Non-Real Time (VBR NRT), provides a specified throughput without end-to-end synchronization
Available Bit Rate (ABR) provides a guaranteed minimum capacity but allows data to be bursted at higher capacities when there is excess capacity in the network, ABR services are generally not implemented in ATM networks and services
Unspecified Bit Rate (UBR) does not guarantee any throughput, used for non-time-critical applications, such as file transfers