VBR - technical definition

In asynchronous transfer mode (ATM), a class of traffic that requires access to time slots at a rate that can vary significantly from time to time. Real-time compressed voice and video and time-sensitive bursty data traffic are examples of VBR traffic. ATM also defines constant bit rate (CBR), non real-time Variable Bit Rate (nrt-VBR), non real-time Variable Bit Rate (nrt-VBR), real-time Variable Bit Rate (rt-VBR), and unspecified bit rate (UBR) traffic classes See also ABR, ATM, CBR, compression, nrt-VBR, real-time, rt-VBR, time slot, and UBR.