In asynchronous transfer mode (ATM), a dependability parameter expressed as the ratio of the number of lost cells to the number of transmitted cells. Cell loss can occur for reasons that include misdirection of cells by a switch, a congestion problem causing a discard in consideration of buffer capacity, a station exceeding its peak cell rate (PCR) resulting in cell discard, or a cell that exceeds the maximum cell transfer delay (CTD) and arrives too late for processing. CLR applies to all service categories except unspecified bit rate (UBR). See also ATM, buffer, cell, congestion, CTD, PCR, and UBR.