This read-write value sets the cell loss ratio (CLR) requirement for this circuit, expressed as a negative exponent of 10 (so a value of 6 means a target CLR of 10^-6), with the default 255 meaning any cell loss ratio is acceptable, i.e., no loss guarantee is requested. This is a QoS contract parameter that influences how the switch prioritizes buffering and scheduling resources for the circuit's traffic to meet a stated loss target. An engineer provisioning a PVC for financial transaction traffic that cannot tolerate cell loss might set cktCLR to a strict value like 9 (target CLR of 10^-9), whereas a best-effort data circuit would be left at the default 255.