Quality of Service (QoS) parameters
Cell Transfer Delay (CTD):     mean CTD < N ms
Cell Delay Variation (CDV):     difference between
upper and lower 10–8 quantiles of CTD < N ms
Cell Loss Ratio (CLR):     < N x 10-7
(less often specified)
Cell Error Ratio (CER):     < N x 10-6
Cell Misinsertion Rate (CMR):     < N / day
Severely Errored Cell Block Ratio (SECBR): < N x 10-4
(and their interpretation)