Quality of Service (QoS) parameters
			(and their interpretation)
		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