Network Effectiveness Ratio is a measure of the quality of the network without applying the A-party error and B-party busy. NER is designed to express the ability of networks to deliver calls to the far-end terminal. Busy signals and other call failure due to user behavior are counted as "successful call delivery" for NER calculation purposes.
NER expresses the relationship between the number of seizures and the sum of the number of seizures resulting in either an answer message, or a user busy, or a ring no answer, or in the case of ISDN a terminal rejection/unavailability. Unlike ASR, NER excludes the effects of customer behavior and terminal behavior.
NER is expressed in the number of seizures to the total number of successful call deliveries (answered calls, user busy, ring no answer and terminal rejections) combined.
The ratio for one seizure per million successful call deliveries equals 1,000,000:1, or 1,000,000 over 1, or .000001% (1.0^-6)