ASR/ACD

ASR - Answer Seizure Ratio

Its calculated by taking the number of successfully answered calls and dividing by the total number of calls attempted (seizures). Since busy signals and other rejections by the called number count as call failures, the calculated ASR value can vary depending on user behavior. (http://www.voip-info.org/wiki/view/ASR)

60-70% is considered very good ASR in VoIP world.

ACD – Average Call Duration

It is calculated by taking sum of billsec (billable seconds) of answered calls and dividing by amount of these answered calls.