ASR/ACD

ASR - Answer Seizure Ratio

The ASR is calculated by dividing the number of successfully answered calls by the total number of calls attempted, known as "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 a very good ASR in the 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.