Understanding ASR, ACD and PDD for carrier traffic

Wholesale voice has dozens of quality metrics, but three do most of the work. ASR tells you whether calls connect, ACD tells you whether people stay on the line, and PDD tells you how long callers wait before anything happens. Read them together and most routing problems become obvious.

ASR: answer-seizure ratio

ASR is the share of attempts that were answered. Send 1,000 attempts, get 420 answers, and ASR is 42%. Busy signals, no-answers, congestion and failures all pull it down. There is no universal target: mobile destinations with heavy screening sit lower than business landlines. Compare a route with its own history and with the same destination on other suppliers.

ACD: average call duration

ACD is the average length of answered calls. It shows whether conversations actually happen. A sudden drop in ACD while ASR holds steady is a classic warning sign — calls are answered but end quickly, which can indicate one-way audio, poor quality or false answer supervision upstream.

PDD: post-dial delay

PDD is the time between sending the call and hearing ringback. Long PDD makes callers hang up before the far end even rings, which drags ASR down for reasons unrelated to the recipient. Rising PDD often points to a route hunting through several suppliers before finding one that accepts the call.

Reading common patterns

• Low ASR, normal ACD — recipients are not answering. Check caller ID presentation and time of day.
• Normal ASR, very low ACD — calls connect but drop. Suspect audio problems or false answers.
• Low ASR with long PDD — callers abandon before ringing. The route is hunting or overloaded.
• All three worsen at once — the route is failing. Move traffic and open a case.

Using your own call history

Your portal calculates attempts, ASR, ACD, minutes and spend for any filter: date range, destination, caller ID or call status. Filter one destination over the last 24 hours and compare it with the previous week. Export the CDR when you need to share evidence with the NOC.