Wholesale voice quality is measured with a handful of numbers. They appear in every route offer and request, so it helps to know what each one says and what affects it.
| Metric | Meaning | How it is calculated |
|---|---|---|
| ASR | Answer-seizure ratio | Answered calls divided by call attempts, in % |
| ACD | Average call duration | Total answered minutes divided by answered calls |
| PDD | Post-dial delay | Seconds between dialling and hearing the ringback |
| NER | Network effectiveness ratio | Like ASR, but ignores failures caused by the called party (busy, no answer) |
| FAS | False answer supervision | Calls billed as answered that never were. A good route is FAS-free |
ASR
ASR depends on the route but also on your traffic: a list with many wrong numbers lowers ASR on any route. That is why carriers compare ASR on the same traffic. CLI and Local CLI routes usually reach higher ASR than non-CLI routes.
ACD
A sudden drop in ACD can mean calls are being cut. Very short ACD on conversational traffic is a warning sign. Call center traffic naturally has a lower ACD, which is why many routes set a minimum.
PDD
Long post-dial delay makes callers hang up before the phone rings. Values of a few seconds are normal; much longer delays usually mean the call is passing through too many hops.
Using them in a request
When you request a route, give the minimum ASR and ACD and the maximum PDD you can accept. When you offer one, give the figures you measure. We compare both sides when we look for a route. Request or offer a route.
Frequently asked questions
What is a good ASR in VoIP?
There is no single target, because ASR depends on the destination and on your traffic. Conversational traffic on a good route often reaches 40 to 60%, while a dialer campaign calling cold lists can sit far lower on the same route. Compare routes on the same traffic and the same hours, not against a fixed number.
What is a good ACD for call center traffic?
Call center traffic has a lower ACD than conversational traffic because many calls are short. Carriers that accept call center traffic often set a floor of about 25 to 30 seconds. Conversational routes usually show much longer ACD, so a sudden drop on such a route deserves a check for calls being cut.
What is the difference between ASR and ACD?
ASR tells you how many call attempts were answered, as a percentage. ACD tells you how long the answered calls lasted on average. A route needs both: high ASR with very low ACD can mean dropped calls or false answers, while good ACD with low ASR means many calls never connect.
What does NER mean in VoIP?
NER is the network effectiveness ratio. Like ASR it is a percentage of call attempts, but it also counts busy, unanswered and rejected calls as successes, because the network delivered them to the phone. It separates route performance from user behaviour, which makes it a fairer measure when you compare carriers on different number lists.
What causes ASR to drop on a VoIP route?
Either your traffic changed or the route did. New number lists, different calling hours, a caller ID flagged as spam or a new traffic mix lower ASR on any route. Congestion, blocking at the destination or a change of supplier further down the chain point to the route. Comparing NER tells the two apart.
Need a route?
Send the destination, route type and target rate. We reply with what we can deliver.