Buying termination on rate alone is how contact centres end up with minutes that cost less and deliver nothing. These four metrics are how you tell the difference.
ASR — Answer Seizure Ratio
The percentage of call attempts that are answered. It is the headline quality number for any route.
What counts as good depends entirely on destination and traffic type. A consumer mobile destination might run 35–50% on a healthy route; a B2B destination during business hours can be much higher. The absolute number matters far less than the trend and the comparison against another carrier on the same list.
A sudden ASR drop on a single destination usually means a route change upstream, not a change in your list.
ACD — Average Call Duration
The mean length of connected calls. Read it alongside ASR, never alone.
A route showing high ASR and very low ACD — say answered calls averaging under ten seconds — is the classic signature of false answer supervision, where the carrier signals "answered" before a human actually picks up. You are billed from that moment. The calls look connected in your reporting and produce no conversations.
PDD — Post-Dial Delay
The time between sending the call and hearing ringback. Under three seconds is comfortable; beyond six, callers start hanging up before the phone has rung.
High PDD is often a symptom of a call being passed through several wholesale hops. Every intermediary adds delay and another opportunity for the audio path to degrade. Short routes are usually better routes.
NER — Network Effectiveness Ratio
Similar to ASR but excludes user-driven outcomes like busy and no-answer, so it isolates network failures from human behaviour. When ASR falls but NER holds steady, the problem is your list or your calling window. When both fall together, the problem is the route.
Reading them together
No single metric identifies a bad route. The combinations do:
| Pattern | Likely cause |
|---|---|
| High ASR, very low ACD | False answer supervision |
| Falling ASR, steady NER | List quality or calling-window issue |
| Falling ASR and NER | Route or carrier degradation |
| Rising PDD | Extra wholesale hops inserted upstream |
| Normal metrics, quality complaints | Media path problem — check jitter, loss and MOS |
Insist on visibility
Any carrier worth using will show you these figures per destination in real time and let you export full CDRs. If a provider will only quote you a rate sheet and cannot show live quality data, that reluctance is itself the answer.
Run a test trunk against your existing carrier with the same list, at the same time of day, and compare. It is the only benchmark that reflects your actual traffic.
