The three numbers
ASR (answer seizure ratio) is the share of call attempts that were answered. ACD (average call duration) is how long answered calls lasted. NER (network effectiveness ratio), defined in ITU-T E.425, is the share of attempts that ended for a reason the network did not cause: answered, busy, not answered or declined. Taken together they separate route problems from list and campaign problems.
| Metric | Formula | What it tells you |
|---|---|---|
| ASR | Answered ÷ attempts | How many calls connect to a person or machine |
| ACD | Billed minutes ÷ answered | Whether conversations are real |
| NER | (Attempts − network failures) ÷ attempts | Whether the network itself is working |
Mapping SIP codes to outcomes
Each failed call ends with a SIP response code. Group them like this before you enter the numbers. The full list, with what each code means for a dialer, is in SIP response codes for dialers.
- Answered:
200 OK. - User busy:
486 Busy Here,600 Busy Everywhere. - No answer or cancelled:
480 Temporarily Unavailable,408 Request Timeout,487 Request Terminated(your dialer hung up first). - Rejected by callee:
603 Decline. - Network failures: every
5xx, plus403,404,484and488. These mean the call never had a chance to reach the person.
Reading the results
There is no single good ASR. It depends on the destination, list quality, time of day and whether you call mobiles or landlines. A clean opt-in list on a CLI route can run well above a cold list on the same route. Compare a route with itself over time, or two routes on the same traffic, rather than with an industry figure.
NER is more absolute. A healthy route sits close to 100% because the network rarely causes failures. Below 95% means one call in twenty dies inside the network, and that is worth a ticket with the carrier, with CDR samples.
Low ASR, healthy NER
The network delivers the calls and people are not answering. Look at list quality, calling hours and caller ID reputation.
Low ASR, low NER
Calls are failing in the network. Check the number format, channel and CPS limits, and look at which 5xx codes come back.
High ASR, very short ACD
If most calls are "answered" but last under 20 seconds, suspect false answer supervision: the route bills calls that never reached a person.
ACD and predictive dialers
Predictive dialers with answering-machine detection produce many short answered calls, because machines are detected and dropped after a few seconds. That pulls ACD down even on a perfect route. Split human and machine answers in your dialer reports if you can, or compare ACD only between routes that carry the same campaign. Short-duration traffic also has its own commercial rules; see short-duration traffic on CC routes.
Measure over at least a few thousand attempts before drawing conclusions. A few hundred calls is too small a sample, and one bad hour can swing the numbers.
Last reviewed by the CLIRoutes routing team. Spotted a numbering change? Tell us.