What do Carrier Errors stand for?
Carrier Error dispositions or status occur when the dialer reaches a number that has been disconnected, is an invalid number, or there is an issue with the carrier route at that time.
The Carrier Error is something that your prospect's carrier provides.
There are 3 main Carrier Errors.
NRD - No Route Destination
NTF - Normal Temporary Failure
NUR - No User Response
For a larger list follow this link http://tmaxdialer.com/bill/knowledgebase/295/CDR-Report-codes-Carrier-Errors-.html