No Error

No error condition.

Format Error

The name server was unable to interpret the query.

Server Failure

The name server was unable to process this query due to an internal problem.

Non-Existing Domain

Meaningful only for responses from an authoritative name server, this code signifies that the domain name referenced in the query does not exist.

Not Implemented

The name server does not support the requested kind of query.

Query Refused

The name server refuses to perform the specified operation for policy reasons. For example, a name server may not wish to provide the information to the particular requester, or a name server may not wish to perform a particular operation (e.g., zone transfer) for particular data.