Resolvers operate by sending query packets to a name
server. A query packet contains the following fields:
- Domain name
- Query type
- A query class
RFC 1035 defines the query types and query classes. The
name server attempts to match the three fields of the query packet
to its database. For flexibility, the following wildcard query types
are defined:
- Type
- Description
- ANY
- Indicates any record type for the domain name.
- AXFR
- Indicates the query type used by secondary name servers to transfer
all records in the zone. (The query class is set to IN when using
the AXFR query type.)
- MAILB
- Indicates any mailbox records for the domain name.
The name server can return the following query responses:
- Response
- Description
- Authoritative
- Is returned from a primary or secondary name server. The name
server contains all the domain data used to define the zone for the
specified query.
- BADVERS
- The name server received a request that contained a EDNS0 version
that was not valid.
- Nonauthoritative
- Is returned from a cache kept by a name server. The cache does
not contain the domain data used to define the zone for the specified
query.
- Format Error
- The name server found an error in the query packet sent by the
resolver.
- Name Error
- No resource records of any type (including wildcards) exist for
the domain name specified.
- NXDOMAIN (negative)
- No records of the requested type were found for the domain name
specified.
- Not-implemented
- The name server does not support the type of query requested.
- NOTAUTH
- The name server is not authoritative for the zone.
- NOTZONE
- A dynamic update failed because the name to be updated is not
contained within the given zone.
- NXRRSET
- A dynamic update failed because the prerequisites were not satisfied.
The Resource Record set existed when the prerequiste stated it should
not.
- Referral
- Contains the addresses of other name servers that might be able
to answer the query. A referral response is returned when a recursive
query is not supported, not requested, or cannot be answered because
of network connectivity.
- Refused
- The name server refuses to perform the specified operation. For
example, some root name servers limit zone transfers to a set number
of IP addresses.
- YXDOMAIN
- DNAME mapping failed because the new name was too long.
- YXRRSET
- A dynamic update failed because the prerequisites were not satisfied.
The Resource Record set did not exist when the prerequiste stated
it should.