DNS zone

The individual domains of this tree may serve as delegation points for administrative authority and management.

However, it is usually desirable to implement fine-grained delegation boundaries so that multiple sub-levels of a domain may be managed independently.

[1] A DNS zone is implemented in the configuration system of a domain name server.

Historically, it is defined in the zone file, an operating system text file that starts with the special DNS record type Start of Authority (SOA) and contains all records for the resources described within the zone.

Similarly, an organization in charge of a lower-level domain may operate its namespace and subdivide its space.

Each delegation confers essentially unrestricted technical autonomy over the allocated space.

DNS zones contain the records for mapping domain names to IP addresses or other information.

Such reverse zones are maintained in the Internet Address and Routing Parameter Area (domain arpa).

Intended as a transitional aid to the DNS, deleting the domain arpa was later found to be impractical.

Consequently, the name was officially redefined as an acronym for Address and Routing Parameter Area.

For example, 8.8.2.5.5.2.2.0.0.8.1.e164.arpa., which might represent an E.164 telephone number in the ENUM system, might be sub-delegated at suitable boundaries of the name.

If the last name server queried did not contain authoritative data for the target of the CNAME, it would have issued the resolver with yet another referral, this time to the zone "text.wikimedia.org.".