Domain Name System

In the Internet, the Domain Name System (DNS) is both a distributed database, and set of application protocols, with the original purpose of translating from human-readable domain names to Internet protocol (IP) addresses (i.e., forward DNS) and from addresses to names (i.e., reverse DNS). Over the years, it has taken on more technical and administrative roles. The domain name space, as well as the address spaces both for Internet Protocol version 4 and Internet Protocol version 6 (IPv6) are under the authority of the Internet Corporation for Assigned Names and Numbers (ICANN), with much delegation of administration. The original system only handled IPv4, so one of the first steps for IPv6 support was defining how to represent IPv6 addresses in DNS.

Later roles for DNS include providing additional information for the names and addresses, especially for security; the DNS infrastructure itself needed to be enhanced to be secure and trusted. DNS originally was manually configured, but there have needed to be a variety of extensions to allow dynamic operation, such as the temporary binding of an address to a name.

Domain name structure and schema

• roots
• root server
• anycast
• FQDN
• relative domain name
• primary zone server

Domain naming administration and issues

Name assignment

• registry
• registrars

Implementation

• secondary zone server
• caching-only server
• resolver

DNS protocols

The most basic DNS protocols are the lookup service, which runs over the connectionless User Datagram Protocol, and the zone transfer service, which runs over connection-oriented Transmission Control Protocol. Lookup is a read-only function, while zone update is read-write and should be implemented as a privileged, authenticated operation.

There are also protocols for dynamic update.