Domain Name System

The domain name system (DNS) stores and associates many types of information with domain names, but most importantly, it translates domain names (computer hostnames) to IP addresses. It also lists mail exchange servers accepting e-mail for each domain. In providing a worldwide keyword-based redirection service, DNS is an essential component of contemporary Internet use.

Useful for several reasons, the DNS pre-eminently makes it possible to attach easy-to-remember domain names (such as "wikipedia.org") to hard-to-remember IP addresses (such as 207.142.131.206). Humans take advantage of this when they recite URLs and e-mail addresses. In a subsidiary function, the domain name system makes it possible for people to assign authoritative names without needing to communicate with a central registrar each time.

History of the DNS

The practice of using a name as a more human-legible abstraction of a machine's numerical address on the network predates even TCP/IP, and goes all the way back to the ARPAnet era. Originally, each computer on the network retrieved a file called HOSTS.TXT from SRI (now SRI International) which mapped an address (such as 192.0.34.166) to a name (such as www.example.net.) The Hosts file still exists on most modern operating systems, either by default or through configuration, and allows users to specify an IP address to use for a hostname without checking the DNS. This file now serves primarily for troubleshooting DNS errors or for mapping local addresses to more organic names. (The Hosts file can also help in ad-blocking, and spyware may utilize it to hijack a computer.) But a system based on a HOSTS.TXT file had inherent limitations, because of the obvious requirement that every time a given computer's address changed, every computer that wanted to communicate with it would need an update to its Hosts file.

The growth of networking called for a more scalable system: one that recorded a change in a host's address in one place only. Other hosts would learn about the change dynamically through a notification system, thus completing a globally accessible network of all hosts' names and their associated IP Addresses. Enter the DNS.

Paul Mockapetris invented the DNS in 1983; the original specifications appear in RFC 882 and 883. In 1987, the publication of RFC 1034 and RFC 1035 updated the DNS specification and made RFC 882 and RFC 883 obsolete. Several more-recent RFCs have proposed various extensions to the core DNS protocols.

Mockapetris wrote the first implementation of DNS. The following year (1984), four Berkeley students — Douglas Terry, Mark Painter, David Riggle and Songnian Zhau — did the first Unix implementation. Ralph Campbell did maintenance of Terry et al's work after that. In 1985, Kevin Dunlap of Digital Equipment Corporation did a major rewrite of the DNS implementation and renamed it BIND. Mike Kavels, Phil Almquist and Paul Vixie have maintained BIND since then. A port of BIND to the Windows NT platform took place in the early 1990s. Due to its long history of security issues, a number of alternative nameserver/resolver programs have been written and distributed by others in recent years.