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The Domain Name Service (DNS) links names to IP addresses in the Internet and TCP/IP Networks. When you access Web sites on the Internet, you can type the IP address of the site if you know what it is and if you can remember it. But few people do this. Instead, we rely on DNS servers scattered throughout the Internet to translate the well-known names we can remember into IP addresses.

DNS servers are strategically located on the Internet. There is usually one either directly accessible to your system or accessible over as few as one router hop, although several servers may be queried. Most Internet service providers have DNS servers. When you type a domain name in a Web browser, a query is sent to the primary DNS server defined in your Web browser's configuration dialog box (or if no server is specified, a default DNS server).

In the early days of the Internet, when there were hundreds of users and not millions, Jon Postel maintained a list of host names and IP address mappings. The list was stored in an FTP server that others could access. It contained two columns of information: the IP address and the host name. A problem with this scheme was updating the file and making sure that everyone had the latest information. Changes and updates got to be a nightmare. A way was needed to automate the process and to make sure that no two hosts had the same name.

Paul Mockapetris eventually came up with what he called the "Domain Name Scheme." It was hierarchical and distributed. It also allowed one DNS server to query another if it did not know a name. The early DNS documents are RFC 1034 (Domain Names-Concepts and Facilities, November 1987) and RFC 2035 (Domain Names-Implementation and Specification, November 1987).

The Berkeley Internet Name Domain (BIND) is the most common implementation of DNS and is available at the Internet Software Consortium (ISC), which is located at http://www.isc.org.