Domain Name System

In the Internet, the Domain Name System (DNS) is a critically important directory service that translates to and from a raw IP address (such as 207.46.197.32) and a domain name (such as microsoft.com). This allows people to interact with software via easier-to-remember domain names instead of numerical IP addresses. More importantly, it allows information to move around on the internet, from host to host, whereas people can still expect to find the information via its domain name. For example, a user need not care if Microsoft Corporation changes the IP address on one of its host computers; all the user needs to know is the domain name microsoft.com, and he of she can then (thanks to DNS) find Microsoft's computers regardless of which IP address the internet has assigned to its computers this year.

DNS illustrates a core concept that has emerged in Computer science called late binding. Using this approach, a user knows only the name of something but not its location (yet), and the user does not need to look up an address until the last instant before reaching for the information, and need not be aware if the actual address has changed since he or she last accessed the information. DNS, introduced into the internet in 1983, is arguably the first successful application of this concept. Late binding is now commonly used in compilers, linkers, and in Digital Object Identifiers (DOI's) in library science.

DNS is a hierarchical database distributed widely across many host computers on the internet. It is also a set of application protocols for interacting with the database. Although the original purpose of DNS was to translate from domain names to IP address (forward DNS), and also to translate backwards from IP addresses to domain names (reverse DNS), there have been recent attempts to expand the purpose and functionality of DNS in the internet.