What is Domain Name System?
{{IPstack}} {{internet}} The '''Domain Name System''' ('''DNS''') is a system used to convert a computer's [[host name]] into an [[Internet Protocol|IP address]] on the [[Internet]]. For example, if a computer needs to communicate with the web server ''example.net'', your computer needs the IP address of the web server ''example.net''. It is the job of the DNS to convert the host name to the IP address of the web server. It is sometimes called the Internet's [[telephone book]] because it converts a Website's name that people know to a number that the Internet actually uses. The DNS is defined by [[Request for Comments]] (RFC) documents. These are technical documents about [[computer network]]s. The DNS is mainly defined by RFC 1034 and RFC 1035. There are later RFC which define changes to the system. ==Structure== Domain names are made up of one or more parts, or ''labels'' that are joined and kept separate by dots, such as <code>www.example.com</code>. * The label on the right is the ''[[top-level domain]] or TLD.'' For example, the top-level domain of <code>www.example.com</code> is <code>com</code>. * The next one along is the subsection (or subdomain as is the proper word) of the TLD. In <code>example.com</code> this is <code>example</code>. * The furthest to the left is the <code>www</code> which is a subdomain of <code>example</code>. The <code>www</code> means the site is part of the [[World Wide Web]] (NOT the same as the Internet <ref name=WWW>[http://www.webopedia.com/TERM/W/World_Wide_Web.html Webopedia Article on the World Wide Web.]</ref><ref name=Internet>[http://www.webopedia.com/TERM/I/internet.html Webopedia Article on the Internet.]</ref>) * Each label can have 63 letters/numbers (''characters'') and a domain name cannot have more than 253 characters. ==Lookup process== Let us imagine that a PC called ''PC1'' needs to connect to a server named ''Server1''. The following steps describe the basic DNS lookup process.<ref>{{cite book|first=Wendell|last=Odom|title=CCENT/CCNA ICND1 100-105 Offi