Top-level domain 31115 223393378 2008-07-03T21:55:52Z Kbrose 3938795 {{mergefrom|infrastructure top-level domain|date=June 2008}} {{redirect|TLD}} A '''top-level domain''' ('''TLD'''), sometimes referred to as a '''top-level domain name''' ('''TLDN'''), is the last part of an [[domain name|Internet domain name]]; that is, the letters which follow the final dot of any domain name. For example, in the domain name <tt>www.example.com</tt>, the top-level domain is <tt>[[.com|com]]</tt> (or <tt>COM</tt>, as domain names are not [[case-sensitive]]). Management of most top-level domains is delegated to responsible parties or organizations by the [[Internet Corporation for Assigned Names and Numbers]] (ICANN), which operates the [[Internet Assigned Numbers Authority]] (IANA) and is in charge of maintaining the [[DNS root zone]]. IANA currently distinguishes the following groups of top-level domains:<ref>[http://www.iana.org/domains/root/db/], the Internet Assigned Numbers Authority</ref> *[[infrastructure top-level domain]]s ([[.arpa]]) -- This group consists of only one top-level domain, the [[.arpa|Address and Routing Parameter Area]] (.arpa), used for mapping IP addresses back to hostname, for E.164 telephone number mapping to resources [[ENUM]], and other special technical purposes. It is managed by IANA on behalf of the [[Internet Engineering Task Force|IETF]] for various purposes specified in [[Request_for_Comments|RFCs]]. *[[country-code top-level domain]]s (ccTLD) -- Used by a [[country]] or a [[List of dependent territories|dependent territory]]. It is two letters long, for example <tt>[[.us]]</tt> for the [[United States]]. With some historical exceptions, the code for any territory is the same as its two-letter [[ISO 3166]] code. *[[sponsored top-level domain]]s (sTLD) -- These domains are proposed and sponsored by private agencies or organizations that establish and enforce rules restricting the eligibility to use the TLD. *[[generic top-level domain]]s (gTLD) -- Generic domains are essentially open for registration to anyone in the world. *[[generic top-level domain|generic-restricted top-level domains]] -- Similar to generic group, except eligibility is supposed to be restricted and ascertained more stringently. In addition, a group of [[internationalized domain name]] (IDN) top-level domains has been installed for testing purposes. The authoritative list of currently existing TLDs in the root zone can be found at the IANA website at [http://www.iana.org/domains/root/db/ http://www.iana.org/domains/root/db/] and a [[list of Internet top-level domains|Wikipedia list]] exists. ==Historical TLDs== A <tt>[[.nato]]</tt> was added in the late 1980s by the [[Domain name registry|NIC]] for the use of [[NATO]], who felt that none of the then existing TLDs adequately reflected their status as an [[international organization]]. Soon after this addition, however, the NIC created the <tt>[[.int]]</tt> TLD for the use of international organizations, and persuaded NATO to use <tt>nato.int</tt> instead. However, the <tt>nato</tt> TLD, although no longer used, was not deleted until July 1996. Other historical TLDs are <tt>[[.cs]]</tt> for [[Czechoslovakia]] (now <tt>[[.cz]]</tt> for [[Czech Republic]] and [[.sk]] for [[Slovak Republic]]), and <tt>[[.zr]]</tt> for [[Zaire]] (now <tt>[[.cd]]</tt> for [[Democratic Republic of the Congo]]). In contrast to these, the TLD <tt>[[.su]]</tt> has remained active use despite the demise of the [[Soviet Union]] that it represents, though <tt>[[.ru]]</tt> is most commonly used for [[Russia]]n domains. ==Pseudo-domains== In the past the Internet was just one of many [[wide area network|wide-area computer networks]]. Computers not connected to the Internet, but connected to another network such as [[BITNET]], [[CSNET]] or [[UUCP]], could generally exchange e-mail with the Internet via e-mail gateways. When used on the Internet, addresses on these networks were often placed under ''pseudo-domains'' such as <tt>[[.bitnet]]</tt>, <tt>[[.oz]]</tt>, <tt>[[.csnet]]</tt>, and <tt>[[.uucp]]</tt>; however these pseudo-domains implemented in mail server configurations such as [[sendmail.cf]] and were not real top-level domains and did not exist in [[Domain name system|DNS]]. Most of these networks have long since ceased to exist, and although UUCP still gets significant use in parts of the world where Internet infrastructure has not yet become well-established, it subsequently transitioned to using Internet domain names, so pseudo-domains now largely survive as historical relics. One notable exception is the 2007 emergence of [[Society for Worldwide Interbank Financial Telecommunication|SWIFTNet]] Mail, which uses the <tt>[[.swift]]</tt> pseudo-domain.<ref>[http://www.swift.com/index.cfm?item_id=61929 SWIFT - About SWIFT - Press room - SWIFTNet Mail now available<!-- Bot generated title -->]</ref> The anonymity network [[Tor (anonymity network)|Tor]] has a pseudo-domain <tt>[[.onion|onion]]</tt>, which can only be reached with a Tor client because it uses the Tor-protocol ([[onion routing]]) to reach the hidden service in order to protect the anonymity of the domain. <tt>[[.local]]</tt> deserves special mention as it is required by the [[Zeroconf]] protocol. It is also used by many organizations internally, which will become a problem for those users as Zeroconf becomes more popular. Both <tt>[[.site]]</tt> and <tt>[[.internal]]</tt> have been suggested for private usage, but no consensus has yet emerged{{Fact|date=June 2008}}. ==Reserved TLDs== RFC 2606 reserves the following four top-level domain names for various purposes, with the intention that these should never become actual TLDs in the global [[Domain name system|DNS]]: *<tt>[[.example]]</tt> &mdash; reserved for use in examples *<tt>[[.invalid]]</tt> &mdash; reserved for use in obviously invalid domain names *<tt>[[.localhost]]</tt> &mdash; reserved to avoid conflict with the traditional use of <tt>[[localhost]]</tt> *<tt>[[.test]]</tt> &mdash; reserved for use in tests In [[As of 2007|2007]] eleven [[Internationalized domain name|IDN]] test TLDs were created:<ref>[http://idn.icann.org ICANN IDN wiki]</ref><ref>[http://data.iana.org/TLD/tlds-alpha-by-domain.txt IANA (ICANN) list of extant TLDs]</ref> # <tt> .xn--kgbechtv&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </tt>[http://xn--mgbh0fb.xn--kgbechtv/ Arabic] (.إختبار) # <tt> .xn--hgbk6aj7f53bba </tt> [http://xn--mgbh0fb.xn--hgbk6aj7f53bba/ Persian] (.آزمایشی) # <tt> .xn--0zwm56d&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </tt> [http://xn--fsqu00a.xn--0zwm56d/ Chinese, simplified] (.测试) # <tt> .xn--g6w251d&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </tt> [http://xn--fsqu00a.xn--g6w251d/ Chinese, traditional] (.測試) # <tt> .xn--80akhbyknj4f&nbsp;&nbsp; </tt> [http://xn--e1afmkfd.xn--80akhbyknj4f/ Cyrillic] (.испытание) # <tt> .xn--11b5bs3a9aj6g&nbsp; </tt> [http://xn--p1b6ci4b4b3a.xn--11b5bs3a9aj6g/ Hindi] (.परीक्षा) # <tt> .xn--jxalpdlp&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </tt> [http://xn--hxajbheg2az3al.xn--jxalpdlp/ Greek] (.δοκιμή) # <tt> .xn--9t4b11yi5a&nbsp;&nbsp;&nbsp;&nbsp; </tt> [http://xn--9n2bp8q.xn--9t4b11yi5a/ Korean] (.테스트) # <tt> .xn--deba0ad&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </tt> [http://xn--fdbk5d8ap9b8a8d.xn--deba0ad/ Yiddish] (.טעסט) # <tt> .xn--zckzah&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </tt> [http://xn--r8jz45g.xn--zckzah/ Japanese] (.テスト) # <tt> .xn--hlcj6aya9esc7a </tt> [http://xn--zkc6cc5bi7f6e.xn--hlcj6aya9esc7a/ Tamil] (.பரிட்சை) ==Debated TLDs== {{see|Proposed top-level domain}} About the time that [[ICANN]] discussed and finally introduced<ref>[http://www.internic.net/faqs/new-tlds.html InterNIC FAQs on New Top-Level Domains]</ref> <tt>[[.aero]]</tt>, <tt>[[.biz]]</tt>, <tt>[[.coop]]</tt>, <tt>[[.info]]</tt>, <tt>[[.museum]]</tt>, <tt>[[.name]]</tt>, and <tt>[[.pro]]</tt> TLDs, site owners and [[USENET]] users argued that a similar TLD should be made available for adult and pornographic websites to settle the dispute of obscene content on the internet and the responsibility of service providers under the questionable [[Communications Decency Act]] of 1996. Several options were proposed including <tt>[[.xxx]]</tt>, <tt>[[.sex]]</tt> and <tt>[[.adult]]</tt>, but so far ICANN chose not to create them.<ref>[http://tools.ietf.org/html/rfc3675 RFC 3675:] .sex Considered Dangerous</ref> An older proposal<ref>[http://www.gtld-mou.org/docs/faq.html#2.1 (historical) gTLD MoU]</ref> consisted of seven new gTLDs <tt>.arts</tt>, <tt>.firm</tt>, <tt>[[.info]]</tt>, <tt>.nom</tt>, <tt>.rec</tt>, <tt>.shop</tt>, and <tt>[[.web]]</tt>. Later <tt>[[.biz]]</tt>, <tt>[[.info]]</tt>, <tt>[[.museum]]</tt>, and <tt>[[.name]]</tt> covered most of these old proposals. On [[26 June]] [[2008]], [[ICANN]] approved the relaxation of the rules for the introduction of new TLDs. The new rules will allow any public or private entity from anywhere in the world to register any string of letters as a gTLD. Observers believed that the new rule could result in hundreds of new gTLDs registered this year.<ref>[http://www.circleid.com/posts/86269_icann_approves_overhaul_top_level_domains/ ICANN Board Approves Sweeping Overhaul of Top-level Domains], CircleID, 26 June 2008</ref> ==TLDs in alternative roots== {{see|Alternative DNS root}} ICANN's slow progress in creating new [[generic top-level domain|gTLDs]], and the relatively high registration costs associated with several TLDs, contributed to the creation of alternate root servers with their own sets of TLDs. At times, browser plugins have been developed to allow access to some set of "alternative" domain names even when the normal DNS roots are otherwise used. ==References== <references/> *''Addressing the World: National Identity and Internet Country Code Domains'', edited by Erica Schlesinger Wass (Rowman & Littlefield, 2003, ISBN 0-7425-2810-3) [http://www.addressingtheworld.info], examines connections between cultures and their ccTLDs. *''Ruling the Root'' by Milton Mueller (MIT Press, 2001, ISBN 0-262-13412-8) [http://mitpress.mit.edu/catalog/item/default.asp?sid=5BA098F1-E04D-4D4D-98EE-4BF1DDA75B9C&ttype=2&tid=8809], discusses TLDs and domain name policy more generally. <table align="right" border="0"><tr><td>{{GTLD}}</td></tr></table> ==See also== * [[List of Internet top-level domains]] * [[Domain Name System]] * [[Proposed top-level domain]] ==External links== *[http://www.circleid.com/topics/top_level_domains Articles on CircleID about TLDs] *[http://data.iana.org/TLD/tlds-alpha-by-domain.txt IANA TLD List] *[http://www.domainrates.org Database of all TLDs with pricing guide] {{-}} [[Category:Domain name system]] [[Category:Internet governance]] [[Category:Top-level domains| ]] [[Category:Identifiers]] [[als:Top Level Domain]] [[ar:مجال المستوى الأعلى]] [[an:Dominio d'Internet]] [[ast:Dominiu Internet]] [[be:Дамен верхняга ўзроўню]] [[be-x-old:Дамэн верхняга ўзроўню]] [[bar:Top Level Domain]] [[bs:Najviši Internet domeni]] [[bg:Домейн от първо ниво]] [[ca:Domini de primer nivell]] [[cs:Doména nejvyššího řádu]] [[cy:Ôl-ddodiad rhyngrwyd]] [[da:Top-level internetdomæner]] [[de:Top-Level-Domain]] [[et:Tippdomeen]] [[el:Top-level domain]] [[es:Dominio de nivel superior]] [[eo:Domajno de plej alta nivelo]] [[eu:Goi mailako domeinu]] [[fr:Domaine de premier niveau]] [[fy:Top level domain]] [[gl:TLD (Internet)]] [[ko:최상위 도메인]] [[id:Ranah internet tingkat teratas]] [[is:Rótarlén]] [[it:Dominio di primo livello]] [[he:סיומת אינטרנט]] [[jv:Internet TLD]] [[ka:ინტერნეტის პირველადი დომენი]] [[ku:Top-level domain]] [[lv:Augšējā līmeņa domēns]] [[li:Top-level domain]] [[hu:Legfelső szintű tartomány]] [[ms:Domain peringkat tinggi]] [[nl:Top-level-domein]] [[ja:トップレベルドメイン]] [[no:Toppnivådomene]] [[nn:Toppnivådomene]] [[nrm:TLD]] [[nds:Top Level Domain]] [[pl:Domena najwyższego poziomu]] [[pt:Domínio de topo]] [[ro:TLD]] [[ru:Домен верхнего уровня]] [[sco:Tap-level domain]] [[simple:Top-level domain]] [[sk:Doména najvyššej úrovne]] [[sl:Vrhnja internetna domena]] [[fi:Verkkotunnus]] [[sv:Toppdomän]] [[tt:İnternet TLD]] [[th:โดเมนระดับบนสุด]] [[vi:Tên miền cấp cao nhất]] [[tr:Üst seviye alan adı]] [[uk:Домен верхнього рівня]] [[ur:بلند ترین اسمِ ساحہ]] [[vec:Sufisi Internet de Primo Liveło]] [[fiu-vro:Internetitunnus]] [[yo:Top-level domain]] [[zh:頂級域]]