Contents 1 History 2 Types 3 Internationalized country code TLDs 4 Infrastructure domain 5 Reserved domains 6 Historical domains 7 Proposed domains 8 Alternative DNS roots 9 Pseudo-domains 10 See also 11 Further reading 12 References 13 External links

History[edit] Originally, the top-level domain space was organized into three main groups: Countries, Categories, and Multiorganizations.[12] An additional temporary group consisted of only the initial DNS domain, arpa,[13] and was intended for transitional purposes toward the stabilization of the domain name system.

Types[edit] As of 2015, IANA distinguishes the following groups of top-level domains:[14] infrastructure top-level domain (ARPA): This group consists of one domain, the Address and Routing Parameter Area. It is managed by IANA on behalf of the Internet Engineering Task Force for various purposes specified in the Request for Comments publications. generic top-level domains (gTLD): Top-level domains with three or more characters restricted generic top-level domains (grTLD): These domains are managed under official ICANN accredited registrars. sponsored top-level domains (sTLD): These domains are proposed and sponsored by private agencies or organizations that establish and enforce rules restricting the eligibility to use the TLD. Use is based on community theme concepts; these domains are managed under official ICANN accredited registrars. country-code top-level domains (ccTLD): Two-letter domains established for countries or territories. With some historical exceptions, the code for any territory is the same as its two-letter ISO 3166 code. internationalized country code top-level domains (IDN ccTLD): ccTLDs in non-Latin character sets (e.g., Arabic, Cyrillic, Hebrew, or Chinese). test top-level domains (tTLD): These domains were installed under .test for testing purposes in the IDN development process; these domains are not present in the root zone. Countries are designated in the Domain Name System by their two-letter ISO country code;[15] there are exceptions, however (e.g., .uk). This group of domains is therefore commonly known as country-code top-level domains (ccTLD). Since 2009, countries with non–Latin-based scripts may apply for internationalized country code top-level domain names, which are displayed in end-user applications in their language-native script or alphabet, but use a Punycode-translated ASCII domain name in the Domain Name System. Generic top-level domains (formerly Categories) initially consisted of gov, edu, com, mil, org, and net. More generic TLDs have been added, such as info. The authoritative list of currently existing TLDs in the root zone is published at the IANA website at

Internationalized country code TLDs[edit] An internationalized country code top-level domain (IDN ccTLD) is a top-level domain with a specially encoded domain name that is displayed in an end user application, such as a web browser, in its language-native script or alphabet, such as the Arabic alphabet, or a non-alphabetic writing system, such as Chinese characters. IDN ccTLDs are an application of the internationalized domain name (IDN) system to top-level Internet domains assigned to countries, or independent geographic regions. ICANN started to accept applications for IDN ccTLDs in November 2009,[16] and installed the first set into the Domain Names System in May 2010. The first set was a group of Arabic names for the countries of Egypt, Saudi Arabia, and the United Arab Emirates. By May 2010, 21 countries had submitted applications to ICANN, representing 11 scripts.[17]

Infrastructure domain[edit] The domain arpa was the first Internet top-level domain. It was intended to be used only temporarily, aiding in the transition of traditional ARPANET host names to the domain name system. However, after it had been used for reverse DNS lookup, it was found impractical to retire it, and is used today exclusively for Internet infrastructure purposes such as for IPv4 and for IPv6 reverse DNS resolution, and for the Dynamic Delegation Discovery System, and for telephone number mapping based on NAPTR DNS records. For historical reasons, arpa is sometimes considered to be a generic top-level domain.

Reserved domains[edit] RFC 6761 reserves the following four top-level domain names to avoid confusion and conflict.[18] Any such reserved usage of those TLDs should not occur in production networks that utilize the global domain name system: example: reserved for use in examples invalid: reserved for use in obviously invalid domain names localhost: reserved to avoid conflict with the traditional use of localhost as a hostname test: reserved for use in tests RFC 6762 reserves the use of .local for link-local host names that can be resolved via the Multicast DNS name resolution protocol.[19] RFC 7686 reserves the use of .onion for the self-authenticating names of Tor hidden services. These names can only be resolved by a Tor client because of the use of onion routing to protect the anonymity of users.[20]

Historical domains[edit] In the late 1980s, InterNIC created the nato domain for use by NATO. NATO considered none of the then existing TLDs as adequately reflecting their status as an international organization. Soon after this addition, however, InterNIC also created the int TLD for the use by international organizations in general, and persuaded NATO to use the second level domain instead. The nato TLD, no longer used, was finally removed in July 1996. Other historical TLDs are cs for Czechoslovakia (now using cz for Czech Republic and sk for Slovak Republic), dd for East Germany (using de after reunification of Germany), yu for SFR Yugoslavia (now using ba for Bosnia and Herzegovina, hr for Croatia, me for Montenegro, mk for Macedonia, rs for Serbia and si for Slovenia), and zr for Zaire (now cd for Democratic Republic of the Congo). In contrast to these, the TLD su has remained active despite the demise of the Soviet Union that it represents. ICANN's ccNSO is working on a policy for retirement of ccTLDs that have been removed from ISO-3166 under the chairmanship of Nigel Roberts.

Proposed domains[edit] Further information: Proposed top-level domain Around late 2000, when ICANN discussed and finally introduced[21] aero, biz, coop, info, museum, name, and pro TLDs, site owners 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 US service providers under the US Communications Decency Act of 1996. Several options were proposed including xxx, sex and adult.[22] The .xxx domain went live in 2011. An older proposal consisted of seven new gTLDs: arts, firm, info, nom, rec, shop, and web.[23] Later biz, info, museum, and name covered most of these old proposals. During the 32nd International Public ICANN Meeting in Paris in 2008, ICANN started a new process of TLD naming policy to take a "significant step forward on the introduction of new generic top-level domains."[24] This program envisioned the availability of many new or already proposed domains, as well as a new application and implementation process.[25] Observers believed that the new rules could result in hundreds of new gTLDs being registered.[26] On 13 June 2012, ICANN announced nearly 2,000 applications for top-level domains, which began installation throughout 2013.[27][28] Donuts Inc. invested $57 million in more than 300 applications[29][30] while Famous Four Media applied for 61 new domains.[31] The first seven – bike, clothing, guru, holdings, plumbing, singles, and ventures – were released in 2014.[32]

Alternative DNS roots[edit] Further information: Alternative DNS root ICANN's slow progress in creating new generic top-level domains, and the high application costs associated with TLDs, contributed to the creation of alternate DNS roots with different sets of top-level domains. Such domains may be accessed by configuration of a computer with alternate or additional (forwarder) DNS servers or plugin modules for web browsers. Browser plugins detect alternate root domain requests and access an alternate domain name server for such requests.

Pseudo-domains[edit] Main article: Pseudo-top-level domain Several networks, such as BITNET, CSNET, UUCP, existed that were in widespread use among computer professionals and academic users, but were not interoperable directly with the Internet and exchanged mail with the Internet via special email gateways. For relaying purposes on the gateways, messages associated with these networks were labeled with suffixes such as bitnet, oz, csnet, or uucp, but these domains did not exist as top-level domains in the public Domain Name System of the Internet. 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, and pseudo-domains now largely survive as historical relics. One notable exception is the 2007 emergence of SWIFTNet Mail, which uses the swift pseudo-domain.[33] The anonymity network Tor formerly used the top-level pseudo-domain onion for Tor hidden services, which can only be reached with a Tor client because it uses the Tor onion routing protocol to reach the hidden service to protect the anonymity of users. However, the pseudo-domain became officially reserved in October 2015. i2p provides a similar hidden pseudo-domain, .i2p. BT hubs use the top-level pseudo-domain home for local DNS resolution of routers, modems and gateways.

See also[edit] Domain hack List of Internet top-level domains Public Suffix List Domain name registrar Second-level domain

Further reading[edit] Addressing the World: National Identity and Internet Country Code Domains, edited by Erica Schlesinger Wass (Rowman & Littlefield, 2003, ISBN 0-7425-2810-3) examines connections between cultures and their ccTLDs. Ruling the Root by Milton Mueller (MIT Press, 2001, ISBN 0-262-13412-8) discusses TLDs and domain name policy more generally.

References[edit] ^ "Delegation Record for .ARPA". Internet Corporation for Assigned Names and Numbers (ICANN). Retrieved 10 November 2015.  ^ "Delegation Record for .BLUE". Internet Corporation for Assigned Names and Numbers (ICANN). Retrieved 10 November 2015.  ^ "Why .BLUE?". Retrieved 10 November 2015.  ^ "Delegation Record for .OVH". Internet Corporation for Assigned Names and Numbers (ICANN). Retrieved 10 November 2015.  ^ "Delegation Record for .NAME". Internet Corporation for Assigned Names and Numbers (ICANN). Retrieved 10 November 2015.  ^ "Delegation Record for .AC". Internet Corporation for Assigned Names and Numbers (ICANN). Retrieved 10 November 2015.  ^ "Delegation Record for .ZW". Internet Corporation for Assigned Names and Numbers (ICANN). Retrieved 10 November 2015.  ^ "Delegation Record for .AERO". Internet Corporation for Assigned Names and Numbers (ICANN). Retrieved 10 November 2015.  ^ "Delegation Record for .ไทย". Internet Corporation for Assigned Names and Numbers (ICANN). Retrieved 23 February 2017.  ^ Postel, Jon (March 1994). "Domain Name System Structure and Delegation". Request for Comments. Network Working Group. Retrieved 7 February 2011. This memo provides some information on the structure of the names in the Domain Name System (DNS), specifically the top-level domain names; and on the administration of domains.  ^ "Root Zone Database". Interxxx Assigned Numbers Authority.  ^ Postel, J.; Reynolds, J. (October 1984). "Domain Requirements". Request for Comments. Network Working Group. Retrieved 7 February 2011.  ^ Postel, J. (October 1984). "Domain Name System Implementation Schedule - Revised". Request for Comments. Network Working Group. Retrieved 7 February 2011. This memo is a policy statement on the implementation of the Domain Style Naming System in the Internet. This memo is an update of RFC-881, and RFC-897. This is an official policy statement of the IAB and the DARPA.  ^ "IANA root zone database". Internet Assigned Numbers Authority. Retrieved 2015-11-10.  ^ Codes for the Representation of Names of Countries, ISO-3166, International Organization for Standardization. (May 1981) ^ "ICANN Bringing the Languages of the World to the Global Internet" (Press release). Internet Corporation For Assigned Names and Numbers (ICANN). 30 October 2009. Retrieved 30 October 2009.  ^ "'Historic' day as first non-Latin web addresses go live". BBC News. 6 May 2010. Retrieved 7 May 2010.  ^ RFC 6761, Special-Use Domain Names, S. Cheshire, M. Krochmal, The Internet Society (February 2013) ^ RFC 6762, Multicast DNS, S. Cheshire, M. Krochmal, The Internet Society (February 2013) ^ RFC 7686, The ".onion" Special-Use Domain Name, J. Appelbaum, A. Muffett, The Internet Society (October 2015) ^ "InterNIC FAQs on New Top-Level Domains". 2002-09-25. Retrieved 2013-03-28.  ^ RFC 3675: .sex Considered Dangerous ^ (historical) gTLD MoU ^ "32nd International Public ICANN Meeting". ICANN. 22 June 2008.  ^ "New gTLD Program". ICANN. Retrieved 15 June 2009.  ^ ICANN Board Approves Sweeping Overhaul of Top-level Domains, CircleID, 26 June 2008. ^ "The Top 10 Proposed New Top Level Domains So Far". Retrieved 12 June 2012.  ^ "Reveal Day 13 June 2012 – New gTLD Applied-For Strings". Retrieved 2013-03-28.  ^ "Donuts full application list" (PDF). Donuts Inc. Archived from the original (PDF) on 28 March 2014. Retrieved 18 August 2013.  ^ Natasha Singer (17 August 2013). "When You Can't Tell Web Suffixes Without a Scorecard". The New York Times. Retrieved 18 August 2013.  ^ "List of 61 new strings applied for Famous Four Media".  ^ "What the new top-level domains from ICANN mean for you - Digital Trends". Digital Trends. 5 February 2014.  ^ "SWIFTNet Mail now available". SWIFT. 16 May 2007. Retrieved 3 January 2010. 

External links[edit] Wikimedia Commons has media related to Top level domains. IANA TLD List IANA List of TLDs on the DNS Root Zone Articles on CircleID about TLDs "Top-Level Domain Names by Host Count". ISC. January 2008. Retrieved 7 August 2008.  TLDs accepted in 2012 v t e List of generic top-level domains Current General .bar .bible .biz .church .club .college .com .design .download .eco .eus .google .green .hiv .info .kaufen .kiwi .lat .lgbt .moe .name .net .ninja .ngo .one .ong .ooo .org .pro .wiki .wtf .xyz Sponsored .aero .asia .cat .coop .edu .gov .int .jobs .mil .mobi .museum .post .tel .travel .xxx Geographic .africa .alsace .amsterdam .berlin .brussels .bzh .cymru .frl .gal .gent .irish .ist .istanbul .kiwi .krd .london .miami .nyc .paris .quebec .rio .saarland .scot .tokyo .vlaanderen .wales .wien Infrastructure .arpa Deleted/retired .nato Reserved .example .invalid .local .localhost .onion .test Proposed Locations .bcn .lat .бг Language and nationality .eng .sic .бг Technical .geo .mail .web Business .shop Other .art .kid .kids .music Country code top-level domains Retrieved from "" Categories: Domain name systemIdentifiersInternet governanceTop-level domainsHidden categories: Pages using RFC magic linksUse dmy dates from July 2012Commons category with local link different than on Wikidata

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Mobile Station Roaming NumberTLD (disambiguation)Country Code Top-level DomainList Of Internet Top-level Domains.arpaInternet Architecture Board.blueAfilias.ovhOVHAFNIC.nameVeriSign.acAscension Island.zwInternet In Zimbabwe.aeroSITA (IT Company).ไทยDomain NameDomain Name SystemInternetDNS Root ZoneDomain NameFully Qualified Domain Corporation For Assigned Names And NumbersInternet Assigned Numbers AuthorityDNS Root ZoneCountry-code Top-level DomainGeneric Top-level DomainSponsored Top-level DomainsUnsponsored Top-level DomainsTop-level Engineering Task ForceRequest For CommentsGeneric Top-level DomainSponsored Top-level DomainCountry Code Top-level DomainCountryList Of Dependent TerritoriesISO 3166Internationalized Country Code Top-level Domain.test.testISO 3166-1 Alpha-2.ukCountry-code Top-level DomainInternationalized Country Code Top-level DomainPunycodeGeneric Top-level Of Internet Top-level DomainsInternationalized Country Code Top-level DomainWeb BrowserAlphabetArabic AlphabetWriting SystemChinese CharacterInternationalized Domain Name.arpaReverse DNS LookupIPv4Dynamic Delegation Discovery SystemTelephone Number MappingNAPTR DNS.onionTor (anonymity Network)Tor (anonymity Network)Onion RoutingInterNIC.natoNATOInternational Republic.skSlovak Republic.ddEast Germany.deReunification Of Germany.yuSocialist Federal Republic Of Yugoslavia.baBosnia And Herzegovina.hrCroatia.meMontenegro.mkRepublic Of Macedonia.rsSerbia.siSlovenia.zrZaire.cdDemocratic Republic Of The Congo.suSoviet UnionICANNCcNSOCcTLDISO-3166Nigel RobertsProposed Top-level Decency Inc.Alternative DNS RootGeneric Top-level DomainPseudo-top-level DomainBITNETCSNETUUCP.bitnet.oz.csnet.uucpDomain Name SystemSociety For Worldwide Interbank Financial TelecommunicationTor (anonymity Network).onionTor Hidden ServiceOnion RoutingI2pBritish TelecomDomain HackList Of Internet Top-level DomainsPublic Suffix ListDomain Name RegistrarSecond-level DomainInternational Standard Book NumberSpecial:BookSources/0-7425-2810-3International Standard Book NumberSpecial:BookSources/0-262-13412-8Jon PostelInternet Assigned Numbers AuthorityInternet Systems ConsortiumTemplate:Generic Top-level DomainsTemplate Talk:Generic Top-level DomainsList Of Internet Top-level DomainsGeneric Top-level DomainGeneric Top-level And (domain).NGO And Top-level Domain.example.invalid.local.localhost.onion.testProposed Top-levelбг Code Top-level DomainHelp:CategoryCategory:Domain Name SystemCategory:IdentifiersCategory:Internet GovernanceCategory:Top-level DomainsCategory:Pages Using RFC Magic LinksCategory:Use Dmy Dates From July 2012Category:Commons Category With Local Link Different Than On WikidataDiscussion About Edits From This IP Address [n]A List Of Edits Made From This IP Address [y]View The Content Page [c]Discussion About The Content Page [t]Edit This Page [e]Visit The Main Page [z]Guides To Browsing WikipediaFeatured Content – The Best Of WikipediaFind Background Information On Current EventsLoad A Random Article [x]Guidance On How To Use And Edit WikipediaFind Out About WikipediaAbout The Project, What You Can Do, Where To Find ThingsA List Of Recent Changes In The Wiki [r]List Of All English Wikipedia Pages Containing Links To This Page [j]Recent Changes In Pages Linked From This Page [k]Upload Files [u]A List Of All Special Pages [q]Wikipedia:AboutWikipedia:General Disclaimer

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