Internationalized country code TLDs
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 oralphabet, 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,^[5] 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 languages.^{[6]
Infrastructure domain
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 forreverse DNS lookup, it was found impractical to retire it, and is used today exclusively for Internet infrastructure purposes such as in-addr.arpa for IPv4 and ip6.arpa for IPv6 reverse DNS resolution, uri.arpa and urn.arpa for the Dynamic Delegation Discovery System, and e164.arpa 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
RFC 2606 reserves the following four top-level domain names to avoid confusion and conflict.[7] They may be used for various specific purposes however, with the intention that these should not occur in production networks within 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
The test domain has seen usage by ICANN in the testing of internationalized domain names, a program started in 2007.[8][9]
xn—kgbechtv       Arabic (إختبار)
xn—hgbk6aj7f53bba Persian (آزمایشی)
xn—0zwm56d        Chinese, simplified (测试)}
xn—g6w251d        Chinese, traditional (測試)
xn—80akhbyknj4f   Cyrillic (испытание)
xn—11b5bs3a9aj6g  Hindi (परीक्षा)
xn—jxalpdlp       Greek (δοκιμή)
xn—9t4b11yi5a     Korean (테스트)
xn—deba0ad        Yiddish, Hebrew (טעסט)
xn—zckzah         Japanese (テスト)
xn—hlcj6aya9esc7a Tamil (பரிட்சை)
Historical domains
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 nato.int instead. The nato TLD, no longer used, was finally removed in July 1996.
Other historical TLDs are cs for Czechoslovakia (now cz for Czech Republic and sk for Slovak Republic), dd for East Germany (using de after reunification of Germany), yu for SFR Yugoslavia (now: ba for Bosnia and Herzegovina, hr forCroatia, me for Montenegro, mk for Macedonia, rs for Serbia and si for Slovenia), and zr for Zaire (now cd forDemocratic Republic of the Congo). In contrast to these, the TLD su has remained active despite the demise of theSoviet Union that it represents.