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Implementation Notice - Version 3.0 of IDN Guidelines

Following the ICANN Board's acceptance at the October 2011 meeting in Dakar, Senegal, ICANN is today providing notice of implementation for version 3.0 of the Guidelines for Implementation of Internationalized Domain Names. The IDN Guidelines are a list of general standards that many top-level domain registries deploying IDNs are required to follow based on the Internationalized Domain Names for Applications (IDNA) protocol standard from the IETF.

The Guidelines document was developed by IDN Guidelines Revision Working Group (comprised of ccTLD and gTLD registry representatives with IDN experience supported by ICANN staff). The new version modifies the current Version 2.2 to reflect the IDNABIS revision ("IDNA2008 protocol") of the initial IDNA protocol ("IDNA2003"). ICANN previously published a draft version of the guidelines for public comment (see http://www.icann.org/en/public-comment/idn-guidelines-revision-27jul11-en.htm). The ICANN Board of Directors endorsed version 3.0 of the IDN Guidelines during their meeting on 28 October 2011. Registries offering IDN registrations should begin transitioning to version 3.0 of the IDN Guidelines.

The Internationalized Domain Names for Applications (IDNA) protocol is the technical standard for the implementation of IDNs for TLD registries, registrars and software developers that make IDNs available for their customers. The IDNA protocol references and further detail about the 2008 revision can be found here: http://www.icann.org/en/topics/idn/rfcs.htm


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Domain Name System
Internationalized Domain Name ,IDN,"IDNs are domain names that include characters used in the local representation of languages that are not written with the twenty-six letters of the basic Latin alphabet ""a-z"". An IDN can contain Latin letters with diacritical marks, as required by many European languages, or may consist of characters from non-Latin scripts such as Arabic or Chinese. Many languages also use other types of digits than the European ""0-9"". The basic Latin alphabet together with the European-Arabic digits are, for the purpose of domain names, termed ""ASCII characters"" (ASCII = American Standard Code for Information Interchange). These are also included in the broader range of ""Unicode characters"" that provides the basis for IDNs. The ""hostname rule"" requires that all domain names of the type under consideration here are stored in the DNS using only the ASCII characters listed above, with the one further addition of the hyphen ""-"". The Unicode form of an IDN therefore requires special encoding before it is entered into the DNS. The following terminology is used when distinguishing between these forms: A domain name consists of a series of ""labels"" (separated by ""dots""). The ASCII form of an IDN label is termed an ""A-label"". All operations defined in the DNS protocol use A-labels exclusively. The Unicode form, which a user expects to be displayed, is termed a ""U-label"". The difference may be illustrated with the Hindi word for ""test"" — परीका — appearing here as a U-label would (in the Devanagari script). A special form of ""ASCII compatible encoding"" (abbreviated ACE) is applied to this to produce the corresponding A-label: xn--11b5bs1di. A domain name that only includes ASCII letters, digits, and hyphens is termed an ""LDH label"". Although the definitions of A-labels and LDH-labels overlap, a name consisting exclusively of LDH labels, such as""icann.org"" is not an IDN."