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Study on Technical Use of Root Zone Label Generation Rules

Open Date: 2 August 2018 Close Date: 11 September 2018
Originating Organization:

Global Domains Division

Categories/Tags: Top-Level Domains
Brief Overview:

Second version of the Root Zone Label Generation Rules (RZ-LGR-2) was released in August 2017, integrating six script proposals, as other LGR script proposals are being finalized. The Root Zone Label Generation Rules Study Group (RZ-LGR-SG) has been constituted to study and make recommendations for the technical use of RZ-LGR in a harmonized way across Internationalized Domain Name (IDN) Top-Level Domains (TLDs). RZ-LGR-SG has identified its scope of work [PDF, 128 KB], which is being shared with the community. The SG seeks feedback from the community on whether the questions identified are all relevant for this study and whether there are any other issues it should also consider. RZ-LGR-SG will take into account the community input to finalize the scope of its work, develop the related recommendations and share these recommendations with the community before finalization.


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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"""" is not an IDN."