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IDN Variant TLD Program – Conclusion of Third Phase

The IDN Variant TLD Program continues to progress towards a future secure and stable delegation of IDN variant TLDs. We are announcing today the conclusion of the third (out of four) phase of the Program with the publication of two reports: the IDN Root Label Generation Rules (LGR) Procedure, and the User Experience Study for Active Variant TLDs.

The Root LGR Procedure defines the process for creating and maintaining the Label Generation Rules (LGR) for the DNS root zone. The project team consisted of a team of Internet community volunteers from across the globe representing multiple scripts and languages, as well as ICANN staff and expert consultants. Following two face-to-face meetings, conference and email work discussions, and numerous community input processes, including two Public Comment processes, the team produced the document entitled "Procedure to Develop and Maintain the Label Generation Rules for the DNS Root Zone in Respect of IDNA Labels" [PDF, 772 KB].

This document provides a procedure for establishing some of the Label Generation Rules for the root zone. The procedure provides a mechanism for creating and maintaining the rules with respect to IDN labels for the root. This mechanism can be used to determine which Unicode code points are permitted for use in U-labels in the root zone, what variants (if any) are possible to allocate in the root zone, and what variants (if any) are automatically blocked. The mechanism is not the last stage in making determinations about IDN labels for the root. Rather, its output is to be consumed by other ICANN procedures that actually determine whether a particular label is allocated to someone, and whether it is delegated in the root.

The User Experience Study examines issues that end-users, system administrators, application developers, and other users might face when IDN variant TLDs are activated. Incorporating inputs from public sessions, a Webinar, and two Public Comment periods, ICANN staff and expert consultants produced the report entitled "Examining the User Experience Implications of Active Variant TLDs" [PDF, 1.38 MB].

The report: 1) summarizes and compares, from a user experience and registry management perspective, variant practices in several ccTLD registries; 2) proposes a set of guiding principles to define an acceptable user experience; and 3) identifies how various user communities (e.g., end users, system/network administrators, application developers, registrants, registrars and registries) will be impacted by active variant top-level domains, and 4) based on 1, 2, and 3, proposes a set of recommendations to ensure the security, stability and acceptable user experience for active variant top-level internationalized domains.

These documents benefited from significant community participation. ICANN wishes to express its gratitude to all of the volunteers, reviewers, commentators, and the subject matter experts who contributed to these reports.

ICANN is holding a public session at the ICANN Beijing meeting on the IDN Variant TLD Program to explain the Procedure and the results from the Study. In the meantime, work continues to ensure a secure and stable delegation of IDN variant TLDs once the IDN Variant TLD Program has finished its work, which is expected by June 2014. The original plan is being followed as indicated by the Board resolution on 25 September 2010 and the IDN ccTLD Fast Track Process.


We found a missing font in the original PDF file that made some characters unreadable in two appendices. The document was republished on 25 March with the issue fixed. No changes were made to the text.


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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."