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ICANN Successfully Conducts Laboratory Tests of Internationalised Domain Names

In October, 2006, ICANN engaged Autonomica AB of Stockholm, Sweden, to develop, conduct, and report on the results of laboratory testing of internationalized top-level domains in a setting corresponding to the public root. Quoting from their report,

Autonomica AB has, under a contract with ICANN, investigated whether the addition of top level domains containing encoded internationalized characters (so called IDNs) would have any impact on the operations of the root name servers providing delegations, or the iterative mode resolvers used to look up the information. No impact at all could be detected. All involved systems behaved exactly as expected.

Internationalized domain names (IDNs) are domain names containing characters other than those based on the ASCII character sets. Such non-ASCII characters include those available in right-to-left scripts (e.g., Arabic) and non-alphabetic scripts (e.g., Mandarin Chinese). ICANN is actively involved in the efforts to make these available at the top level—that is, so that an entire domain name can be rendered in local characters. The global deployment of IDNs will enhance the local Internet experience in large regions of the world by enabling people to share and access information or use services offered in their own languages.

The laboratory technical test is one of the prerequisites to eventual insert internationalized top level labels in the root zone. This test is intended to determine the viability of internationalized top-level names and the effect they may have on the DNS. The work was done by replicating the root server environment. The test intentionally did not incorporate the end-user perspective or a live root test.

Autonomica reported successful insertion using two major server implementations used by most root server operators: BIND and NSD.

The test design was finalized in December of 2006 following a public comment period. The test procedure was published so that others can replicate the test.

Details of the test setup and design can be found here.

Details of the test result can be found here. [PDF, 73K]

For any questions or request for additional details of the test design and result please contact Tina Dam at

For further information around ICANN’s IDN Program please visit

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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."