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ICANN Establishes Forum on Allocation Methods for Single-Letter and Single-Digit Domain Names

(Comment period extended 7 November 2007)

As recommended by the GNSO Council, ICANN is commencing a forum on potential allocation methods for single-letter and single-digit domain names at the second level in gTLD registries. Examples include,,, Since revenue will result from this allocation, comments regarding the potential uses for this revenue are also requested.

ICANN intends to synthesize responses to the forum and present proposed methods for allocation of single-letter and single-digit domain names at the second level for community consideration.

To be considered by ICANN, ideas on potential allocation methods should be submitted to Comments may be viewed at **ICANN is extending the comment period until 23:59 UTC 15 December 2007 on the forum for potential allocation methods for single-letter and single-digit domain names at the second level in gTLD registries. There has been interest in providing additional time so that members of the Internet community that have not previously commented on ICANN topics may do so. 17 comments have been provided to date.

The GNSO Council asked ICANN to initiate a forum on this issue after considering a report of the Council's Reserved Names Working Group (RN-WG), which recommended that “single letters and digits be released at the second level in future gTLDs, and that those currently reserved in existing gTLDs should be released. This release should be contingent upon the use of appropriate allocation frameworks. More work may be needed. In future gTLDs we recommend that single letters and single digits be available at the second (and third level if applicable).” The GNSO is one of ICANN's primary stakeholder-populated policy making bodies. The recommendations of the RN-WG can be found at [PDF, 713K].


Currently, all 16 gTLD registry agreements (.AERO, .ASIA, .BIZ, .CAT, .COM, .COOP, .INFO, .JOBS, .MOBI, .MUSEUM, .NAME, .NET, .ORG, .PRO, .TEL, and .TRAVEL) provide for the reservation of single-letter and single-digit names at the second level. ICANN’s gTLD registry agreements contain the following provision on single-letter and single-digit names. See Appendix 6 of the .TEL Registry Agreement, (“the following names shall be reserved at the second-level: All single-character labels.”).

Letters, numbers and the hyphen symbol are allowed within second level names in both top level and country code TLDs. Single letters and numbers also are allowed as IDNs -- as single-character Unicode renderings of ASCII compatible (ACE) forms of IDNA valid strings.

Before the current reserved name policy was imposed in 1993, Jon Postel (under the IANA function) took steps to reserve all available single character letters and numbers at the second level for future extensibility of the Internet (see 20 May 1994 email from Jon Postel, All but six (,,,,, and of the possible 144 single letters or numbers at the second-level in .COM, .EDU, .NET and .ORG remain reserved by IANA. Those six registrations are an exception to the reservation practice. Under current practice, these names would be placed on reserve if the registrations were allowed to expire.

The RN-WG carefully considered technical implications of releasing single-letter and single-digit domain names from reservation, and engaged in discussions with technical experts as the working group recommendations were being developed.

There are currently 280 TLDs in the root zone (20 gTLDs, 249 ccTLDs and 11 evaluative translations of .TEST). Although nearly all single-letter and single-digit domain names are reserved in gTLDs, 24% of ccTLDs (60) have at least one single-character name registration. According to IANA, out of 9540 possible combinations of single-character ASCII names (containing 26 letters, 10 numbers, but not symbols, across 265 TLDs), 1225 delegations of single-character ASCII names exist in the TLD zones (See

ICANN has received many inquiries from third parties seeking to register single-letter and single-digit domain names, and has advised these parties that the names are reserved. Through the establishment of the public forum described above, ICANN is following its bottom-up, multi-stakeholder model to develop suitable allocation mechanisms for the release of single-letter and single-digit domain names as recommended by the GNSO working group.

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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."