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Independent Report Maps Possible Way Forward in Mitigating Domain Name Collisions

Los Angeles… An independent report commissioned by ICANN has offered a set of concrete recommendations on how to mitigate potential risks of domain name collisions.

A name collision occurs when an attempt to resolve a name used in a private name space results in a query to the public Domain Name System (DNS).

"This report takes an in-depth look at the collision issue and the potential risks and impacts, and gives us some very clear advice aimed at how to help system operators detect and mitigate those risks," said Akram Atallah, President of ICANN's Global Domains Division. "The next step is to seek input from our community on the report's findings."

The report stressed that name collisions are nothing new and that any issues that arise from expansion of the Top-Level Domains (TLDs) under ICANN's New gTLD program would resemble those that occur in other parts of the DNS. But the report noted that expanding the number of TLDs will not fundamentally or significantly increase the risks of name collisions.

Specifically, the study outlines a set of recommendations on how ICANN and the TLD operators should handle the issue of name collisions in the expanding TLD space:

  • ICANN should require new TLD registries to implement and publish a 120-day controlled interruption zone monitored by ICANN immediately upon delegation in the root zone. 
    • After the 120-day period, there shall be no further collision-related restrictions on the TLD.
  • ICANN should have emergency response processes to analyze and act upon reported problems that present "clear and present danger to human life".
  • ICANN and others in the community should continue to collect and analyze data relating to the root servers and to the controlled interruption.
  • The Top-Level Domains .corp, .home and .mail should be permanently reserved.

The report, Mitigating the Risk of DNS Namespace Collisions, is posted for public comment until April 21, 2014.


To review the report and/or make comments, go to:

For more information on name collisions, go to:

For more information about the new gTLD program, go to:


Brad White
ICANN Director of Global Media Affairs
Washington, D.C.
Tel. +1 (202) 570 7118

James Cole
ICANN Global Media Coordinator
Washington, D.C.
Tel. +1 (202) 570 7139

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."