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Comment Concerning Trailing-Hyphen Domain Names

Since the implementation of the Internet domain-name system in the 1980s, the specifications published and implemented by the Internet community have not permitted labels making up domain names to have trailing hyphens (e.g., "example-.com"). Througout this period, the specifications for the format of domain names have been well-known throughout the Internet technical community. They have been set forth in several RFCs, including RFC 1035 (published in 1987) and RFC 1123 (published in 1989). The commonly accepted specifications are reflected in the functional specification for the Shared Registry System, through which competitive registrar services were introduced in the .com/.net/.org top-level domains last year, which requires that labels end with letters or digits, not hyphens.

In the past several weeks, however, over 800 domain names with labels containing trailing hyphens were registered by mistake in the .com/.net/.org registry. These names do not conform to the the functional specification under which the .com/.net/.org registry is operated. The registry software in use before January 3, 2000, however, permitted registrars to enter these malformatted names into the registry, and some registrars' software similarly failed to screen out requests to register these names. Promptly upon learning that these names had been registered, the registry operator (NSI-Registry) revised the software to reject additional requests to register names of this format.

ICANN supports these corrections to maintain the stability of the Internet. At the ICANN annual meeting on November 4, 1999, the ICANN Board approved a package of agreements among NSI, ICANN, the United States Department of Commerce, and the ICANN-accredited registrars. Those agreements require any names that are registered to comply with the format specified in the registry's functional specification. They also provide that those registering domain names must agree to cancellation of the registration in the event of a registry or registrar mistake, and in the case of every one of the trailing-hyphen names the registering party did in fact have such an agreement.

The use of domain names in this noncompliant format presents interoperability problems. The documented format is well-known throughout the Internet technical community. Among other things, domain names that violate this format have the potential of causing software written in reliance on these formats to malfunction, and several instances of actual malfunctions have been identified.

The U.S. Government's Statement of Policy on the Management of Internet Names and Addresses, 63 Fed. Reg. 31741 (June 10, 1998) (commonly known as the "White Paper") specifies that preserving the stability of the Internet should be the first priority of any DNS management system. A second principle that the White Paper states should guide DNS-management activities is the promotion of competition in the provision of registration services.

After consultation among ICANN, NSI-Registry, and the registrars involved, notices have been given to the registering parties that these names were accepted and registered by mistake and will be cancelled. These cancellations reflect implementation of longstanding policy, rather than adoption of any new policy. ICANN commends NSI-Registry and the registrars involved for working constructively within the competitive framework adopted at the March and November 1999 ICANN meetings to effectively and promptly address this challenge to Internet stability. This sort of commitment to stability and competition will continue and expand the many public benefits the Internet has brought.


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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."