National and Local Characters for DNS Top Level Domain (TLD) Names
RFC 4185

Network Working Group                                         J. Klensin
Request for Comments: 4185                                  October 2005
Category: Informational

   National and Local Characters for DNS Top Level Domain (TLD) Names

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2005).

IESG Note

   This RFC is not a candidate for any level of Internet Standard.  The
   IETF disclaims any knowledge of the fitness of this RFC for any
   purpose and notes that the decision to publish is not based on IETF
   review apart from IESG review for conflict with IETF work.  The RFC
   Editor has chosen to publish this document at its discretion.  See
   RFC 3932 [RFC3932] for more information.

Abstract

   In the context of work on internationalizing the Domain Name System
   (DNS), there have been extensive discussions about "multilingual" or
   "internationalized" top level domain names (TLDs), especially for
   countries whose predominant language is not written in a Roman-based
   script.  This document reviews some of the motivations for such
   domains, several suggestions that have been made to provide needed
   functionality, and the constraints that the DNS imposes.  It then
   suggests an alternative, local translation, that may solve a superset
   of the problem while avoiding protocol changes, serious deployment
   delays, and other difficulties.  The suggestion utilizes a
   localization technique in applications to permit any TLD to be
   accessed using the vocabulary and characters of any language.  It is
   not restricted to language- or country-specific "multilingual" TLDs
   in the language(s) and script(s) of that country.

Klensin                      Informational                      [Page 1]
RFC 4185              Characters for DNS TLD Names          October 2005

Table of Contents

   1. Introduction ....................................................3
      1.1. Terminology ................................................3
      1.2. Background on the "Multilingual Name" Problem ..............3
           1.2.1. Approaches to the Requirement .......................3
           1.2.2. Writing the Name of One's Country in its Own
                  Characters ..........................................4
           1.2.3. Countries with Multiple Languages and
                  Countries with Multiple .............................5
           1.2.4. Availability of Non-ASCII Characters in Programs ....5
      1.3. Domain Name System Constraints .............................6
           1.3.1. Administrative Hierarchy ............................6
           1.3.2. Aliases .............................................6
      1.4. Internationalization and Localization ......................7
   2. Client-Side Solutions ...........................................7
      2.1. IDNA and the Client ........................................8
      2.2. Local Translation Tables for TLD Names .....................8
   3. Advantages and Disadvantages of Local Translation ...............9
      3.1. Every TLD Appears in the Local Language and Character Set ..9
      3.2. Unification of Country Code Domains .......................10
      3.3. User Understanding of Local and Global References .........11
      3.4. Limits on Expansion of the Number of TLDs .................11
      3.5. Standardization of the Translations .......................12
      3.6. Implications for Future New Domain Names ..................13
      3.7. Mapping for TLDs, Not Domain Names or Keywords ............13
   4. Information Interchange, IDNs, Comparisons, and Translations ...13
   5. Internationalization Considerations ............................15
   6. Security Considerations ........................................15
   7. Acknowledgements ...............................................16
   8. Informative References .........................................17

Klensin                      Informational                      [Page 2]
RFC 4185              Characters for DNS TLD Names          October 2005

1.  Introduction

1.1.  Terminology

   This document assumes the conventional terminology used to discuss
   the domain name system (DNS) and its hierarchical arrangements.
   Terms such as "top level domain" (or just "TLD"), "subdomain",
   "subtree", and "zone file" are used without further explanation.  In
   addition, the term "ccTLD" is used to denote a "country code top