Suggested Practices for Registration of Internationalized Domain Names (IDN)
RFC 4290

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Network Working Group                                         J. Klensin
Request for Comments: 4290                                 December 2005
Category: Informational

                Suggested Practices for Registration of
                  Internationalized Domain Names (IDN)

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 for more information.

Abstract

   This document explores the issues in the registration of
   internationalized domain names (IDNs).  The basic IDN definition
   allows a very large number of possible characters in domain names,
   and this richness may lead to serious user confusion about similar-
   looking names.  To avoid this confusion, the IDN registration process
   must impose rules that disallow some otherwise-valid name
   combinations.  This document suggests a set of mechanisms that
   registries might use to define and implement such rules for a broad
   range of languages, including adaptation of methods developed for
   Chinese, Japanese, and Korean domain names.

Klensin                      Informational                      [Page 1]
RFC 4290               IDN Registration Practices          December 2005

Table of Contents

   1. Introduction ....................................................3
      1.1. Background .................................................3
      1.2. The Nature and Status of these Recommendations .............4
      1.3. Terminology ................................................5
         1.3.1. Languages and Scripts .................................5
         1.3.2. Characters, Variants, Registrations, and Other
                Issues ................................................6
         1.3.3. Confusion, Fraud, and Cybersquatting ..................9
      1.4. A Review of the JET Guidelines .............................9
         1.4.1. JET Model .............................................9
         1.4.2. Reserved Names and Label Packages ....................10
      1.5. Languages, Scripts, and Variants ..........................11
         1.5.1. Languages versus Scripts .............................11
         1.5.2. Variant Selection ....................................13
      1.6. Variants are not a Universal Remedy .......................14
      1.7. Reservations and Exclusions ...............................14
         1.7.1. Sequence Exclusions for Valid Characters .............14
         1.7.2. Character Pairing Issues .............................15
      1.8. The Registration Bundle ...................................15
         1.8.1. Definitions and Structure ............................15
         1.8.2. Application of the Registration Bundle ...............16
   2. Some Implications of This Approach .............................17
   3. Possible Modifications of the JET Model ........................18
   4. Conclusions and Recommendations About the General Approach .....18
   5. A Model Table Format ...........................................19
   6. A Model Label Registration Procedure: "CreateBundle" ...........20
      6.1. Description of the CreateBundle Mechanism .................21
      6.2. The "no-variants" Case ....................................22
      6.3. CreateBundle and Nameprep Mapping .........................22
   7. IANA Considerations ............................................23
   8. Internationalization Considerations ............................24
   9. Security Considerations ........................................24
   10. Acknowledgements ..............................................25
   11. Informative References ........................................26

Klensin                      Informational                      [Page 2]
RFC 4290               IDN Registration Practices          December 2005

1.  Introduction

1.1.  Background

   The IDNA (Internationalized Domain Names in Applications)
   specification [RFC3490] defines the basic model for encoding non-
   ASCII strings in the DNS.  Additional specifications [RFC3491]
   [RFC3492] define the mechanisms and tables needed to support IDNA.
   As work on these specifications neared completion, it became apparent
   that it would be desirable for registries to impose additional
   restrictions on the names that could actually be registered (e.g.,
   see [IESG-IDN] and [ICANN-IDN]) to reduce potential confusion among