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INTERNET DRAFT                                     Editors:  James SENG
draft-jseng-idn-admin-03.txt              John C KLENSIN, Wendy RICKARD
16 June 2003                                       Authors:  K. KONISHI
Expires December 2003                          K. HUANG, H. QIAN, Y. KO

    Internationalized Domain Names Registration and Administration
              Guideline for Chinese, Japanese, and Korean

Status of This Memo

This document is an Internet Draft and is in full conformance
with all provisions of Section 10 of RFC2026 except that the
right to produce derivative works is not granted.

    Internet Drafts are working documents of the Internet
    Engineering Task Force (IETF), its areas, and its working
    groups. Note that other groups may also distribute working
    documents as Internet Drafts.

    Internet Drafts are draft documents valid for a maximum of
    six months and may be updated, replaced, or rendered obsolete by
    other documents at any time. It is inappropriate to use Internet
    Drafts as reference material or to cite them other than as
    "works in progress."

    The list of current Internet Drafts can be accessed at
    http://www.ietf.org/ietf/1id-abstracts.txt.

    The list of Internet Draft Shadow Directories can be accessed at
    http://www.ietf.org/shadow.html.

Abstract

Achieving internationalized access to domain names raises many complex
issues.  These are associated not only with basic protocol design--such
as how names are represented on the network, compared, and converted to
appropriate forms--but also with issues and options for deployment,
transition, registration, and administration.

The IETF Internationalized Domain Name (IDN) Working Group focused its
efforts on the development of a standards-track specification for access
to domain names in a range of scripts that is broader in scope than the
original ASCII.  During its efforts, it became clear that the appearance
of characters with similar appearances and/or interpretations created
potential for confusion, as well as difficulties in deployment and
transition, and that those issues could best be addressed
administratively rather than through restrictions embedded in the
protocols.

This document is an effort of the Joint Engineering Team (JET), a group
composed of members of CNNIC, TWNIC, KRNIC, and JPNIC as well as other
individual experts.  It offers guidelines for zone administrators --
including but not limited to registry operators and registrars -- and
information for all domain names holders on the administration of domain
names that contain characters drawn from Chinese, Japanese, and Korean
scripts.  Other language groups are encouraged to develop their own
guidelines as needed, based on these guidelines if that is helpful.

Table of Contents

1. Introduction

2.  Definitions, Context, and Notation
2.1. Definitions and Context
2.2. Notation for Ideographs and Other Non-ASCII CJK Characters

3.  Scope of the Administrative Guidelines
3.1. Principles Underlying These Guidelines
3.2. Registration of IDL
3.2.1. Using the Language Variant Table
3.2.2. IDL Package
3.2.3.  Procedure for Registering IDLs
3.3. Deletion and Transfer of IDL and IDL Package
3.4. Activation and Deactivation of IDL Variants
3.4.1. Activation Algorithm
3.4.2. Deactivation Algorithm
3.5. Managing Changes in Language Associations
3.6. Managing Changes to Language Variant Tables

4. Examples of Guideline Use in Zones

5. Syntax Description for the Language Variant Table
5.1 ABNF Syntax
5.2. Comments and Explanation of Syntax

6. Security Considerations

7. Index to Terminology

8. Acknowledgments

9. Authors’ Addresses

10. Normative References

11. Nonnormative References

1. Introduction

Domain names form the fundamental naming architecture of the Internet.
Countless Internet protocols and applications rely on them, not just for
stability and continuity, but also to avoid ambiguity.  They were
designed to be identifiers without any language context.  However, as
domain names have become visible to end users through Web URLs and
e-mail addresses, the strings in domain-name labels are being
increasingly interpreted as names, words, or phrases.  It is likely that
users will do the same with languages of differing character sets--such
as Chinese, Japanese and Korean (CJK)--in which many words or concepts
are represented using short sequences of characters.

The introduction of what are called Internationalized Domain Names (IDN)
amplifies both the difficulty of putting names into identifiers and the
confusion that exists between scripts and languages.  It also affects a
number of Internet protocols and applications and creates additional
layers of complexity in terms of technical administration and services.
Given the added complications of using a much broader range of
characters than the original small ASCII subset, precautions are
necessary in the deployment of IDNs in order to minimize confusion and
fraud.

The IETF IDN Working Group [IDN-WG] addressed the problem of handling
the encoding and decoding of Unicode strings into and out of Domain Name
System (DNS) labels with the goal that its solution would not put the
operational DNS at any risk.  Its work resulted in one primary protocol
and three supporting ones, respectively:

1. Internationalizing Host Names in Applications [IDNA]
2. Preparation of Internationalized Strings [STRINGPREP]
3. A Stringprep Profile for Internationalized Domain Names [NAMEPREP]
4. Punycode [PUNYCODE]

IDNA--which calls on the others--normalizes and transforms strings that
are intended to be used as IDNs.  In combination, the four provide the
minimum functions required for internationalization, such as performing
case mappings, eliminating character differences that would cause severe
problems, and specifying matching (equality).  They also convert between
the resulting Unicode code points and an ASCII-based form that is more
suitable for storing in actual DNS labels.  In this way, the IDNA
transformations improve a user’s chances of getting to the correct IDN.

Addressing the issues around differing character sets, a primary
consideration and administrative challenge involves region-specific
definitions, interpretations, and the semantics of strings to be used in
IDNs.  A Unicode string may have a specific meaning as a name, word, or
phrase in a particular language but that meaning could vary depending on
the country, region, culture, or other context in which the string is
used.  It might also have different interpretations in different
languages that share some or all of the same characters.  Therefore,
individual zones and zone administrators may find it necessary to impose
restrictions and procedures to reduce the likelihood of confusion--and
instabilities of reference--within their own environments.

Over the centuries, the evolution of CJK characters--and the differences
in their use in different languages and even in different regions where
the same language is spoken--has given rise to the idea of "variants",
wherein one conceptual character can be identified with several
different Code Points in character sets for computer use.  This document
provides a framework for handling such variants while minimizing the
possibility of serious user confusion in the obtaining or use of domain
names.  However, the concept of variants is complex and may require many
different layers of solution, this guideline offers only one of the
solution components.  It is not sufficient by itself to solve the whole
problem, even with zone-specific tables as described below.

Additionally, because of local language or writing-system differences,
it is impossible to create universally accepted definitions for which
potential variants are the same and which are not the same.  It is even
more difficult to define a technical algorithm to generate variants that
are linguistically accurate--that is, that the variant forms produced
make as much sense in the language as the originally specified forms.
It is also possible that variants generated may have no meaning in the
associated language or languages.  The intention is not to generate
meaningful "words" but to generate similar variants to be reserved.  So
even though the method described in this document may not always be
linguistically accurate--or need to be--it increases the chances of
getting the right variants while accepting the inherent limitations of
the DNS and the complexities of human language.

This document outlines a model for such conventions for zones in which
labels that contain CJK characters are to be registered and a system for
implementing that model.  It provides a mechanism that allows each zone
to define its own local rules for permitted characters and sequences and
the handling of IDNs and their variants.

2. Definitions, Context, and Notation

2.1. Definitions and Context

This document uses a number of special terms.  In this section,
definitions and explanations are grouped topically.  Some readers may
prefer to skip over this material, returning, perhaps via the index to
terminology in section 7, when needed.

2.1.1.  IDN: The term "IDN" has a number of different uses: (a) as an
abbreviation for "Internationalized Domain Name"; (b) as a fully
qualified domain name that contains at least one label that contains
characters not appearing in ASCII, specifically not in the subset of
ASCII recommended for domain names (the so-called "hostname" or "LDH"
subset, see RFC1035 [STD13]); (c) as a label of a domain name that
contains at least one character beyond ASCII; (d) as a Unicode string to
be processed by Nameprep; (e) as a string that is an output from
Nameprep; (f) as a string that is the result of processing through both
Nameprep and conversion into Punycode; (g) as the abbreviation of an IDN
(more properly, IDL) Package, in the terminology of this document; (h)
as the abbreviation of the IETF IDN Working Group; (g) as the
abbreviation of the ICANN IDN Committee; and (h) as standing for other
IDN activities in other companies/organizations.

Because of the potential confusion, this document uses the term "IDN" as
an abbreviation for Internationalized Domain Name and, specifically, in
the second sense described in (b) above.  It uses "IDL," defined
immediately below, to refer to Internationalized Domain Labels.

2.1.2.  IDL: This document provides a guideline to be applied on a
per-zone basis, one label at a time.  Therefore, the term
"Internationalized Domain Label" or "IDL" will be used instead of the
more general term "IDN" or its equivalents.  The processing
specifications of this document may be applied, in some zones, to ASCII
characters also, if those characters are specified as valid in a
Language Variant Table (see below).  Hence, in some zones, an IDL may
contain or consist entirely of "LDH" characters.

2.1.3.  FQDN: A fully qualified domain name, one that explicitly
contains all labels, including a Top-Level Domain (TLD) name.  In this
context, a TLD name is one whose label appears in a nameserver record in
the root zone.  The term "Domain Name Label" refers to any label of a
FQDN.

2.1.4.  Registration: In this document, the term "registration" refers
to the process by which a potential domain name holder requests that a
label be placed in the DNS either as an individual name within a domain
or as a subdomain delegation from another domain name holder.  In the
case of a successful registration, the label or delegation records are
placed in the relevant zone file, or, more specifically, they are
"activated" or made "active" and additional IDLs may be reserved as part
of an "IDL Package" (see below).  The guidelines presented here are
recommended for all zones--at any hierarchy level--in which CJK
characters are to appear and not just domains at the first or second
level.

2.1.5.  RFC3066: A system, widely used in the Internet, for coding and
representing names of languages.  It is based on an International
Organization for Standardization (ISO) standard for coding language
names [ISO639], but expands it to provide additional precision.

2.1.6.  ISO/IEC 10646: The international standard universal
multiple-octet coded character set ("UCS") [IS10646].  The Code Point
definitions of this standard are identical to those of corresponding
versions of the Unicode standard (see below).  Consequently, the
characters and their coding are often referred to as "Unicode
characters."

2.1.7.  Unicode Character: The term "Unicode character" is used here in
reference to characters chosen from the Unicode Standard Version 3.2
[UNICODE] (and hence from ISO/IEC 10646).  In this document, the
characters are identified by their positions, or "Code Points." The
notation U+12AB, for example, indicates the character at the position
12AB (hexadecimal) in the Unicode 3.2 table.  For characters in
positions above FFFF—i.e., requiring more than sixteen bits to
represent--a five to eight-character string is used, such as U+112AB for
the character in position 12AB of plane 1.

2.1.8.  Unicode String: "Unicode string" refers to a string of Unicode
characters.  The Unicode string is identified by the sequence of the
Unicode characters regardless of the encoding scheme.

2.1.9.  CJK Characters: CJK characters are characters commonly used in
the Chinese, Japanese, or Korean languages, including but not limited to
those defined in the Unicode Standard as ASCII (U+0020 to U+007F), Han
ideographs (U+3400 to U+9FAF and U+20000 to U+2A6DF), Bopomofo (U+3100
to U+312F and U+31A0 to U+31BF), Kana (U+3040 to U+30FF), Jamo (U+1100
to 11FF and U+3130 to U+318F), Hangul (U+AC00 to U+D7AF and U+3130 to
U+318F), and the respective compatibility forms.  The particular
characters that are permitted in a given zone are specified in the
Language Variant Table(s) for that zone.

2.1.10.  Label String: A generic term referring to a string of
characters that is a candidate for registration in the DNS or such a
string, once registered.   A label string may or may not be valid
according to the rules of this specification and may even be invalid for
IDNA use.  The term "label", by itself, refers to a string that has been
validated and may be formatted to appear in a DNS zone file.

2.1.11.  Language Variant Table: The key mechanisms of this
specification utilize a three-column table, called a Language Variant
Table, for each language permitted to be registered in the zone.  Those
columns are known, respectively, as "Valid Code Point", "Preferred
Variant", and "Character Variant", which are defined separately below.
The Language Variant Tables are critical to the success of the guideline
described in this document.  However, the principles to be used to
generate the tables are not within the scope of this document and should
be worked out by each registry separately (perhaps by adopting or
adapting the work of some other registry).  In this document, "Table"
and "Variant Table" are used as short forms for Language Variant Table.

2.1.12.  Valid Code Point: In a Language Variant Table, the list of Code
Points that is permitted for that language.  Any other Code Points, or
any string containing them, will be rejected by this specification.  The
Valid Code Point list appears as the first column of the Language
Variant Table.

2.1.13.  Preferred Variant: In a Language Variant Table, a list of Code
Points corresponding to each Valid Code Point and providing possible
substitutions for it.  These substitutions are "preferred" in the sense
that the variant labels generated using them are normally registered in
the zone file, or "activated." The Preferred Code Points appear in
column 2 of the Language Variant Table.  "Preferred Code Point" is used
interchangeably with this term.

2.1.14.  Character Variant: In a Language Variant Table, a second list
of Code Points corresponding to each Valid Code Point and providing
possible substitutions for it.  Unlike the Preferred Variants,
substitutions based on Character Variants are normally reserved but not
actually registered (or "activated").  Character Variants appear in
column 3 of the Language Variant Table.  The term "Code Point Variants"
is used interchangeably with this term.

2.1.15.  Preferred Variant Label: A label generated by use of Preferred
Variants (or Preferred Code Points).

2.1.16.  Character Variant Label: A label generated by use of Character
Variants.

2.1.17.  Zone Variant: A Preferred or Character Variant Label that is
actually to be entered (registered) into the DNS--that is, into the zone
file for the relevant zone.  Zone Variants are also referred to as Zone
Variant Labels or Active (or Activated) Labels.

2.1.18.  IDL Package: A collection of IDLs as determined by these
Guidelines.   All labels in the package are "reserved", meaning they
cannot be registered by anyone other than the holder of the Package.
These reserved IDLs may be "activated", meaning they are actually
entered into a zone file as a "Zone Variant".   The IDL Package also
contains identification of the language(s) associated with the
registration process.   The IDL and its variant labels form a single,
atomic unit.

2.2 Notation for Ideographs and Other Non-ASCII CJK Characters.

For purposes of clarity, particularly in regard to examples, Han
ideographs appear in several places in this document.  However, they do
not appear in the ASCII version of this document.  For the convenience
of readers of the ASCII version--and some readers not familiar with
recognizing and distinguishing Chinese characters--most uses of these
characters will be associated with both their Unicode Code Points and an
"asterisk tag" with its corresponding Chinese Romanization [ISO7098],
with the tone mark represented by a number from 1 to 4.  Those tags have
no meaning outside this document; they are a quick visual and reading
reference to help facilitate the combinations and transformations of
characters in the guideline and table excerpts.

3. Scope of the Administrative Guidelines

Zone administrators are responsible for the administration of the domain
name labels under their control.  A zone administrator might be
responsible for a large zone, such as a top-level domain (TLD)--whether
generic or country code--or a smaller one, such as a typical second- or
third-level domain.  A large zone is often more complex than its smaller
counterpart.  However, actual technical administrative tasks--such as
addition, deletion, delegation, and transfer of zones between domain
name holders--are similar for all zones.

This document provides guidelines for the ways CJK characters should be
handled within a zone, for how language issues should be considered and
incorporated, and for how Domain Name Labels containing CJK characters
should be administered (including registration, deletion, and transfer
of labels).  It does not provide any guidance for the handling of
non-CKJ characters or languages in zones.

Other IDN policies--such as the creation of new top-level domains
(TLDs), the cost structure for registrations, and how the processes
described here get allocated between registrar and registry if the zone
makes that distinction--also are outside the scope of this document.

Technical implementation issues are not discussed here either.  For
example, deciding which guidelines should be implemented as registry
actions and which should be registrar actions is left to zone
administrators, with the possibility that it will differ from zone to
zone.

3.1. Principles Underlying These Guidelines

In many places, in the event of a dispute over rights to a name (or,
more accurately, DNS label string), this document assumes "first-come,
first-served" (FCFS) as a resolution policy even though FCFS is not
listed below as one of the principles for this document.  If policies
are already in place governing priorities and "rights", one can use the
guidelines here by replacing uses of FCFS in this document with policies
specific to the zone.  Some of the guidelines here may not be applicable
to other policies for determining rights to labels.  Still other
alternatives--such as use of UDRP [WIPO-UDRP] or mutual exclusion--might
have little impact on other aspects of these guidelines.

(a) Although some Unicode strings may be pure identifiers made up of an
assortment of characters from many languages and scripts, IDLs are
likely to be "words" or "names" or "phrases" that have specific meaning
in a language.  While a zone administration might or might not require
"meaning" as a registration criterion, meaning could prove to be a
useful tool for avoiding user confusion.

    Each IDL to be registered should be associated administratively
    with one or more languages.

Language associations should either be predetermined by the zone
administrator and applied to the entire zone or be chosen by the
registrants on a per-IDL basis.  The latter may be necessary for some
zones, but it will make administration more difficult and will increase
the likelihood of conflicts in variant forms.

    A given zone might have multiple languages associated with it or
    it may have no language specified at all.  Omitting specification
    of a language may provide additional opportunities for user
    confusion and is therefore NOT recommended.

(b) Each language uses only a subset of Unicode characters.  Therefore,
if an IDL is associated with a language, it is not permitted to contain
any Unicode character that is not within the valid subset for that
language.

    Each IDL to be registered must be verified against the valid subset
 of Unicode for the language(s) associated with the IDL.  That subset
 is specified by the list of characters appearing in the first column
    of the language and zone-specific tables as described later in this
    document.

If the IDL fails this test for any of its associated languages, the IDL
is not valid for registration.

Note that this verification is not necessarily linguistically accurate,
because some languages have special rules.  For example, some languages
impose restrictions on the order in which particular combinations of
characters may appear.  Characters that are valid for the language--and
hence permitted by this specification--might still not form valid words
or even strings in the language.

(c) When an IDL is associated with a language, it may have Character
Variants that depend on that language associated with it in addition to
any Preferred Variants.  These variants are potential sources of
confusion with the Code Points in the original label string.
Consequently, the labels generated from them should be unavailable to
registrants of other names, words, or phrases.

    During registration, all labels generated from the Character
    Variants for the associated language(s) of the IDL should be
    reserved.

IDL reservations of the type described here normally do not appear in
the distributed DNS zone file.  In other words, these reserved IDLs may
not resolve.  Domain name holders could request that these reserved IDLs
be placed in the zone file and made active and resolvable.

Zones will need to establish local policies about how they are to be
made active.  Specifically, many zones, especially at the top level,
have prohibited or restricted the use of "CNAME"s--DNS
aliases--especially CNAMEs that point to nameserver delegation records
(NS records).  And long-term use of long-term aliases for domain
hierarchies, rather than single names ("DNAME records") are considered
problematic because of the recursion they can introduce into DNS
lookups.

(d) When an IDL is a "name", "word", or "phrase", it will have Character
Variants depending on the associated language.  Furthermore, one or more
of those Character Variants will be used more often than others for
linguistic, political, or other reasons.  These more commonly used
variants are distinguished from ordinary Character Variants and are
known as Preferred Variant(s) for the particular language.

    To increase the likelihood of correct and predictable resolution of
    the IDN by end users, all labels generated from the Preferred
    Variants for the associated language(s) should be resolvable.

In other words, the Preferred Variant Labels should appear in the
distributed DNS zone file.

(e) IDLs associated with one or more languages may have a large number
of Character Variant Labels or Preferred Variant Labels.  Some of these
labels may include combinations of characters that are meaningless or
invalid linguistically.   It may therefore be appropriate for a zone to
adopt procedures that include only linguistically-acceptable labels in
the IDL Package.

    A zone administrator may impose additional rules and other
    processing activities to limit the number of Character Variant
    Labels or Preferred Variant Labels that are actually reserved or
    registered.

These additional rules and other processing activities are based on
policies and/or procedures imposed on a per-zone basis and therefore are
not within the scope of this document.  Such policies or procedures
might be used, for example, to restrict the number of Preferred Variant
Labels actually reserved or to prevent certain words from being
registered at all.

(f) There are some Character Variant Labels and Preferred Variant Labels
that are associated with each IDL.  These labels are considered
"equivalent" to each another.  To avoid confusion, they all should be
assigned to a single domain name holder.

    The IDL and its variant labels should be grouped together into a
    single atomic unit, known in this document as an "IDL Package".

The IDL Package is created upon registration and is atomic: Transfer and
deletion of an IDL is performed on the IDL Package as a whole.  That is,
an IDL within the IDL Package may not be transferred or deleted
individually; any re-registration, transfers, or other actions that
impact the IDL should also affect the other variants.

The name-conflict resolution policy associated with this zone could
result in a conflict with the principle of IDL Package atomicity.  In
such a case, the policy must be defined to make the precedence clear.

3.2. Registration of IDL

To conform to the principles described in 3.1, this document introduces
two concepts: the Language Variant Table and the IDL Package.  These are
described in the next two subsections, followed by a description of the
algorithm that is used to interpret the table and generate variant
labels.

3.2.1. Using the Language Variant Table

For each zone that uses a given language, each language should have its
own Language Variant Table.  The table consists of a header section that
identifies references and version information, followed by a section
with one row for each Code Point that is valid for the language and
three columns..

a) The first column contains the subset of Unicode characters that is
valid to be registered ("Valid Code Point").  This is used to verify the
IDL to be registered (see 3.1b).  As in the registration procedure
described later, this column is used as an index to examine characters
that appear in a proposed IDL to be processed.  The collection of Valid
Code Points in the table for a particular language can be thought of as
defining the script for that language, although the normal definition of
a script would not include, for example, ASCII characters with CJK ones.

b) The second column contains the Preferred Variant(s) of the
corresponding Unicode character in column one ("Valid Code Point").
These variant characters are used to generate the Preferred Variant
Labels for the IDL.  Those labels should be resolvable (see 3.1d).
Under normal circumstances, all of those Preferred Variant Labels will
be activated in the relevant zone file so that they will resolve when
the DNS is queried for them.

c) The third column contains the Character Variant(s) for the
corresponding Valid Code Point.  These are used to generate the
Character Variant Labels of the IDL, which are then to be reserved (see
3.1c).  Registration--or activation--of labels generated from Character
Variants will normally be a registrant decision, subject to local
policy.

Each entry in a column consists of one or more Code Points, expressed as
a numeric character number in the Unicode table and optionally followed
by a parenthetical reference.  The first column--or Valid Code Point--
may have only one Code Point specified in a given row.  The other
columns may have more than one.

Any row may be terminated with an optional comment, starting in "#".

The formal syntax of the table and more-precise definitions of some of
its organization appear in Section 5.

The Language Variant Table should be provided by a relevant group,
organization, or body.  However, the question of who is relevant or has
the authority to create this table and the rules that define it is
beyond the scope of this document.

3.2.2. IDL Package

The IDL Package is created on successful registration and consists of:

a) the IDL registered

b) the language(s) associated with the IDL

c) the reserved IDLs

d) active IDLs--that is, "Zone Variant Labels" that are to appear in
   the DNS zone file

3.2.3. Procedure for Registering IDLs

An explanation follows each step.

Step 1. IN <= IDL to be registered and
        {L} <= Set of languages associated with IN

Start the process with the label string (prospective IDL) to be
registered and the associated language(s) as input.

Step 2. Generate the Nameprep-processed version of the IN, applying
        all mappings and canonicalization required by IDNA.

The prospective IDL is processed by using Nameprep to apply the
normalizations and exclusions globally required to use IDNA.  If the
Nameprep processing fails, then the IDL is invalid and the registration
process must stop.

Step 2.1. NP(IN) <= Nameprep processed IN
Step 2.2. Check availability of NP(IN).
          If not available, route to conflict policy.

The Nameprep-processed IDL is then checked against the contents of the
zone file and previously created IDL Packages.  If it is already
registered or reserved, then a conflict exists that must be resolved by
applying whatever policy is applicable for the zone.  For example, if
FCFS is used, the registration process terminates unless the conflict
resolution policy provides another alternative.

Step 3. Process each language.
        For each language (AL} in {L}

Step 3 goes through all languages associated with the proposed IDL and
checks each character (after Nameprep has been applied) for validity in
each of them.  It then applies the Preferred Variants (column 2 values)
and the Character Variants (column 3 values) to generate candidate
labels.

Step 3.1. Check validity of NP(IN) in AL. If failed, stop processing.

In step 3.1, IDL validation is done by checking that every Code Point in
the Nameprep-processed IDL is a Code Point allowed by the "Valid Code
Point" column of the Character Variant Table for the language.  This is
then repeated for any other languages (and hence, Language Variant
Tables) specified in the registration.  If one or more Code Points are
not valid, the registration process terminates.

Step 3.2.  PV(IN,AL) <= Set of available Nameprep-processed Preferred
                        Variants of NP(IN) in AL

Step 3.2 generates the list of Preferred Variant Labels of the IDL by
doing a combination (see Step 3.2A below) of all possible variants
listed in the "Preferred Variant(s)" column for each Code Point in the
Nameprep-processed IDL.  The generated Preferred Variant Labels must be
processed through Nameprep.  If the Nameprep processing fails for any
Preferred Variant Label (this is unlikely to occur if the Preferred
Variants [Code Points] are processed through Nameprep before being
placed in the table), then that variant label will be removed from the
list.  The remaining Preferred Variant Labels in the list are then
checked to see whether they are already registered or reserved.  If any
are registered or reserved, then the conflict resolution policy will
apply.  In general, this will not prevent the originally requested IDL
from being registered unless the policy prevents such registration.  For
example, if FCFS is applied, then the conflicting variants will be
removed from the list, but the originally requested IDL and any
remaining variants will be registered (see steps 5 and 8 below).

Step 3.2A Generating variant labels from Variant Code Points.

Steps 3.2 and 3.3 require that the Preferred Variants and Character
Variants be combined with the original IDL to form sets of variant
labels.  Conceptually, one starts with the original, Nameprep-processed,
IDL and examines each of its characters in turn.  If a character is
encountered for which there is a corresponding Preferred Variant or
Character Variant, a new variant label is produced with the Variant Code
Point substituted for the original one.  If variant labels already exist
as the result of the processing of characters that appeared earlier in
the original IDL, then the substitutions are made in them as well,
resulting in additional generated variant labels.  This operation is
repeated separately for the Preferred Variants (in Step 3.2) and
Character Variants (in Step 3.3).  Of course, equivalent results could
be achieved by processing the original IDL’s characters in order,
building the Preferred Variant Label set and Character Variant Label set
in parallel.

This process will sometimes generate a very large number of labels.  For
example, if only two of the characters in the original IDL are
associated with Preferred Variants and if the first of those characters
has three Preferred Variants and the second has two, one ends up with 12
variant labels to be placed in the IDL Package and, normally, in the
zone file.  Repeating the process for Character Variants, if any exist,
would further increase the number of labels.  And if more than one
language is specified for the original IDL, then repetition of the
process for additional languages (see step 4, below) might further
increase the size of the set.

For illustrative purposes, the "combination" process could be achieved
by a recursive function similar to the following pseudocode:

Function Combination(Str)
  F <= first codepoint of Str
  SStr <= Substring of Str, without the first code point
  NSC <= {}

  If SStr is empty then
    For each V in (Variants of code point F)
      NSC = NSC set-union (the string with the code point V)
    End of Loop
  Else
    SubCom = Combination(SStr)
    For each V in (Variants of code point F)
      For each SC in SubCom
        NSC = NSC set-union (the string with the first code point V
              followed by the string SC)
      End of Loop
    End of Loop
  Endif

  Return NSC

Step 3.3.  CV(IN,AL) <= Set of available Nameprep-processed Character
                        Variants of NP(IN) in AL

This step generates the list of Character Variant Labels by doing a
combination (see Step 3.2A above) of all the possible variants listed in
the "Character Variant(s)" column for each Code Point in the
Nameprep-processed original IDL.  As with the Preferred Variant Labels,
the generated Character Variant Labels must be processed by, and
acceptable to, Nameprep.  If the Nameprep processing fails for a
Character Variant Label, then that variant label will be removed from
the list.  The remaining Character Variant Labels are then checked to be
sure they are not registered or reserved.  If one or more are, then the
conflict resolution policy is applied.  As with Preferred Variant
Labels, a conflict that is resolved in favor of the earlier registrant
does not, in general, prevent the IDL from being registered, nor the
remaining variants from being reserved in step 6 below.

Step 3.4.    End of Loop

Step 4. Let PVall be the set-union of all PV(IN,AL)

Step 4 generates the Preferred Variants Label for all languages.
In this step, and again in step 6 below, the zone administrator may
impose additional rules and processing activities to restrict the number
of Preferred (tentatively to be reserved and activated) and Character
(tentatively to be reserved) Label Variants.  These additional rules and
processing activities are zone policy specific and therefore are not
specified in this document.

Step 5. {ZV} <= PVall set-union NP(IN)

Step 5 generates the initial Zone Variants.  The set includes all
Preferred Variants for all languages and the original Nameprep-processed
IDL.  Unless excluded by further processing, these Zone Variants will be
activated--that is, placed into the DNS zone.  Note that the "set-union"
operation will eliminate any duplicates.

Step 6. Let CVall be the set-union of all CV(IN,AL), set-minus {ZV}

Step 6 generates the Reserved Label Variants (the Character Variant
Label set).  These labels are normally reserved but not activated.  The
set includes all Character Variant Labels for all languages, but not the
Zone Variants defined in the previous step.  The set-union and set-minus
operations eliminate any duplicates.

Step 7. Create IDL Package for IN using IN, {L}, {ZV} and CVall

In Step 7, the "IDL Package" is created using the original IDL, the
associated language(s), the Zone Variant Labels, and the Reserved
Variant Labels.  If zone-specific additional processing or filtering is
to be applied to eliminate linguistically inappropriate or other forms,
it should be applied before the IDL Package is actually assembled.

Step 8. Put {ZV} into zone file

The activated IDLs are converted via ToASCII with UseSTD13ASCIIRules
[IDNA] before being placed into the zone file.  This conversion results
in the IDLs being in the actual IDNA ("Punycode") form used in zone
files, while the IDLs have been carried in Unicode form up to this
point.  If ToASCII fails for any of the activated IDLs, that IDL must
not be placed into the zone file.  If the IDL is a subdomain name, it
will be delegated.

3.3. Deletion and Transfer of IDL and IDL Package

In traditional domain administration, every Domain Name Label is
independent of all other Domain Name Labels.  Registration, deletion,
and transfer of labels is done on a per-label basis.  However, with the
guidelines discussed here, each IDL is associated with specific
languages, with all label variants--both active (zone) and reserved--
together in an IDL Package.  This quite deliberately prohibits labels
that contain sufficient mixtures of characters from different scripts
to make them impossible as words in any given language.  If a zone
chooses to not impose that restriction--that is, to permit labels to
be constructed by picking characters from several different languages
and scripts--then the guidelines described here would be inappropriate.

As stated earlier, the IDL package should be treated as a single atomic
unit and all variants of the IDL should belong to a single domain-name
holder.  If the local policy related to the handling of disagreements
requires a particular IDL to be transferred and deleted independently of
the IDL Package, the conflict policy would take precedence.  In such an
event, the conflict policy should include a transfer or delete procedure
that takes the nature of IDL Packages into consideration.

When an IDL Package is deleted, all of the Zone and Reserved Label
Variants again become available.  The deletion of one IDL Package does
not change any other IDL Packages.

3.4. Activation and Deactivation of IDL variants

Because there are active (registered) IDLs and inactive (reserved but
not registered) IDLs within an IDL package, processes are required to
activate or deactivate IDL variants within an IDL Package.

3.4.1. Activation Algorithm

Step 1. IN <= IDL to be activated and PA <= IDL Package

Start with the IDL to be activated and the IDL Package of which it is a
member.

Step 2. NP(IN) <= Nameprep processed IN

Process the IDL through Nameprep.  This step should never cause a
problem, or even a change, since all labels that become part of the IDL
Package are processed through Nameprep in Step 3.2 or 3.3 of the
Registration procedure (section 3.2.3).

Step 3. If NP(IN) not in {RV} then stop

Verify that the Nameprep-processed version of the IDL appears as a
still-unactivated label in the IDL Package, i.e., in the list of
Reserved Label Variants, {RV}.  It might be a useful "sanity check" to
also verify that it does not already appear in the zone file.

Step 4. {RV} <= {RV} set-minus NP(IN) and {ZV} <= {ZV} set-union NP(IN)

Within the IDL Package, remove the Nameprep-processed version of the IDL
from the list of Reserved Label Variants and add it to the list of
active (zone) label variants.

Step 5. Put {ZV} into the zone file

Actually register (activate) the Zone Variant Labels.


3.4.2. Deactivation Algorithm

Step 1. IN <= IDL to be deactivated and PA <= IDL Package

As with activation, start with the IDL to be deactivated and the IDL
Package of which it is a member.

Step 2. NP(IN) <= Nameprep processed IN

Get the Nameprep-processed version of the name (see discussion in the
previous section).

Step 3. If NP(IN) not in {ZV} then stop

Verify that the Nameprep-processed version of the IDL appears as an
activated (zone) label variant in the IDL Package.  It might be a useful
"sanity check" at this point to also verify that it actually appears in
the zone file.

Step 4. {RV} <= {RV} set-union NP(IN) and {ZV} <= {ZV} set-minus NP(IN)

Within the IDL Package, remove the Nameprep-processed version of the IDL
from the list of Active (Zone) Label Variants and add it to the list of
Reserved (but inactive) Label Variants.

Step 5. Put {ZV} into the zone file

3.5. Managing Changes in Language Associations

Since the IDL package is an atomic unit and the associated list of
variants must not be changed after creation, this document does not
include a mechanism for adding and deleting language associations within
the IDL package.  Instead, it recommends deleting the IDL package
entirely, followed by a registration with the new set of languages.
Zone administrators may find it desirable to devise procedures that
prevent other parties from capturing the labels in the IDL Package
during these operations.

3.6. Managing Changes to the Language Variant Tables

Language Variant Tables are subject to changes over time, and these
changes may or may not be backward compatible.  It is possible that
updated Language Variant Tables may produce a different set of Preferred
Variants and Reserved Variants.

In order to preserve the atomicity of the IDL Package, when the Language
Variant Table is changed, IDL Packages created using the previous
version of the Language Variant Table must not be updated or affected.

4. Examples of Guideline Use in Zones

To provide a meaningful example, some Language Variant Tables must be
defined.  Assume, then, for the purpose of giving examples, that the
following four Language Variant Tables are defined:

Note: these tables are not a representation of the actual tables, and
they do not contain sufficient entries to be used in any actual
implementation.

a) Language Variant Table for zh-cn and zh-sg

Reference 1 CP936 (commonly known as GBK)
Reference 2 zVariant, zTradVariant, zSimpVariant in Unihan.txt
Reference 3 List of Simplified character Table (Simplified column)
Reference 4 zSimpVariant in Unihan.txt
Reference 5 variant that exists in GB2312, common simplified hanzi

Version 1 20020701 # July 2002

56E2(1);56E2(5);5718(2)            # sphere, ball, circle; mass, lump
5718(1);56E2(4);56E2(2),56E3(2)    # sphere, ball, circle; mass, lump
60F3(1);60F3(5);                   # think, speculate, plan, consider
654E(1);6559(5);6559(2)            # teach
6559(1);6559(5);654E(2)            # teach, class
6DF8(1);6E05(5);6E05(2)            # clear
6E05(1);6E05(5);6DF8(2)            # clear, pure, clean; peaceful
771E(1);771F(5);771F(2)            # real, actual, true, genuine
771F(1);771F(5);771E(2)            # real, actual, true, genuine
8054(1);8054(3);806F(2)            # connect, join; associate, ally
806F(1);8054(3);8054(2),8068(2)    # connect, join; associate, ally
96C6(1);96C6(5);                   # assemble, collect together


b) Language Variant Table for zh-tw

Reference 1 CP950 (commonly known as BIG5)
Reference 2 zVariant, zTradVariant, zSimpVariant in Unihan.txt
Reference 3 List of Simplified Character Table (Traditional column)
Reference 4 zTradVariant in Unihan.txt

Version 1 20020701 # July 2002

5718(1);5718(4);56E2(2),56E3(2)    # sphere, ball, circle; mass, lump
60F3(1);60F3(1);                   # think, speculate, plan, consider
6559(1);6559(1);654E(2)            # teach, class
6E05(1);6E05(1);6DF8(2)            # clear, pure, clean; peaceful
771F(1);771F(1);771E(2)            # real, actual, true, genuine
806F(1);806F(3);8054(2),8068(2)    # connect, join; associate, ally
96C6(1);96C6(1);                   # assemble, collect together

c) Language Variant Table for ja

Reference 1 CP932 (commonly known as Shift-JIS)
Reference 2 zVariant in Unihan.txt
Reference 3 variant that exists in JIS X0208, commonly used Kanji

Version 1 20020701 # July 2002

5718(1);5718(3);56E3(2)            # sphere, ball, circle; mass, lump
60F3(1);60F3(3);                   # think, speculate, plan, consider
654E(1);6559(3);6559(2)            # teach
6559(1);6559(3);654E(2)            # teach, class
6DF8(1);6E05(3);6E05(2)            # clear
6E05(1);6E05(3);6DF8(2)            # clear, pure, clean; peaceful
771E(1);771E(1);771F(2)            # real, actual, true, genuine
771F(1);771F(1);771E(2)            # real, actual, true, genuine
806F(1);806F(1);8068(2)            # connect, join; associate, ally
96C6(1);96C6(3);                   # assemble, collect together

d) Language Variant Table for ko

Reference 1 CP949 (commonly known as EUC-KR)
Reference 2 zVariant and K-source in Unihan.txt

Version 1 20020701 # July 2002

5718(1);5718(1);56E3(2)            # sphere, ball, circle; mass, lump
60F3(1);60F3(1);                   # think, speculate, plan, consider
654E(1);654E(1);6559(2)            # teach
6DF8(1);6DF8(1);6E05(2)            # clear
771E(1);771E(1);771F(2)            # real, actual, true, genuine
806F(1);806F(1);8068(2)            # connect, join; associate, ally
96C6(1);96C6(1);                   # assemble, collect together

Example 1: IDL = (U+6E05 U+771F U+6559) *qing2 zhen1 jiao4*
           {L} = {zh-cn, zh-sg, zh-tw}

NP(IN) = (U+6E05 U+771F U+6559)
PV(IN,zh-cn) = (U+6E05 U+771F U+6559)
PV(IN,zh-sg) = (U+6E05 U+771F U+6559)
PV(IN,zh-tw) = (U+6E05 U+771F U+6559)
{ZV} = (U+6E05 U+771F U+6559)}
CVall = (U+6E05 U+771E U+6559),
        (U+6E05 U+771E U+654E),
        (U+6E05 U+771F U+654E),
        (U+6DF8 U+771E U+6559),
        (U+6DF8 U+771E U+654E),
        (U+6DF8 U+771F U+6559),
        (U+6DF8 U+771F U+654E)}

Example 2: IDL = (U+6E05 U+771F U+6559) *qing2 zhen1 jiao4*
           {L} = {ja}

NP(IN) = (U+6E05 U+771F U+6559)
PV(IN,ja) = (U+6E05 U+771F U+6559)
{ZV} = (U+6E05 U+771F U+6559)}
CVall = (U+6E05 U+771E U+6559),
        (U+6E05 U+771E U+654E),
        (U+6E05 U+771F U+654E),
        (U+6DF8 U+771E U+6559),
        (U+6DF8 U+771E U+654E),
        (U+6DF8 U+771F U+6559),
        (U+6DF8 U+771F U+654E)}

Example 3: IDL = (U+6E05 U+771F U+6559) *qing2 zhen1 jiao4*
           {L} = {zh-cn, zh-sg, zh-tw, ja, ko}

NP(IN) = (U+6E05 U+771F U+6559) *qing2 zhen1 jiao4*
Invalid registration because U+6E05 is invalid in L = ko

Example 4: IDL = (U+806F U+60F3 U+96C6 U+5718)
                 *lian2 xiang3 ji2 tuan2*
           {L} = {zh-cn, zh-sg, zh-tw}

NP(IN) = (U+806F U+60F3 U+96C6 U+5718)
PV(IN,zh-cn) = (U+8054 U+60F3 U+96C6 U+56E2)
PV(IN,zh-sg) = (U+8054 U+60F3 U+96C6 U+56E2)
PV(IN,zh-tw) = (U+806F U+60F3 U+96C6 U+5718)
{ZV} = (U+8054 U+60F3 U+96C6 U+56E2),
       (U+806F U+60F3 U+96C6 U+5718)}
CVall = (U+8054 U+60F3 U+96C6 U+56E3),
        (U+8054 U+60F3 U+96C6 U+5718),
        (U+806F U+60F3 U+96C6 U+56E2),
        (U+806f U+60F3 U+96C6 U+56E3),
        (U+8068 U+60F3 U+96C6 U+56E2),
        (U+8068 U+60F3 U+96C6 U+56E3),
        (U+8068 U+60F3 U+96C6 U+5718)

Example 5: IDL = (U+8054 U+60F3 U+96C6 U+56E2)
                 *lian2 xiang3 ji2 tuan2*
           {L} = {zh-cn, zh-sg}

NP(IN) = (U+8054 U+60F3 U+96C6 U+56E2)
PV(IN,zh-cn) = (U+8054 U+60F3 U+96C6 U+56E2)
PV(IN,zh-sg) = (U+8054 U+60F3 U+96C6 U+56E2)
{ZV} = (U+8054 U+60F3 U+96C6 U+56E2)}
CVall = (U+8054 U+60F3 U+96C6 U+56E3),
        (U+8054 U+60F3 U+96C6 U+5718),
        (U+806F U+60F3 U+96C6 U+56E2),
        (U+806f U+60F3 U+96C6 U+56E3),
        (U+806F U+60F3 U+96C6 U+5718),
        (U+8068 U+60F3 U+96C6 U+56E2),
        (U+8068 U+60F3 U+96C6 U+56E3),
        (U+8068 U+60F3 U+96C6 U+5718)}

Example 6: IDL = (U+8054 U+60F3 U+96C6 U+56E2)
                 *lian2 xiang3 ji2 tuan2*
           {L} = {zh-cn, zh-sg, zh-tw}

NP(IN) = (U+8054 U+60F3 U+96C6 U+56E2)
Invalid registration because U+8054 is invalid in L = zh-tw

Example 7: IDL = (U+806F U+60F3 U+96C6 U+5718)
                 *lian2 xiang3 ji2 tuan2*
           {L} = {ja,ko}

NP(IN) = (U+806F U+60F3 U+96C6 U+5718)
PV(IN,ja) = (U+806F U+60F3 U+96C6 U+5718)
PV(IN,ko) = (U+806F U+60F3 U+96C6 U+5718)
{ZV} = (U+806F U+60F3 U+96C6 U+5718)}
CVall = (U+806F U+60F3 U+96C6 U+56E3),
        (U+8068 U+60F3 U+96C6 U+5718),
        (U+8068 U+60F3 U+96C6 U+56E3)}

5. Syntax Description for the Language Variant Table

The formal syntax for the Language Variant Table is as follows, using
the IETF "ABNF" metalanguage [ABNF].  Some comments on this syntax
appear immediately after it.

5.1 ABNF Syntax

LanguageVariantTable = 1*ReferenceLine VersionLine 1*EntryLine
ReferenceLine = "Reference" SP RefNo SP RefDesciption [ Comment ] CRLF
RefNo = 1*DIGIT
RefDesciption = *[VCHAR]
VersionLine = "Version" SP VersionNo SP VersionDate [ Comment ] CRLF
VersionNo = 1*DIGIT
VersionDate = YYYYMMDD
EntryLine = VariantEntry/Comment CRLF
VariantEntry = ValidCodePoint  ";"
               PreferredVariant ";" CharacterVariant [ Comment ]
ValidCodePoint = CodePoint
RefList = RefNo  0*( "," RefNo )
PreferredVariant = CodePointSet 0*( "," CodePointSet )
CharacterVariant = CodePointSet 0*( "," CodePointSet )
CodePointSet = CodePoint 0*( SP CodePoint )
CodePoint = 4*8DIGIT  [ "(" Reflist ")" ]
Comment = "#" *VCHAR

YYYYMMDD is an integer, in alphabetic form, representing a date, where
YYYY is the 4-digit year, MM is the 2-digit month, and DD is the 2-digit
day.

5.2. Comments and Explanation of Syntax

Any lines starting with, or portions of lines after, the hash
symbol("#") are treated as comments.  Comments have no significance in
the processing of the tables; nor are there any syntax requirements
between the hash symbol and the end of the line.  Blank lines in the
tables are ignored completely.

Every language should have its own Language Variant Table provided by a
relevant group, organization, or other body.  That table will normally
be based on some established standard or standards.  The group that
defines a Language Variant Table should document references to the
appropriate standards at the beginning of the table, tagged with the
word "Reference" followed by an integer (the reference number) followed
by the description of the reference.  For example:

Reference 1 CP936 (commonly known as GBK)
Reference 2 zVariant, zTradVariant, zSimpVariant in Unihan.txt
Reference 3 List of Simplified Character Table (Simplified column)
Reference 4 zSimpVariant in Unihan.txt
Reference 5 Variant that exists in GB2312, common simplified Hanzi

Each Language Variant Table must have a version number and its release
date.  This is tagged with the word "Version" followed by an integer
then followed by the date in the format YYYYMMDD, where YYYY is the
4-digit year, MM is the 2-digit month, and DD is the 2-digit day of the
publication date of the table.

Version 1 20020701     # July 2002 Version 1

The table has three columns, separated by semicolons: "Valid Code
Point"; "Preferred Variant(s)"; and "Character Variant(s)".

The "Valid Code Point" is the subset of Unicode characters that are
valid to be registered.

There can be more than one Preferred Variant; hence there could be
multiple entries in the "Preferred Variant(s)" column.  If the
"Preferred Variant(s)" column is empty, then there is no corresponding
Preferred Variant; in other words, the Preferred Variant is null.
Unless local policy dictates otherwise, the procedures above will result
in only those labels that reflect the valid code point being activated
(registered) into the zone file.

The "Character Variant(s)" column contains all Character Variants of the
Code Point.  Since the Code Point is always a variant of itself, to
avoid redundancy, the Code Point is assumed to be part of the "Character
Variant(s)" and need not be repeated in the "Character Variant(s)"
column.

If the variant in the "Preferred Variant(s)" or the "Character
Variant(s)" column is composed of a sequence of Code Points, then
sequence of Code Points is listed separated by a space.

If there are multiple variants in the "Preferred Variant(s)" or the
"Character Variant(s)" column, then each variant is separated by a
comma.

Any Code Point listed in the "Preferred Variant(s)" column must be
allowed by the rules for the relevant language to be registered.
However, this is not a requirement for the entries in the "Character
Variant(s)" column; it is possible that some of those entries may not be
allowed to be registered.

Every Code Point in the table should have a corresponding reference
number (associated with the references) specified to justify the entry.
The reference number is placed in parentheses after the Code Point.  If
there is more than one reference, then the numbers are placed within a
single set of parentheses and separated by commas.

6. Security Considerations

As discussed in the Introduction, substantially-unrestricted use of
international (non-ASCII) characters in domain name labels may cause
user confusion and invite various types of attacks.   In particular, in
the case of CJK languages, an attacker has an opportunity to divert or
confuse users as a result of different characters (or, more
specifically, assigned code points) with identical or similar semantics.
These Guidelines provide a partial remedy for those risks by supplying
a framework for prohibiting inappropriate characters from being
registered at all and for permitting "variant" characters to be grouped
together and reserved, so that they can only be registered in the DNS by
the same owner.   However, the system it suggests is no better or worse
than the per-zone and per-language tables whose format and use this
document specifies.  Specific tables, and any additional local
processing, will reflect per-zone decisions about the balance between
risk and flexibility of registrations.  And, of course, errors in
construction of those tables may significantly reduce the quality of
protection provided.

7. Index to Terminology

As a convenience to the reader, this section lists all of the special
terminology used in this document, with a pointer to the section in
which it is defined.

Activated Label                 2.1.17
Activation                      2.1.4
Active Label                    2.1.17
Character Variant               2.1.14
Character Variant Label         2.1.16
CJK Characters                  2.1.9
Code point                      2.1.7
Code Point Variant              2.1.14
FQDN                            2.1.3
Hostname                        2.1.1
IDL                             2.1.2
IDL Package                     2.1.18
IDN                             2.1.1
Internationalized Domain Label  2.1.2
ISO/IEC 10646                   2.1.6
Label String                    2.1.10
Language name codes             2.1.5
Language Variant Table          2.1.11
LDH Subset                      2.1.1
Preferred Code Point            2.1.13
Preferred Variant               2.1.13
Preferred Variant Label         2.1.15
Registration                    2.1.4
Reserved                        2.1.18
RFC3066                         2.1.5
Table                           2.1.11
UCS                             2.1.6
Unicode Character               2.1.7
Unicode String                  2.1.8
Valid Code Point                2.1.12
Variant Table                   2.1.11
Zone Variant                    2.1.17


8. Acknowledgments

The authors gratefully acknowledge the contributions of:

- V.  CHEN, N.  HSU, H.  HOTTA, S.  TASHIRO, Y.  YONEYA, and other Joint
Engineering Team members at the JET meeting in Bangkok, Thailand.

- Yves Arrouye, an observer at the JET meeting in Bangkok, for his
contribution on the IDL Package.

- Those who commented on, and made suggestions about, earlier versions,
including Harald ALVESTRAND, Erin CHEN, Patrik FALTSTROM, Paul HOFFMAN,
Soobok LEE, LEE Xiaodong, MAO Wei, Erik NORDMARK, and L.M.  TSENG.

9. Authors’ Addresses

James SENG
Infocomm Development Authority
8 Temasek Boulevard
#14-00 Suntec Tower Three
Singapore 038988
Phone: +65 9638-7085
E-mail: jseng@pobox.org.sg

Kazunori KONISHI
JPNIC
Kokusai-Kougyou-Kanda Bldg 6F
2-3-4 Uchi-Kanda, Chiyoda-ku
Tokyo 101-0047
Japan
Phone: +81 49-278-7313
E-mail: konishi@jp.apan.net

Kenny HUANG
TWNIC
3F, 16, Kang Hwa Street, Taipei
Taiwan
TEL : 886-2-2658-6510
E-mail: huangk@alum.sinica.edu

QIAN Hualin
CNNIC
No.6 Branch-box of No.349 Mailbox, Beijing 100080
Peoples Republic of China
E-mail: Hlqian@cnnic.net.cn

KO YangWoo
PeaceNet
Yangchun P.O. Box 81 Seoul 158-600
Korea
E-mail: newcat@peacenet.or.kr

John C KLENSIN
1770 Massachusetts Avenue, No. 322
Cambridge, MA 02140
U.S.A.
E-mail: Klensin+ietf@jck.com

Wendy RICKARD
The Rickard Group
16 Seminary Ave
Hopewell, NJ  08525
USA
E-mail: rickard@rickardgroup.com

10. Normative References

[ABNF]      Augmented BNF for Syntax Specifications: ABNF, RFC 2234, D.
            Crocker and P.  Overell, eds., November 1997.

[STD13]     Paul Mockapetris, "Domain names--concepts and facilities"
            (RFC 1034) and "Domain names--implementation and
            specification" (RFC 1035), STD 13, November 1987.


[RFC3066]   Tags for the Identification of Languages, RFC3066,
            Jan 2001, H. Alvestrand.

[IDNA]      Internationalizing Domain Names in Applications (IDNA),
            RFC 3490, March 2003, Patrik Faltstrom, Paul Hoffman,
            Adam M. Costello.

[PUNYCODE]  Punycode: A Bootstring encoding of Unicode for
            Internationalized Domain Names in Applications (IDNA),
            RFC 3492, March 2003, Adam M.  Costello.

[STRINGPREP]Preparation of Internationalized Strings ("stringprep"),
            RFC 3454, December 2002, P.  Hoffman, M.  Blanchet.

[NAMEPREP]  Nameprep: A Stringprep Profile for Internationalized
            Domain Names, RFC 3491, March 2003, P. Hoffman, M. Blanchet.

[IS10646]   A product of ISO/IEC JTC1/SC2/WG2, Work Item JTC1.02.18
            (ISO/IEC 10646).  It is a multipart standard: Part 1,
            published as ISO/IEC 10646-1:2000(E), covers the
            Architecture and Basic Multilingual Plane, and Part 2,
            published as ISO/IEC 10646-2:2001(E), covers the
            supplementary (additional) planes.

[UNIHAN]    Unicode Han Database, Unicode Consortium
            ftp://ftp.unicode.org/Public/UNIDATA/Unihan.txt.

[UNICODE]   The Unicode Consortium, "The Unicode Standard--Version
            3.0," ISBN 0-201-61633-5. Unicode Standard Annex #28
            (http://www.unicode.org/unicode/reports/tr28/) defines
            Version 3.2 of the Unicode Standard, which is definitive
            for IDNA and this document.

[ISO7098]   ISO 7098;1991 Information and documentation--Romanization
            of Chinese, ISO/TC46/SC2.

11. Nonnormative References

[IDN-WG]    IETF Internationalized Domain Names Working Group,
            idn@ops.ietf.org, James Seng, Marc Blanchet.
            http://www.i-d-n.net/.

[IESG-IDN] "IESG Statement on IDN", Internet Engineering Steering Group,
            IETF, 11 February 2003,
            http://www.ietf.org/IESG/STATEMENTS/IDNstatement.txt.

[ISO639]    "ISO 639:1988 (E/F)--Code for the representation of names
            of languages"--International Organization for
            Standardization, 1st edition, 1988-04-01.


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