Internet DRAFT - draft-klensin-idnabis-protocol
draft-klensin-idnabis-protocol
Network Working Group J. Klensin, Ed.
Internet-Draft February 6, 2008
Obsoletes: 3490 (if approved)
Intended status: Standards Track
Expires: August 9, 2008
Internationalizing Domain Names in Applications (IDNA): Protocol
draft-klensin-idnabis-protocol-04.txt
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Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
This document supplies the protocol definition for a revised and
updated specification for internationalized domain names (IDNs). The
rationale for these changes, the relationship to the older
specification, and important terminology are provided in other
documents. This document specifies the protocol mechanism, called
Internationalizing Domain Names in Applications (IDNA), for
registering and looking up IDNs in a way that does not require
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changes to the DNS itself. IDNA is only meant for processing domain
names, not free text.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Discussion Forum . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Requirements and Applicability . . . . . . . . . . . . . . . . 5
3.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Applicability . . . . . . . . . . . . . . . . . . . . . . 5
3.2.1. DNS Resource Records . . . . . . . . . . . . . . . . . 5
3.2.2. Non-domain-name Data Types Stored in the DNS . . . . . 6
4. Registration Protocol . . . . . . . . . . . . . . . . . . . . 6
4.1. Proposed label . . . . . . . . . . . . . . . . . . . . . . 6
4.2. Conversion to Unicode and Normalization . . . . . . . . . 6
4.3. Permitted Character and Label Validation . . . . . . . . . 7
4.3.1. Rejection of Characters that are not Permitted . . . . 7
4.3.2. Label Validation . . . . . . . . . . . . . . . . . . . 7
4.3.3. Registration Validation Summary . . . . . . . . . . . 8
4.4. Registry Restrictions . . . . . . . . . . . . . . . . . . 8
4.5. Punycode Conversion . . . . . . . . . . . . . . . . . . . 8
4.6. Insertion in the Zone . . . . . . . . . . . . . . . . . . 8
5. Domain Name Resolution (Lookup) Protocol . . . . . . . . . . . 8
5.1. Label String Input . . . . . . . . . . . . . . . . . . . . 9
5.2. Conversion to Unicode . . . . . . . . . . . . . . . . . . 9
5.3. Character Changes in Preprocessing or the User
Interface . . . . . . . . . . . . . . . . . . . . . . . . 9
5.4. Validation and Character List Testing . . . . . . . . . . 10
5.5. Punycode Conversion . . . . . . . . . . . . . . . . . . . 11
5.6. DNS Name Resolution . . . . . . . . . . . . . . . . . . . 11
6. Name server Considerations . . . . . . . . . . . . . . . . . . 11
6.1. Processing Non-ASCII Strings . . . . . . . . . . . . . . . 11
6.2. DNSSEC Authentication of IDN Domain Names . . . . . . . . 12
6.3. Root Server Considerations . . . . . . . . . . . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
9. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 13
9.1. Version -00 . . . . . . . . . . . . . . . . . . . . . . . 13
9.2. Versions -01 and -02 . . . . . . . . . . . . . . . . . . . 13
9.3. Version -03 . . . . . . . . . . . . . . . . . . . . . . . 14
9.4. Version -04 . . . . . . . . . . . . . . . . . . . . . . . 14
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 14
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
12.1. Normative References . . . . . . . . . . . . . . . . . . . 15
12.2. Informative References . . . . . . . . . . . . . . . . . . 16
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Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 17
Intellectual Property and Copyright Statements . . . . . . . . . . 18
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1. Introduction
This document supplies the protocol definition for a revised and
updated specification for internationalized domain names. The
rationale for these changes and relationship to the older
specification and some new terminology is provided in other
documents, notably [IDNA200X-Rationale].
IDNA works by allowing applications to use certain ASCII string
labels (beginning with a special prefix) to represent non-ASCII name
labels. Lower-layer protocols need not be aware of this; therefore
IDNA does not depend on changes to any infrastructure. In
particular, IDNA does not depend on any changes to DNS servers,
resolvers, or protocol elements, because the ASCII name service
provided by the existing DNS is entirely sufficient for IDNA.
IDNA is applied only to DNS labels. Standards for combining labels
into fully-qualified domain names and parsing labels out of those
names are covered in the base DNS standards [RFC1035]. An
application may, of course, apply locally-appropriate conventions to
the presentation forms of domain names as discussed in
[IDNA200X-Rationale].
While they share terminology, reference data, and some operations,
this document describes two separate protocols, one for IDN
registration (Section 4) and one for IDN lookup (Section 5).
A good deal of the background material that appeared in RFC 3490 has
been removed from this update. That material is either of historical
interest only or has been covered from a more recent perspective in
RFC 4690 [RFC4690] and [IDNA200X-Rationale].
[[anchor2: Note in Draft: This document still needs more specifics
about how to perform some of the tests in the Registration and Lookup
protocols described below. Those details will be supplied in a later
revision, but the intent should be clear from the existing text.]]
1.1. Discussion Forum
[[anchor4: RFC Editor: please remove this section.]]
This work is being discussed on the mailing list
idna-update@alvestrand.no
2. Terminology
General terminology applicable to IDNA, but with meanings familiar to
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those who have worked with Unicode or other character set standards
and the DNS, appears in [IDNA200X-Rationale]. Terminology that is an
integral, normative, part of the IDNA definition, including the
definitions of "ACE", appears in that document as well. Familiarity
with the terminology materials in that document is assumed for
reading this one.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, RFC 2119
[RFC2119].
3. Requirements and Applicability
3.1. Requirements
IDNA conformance means adherence to the following requirements:
1. Whenever a domain name is put into an IDN-unaware domain name
slot (see Section 2 and [IDNA200X-Rationale]), it MUST contain
only ASCII characters (i.e., must be either an A-label or an LDH-
label), or must a label associated with a DNS application that is
not subject to either IDNA or the historical recommendations for
"hostname"-style names [RFC1034].
2. Comparison of labels MUST be done on the A-label form, using an
ASCII case-insensitive comparison as with all comparisons of DNS
labels.
3.2. Applicability
IDNA is applicable to all domain names in all domain name slots
except where it is explicitly excluded. It is not applicable to
domain name slots which do not use the LDH syntax rules.
This implies that IDNA is applicable to many protocols that predate
IDNA. Note that IDNs occupying domain name slots in those protocols
MUST be in A-label form.
3.2.1. DNS Resource Records
IDNA applies only to domain names in the NAME and RDATA fields of DNS
resource records whose CLASS is IN.
There are currently no other exclusions on the applicability of IDNA
to DNS resource records. Applicability depends entirely on the
CLASS, and not on the TYPE. This will remain true, even as new types
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are defined, unless there is a compelling reason for a new type that
requires type-specific rules. It is worth noting that the special
naming conventions applicable to SRV records are precisely such type-
specific rules and that the SRV requirement for a leading underscore
("_") in some labels is incompatible with IDNA coding.
3.2.2. Non-domain-name Data Types Stored in the DNS
Although IDNA enables the representation of non-ASCII characters in
domain names, that does not imply that IDNA enables the
representation of non-ASCII characters in other data types that are
stored in domain names, specifically in the RDATA field for types
that have structured RDATA format. For example, an email address
local part is stored in a domain name in the RNAME field as part of
the RDATA of an SOA record (hostmaster@example.com would be
represented as hostmaster.example.com). IDNA specifically does not
update the existing email standards, which allow only ASCII
characters in local parts. Other work is under development to define
internationalization for email addresses [RFC4952], but changes to
the email address part of the SOA RDATA would require action in other
standards. Such standards could also specify IDNA interpretation of
labels that follow the local part such as by permitting them to be
A-labels or even U-labels.
4. Registration Protocol
This section defines the procedure for registering an IDN. The
procedure is implementation independent; any sequence of steps that
produces exactly the same result for all labels is considered a valid
implementation.
4.1. Proposed label
The registrant submits a request for an IDN. The user typically
produces the request string by the keyboard entry of a character
sequence.
4.2. Conversion to Unicode and Normalization
Some system routine, or a localized front-end to the IDNA process,
ensures that the proposed label is a Unicode string. That string
MUST be in Unicode Normalization Form C (NFC [Unicode-UAX15]).
As a local implementation choice, the implementation MAY choose to
map some forbidden characters to permitted characters (for instance
mapping uppercase characters to lowercase ones), displaying the
result to the user, and allowing processing to continue. However, it
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is strongly recommended that, to avoid any possible ambiguity,
entities responsible for zone files ("registries") accept
registrations only for A-labels or U-labels actually produced from
A-labels, not forms expected to be converted by some other process.
4.3. Permitted Character and Label Validation
4.3.1. Rejection of Characters that are not Permitted
The Unicode string is examined to prohibit characters that IDNA does
not permit in input. Those characters are identified in the
"DISALLOWED" and "UNASSIGNED" lists that are discussed in
[IDNA200X-Rationale]. The normative rules for producing that list
and the initial version of it are specified in [IDNA200X-Tables].
Characters that are either DISALLOWED or UNASSIGNED MUST NOT be part
of labels being processed for registration in the DNS.
4.3.2. Label Validation
The proposed label is then examined, performing tests that require
examination of more than one character.
4.3.2.1. Leading Combining Marks
The first character of the string is examined to verify that it is
not a combining mark. If it is a combining mark, the string MUST NOT
be registered.
4.3.2.2. Contextual Rules
Each code point is checked for its identification as characters for
registration (the list of characters appears as the combination of
CONTEXTJ and CONTEXTO in [IDNA200X-Tables]). If that indication
appears, the table of contextual rules is checked for a rule for that
character. If no rule is found, the proposed label is rejected and
MUST NOT be installed in a zone file. If one is found, it is applied
(typically as a test on the entire label or on adjacent characters).
If the application of the rule does not conclude that the character
is valid in context, the proposed label MUST BE rejected. (See the
IANA Considerations: IDNA Context Registry section of
[IDNA200X-Rationale].)
4.3.2.3. Labels Containing Characters Written Right to Left
Additional special tests for right-to-left strings are applied (See
[IDNA200X-BIDI]. Strings that contain right to left characters that
do not conform to the rule identified there MUST NOT be inserted in
zone files.
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4.3.3. Registration Validation Summary
Strings that have been produced by the steps above, and whose
contents pass the above tests, are U-labels.
To summarize, tests are made here for invalid characters, invalid
combinations of characters, and for labels that are invalid even if
the characters they contain are valid individually. For example,
labels containing invisible ("zero-width") characters may be
permitted in context with characters whose presentation forms are
significantly changed by the presence or absence of the zero-width
characters, while other labels in which zero-width characters appear
may be rejected.
4.4. Registry Restrictions
Registries at all levels of the DNS, not just the top level, are
expected to establish policies about the labels that may be
registered, and for the processes associated with that action. While
exact policies are not specified as part of IDNA200X and it is
expected that different registries may specify different policies,
there SHOULD be policies. These per-registry policies and
restrictions are an essential element of the IDNA registration
protocol even for registries (and corresponding zone files) deep in
the DNS hierarchy. As discussed in [IDNA200X-Rationale], such
restrictions have always existed in the DNS.
The string produced by the above steps is checked and processed as
appropriate to local registry restrictions. Application of those
registry restrictions may result in the rejection of some labels or
the application of special restrictions to others.
4.5. Punycode Conversion
The resulting U-label is converted to an A-label (i.e., the encoding
of that label according to the Punycode algorithm [RFC3492] with the
prefix included, i.e., the "xn--..." form).
4.6. Insertion in the Zone
The A-label is registered in the DNS by insertion into a zone.
5. Domain Name Resolution (Lookup) Protocol
Resolution is conceptually different from registration and different
tests are applied on the client. Although some validity checks are
necessary to avoid serious problems with the protocol (see
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Section 5.4 ff.), the resolution-side tests are more permissive and
rely heavily on the assumption that names that are present in the DNS
are valid. Among other things, this distinction, applied carefully,
facilitates expansion of the permitted character lists to include new
scripts and accommodate new versions of Unicode without introducing
ambiguity into domain name processing.
5.1. Label String Input
The user supplies a string in the local character set, typically by
typing it or clicking on, or copying and pasting, a resource
identifier, e.g., a URI [RFC3986] or IRI [RFC3987] from which the
domain name is extracted. Or some process not directly involving the
user may read the string from a file or obtain it in some other way.
Processing in this step and the next two are local matters, to be
accomplished prior to actual invocation of IDNA, but at least this
one and the next one must be accomplished in some way.
5.2. Conversion to Unicode
The local character set, character coding conventions, and, as
necessary, display and presentation conventions, are converted to
Unicode (without surrogates), paralleling the process described above
in Section 4.2.
5.3. Character Changes in Preprocessing or the User Interface
The Unicode string MAY then be processed, in a way specific to the
local environment, to make the result of the IDNA processing match
user expectations. For instance, at this step, it would be
reasonable to convert all upper case characters to lower case, if
this makes sense in the user's environment.
Other examples of processing for localization that might be applied,
if appropriate, at this point (but even further outside the scope of
this specification) include interpreting the KANA MIDDLE DOT as
separating domain name components from each other, mapping different
"width" forms of the same character into the one form permitted in
labels, or giving special treatment to characters whose presentation
forms are dependent only on placement in the label.
Recommendations for preprocessing for global contexts (i.e., when
local considerations do not apply or cannot be used) and for maximum
interoperability with labels that might have been specified under
liberal readings of IDNA2003 are given in [IDNA200X-Rationale].
Because these transformations are local, it is important that domain
names that might be passed between systems (e.g., in IRIs) be
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U-labels or A-labels and not forms that might be accepted locally as
a consequence of this step. This step is not standardized as part of
IDNA, and is not further specified here.
5.4. Validation and Character List Testing
In parallel with the registration procedure, the Unicode string is
checked to verify that all characters that appear in it are valid for
IDNA resolution input. As discussed in [IDNA200X-Rationale], the
resolution check is more liberal than that of the registration one.
Putative labels with any of the following characteristics MUST BE
rejected prior to DNS lookup:
o Labels containing code points that are unassigned in the version
of Unicode being used by the application, i.e., in the
"Unassigned" Unicode category or the UNASSIGNED category of
[IDNA200X-Tables].
o Labels that are not in NFC form.
o Labels containing prohibited code points, i.e., those that are
assigned to the "DISALLOWED" category in the permitted character
table [IDNA200X-Tables].
o Labels containing code points that are shown in the permitted
character table as requiring a contextual rule and that are
flagged as requiring exceptional special processing on lookup
("CONTEXTJ" in the Tables) MUST conform to the rule, which MUST be
present.
o Labels containing other code points that are shown in the
permitted character table as requiring a contextual rule
("CONTEXTO" in the tables), but for which no such rule appears in
the table of rules. With the exception in the rule immediately
above, applications resolving DNS names or carrying out equivalent
operations are not required to test contextual rules, only to
verify that a rule exists.
o Labels whose first character is a combining mark. [[anchor15: Note
in Draft: this definition may need to be further tightened.]]
In addition, the application SHOULD apply the following test. The
test may be omitted in special circumstances, such as when the
resolver application knows that the conditions are enforced
elsewhere, because an attempt to resolve such strings will almost
certainly lead to a DNS lookup failure. However, applying the test
is likely to give much better information about the reason for a
lookup failure -- information that may be usefully passed to the user
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when that is feasible -- then DNS resolution failure alone.
o Verification that the string is compliant with the requirements
for right to left characters, specified in [IDNA200X-BIDI].
For all other strings, the resolver MUST rely on the presence or
absence of labels in the DNS to determine the validity of those
labels and the validity of the characters they contain. If they are
registered, they are presumed to be valid; if they are not, their
possible validity is not relevant. A resolver that declines to look
up a string that conforms to the above rules is not in conformance
with this protocol.
5.5. Punycode Conversion
The validated string, a U-label, is converted to an A-label using the
punycode algorithm.
5.6. DNS Name Resolution
The A-label is looked up in the DNS, using normal DNS procedures.
6. Name server Considerations
6.1. Processing Non-ASCII Strings
Existing DNS servers do not know the IDNA rules for handling non-
ASCII forms of IDNs, and therefore need to be shielded from them.
All existing channels through which names can enter a DNS server
database (for example, master files (as described in RFC 1034) and
DNS update messages [RFC2136]) are IDN-unaware because they predate
IDNA. Other sections of this document provide the needed shielding
by ensuring that internationalized domain names entering DNS server
databases through such channels have already been converted to their
equivalent ASCII A-label forms.
Because of the design of the algorithms in Section 4 and Section 5 (a
domain name containing only ASCII codepoints can not be converted to
an A-label), there can not be more than one label for each domain
name.
The current definition of the DNS protocol [RFC2181] explicitly
allows domain labels to contain octets beyond the ASCII range
(0000..007F), and this document does not change that. Note, however,
that there is no defined interpretation of octets 0080..00FF as
characters. If labels containing these octets are returned to
applications, unpredictable behavior could result. The A-label form,
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which cannot contain those characters, is the only standard
representation for internationalized labels in the current DNS
protocol.
6.2. DNSSEC Authentication of IDN Domain Names
DNS Security [RFC2535] is a method for supplying cryptographic
verification information along with DNS messages. Public Key
Cryptography is used in conjunction with digital signatures to
provide a means for a requester of domain information to authenticate
the source of the data. This ensures that it can be traced back to a
trusted source, either directly or via a chain of trust linking the
source of the information to the top of the DNS hierarchy.
IDNA specifies that all internationalized domain names served by DNS
servers that cannot be represented directly in ASCII must use the
A-label form. Conversion to A-labels must be performed prior to a
zone being signed by the private key for that zone. Because of this
ordering, it is important to recognize that DNSSEC authenticates a
domain name containing A-labels or conventional LDH-labels, not
U-labels. In the presence of DNSSEC, no form of a zone file or query
response that contains a U-label may be signed or validated against.
One consequence of this for sites deploying IDNA in the presence of
DNSSEC is that any special purpose proxies or forwarders used to
transform user input into IDNs must be earlier in the resolution flow
than DNSSEC authenticating nameservers for DNSSEC to work.
6.3. Root Server Considerations
IDNs are likely to be somewhat longer than current domain names, so
the bandwidth needed by the root servers is likely to go up by a
small amount. Also, queries and responses for IDNs will probably be
somewhat longer than typical queries today, so more queries and
responses may be forced to go to TCP instead of UDP.
7. Security Considerations
The general security principles and issues for IDNA appear in
[IDNA200X-Rationale]. The comments below are specific to this pair
of protocols, but should be read in the context of that material and
the definitions and specifications, identified there, on which this
one depends.
This memo describes procedures for registering and looking up labels
that are not valid according to the base DNS specifications (STD13
[RFC1034] [RFC1035] and Host Requirements [RFC1123]) because they
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contain non-ASCII characters. Those procedures depends on the use of
a special ACE encoded form, with the encoding specified in [RFC3492],
that contains only characters permitted in host names by those
specifications. No security issues such as string length increases
or new allowed values are introduced by the encoding process or the
use of these encoded values, apart from those introduced by the ACE
encoding itself.
Domain names (or portions of them) are sometimes compared against a
set of privileged or anti-privileged domains. In such situations it
is especially important that the comparisons be done properly, as
specified in requirement 2 of Section 3.1. For labels already in
ASCII form (i.e., are LDH-labels or A-labels), the proper comparison
reduces to the same case-insensitive ASCII comparison that has always
been used for ASCII labels.
The introduction of IDNA means that any existing labels that start
with the ACE prefix would be construed as U-labels, at least until
they failed one of the relevant tests, whether or not that was the
intent of the zone administrator or registrant. There is no evidence
that this has caused any practical problems since RFC 3490 was
adopted, but the risk still exists in principle.
8. IANA Considerations
IANA actions for this version of IDNA are specified in
[IDNA200X-Rationale].
9. Change Log
[[anchor22: RFC Editor: Please remove this section.]]
9.1. Version -00
Version -00 of this draft was produced in November 2007 by moving
text from draft-klensin-idnabis-issues and by copy considerable text
from RFC 3490. The result was then extensively edited.
9.2. Versions -01 and -02
These versions reflected a number of editorial changes, some of them
significant, and alignment of terminology with
draft-faltstrom-idnabis-tables.
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9.3. Version -03
o Abstract rewritten to bring its length within RFC Editor
guidelines.
o Corrections and revisions in response to extensive comments by
Mark Davis and others.
o Small modifications to several operations, including moving the
Normalization steps to a different place in the sequence.
o Many editorial changes.
9.4. Version -04
o Revised terminology and removed the MAYBE category as a
consequence of design discussions on 30 January 2003 and followup
conversations. Also restructed the various operations to treat
CONTEXTUAL RULE REQUIRED as a validation step (paralleling bidi),
rather than a category. Those changes required changes elsewhere
in the document for consistency.
o Changed the requirements for normalization, making this a
requirement on the calling application rather than an action of
this protocol. This is consistent with the general "mappings
belong somewhere else" principle.
o Updated references.
o More editorial work, some independent of the changes, described
immediately above.
10. Contributors
While the listed editor held the pen, this document represents the
joint work and conclusions of an ad hoc design team consisting of the
editor and, in alphabetic order, Harald Alvestrand, Tina Dam, Patrik
Faltstrom, and Cary Karp. This document draws significantly on the
original version of IDNA [RFC3490] both conceptually and for specific
text. This second-generation version would not have been possible
without the work that went into that first version and its authors,
Patrik Faltstrom, Paul Hoffman, and Adam Costello. While Faltstrom
was actively involved in the creation of this version, Hoffman and
Costello were not and should not be held responsible for any errors
or omissions.
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11. Acknowledgements
This revision to IDNA would have been impossible without the
accumulated experience since RFC 3490 was published and resulting
comments and complaints of many people in the IETF, ICANN, and other
communities, too many people to list here. Nor would it have been
possible without RFC 3490 itself and the efforts of the Working Group
that defined it. Those people whose contributions are acknowledged
in RFC 3490, [RFC4690], and [IDNA200X-Rationale] were particularly
important.
12. References
12.1. Normative References
[IDNA200X-BIDI]
Alvestrand, H. and C. Karp, "An updated IDNA criterion for
right-to-left scripts", January 2008, <http://
www.ietf.org/internet-drafts/
draft-alvestrand-idna-bidi-03.txt>.
[IDNA200X-Rationale]
Klensin, J., Ed., "Internationalizing Domain Names for
Applications (IDNA): Issues, Explanation, and Rationale",
February 2008, <http://www.ietf.org/internet-drafts/
draft-klensin-idnabis-issues-06.txt>.
[IDNA200X-Tables]
Faltstrom, P., "The Unicode Codepoints and IDN",
February 2008, <http://stupid.domain.name/idnabis/
draft-faltstrom-idnabis-tables-04.txt>.
A version of this document, is available in HTML format at
http://stupid.domain.name/idnabis/
draft-faltstrom-idnabis-tables-04.html
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, November 1987.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC1123] Braden, R., "Requirements for Internet Hosts - Application
and Support", STD 3, RFC 1123, October 1989.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC3492] Costello, A., "Punycode: A Bootstring encoding of Unicode
for Internationalized Domain Names in Applications
(IDNA)", RFC 3492, March 2003.
[Unicode-UAX15]
The Unicode Consortium, "Unicode Standard Annex #15:
Unicode Normalization Forms", 2006,
<http://www.unicode.org/reports/tr15/>.
12.2. Informative References
[ASCII] American National Standards Institute (formerly United
States of America Standards Institute), "USA Code for
Information Interchange", ANSI X3.4-1968, 1968.
ANSI X3.4-1968 has been replaced by newer versions with
slight modifications, but the 1968 version remains
definitive for the Internet.
[RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound,
"Dynamic Updates in the Domain Name System (DNS UPDATE)",
RFC 2136, April 1997.
[RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS
Specification", RFC 2181, July 1997.
[RFC2535] Eastlake, D., "Domain Name System Security Extensions",
RFC 2535, March 1999.
[RFC3490] Faltstrom, P., Hoffman, P., and A. Costello,
"Internationalizing Domain Names in Applications (IDNA)",
RFC 3490, March 2003.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005.
[RFC4690] Klensin, J., Faltstrom, P., Karp, C., and IAB, "Review and
Recommendations for Internationalized Domain Names
(IDNs)", RFC 4690, September 2006.
[RFC4952] Klensin, J. and Y. Ko, "Overview and Framework for
Internationalized Email", RFC 4952, July 2007.
[Unicode] The Unicode Consortium, "The Unicode Standard, Version
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5.0", 2007.
Boston, MA, USA: Addison-Wesley. ISBN 0-321-48091-0
Author's Address
John C Klensin (editor)
1770 Massachusetts Ave, Ste 322
Cambridge, MA 02140
USA
Phone: +1 617 245 1457
Fax:
Email: john+ietf@jck.com
URI:
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