draft-ietf-idnabis-protocol-14.txt   draft-ietf-idnabis-protocol-15.txt 
Network Working Group J. Klensin Network Working Group J. Klensin
Obsoletes: 3490, 3491 Obsoletes: 3490, 3491
(if approved) (if approved)
Updates: 3492 (if approved) Updates: 3492 (if approved)
Intended status: Standards Track Intended status: Standards Track
Expires: February 10, 2010 Expires: March 5, 2010
Internationalized Domain Names in Applications (IDNA): Protocol Internationalized Domain Names in Applications (IDNA): Protocol
draft-ietf-idnabis-protocol-14.txt draft-ietf-idnabis-protocol-15.txt
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
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Abstract Abstract
This document is the revised protocol definition for This document is the revised protocol definition for
internationalized domain names (IDNs). The rationale for changes, internationalized domain names (IDNs). The rationale for changes,
the relationship to the older specification, and important the relationship to the older specification, and important
terminology are provided in other documents. This document specifies terminology are provided in other documents. This document specifies
the protocol mechanism, called Internationalizing Domain Names in the protocol mechanism, called Internationalized Domain Names in
Applications (IDNA), for registering and looking up IDNs in a way Applications (IDNA), for registering and looking up IDNs in a way
that does not require changes to the DNS itself. IDNA is only meant that does not require changes to the DNS itself. IDNA is only meant
for processing domain names, not free text. for processing domain names, not free text.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Discussion Forum . . . . . . . . . . . . . . . . . . . . . 5 1.1. Discussion Forum . . . . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Requirements and Applicability . . . . . . . . . . . . . . . . 6 3. Requirements and Applicability . . . . . . . . . . . . . . . . 6
skipping to change at page 3, line 26 skipping to change at page 3, line 26
4.1. Input to IDNA Registration Process . . . . . . . . . . . . 8 4.1. Input to IDNA Registration Process . . . . . . . . . . . . 8
4.2. Permitted Character and Label Validation . . . . . . . . . 8 4.2. Permitted Character and Label Validation . . . . . . . . . 8
4.2.1. Input Format . . . . . . . . . . . . . . . . . . . . . 8 4.2.1. Input Format . . . . . . . . . . . . . . . . . . . . . 8
4.2.2. Rejection of Characters that are not Permitted . . . . 8 4.2.2. Rejection of Characters that are not Permitted . . . . 8
4.2.3. Label Validation . . . . . . . . . . . . . . . . . . . 8 4.2.3. Label Validation . . . . . . . . . . . . . . . . . . . 8
4.2.4. Registration Validation Summary . . . . . . . . . . . 9 4.2.4. Registration Validation Summary . . . . . . . . . . . 9
4.3. Registry Restrictions . . . . . . . . . . . . . . . . . . 9 4.3. Registry Restrictions . . . . . . . . . . . . . . . . . . 9
4.4. Punycode Conversion . . . . . . . . . . . . . . . . . . . 10 4.4. Punycode Conversion . . . . . . . . . . . . . . . . . . . 10
4.5. Insertion in the Zone . . . . . . . . . . . . . . . . . . 10 4.5. Insertion in the Zone . . . . . . . . . . . . . . . . . . 10
5. Domain Name Lookup Protocol . . . . . . . . . . . . . . . . . 10 5. Domain Name Lookup Protocol . . . . . . . . . . . . . . . . . 10
5.1. Label String Input . . . . . . . . . . . . . . . . . . . . 10 5.1. Label String Input . . . . . . . . . . . . . . . . . . . . 11
5.2. Conversion to Unicode . . . . . . . . . . . . . . . . . . 11 5.2. Conversion to Unicode . . . . . . . . . . . . . . . . . . 11
5.3. A-label Input . . . . . . . . . . . . . . . . . . . . . . 11 5.3. A-label Input . . . . . . . . . . . . . . . . . . . . . . 11
5.4. Validation and Character List Testing . . . . . . . . . . 11 5.4. Validation and Character List Testing . . . . . . . . . . 12
5.5. Punycode Conversion . . . . . . . . . . . . . . . . . . . 13 5.5. Punycode Conversion . . . . . . . . . . . . . . . . . . . 13
5.6. DNS Name Resolution . . . . . . . . . . . . . . . . . . . 13 5.6. DNS Name Resolution . . . . . . . . . . . . . . . . . . . 13
6. Security Considerations . . . . . . . . . . . . . . . . . . . 13 6. Security Considerations . . . . . . . . . . . . . . . . . . . 13
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 14 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 14
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
10.1. Normative References . . . . . . . . . . . . . . . . . . . 14 10.1. Normative References . . . . . . . . . . . . . . . . . . . 15
10.2. Informative References . . . . . . . . . . . . . . . . . . 16 10.2. Informative References . . . . . . . . . . . . . . . . . . 16
Appendix A. Summary of Major Changes from IDNA2003 . . . . . . . 17 Appendix A. Summary of Major Changes from IDNA2003 . . . . . . . 17
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 18 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 18
B.1. Changes between Version -00 and -01 of B.1. Changes between Version -00 and -01 of
draft-ietf-idnabis-protocol . . . . . . . . . . . . . . . 18 draft-ietf-idnabis-protocol . . . . . . . . . . . . . . . 18
B.2. Version -02 . . . . . . . . . . . . . . . . . . . . . . . 18 B.2. Version -02 . . . . . . . . . . . . . . . . . . . . . . . 18
B.3. Version -03 . . . . . . . . . . . . . . . . . . . . . . . 18 B.3. Version -03 . . . . . . . . . . . . . . . . . . . . . . . 19
B.4. Version -04 . . . . . . . . . . . . . . . . . . . . . . . 19 B.4. Version -04 . . . . . . . . . . . . . . . . . . . . . . . 19
B.5. Version -05 . . . . . . . . . . . . . . . . . . . . . . . 19 B.5. Version -05 . . . . . . . . . . . . . . . . . . . . . . . 19
B.6. Version -06 . . . . . . . . . . . . . . . . . . . . . . . 19 B.6. Version -06 . . . . . . . . . . . . . . . . . . . . . . . 19
B.7. Version -07 . . . . . . . . . . . . . . . . . . . . . . . 19 B.7. Version -07 . . . . . . . . . . . . . . . . . . . . . . . 20
B.8. Version -08 . . . . . . . . . . . . . . . . . . . . . . . 19 B.8. Version -08 . . . . . . . . . . . . . . . . . . . . . . . 20
B.9. Version -09 . . . . . . . . . . . . . . . . . . . . . . . 20 B.9. Version -09 . . . . . . . . . . . . . . . . . . . . . . . 20
B.10. Version -10 . . . . . . . . . . . . . . . . . . . . . . . 20 B.10. Version -10 . . . . . . . . . . . . . . . . . . . . . . . 21
B.11. Version -11 . . . . . . . . . . . . . . . . . . . . . . . 21 B.11. Version -11 . . . . . . . . . . . . . . . . . . . . . . . 21
B.12. Version -12 . . . . . . . . . . . . . . . . . . . . . . . 21 B.12. Version -12 . . . . . . . . . . . . . . . . . . . . . . . 21
B.13. Version -13 . . . . . . . . . . . . . . . . . . . . . . . 21 B.13. Version -13 . . . . . . . . . . . . . . . . . . . . . . . 22
B.14. Version -14 . . . . . . . . . . . . . . . . . . . . . . . 22 B.14. Version -14 . . . . . . . . . . . . . . . . . . . . . . . 22
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 22 B.15. Version -15 . . . . . . . . . . . . . . . . . . . . . . . 22
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 23
1. Introduction 1. Introduction
This document supplies the protocol definition for internationalized This document supplies the protocol definition for internationalized
domain names. Essential definitions and terminology for domain names. Essential definitions and terminology for
understanding this document and a road map of the collection of understanding this document and a road map of the collection of
documents that make up IDNA2008 appear in [IDNA2008-Defs]. documents that make up IDNA2008 appear in [IDNA2008-Defs].
Appendix A discusses the relationship between this specification and Appendix A discusses the relationship between this specification and
the earlier version of IDNA (referred to here as "IDNA2003") and the the earlier version of IDNA (referred to here as "IDNA2003"). The
rationale for these changes, along with considerable explanatory rationale for these changes, along with considerable explanatory
material and advice to zone administrators who support IDNs is material and advice to zone administrators who support IDNs is
provided in another document, [IDNA2008-Rationale]. provided in another document, [IDNA2008-Rationale].
IDNA works by allowing applications to use certain ASCII string IDNA works by allowing applications to use certain ASCII string
labels (beginning with a special prefix) to represent non-ASCII name labels (beginning with a special prefix) to represent non-ASCII name
labels. Lower-layer protocols need not be aware of this; therefore labels. Lower-layer protocols need not be aware of this; therefore
IDNA does not changes any infrastructure. In particular, IDNA does IDNA does not change any infrastructure. In particular, IDNA does
not depend on any changes to DNS servers, resolvers, or protocol not depend on any changes to DNS servers, resolvers, or protocol
elements, because the ASCII name service provided by the existing DNS elements, because the ASCII name service provided by the existing DNS
can be used for IDNA. can be used for IDNA.
IDNA applies only to DNS labels. The base DNS standards [RFC1034] IDNA applies only to DNS labels. The base DNS standards [RFC1034]
[RFC1035] and their various updates specify how to combine labels [RFC1035] and their various updates specify how to combine labels
into fully-qualified domain names and parse labels out of those into fully-qualified domain names and parse labels out of those
names. names.
This document describes two separate protocols, one for IDN This document describes two separate protocols, one for IDN
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Section 3.2.1). Section 3.2.1).
2. Labels MUST be compared using equivalent forms: either both 2. Labels MUST be compared using equivalent forms: either both
A-Label forms or both U-Label forms. Because A-labels and A-Label forms or both U-Label forms. Because A-labels and
U-labels can be transformed into each other without loss of U-labels can be transformed into each other without loss of
information, these comparisons are equivalent. A pair of information, these comparisons are equivalent. A pair of
A-labels MUST be compared as case-insensitive ASCII (as with all A-labels MUST be compared as case-insensitive ASCII (as with all
comparisons of ASCII DNS labels). U-labels must be compared comparisons of ASCII DNS labels). U-labels must be compared
as-is, without case-folding or other intermediate steps. Note as-is, without case-folding or other intermediate steps. Note
that it is not necessary to validate labels in order to compare that it is not necessary to validate labels in order to compare
them. In many cases, validation may be important for other them and that successful comparison does not imply validity. In
reasons and SHOULD be performed. many cases, validation may be important for other reasons and
SHOULD be performed.
3. Labels being registered MUST conform to the requirements of 3. Labels being registered MUST conform to the requirements of
Section 4. Labels being looked up and the lookup process MUST Section 4. Labels being looked up and the lookup process MUST
conform to the requirements of Section 5. conform to the requirements of Section 5.
3.2. Applicability 3.2. Applicability
IDNA applies to all domain names in all domain name slots in IDNA applies to all domain names in all domain name slots in
protocols except where it is explicitly excluded. It does not apply protocols except where it is explicitly excluded. It does not apply
to domain name slots which do not use the Letter/Digit/Hyphen (LDH) to domain name slots which do not use the Letter/Digit/Hyphen (LDH)
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are very similar in most respects, they are different and are very similar in most respects, they are different and
implementers should carefully follow the appropriate steps. implementers should carefully follow the appropriate steps.
4.1. Input to IDNA Registration Process 4.1. Input to IDNA Registration Process
Registration processes, especially processing by entities, such as Registration processes, especially processing by entities, such as
"registrars" who deal with registrants before the request actually "registrars" who deal with registrants before the request actually
reaches the zone manager ("registry") are outside the scope of these reaches the zone manager ("registry") are outside the scope of these
protocols and may differ significantly depending on local needs. By protocols and may differ significantly depending on local needs. By
the time a string enters the IDNA registration process as described the time a string enters the IDNA registration process as described
in this specification, it is expected to be in Unicode and MUST be in in this specification, it MUST be in Unicode and in Normalization
Unicode Normalization Form C (NFC [Unicode-UAX15]). Entities Form C (NFC [Unicode-UAX15]). Entities responsible for zone files
responsible for zone files ("registries") are expected to accept only ("registries") are expected to accept only the exact string for which
the exact string for which registration is requested, free of any registration is requested, free of any mappings or local adjustments.
mappings or local adjustments. They SHOULD avoid any possible They SHOULD avoid any possible ambiguity by accepting registrations
ambiguity by accepting registrations only for A-labels, possibly only for A-labels, possibly paired with the relevant U-labels so that
paired with the relevant U-labels so that they can verify the they can verify the correspondence.
correspondence.
4.2. Permitted Character and Label Validation 4.2. Permitted Character and Label Validation
4.2.1. Input Format 4.2.1. Input Format
The registry SHOULD permit submission of labels in A-label form and The registry SHOULD permit submission of labels in A-label form and
is encouraged to accept both the A-label form and the U-label one. is encouraged to accept both the A-label form and the U-label one.
If it does so, it MUST perform a conversion to a U-label, perform the If both label forms are available, it MUST ensure that the A-label
steps and tests described below, and verify that the A-label produced form is in lower case, perform a conversion to a U-label, perform the
by the step in Section 4.4 matches the one provided as input. In steps and tests described below on that U-label, and then verify that
addition, if a U-label was provided, that U-label and the one the A-label produced by the step in Section 4.4 matches the one
obtained by conversion of the A-label MUST match exactly. If, for provided as input. In addition, if a U-label was provided, that
some reason, these tests fail, the registration MUST be rejected. If U-label and the one obtained by conversion of the A-label MUST match
the conversion to a U-label is not performed, the registry MUST still exactly. If, for some reason, these tests fail, the registration
verify that the A-label is superficially valid, i.e., that it does MUST be rejected. If the conversion to a U-label is not performed,
not violate any of the rules of Punycode [RFC3492] encoding such as the registry MUST still verify that the A-label is superficially
the prohibition on trailing hyphen-minus, appearance of non-basic valid, i.e., that it does not violate any of the rules of Punycode
characters before the delimiter, and so on. Fake A-labels, i.e., [RFC3492] encoding such as the prohibition on trailing hyphen-minus,
invalid strings that appear to be A-labels but are not, MUST NOT be appearance of non-basic characters before the delimiter, and so on.
placed in DNS zones that support IDNA. Fake A-labels, i.e., invalid strings that appear to be A-labels but
are not, MUST NOT be placed in DNS zones that support IDNA.
4.2.2. Rejection of Characters that are not Permitted 4.2.2. Rejection of Characters that are not Permitted
The candidate Unicode string MUST NOT contain characters in the The candidate Unicode string MUST NOT contain characters that appear
"DISALLOWED" and "UNASSIGNED" lists specified in [IDNA2008-Tables]. in the "DISALLOWED" and "UNASSIGNED" lists specified in
[IDNA2008-Tables].
4.2.3. Label Validation 4.2.3. Label Validation
The proposed label (in the form of a Unicode string, i.e., a string The proposed label (in the form of a Unicode string, i.e., a string
that at least superficially appears to be a U-label) is then that at least superficially appears to be a U-label) is then
examined, performing tests that require examination of more than one examined, performing tests that require examination of more than one
character. Character order is considered to be the on-the-wire character. Character order is considered to be the on-the-wire
order, not the display order. order, not the display order.
4.2.3.1. Consecutive Hyphens 4.2.3.1. Hyphen Restrictions
The Unicode string MUST NOT contain "--" (two consecutive hyphens) in The Unicode string MUST NOT contain "--" (two consecutive hyphens) in
the third and fourth character positions. the third and fourth character positions and MUST NOT start or end
with a "-" (hyphen).
4.2.3.2. Leading Combining Marks 4.2.3.2. Leading Combining Marks
The Unicode string MUST NOT begin with a combining mark or combining The Unicode string MUST NOT begin with a combining mark or combining
character (see The Unicode Standard, Section 2.11 [Unicode] for an character (see The Unicode Standard, Section 2.11 [Unicode] for an
exact definition). exact definition).
4.2.3.3. Contextual Rules 4.2.3.3. Contextual Rules
The Unicode string MUST NOT contain any characters whose validity is The Unicode string MUST NOT contain any characters whose validity is
context-dependent, unless the validity is positively confirmed by a context-dependent, unless the validity is positively confirmed by a
contextual rule. To check this, each code-point marked as CONTEXTJ contextual rule. To check this, each code-point marked as CONTEXTJ
and CONTEXTO in [IDNA2008-Tables] MUST have a non-null rule. If such and CONTEXTO in [IDNA2008-Tables] MUST have a non-null rule. If such
a code-point is missing a rule, it is invalid. If the rule exists a code-point is missing a rule, it is invalid. If the rule exists
but the result of applying the rule is negative or inconclusive, the but the result of applying the rule is negative or inconclusive, the
proposed label is invalid. proposed label is invalid.
4.2.3.4. Labels Containing Characters Written Right to Left 4.2.3.4. Labels Containing Characters Written Right to Left
If the proposed label contains any characters that are written from If the proposed label contains any characters that are written from
right to left it MUST meet the "bidi" criteria [IDNA2008-BIDI]. right to left it MUST meet the BIDI criteria [IDNA2008-BIDI].
4.2.4. Registration Validation Summary 4.2.4. Registration Validation Summary
Strings that contain at least one non-ASCII character, have been Strings that contain at least one non-ASCII character, have been
produced by the steps above, whose contents pass all of the tests in produced by the steps above, whose contents pass all of the tests in
Section 4.2, and are 63 or fewer characters long in ACE form (see Section 4.2, and are 63 or fewer characters long in ACE form (see
Section 4.4), are U-labels. Section 4.4), are U-labels.
To summarize, tests are made in Section 4.2 for invalid characters, To summarize, tests are made in Section 4.2 for invalid characters,
invalid combinations of characters, for labels that are invalid even invalid combinations of characters, for labels that are invalid even
if the characters they contain are valid individually, and for labels if the characters they contain are valid individually, and for labels
that do not conform to the restrictions for strings containing right that do not conform to the restrictions for strings containing right
to left characters. to left characters.
4.3. Registry Restrictions 4.3. Registry Restrictions
In addition to the rules and tests above, there are many reasons why In addition to the rules and tests above, there are many reasons why
a registry could reject a label. Registries at all levels of the a registry could reject a label. Registries at all levels of the
DNS, not just the top level, establish policies about label DNS, not just the top level, are expected to establish policies about
registrations. Policies are likely to be informed by the local label registrations. Policies are likely to be informed by the local
languages and may depend on many factors including what characters languages and may depend on many factors including what characters
are in the label (for example, a label may be rejected based on other are in the label (for example, a label may be rejected based on other
labels already registered). See [IDNA2008-Rationale] for a labels already registered). See [IDNA2008-Rationale] for a
discussion and recommendations about registry policies. discussion and recommendations about registry policies.
The string produced by the steps in Section 4.2 is checked and The string produced by the steps in Section 4.2 is checked and
processed as appropriate to local registry restrictions. Application processed as appropriate to local registry restrictions. Application
of those registry restrictions may result in the rejection of some of those registry restrictions may result in the rejection of some
labels or the application of special restrictions to others. labels or the application of special restrictions to others.
4.4. Punycode Conversion 4.4. Punycode Conversion
The resulting U-label is converted to an A-label (defined in The resulting U-label is converted to an A-label (defined in
[IDNA2008-Defs] [[anchor13: Insert section number]]). The A-label is [IDNA2008-Defs] [[anchor12: ?? Insert section number]]). The
the encoding of the U-label according to the Punycode algorithm A-label is the encoding of the U-label according to the Punycode
[RFC3492] with the ACE prefix "xn--" added at the beginning of the algorithm [RFC3492] with the ACE prefix "xn--" added at the beginning
string. The resulting string must, of course, conform to the length of the string. The resulting string must, of course, conform to the
limits imposed by the DNS. This document updates RFC 3492 only to length limits imposed by the DNS. This document updates RFC 3492
the extent of replacing the reference to the discussion of the ACE only to the extent of replacing the reference to the discussion of
prefix. The ACE prefix is now specified in this document rather than the ACE prefix. The ACE prefix is now specified in this document
as part of RFC 3490 or Nameprep [RFC3491] but is the same in both rather than as part of RFC 3490 or Nameprep [RFC3491] but is the same
sets of documents. in both sets of documents.
The failure conditions identified in the Punycode encoding procedure The failure conditions identified in the Punycode encoding procedure
cannot occur if the input is a U-label as determined by the steps cannot occur if the input is a U-label as determined by the steps
above. above.
4.5. Insertion in the Zone 4.5. Insertion in the Zone
The A-label is registered in the DNS by insertion into a zone. The A-label is registered in the DNS by insertion into a zone.
5. Domain Name Lookup Protocol 5. Domain Name Lookup Protocol
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involving the user may read the string from a file or obtain it in 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 some other way. Processing in this step and the next two are local
matters, to be accomplished prior to actual invocation of IDNA. matters, to be accomplished prior to actual invocation of IDNA.
5.2. Conversion to Unicode 5.2. Conversion to Unicode
The string is converted from the local character set into Unicode, if The string is converted from the local character set into Unicode, if
it is not already Unicode. Depending on local needs, this conversion it is not already Unicode. Depending on local needs, this conversion
may involve mapping some characters into other characters as well as may involve mapping some characters into other characters as well as
coding conversions. Those issues are discussed in [IDNA2008-Mapping] coding conversions. Those issues are discussed in [IDNA2008-Mapping]
and the mapping-related sections of [IDNA2008-Rationale]. [[anchor14: and the mapping-related sections of [IDNA2008-Rationale].[[anchor13:
Supply section number.]] A Unicode string may require normalization ?? Supply section number.]] A Unicode string may require
as discussed in Section 4.1. The result MUST be a Unicode string in normalization as discussed in Section 4.1. The result MUST be a
NFC form. Unicode string in NFC form.
5.3. A-label Input 5.3. A-label Input
If the input to this procedure appears to be an A-label (i.e., it If the input to this procedure appears to be an A-label (i.e., it
starts in "xn--"), the lookup application MAY attempt to convert it starts in "xn--"), the lookup application MAY attempt to convert it
to a U-label and apply the tests of Section 5.4 and the conversion of to a U-label, first ensuring that the A-label is entirely in lower
case, and apply the tests of Section 5.4 and the conversion of
Section 5.5 to that form. If the label is converted to Unicode Section 5.5 to that form. If the label is converted to Unicode
(i.e., to U-label form) using the Punycode decoding algorithm, then (i.e., to U-label form) using the Punycode decoding algorithm, then
the processing specified in those two sections MUST be performed, and the processing specified in those two sections MUST be performed, and
the label MUST be rejected if the resulting label is not identical to the label MUST be rejected if the resulting label is not identical to
the original. See the Name Server Considerations section of the original. See the Name Server Considerations section of
[IDNA2008-Rationale] for additional discussion on this topic. [IDNA2008-Rationale] for additional discussion on this topic.
That conversion and testing SHOULD be performed if the domain name That conversion and testing SHOULD be performed if the domain name
will later be presented to the user in native character form (this will later be presented to the user in native character form (this
requires that the lookup application be IDNA-aware). If those steps requires that the lookup application be IDNA-aware). If those steps
skipping to change at page 11, line 49 skipping to change at page 12, line 13
information to users. information to users.
5.4. Validation and Character List Testing 5.4. Validation and Character List Testing
As with the registration procedure described in Section 4, the As with the registration procedure described in Section 4, the
Unicode string is checked to verify that all characters that appear Unicode string is checked to verify that all characters that appear
in it are valid as input to IDNA lookup processing. As discussed in it are valid as input to IDNA lookup processing. As discussed
above and in [IDNA2008-Rationale], the lookup check is more liberal above and in [IDNA2008-Rationale], the lookup check is more liberal
than the registration one. Labels that have not been fully evaluated than the registration one. Labels that have not been fully evaluated
for conformance to the applicable rules are referred to as "putative" for conformance to the applicable rules are referred to as "putative"
labels as discussed in [IDNA2008-Defs][[anchor15: ??? Insert section labels as discussed in [IDNA2008-Defs][[anchor14: ??? Insert section
number -- 2.2.3 as of Defs-09]]. Putative labels with any of the number -- 2.2.3 as of Defs-09]]. Putative labels with any of the
following characteristics MUST BE rejected prior to DNS lookup: following characteristics MUST be rejected prior to DNS lookup:
o Labels containing code points that are unassigned in the version o Labels containing code points that are unassigned in the version
of Unicode being used by the application, i.e.,in the UNASSIGNED of Unicode being used by the application, i.e.,in the UNASSIGNED
category of [IDNA2008-Tables]. category of [IDNA2008-Tables].
o Labels that are not in NFC form as defined in [Unicode-UAX15]. o Labels that are not in NFC form as defined in [Unicode-UAX15].
o Labels containing "--" (two consecutive hyphens) in the third and o Labels containing "--" (two consecutive hyphens) in the third and
fourth character positions. fourth character positions.
o Labels containing prohibited code points, i.e., those that are o Labels containing prohibited code points, i.e., those that are
assigned to the "DISALLOWED" category in the permitted character assigned to the "DISALLOWED" category in the permitted character
table [IDNA2008-Tables]. table [IDNA2008-Tables].
o Labels containing code points that are identified in o Labels containing code points that are identified in
[IDNA2008-Tables] as "CONTEXTJ", i.e., requiring exceptional [IDNA2008-Tables] as "CONTEXTJ", i.e., requiring exceptional
contextual rule processing on lookup, but that do not conform to contextual rule processing on lookup, but that do not conform to
that rule. Note that this implies that a rule must be defined, those rules. Note that this implies that a rule must be defined,
not null: a character that requires a contextual rule but for not null: a character that requires a contextual rule but for
which the rule is null is treated in this step as having failed to which the rule is null is treated in this step as having failed to
conform to the rule. conform to the rule.
o Labels containing code points that are identified in o Labels containing code points that are identified in
[IDNA2008-Tables] as "CONTEXTO", but for which no such rule [IDNA2008-Tables] as "CONTEXTO", but for which no such rule
appears in the table of rules. Applications resolving DNS names appears in the table of rules. Applications resolving DNS names
or carrying out equivalent operations are not required to test or carrying out equivalent operations are not required to test
contextual rules for "CONTEXTO" characters, only to verify that a contextual rules for "CONTEXTO" characters, only to verify that a
rule is defined (although they MAY make such tests to provide rule is defined (although they MAY make such tests to provide
skipping to change at page 13, line 25 skipping to change at page 13, line 36
5.5. Punycode Conversion 5.5. Punycode Conversion
The string that has now been validated for lookup is converted to ACE The string that has now been validated for lookup is converted to ACE
form using the Punycode algorithm (with the ACE prefix added). With form using the Punycode algorithm (with the ACE prefix added). With
the understanding that this summary is not normative (the steps above the understanding that this summary is not normative (the steps above
are), the string is either are), the string is either
o in Unicode NFC form that contains no leading combining marks, o in Unicode NFC form that contains no leading combining marks,
contains no DISALLOWED or UNASSIGNED code points, has rules contains no DISALLOWED or UNASSIGNED code points, has rules
associated with any code points in CONTEXTJ or CONTEXTO, and, for associated with any code points in CONTEXTJ or CONTEXTO, and, for
those in CONTEXTJ, to satisfies the conditions of the rules; or those in CONTEXTJ, to satisfy the conditions of the rules; or
o in A-label form, was supplied under circumstances in which the o in A-label form, was supplied under circumstances in which the
U-label conversions and tests have not been performed (see U-label conversions and tests have not been performed (see
Section 5.3). Section 5.3).
5.6. DNS Name Resolution 5.6. DNS Name Resolution
That resulting validated string is looked up in the DNS, using normal That resulting validated string is looked up in the DNS, using normal
DNS resolver procedures. That lookup can obviously either succeed DNS resolver procedures. That lookup can obviously either succeed
(returning information) or fail. (returning information) or fail.
skipping to change at page 14, line 14 skipping to change at page 14, line 24
8. Contributors 8. Contributors
While the listed editor held the pen, the original versions of this While the listed editor held the pen, the original versions of this
document represent the joint work and conclusions of an ad hoc design document represent the joint work and conclusions of an ad hoc design
team consisting of the editor and, in alphabetic order, Harald team consisting of the editor and, in alphabetic order, Harald
Alvestrand, Tina Dam, Patrik Faltstrom, and Cary Karp. This document Alvestrand, Tina Dam, Patrik Faltstrom, and Cary Karp. This document
draws significantly on the original version of IDNA [RFC3490] both draws significantly on the original version of IDNA [RFC3490] both
conceptually and for specific text. This second-generation version conceptually and for specific text. This second-generation version
would not have been possible without the work that went into that would not have been possible without the work that went into that
first version and its authors, Patrik Faltstrom, Paul Hoffman, and first version and especially the contributions of its authors Patrik
Adam Costello. While Faltstrom was actively involved in the creation Faltstrom, Paul Hoffman, and Adam Costello. While Faltstrom was
of this version, Hoffman and Costello were not and should not be held actively involved in the creation of this version, Hoffman and
responsible for any errors or omissions. Costello were not and should not be held responsible for any errors
or omissions.
9. Acknowledgments 9. Acknowledgments
This revision to IDNA would have been impossible without the This revision to IDNA would have been impossible without the
accumulated experience since RFC 3490 was published and resulting accumulated experience since RFC 3490 was published and resulting
comments and complaints of many people in the IETF, ICANN, and other comments and complaints of many people in the IETF, ICANN, and other
communities, too many people to list here. Nor would it have been communities, too many people to list here. Nor would it have been
possible without RFC 3490 itself and the efforts of the Working Group possible without RFC 3490 itself and the efforts of the Working Group
that defined it. Those people whose contributions are acknowledged that defined it. Those people whose contributions are acknowledged
in RFC 3490, [RFC4690], and [IDNA2008-Rationale] were particularly in RFC 3490, [RFC4690], and [IDNA2008-Rationale] were particularly
important. important.
Specific textual changes were incorporated into this document after Specific textual changes were incorporated into this document after
suggestions from the other contributors, Stephane Bortzmeyer, Vint suggestions from the other contributors, Stephane Bortzmeyer, Vint
Cerf, Lisa Dusseault, Mark Davis, Paul Hoffman, Kent Karlsson, Erik Cerf, Lisa Dusseault, Paul Hoffman, Kent Karlsson, James Mitchell,
van der Poel, Marcos Sanz, Andrew Sullivan, Wil Tan, Ken Whistler, Erik van der Poel, Marcos Sanz, Andrew Sullivan, Wil Tan, Ken
and other WG participants. As is usual with IETF specifications, Whistler, Chris Wright, and other WG participants. Special thanks
while the document represents rough consensus, it should not be are due to Paul Hoffman for permission to extract material from his
assumed that all participants and contributors agree with all Internet-Draft to form the basis for Appendix A.
provisions. Special thanks are due to Paul Hoffman for permission to
extract material from his Internet-Draft to form the basis for
Appendix A.
10. References 10. References
10.1. Normative References 10.1. Normative References
[IDNA2008-BIDI] [IDNA2008-BIDI]
Alvestrand, H. and C. Karp, "An updated IDNA criterion for Alvestrand, H. and C. Karp, "An updated IDNA criterion for
right-to-left scripts", August 2009, <https:// right-to-left scripts", August 2009, <https://
datatracker.ietf.org/drafts/draft-ietf-idnabis-bidi/>. datatracker.ietf.org/drafts/draft-ietf-idnabis-bidi/>.
skipping to change at page 15, line 16 skipping to change at page 15, line 27
August 2009, <https://datatracker.ietf.org/drafts/ August 2009, <https://datatracker.ietf.org/drafts/
draft-ietf-idnabis-defs/>. draft-ietf-idnabis-defs/>.
[IDNA2008-Tables] [IDNA2008-Tables]
Faltstrom, P., "The Unicode Codepoints and IDNA", Faltstrom, P., "The Unicode Codepoints and IDNA",
August 2009, <https://datatracker.ietf.org/drafts/ August 2009, <https://datatracker.ietf.org/drafts/
draft-ietf-idnabis-tables/>. draft-ietf-idnabis-tables/>.
A version of this document is available in HTML format at A version of this document is available in HTML format at
http://stupid.domain.name/idnabis/ http://stupid.domain.name/idnabis/
draft-ietf-idnabis-tables-02.html draft-ietf-idnabis-tables-06.html
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities", [RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, November 1987. STD 13, RFC 1034, November 1987.
[RFC1035] Mockapetris, P., "Domain names - implementation and [RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987. specification", STD 13, RFC 1035, November 1987.
[RFC1123] Braden, R., "Requirements for Internet Hosts - Application [RFC1123] Braden, R., "Requirements for Internet Hosts - Application
and Support", STD 3, RFC 1123, October 1989. and Support", STD 3, RFC 1123, October 1989.
skipping to change at page 16, line 22 skipping to change at page 16, line 32
ANSI X3.4-1968 has been replaced by newer versions with ANSI X3.4-1968 has been replaced by newer versions with
slight modifications, but the 1968 version remains slight modifications, but the 1968 version remains
definitive for the Internet. definitive for the Internet.
[IDNA2008-Mapping] [IDNA2008-Mapping]
Resnick, P., "Mapping Characters in IDNA", August 2009, <h Resnick, P., "Mapping Characters in IDNA", August 2009, <h
ttps://datatracker.ietf.org/drafts/ ttps://datatracker.ietf.org/drafts/
draft-ietf-idnabis-mapping/>. draft-ietf-idnabis-mapping/>.
[IDNA2008-Rationale] [IDNA2008-Rationale]
Klensin, J., Ed., "Internationalizing Domain Names for Klensin, J., Ed., "Internationalized Domain Names for
Applications (IDNA): Issues, Explanation, and Rationale", Applications (IDNA): Issues, Explanation, and Rationale",
February 2009, <https://datatracker.ietf.org/drafts/ February 2009, <https://datatracker.ietf.org/drafts/
draft-ietf-idnabis-rationale>. draft-ietf-idnabis-rationale>.
[RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound, [RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound,
"Dynamic Updates in the Domain Name System (DNS UPDATE)", "Dynamic Updates in the Domain Name System (DNS UPDATE)",
RFC 2136, April 1997. RFC 2136, April 1997.
[RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS
Specification", RFC 2181, July 1997. Specification", RFC 2181, July 1997.
skipping to change at page 18, line 13 skipping to change at page 18, line 24
contexts or as part of running text in paragraphs. contexts or as part of running text in paragraphs.
9. Remove the dot separator from the mandatory part of the 9. Remove the dot separator from the mandatory part of the
protocol. protocol.
10. Make some currently-valid labels that are not actually IDNA 10. Make some currently-valid labels that are not actually IDNA
labels invalid. labels invalid.
Appendix B. Change Log Appendix B. Change Log
[[anchor22: RFC Editor: Please remove this appendix.]] [[anchor21: RFC Editor: Please remove this appendix.]]
B.1. Changes between Version -00 and -01 of draft-ietf-idnabis-protocol B.1. Changes between Version -00 and -01 of draft-ietf-idnabis-protocol
o Corrected discussion of SRV records. o Corrected discussion of SRV records.
o Several small corrections for clarity. o Several small corrections for clarity.
o Inserted more "open issue" placeholders. o Inserted more "open issue" placeholders.
B.2. Version -02 B.2. Version -02
skipping to change at page 19, line 12 skipping to change at page 19, line 24
o "Editor" designation temporarily removed because the automatic o "Editor" designation temporarily removed because the automatic
posting machinery does not accept it. posting machinery does not accept it.
B.4. Version -04 B.4. Version -04
o Removed Contextual Rule appendices for transfer to Tables. o Removed Contextual Rule appendices for transfer to Tables.
o Several changes, including removal of discussion anchors, based on o Several changes, including removal of discussion anchors, based on
discussions at IETF 72 (Dublin) discussions at IETF 72 (Dublin)
o Rewrote the preprocessing material (former Section 5.3 -- see o Rewrote the preprocessing material (former Section 5.3) somewhat
Appendix B.14) somewhat. -- see Appendix B.14.
B.5. Version -05 B.5. Version -05
o Updated part of the A-label input explanation (Section 5.3) per o Updated part of the A-label input explanation (Section 5.3) per
note from Erik van der Poel. note from Erik van der Poel.
B.6. Version -06 B.6. Version -06
o Corrected a few typographical errors. o Corrected a few typographical errors.
skipping to change at page 20, line 49 skipping to change at page 21, line 19
o Added placeholder notes about several tasks, notably reorganizing o Added placeholder notes about several tasks, notably reorganizing
Section 4 and Section 5 so that subsection numbers are parallel. Section 4 and Section 5 so that subsection numbers are parallel.
o Cleaned up an incorrect use of the terms "A-label" and "U-label" o Cleaned up an incorrect use of the terms "A-label" and "U-label"
in the lookup phase that was spotted by Mark Davis. Inserted a in the lookup phase that was spotted by Mark Davis. Inserted a
note there about alternate ways to deal with the resulting note there about alternate ways to deal with the resulting
terminology problem. terminology problem.
o Added a temporarily appendix (above) to document alternate o Added a temporarily appendix (above) to document alternate
strategies for possible replacements for former section 5.3 (see strategies for possible replacements for the former Section 5.3
Appendix B.14. (see Appendix B.14).
B.11. Version -11 B.11. Version -11
o Removed dangling reference to "C-label" (editing error in prior o Removed dangling reference to "C-label" (editing error in prior
draft). draft).
o Recast the last steps of the Lookup description to eliminate o Recast the last steps of the Lookup description to eliminate
"apparent" (previously "putative") terminology. "apparent" (previously "putative") terminology.
o Rewrote major portions of the temporary appendix that describes o Rewrote major portions of the temporary appendix that describes
skipping to change at page 22, line 29 skipping to change at page 22, line 43
belongs in the Mapping document, the portion of Rationale that belongs in the Mapping document, the portion of Rationale that
supports it, or not at all. Section 5.2 has been rewritten supports it, or not at all. Section 5.2 has been rewritten
slightly to point to Mapping for those issues. slightly to point to Mapping for those issues.
o Note: With the revised mapping material inserted, I've just about o Note: With the revised mapping material inserted, I've just about
given up on the idea of having the subsections of Sections 4 and 5 given up on the idea of having the subsections of Sections 4 and 5
exactly parallel each other. Anyone who still feels strongly exactly parallel each other. Anyone who still feels strongly
about this should be prepared to make very specific suggestions. about this should be prepared to make very specific suggestions.
--JcK --JcK
B.15. Version -15
o Corrected name of protocol in the abstract ("Internationalization"
to "Internationalized") and a few other instances of that error.
o Corrected the hyphen test (Section 4.2.3.1).
o Added text to deal with the "upper case in A-labels" problem.
o Adjusted Acknowledgments to remove Mark Davis's name, per his
request and advice from IETF Trust Counsel.
o Incorporated other changes from WG Last Call.
o Small typographical and editorial corrections.
Author's Address Author's Address
John C Klensin John C Klensin
1770 Massachusetts Ave, Ste 322 1770 Massachusetts Ave, Ste 322
Cambridge, MA 02140 Cambridge, MA 02140
USA USA
Phone: +1 617 245 1457 Phone: +1 617 245 1457
Email: john+ietf@jck.com Email: john+ietf@jck.com
 End of changes. 38 change blocks. 
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