Network Working Group                                         J. Klensin
Internet-Draft                                         November 18, 2007
Obsoletes: 3490 (if approved)
Intended status: Standards Track
Expires: May 21, 2008

    Internationalizing Domain Names in Applications (IDNA): Protocol

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   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-

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

   The list of current Internet-Drafts can be accessed at

   The list of Internet-Draft Shadow Directories can be accessed at

   This Internet-Draft will expire on May 21, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2007).


   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.  This document specifies a standard method using
   characters outside the ASCII repertoire in domain names.  This
   document defines internationalized domain names (IDNs) and a

Klensin                   Expires May 21, 2008                  [Page 1]

Internet-Draft              IDNA200X Protocol              November 2007

   mechanism called Internationalizing Domain Names in Applications
   (IDNA) for handling them in a standard fashion.  IDNs use characters
   drawn from a large subset of the Unicode repertoire, but IDNA allows
   the non-ASCII characters to be represented using only the ASCII
   characters already allowed in so-called host names today.  This
   backward-compatible representation is required in existing protocols
   like DNS, so that IDNs can be introduced with no changes to the
   existing infrastructure.  IDNA is only meant for processing domain
   names, not free text.

Klensin                   Expires May 21, 2008                  [Page 2]

Internet-Draft              IDNA200X Protocol              November 2007

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  . . . . . . . . . . . . . . . . . .  6
     4.3.  Permitted Character Identification . . . . . . . . . . . .  6
     4.4.  Additional Character String Checking and Processing  . . .  7
     4.5.  Registry Restrictions  . . . . . . . . . . . . . . . . . .  8
     4.6.  Punycode Conversion  . . . . . . . . . . . . . . . . . . .  8
     4.7.  Insertion in the Zone  . . . . . . . . . . . . . . . . . .  8
   5.  Domain Name Resolution (Lookup) Protocol . . . . . . . . . . .  8
     5.1.  User input . . . . . . . . . . . . . . . . . . . . . . . .  8
     5.2.  Conversion to Unicode  . . . . . . . . . . . . . . . . . .  8
     5.3.  User Interface Character Changes . . . . . . . . . . . . .  9
     5.4.  Pre-Normalization Validation and Character List Testing  .  9
     5.5.  Normalization  . . . . . . . . . . . . . . . . . . . . . . 10
     5.6.  Post-Normalization Processing  . . . . . . . . . . . . . . 10
     5.7.  Punycode Conversion  . . . . . . . . . . . . . . . . . . . 10
     5.8.  DNS Name Resolution  . . . . . . . . . . . . . . . . . . . 10
   6.  Name server Considerations . . . . . . . . . . . . . . . . . . 10
     6.1.  Processing Non-ASCII Strings . . . . . . . . . . . . . . . 10
     6.2.  DNSSEC Authentication of IDN Domain Names  . . . . . . . . 11
     6.3.  Root Server Considerations . . . . . . . . . . . . . . . . 11
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   9.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 12
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 13
     11.2. Informative References . . . . . . . . . . . . . . . . . . 13
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 14
   Intellectual Property and Copyright Statements . . . . . . . . . . 16

Klensin                   Expires May 21, 2008                  [Page 3]

Internet-Draft              IDNA200X Protocol              November 2007

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-issues].

   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

   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-issues].

1.1.  Discussion Forum

   [[anchor3: RFC Editor: please remove this section.]]

   This work is being discussed on the mailing list

2.  Terminology

   General terminology applicable to IDNA, but with meanings familiar to
   those who have worked with Unicode or other character set standards
   and the DNS, appears in [IDNA200X-issues].  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.

   [[anchor4: May want to copy some definitions from "issues" back to
   here to avoid or reduce normative dependencies.  But, of course, that

Klensin                   Expires May 21, 2008                  [Page 4]

Internet-Draft              IDNA200X Protocol              November 2007

   would risk the two sets of definitions becoming inconsistent.

   The key words "MUST", "SHALL", "REQUIRED", "SHOULD", "RECOMMENDED",
   and "MAY" 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-issues]), it MUST contain only
       ASCII characters (i.e., must be either an A-label, an LDH-label,
       or a label associated with a DNS application that is not subject
       to IDNA.

   2.  Comparing two labels MUST be done on the A-label form, using an
       ASCII case-insensitive comparison, as with all comparisons of DNS

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; it depends entirely on the CLASS, and not on
   the TYPE.  This will remain true, even as new types 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.

Klensin                   Expires May 21, 2008                  [Page 5]

Internet-Draft              IDNA200X Protocol              November 2007

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 ( would be
   represented as  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
   that part of the SOA RDATA would require action in other standards,
   which could also specify IDNA interpretation of labels that follow
   the local part such as by permitting them to be A-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

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

4.2.  Conversion to Unicode

   Some system routine, or a localized front-end to the IDNA process,
   ensures that the proposed label is a Unicode string.  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.

4.3.  Permitted Character Identification

   The Unicode string is examined to prohibit characters that IDNA does
   not permit in input.  Those characters are identified in the "NEVER"
   list that is discussed in [IDNA200X-issues] which characters
   specified in [IDNA200X-Tables].  Characters that are specified as
   "NEVER" in those documents, and characters or sequences that are
   unassigned in Unicode, MUST NOT be part of labels being processed for

Klensin                   Expires May 21, 2008                  [Page 6]

Internet-Draft              IDNA200X Protocol              November 2007

   registration in the DNS.

4.4.  Additional Character String Checking and Processing

   All characters produced as output of the preceding step are then
   verified for permissibility by IDNA.  Conceptually, these tests are,
   in order:

   1.  Each code point is verified to be assigned in the version of
       Unicode in use (See [IDNA200X-issues]).  If verification fails,
       the proposed label containing the code point is not a U-label and
       MUST NOT be processed further.

   2.  Each code point is checked for its presence as "ALWAYS"
       (permitted) in the table of included characters for registration
       or, if appropriate for the specific registry, as "MAYBE"
       permitted (see [IDNA200X-Tables]).

   3.  Each code point is checked for its presence as "CONTEXTUAL RULE
       REQUIRED" in the table of included characters for registration.
       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.  If one is found, it is applied
       (typically as a test on the entire label or 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-issues]).

   4.  Additional special tests for right-to-left strings are applied
       (See [IDNA200X-BIDI].

   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 individual characters they contain are all valid.  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.  Additional transformations that do not occur as the
   result of the steps above may be specified at this point by IDNA200x.
   As the list of characters permitted to be registered expands, new
   rules, similar to those suggested for zero-width characters, may
   accompany them.

Klensin                   Expires May 21, 2008                  [Page 7]

Internet-Draft              IDNA200X Protocol              November 2007

4.5.  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.  As
   discussed in [IDNA200X-issues]), 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.

4.6.  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).

4.7.  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.  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
   facilitates expansion of the permitted character lists to include new
   scripts and accommodate new versions of Unicode.

5.1.  User 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.  Processing in this step and the next two
   are local matters, to be accomplished prior to actual invocation of
   IDNAbis, 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 above

Klensin                   Expires May 21, 2008                  [Page 8]

Internet-Draft              IDNA200X Protocol              November 2007

   (Section 4.2).

5.3.  User Interface Character Changes

   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 case-fold 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 to
   separate domain name components from each other, standardizing
   different "width" forms of the same character, or giving special
   treatment to characters whose presentation forms are dependent only
   on placement in the label.

   Because these transformations are local, it is important that domain
   names that might be passed between systems (e.g., in IRIs) be
   U-labels or A-labels and not forms that might be accepted locally as
   a consequence of this step.  This step is not standardized, and not
   specified further here.

5.4.  Pre-Normalization 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-issues], the
   resolution check is more liberal than that of the registration one.
   Characters that fall into the "MAYBE" (see [IDNA200X-issues])
   categories in the inclusion tables do not lead to label rejection on
   resolution.  Putative labels containing code points with any of the
   following characteristics MUST BE rejected prior to DNS lookup:

   o  Code points that are unassigned in the version of Unicode being
      used by the application, i.e., in the "Unassigned" Unicode

   o  Prohibited code points, i.e., those that are assigned to the
      "NEVER" category in the permitted character table.

   o  Code points that are shown in the permitted character table as
      requiring a contextual rule ("CONTEXTUAL RULE REQUIRED"), but for
      which no such rule appears in the table of rules.

   For all other strings, the resolver MUST rely on the presence or
   absence of labels in the DNS to determine the validity of those

Klensin                   Expires May 21, 2008                  [Page 9]

Internet-Draft              IDNA200X Protocol              November 2007

   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.

5.5.  Normalization

   The validated Unicode string is normalized (using NFC); no case-
   mapping is performed.

5.6.  Post-Normalization Processing

   Any necessary processing or filtering is applied to the normalized
   output string produced by the above.  In the cases that can be
   anticipated, this step will be null.  It is included in the model in
   case, e.g., full-label checks are needed on lookup.

5.7.  Punycode Conversion

   The validated string, a U-label, is converted to an A-label.

5.8.  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

   RFC2821 explicitly allows domain labels to contain octets beyond the
   ASCII range (0..7F), and this document does not change that.  Note,
   however, that there is no defined interpretation of octets 80..FF as
   characters.  If labels containing these octets are returned to

Klensin                   Expires May 21, 2008                 [Page 10]

Internet-Draft              IDNA200X Protocol              November 2007

   applications, unpredictable behavior could result.  The A-label form,
   which cannot contain those characters, is the only standard
   representation for internationalized labels in the current DNS

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-issues].  The comments below are specific to this protocol,
   but should be read in the context of that material and the
   specifications, identified there, on which this one depends.

   This memo describes an algorithm which encodes characters that are
   not valid according to the base DNS specifications (STD13 [RFC1034]
   [RFC1035] and Host Requirements [RFC1123]) into octet values that are

Klensin                   Expires May 21, 2008                 [Page 11]

Internet-Draft              IDNA200X Protocol              November 2007

   valid.  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

   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, the proper comparison reduces to the same case-
   insensitive ASCII comparison that has always been used for ASCII

   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

9.  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.

10.  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

Klensin                   Expires May 21, 2008                 [Page 12]

Internet-Draft              IDNA200X Protocol              November 2007

   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-issues] were particularly

11.  References

11.1.  Normative References

              Alvestrand, H. and C. Karp, "An IDNA problem in right-to-
              left scripts", July 2007, <

              Klensin, J., Ed., "Internationalizing Domain Names for
              Applications (IDNA): Issues and Rationale", November 2007.

   [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.

   [RFC3492]  Costello, A., "Punycode: A Bootstring encoding of Unicode
              for Internationalized Domain Names in Applications
              (IDNA)", RFC 3492, March 2003.

11.2.  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.

              Faltstrom, P., "The Unicode Codepoints and IDN",
              November 2007, <

Klensin                   Expires May 21, 2008                 [Page 13]

Internet-Draft              IDNA200X Protocol              November 2007


              A version of this document, is available in HTML format at

   [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
              5.0", 2007.

              Boston, MA, USA: Addison-Wesley.  ISBN 0-321-48091-0

Klensin                   Expires May 21, 2008                 [Page 14]

Internet-Draft              IDNA200X Protocol              November 2007

Author's Address

   John C Klensin
   1770 Massachusetts Ave, Ste 322
   Cambridge, MA  02140

   Phone: +1 617 245 1457

Klensin                   Expires May 21, 2008                 [Page 15]

Internet-Draft              IDNA200X Protocol              November 2007

Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an

Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at


   Funding for the RFC Editor function is provided by the IETF
   Administrative Support Activity (IASA).

Klensin                   Expires May 21, 2008                 [Page 16]