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+Network Working Group M. Duerst
+Internet-Draft W3C/Keio University
+Expires: December 30, 2002 July 1, 2002
+
+
+ Internationalized Domain Names in URIs
+ draft-ietf-idn-uri-02
+
+Status of this Memo
+
+ This document is an Internet-Draft and is in full conformance with
+ all provisions of Section 10 of RFC2026.
+
+ Internet-Drafts are working documents of the Internet Engineering
+ Task Force (IETF), its areas, and its working groups. Note that
+ other groups may also distribute working documents as Internet-
+ Drafts.
+
+ Internet-Drafts are draft documents valid for a maximum of six months
+ and may be updated, replaced, or 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 http://
+ www.ietf.org/ietf/1id-abstracts.txt.
+
+ The list of Internet-Draft Shadow Directories can be accessed at
+ http://www.ietf.org/shadow.html.
+
+ This Internet-Draft will expire on December 30, 2002.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2002). All Rights Reserved.
+
+Abstract
+
+ This document proposes to upgrade the definition of URIs (RFC 2396)
+ [RFC2396] to work consistently with internationalized domain names.
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+Duerst Expires December 30, 2002 [Page 1]
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+Internet-Draft IDNs in URIs July 2002
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+Table of Contents
+
+ 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
+ 2. URI syntax changes . . . . . . . . . . . . . . . . . . . . . . 3
+ 3. Security considerations . . . . . . . . . . . . . . . . . . . 5
+ 4. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 5
+ 4.1 Changes from draft-ietf-idn-uri--01 to draft-ietf-idn-uri-02 . 5
+ 4.2 Changes from draft-ietf-idn-uri--00 to draft-ietf-idn-uri-01 . 5
+ References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
+ Author's Address . . . . . . . . . . . . . . . . . . . . . . . 7
+ Full Copyright Statement . . . . . . . . . . . . . . . . . . . 8
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+1. Introduction
+
+ Internet domain names serve to identify hosts and services on the
+ Internet in a convenient way. The IETF IDN working group [IDNWG] has
+ been working on extending the character repertoire usable in domain
+ names beyond a subset of US-ASCII.
+
+ One of the most important places where domain names appear are
+ Uniform Resource Identifiers (URIs, [RFC2396], as modified by
+ [RFC2732]). However, in the current definition of the generic URI
+ syntax, the restrictions on domain names are 'hard-coded'. In
+ Section 2, this document relaxes these restrictions by updating the
+ syntax, and defines how internationalized domain names are encoded in
+ URIs.
+
+ The syntax in this document has been choosen to further increase the
+ uniformity of URI syntax, which is a very important principle of
+ URIs.
+
+ In practice, escaped domanin names should be used as rarely as
+ possible. Wherever possible, the actual characters in
+ Internationalized Domain Names should be preserved as long as
+ possible by using IRIs [IRI] rather than URIs, and only converting to
+ URIs and then to ACE-encoded [IDNA] domain names (or ideally directly
+ to ACE-encoding without even using URIs) when resolving the IRI.
+ Also, this document does in no way exclude the use of ACE encoding
+ directly in an URI domain name part. ACE encoding may be used
+ directly in an URI domain name part if this is considered necessary
+ for interoperability.
+
+ Please note that even with the definition of URIs in [RFC2396], some
+ URIs can already contain host names with escaped characters. For
+ example, mailto:example@w%33.org is legal per [RFC2396] because the
+ mailto: URI scheme does not follow the generic syntax of [RFC2396].
+
+2. URI syntax changes
+
+ The syntax of URIs [RFC2396] currently contains the following rules
+ relevant to domain names:
+
+ hostname = *( domainlabel "." ) toplabel [ "." ]
+ domainlabel = alphanum | alphanum *( alphanum | "-" ) alphanum
+ toplabel = alpha | alpha *( alphanum | "-" ) alphanum
+
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+ The later two rules are changed as follows:
+
+ domainlabel = anchar | anchar *( anchar | "-" ) anchar
+ toplabel = achar | achar *( anchar | "-" ) anchar
+
+ and the following rules are added:
+
+ anchar = alphanum | escaped
+ achar = alpha | escaped
+
+ Characters outside the repertoire (alphanum) are encoded by first
+ encoding the characters in UTF-8 [RFC 2279], resulting in a sequence
+ of octets, and then escaping these octets according to the rules
+ defined in [RFC2396].
+
+ Using UTF-8 assures that this encoding interoperates with IRIs [IRI].
+ It is also aligned with the recommendations in [RFC2277] and
+ [RFC2718], and is consistent with the URN syntax [RFC2141] as well as
+ recent URL scheme definitions that define encodings of non-ASCII
+ characters based on UTF-8 (e.g., IMAP URLs [RFC2192] and POP URLs
+ [RFC2384]).
+
+ The above syntax rules permit for domain names that are neither
+ permitted as US-ASCII only domain names nor as internationalized
+ domain names. However, such syntax should never be used, and will
+ always be rejected by resolvers. For US-ASCII only domain names, the
+ syntax rules in [RFC2396] are relevant. For example, http://
+ www.w%33.org is legal, because the corresponding 'w3' is a legal
+ 'domainlabel' according to [RFC2396]. However, http://
+ %2a.example.org is illegal because the corresponding '*' is not a
+ legal 'domainlabel' according to [RFC2396]. For domain names
+ containing non-ASCII characters, the legal domain names are those for
+ which the ToASCII operation ([IDNA], [Nameprep]; using the unescaped
+ UTF-8 values as input) is successful.
+
+ For consistency in comparison operations and for interoperability
+ with older software, the following should be noted: 1) US-ASCII
+ characters in domain names should not be escaped. 2) Because of the
+ principle of syntax uniformity for URIs, it is always more prudent to
+ take into account the possibility that US-ASCII characters are
+ escaped.
+
+ The work of the IDN WG includes some procedures for name preparation
+ [Nameprep]. Before encoding an internationalized domain name in an
+ URI, this preparation step SHOULD be applied. However, the URI
+ resolver MUST also apply any steps required as part of domain name
+ resolution by [IDNA].
+
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+3. Security considerations
+
+ The security considerations of [RFC2396] and those applying to
+ internationalized domain names apply. There may be an increased
+ potential to smuggle escaped US-ASCII-based domain names across
+ firewalls, although because of the uniform syntax principle for URIs,
+ such a potential is already existing.
+
+4. Change Log
+
+4.1 Changes from draft-ietf-idn-uri--01 to draft-ietf-idn-uri-02
+
+ Moved change log to back
+
+ Changed to only change URIs; IRI syntax updated directly in IRI
+ draft.
+
+ Removed syntax restriction on %hh in the US-ASCII part, but made
+ clear that restrictions to domain names apply.
+
+ Made clear that escaped domain names in URIs should only be an
+ intermediate representation.
+
+ Gave example of mailto: as already allowing escaped host names.
+
+4.2 Changes from draft-ietf-idn-uri--00 to draft-ietf-idn-uri-01
+
+ Changed requirement for URI/IRI resolvers from MUST to SHOULD
+
+ Changed IRI syntax slightly (ichar -> idchar, based on changes in
+ [IRI])
+
+ Various wording changes
+
+References
+
+ [IDNA] Faltstrom, P., Hoffman, P. and A. Costello,
+ "Internationalizing Domain Names in Applications (IDNA)",
+ draft-ietf-idn-idna-09.txt (work in progress), May 2002,
+ <http://www.ietf.org/internet-drafts/draft-ietf-idn-idna-
+ 09.txt>.
+
+ [IDNWG] "IETF Internationalized Domain Name (idn) Working Group".
+
+ [IRI] Duerst, M. and M. Suignard, "Internationalized Resource
+ Identifiers (IRI)", draft-duerst-iri-01 (work in
+ progress), July 2002.
+
+
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+ [ISO10646] International Organization for Standardization,
+ "Information Technology - Universal Multiple-Octet Coded
+ Character Set (UCS) - Part 1: Architecture and Basic
+ Multilingual Plane", ISO Standard 10646-1, October 2000.
+
+ [Nameprep] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep
+ Profile for Internationalized Domain Names", draft-ietf-
+ idn-nameprep-10.txt (work in progress), May 2002, <http:/
+ /www.ietf.org/internet-drafts/draft-ietf-idn-nameprep-
+ 10.txt>.
+
+ [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC2141] Moats, R., "URN Syntax", RFC 2141, May 1997.
+
+ [RFC2192] Newman, C., "IMAP URL Scheme", RFC 2192, September 1997.
+
+ [RFC2277] Alvestrand, H., "IETF Policy on Character Sets and
+ Languages", BCP 18, RFC 2277, January 1998.
+
+ [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO
+ 10646", RFC 2279, January 1998.
+
+ [RFC2384] Gellens, R., "POP URL Scheme", RFC 2384, August 1998.
+
+ [RFC2396] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
+ Resource Identifiers (URI): Generic Syntax", RFC 2396,
+ August 1998.
+
+ [RFC2640] Curtin, B., "Internationalization of the File Transfer
+ Protocol", RFC 2640, July 1999.
+
+ [RFC2718] Masinter, L., Alvestrand, H., Zigmond, D. and R. Petke,
+ "Guidelines for new URL Schemes", RFC 2718, November
+ 1999.
+
+ [RFC2732] Hinden, R., Carpenter, B. and L. Masinter, "Format for
+ Literal IPv6 Addresses in URL's", RFC 2732, December
+ 1999.
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+Author's Address
+
+ Martin Duerst
+ W3C/Keio University
+ 5322 Endo
+ Fujisawa 252-8520
+ Japan
+
+ Phone: +81 466 49 1170
+ Fax: +81 466 49 1171
+ EMail: duerst@w3.org
+ URI: http://www.w3.org/People/D%C3%BCrst/
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+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2002). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
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projects / thirdparty / bind9.git / commitdiff
