Nameprep: A Stringprep Profile for Internationalized Domain Names (IDN)
RFC 3491
Document | Type |
RFC - Proposed Standard
(March 2003; No errata)
Obsoleted by RFC 5891
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Authors | Paul Hoffman , Marc Blanchet | ||
Last updated | 2015-10-14 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Stream | WG state | WG Document | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 3491 (Proposed Standard) | |
Action Holders |
(None)
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Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Erik Nordmark | ||
IESG note |
Updated drafts are available. Need to be reviewed to see if the IESG comments have been addressed. |
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Send notices to | <jseng@pobox.org.sg> |
Network Working Group P. Hoffman Request for Comments: 3491 IMC & VPNC Category: Standards Track M. Blanchet Viagenie March 2003 Nameprep: A Stringprep Profile for Internationalized Domain Names (IDN) Status of this Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. Abstract This document describes how to prepare internationalized domain name (IDN) labels in order to increase the likelihood that name input and name comparison work in ways that make sense for typical users throughout the world. This profile of the stringprep protocol is used as part of a suite of on-the-wire protocols for internationalizing the Domain Name System (DNS). 1. Introduction This document specifies processing rules that will allow users to enter internationalized domain names (IDNs) into applications and have the highest chance of getting the content of the strings correct. It is a profile of stringprep [STRINGPREP]. These processing rules are only intended for internationalized domain names, not for arbitrary text. This profile defines the following, as required by [STRINGPREP]. - The intended applicability of the profile: internationalized domain names processed by IDNA. - The character repertoire that is the input and output to stringprep: Unicode 3.2, specified in section 2. Hoffman & Blanchet Standards Track [Page 1] RFC 3491 IDN Nameprep March 2003 - The mappings used: specified in section 3. - The Unicode normalization used: specified in section 4. - The characters that are prohibited as output: specified in section 5. - Bidirectional character handling: specified in section 6. 1.1 Interaction of protocol parts Nameprep is used by the IDNA [IDNA] protocol for preparing domain names; it is not designed for any other purpose. It is explicitly not designed for processing arbitrary free text and SHOULD NOT be used for that purpose. Nameprep is a profile of Stringprep [STRINGPREP]. Implementations of Nameprep MUST fully implement Stringprep. Nameprep is used to process domain name labels, not domain names. IDNA calls nameprep for each label in a domain name, not for the whole domain name. 1.2 Terminology The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY" in this document are to be interpreted as described in BCP 14, RFC 2119 [RFC2119]. 2. Character Repertoire This profile uses Unicode 3.2, as defined in [STRINGPREP] Appendix A. 3. Mapping This profile specifies mapping using the following tables from [STRINGPREP]: Table B.1 Table B.2 4. Normalization This profile specifies using Unicode normalization form KC, as described in [STRINGPREP]. Hoffman & Blanchet Standards Track [Page 2] RFC 3491 IDN Nameprep March 2003 5. Prohibited Output This profile specifies prohibiting using the following tables from [STRINGPREP]: Table C.1.2 Table C.2.2 Table C.3 Table C.4 Table C.5 Table C.6 Table C.7 Table C.8 Table C.9 IMPORTANT NOTE: This profile MUST be used with the IDNA protocol. The IDNA protocol has additional prohibitions that are checked outside of this profile. 6. Bidirectional characters This profile specifies checking bidirectional strings as described in [STRINGPREP] section 6. 7. Unassigned Code Points in Internationalized Domain Names If the processing in [IDNA] specifies that a list of unassigned code points be used, the system uses table A.1 from [STRINGPREP] as its list of unassigned code points. 8. References 8.1 Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [STRINGPREP] Hoffman, P. and M. Blanchet, "Preparation of Internationalized Strings ("stringprep")", RFC 3454, December 2002. [IDNA] Faltstrom, P., Hoffman, P. and A. Costello, "Internationalizing Domain Names in Applications (IDNA)", RFC 3490, March 2003. Hoffman & Blanchet Standards Track [Page 3]Show full document text