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Versions: 00

Network Working Group                                    M. Blanchet Ed.
Internet-Draft                                                  Viagenie
Intended status: Informational                             March 1, 2010
Expires: September 2, 2010


                       NewPrep Problem Statement
            draft-blanchet-newprep-problem-statement-00.txt

Abstract

   Using Unicode codepoints in protocol strings requires preparation of
   the string.  Internationalized Domain Names(idn) initial work defined
   and used Stringprep and Nameprep.  Other protocols have defined
   Stringprep profiles.  New approach different from Stringprep/Nameprep
   is used for a revision of IDN.  This document summarize the
   characteristics of both approach and provides guidance to protocol
   designers for handling internationalized strings.

Status of this Memo

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Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal



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   Provisions Relating to IETF Documents
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 4
   2.  Key Characteristics of Stringprep . . . . . . . . . . . . . . . 4
   3.  Key Characteristics of IDNAbis  . . . . . . . . . . . . . . . . 5
   4.  Protocols already using Stringprep  . . . . . . . . . . . . . . 5
   5.  Protocols looking for preparing internationalized strings . . . 5
   6.  Generalizing IDNAbis for other protocols  . . . . . . . . . . . 6
   7.  Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
   8.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   10. Discussion home for this draft  . . . . . . . . . . . . . . . . 6
   11. Informative References  . . . . . . . . . . . . . . . . . . . . 6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 7





































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1.  Introduction

   As part of the Internationalized Domain Names(idn) initial work
   [RFC3490][RFC3491][RFC3492], the unicode-based strings needed to be
   prepared and normalized to enable their use in the DNS with exact
   match mechanism.  The method, called Nameprep [RFC3491], was specific
   to idn, but was generalized as Stringprep [RFC3454], to help other
   protocols with similar needs, but with different constraints than
   idn.

   Strinprep defines a framework where protocols defines their
   Stringprep profiles.  Known IETF specifications using Strinprep are:
   o  The Nameprep profile[RFC3490] for use in Internationalized Domain
      Names (IDNs)
   o  The iSCSI profile [RFC3722] for use in Internet Small Computer
      Systems Interface (iSCSI) Names
   o  The Nodeprep and Resourceprep profiles [RFC3920] for use in the
      Extensible Messaging and Presence Protocol (XMPP)
   o  The Policy MIB profile [RFC4011] for use in the Simple Network
      Management Protocol (SNMP)
   o  The SASLprep profile [RFC4013] for use in the Simple
      Authentication and Security Layer (SASL)
   o  The trace profile [RFC4505] for use with the SASL ANONYMOUS
      mechanism
   o  The LDAP profile [RFC4518] for use with LDAP

   Based on findings [RFC4690] on early deployments of idn, IDNs
   specifications have been updated /* note to add ref to idnabis RFCs*/
   and do not use stringprep/nameprep anymore.  Instead, a complete
   table of the supported Unicode codepoints is defined.  This table is
   based on some properties of the codepoints as defined by Unicode and
   some specific exceptions.  It also defines an algorithm to update the
   table with new versions of the Unicode codepoints database.

   Do other protocols, either current users of Stringprep or other
   protocols, would benefit from the new approach for idns?  The aim of
   this document is to provide advice on the preparation of
   internationalized strings to protocol designers of current stringprep
   profiles as well as for new protocols.


2.  Key Characteristics of Stringprep

   Stringprep is used to prepare a string and output a string or an
   error.  The output string is normalized so that it could be compared
   with others in a protocol.  The functions and operations done by
   Stringprep are: mapping, normalization, prohibition and bidirectional
   string processing.  Many functions use or may use Unicode



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   specifications such as the normalization rules /* note to add ref to
   unicode normalization rules docs*/.

   Functions provided by Stringprep are typically needed for many
   network protocols that handles internationalized strings.

   Stringprep has the following key characteristics:
   o  Based on Unicode 3.2
   o  Defines a list of codepoints that are specially processed, such as
      removed
   o  Codepoints not specifically listed are only normalized by Unicode
      normalization rules


3.  Key Characteristics of IDNAbis

   IDNAbis method has the following key characteristics:
   o  Based on Unicode 5.2
   o  Each Unicode codepoint is tagged
   o  Basic table is created algorithmatically using some properties of
      the Unicode codepoint database.
   o  Some exceptions are specially handled
   o  An exception table(currently empty) is provisionned in case a
      future version of Unicode introduces a new character or a change
      in a character that creates a compatibility issue with previous
      tables.
   o  IANA registers the whole codepoint table for each Unicode database
      version.

   When Unicode releases a new version of the codepoint database, the
   table has to be regenerated and registered by IANA.  Exceptions may
   appear in the new table.  In this case, an expert will have to
   manually resolve the exceptions.


4.  Protocols already using Stringprep

   Possible options are:
   o  Leave it as is.
   o  Update Stringprep to new version of Unicode.  Update protocol
      profile to new version of Stringprep.
   o  Define a generalized version of IDNAbis for protocols.  Update
      protocol to use the new method.


5.  Protocols looking for preparing internationalized strings

   Possible options are:



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   o  Use Stringprep as is.  Define a profile for it
   o  Use IDNAbis.
   o  Define a generalized version of IDNAbis for protocols.  Define
      protocol to use the new method.


6.  Generalizing IDNAbis for other protocols

   A generalized version of IDNAbis to be used for other protocols might
   be interesting to do.  Similar to Stringprep but using the IDNAbis
   approach.


7.  Summary

   When this document matures enough, then appropriate summary and
   conclusions will be written...


8.  Security Considerations

   TBD


9.  IANA Considerations

   This document has no actions for IANA.


10.  Discussion home for this draft

   This document is intended to define the problem space discussed in
   the newprep@ietf.org mailing list.


11.  Informative References

   [RFC3454]  Hoffman, P. and M. Blanchet, "Preparation of
              Internationalized Strings ("stringprep")", RFC 3454,
              December 2002.

   [RFC3490]  Faltstrom, P., Hoffman, P., and A. Costello,
              "Internationalizing Domain Names in Applications (IDNA)",
              RFC 3490, March 2003.

   [RFC3491]  Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep
              Profile for Internationalized Domain Names (IDN)",
              RFC 3491, March 2003.



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

   [RFC3722]  Bakke, M., "String Profile for Internet Small Computer
              Systems Interface (iSCSI) Names", RFC 3722, April 2004.

   [RFC3920]  Saint-Andre, P., Ed., "Extensible Messaging and Presence
              Protocol (XMPP): Core", RFC 3920, October 2004.

   [RFC4011]  Waldbusser, S., Saperia, J., and T. Hongal, "Policy Based
              Management MIB", RFC 4011, March 2005.

   [RFC4013]  Zeilenga, K., "SASLprep: Stringprep Profile for User Names
              and Passwords", RFC 4013, February 2005.

   [RFC4505]  Zeilenga, K., "Anonymous Simple Authentication and
              Security Layer (SASL) Mechanism", RFC 4505, June 2006.

   [RFC4518]  Zeilenga, K., "Lightweight Directory Access Protocol
              (LDAP): Internationalized String Preparation", RFC 4518,
              June 2006.

   [RFC4690]  Klensin, J., Faltstrom, P., Karp, C., and IAB, "Review and
              Recommendations for Internationalized Domain Names
              (IDNs)", RFC 4690, September 2006.


Author's Address

   Marc Blanchet
   Viagenie
   2600 boul. Laurier, suite 625
   Quebec, QC  G1V 4W1
   Canada

   Email: Marc.Blanchet@viagenie.ca
   URI:   http://www.viagenie.ca













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