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Preparation and Comparison of Internationalized Strings

Document Charter Preparation and Comparison of Internationalized Strings WG (precis)
Title Preparation and Comparison of Internationalized Strings
Last updated 2010-06-11
State Approved
WG State Concluded
IESG Responsible AD Alexey Melnikov
Charter edit AD (None)
Send notices to (None)


Problem Statement

The use of non-ASCII strings in Internet protocols requires additional
processing to be handled properly. As part of the Internationalized
Domain Names (idn) work in 2003, a method for preparation and comparison
of internationalized strings was defined and generalized to be re-used
by other protocols. This "stringprep" method [RFC 3454] defines the
overall framework whereas specific protocols define their own profiles.
Known existing IETF profiles are:

  • The Nameprep profile [RFC 3490] for use in Internationalized Domain
    Names in Applications (IDNA)
  • The iSCSI profile [RFC 3722] for use in Internet Small Computer
    Systems Interface (iSCSI) Names
  • The Nodeprep and Resourceprep profiles [RFC 3920] for use in the
    Extensible Messaging and Presence Protocol (XMPP)
  • The Policy MIB profile [RFC 4011] for use in the Simple Network
    Management Protocol (SNMP)
  • The SASLprep profile [RFC 4013] for use in the Simple Authentication
    and Security Layer (SASL)
  • The trace profile [RFC 4505] for use with the SASL ANONYMOUS mechanism
  • The LDAP profile (RFC 4518] for use with LDAP

The IAB completed a review of IDN and made recommendations for change
[RFC 4690], which triggered a new version of the IDNA protocol called
IDNA2008. Whereas IDNA2003 was tied to Unicode 3.2 via stringprep,
IDNA2008 does not use the stringprep method, but instead uses an
algorithm based on the properties of Unicode characters, which makes it
agile to the Unicode database version. The protocols using stringprep
need Unicode version agility and therefore need to investigate whether
and how to move away from the current stringprep approach, with the
associated challenges of backward compatibility and migration.


The goal of this group is to assess whether a new method based on the
new IDNA2008 algorithmic approach is the appropriate path forward for
existing stringprep protocols as well as for other application protocols
requiring internationalized strings.

The group will evaluate if a new generalized framework based on the
algorithmic approach is appropriate and, if so, define it.

The group will analyze existing stringprep profiles and will do one of
the following with regard to each profile:

  1. Develop a replacement for the profile in close collaboration with the
    related protocol working group (if any).

  2. Collaborate with another active working group which will be
    developing the new profile as part of its charter.

  3. Advise the authors of profiles for which there is no active working
    group how to proceed.

The group will also define a set of best current practices for
preparation and comparison of internationalized strings.

Because the framework, profile replacements, and guidelines are very
much interrelated, work on them will proceed in parallel as much as

Based on normal working group processes for achieving consensus, the
group will attempt to gather input from, and may provide advice to,
"customers" working on IETF technologies other than those listed above,
including but not limited to Network Address Identifiers (RFC 4282) and
Kerberos (RFC 4120). However, the group will prioritize work on the
listed stringprep profiles higher than work on other technologies, and
will formally accept additional tasks as official milestones only after

In completing its tasks, the working group should collaborate with other
teams involved in internationalized identifiers, such as the IETF's IRI
and EAI working groups as well as other relevant standards development
organizations (e.g., the Unicode Consortium).


  1. Problem statement / analysis of existing stringprep profiles

  2. Possible new framework to replace stringprep (Standards Track).

  3. Possible replacements for the existing IETF stringprep profiles as
    listed earlier in this charter (Standards Track).

  4. String preparation and comparison guidelines (BCP).