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Internationalized Domain Names in Applications, Revised

Document Charter Internationalized Domain Names in Applications, Revised WG (idnabis)
Title Internationalized Domain Names in Applications, Revised
Last updated 2010-03-15
State Approved
WG State Concluded
IESG Responsible AD (None)
Charter edit AD (None)
Send notices to (None)

The original Internationalized Domain Name (IDN) WG specified rules for
  the use of characters other than Latin A(a)-Z(z), digits 0-9 and the
  hyphen (-) in domain names in RFC3490, RFC3491 and RFC3492 in 2002
  (published in 2003 and often referenced collectively as "IDNA2003").
  These documents depend on RFC 3454 and were tied to Unicode version 
  3.2. An update to the current version (5.x) is required to accommodate
  additional scripts.  In addition, experience has shown that significant
  improvements could be made in the protocol as presently specified.
  This WG is chartered to decouple IDNA from specific versions of Unicode
  using algorithms that define validity based on Unicode properties.  It
  is recognized that some explicit exceptions may be necessary in any
  case, but attempts will be made to minimize these exceptions.
  Additional goals:
    - Separate requirements for valid IDNs at registration time (insertion 
  of names into DNS zone files), vs. at resolution time (looking up those 
    - Review, and if necessary revise, the algorithms and rules for
  handling right to left character sequences in an IDN context to allow
  labels based on additional scripts and languages and to make presentation 
  as predictable as reasonably possible.
    - Permit use of some scripts that were inadvertently excluded by the
  original protocols.
    - Ensure practical stability of validity algorithms for IDNs.
  The constraints of the original IDN WG still apply to IDNABIS, namely 
  to avoid disturbing the current use and operation of the domain name
  system, and for the DNS to continue to allow any system to resolve any
  domain name in a consistent way. The client-based approach of the
  original IDN work will be maintained -- substantially new protocols or
  mechanisms are not in scope.  In particular, IDNs continue to use the
  "xn--" prefix and the same ASCII-compatible encoding, and the
  bidirectional algorithm follows the same basic design.
  The specifications are initially organized as four documents: overview
  and rationale, protocol, table algorithm, and improvements to the
  bidirectional algorithm. These documents are to be used as the basis 
  for the discussion of the general direction of the work.
  This working group will be providing extended public review of the
  output of a design team that has been working on improvement of the 
  IDNA specifications.
  This review-based approach is being used in part because of the way the
  work was undertaken by the team; in particular, the design team has 
  been working with IETF visibility and has solicited and received 
  significant amounts of technical review already from IETF participants 
  and from others including experts in the Unicode specifications and the 
  use of scripts in languages.  If the public review provided by this 
  Working Group confirms the basic method outlined in the input documents, 
  it is expected that the working group will be able to respond with any 
  needed changes and close in a short period of time.  If technical issues 
  arise that indicate a fundamentally different approach must be taken 
  from the one outlined above, it is anticipated that this working group 
  would close, and a new one with an appropriate charter would be 
  This work is intended to specify an improved means to produce and use
  stable and unambiguous IDN identifiers.
  There are a variety of generally unsolvable problems, notably the
  problem of characters that are confusingly similar in appearance (often
  known as the "phishing" problem) that are not specifically part of the
  scope of the WG although some of the preliminary results of the design
  team suggest that the improvements contemplated in the specifications
  might mitigate some of the ways in which the current IDNA specifications
  can be abused for phishing purposes.
  While it is referenced from the original IDNA2003 package, the original
  Stringprep specification, RFC 3454, is not formally part of the IDNA
  package and will not be altered by this work.
  The work will update or obsolete RFC 3490.  It is not expected to 
  continue to use Nameprep (RFC 3491).  Nameprep is used by other 
  specifications; determining how (or whether) to update those 
  specifications and, consequently, the long-term status of Nameprep, 
  are not part of this effort.  The method for ASCII-compatible ("ACE") 
  encoding of IDNs, "Punycode" (RFC 3492) will not be revised by this WG.
  Subject to the more general constraints described above, the WG is
  permitted to consider changes that are not strictly backwards-
  compatible.  For any such change that is recommended, it is expected to 
  document the reasons for the change, the characters affected, and 
  possible transition strategies.
  The assumptions outlined above are considered critical to the WG
  constituted by this charter.  The WG will stop work and recommend that 
  a new charter be generated if it concludes that any of the following are
  necessary to meet its goals:
    (i) A change to the "punycode" algorithm or to the ACE approach to
  encoding names  in the DNS.
    (ii) A change to the ACE prefix from "xn--"
    (iii) A change to the basic approach taken in the design team
  documents (Namely: independence from Unicode version and reduction of
  dependency on character mapping )