Internationalized Domain Names for Applications (IDNA) Review for New Unicode Versions
RFC 8753

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Internet Engineering Task Force (IETF)                        J. Klensin
Request for Comments: 8753                                              
Updates: 5892                                               P. Fältström
Category: Standards Track                                         Netnod
ISSN: 2070-1721                                               April 2020

 Internationalized Domain Names for Applications (IDNA) Review for New
                            Unicode Versions

Abstract

   The standards for Internationalized Domain Names in Applications
   (IDNA) require a review of each new version of Unicode to determine
   whether incompatibilities with prior versions or other issues exist
   and, where appropriate, to allow the IETF to decide on the trade-offs
   between compatibility with prior IDNA versions and compatibility with
   Unicode going forward.  That requirement, and its relationship to
   tables maintained by IANA, has caused significant confusion in the
   past.  This document makes adjustments to the review procedure based
   on experience and updates IDNA, specifically RFC 5892, to reflect
   those changes and to clarify the various relationships involved.  It
   also makes other minor adjustments to align that document with
   experience.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8753.

Copyright Notice

   Copyright (c) 2020 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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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction
   2.  Brief History of IDNA Versions, the Review Requirement, and RFC
           5982
   3.  The Review Model
     3.1.  Review Model Part I: Algorithmic Comparison
     3.2.  Review Model Part II: New Code Point Analysis
   4.  IDNA Assumptions and Current Practice
   5.  Derived Tables Published by IANA
   6.  Editorial Clarification to RFC 5892
   7.  IANA Considerations
   8.  Security Considerations
   9.  References
     9.1.  Normative References
     9.2.  Informative References
   Appendix A.  Summary of Changes to RFC 5892
   Appendix B.  Background and Rationale for Expert Review Procedure
           for New Code Point Analysis
   Acknowledgments
   Authors' Addresses

1.  Introduction

   The standards for Internationalized Domain Names in Applications
   (IDNA) require a review of each new version of Unicode to determine
   whether incompatibilities with prior versions or other issues exist
   and, where appropriate, to allow the IETF to decide on the trade-offs
   between compatibility with prior IDNA versions and compatibility with
   Unicode [Unicode] going forward.  That requirement, and its
   relationship to tables maintained by IANA, has caused significant
   confusion in the past (see Section 3 and Section 4 for additional
   discussion of the question of appropriate decisions and the history
   of these reviews).  This document makes adjustments to the review
   procedure based on nearly a decade of experience and updates IDNA,
   specifically the document that specifies the relationship between
   Unicode code points and IDNA derived properties [RFC5892], to reflect
   those changes and to clarify the various relationships involved.

   This specification does not change the requirement that registries at
   all levels of the DNS tree take responsibility for the labels they
   insert in the DNS, a level of responsibility that requires allowing
   only a subset of the code points and strings allowed by the IDNA
   protocol itself.  That requirement is discussed in more detail in a
   companion document [RegRestr].

   Terminology note: In this document, "IDNA" refers to the current
   version as described in RFC 5890 [RFC5890] and subsequent documents
   and sometimes known as "IDNA2008".  Distinctions between it and the
   earlier version are explicit only where they are necessary for
   understanding the relationships involved, e.g., in Section 2.