DNS Attrleaf Changes: Fixing Specifications That Use Underscored Node Names
RFC 8553

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Internet Engineering Task Force (IETF)                        D. Crocker
Request for Comments: 8553                   Brandenburg InternetWorking
BCP: 222                                                      March 2019
Updates: 2782, 3263, 3529, 3620, 3832,
         3887, 3958, 4120, 4227, 4386,
         4387, 4976, 5026, 5328, 5389,
         5415, 5518, 5555, 5617, 5679,
         5766, 5780, 5804, 5864, 5928,
         6120, 6186, 6376, 6733, 6763,
         7208, 7489, 8145
Category: Best Current Practice
ISSN: 2070-1721

                         DNS AttrLeaf Changes:
         Fixing Specifications That Use Underscored Node Names

Abstract

   Using an underscore for a prefix creates a space for constrained
   interoperation of resource records.  Original uses of an underscore
   character as a domain node name prefix were specified without the
   benefit of an IANA registry.  This produced an entirely uncoordinated
   set of name-creation activities, all drawing from the same namespace.
   A registry for these names has now been defined by RFC 8552.
   However, the existing specifications that use underscored naming need
   to be modified in order to be in line with the new registry.  This
   document specifies those changes.  The changes preserve existing
   software and operational practice, while adapting the specifications
   for those practices to the newer underscore registry model.

Status of This Memo

   This memo documents an Internet Best Current Practice.

   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
   BCPs 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/rfc8553.

Crocker                   Best Current Practice                 [Page 1]
RFC 8553                    DNS AttrLeaf Fix                  March 2019

Copyright Notice

   Copyright (c) 2019 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
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Underscored RRset Use in Specifications . . . . . . . . . . .   3
     2.1.  TXT RRset . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  SRV RRset . . . . . . . . . . . . . . . . . . . . . . . .   5
     2.3.  URI RRset . . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  Underscored Template Specifications . . . . . . . . . . . . .   7
     3.1.  SRV Specification Changes . . . . . . . . . . . . . . . .   7
     3.2.  URI Specification Changes . . . . . . . . . . . . . . . .   8
     3.3.  DNSSEC Signaling Specification Changes  . . . . . . . . .  10
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  12
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  15
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   Original uses of an underscore character as a domain node name
   [RFC1035] prefix, which creates a space for constrained
   interpretation of resource records, were specified without the
   benefit of an IANA registry [IANA-reg].  This produced an entirely
   uncoordinated set of name-creation activities, all drawing from the
   same namespace.  A registry has now been defined (see Section 4 of
   [RFC8552]); the RFC that defined it discusses the background for the
   use of underscored domain names [RFC8552].

Crocker                   Best Current Practice                 [Page 2]
RFC 8553                    DNS AttrLeaf Fix                  March 2019

   The basic model for underscored name registration, as specified in
   [RFC8552], is to have each registry entry be unique in terms of the
   combination of a resource record type and a "global" (highest-level)
   underscored node name; that is, the node name beginning with an