Scoped Interpretation of DNS Resource Records through "Underscored" Naming of Attribute Leaves
RFC 8552

Document Type RFC - Best Current Practice (March 2019; Errata)
Also known as BCP 222
Last updated 2019-03-22
Replaces draft-crocker-dns-attrleaf
Stream IETF
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Stream WG state Submitted to IESG for Publication
Document shepherd Benno Overeinder
Shepherd write-up Show (last changed 2018-07-21)
IESG IESG state RFC 8552 (Best Current Practice)
Consensus Boilerplate Yes
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Send notices to "Tim Wicinski" <tjw.ietf@gmail.com>, Benno Overeinder <benno@NLnetLabs.nl>
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Internet Engineering Task Force (IETF)                        D. Crocker
Request for Comments: 8552                   Brandenburg InternetWorking
BCP: 222                                                      March 2019
Category: Best Current Practice
ISSN: 2070-1721

         Scoped Interpretation of DNS Resource Records through
                "Underscored" Naming of Attribute Leaves

Abstract

   Formally, any DNS Resource Record (RR) may occur under any domain
   name.  However, some services use an operational convention for
   defining specific interpretations of an RRset by locating the records
   in a DNS branch under the parent domain to which the RRset actually
   applies.  The top of this subordinate branch is defined by a naming
   convention that uses a reserved node name, which begins with the
   underscore character (e.g., "_name").  The underscored naming
   construct defines a semantic scope for DNS record types that are
   associated with the parent domain above the underscored branch.  This
   specification explores the nature of this DNS usage and defines the
   "Underscored and Globally Scoped DNS Node Names" registry with IANA.
   The purpose of this registry is to avoid collisions resulting from
   the use of the same underscored name for different services.

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/rfc8552.

Crocker                   Best Current Practice                 [Page 1]
RFC 8552                      DNS AttrLeaf                    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
     1.1.  Underscore-Based Scoping  . . . . . . . . . . . . . . . .   3
     1.2.  Scaling Benefits  . . . . . . . . . . . . . . . . . . . .   4
     1.3.  Global Underscored Node Names . . . . . . . . . . . . . .   4
     1.4.  Interaction with DNS Wildcards  . . . . . . . . . . . . .   5
     1.5.  History . . . . . . . . . . . . . . . . . . . . . . . . .   5
   2.  "Underscored and Globally Scoped DNS Node Names" Registry . .   6
   3.  Guidance for Registering RRset Use  . . . . . . . . . . . . .   7
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
     4.1.  "Underscored and Globally Scoped DNS Node Names" Registry   8
     4.2.  Enumservices Registrations Registry . . . . . . . . . . .  11
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  12
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  15
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  15
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   The core Domain Name System (DNS) technical specifications ([RFC1035]
   and [RFC2181]) assign no semantics to domain names or their parts,
   and no constraints upon which resource record (RR) types are
   permitted to be stored under particular names [RFC1035] [RFC2181].
   Over time, some leaf node names, such as "www" and "ftp", have come
   to imply support for particular services, but this is a matter of
   operational convention rather than defined protocol semantics.  This
   freedom in the basic technology has permitted a wide range of
   administrative and semantic policies to be used -- in parallel.  DNS
   data semantics have been limited to the specification of particular
   resource record types on the expectation that new resource record

Crocker                   Best Current Practice                 [Page 2]
RFC 8552                      DNS AttrLeaf                    March 2019

   types would be added as needed.  Unfortunately, the addition of new
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