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DNAME Redirection in the DNS
RFC 6672

Internet Engineering Task Force (IETF)                           S. Rose
Request for Comments: 6672                                          NIST
Obsoletes: 2672                                            W. Wijngaards
Updates: 3363                                                 NLnet Labs
Category: Standards Track                                      June 2012
ISSN: 2070-1721

                      DNAME Redirection in the DNS

Abstract

   The DNAME record provides redirection for a subtree of the domain
   name tree in the DNS.  That is, all names that end with a particular
   suffix are redirected to another part of the DNS.  This document
   obsoletes the original specification in RFC 2672 as well as updates
   the document on representing IPv6 addresses in DNS (RFC 3363).

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 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6672.

Rose & Wijngaards            Standards Track                    [Page 1]
RFC 6672                    DNAME Redirection                  June 2012

Copyright Notice

   Copyright (c) 2012 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
   (http://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.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Rose & Wijngaards            Standards Track                    [Page 2]
RFC 6672                    DNAME Redirection                  June 2012

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  4
   2.  The DNAME Resource Record  . . . . . . . . . . . . . . . . . .  5
     2.1.  Format . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.2.  The DNAME Substitution . . . . . . . . . . . . . . . . . .  5
     2.3.  DNAME Owner Name Matching the QNAME  . . . . . . . . . . .  6
     2.4.  Names next to and below a DNAME Record . . . . . . . . . .  7
     2.5.  Compression of the DNAME Record  . . . . . . . . . . . . .  7
   3.  Processing . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     3.1.  CNAME Synthesis  . . . . . . . . . . . . . . . . . . . . .  8
     3.2.  Server Algorithm . . . . . . . . . . . . . . . . . . . . .  9
     3.3.  Wildcards  . . . . . . . . . . . . . . . . . . . . . . . . 10
     3.4.  Acceptance and Intermediate Storage  . . . . . . . . . . . 11
       3.4.1.  Resolver Algorithm . . . . . . . . . . . . . . . . . . 11
   4.  DNAME Discussions in Other Documents . . . . . . . . . . . . . 12
   5.  Other Issues with DNAME  . . . . . . . . . . . . . . . . . . . 13
     5.1.  Canonical Hostnames Cannot Be below DNAME Owners . . . . . 13
     5.2.  Dynamic Update and DNAME . . . . . . . . . . . . . . . . . 13
     5.3.  DNSSEC and DNAME . . . . . . . . . . . . . . . . . . . . . 14
       5.3.1.  Signed DNAME, Unsigned Synthesized CNAME . . . . . . . 14
       5.3.2.  DNAME Bit in NSEC Type Map . . . . . . . . . . . . . . 14
       5.3.3.  DNAME Chains as Strong as the Weakest Link . . . . . . 14
       5.3.4.  Validators Must Understand DNAME . . . . . . . . . . . 14
         5.3.4.1.  Invalid Name Error Response Caused by DNAME in

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