Moving A6 to Historic Status
RFC 6563

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Internet Engineering Task Force (IETF)                          S. Jiang
Request for Comments: 6563                  Huawei Technologies Co., Ltd
Category: Informational                                        D. Conrad
ISSN: 2070-1721                                         Cloudflare, Inc.
                                                            B. Carpenter
                                                       Univ. of Auckland
                                                              March 2012

                      Moving A6 to Historic Status

Abstract

   This document provides a summary of issues related to the use of A6
   records, discusses the current status, and moves RFC 2874 to Historic
   status, providing clarity to implementers and operators.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   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).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see 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/rfc6563.

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
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   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.

Jiang, et al.                 Informational                     [Page 1]
RFC 6563              Moving A6 to Historic Status            March 2012

Table of Contents

   1. Introduction and Background .....................................2
      1.1. Standards Action Taken .....................................3
   2. A6 Issues .......................................................3
      2.1. Resolution Latency .........................................3
      2.2. Resolution Failure .........................................3
      2.3. Cross Administrative Domains ...............................4
      2.4. Difficult Maintenance ......................................4
      2.5. Existence of Multiple RR Types for One Purpose is Harmful ..4
      2.6. Higher Security Risks ......................................4
   3. Current Usage of A6 .............................................5
      3.1. Reasons for Current A6 Usage ...............................5
   4. Moving A6 to Historic Status ....................................6
      4.1. Impact on Current A6 Usage .................................6
      4.2. Transition Phase for Current A6 Usage ......................6
   5. Security Considerations .........................................6
   6. IANA Considerations .............................................6
   7. Acknowledgments .................................................6
   8. References ......................................................7
      8.1. Normative References .......................................7
      8.2. Informative References .....................................7

1.  Introduction and Background

   The IETF began standardizing two different DNS protocol enhancements
   for IPv6 addresses in DNS records: AAAA was specified in 1995 as a
   Proposed Standard [RFC1886] and later in 2003 as a Draft Standard
   [RFC3596], and A6 appeared in 2000 as a Proposed Standard [RFC2874].

   The existence of multiple ways to represent an IPv6 address in the
   DNS has led to confusion and conflicts about which of these protocol
   enhancements should be implemented and/or deployed.  Having more than
   one choice of how IPv6 addresses are to be represented within the DNS
   can be argued to have led to delays in the deployment of IPv6.  In
   2002, "Representing Internet Protocol version 6 (IPv6) Addresses in
   the Domain Name System (DNS)" [RFC3363] moved A6 to Experimental
   status, with an aim of clearing up any confusion in this area.
   [RFC3363] and [RFC3364] compared AAAA and A6, and examined many of
   the issues in the A6 standard; these issues are summarized in this
   document.

   After ten years, the Experimental status of A6 continues to result in
   confusion and parallel deployment of both A6 and AAAA, albeit AAAA
   predominates by a large degree.  In recent IPv6 transition tests and