Discovery of the IPv6 Prefix Used for IPv6 Address Synthesis
RFC 7050

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Internet Engineering Task Force (IETF)                     T. Savolainen
Request for Comments: 7050                                         Nokia
Category: Standards Track                                    J. Korhonen
ISSN: 2070-1721                                                 Broadcom
                                                                 D. Wing
                                                           Cisco Systems
                                                           November 2013

      Discovery of the IPv6 Prefix Used for IPv6 Address Synthesis

Abstract

   This document describes a method for detecting the presence of DNS64
   and for learning the IPv6 prefix used for protocol translation on an
   access network.  The method depends on the existence of a well-known
   IPv4-only fully qualified domain name "ipv4only.arpa.".  The
   information learned enables nodes to perform local IPv6 address
   synthesis and to potentially avoid NAT64 on dual-stack and multi-
   interface deployments.

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/rfc7050.

Savolainen, et al.           Standards Track                    [Page 1]
RFC 7050                  Pref64::/n Discovery             November 2013

Copyright Notice

   Copyright (c) 2013 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.

Table of Contents

   1. Introduction ....................................................3
   2. Requirements Notation and Terminology ...........................4
      2.1. Requirements Notation ......................................4
      2.2. Terminology ................................................4
   3. Node Behavior ...................................................4
      3.1. Validation of Discovered Pref64::/n ........................6
           3.1.1. DNSSEC Requirements for the Network .................7
           3.1.2. DNSSEC Requirements for the Node ....................7
      3.2. Connectivity Check .........................................8
           3.2.1. No Connectivity Checks against "ipv4only.arpa." .....9
      3.3. Alternative Fully Qualified Domain Names ..................10
      3.4. Message Flow Illustration .................................10
   4. Operational Considerations for Hosting the IPv4-Only
      Well-Known Name ................................................12
   5. Operational Considerations for DNS64 Operator ..................12
      5.1. Mapping of IPv4 Address Ranges to IPv6 Prefixes ...........13
   6. Exit Strategy ..................................................14
   7. Security Considerations ........................................14
   8. IANA Considerations ............................................15
      8.1. Domain Name Reservation Considerations ....................15
      8.2. IPv4 Address Allocation Considerations ....................16
      8.3. IAB Statement Regarding This .arpa Request ................17
   9. Acknowledgements ...............................................18
   10. References ....................................................18
      10.1. Normative References .....................................18
      10.2. Informative References ...................................19
   Appendix A.  Example of DNS Record Configuration ..................20
   Appendix B.  About the IPv4 Address for the Well-Known Name .......21

Savolainen, et al.           Standards Track                    [Page 2]
RFC 7050                  Pref64::/n Discovery             November 2013

1.  Introduction

   As part of the transition to IPv6, NAT64 [RFC6146] and DNS64
   [RFC6147] technologies will be utilized by some access networks to
   provide IPv4 connectivity for IPv6-only nodes [RFC6144].  DNS64
   utilizes IPv6 address synthesis to create local IPv6 addresses for
   peers having only IPv4 addresses, hence allowing DNS-using IPv6-only