Discovering PREF64 in Router Advertisements
draft-ietf-6man-ra-pref64-06

Document Type Active Internet-Draft (6man WG)
Last updated 2019-10-04 (latest revision 2019-10-03)
Replaces draft-pref64folks-6man-ra-pref64
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Document shepherd Bob Hinden
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Send notices to Bob Hinden <bob.hinden@gmail.com>
IPv6 Maintenance                                              L. Colitti
Internet-Draft                                                J. Linkova
Intended status: Standards Track                                  Google
Expires: April 5, 2020                                   October 3, 2019

              Discovering PREF64 in Router Advertisements
                      draft-ietf-6man-ra-pref64-06

Abstract

   This document specifies a Router Advertisement option to communicate
   NAT64 prefixes to hosts.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 5, 2020.

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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Use cases for communicating the NAT64 prefix to hosts . . . .   3
   3.  Why include the NAT64 prefix in Router Advertisements . . . .   3
   4.  Usage Guidelines  . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Option format . . . . . . . . . . . . . . . . . . . . . . . .   4
   6.  Handling Multiple NAT64 Prefixes  . . . . . . . . . . . . . .   6
   7.  PREF64 Consistency  . . . . . . . . . . . . . . . . . . . . .   7
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   8
     11.2.  Informative References . . . . . . . . . . . . . . . . .   9
     11.3.  URIs . . . . . . . . . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   NAT64 [RFC6146] with DNS64 [RFC6147] is a widely-deployed mechanism
   to provide IPv4 access on IPv6-only networks.  In various scenarios,
   the host must be aware of the NAT64 prefix in use by the network.
   This document specifies a Router Advertisement [RFC4861] option to
   communicate the NAT64 prefix to hosts.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

1.2.  Terminology

   PREF64 (or NAT64 prefix): an IPv6 prefix used for IPv6 address
   synthesis [RFC6146];

   NAT64: Network Address and Protocol Translation from IPv6 Clients to
   IPv4 Servers [RFC6146];

   RA: Router Advertisement, a message used by IPv6 routers to advertise
   their presence together with various link and Internet parameters
   [RFC4861];

   DNS64: a mechanism for synthesizing AAAA records from A records
   [RFC6147];

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2.  Use cases for communicating the NAT64 prefix to hosts

   On networks employing NAT64, it is useful for hosts to know the NAT64
   prefix for several reasons, including the following:

   o  Enabling DNS64 functions on end hosts.  In particular:

      *  Local DNSSEC validation (DNS64 in stub-resolver mode).  As
         discussed in [RFC6147] section 2, the stub resolver in the host
         "will try to obtain (real) AAAA RRs, and in case they are not
         available, the DNS64 function will synthesize AAAA RRs for
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