Discovering NAT64 IPv6 Prefixes Using the Port Control Protocol (PCP)
RFC 7225

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Internet Engineering Task Force (IETF)                      M. Boucadair
Request for Comments: 7225                                France Telecom
Category: Standards Track                                       May 2014
ISSN: 2070-1721

 Discovering NAT64 IPv6 Prefixes Using the Port Control Protocol (PCP)

Abstract

   This document defines a new Port Control Protocol (PCP) option to
   learn the IPv6 prefix(es) used by a PCP-controlled NAT64 device to
   build IPv4-converted IPv6 addresses.  This option is needed for
   successful communications when IPv4 addresses are used in referrals.

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/rfc7225.

Copyright Notice

   Copyright (c) 2014 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.

Boucadair                    Standards Track                    [Page 1]
RFC 7225                       PCP & NAT64                      May 2014

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Issues  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . .   3
       3.2.1.  AAAA Synthesis by the DNS Stub-resolver . . . . . . .   4
       3.2.2.  Application Referrals . . . . . . . . . . . . . . . .   4
   4.  PREFIX64 Option . . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Format  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.2.  Server's Behavior . . . . . . . . . . . . . . . . . . . .   7
     4.3.  Client's Behavior . . . . . . . . . . . . . . . . . . . .   9
   5.  Flow Examples . . . . . . . . . . . . . . . . . . . . . . . .  10
     5.1.  TCP Session Initiated from an IPv6-only Host  . . . . . .  10
     5.2.  SIP Flow Example  . . . . . . . . . . . . . . . . . . . .  11
     5.3.  Mapping of IPv4 Address Ranges to IPv6 Prefixes . . . . .  13
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  15
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  16

1.  Introduction

   According to [RFC6146], NAT64 uses Pref64::/n to construct
   IPv4-converted IPv6 addresses as defined in [RFC6052].

   This document defines a new Port Control Protocol (PCP) option
   [RFC6887] to inform PCP clients about the Pref64::/n and suffix
   [RFC6052] used by a PCP-controlled NAT64 device [RFC6146].  It does
   so by defining a new PREFIX64 option.

   This PCP option is a deterministic solution to help establish
   communications between IPv6-only hosts and remote IPv4-only hosts.
   Unlike [RFC7050], this option solves all the issues identified in
   [RFC7051].

   Some illustrative examples are provided in Section 5.  Detailed
   experiments conducted to assess the applicability of the PREFIX64
   option for services (e.g., accessing a video server, establishing
   SIP-based sessions, etc.) in NAT64 environments are available in
   [EXPERIMENTS].

   The use of this PCP option for NAT64 load-balancing purposes is out
   of scope.

Boucadair                    Standards Track                    [Page 2]
RFC 7225                       PCP & NAT64                      May 2014

2.  Requirements Language

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

3.  Problem Statement