Framework for accessing IPv6 content for IPv4-only clients

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Document Type Active Internet-Draft (individual)
Authors Branimir Rajtar , Ian Farrer  , Vizdal Ales  , Xing Li  , Congxiao Bao 
Last updated 2013-07-01
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Behave WG                                                      B. Rajtar
Internet-Draft                                          Hrvatski Telekom
Intended status: Standards Track                               I. Farrer
Expires: January 02, 2014                            Deutsche Telekom AG
                                                               A. Vizdal
                                                             T-Mobile CZ
                                                                   X. Li
                                                                  C. Bao
                                       CERNET Center/Tsinghua University
                                                           July 01, 2013

       Framework for accessing IPv6 content for IPv4-only clients


   With the expansion of IPv6 usage and content available on IPv6, it is
   important to enable clients with legacy (i.e. non IPv6-ready)
   operating systems to access such content.

   This document describes how this can be achieved and how it can be
   implemented in a real-world scenario.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

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
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   This Internet-Draft will expire on January 02, 2014.

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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Solution Requirements . . . . . . . . . . . . . . . . . .   3
     1.2.  Covered Scenarios . . . . . . . . . . . . . . . . . . . .   3
   2.  Algorithm Description . . . . . . . . . . . . . . . . . . . .   3
   3.  Usage scenarios . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   At the time of writing, IPv6 is still not widely deployed.  Several
   reasons can be named, one of which is the fact that IPv4-only
   operating systems are still used by many end customers and account
   for a large fraction of total Internet traffic.  Also, with the
   introduction of Carrier-Grade NAT, exhaustion of IPv4 address space
   is no longer an issue which would be the key driver of the transition
   to IPv6.

   With the growth of IPv6 traffic, servers only supporting IPv6 are
   appearing on the Internet and IPv4-only clients must be able to
   access content available on them.  The following sections describe a
   methodology how this can achieved.

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1.1.  Solution Requirements

   To clarify when this approach is applicable, the following
   requirements can be named:

   1.  The content must be reachable through IPv6, i.e. the server on
       which the content is stored must have a valid IPv6 address and a
       working IPv6 stack.  As can be seen later in the document, this
       in turn implies that the server must have a valid AAAA record.

   2.  The client must support only IPv4.  The other alternative is also
       that it supports IPv6, but for some reason uses only IPv4 to
       access content on the Internet.

   3.  Client's DNS queries must be proxied by a dedicated appliance.

   4.  All traffic between the client and the server must pass through a
       device capable of performing translation between IPv4 and IPv6,
       as described in [RFC6145] and [RFC6052].

   It is feasible that requirements three and four can be combined in
   one device and managed by the service provider.

1.2.  Covered Scenarios

   As described in [RFC6144], there are multiple scenarios for IPv4/IPv6
   translation.  This document covers mainly Scenario 4: An IPv4 Network
   to the IPv6 Internet, but is not limited to be used for the following
   scenarios as well:

   o  Scenario 2: The IPv4 Internet to an IPv6 Network

   o  Scenario 6: An IPv4 Network to an IPv6 Network

   These scenarios are not subject of this draft and can be elaborated
   in future documents, if deemed necessary.

2.  Algorithm Description

   This section describes how the algorithm works and the roles of every
   functional element.  The steps are in cronological order, and display
   the scenario when the IPv4 client initiates a request for
   which is running on an IPv6-only server.

   1.  The customer types in "" into his web browser and
       initiaties the request for the web page.

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   2.  The client operating system initiates a DNS query for
       "".  Since the client uses IPv4, the query is for an A

   3.  DNS proxy perceives that the query is for an A resource record
       only and assumes the client is not IPv6 capable.  Therefore, it
       initiates a DNS query for A and AAAA records for "" to
       the authorative DNS server.

   4.  If a DNS response is received with only an AAAA record, the DNS
       proxy assumes that the server is IPv6-only.  (In case the proxy
       receives both A or AAAA records, or just an A record, the A
       record is returned to the client and the process ends here.)

   5.  As a response to the client, the proxy returns a fake A record
       for "" pointing at an IPv4 address from the private
       address space (as described in [RFC1918] ).

   6.  The private IPv4 address and the resolved IPv6 address of
       "" must be kept in translation table at the device
       which performs the actual translation.  The time the translation
       would stay active in the table would be equal to the TTL field of
       the DNS response.  How the DNS-related information is conveyed
       from the DNS proxy to the translation device is out of the scope
       of this document.

   7.  All IPv4 traffic from the client to "" will be
       translated to IPv6 as described in [RFC6145].  Unlike NAT-PT
       described in [RFC2766] (moved to Historic Status by [RFC4966]),
       the translation is a configured state and not a session triggered
       state.  The destination address of the translated IPv6 packet
       will be the resolved AAAA record of "", while the
       source IPv6 address will be created according to [RFC6052].  The
       IPv4 address and IPv6 prefix used to create the source IPv6
       address are out of the scope of this document.

   8.  Return IPv6 traffic will be translated at the same device as the
       outgoing traffic, using IPv6 to IPv4 translation analogous to the
       one described in previous step.  The source IPv4 address would be
       the private IPv4 address given by the DNS proxy to the client,
       while the destination IPv4 address would be the one of the

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3.  Usage scenarios

   The typical scenario where such a solution can be used is the home
   network.  The customer can have a broadband service with access to
   IPv6 Internet, but uses an IPv4-only client.  The DNS proxy and the
   translation device would in that case be the home gateway, which
   would handle the decision-making process, as well as the translation
   as well.

   However, other scenarios can also be foreseable, such as mobile
   access, business customers, etc.  It's applicable to all scenarios
   where a DNS proxy is used, as well as a default gateway which can act
   as a translation device.

4.  IANA Considerations

   This document makes no request of IANA.

   Note to RFC Editor: this section may be removed on publication as an

5.  Security Considerations

6.  Acknowledgements

7.  Normative References

   [RFC1918]  , "Address Allocation for Private Internets", .

   [RFC2119]  , "Key words for use in RFCs to Indicate Requirement
              Levels", .

   [RFC2766]  , "Network Address Translation - Protocol Translation
              (NAT-PT)", .

   [RFC4966]  , "Reasons to Move the Network Address Translator -
              Protocol Translator (NAT-PT) to Historic Status", .

   [RFC6052]  , "IPv6 Addressing of IPv4/IPv6 Translators", .

   [RFC6144]  , "Framework for IPv4/IPv6 Translation", .

   [RFC6145]  , "IP/ICMP Translation Algorithm", .

Authors' Addresses

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   Branimir Rajtar
   Hrvatski Telekom


   Ian Farrer
   Deutsche Telekom AG


   Ales Vizdal
   T-Mobile CZ
   Czech Republic


   Xing Li
   CERNET Center/Tsinghua University


   Congxiao Bao
   CERNET Center/Tsinghua University


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