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Versions: 00 01                                                         
Behave WG                                                      B. Rajtar
Internet-Draft                                          Hrvatski Telekom
Intended status: Standards Track                               I. Farrer
Expires: January 16, 2014                            Deutsche Telekom AG
                                                               A. Vizdal
                                                             T-Mobile CZ
                                                                   X. Li
                                                                  C. Bao
                                       CERNET Center/Tsinghua University
                                                           July 15, 2013


       Framework for accessing IPv6 content for IPv4-only clients
            draft-rfvlb-behave-v6-content-for-v4-clients-01

Abstract

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

   This document describes a method for achieving this, including how
   the method could be implemented in real-world scenarios.

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].

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 http://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 January 16, 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
   (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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Solution Requirements . . . . . . . . . . . . . . . . . .   2
     1.2.  Covered Scenarios . . . . . . . . . . . . . . . . . . . .   3
     1.3.  Functional elements . . . . . . . . . . . . . . . . . . .   3
   2.  Algorithm Description . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Flow diagram  . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Usage scenarios . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   At the time of writing, IPv6 is still not widely deployed.  There are
   several reasons for this, one of which is that IPv4-only operating
   systems are still commonplace with end-users and account for a large
   fraction of overall Internet traffic.

   With the growth of IPv6 traffic, servers supporting only IPv6 are
   appearing on the Internet.  An approach for enabling and IPv4-only
   clients to access this content is described below.

1.1.  Solution Requirements

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






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   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.

   2.  The server hosting the content MUST have a valid AAAA record

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

   4.  Client's DNS queries MUST be resolved by a dedicated appliance,
       i.e. a caching nameserver.

   5.  All traffic between the client and the server MUST be routed
       through a device capable of performing translation between IPv4
       and IPv6, as described in [RFC6145] and [RFC6052].

   It is feasible that requirements (4) and (5) can be combined in one
   device and managed by the service provider.That would simplify
   operations and remove the need for a control-plane protocol between
   the two devices.

1.2.  Covered Scenarios

   [RFC6144] describes multiple scenarios for IPv4/IPv6 translation.
   This document is mainly concerned with Scenario 4: An IPv4 Network to
   the IPv6 Internet, but is also applicable to Scenario 6 (An IPv4
   Network to an IPv6 Network).  This scenario is not covered in this
   memo and can be elaborated in future documents, as necessary.
   Scenario 2, which faces similar challenges (The IPv4 Internet to an
   IPv6 Network), is covered by [I-D.draft-sun-behave-v4tov6-00].

1.3.  Functional elements

   Client  User end-device, typically a personal computer or similar.

   DNS proxy  Caching nameserver which proxies DNS queries from the
      client.

   NAT46 translator  Translation device which translates incoming IPv4
      traffic.

   IPv6-only server  Device which holds content on an IPv6-only network.

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



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   the scenario when the IPv4 client initiates a request for
   ipv6.example.com which is running on an IPv6-only server.

   1.  The customer types in "ipv6.example.com" into his web browser and
       initiaties the request for the web page.

   2.  The client operating system initiates a DNS query for
       "ipv6.example.com".  Since the client uses IPv4, the query is for
       an A record.

   3.  The DNS proxy receives the A record query and assumes the client
       is not IPv6 capable.  Therefore, it initiates a DNS query for A
       and AAAA records for "ipv6.example.com" 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 "ipv6.example.com" pointing at an un-used IPv4 address from
       the private address space (as described in [RFC1918]).

   6.  The private IPv4 address and the resolved IPv6 address of
       "ipv6.example.com" must be kept in the translation table of the
       NAT46 translator.  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 translator is out of the scope of this document.  In the case
       the translator and the DNS proxy are functions of the same
       device, the logic is simplified.

   7.  All IPv4 traffic from the client to "ipv6.example.com" 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 learned state and not a session triggered
       state.  The destination address of the translated IPv6 packet
       will be the resolved AAAA record of "ipv6.example.com", while the
       source IPv6 address will be created according to [RFC6052].  The
       IPv6 prefix used to create the source IPv6 address must be
       globally unique and allocated to the device.  If there are more
       IPv6 prefixes on the device, defining which one will be used is
       out of the scope of this document.  The IPv4 address used to
       create the source IPv6 address is the address of the client.

   8.  Return IPv6 traffic will be translated by the same device as the
       outgoing traffic, using IPv6 to IPv4 translation analogous to the



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       previous step.  The source IPv4 address will be the private IPv4
       address given by the DNS proxy to the client, while the
       destination IPv4 address would be the one of the client.

2.1.  Flow diagram

   In this example, the client is located behind a home gateway and is
   delegated an IPv4 address of 192.168.1.3.  The home gateway is acting
   as a DNS proxy and as a NAT46 translator.

   +-----------+       +----------------+   +-----------+ +------------+
   |           |       | (Home Gateway) |   |   DNS     | |   ipv6.    |
   |  Client   |       |   DNS proxy/   |   |authorative| |example.com |
   |192.168.1.3|       |NAT46 translator|   |  server   | |2000:db9::1 |
   |           |       |   2000:db8::1  |   |           | |            |
   +-----------        +----------------+   +-----------+ +------------+
        |    DNS A query for   |                      |          |
        |  "ipv6.example.com"  |                      |          |
        |--------------------->|DNS A and AAAA query  |          |
        |                      |for "ipv6.example.com"|          |
        |                      |--------------------->|          |
        |                      |   DNS AAAA response  |          |
        |                      |for "ipv6.example.com"|          |
        |DNS A response:       |<---------------------|          |
        |""ipv6.example.com"   |                      |          |
        |is located on 10.1.1.1|                                 |
        |<---------------------|                                 |
        | IPv4 SA:192.168.1.3  | IPv6 SA:2000:db8::192.168.1.3   |
        |   DA:10.1.1.1        | DA:2000:db9::1                  |
        |--------------------->|-------------------------------->|
        | IPv4 SA:10.1.1.1     | IPv6 SA:2000:db9::1             |
        |  DA:192.168.1.3      | DA:2000:db8::192.168.1.3        |
        |<---------------------|<--------------------------------|
        |                      |                                 |


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.

   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.



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4.  IANA Considerations

   This document makes no request of IANA.

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

5.  Security Considerations

6.  Acknowledgements

7.  Normative References

   [I-D.draft-sun-behave-v4tov6-00]
              , .

   [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

   Branimir Rajtar
   Hrvatski Telekom
   Zagreb
   Croatia

   Email: branimir.rajtar@t.ht.hr










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   Ian Farrer
   Deutsche Telekom AG
   Bonn
   Germany

   Email: ian.farrer@telekom.de


   Ales Vizdal
   T-Mobile CZ
   Prague
   Czech Republic

   Email: ales.vizdal@t-mobile.cz


   Xing Li
   CERNET Center/Tsinghua University
   Beijing
   China

   Email: xing@cernet.edu.cn


   Congxiao Bao
   CERNET Center/Tsinghua University
   Beijing
   China

   Email: congxiao@cernet.edu.cn





















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