Network Working Group                                              X. Li
Internet-Draft                                                    C. Bao
Intended status: Informational         CERNET Center/Tsinghua University
Expires: February 18, 2011                               August 17, 2010


              DNS46 for the IPv4/IPv6 Stateless Translator
                draft-xli-behave-dns46-for-stateless-03

Abstract

   The stateless translator can support IPv6-initiated communications as
   well as IPv4-initiated communications for IPv6 hosts using IPv4-
   translatable addresses.  DNS support for the IPv6-initiated
   communication is defined in the DNS64 specification.  This document
   defines the DNS46 function for the stateless translator.

Status of this Memo

   This Internet-Draft is submitted to IETF 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 February 18, 2011.

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   Copyright (c) 2010 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
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   described in the Simplified BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . . . 3
   3.  DNS46 for the IPv4/IPv6 Stateless Translator  . . . . . . . . . 3
     3.1.  Authoritative DNS server  . . . . . . . . . . . . . . . . . 3
       3.1.1.  Static AAAA record  . . . . . . . . . . . . . . . . . . 3
       3.1.2.  Varying AAAA record . . . . . . . . . . . . . . . . . . 4
     3.2.  DNS resolver  . . . . . . . . . . . . . . . . . . . . . . . 4
       3.2.1.  DNS resolver for scenario 6 . . . . . . . . . . . . . . 4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5
   7.  Normative References  . . . . . . . . . . . . . . . . . . . . . 5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 6




































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.  Introduction

   DNS mechanism is one of the functions model for the IPv4/IPv6
   transition [I-D.ietf-behave-v6v4-framework].  DNS64 allows IPv6 hosts
   to resolve names of IPv4 hosts whereas DNS46 allows IPv4 hosts to
   resolve names of IPv6 hosts.

   General DNS46 is considered harmful, as NAT-PT was deprecated by IETF
   [RFC4966].  However, stateless translators can support IPv6-initiated
   communications (scenario 1 and 3) which requires the DNS64 support,
   as well as IPv4-initiated communications (scenario 2 and 4) which
   requires the DNS46 support [I-D.ietf-behave-v6v4-framework]
   [I-D.ietf-behave-v6v4-xlate].

   DNS64 is used for both stateful and stateless translators and it is
   defined in [I-D.ietf-behave-dns64].  DNS46 is only used for the
   stateless translators and it is defines in this document.


.  Notational Conventions

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


.  DNS46 for the IPv4/IPv6 Stateless Translator

   The DNS46 for stateless IPv4/IPv6 translation is for the following
   scenarios:

   o  Scenario 2: The IPv4 Internet to an IPv6 network.

   o  Scenario 6: An IPv4 network to an IPv6 network.

3.1.  Authoritative DNS server

   Since the destination is "an IPv6 network", DNS46 can be deployed as
   an authoritative DNS server [RFC1035] in an IPv6 network.

3.1.1.  Static AAAA record

   This is very similar to the authoritative DNS configuration of dual-
   stack hosts.  The only difference is that in the dual-stack case, the
   A record and AAAA record are independent, while in stateless
   translation case, the hosts are typically IPv6 single stack (or for
   some reason incapable of using IPv4 on a particular network) using
   IPv4-translatable addresses and the A record MUST be derived from the



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   AAAA record based on the algorithm and the PREFIX information
   [I-D.ietf-behave-address-format].

3.1.2.  Varying AAAA record

   If an IPv6 host has a varying AAAA record (that is, it could change
   due to the IPv6-only host changing its IPv6 address and registering
   its new address via, for example, DNS Dynamic Updates [RFC2316]),
   then the dynamic DNS46 function is required.  However, it is still
   the authoritative DNS.  When the authoritative DNS receives a dynamic
   update containing AAAA record, it MUST synthesize corresponding A
   record before signing the zone, which can be derived based on the
   algorithm and the PREFIX information
   [I-D.ietf-behave-address-format].

3.2.  DNS resolver

   For scenario 2 (the IPv4 Internet to an IPv6 network) the
   implementation of DNS46 resolver is impossible, since the IPv4 hosts
   are in the IPv4 Internet.

3.2.1.  DNS resolver for scenario 6

   However, for scenario 6 (an IPv4 network to IPv6 network)
   [I-D.ietf-behave-v6v4-framework], it is possible to use DNS resolver
   in an IPv4 network to synthesize A records from the AAAA records
   based on the algorithm and the PREFIX information
   [I-D.ietf-behave-address-format].


.  Security Considerations

   When DNS46 function is provided by authoritative DNS server, DNS46
   can support DNSSEC without problem.

   When DNS46 function is provided by authoritative DNS server, the
   reverse DNS is also under the same network operator's control which
   may provide additional validation function for the IPv4-translatable
   IPv6 addresses.


.  IANA Considerations

   This memo adds no new IANA considerations.

   Note to RFC Editor: This section will have served its purpose if it
   correctly tells IANA that no new assignments or registries are
   required, or if those assignments or registries are created during



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   the RFC publication process.  From the author's perspective, it may
   therefore be removed upon publication as an RFC at the RFC Editor's
   discretion.


.  Acknowledgments

   The authors would like to acknowledge the following contributors of
   this document: Dan Wing and Kevin Yin.


.  Normative References

   [I-D.ietf-behave-address-format]
              Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
              Li, "IPv6 Addressing of IPv4/IPv6 Translators",
              draft-ietf-behave-address-format-10 (work in progress),
              August 2010.

   [I-D.ietf-behave-dns64]
              Bagnulo, M., Sullivan, A., Matthews, P., and I. Beijnum,
              "DNS64: DNS extensions for Network Address Translation
              from IPv6 Clients to IPv4 Servers",
              draft-ietf-behave-dns64-10 (work in progress), July 2010.

   [I-D.ietf-behave-v6v4-framework]
              Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
              IPv4/IPv6 Translation",
              draft-ietf-behave-v6v4-framework-09 (work in progress),
              May 2010.

   [I-D.ietf-behave-v6v4-xlate]
              Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
              Algorithm", draft-ietf-behave-v6v4-xlate-20 (work in
              progress), May 2010.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, November 1987.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2316]  Bellovin, S., "Report of the IAB Security Architecture
              Workshop", RFC 2316, April 1998.

   [RFC4966]  Aoun, C. and E. Davies, "Reasons to Move the Network
              Address Translator - Protocol Translator (NAT-PT) to
              Historic Status", RFC 4966, July 2007.



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Authors' Addresses

   Xing Li
   CERNET Center/Tsinghua University
   Room 225, Main Building, Tsinghua University
   Beijing  100084
   CN

   Phone: +86 10-62785983
   Email: xing@cernet.edu.cn


   Congxiao Bao
   CERNET Center/Tsinghua University
   Room 225, Main Building, Tsinghua University
   Beijing  100084
   CN

   Phone: +86 10-62785983
   Email: congxiao@cernet.edu.cn































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