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Versions: (draft-anderson-v6ops-v4v6-xlat-prefix) 00 01 02 RFC 8215

IPv6 Operations                                              T. Anderson
Internet-Draft                                            Redpill Linpro
Intended status: Standards Track                           June 20, 2017
Expires: December 22, 2017


                 Local-use IPv4/IPv6 Translation Prefix
                  draft-ietf-v6ops-v4v6-xlat-prefix-02

Abstract

   This document reserves the IPv6 prefix 64:ff9b:1::/48 for local use
   within domains that enable IPv4/IPv6 translation mechanisms.

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 December 22, 2017.

Copyright Notice

   Copyright (c) 2017 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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   2
   4.  Why 64:ff9b:1::/48? . . . . . . . . . . . . . . . . . . . . .   3
     4.1.  Prefix Length . . . . . . . . . . . . . . . . . . . . . .   3
     4.2.  Prefix Value  . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Deployment Considerations . . . . . . . . . . . . . . . . . .   4
   6.  Checksum Neutrality . . . . . . . . . . . . . . . . . . . . .   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   This document reserves 64:ff9b:1::/48 for local use within domains
   that enable IPv4/IPv6 translation mechanisms.  This facilitates the
   co-existence of multiple IPv4/IPv6 translation mechanisms in the same
   network without requiring the use of a Network-Specific Prefix
   assigned from the operator's allocated global unicast address space.

2.  Terminology

   This document makes use of the following terms:

   Network-Specific Prefix (NSP)
      A globally unique prefix assigned by a network operator for use
      with an IPv4/IPv6 translation mechanism [RFC6052].

   Well-Known Prefix (WKP)
      The prefix 64:ff9b::/96, which is reserved for use with the
      [RFC6052] IPv4/IPv6 address translation algorithm.

3.  Problem Statement

   Since the WKP 64:ff9b::/96 was reserved by [RFC6052], several new
   IPv4/IPv6 translation mechanisms have been defined by the IETF, such
   as [RFC6146] and [RFC7915].  These mechanisms target various
   different use cases.  An operator might therefore wish to make use of
   several of them simultaneously.

   The WKP is reserved specifically for use with the algorithm specified
   in [RFC6052].  More recent IETF documents describe IPv4/IPv6



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   translation mechanisms that use different algorithms.  An operator
   deploying such mechanisms can not make use of the WKP in a legitimate
   fashion.

   Also, because the WKP is a /96, an operator preferring to use the WKP
   over an NSP can only do so for only one of their IPv4/IPv6
   translation mechanisms.  All others must necessarily use an NSP.

   Section 3.1 of [RFC6052] imposes certain restrictions on the use of
   the WKP, such as forbidding its use in combination with private IPv4
   addresses [RFC1918].  These restrictions might conflict with the
   operator's desired use of an IPv4/IPv6 translation mechanism.

   In summary, there is a need for a local-use prefix that facilitates
   the co-existence of multiple IPv4/IPv6 translation mechanisms in a
   single network domain, as well as the deployment of translation
   mechanisms that do not use the [RFC6052] algorithm or adhere to its
   usage restrictions.

4.  Why 64:ff9b:1::/48?

4.1.  Prefix Length

   One of the primary goals of this document is to facilitate multiple
   simultaneous deployments of IPv4/IPv6 translation mechanisms in a
   single network.  The first criterion is therefore that the prefix
   length chosen must be shorter than the prefix length used by any
   individual translation mechanism.

   The second criterion is that the prefix length chosen is a multiple
   of 16.  This ensures the prefix ends on a colon boundary when
   representing it in text, easing operator interaction with it.

   The [RFC6052] algorithm specifies IPv4/IPv6 translation prefixes as
   short as /32.  In order to facilitate multiple instances of
   translation mechanisms using /32s, while at the same time aligning on
   a 16-bit boundary, it would be necessary to reserve a /16.  Doing so,
   however, was considered as too wasteful by the IPv6 Operations
   working group.

   The shortest translation prefix that was reported to the IPv6
   Operations working group to be deployed in a live network was /64.
   The longest 16-bit-aligned prefix length that can accommodate
   multiple instances of /64 is /48.  The prefix length of /48 was
   therefore chosen, as it satisfies both the criteria above, while at
   the same time avoids wasting too much of the IPv6 address space.





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4.2.  Prefix Value

   It is desirable to minimise the amount of additional "pollution" in
   the unallocated IPv6 address space caused by the reservation made by
   this document.  Ensuring the reserved prefix is adjacent to the
   64:ff9b::/96 WKP already reserved by [RFC6052] accomplishes this.

   Given the previous decision to use a prefix length of /48, this
   leaves two options: 64:ff9a:ffff::/48 and 64:ff9b:1::/48.

   64:ff9a:ffff::/48 has the benefit that it is completely adjacent to
   the [RFC6052] WKP.  That is, 64:ff9a:ffff::/48 and 64:ff9b::/96
   combines to form a uninterrupted range of IPv6 addresses starting
   with 64:ff9a:ffff:: and ending with 64:ff9b::ffff:ffff.

   64:ff9b:1::/48 is, on the other hand, not completely adjacent to
   64:ff9b::/96.  The range starting with 64:ff9b::1:0:0 and ending with
   64:ff9b:0:ffff:ffff:ffff:ffff:ffff would remain unallocated.

   This particular drawback is, however, balanced by the fact that the
   smallest possible aggregate prefix that covers both the [RFC6052] WKP
   and 64:ff9a:ffff::/48 is much larger than the smallest possible
   aggregate prefix that covers both the [RFC6052] WKP and
   64:ff9b:1::/48.  These aggregate prefixes are 64:ff9a::/31 and
   64:ff9b::/47, respectively.  IPv6 address space is allocated using
   prefixes rather than address ranges, so it could be argued that
   64:ff9b:1::/48 is the option that would cause special-use prefixes
   reserved for IPv4/IPv6 translation to "pollute" the minimum possible
   amount of unallocated IPv6 address space.

   Finally, 64:ff9b:1::/48 also has the advantage that its textual
   representation is shorter than 64:ff9a:ffff::/48.  While this might
   seem insignificant, the preference human network operators have for
   addresses that are simple to type should not be underestimated.

   After weighing the above pros and cons, 64:ff9b:1::/48 was chosen.

5.  Deployment Considerations

   64:ff9b:1::/48 is intended as a technology-agnostic and generic
   reservation.  A network operator may freely use it in combination
   with any kind of IPv4/IPv6 translation mechanism deployed within
   their network.

   By default, IPv6 nodes and applications must not treat IPv6 addresses
   within 64:ff9b:1::/48 different from other globally scoped IPv6
   addresses.  In particular, they must not make any assumptions
   regarding the syntax or properties of those addresses (e.g., the



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   existence and location of embedded IPv4 addresses), or the type of
   associated translation mechanism (e.g., whether it is stateful or
   stateless).

   64:ff9b:1::/48 or any more-specific prefix may only be used in inter-
   domain routing if done in accordance with the rules described in
   Section 3.2 of [RFC6052].

   Note that 64:ff9b:1::/48 (or any more-specific prefix) is distinct
   from the WKP 64:ff9b::/96.  Therefore, the restrictions on the use of
   the WKP described in Section 3.1 of [RFC6052] do not apply to the use
   of 64:ff9b:1::/48.

   Operators tempted to use the covering aggregate prefix 64:ff9b::/47
   to refer to all special-use prefixes currently reserved for IPv4/IPv6
   translation should be warned that this aggregate includes a range of
   unallocated addresses (Section 4.2) that the IETF could potentially
   reserve in the future for entirely different purposes.

6.  Checksum Neutrality

   Use of 64:ff9b:1::/48 does not in itself guarantee checksum
   neutrality, as many of the IPv4/IPv6 translation algorithms it can be
   used with are fundamentally incompatible with checksum-neutral
   address translations.

   Section 4.1 of [RFC6052] contains further discussion about IPv4/IPv6
   translation and checksum neutrality.

   The Stateless IP/ICMP Translation algorithm [RFC7915] is one well-
   known algorithm that can operate in a checksum-neutral manner, when
   using the [RFC6052] algorithm for all of its address translations.
   However, in order to attain checksum neutrality it is imperative that
   the translation prefix is chosen carefully.  Specifically, in order
   for a 96-bit [RFC6052] prefix to be checksum neutral, all the six
   16-bit words in the prefix must add up to a multiple of 0xffff.

   The following non-exhaustive list contains examples of translation
   prefixes that are checksum neutral when used with the [RFC7915] and
   [RFC6052] algorithms:

   o  64:ff9b:1:fffe::/96

   o  64:ff9b:1:fffd:1::/96

   o  64:ff9b:1:fffc:2::/96

   o  64:ff9b:1:abcd:0:5431::/96



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7.  IANA Considerations

   (Note to the RFC Editor: Please replace occurrences of "TBD" in this
   section with the assigned RFC number of this document and delete this
   note.)

   The IANA is requested to add the following entry to the IPv6 Special-
   Purpose Address Registry:

              +----------------------+---------------------+
              | Attribute            | Value               |
              +----------------------+---------------------+
              | Address Block        | 64:ff9b:1::/48      |
              | Name                 | IPv4-IPv6 Translat. |
              | RFC                  | (TBD)               |
              | Allocation Date      | (TBD)               |
              | Termination Date     | N/A                 |
              | Source               | True                |
              | Destination          | True                |
              | Forwardable          | True                |
              | Global               | False               |
              | Reserved-by-Protocol | False               |
              +----------------------+---------------------+

   The IANA is furthermore requested to add the following footnote to
   the 0000::/8 entry of the Internet Protocol Version 6 Address Space
   registry:

      64:ff9b:1::/48 reserved for Local-use IPv4/IPv6 Translation [TBD]

8.  Security Considerations

   The reservation of 64:ff9b:1::/48 is not known to cause any new
   security considerations beyond those documented in Section 5 of
   [RFC6052].

9.  References

9.1.  Normative References

   [RFC6052]  Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
              Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
              DOI 10.17487/RFC6052, October 2010,
              <http://www.rfc-editor.org/info/rfc6052>.







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9.2.  Informative References

   [RFC1918]  Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
              and E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996,
              <http://www.rfc-editor.org/info/rfc1918>.

   [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
              NAT64: Network Address and Protocol Translation from IPv6
              Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
              April 2011, <http://www.rfc-editor.org/info/rfc6146>.

   [RFC7915]  Bao, C., Li, X., Baker, F., Anderson, T., and F. Gont,
              "IP/ICMP Translation Algorithm", RFC 7915,
              DOI 10.17487/RFC7915, June 2016,
              <http://www.rfc-editor.org/info/rfc7915>.

Acknowledgements

   The author would like to thank Fred Baker, Mohamed Boucadair, Brian E
   Carpenter, Pier Carlo Chiodi, Joe Clarke, David Farmer, Suresh
   Krishnan, Warren Kumari, Holger Metschulat, Federico Santandrea and
   David Schinazi for contributing to the creation of this document.

Author's Address

   Tore Anderson
   Redpill Linpro
   Vitaminveien 1A
   0485 Oslo
   Norway

   Phone: +47 959 31 212
   Email: tore@redpill-linpro.com
   URI:   http://www.redpill-linpro.com
















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