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Versions: 00 01 02 03 draft-ietf-v6ops-siit-eam

IPv6 Operations                                              T. Anderson
Internet-Draft                                            Redpill Linpro
Updates: 6145 (if approved)                             January 08, 2015
Intended status: Standards Track
Expires: July 12, 2015


      Explicit Address Mappings for Stateless IP/ICMP Translation
                    draft-anderson-v6ops-siit-eam-03

Abstract

   This document extends the Stateless IP/ICMP Translation Algorithm
   (SIIT) with an Explicit Address Mapping (EAM) algorithm, and formally
   updates RFC 6145.  The EAM algorithm facilitates stateless IP/ICMP
   translation between arbitrary (non-IPv4-translatable) IPv6 endpoints
   and IPv4.

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 July 12, 2015.

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.












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   This document is subject to BCP 78 and the IETF Trust's Legal
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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Explicit Address Mapping Algorithm  . . . . . . . . . . . . .   5
     3.1.  Explicit Address Mapping Table  . . . . . . . . . . . . .   5
     3.2.  Explicit Address Mapping Specification  . . . . . . . . .   6
     3.3.  IP Address Translation Procedure  . . . . . . . . . . . .   6
       3.3.1.  Address Translation Steps: IPv4 to IPv6 . . . . . . .   7
       3.3.2.  Address Translation Steps: IPv6 to IPv4 . . . . . . .   7
   4.  Lack of Checksum Neutrality . . . . . . . . . . . . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Appendix A.  Use Cases  . . . . . . . . . . . . . . . . . . . . .   9
     A.1.  464XLAT . . . . . . . . . . . . . . . . . . . . . . . . .   9
     A.2.  IVI . . . . . . . . . . . . . . . . . . . . . . . . . . .  10
     A.3.  SIIT-DC . . . . . . . . . . . . . . . . . . . . . . . . .  10
   Appendix B.  Example IP Address Translations  . . . . . . . . . .  11
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   The Stateless IP/ICMP Translation Algorithm (SIIT) [RFC6145]
   specifies that when translating IPv4 addresses to IPv6 and vice
   versa, all addresses must be translated using the algorithm specified
   in [RFC6052].  This document specifies an alternative to the
   [RFC6052] algorithm, where IP addresses are translated according to a
   table of Explicit Address Mappings configured on the stateless
   translator.  This removes the previous constraint that IPv6 nodes
   that communicate with IPv4 nodes through SIIT must be configured with
   IPv4-translatable IPv6 addresses.





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   The Explicit Address Mapping Table does not replace [RFC6052].  For
   most use cases, it is expected that both algorithms are used in
   concert.  The Explicit Address Mapping algorithm is used only when a
   mapping matching the address to be translated exists.  If no matching
   mapping exists, the [RFC6052] algorithm will be used instead.  Thus,
   when translating an individual IP packet, an SIIT implementation
   might translate one of the two IP address fields according to an EAM,
   while the other IP address field is translated according to
   [RFC6052].

1.1.  Terminology

   This document makes use of the following terms:

   EAM
      An Explicit Address Mapping, as specified in Section 3.2.

   EAMT
      The Explicit Address Mapping Table, as specified in Section 3.1.

   SIIT
      The Stateless IP/ICMP Translation algorithm, as specified in
      [RFC6145].

   IPv4-converted IPv6 addresses
      As defined in Section 1.3 of [RFC6052].

   IPv4-translatable IPv6 addresses
      As defined in Section 1.3 of [RFC6052].

   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 [RFC2119].

2.  Problem Statement

   Section 3.2.1 of [RFC6144] notes that "stateless translation
   mechanisms typically put constraints on what IPv6 addresses can be
   assigned to IPv6 nodes that want to communicate with IPv4
   destinations using an algorithmic mapping".  In practice, this means
   that the IPv6 nodes must be configured with IPv4-translatable IPv6
   addresses.  For the reasons discussed below, some environments may
   find that the use of IPv4-translatable IPv6 addresses is not desired
   or even possible.

   Limited availability:
      The number of IPv4-translatable IPv6 addresses available to an
      operator is equal to the number of IPv4 addresses he assigns to



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      the SIIT function.  IPv4 addresses are scarce, and as a result an
      operator might not have enough IPv4-translatable IPv6 addresses to
      number his entire IPv6 infrastructure.

   Restricted format:
      IPv4-translatable IPv6 addresses must conform to the format
      specified in Section 2.2 of [RFC6052].  This format is not
      compatible with other common IPv6 address formats, such as the
      EUI-64 based IPv6 address format used by IPv6 Stateless Address
      Autoconfiguration [RFC4862].

   An operator could overcome the above two problems by building an IPv6
   network using regular (non-IPv4-translatable) IPv6 addresses, and
   assign IPv4-translatable IPv6 addresses as secondary addresses on the
   nodes that want to communicate with IPv4 nodes through SIIT only.
   However, doing so may result in a new set of undesired properties:

   Routing complexity:
      The IPv4-translatable IPv6 addresses must be routed throughout the
      IPv6 network separately from the primary (non-IPv4-translatable)
      IPv6 addresses used by the nodes.  It might be impossible to
      aggregate these routes, as two adjacent IPv4-translatable IPv6
      addresses might not be assigned to two adjacent IPv6 nodes.  As a
      result, in order to support SIIT, the IPv6 network might need to
      carry a large number of extraneous routes.  These routes must be
      separately injected into the IPv6 routing topology somehow.  Any
      intermediate devices in the IPv6 network such as a firewall might
      require special configuration in order to treat the
      IPv4-translatable IPv6 address the same as the primary IPv6
      address, for example by requiring that any ACL entries involving
      the primary IPv6 address of a node must be duplicated.

   Operational complexity:


















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      The IPv4-translatable IPv6 addresses must not only be assigned to
      the IPv6 nodes participating in SIIT; all applications and
      services on those nodes must also be configured to use them.  For
      example, if the IPv6 node is a load balancer, it might require a
      separate Virtual Server definition using the IPv4-translatable
      IPv6 address in addition to one using the service's primary IPv6
      address.  A web server might require specific configuration to
      listen for connections on both the IPv4-translatable and the
      primary IPv6 address.  A High-Availability cluster service must be
      set up to fail over both addresses between cluster nodes, and
      depending on how the IPv6 network learns the location of the
      IPv4-translatable IPv6 address, the fail-over mechanism used for
      the two addresses might be completely different.  Service
      monitoring must be done for both the IPv4-translatable and the
      primary IPv6 address, and any trouble-shooting procedures must be
      extended to involve both addresses.

   In short, the use of IPv4-translatable IPv6 addresses in parallel
   with regular IPv6 addresses is in many ways analogous to the use of
   Dual Stack [RFC4213].  While no actual IPv4 packets are used, the
   IPv4-translatable IPv6 addresses creates a secondary "stack" in the
   infrastructure that must be treated and operated separately from the
   primary one.  This increases the complexity of the overall
   infrastructure, in turn increasing operational overhead, and reducing
   reliability.  An operator who for such reasons finds the use Dual
   Stack unappealing, might feel the same way about using SIIT with
   IPv4-translatable IPv6 addresses.

3.  Explicit Address Mapping Algorithm

   This normative section defines the EAM algorithm.  SIIT
   implementations are REQUIRED to support the specifications herein.

3.1.  Explicit Address Mapping Table

   An SIIT implementation MUST include an Explicit Address Mapping Table
   (EAMT).  By default, the EAMT SHOULD be empty.  The operator MUST be
   able to populate the EAMT using the implementation's normal
   configuration interfaces.  The implementation MAY additionally
   support other ways of populating the EAMT.

   The EAMT consists of the following columns:

      IPv4 Prefix

      IPv6 Prefix





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   SIIT implementations MAY include other columns in order to support
   proprietary extensions to the EAM algorithm.

   Throughout this document, figures representing the EAMT contain an
   Index column using the pound sign as the header.  This column is not
   a required part of this specification; it is included only as a
   convenience to the reader.

3.2.  Explicit Address Mapping Specification

   An EAM consists of an IPv4 Prefix and an IPv6 Prefix.  The prefix
   length MAY be omitted, in which case the implementation MUST assume
   it to be 32 for IPv4 and 128 for IPv6.  Figure 1 illustrates an EAMT
   containing examples of valid EAMs.

                               Example EAMT

               +---+----------------+----------------------+
               | # | IPv4 Prefix    |     IPv6 Prefix      |
               +---+----------------+----------------------+
               | 1 | 192.0.2.1      | 2001:db8:aaaa::      |
               | 2 | 192.0.2.2/32   | 2001:db8:bbbb::b/128 |
               | 3 | 192.0.2.16/28  | 2001:db8:cccc::/124  |
               | 4 | 192.0.2.128/26 | 2001:db8:dddd::/64   |
               | 5 | 192.0.2.192/31 | 64:ff9b::/127        |
               +---+----------------+----------------------+

                                 Figure 1

   An EAM's IPv4 Prefix value MUST have an identical or smaller number
   of suffix bits than its corresponding IPv6 Prefix value.

   Overlapping EAMs SHOULD be considered an error, and attempts to
   insert them into the EAMT SHOULD be blocked.  The behaviour of an
   SIIT implementation when overlapping EAMs are present in the EAMT is
   left undefined.

   When translating a packet between IPv4 and IPv6, an SIIT
   implementation MUST individually translate each IP address it
   encounters in the packet's IP headers (including any IP headers
   contained within ICMP errors) according to Section 3.3.

3.3.  IP Address Translation Procedure

   This section describes step-by-step how an SIIT implementation
   translates addresses between IPv4 and IPv6.  Only the outcome of the
   algorithm described should be considered normative, that is, an SIIT
   implementation MAY implement the exact procedure differently than



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   what is described here, but the outcome of the algorithm MUST be the
   same.

   For concrete examples of IP addresses translations, refer to
   Appendix B.

3.3.1.  Address Translation Steps: IPv4 to IPv6

   1.  The EAMT is searched for an EAM entry containing an IPv4 Prefix
       identical to that of the IPv4 address being translated.  The IPv4
       Prefix and IPv6 Prefix values of the EAM entry found is from now
       on referred to as EAM4 and EAM6, respectively.

   2.  If no matching EAM entry is found, the EAM algorithm is aborted.
       The SIIT implementation MUST proceed to translate the address in
       accordance with [RFC6145] (and its updates).

   3.  The prefix bits of EAM4 are removed from IPv4 address being
       translated.  The remaining suffix bits from the IPv4 address
       being translated are stored in a temporary buffer.

   4.  The prefix bits of EAM6 are prepended to the temporary buffer.

   5.  If the temporary buffer at this point does not contain a 128-bit
       value, it is padded with trailing zeroes so that it reaches a
       length of 128 bits.

   6.  The contents of the temporary buffer is the translated IPv6
       address.

3.3.2.  Address Translation Steps: IPv6 to IPv4

   1.  The EAMT is searched for an EAM entry containing an IPv6 Prefix
       identical to that of the IPv6 address being translated.  The IPv4
       Prefix and IPv6 Prefix values of the EAM entry found is from now
       on referred to as EAM4 and EAM6, respectively.

   2.  If no matching EAM entry is found, the EAM algorithm is aborted.
       The SIIT implementation MUST proceed to translate the address in
       accordance with [RFC6145] (and its updates).

   3.  The prefix bits of EAM6 are removed from IPv6 address being
       translated.  The remaining suffix bits from the IPv6 address
       being translated are stored in a temporary buffer.

   4.  The prefix bits of EAM4 are prepended to the temporary buffer.





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   5.  If the temporary buffer at this point does not contain a 32-bit
       value, any trailing bits are discarded so that the buffer is
       reduced to a length of 32 bits.

   6.  The contents of the temporary buffer is the translated IPv4
       address.

4.  Lack of Checksum Neutrality

   When one or both of the address fields in an IP/ICMP packet are
   translated according to EAM, the translation can not be relied upon
   to be checksum neutral, even if the well-known prefix 64:ff9b::/96 is
   used.  This consideration is discussed in more detail in Section 4.1
   of [RFC6052].

5.  Security Considerations

   The EAM algorithm does not introduce any new security issues beyond
   those that are already discussed in Section 7 of [RFC6145].

6.  IANA Considerations

   This draft makes no request of the IANA.  The RFC Editor may remove
   this section prior to publication.

7.  Acknowledgements

   This document was conceived due to comments made by Dave Thaler in
   the v6ops session at IETF 91 as well as e-mail discussions between
   Fred Baker and the author.

   Valuable reviews, suggestions, and other feedback was given by
   Cameron Byrne, Brian E Carpenter, Alberto Leiva, and Andrew
   Yourtchenko.

8.  References

8.1.  Normative References

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

   [RFC6052]  Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
              Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
              October 2010.

   [RFC6145]  Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
              Algorithm", RFC 6145, April 2011.



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8.2.  Informative References

   [I-D.anderson-v6ops-siit-dc]
              tore, t., "SIIT-DC: Stateless IP/ICMP Translation for IPv6
              Data Centre Environments", draft-anderson-v6ops-siit-dc-01
              (work in progress), October 2014.

   [RFC4213]  Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
              for IPv6 Hosts and Routers", RFC 4213, October 2005.

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862, September 2007.

   [RFC6144]  Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
              IPv4/IPv6 Translation", RFC 6144, April 2011.

   [RFC6219]  Li, X., Bao, C., Chen, M., Zhang, H., and J. Wu, "The
              China Education and Research Network (CERNET) IVI
              Translation Design and Deployment for the IPv4/IPv6
              Coexistence and Transition", RFC 6219, May 2011.

   [RFC6877]  Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT:
              Combination of Stateful and Stateless Translation", RFC
              6877, April 2013.

   [RFC7335]  Byrne, C., "IPv4 Service Continuity Prefix", RFC 7335,
              August 2014.

Appendix A.  Use Cases

   The following subsections lists some use cases that at the time of
   writing leverage SIIT with the EAM algorithm.

A.1.  464XLAT

   When the CLAT component in the 464XLAT [RFC6877] architecture does
   not have a dedicated IPv6 prefix assigned, it may instead use "one
   interface IPv6 address that is claimed by the CLAT".  This IPv6
   address might not be IPv4-translatable.  If this is the case, the
   CLAT essentially implements the EAM algorithm using an EAMT as
   follows (assuming the CLAT's IPv4 address is picked from the IPv4
   Service Continuity Prefix [RFC7335]):

                     Example EAMT for an 464XLAT CLAT







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           +---+--------------+-------------------------------+
           | # | IPv4 Prefix  |          IPv6 Prefix          |
           +---+--------------+-------------------------------+
           | 1 | 192.0.0.1/32 | CLAT_claimed_IPv6_address/128 |
           +---+--------------+-------------------------------+

                                 Figure 2

   In this particular use case, the EAM algorithm is used to translate
   IPv6 destination addresses to IPv4, and conversely, IPv4 source
   addresses to IPv6.  Other addresses are translated using [RFC6052].
   Note that this is the exact opposite of the SIIT-DC use case
   (Appendix A.3).

A.2.  IVI

   IVI [RFC6219] describes a stateless translation model that embeds
   IPv4 addresses in a 40-bit translation prefix where bits 33-40 are
   required to be 1.  The embedded IPv4 address is located in bits 41-72
   of the IPv6 address.  Bits 73-128 are required to be 0.

   The location of the eight least significant IPv4 address bits makes
   the IVI address mapping differ from [RFC6052].

                           Example EAMT for IVI

                 +---+-------------+--------------------+
                 | # | IPv4 Prefix |    IPv6 Prefix     |
                 +---+-------------+--------------------+
                 | 1 | 0.0.0.0/0   | 2001:db8:ff00::/40 |
                 +---+-------------+--------------------+

                                 Figure 3

   In this particular use case, all addresses are translated according
   to the EAM algorithm.  In other words, [RFC6052] mapping is not used
   at all.

A.3.  SIIT-DC












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   SIIT-DC [I-D.anderson-v6ops-siit-dc] describes the use of SIIT to
   facilitate connectivity from the IPv4 Internet to services hosted in
   an IPv6-only data centre.  In order to avoid the constraints relating
   to the use of IPv4-translatable IPv6 addresses discussed in Section 2
   the stateless IPv4/IPv6 translators are provisioned with an EAMT
   containing one entry per IPv6-only service that are to be made
   available from the IPv4 Internet, for example (assuming
   2001:db8:aaaa::1 and 2001:db8:bbbb::1 are assigned to load balancers
   or servers that provides the IPv6-only services in question):

                         Example EAMT for SIIT-DC

                +---+--------------+----------------------+
                | # | IPv4 Prefix  |     IPv6 Prefix      |
                +---+--------------+----------------------+
                | 1 | 192.0.2.1/32 | 2001:db8:aaaa::1/128 |
                | 2 | 192.0.2.2/32 | 2001:db8:bbbb::1/128 |
                +---+--------------+----------------------+

                                 Figure 4

   In this particular use case, the EAM algorithm is used to translate
   IPv4 destination addresses to IPv6, and conversely, IPv6 source
   addresses to IPv4.  Other addresses are translated using [RFC6052].
   Note that this is the exact opposite of the 464XLAT use case
   (Appendix A.1).

Appendix B.  Example IP Address Translations

   Figure 5 demonstrates how a set of example IP addresses are
   translated given the example EAMT in Figure 1.  Implementors may use
   the examples given to develop test cases to validate correct
   operation.  Note that the address translations are bidirectional, so
   a single row in the table describes two address translations: IPv4 to
   IPv6, and IPv6 to IPv4.

   It is also assumed that the [RFC6052] translation prefix is
   configured to be 64:ff9b::/96.

                      Example IP Address Translations











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     +--------------+------------------------+-----------------------+
     | IPv4 Address |      IPv6 Address      |        Comment        |
     +--------------+------------------------+-----------------------+
     | 192.0.2.1    | 2001:db8:aaaa::        | According to EAM #1   |
     | 192.0.2.2    | 2001:db8:bbbb::b       | According to EAM #2   |
     | 192.0.2.16   | 2001:db8:cccc::        | According to EAM #3   |
     | 192.0.2.24   | 2001:db8:cccc::8       | According to EAM #3   |
     | 192.0.2.31   | 2001:db8:cccc::f       | According to EAM #3   |
     | 192.0.2.128  | 2001:db8:dddd::        | According to EAM #4   |
     | 192.0.2.152  | 2001:db8:dddd:0:6000:: | According to EAM #4   |
     | 192.0.2.183  | 2001:db8:dddd:0:dc00:: | According to EAM #4   |
     | 192.0.2.191  | 2001:db8:dddd:0:fc00:: | According to EAM #4   |
     | 192.0.2.193  | 64:ff9b::1             | According to EAM #5   |
     | 192.0.2.200  | 64:ff9b::c000:2c8      | According to RFC 6052 |
     +--------------+------------------------+-----------------------+

                                 Figure 5

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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