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Versions: 00 draft-ietf-v6ops-siit-dc-2xlat

IPv6 Operations                                              T. Anderson
Internet-Draft                                            Redpill Linpro
Intended status: Standards Track                      September 15, 2014
Expires: March 19, 2015


                     SIIT-DC: Dual Translation Mode
                 draft-anderson-v6ops-siit-dc-2xlat-00

Abstract

   This document describes an extension of the SIIT-DC
   [I-D.anderson-v6ops-siit-dc] architecture, which allows applications
   that are incompatible with IPv6, SIIT-DC and/or Network Address
   Translation in general to operate correctly in an SIIT-DC
   environment.  This is accomplished by introducing a new component
   called a SIIT-DC Host Agent, which reverses the translations made by
   an SIIT-DC Gateway.  The application is thus provided with seemingly
   native IPv4 connectivity.

   The reader is expected to be familiar with the SIIT-DC architecture
   described in [I-D.anderson-v6ops-siit-dc].

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
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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   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 March 19, 2015.

Copyright Notice

   Copyright (c) 2014 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



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   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
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  SIIT-DC Host Agent Specification  . . . . . . . . . . . . . .   4
   4.  Architectural Overview  . . . . . . . . . . . . . . . . . . .   4
   5.  Deployment Considerations . . . . . . . . . . . . . . . . . .   6
     5.1.  IPv6 Path MTU . . . . . . . . . . . . . . . . . . . . . .   6
     5.2.  IPv4 MTU  . . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   7.  Requirements Language . . . . . . . . . . . . . . . . . . . .   6
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
     9.1.  Address Spoofing  . . . . . . . . . . . . . . . . . . . .   7
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     10.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   SIIT-DC [I-D.anderson-v6ops-siit-dc] describes an architecture where
   IPv4-only users can access IPv6-only services through a stateless
   translation gateway.  However, this only works for applications that
   are compatible with Network Address Translation (NAT), due to the
   fact that the SIIT-DC Gateway will rewrite the addresses in the IP
   header as part of the translation process.  SIIT-DC will also fail to
   work correctly for applications that make use of legacy IPv4-only
   socket calls.

   This document remedies this problem by defining an extension to SIIT-
   DC.  Translations performed by the SIIT-DC Gateway will also be done
   in reverse by an SIIT-DC Host Agent running on the server.  The
   resulting IPv4 packets are then passed to the application.  This way,
   the application will be able to use legacy IPv4-only socket calls and
   /or include references to its own IPv4 address in the application
   payload, while maintaining correct operation.

   The approach is heavily inspired by and very similar to 464XLAT
   [RFC6877].  The SIIT-DC Host Agent described in this document is
   almost identical to the CLAT component in 464XLAT, except for the



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   fact that it will be located on a server, rather than on the
   customer-side node.  Furthermore, an SIIT-DC Host Agent uses
   statically configured public IP addresses, whereas a 464XLAT CLAT
   uses a dynamic IPv6 address and a private IPv4 address.  The SIIT-DC
   Gateway described in [I-D.anderson-v6ops-siit-dc] is used instead of
   the PLAT described by 464XLAT.

2.  Terminology

   This document makes use of the following terms:

   IPv4 Service Address  A public IPv4 address with which IPv4-only
      clients will communicate.  This communication will be translated
      to IPv6 by the SIIT-DC Gateway.

   IPv6 Service Address  A public IPv6 address assigned to a server or
      application in the IPv6 network.  IPv6-only and dual stacked
      clients communicates with this address directly without invoking
      SIIT-DC.  IPv4-only clients also communicate with this address
      through the SIIT-DC Gateway and via an IPv4 Service Address.

   SIIT-DC Host Agent  A logical function very similar to an SIIT-DC
      Gateway that resides on a server and provides virtual IPv4
      connectivity to applications, by performing
      [I-D.anderson-v6ops-siit-dc] translation on packets passing
      through it.  See Section 3.

   SIIT-DC Gateway  A device or a logical function that translates
      between IPv4 and IPv6 in accordance with
      [I-D.anderson-v6ops-siit-dc].

   Static Address Mapping  A bi-directional mapping between an IPv4
      Service Address and an IPv6 Service Address configured in the
      SIIT-DC Gateway.  When translating between IPv4 and IPv6, the
      SIIT-DC Gateway changes the adddress fields in the translated
      packet's IP header according to any matching Static Address
      Mapping.

   Translation Prefix  An IPv6 prefix into which the entire IPv4 address
      space is mapped.  This prefix is routed to the SIIT-DC Gateway's
      IPv6 interface.  It is either an Network-Specific Prefix or a
      Well-Known Prefix as specified in [RFC6052].  When translating
      between IPv4 and IPv6, the SIIT-DC Gateway prepends or strips the
      Translation Prefix from the address fields in the translated
      packet's IP header, unless a Static Address Mapping exists for the
      IP address in question.





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3.  SIIT-DC Host Agent Specification

   The SIIT-DC Host Agent runs on the servers hosting application which
   do not work correctly with the SIIT-DC architecture as specified by
   [I-D.anderson-v6ops-siit-dc].  Its task is the performing the exact
   same packet translation as the SIIT-DC Gateway, only in reverse.  It
   therefore shares the same implementation requirements as the SIIT-DC
   Gateway defined in Section 4 of [I-D.anderson-v6ops-siit-dc], with
   one exception: The SIIT-DC Host Agent is not required to support
   configuring an arbitrary number of Static Address Mappings, but it
   must support at least one.

   The SIIT-DC Host Agent must be configured with a Static Address
   Mapping that corresponds exactly with the same mapping found on the
   SIIT-DC Gateway.  The IPv4 address of the Static Address Mapping
   (i.e., the IPv4 Service Address) must be configured on a virtual
   network interface which applications running on the server can bind
   to, and the server is expected to install a default IPv4 route
   poining to this virtual IPv4 interface.  The IPv6 address of the
   Static Address Mapping must be a secondary address that is routed to
   the server by the IPv6 network.  The server must forward all packets
   it receives destined for this IPv6 address to the SIIT-DC Host Agent.

4.  Architectural Overview

   The following figure shows how an application (that is presumably
   incompatible with standard SIIT-DC) is being made available to the
   IPv4 Internet on the IPv4 address 192.0.2.4.  The application will be
   able to know that this is its local address and thus be able to
   provide correct references to it in application payload.

   The figure also shows how the same application is available over IPv6
   on its IPv6 Service Address 2001:db8:12:34::3.  This is included in
   order to illustrate how native IPv6 connectivity is not impacted by
   the SIIT-DC Host Agent, and also to illustrate how the address
   assigned to the SIIT-DC Host Agent (2001:db8:12:34::4) is separate
   from the primary IPv6 address of the server.  It is however important
   to note that the application in question does not have to be dual-
   stack capable at all.  IPv4-only applications would also be able to
   operate behind a SIIT-DC Host Agent in the exact same manner.

   Note that the figure below could be considered a more detailed view
   of Customer A's FTP server from the example topology figure in
   Appendix A of I-D.anderson-v6ops-siit-dc
   [I-D.anderson-v6ops-siit-dc].  Both figures intentionally use the
   exact same example IP addresses and prefixes.

                      SIIT-DC Host Agent Architecture



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             +-------------------+         +----------------+
             | IPv6-capable user |         | IPv4-only user |
             | ================= |         | ============== |
             |                   |         |                |
             +-<2001:db8::ab:cd>-+         +-<203.0.113.50>-+
                 |                                  |
                 |                                  |
              (the IPv6 internet)         (the IPv4 Internet)
                 |                                  |
                 |                                  |
                 |        +------------------<192.0.2.0/24>-+
                 |        |                                 |
                 |        |         SIIT-DC Gateway         |
                 |        |         ===============         |
                 |        |                                 |
                 |        |       Translation Prefix:       |
                 |        |         2001:db8:46::/96        |
                 |        |                                 |
                 |        |     Static Address Mapping:     |
                 |        | 192.0.2.4 <=> 2001:db8:12:34::4 |
                 |        |                                 |
                 |        +--------------<2001:db8:46::/96>-+
                 |                               |
                 |                               |
                (the IPv6-only data centre network)
                 |                               |
                 |                               |
           +--<2001:db8:12:34::3>-------<2001:db8:12:34::4>---+
           |     |                               |            |
           |     |          IPv6-only server     |            |
           |     |          ================     |            |
           |     |                               |            |
           |     |        +-------------<2001:db8:12:34::4>-+ |
           |     |        |                                 | |
           |     |        |       SIIT-DC Host Agent        | |
           |     |        |       ==================        | |
           |     |        |                                 | |
           |     |        |       Translation Prefix:       | |
           |     |        |         2001:db8:46::/96        | |
           |     |        |                                 | |
           |     |        |     Static Address Mapping:     | |
           |     |        | 192.0.2.4 <=> 2001:db8:12:34::4 | |
           |     |        |                                 | |
           |     |        +---------------------<192.0.2.4>-+ |
           |     |                                   |        |
           |     |                                   |        |
           | +-[2001:db8:12:34::3]--------------[192.0.2.4]-+ |
           | |      AF_INET6                      AF_INET   | |



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           | |                                              | |
           | |           Dual-stacked application           | |
           | |                                              | |
           | +----------------------------------------------+ |
           +--------------------------------------------------+

                                 Figure 1

5.  Deployment Considerations

5.1.  IPv6 Path MTU

   The IPv6 Path MTU between the SIIT-DC Host Agent and the SIIT-DC
   Gateway will typically be larger than the default value defined in
   Section 4 of [RFC6145] (1280), as it will typically contained within
   a single administrative domain.  Therefore, it is recommended that
   the IPv6 Path MTU configured in the SIIT-DC Host Agent is raised
   accordingly.  It is RECOMMENDED that the SIIT-DC Host Agent and the
   SIIT-DC Gateway use identical configured IPv6 Path MTU values.

5.2.  IPv4 MTU

   In order to avoid fragmentation, it is RECOMMENDED that the virtual
   IPv4 interface is configured with an MTU value identical to the
   configured IPv6 Path MTU - 20.  This ensures that the application may
   do its part in avoiding IP-level fragmentation from occurring, e.g.,
   by segmenting/fragmenting outbound packets at the application layer,
   and advertising the maximum size its peer may use for inbound packets
   (e.g., through the use of the TCP MSS option).

6.  Acknowledgements

   The author would like to especially thank the authors of 464XLAT
   [RFC6877]: Masataka Mawatari, Masanobu Kawashima, and Cameron Byrne.
   The architecture described by this document is merely an adaptation
   of their work to a data centre environment, and could not have
   happened without them.

   The author would like also to thank the following individuals for
   their contributions, suggestions, corrections, and criticisms: Fred
   Baker, Tobias Brox, [YOUR NAME GOES HERE].

7.  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 [RFC2119].




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8.  IANA Considerations

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

9.  Security Considerations

   This section discusses security considerations specific to the use of
   a SIIT-DC Host Agent.  See the Security Considerations in I-D
   .anderson-v6ops-siit-dc [I-D.anderson-v6ops-siit-dc] for additional
   security considerations applicable to the SIIT-DC architecture in
   general.

9.1.  Address Spoofing

   If the SIIT-DC Host Agent receives an IPv4 packet from the
   application from a different source address than the one it has a
   Static Address Mapping for, the both the source and destination
   addresses will be rewritten according to [RFC6052].  After undergoing
   the reverse translation in the SIIT-DC Gateway, the resulting IPv4
   packet routed to the IPv4 network will have a spoofed IPv4 source
   address.  The SIIT-DC Host Agent should therefore ensure that ingress
   filtering (cf. BCP38 [RFC2827]) is used on the SIIT-DC Host Agent's
   IPv4 interface, so that such packets are immediately discarded.

   If the SIIT-DC Host Agent receives an IPv6 packet with both the
   source and destination address equal to the one it has a Static
   Address Mapping for, the resulting packet would appear to the
   application as locally generated, as both the source address and the
   destination address will be the same address as the one configured on
   the virtual IPv4 interface.  This could trick the application into
   thinking this packet came from a trusted source, and give elevated
   privileges accordingly.  To prevent this, the SIIT-DC Host Agent
   should discard any received IPv6 packets that have a source address
   that is equal either to either the IPv4 (after undergoing [RFC6052]
   translation) or the IPv6 address in the Static Address Mapping.

10.  References

10.1.  Normative References

   [I-D.anderson-v6ops-siit-dc]
              Anderson, T., "SIIT-DC: Stateless IP/ICMP Translation in
              IPv6 Data Centre Environments", draft-anderson-v6ops-siit-
              dc-00 (work in progress), September 2014.

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



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10.2.  Informative References

   [RFC2827]  Ferguson, P. and D. Senie, "Network Ingress Filtering:
              Defeating Denial of Service Attacks which employ IP Source
              Address Spoofing", BCP 38, RFC 2827, May 2000.

   [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.

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

Author's Address

   Tore Anderson
   Redpill Linpro
   Vitaminveien 1A
   0485 Oslo
   NORWAY

   Phone: +47 959 31 212
   Email: tore@redpill-linpro.com
























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