Stateless IP/ICMP Translation for IPv6 Internet Data Center Environments (SIIT-DC): Dual Translation Mode
RFC 7756

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Internet Engineering Task Force (IETF)                       T. Anderson
Request for Comments: 7756                                Redpill Linpro
Category: Informational                                      S. Steffann
ISSN: 2070-1721                              S.J.M. Steffann Consultancy
                                                           February 2016

      Stateless IP/ICMP Translation for IPv6 Internet Data Center
             Environments (SIIT-DC): Dual Translation Mode

Abstract

   This document describes an extension of the Stateless IP/ICMP
   Translation for IPv6 Internet Data Center Environments (SIIT-DC)
   architecture, which allows applications, protocols, or nodes that are
   incompatible with IPv6 and/or Network Address Translation to operate
   correctly with SIIT-DC.  This is accomplished by introducing a new
   component called an SIIT-DC Edge Relay, which reverses the
   translations made by an SIIT-DC Border Relay.  The application and/or
   node is thus provided with seemingly native IPv4 connectivity that
   provides end-to-end address transparency.

   The reader is expected to be familiar with the SIIT-DC architecture
   described in RFC 7755.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7756.

Anderson & Steffann           Informational                     [Page 1]
RFC 7756             SIIT-DC: Dual Translation Mode        February 2016

Copyright Notice

   Copyright (c) 2016 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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Edge Relay Description  . . . . . . . . . . . . . . . . . . .   5
     3.1.  Node-Based Edge Relay . . . . . . . . . . . . . . . . . .   6
     3.2.  Network-Based Edge Relay  . . . . . . . . . . . . . . . .   7
       3.2.1.  Edge Relay "on a Stick" . . . . . . . . . . . . . . .   8
       3.2.2.  Edge Relay That Bridges IPv6 Packets  . . . . . . . .   9
   4.  Deployment Considerations . . . . . . . . . . . . . . . . . .   9
     4.1.  IPv6 Path MTU . . . . . . . . . . . . . . . . . . . . . .   9
     4.2.  IPv4 MTU  . . . . . . . . . . . . . . . . . . . . . . . .  10
     4.3.  IPv4 Identification Header  . . . . . . . . . . . . . . .  10
   5.  Intra-IDC IPv4 Communication  . . . . . . . . . . . . . . . .  10
     5.1.  Hairpinning by the SIIT-DC Border Relay . . . . . . . . .  11
     5.2.  Additional EAMs Configured in Edge Relay  . . . . . . . .  12
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Appendix A.  Examples: Network-Based IPv4 Connectivity  . . . . .  16
     A.1.  Subnet with IPv4 Service Addresses  . . . . . . . . . . .  16
     A.2.  Subnet with Unrouted IPv4 Addresses . . . . . . . . . . .  16
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

Anderson & Steffann           Informational                     [Page 2]
RFC 7756             SIIT-DC: Dual Translation Mode        February 2016

1.  Introduction

   SIIT-DC [RFC7755] describes an architecture where IPv4-only users can
   access IPv6-only services through a stateless translator called an
   SIIT-DC Border Relay (BR).  This approach has certain limitations,
   however.  In particular, the following cases will work poorly or not
   at all:

   o  Application protocols that do not support NAT (i.e., the lack of
      end-to-end transparency of IP addresses).