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An Incremental Carrier-Grade NAT (CGN) for IPv6 Transition
RFC 6264

Internet Engineering Task Force (IETF)                          S. Jiang
Request for Comments: 6264                                        D. Guo
Category: Informational                                           Huawei
ISSN: 2070-1721                                             B. Carpenter
                                                  University of Auckland
                                                               June 2011

       An Incremental Carrier-Grade NAT (CGN) for IPv6 Transition

Abstract

   Global IPv6 deployment was slower than originally expected.  As IPv4
   address exhaustion approaches, IPv4 to IPv6 transition issues become
   more critical and less tractable.  Host-based transition mechanisms
   used in dual-stack environments cannot meet all transition
   requirements.  Most end users are not sufficiently expert to
   configure or maintain host-based transition mechanisms.  Carrier-
   Grade NAT (CGN) devices with integrated transition mechanisms can
   reduce the operational changes required during the IPv4 to IPv6
   migration or coexistence period.

   This document proposes an incremental CGN approach for IPv6
   transition.  It can provide IPv6 access services for IPv6 hosts and
   IPv4 access services for IPv4 hosts while leaving much of a legacy
   ISP network unchanged during the initial stage of IPv4 to IPv6
   migration.  Unlike CGN alone, incremental CGN also supports and
   encourages smooth transition towards dual-stack or IPv6-only ISP
   networks.  An integrated configurable CGN device and an adaptive home
   gateway (HG) device are described.  Both are reusable during
   different transition phases, avoiding multiple upgrades.  This
   enables IPv6 migration to be incrementally achieved according to real
   user requirements.

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.

Jiang, et al.                 Informational                     [Page 1]
RFC 6264           Incremental CGN for IPv6 Transition         June 2011

   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/rfc6264.

Copyright Notice

   Copyright (c) 2011 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 ....................................................2
   2. An Incremental CGN Approach .....................................4
      2.1. Incremental CGN Approach Overview ..........................4
      2.2. Choice of Tunneling Technology .............................5
      2.3. Behavior of Dual-Stack Home Gateway ........................6
      2.4. Behavior of Dual-Stack CGN .................................6
      2.5. Impact for Existing Hosts and Unchanged Networks ...........7
      2.6. IPv4/IPv6 Intercommunication ...............................7
      2.7. Discussion .................................................8
   3. Smooth Transition towards IPv6 Infrastructure ...................8
   4. Security Considerations ........................................10
   5. Acknowledgements ...............................................10
   6. References .....................................................10
      6.1. Normative References ......................................10
      6.2. Informative References ....................................11

1.  Introduction

   Global IPv6 deployment did not happen as was forecast 10 years ago.
   Network providers were hesitant to make the first move while IPv4 was
   and is still working well.  However, IPv4 address exhaustion is
   imminent.  The dynamically updated IPv4 Address Report [IPUSAGE] has
   analyzed this issue. IANA unallocated address pool exhaustion
   occurred in February 2011, and at the time of publication, the site

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