6to4 Provider Managed Tunnels
RFC 6732

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Independent Submission                                 V. Kuarsingh, Ed.
Request for Comments: 6732                         Rogers Communications
Category: Informational                                           Y. Lee
ISSN: 2070-1721                                                  Comcast
                                                              O. Vautrin
                                                        Juniper Networks
                                                          September 2012

                     6to4 Provider Managed Tunnels

Abstract

   6to4 Provider Managed Tunnels (6to4-PMT) provide a framework that can
   help manage 6to4 tunnels operating in an anycast configuration.  The
   6to4-PMT framework is intended to serve as an option for operators to
   help improve the experience of 6to4 operation when conditions of the
   network may provide sub-optimal performance or break normal 6to4
   operation. 6to4-PMT supplies a stable provider prefix and forwarding
   environment by utilizing existing 6to4 relays with an added function
   of IPv6 Prefix Translation.  This operation may be particularly
   important in NAT444 infrastructures where a customer endpoint may be
   assigned a non-RFC1918 address, thus breaking the return path for
   anycast-based 6to4 operation.  6to4-PMT has been successfully used in
   a production network, implemented as open source code, and
   implemented by a major routing vendor.

Status of This Memo

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

   This is a contribution to the RFC Series, independently of any other
   RFC stream.  The RFC Editor has chosen to publish this document at
   its discretion and makes no statement about its value for
   implementation or deployment.  Documents approved for publication by
   the RFC Editor are not 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/rfc6732.

Kuarsingh, et al.             Informational                     [Page 1]
RFC 6732              6to4 Provider Managed Tunnels       September 2012

Copyright Notice

   Copyright (c) 2012 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.

Table of Contents

   1. Introduction ....................................................3
   2. Motivation ......................................................3
   3. 6to4 Provider Managed Tunnels ...................................5
      3.1. 6to4 Provider Managed Tunnel Model .........................5
      3.2.  Traffic Flow ..............................................5
      3.3.  Prefix Translation ........................................6
      3.4.  Translation State .........................................7
   4. Deployment Considerations and Requirements ......................7
      4.1. Customer Opt-Out ...........................................7
      4.2. Shared CGN Space Considerations ............................8
      4.3. End-to-End Transparency ....................................8
      4.4. Path MTU Discovery Considerations ..........................9
      4.5. Checksum Management ........................................9
      4.6. Application Layer Gateways .................................9
      4.7. Routing Requirements .......................................9
      4.8. Relay Deployments .........................................10
   5. Security Considerations ........................................10
   6. Acknowledgements ...............................................10
   7. References .....................................................11
      7.1. Normative References ......................................11
      7.2. Informative References ....................................11

Kuarsingh, et al.             Informational                     [Page 2]
RFC 6732              6to4 Provider Managed Tunnels       September 2012

1.  Introduction

   6to4 [RFC3056] tunneling, along with the anycast operation described
   in [RFC3068], is widely deployed in modern Operating Systems and
   off-the-shelf gateways sold throughout retail and Original Equipment
   Manufacturer (OEM) channels.  Anycast-based 6to4 [RFC3068] allows for
   tunneled IPv6 connectivity through IPv4 clouds without explicit
   configuration of a relay address.  Since the overall system utilizes
   anycast forwarding in both directions, flow paths are difficult to