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Native IPv6 behind IPv4-to-IPv4 NAT Customer Premises Equipment (6a44)
RFC 6751

Independent Submission                                   R. Despres, Ed.
Request for Comments: 6751                                     RD-IPtech
Category: Experimental                                      B. Carpenter
ISSN: 2070-1721                                        Univ. of Auckland
                                                                 D. Wing
                                                                   Cisco
                                                                S. Jiang
                                           Huawei Technologies Co., Ltd.
                                                            October 2012

 Native IPv6 behind IPv4-to-IPv4 NAT Customer Premises Equipment (6a44)

Abstract

   In customer sites having IPv4-only Customer Premises Equipment (CPE),
   Teredo (RFC 4380, RFC 5991, RFC 6081) provides last-resort IPv6
   connectivity.  However, because it is designed to work without the
   involvement of Internet Service Providers, it has significant
   limitations (connectivity between IPv6 native addresses and Teredo
   addresses is uncertain; connectivity between Teredo addresses fails
   for some combinations of NAT types).  6a44 is a complementary
   solution that, being based on ISP cooperation, avoids these
   limitations.  At the beginning of 6a44 IPv6 addresses, it replaces
   the Teredo well-known prefix, present at the beginning of Teredo IPv6
   addresses, with network-specific /48 prefixes assigned by local ISPs
   (an evolution similar to that from 6to4 to 6rd (IPv6 Rapid Deployment
   on IPv4 Infrastructures)).  The specification is expected to be
   complete enough for running code to be independently written and the
   solution to be incrementally deployed and used.

Despres, et al.               Experimental                      [Page 1]
RFC 6751          Native IPv6 behind NAT44 CPEs (6a44)      October 2012

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for examination, experimental implementation, and
   evaluation.

   This document defines an Experimental Protocol for the Internet
   community.  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/rfc6751.

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.

Despres, et al.               Experimental                      [Page 2]
RFC 6751          Native IPv6 behind NAT44 CPEs (6a44)      October 2012

Table of Contents

   1. Introduction ....................................................3
   2. Requirements Language ...........................................5
   3. Definitions .....................................................5
   4. Design Goals, Requirements, and Model of Operation ..............7
      4.1. Hypotheses about NAT Behavior ..............................7
      4.2. Native IPv6 Connectivity for Unmanaged Hosts behind
           NAT44s .....................................................7
      4.3. Operational Requirements ...................................8
      4.4. Model of Operation .........................................9
   5. 6a44 Addresses .................................................12
   6. Specification of Clients and Relays ............................14
      6.1. Packet Formats ............................................14
      6.2. IPv6 Packet Encapsulations ................................14
      6.3. 6a44 Bubbles ..............................................14
      6.4. MTU Considerations ........................................16
      6.5. 6a44 Client Specification .................................16
           6.5.1. Tunnel Maintenance .................................16
           6.5.2. Client Transmission ................................19
           6.5.3. Client Reception ...................................20
      6.6. 6a44 Relay Specification ..................................23

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