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Internet Engineering Task Force (IETF)                         W. George
Request for Comments: 6540                             Time Warner Cable
BCP: 177                                                       C. Donley
Category: Best Current Practice                                CableLabs
ISSN: 2070-1721                                          C. Liljenstolpe
                                                     Big Switch Networks
                                                               L. Howard
                                                       Time Warner Cable
                                                              April 2012

             IPv6 Support Required for All IP-Capable Nodes


   Given the global lack of available IPv4 space, and limitations in
   IPv4 extension and transition technologies, this document advises
   that IPv6 support is no longer considered optional.  It also cautions
   that there are places in existing IETF documents where the term "IP"
   is used in a way that could be misunderstood by implementers as the
   term "IP" becomes a generic that can mean IPv4 + IPv6, IPv6-only, or
   IPv4-only, depending on context and application.

Status of This Memo

   This memo documents an Internet Best Current Practice.

   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).  Further information on
   BCPs is available in 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

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RFC 6540                      IPv6-Required                   April 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.  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. Clarifications and Recommendation ...............................3
   3. Acknowledgements ................................................4
   4. Security Considerations .........................................5
   5. Informative References ..........................................5

1.  Introduction

   IP version 4 (IPv4) has served to connect public and private hosts
   all over the world for over 30 years.  However, due to the success of
   the Internet in finding new and innovative uses for IP networking,
   billions of hosts are now connected via the Internet and require
   unique addressing.  This demand has led to the exhaustion of the IANA
   global pool of unique IPv4 addresses [IANA-EXHAUST], and will be
   followed by the exhaustion of the free pools for each Regional
   Internet Registry (RIR), the first of which is APNIC [APNIC-EXHAUST].
   While transition technologies and other means to extend the lifespan
   of IPv4 do exist, nearly all of them come with trade-offs that
   prevent them from being optimal long-term solutions when compared
   with deployment of IP version 6 (IPv6) as a means to allow continued
   growth on the Internet.  See [RFC6269] and [NAT444-IMPACTS] for some
   discussion on this topic.

   IPv6 [RFC1883] was proposed in 1995 as, among other things, a
   solution to the limitations on globally unique addressing that IPv4's
   32-bit addressing space represented, and has been under continuous
   refinement (e.g., [RFC2460]) and deployment ever since.  The
   exhaustion of IPv4 and the continued growth of the Internet worldwide
   have created the driver for widespread IPv6 deployment.

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RFC 6540                      IPv6-Required                   April 2012

   However, the IPv6 deployment necessary to reduce reliance on IPv4 has
   been hampered by a lack of ubiquitous hardware and software support
   throughout the industry.  Many vendors, especially in the consumer
   space, have continued to view IPv6 support as optional.  Even today,
   they are still selling "IP-capable" or "Internet-Capable" devices
   that are not IPv6-capable, which has continued to push out the point
   at which the natural hardware refresh cycle will significantly
   increase IPv6 support in the average home or enterprise network.
   They are also choosing not to update existing software to enable IPv6
   support on software-updatable devices, which is a problem because it
   is not realistic to expect that the hardware refresh cycle will
   single-handedly purge IPv4-only devices from the active network in a
   reasonable amount of time.  This is a significant problem, especially
   in the consumer space, where the network operator often has no
   control over the hardware the consumer chooses to use.  For the same
   reason that the average consumer is not making a purchasing decision
   based on the presence of IPv6 support in their Internet-capable
   devices and services, consumers are unlikely to replace their still-
   functional Internet-capable devices simply to add IPv6 support --
   they don't know or don't care about IPv6; they simply want their
   devices to work as advertised.

   This lack of support is making the eventual IPv6 transition
   considerably more difficult, and drives the need for expensive and
   complicated transition technologies to extend the life of IPv4-only
   devices as well as to eventually interwork IPv4-only and IPv6-only
   hosts.  While IPv4 is expected to coexist on the Internet with IPv6
   for many years, a transition from IPv4 as the dominant Internet
   Protocol version towards IPv6 as the dominant Internet Protocol
   version will need to occur.  The sooner the majority of devices
   support IPv6, the less protracted this transition period will be.

2.  Clarifications and Recommendation

   To ensure interoperability and proper function after IPv4 exhaustion,
   support for IPv6 is virtually a requirement.  Rather than update the
   existing IPv4 protocol specification standards to include IPv6, the
   IETF has defined a completely separate set of standalone documents
   that cover IPv6.  Therefore, implementers are cautioned that a
   distinction must be made between IPv4 and IPv6 in some IETF documents
   where the term "IP" is used generically.  Current requirements for
   IPv6 support can be found in [RFC6204] and [RFC6434].  Each of these
   documents contains specific information, requirements, and references
   to other Draft and Proposed Standards governing many aspects of IPv6

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RFC 6540                      IPv6-Required                   April 2012

   Many of the IETF's early documents use the generic term "IP"
   synonymously with the more specific "IPv4".  Some examples of this
   potential confusion can be found in [RFC1812], especially in
   Sections 1, 2, and 4.  Since RFC 1812 is an IPv4 router
   specification, the generic use of IP in this standard may cause
   confusion as the term "IP" can now be interpreted to mean
   IPv4 + IPv6, IPv6-only, or IPv4-only.  Additionally, [RFC1122] is no
   longer a complete definition of "IP" or the Internet Protocol suite
   by itself, because it does not include IPv6.  For example,
   Section 3.1 does not contain references to the equivalent standards
   for IPv6 for the Internet layer, Section 3.2 is a protocol
   walk-through for IPv4 only, and Section explicitly requires
   that an IP datagram whose version number is not 4 be discarded, which
   would be detrimental to IPv6 forwarding.  Additional instances of
   this type of problem exist that are not discussed here.  Since
   existing RFCs say "IP" in places where they may mean IPv4,
   implementers are cautioned to ensure that they know whether a given
   standard is inclusive or exclusive of IPv6.  To ensure
   interoperability, implementers building IP nodes will need to support
   both IPv4 and IPv6.  If the standard does not include an integral
   definition of both IPv4 and IPv6, implementers need to use the other
   informative references in this document as companion guidelines for
   proper IPv6 implementations.

   To ensure interoperability and flexibility, the best practices are as

   o  New IP implementations must support IPv6.

   o  Updates to current IP implementations should support IPv6.

   o  IPv6 support must be equivalent or better in quality and
      functionality when compared to IPv4 support in a new or updated IP

   o  New and updated IP networking implementations should support IPv4
      and IPv6 coexistence (dual-stack), but must not require IPv4 for
      proper and complete function.

   o  Implementers are encouraged to update existing hardware and
      software to enable IPv6 wherever technically feasible.

3.  Acknowledgements

   Thanks to the following people for their reviews and comments: Marla
   Azinger, Brian Carpenter, Victor Kuarsingh, Jari Arkko, Scott Brim,
   Margaret Wasserman, Joe Touch, Fred Baker, Benson Schliesser, Eric
   Rosen, David Harrington, and Wesley Eddy.

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RFC 6540                      IPv6-Required                   April 2012

4.  Security Considerations

   There are no direct security considerations generated by this
   document, but existing documented security considerations for
   implementing IPv6 will apply.

5.  Informative References

              APNIC, "APNIC Press Release - Key Turning Point in Asia
              Pacific IPv4 Exhaustion", April 2011, <http://

              IANA, "IANA IPv4 Address Space Registry",

              Donley, C., Howard, L., Kuarsingh, V., Berg, J., and J.
              Doshi, "Assessing the Impact of Carrier-Grade NAT on
              Network Applications", Work in Progress, November 2011.

   [RFC1122]  Braden, R., Ed., "Requirements for Internet Hosts -
              Communication Layers", STD 3, RFC 1122, October 1989.

   [RFC1812]  Baker, F., Ed., "Requirements for IP Version 4 Routers",
              RFC 1812, June 1995.

   [RFC1883]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 1883, December 1995.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

   [RFC6204]  Singh, H., Beebee, W., Donley, C., Stark, B., and O.
              Troan, Ed., "Basic Requirements for IPv6 Customer Edge
              Routers", RFC 6204, April 2011.

   [RFC6269]  Ford, M., Ed., Boucadair, M., Durand, A., Levis, P., and
              P. Roberts, "Issues with IP Address Sharing", RFC 6269,
              June 2011.

   [RFC6434]  Jankiewicz, E., Loughney, J., and T. Narten, "IPv6 Node
              Requirements", RFC 6434, December 2011.

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RFC 6540                      IPv6-Required                   April 2012

Authors' Addresses

   Wesley George
   Time Warner Cable
   13820 Sunrise Valley Drive
   Herndon, VA  20171

   Phone: +1 703-561-2540
   EMail: wesley.george@twcable.com

   Chris Donley
   858 Coal Creek Circle
   Louisville, CO  80027

   Phone: +1-303-661-9100
   EMail: C.Donley@cablelabs.com

   Christopher Liljenstolpe
   Big Switch Networks
   430 Cowper St.
   Palo Alto, CA  94301

   EMail: cdl@asgaard.org

   Lee Howard
   Time Warner Cable
   13820 Sunrise Valley Drive
   Herndon, VA  20171

   Phone: +1-703-345-3513
   EMail: lee.howard@twcable.com

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