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rfc:rfc6540

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

Abstract

 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
 http://www.rfc-editor.org/info/rfc6540.

George, et al. Best Current Practice [Page 1] 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.

George, et al. Best Current Practice [Page 2] 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
 implementation.

George, et al. Best Current Practice [Page 3] 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 3.2.1.1 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
 follows:
 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
    implementation.
 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.

George, et al. Best Current Practice [Page 4] 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-EXHAUST]
            APNIC, "APNIC Press Release - Key Turning Point in Asia
            Pacific IPv4 Exhaustion", April 2011, <http://
            www.apnic.net/__data/assets/pdf_file/0018/33246/
            Key-Turning-Point-in-Asia-Pacific-IPv4-
            Exhaustion_English.pdf>.
 [IANA-EXHAUST]
            IANA, "IANA IPv4 Address Space Registry",
            <http://www.iana.org/assignments/ipv4-address-space>.
 [NAT444-IMPACTS]
            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.

George, et al. Best Current Practice [Page 5] RFC 6540 IPv6-Required April 2012

Authors' Addresses

 Wesley George
 Time Warner Cable
 13820 Sunrise Valley Drive
 Herndon, VA  20171
 US
 Phone: +1 703-561-2540
 EMail: wesley.george@twcable.com
 Chris Donley
 CableLabs
 858 Coal Creek Circle
 Louisville, CO  80027
 US
 Phone: +1-303-661-9100
 EMail: C.Donley@cablelabs.com
 Christopher Liljenstolpe
 Big Switch Networks
 430 Cowper St.
 Palo Alto, CA  94301
 US
 EMail: cdl@asgaard.org
 Lee Howard
 Time Warner Cable
 13820 Sunrise Valley Drive
 Herndon, VA  20171
 US
 Phone: +1-703-345-3513
 EMail: lee.howard@twcable.com

George, et al. Best Current Practice [Page 6]

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