Internet Engineering Task Force W. George
Internet-Draft Time Warner Cable
Intended status: Best Current Practice C. Donley
Expires: August 22, 2012 Cablelabs
L. Howard
Time Warner Cable
February 21, 2012

IPv6 Support Within IETF work


This document recommends that IETF formally require its standards work to be IP version agnostic or to explicitly include support for IPv6, with some exceptions. It recommends that future IPv4 work be limited to solving documented operational problems identified through deployment experience.

Status of this Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at

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This Internet-Draft will expire on August 22, 2012.

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Table of Contents

1. Introduction

[I-D.ietf-intarea-ipv6-required] gives guidance to implementers that in order to ensure interoperability and proper function after IPv4 exhaustion, IP-capable devices need to support IPv6, because global IPv4 exhaustion creates many circumstances where the use of IPv6 will no longer be optional.

In the above draft, IETF is making the recommendation that IP-capable devices need to support IPv6. Therefore, it is imperative that the results of IETF efforts enable implementers to follow that recommendation. This document provides explicit recommendations and guidance as to how IETF itself should handle future work as it relates to Internet Protocol versions.

1.1. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119].

2. Requirements and Recommendation

When considering support for IPv4 vs IPv6 within IETF work, the general goal is to provide tools that enable networks and applications to operate seamlessly in any combination of IPv4-only, dual-stack, or IPv6-only as their needs dictate.

As IPv6 deployment grows, IETF will naturally focus on features and protocols that enhance and extend IPv6, along with continuing work on items that are IP version agnostic. New features and protocols will not typically be introduced for use as IPv4-only. However, as of this document's writing, there is no documented requirement for all IETF work to support IPv6, either implicitly by being network-layer agnostic or explicitly by having an IPv6-specific implementation.

Due to the existing operational base of IPv4, it is not realistic to completely bar further work on IPv4 within the IETF at this time, nor to formally declare it historic. This draft is viewed as a first step in IPv4's eventual phase-out, in that it limits IPv4-specific activities within the IETF to a few key areas. Until the time when IPv4 is no longer in wide use and/or declared historic, the IETF needs to continue to update IPv4-only protocols and features for vital operational or security issues. Similarly, IETF needs to continue the work related to IPv4-to-IPv6 transition tools for migrating more traffic to IPv6. As the transition to IPv6-capable networks accelerates, it is also likely that some changes may be necessary in IPv4 protocols to facilitate decommissioning IPv4 in a way that does not create unacceptable impact to applications or users. These sorts of IPv4-focused activities should be allowed to continue, especially if they are accompanied by real operational experience documenting the problem to be solved.

Generally, the IETF should be focused on two goals as it relates to IP version support:

  1. Transition technologies that enable IPv6
  2. Complete support for IPv6-only operation

It is helpful to clarify what the above statements mean. "Transition technologies" is a fairly broad term that can be interpreted in a lot of different ways. At its broadest, it includes providing IPv6 support over an IPv4 network and vice versa, methods to interwork IPv4-only devices and IPv6-only devices, as well as technologies to extend IPv4's life despite the lack of additional globally unique addresses to provide to hosts and networks. This document makes the distinction between those technologies which provide a path for an IPv4-only network to become dual-stack or otherwise use native IPv6, and those which primarily serve to extend the life of IPv4 while not providing a path to native IPv6 support on the network in question. The IETF needs to be focusing their work on transition mechanisms that provide progress toward native IPv6, are simple, stateless, and use mechanisms which preserve end-to-end connectivity as much as possible.

While the eventual end state may be networks and end points that are IPv6-only, the timeframe for that to become a reality is likely to be different within each network. This means that there are multiple legitimate use cases for continued support for IPv4, including methods to translate between IPv4-only hosts and IPv6-only hosts, as well as methods for IPv4 address sharing in order to reduce the impact of IPv4 exhaustion on implementations that still use IPv4. The IETF has provided several soutions that have implementations to address the need to keep business running and users happy during this transition, including Dual Stack Lite RFC 6333 [RFC6333], NAT64 RFC 6146 [RFC6146], as well as Carrier Grade NAT ([I-D.ietf-behave-lsn-requirements] and RFC 6264 [RFC6264]). As the above documents complete the IETF document lifecycle and become RFCs, and the BEHAVE WG closes after completion of its charter, this should comprise a body of solutions to meet the needs of the majority of IPv4's continued use cases such that work on additional protocols to extend the life of IPv4 no longer needs to be an area of focus for the IETF.

[**authors' note, remove before publication**]

This document is not intended to be yet another survey of available transition mechanisms, so the list above does not have to be exhaustive. The intent was to cite the most likely candidates for wide deployment as evidence that there exists a consensus solution for each major case. There are a number of other drafts that could be included in the above list of solutions, but as draft documents, they have not yet found consensus. For example, A+P is an Experimental RFC (6346), and its derivative works such as MAP (draft-mdt-softwire-mapping-address-and-port) and potentially 4rd- {E,T,U}, dIVI-PD, stateless 4over6, etc. are current internet-draft documents. Under the structure proposed in this document, a working group would need to find consensus on a problem statement, defining a real operational problem that the proposed solution would solve, before any proposed solution could be adopted as a WG item.

[end author's note]

It is not possible to document completely which technologies and drafts are and are not acceptable, so this document is intended to be a guideline for working groups and IESG members when evaluating new and existing work, rather than being an exhaustive list. There are corner cases and use cases for which the existing solutions may not be a perfect fit, as well as unsolved theoretical problems, but standardizing solutions for every possible permutation moves into the realm of diminishing returns, and solutions applicable only to one or two networks are best pursued between the operator and their vendors. Thus, further work on IPv4-extension protocols such as those mentioned MUST be triggered by a draft documenting actual operational experiences, focusing on problems encountered in deployment that the IETF needs to solve through protocol changes. This will ensure that IETF is focusing its energies on solving real operational problems that exist in IPv4 and transition technologies, rather than interesting theoretical problems, corner cases or new features.

To put this set of guidelines succinctly:

This last item raises a question about where feature parity between IPv4 and IPv6 fits into the discussion. In this context, feature parity ensures that there are no gaps where functionality exists in IPv4 but has no equivalent in IPv6. Note that this does not mean a direct 1:1 relationship where every feature that exists in IPv4 will exist in IPv6. This is because IPv6 eliminates the need for some features that exist in IPv4, IPv4 supports some legacy features that are no longer in use, and some existing IPv4 features are integrated into other parts of IPv6. In addition, as new features and implementations take advantage of the differences between IPv6 and IPv4, it is expected that IPv6 will surpass IPv4 and certain features and protocols will not have specific support for IPv4. A comprehensive list of needed parity items and enhancements for IPv6 is outside the scope of this document, but this document recommends that the charters and work items of currently active IETF Working Groups (WGs) be evaluated to ensure that they are supporting a goal to eliminate of any remaining places in IETF standards and protocols where IPv4 is required for complete and proper function, and that they do not focus on IPv4 extension technologies. This document does not suggest a timeline where this must be completed, as it will likely happen organically over a long period of time.

3. Acknowledgements

Thanks to the following people for their comments: Jari Arkko, Ralph Droms, Scott Brim, Margaret Wasserman. Thanks also to Randy Bush, Mark Townsley, and Dan Wing for their discussion in IntArea WG at IETF 81 in Taipei, TW regarding transition technologies, IPv4 life extension, and IPv6 support.

4. IANA Considerations

This memo includes no request to IANA.

5. Security Considerations

This document generates no new security considerations because it is not defining a new protocol. However, it is important to note that the recommendations above to stop work on IPv4-only protocols and applications include an exception for fixes to critical security issues. The definition of critical in this context will be left to the appropriate ADs, but while IPv4 is still in wide use, it is expected that these exceptions will occur from time to time.

6. References

6.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.

6.2. Informative References

[I-D.ietf-intarea-ipv6-required] George, W, Donley, C, Liljenstolpe, C and L Howard, "IPv6 Support Required for all IP-capable Nodes", Internet-Draft draft-ietf-intarea-ipv6-required-02, December 2011.
[I-D.ietf-behave-lsn-requirements] Perreault, S, Yamagata, I, Miyakawa, S, Nakagawa, A and H Ashida, "Common requirements for Carrier Grade NATs (CGNs)", Internet-Draft draft-ietf-behave-lsn-requirements-05, November 2011.
[RFC6146] Bagnulo, M., Matthews, P. and I. van Beijnum, "Stateful NAT64: Network Address and Protocol Translation from IPv6 Clients to IPv4 Servers", RFC 6146, April 2011.
[RFC6264] Jiang, S., Guo, D. and B. Carpenter, "An Incremental Carrier-Grade NAT (CGN) for IPv6 Transition", RFC 6264, June 2011.
[RFC6333] Durand, A., Droms, R., Woodyatt, J. and Y. Lee, "Dual-Stack Lite Broadband Deployments Following IPv4 Exhaustion", RFC 6333, August 2011.

Authors' Addresses

Wesley George Time Warner Cable 13820 Sunrise Valley Drive Herndon, VA 20171 US Phone: +1 703-561-2540 EMail:
Chris Donley Cablelabs 858 Coal Creek Circle Louisville, CO 80027 US Phone: +1-303-661-9100 EMail:
Lee Howard Time Warner Cable 13820 Sunrise Valley Drive Herndon, VA 20171 US Phone: +1-703-345-3513 EMail: