IPv6 Support Within IETF work
draft-george-ipv6-support-02

Abstract

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 further recommends that IETF revisit and update the previous attempts to review existing standards for IPv6 compliance. It makes this recommendation in order to ensure that it is possible to operate without dependencies on IPv4.

Status of This Memo

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

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This Internet-Draft will expire on July 10, 2014.

Copyright Notice

Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved.

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Table of Contents

• 1. Introduction
• 1.1. Requirements Language
• 2. IPv6-only operation
• 2.1. Functional Parity with IPv4
• 2.2. IPv4 Sunset
• 3. IETF Actions
• 4. Requirements and Recommendations
• 5. Acknowledgements
• 6. IANA Considerations
• 7. Security Considerations
• 8. References
• 8.1. Normative References
• 8.2. Informative References
• Authors' Addresses

1. Introduction

[RFC6540] gives guidance to implementers that in order to ensure interoperability and proper function after IPv4 exhaustion, IP-capable devices need to support IPv6, and cannot be reliant on IPv4, because global IPv4 exhaustion creates many circumstances where the use of IPv6 will no longer be optional. Since this is an IETF Best Current Practice recommendation, it is imperative that the results of IETF efforts enable implementers to follow that recommendation. This document provides recommendations and guidance as to how IETF itself should handle future work as it relates to Internet Protocol versions, and discusses the need for gap analyses on existing work.

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. However, as the IPv4 to IPv6 transition continues, it will become increasingly difficult to ensure interoperability and backward compatibility with IPv4-only networks and applications. 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 formal requirement for all IETF work to support IPv6, either implicitly by being network-layer agnostic or explicitly by having an IPv6-specific implementation. Additionally, although reviews in RFC's 3789 [RFC3789] through RFC3796 ensured that IETF standards then in use could support IPv6, no IETF-wide effort has been undertaken to ensure that the issues identified in those drafts are all addressed, nor to ensure that standards written after RFC3100 (where the previous review efforts stopped) function properly on IPv6-only networks.

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. IPv6-only operation

At this document's writing, IPv6 has seen significant deployment. Most of these deployments are dual-stack, with IPv4 and IPv6 coexisting on the same networks. However, dual-stack is a waypoint in the transition from IPv4 to IPv6. The eventual end state is networks and end points that are IPv6-only. Some operators may take a long time to turn off IPv4, if they ever do, but the IETF must make sure that its standards can be deployed by even the first operators to turn off IPv4. Problems (and solutions) should be identified before they are encountered by the earliest adopters.

2.1. Functional Parity with IPv4

In order for IPv6-only operation to be realistic, IPv6 MUST have at least functional parity with IPv4. "Functional parity" means that any function that IPv4 enabled MUST also be enabled by IPv6. This does not mean that every feature that exists in IPv4 will exist in IPv6; different features may enable the same function. For instance, IPv4 supports some features that are no longer in use. In some cases it has not been practical to remove them in IPv4, or even to declare them historic, but it is unnecessary to carry them forward into IPv6. IPv6 also eliminates the need for some features that exist in IPv4; no effort to create unneeded features is required. Functional parity does not mean that all functions in IPv6 must also be possible in IPv4. Indeed, with IPv6 becoming the predominant protocol, new functionality should be developed in IPv6, and IETF effort SHOULD NOT be spent retrofitting features into the legacy protocol. The key at this point is to ensure that existing standards and protocols have been actively reviewed, and any parity gaps either identified so that they can be fixed, or documented as unnecessary to address because it is unused or superseded by other features.

2.2. IPv4 Sunset

Somewhat distinct from identifying the needed features for IPv6-only functional parity is the effort to identify what is necessary to disable or sunset IPv4 in a given network. Since many of the protocols in use today were designed to be fault-tolerant and very robust, actually removing them from a network once they are no longer needed is sometimes complex. Many implementations may not even have "off switches" because the assumption was that they would never be switched off in a normal network implementation. The Sunset4 Working Group was chartered to address these issues:

"The Working Group will point out specific areas of concern, provide recommendations, and standardize protocols that facilitate the graceful "sunsetting" of the IPv4 Internet in areas where IPv6 has been deployed. This includes the act of shutting down IPv4 itself, as well as the ability of IPv6-only portions of the Internet to continue to connect with portions of the Internet that remain IPv4-only. ... Disabling IPv4 in applications, hosts, and networks is new territory for much of the Internet today, and it is expected that problems will be uncovered including those related to basic IPv4 functionality, interoperability, as well as potential security concerns. The working group will report on common issues, provide recommendations, and, when necessary, protocol extensions in order to facilitate disabling IPv4 in networks where IPv6 has been deployed."

3. IETF Actions

In addition to a requirement for IPv6 support in the following section, this document recommends two major actions:

First, the IETF must review RFCs 3789-3796 to ensure that any gaps in specifications identified in these documents and still in active use have been updated as necessary to enable operation in IPv6-only environments (or if no longer in use, are declared historic). A document updating each of the below area-specific RFCs to identify which gaps have been addressed and which ones are either still outstanding or are now irrelevant may be an appropriate way to track this activity.

• Internet Area [RFC3790]
• Routing Area [RFC3791]
• Security Area [RFC3792]
• Sub-IP Area [RFC3793]
• Transport Area [RFC3794]
• Applications Area [RFC3795]
• Operations and Management Area [RFC3796]

Second, the IETF must review documents written after the existing review stopped (according to RFC 3790, this review stopped with approximately RFC 3100) to identify specifications where IPv6-only operation is not possible, and update them as necessary and appropriate, or document why an identified gap is not an issue i.e. not necessary for functional parity with IPv4.

This represents a significant amount of work in addition to IETF's existing workload, and there are basically two options for how to accomplish this significant document review. If existing IETF resources are to take on this work, one method would be for Area Directors to charter their existing Working Groups to undertake this review for relevant work, and charter their Directorates or other volunteers to review work that is not within the charter of any active Working Group. Another method would be to charter one (new or existing) Working Group or directorate to oversee this activity, with the assumption that the WG or directorate will pull in expertise from other areas and WGs as needed. The alternative is to use a similar model to the previous analysis in RFCs 3789-3796, in which ISOC funded dedicated resources whose primary duty was to complete this document audit.

RFC3789 [RFC3789] section 2 provides some guidance on methodology that can serve as a useful starting point for this effort.

"To perform this study, each class of IETF standards are investigated in order of maturity: Full, Draft, and Proposed, as well as Experimental. Informational and BCP RFCs are not addressed. RFCs that have been obsoleted by either newer versions or because they have transitioned through the standards process are not covered. RFCs which have been classified as Historic are also not included."

This document does not recommend excluding Informational and BCP RFCs as the previous effort did, due to changes in the way that these documents are used and their relative importance in the RFC Series. Instead, any documents that are still active (i.e. not declared historic or obsolete) and the product of IETF consensus (i.e. not a product of the ISE Series) should be included. In addition, the reviews undertaken by RFC 3789-96 were looking for "IPv4 dependency" or "usage of IPv4 addresses in standards". This document recommends a slightly more specific set of criteria for review: review should include consideration of whether the specification can operate in an environment without IPv4. Reviews should include guidance on the use of 32-bit identifiers that are commonly populated by IPv4 addresses. Reviews should include consideration of protocols on which specifications depend or interact, to identify indirect dependencies on IPv4. Finally, reviews should consider how to migrate from an IPv4 environment to an IPv6 environment.

By necessity, this sort of gap analysis work is already happening in several places, e.g. draft-ietf-sunset4-gapanalysis [I-D.ietf-sunset4-gapanalysis], draft-george-mpls-ipv6-only-gap [I-D.george-mpls-ipv6-only-gap], and draft-klatsky-dispatch-ipv6-impact-ipv4 [I-D.klatsky-dispatch-ipv6-impact-ipv4]. These efforts are limited in scope, but may serve as a model for the larger effort necessary.

4. Requirements and Recommendations

While the primary goal of this effort is to ensure that existing IETF work has been properly evaluated and updated for IPv6-only support, ongoing focus is required for future work, whether via IESG evaluation, individual document reviews, or future WG charters. 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. 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, the IETF needs to complete 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, in support of security, transition, and decommissioning, should continue, accompanied by problem statements based on operational experience. Generally the focus should move away from IPv4-only work.

• IETF should make updates to IPv4 protocols and features to facilitate IPv4 decommissioning
• IETF work SHOULD explicitly support IPv6 or SHOULD be IP version agnostic (because it is implemented above the network layer), except IPv4-specific transition or address-sharing technologies.
• IETF SHOULD NOT initiate new IPv4 extension technology development.
• IETF work SHOULD function completely on IPv6-only nodes and networks, unless consensus exists that it is unnecessary to use a given feature or protocol on IPv6-only networks.
• IETF SHOULD identify and update IPv4-only protocols and applications to support IPv6 unless consensus exists that it is unnecessary for a given feature or protocol.

5. Acknowledgements

Thanks to the following people for their comments: Jari Arkko, Ralph Droms, Scott Brim, Margaret Wasserman, Brian Haberman. 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.

6. IANA Considerations

This memo includes no request to IANA.

7. Security Considerations

This document generates no new security considerations because it is not defining a new protocol. As existing work is analyzed for its ability to operate properly on IPv6-only networks, new security issues may be identified.

8. References

8.1. Normative References

8.2. Informative References

Authors' Addresses