An Internet Transition Plan
A phased timeline for transitioning the Internet from IPv4 to IPv6
Curran, J., "An Internet Transition Plan", RFC 5211, DOI 10.17487/RFC5211, July 2008, <https://www.rfc-editor.org/info/rfc5211>.
@misc{rfc5211,
series = {Request for Comments},
number = 5211,
howpublished = {RFC 5211},
publisher = {RFC Editor},
doi = {10.17487/RFC5211},
url = {https://www.rfc-editor.org/info/rfc5211},
author = {J. Curran},
title = {{An Internet Transition Plan}},
pagetotal = 8,
year = 2008,
month = jul,
} RFC text
Contents
Network Working Group J. Curran
Request for Comments: 5211 July 2008
Category: Informational
An Internet Transition Plan
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
IESG Note
This RFC is not a candidate for any level of Internet Standard. The
IETF disclaims any knowledge of the fitness of this RFC for any
purpose and notes that the decision to publish is not based on IETF
review apart from IESG review for conflict with IETF work. RFC
Editor has chosen to publish this document at its discretion. See
RFC 3932 for more information.
Abstract
This memo provides one possible plan for transitioning the Internet
from a predominantly IPv4-based connectivity model to a predominantly
IPv6-based connectivity model.
Table of Contents
1. Introduction ....................................................2
1.1. Requirements Language ......................................2
2. A Phased Transition Model .......................................2
2.1. Preparation Phase - Present to December 2009 ...............3
2.2. Transition Phase - January 2010 to December 2011 ...........4
2.3. Post-Transition Phase - January 2012 to the Future .........4
3. Summary .........................................................5
4. Security Considerations .........................................5
5. IANA Considerations .............................................5
6. Acknowledgments .................................................6
7. References ......................................................6
7.1. Normative References .......................................6
7.2. Informative References .....................................6
1. Introduction
This memo provides one possible plan for transitioning the Internet
from a predominantly IPv4-based connectivity model to a predominantly
IPv6-based connectivity model.
Other transition plans are possible and this purely informational
document does not create an obligation on any party to undertake any
of the actions specified herein, and the use of requirements language
per RFC 2119 is only for the purpose of clearly describing the
proposed transition plan in unambiguous terms.
The motivation for an Internet-wide transition plan is to facilitate
coordination of expectations among innumerable, highly decentralized
entities during a period of significant change, thus reducing risk to
the defining Internet property of universal connectivity.
The purpose of specifying this particular transition plan is to allow
for overall assessment of the challenges of accomplishing the desired
transition and to continue the discussion of Internet-wide transition
plans in general.
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].
RFC 2119 defines the use of these key words to help make the intent
of Standards Track documents as clear as possible. While not a
Standards Track document, the same key words are used in this
document only for sake of clarity in describing the proposed
transition plan.
2. A Phased Transition Model
It is not reasonable to specify the changes that each and every
system connected to the Internet must undergo in order to achieve the
desired transition, as the number of connected systems precludes
creating one plan that contains such a level of detail. Further,
while there are common scenarios that may be specified for
transitioning individual networks (refer to [RFC3750] and [RFC4057]
for examples), the specific timeline and mechanisms utilized for a
given network will be unique. Despite these challenges, it is
necessary to coordinate expectations on an overall basis so that
Internet-wide connectivity is maintained throughout the transition.
This document specifies a three-phase transition plan that includes
preparation, transition, and post-transition phases, and delineates
the necessary activities within each phase based on the role that an
organization plays in the provision and use of Internet services.
An important distinction made in this transition plan is identifying
the explicit requirement for existing end-site organizations to add
IPv6-based connectivity to their public-facing servers during a
transition phase. An accelerated adoption of IPv6 for public-facing
servers enables new organizations in the post-transition phase to be
connected to the Internet only via IPv6 and still have access to a
substantial representative base of publicly available servers.
For nearly every organization, the task of IPv6-enabling their
public-facing servers is far easier than undertaking an
organization-wide adoption of IPv6. Still, the requirement for
existing Internet-connected organizations to add IPv6 connectivity
(even to a small number of systems) will be a significant hurdle and
require a level of effort that may not be achievable given the lack
of compelling additional benefits to these organizations [RFC1669].
This transition plan presumes that "connectivity is its own reward"
[RFC1958] and that there still exists a sufficient level of
cooperation among Internet participants to make this evolution
possible.
The three proposed phases are: Preparation Phase, Transition Phase,
and Post-Transition Phase. The timeline for the phases has been set
to allow entry to the Post-Transition Phase prior to the projected
IPv4 address pool exhaustion date [IPUSAGE].
2.1. Preparation Phase - Present to December 2009
In the Preparation Phase, Service Providers pilot test their IPv6
network services, and end-site organizations prepare to provide
Internet-facing services via IPv6-based connectivity while continuing
to provide Internet-facing services via IPv4 connectivity.
During the Preparation Phase, the following principles apply:
PREP1: Service Providers SHOULD offer pilot IPv6-based Internet
Service to their Internet customers. IPv6-based Internet
Service MAY be provided via IPv6 transition mechanisms (such
as those described in [RFC4213], for example) or via native
IPv6 network service.
PREP2: Organizations SHOULD arrange for IPv6-based Internet
connectivity for any Internet-facing servers (e.g., web,
email, and domain name servers). Internet-facing IPv6 servers
in this phase SHOULD use separate service names per [RFC4472]
to avoid impact to production IPv4-based services unless the
organization supports production IPv6 connectivity.
PREP3: Organizations MAY provide IPv6-based Internet connectivity to
internal user communities.
2.2. Transition Phase - January 2010 to December 2011
In the Transition Phase, Service Providers offer production IPv6 and
IPv4 services to their Internet customers. End-site organizations
provide Internet-facing services in a production manner via IPv6-
based connectivity in addition to IPv4-based connectivity.
During the Transition Phase, the following principles apply:
TRANS1: Service Providers MUST offer IPv6-based Internet Service to
their Internet customers. IPv6-based Internet Service SHOULD
be via native IPv6 network service but MAY be via IPv6
transition mechanisms if necessary.
TRANS2: Organizations MUST arrange for IPv6-based Internet
connectivity for any Internet-facing servers (e.g., web,
email, and domain name servers). Internet-facing IPv6
servers SHOULD be treated as production by the organization,
and SHOULD be treated as production by other Internet
organizations.
TRANS3: Organizations SHOULD provide IPv6-based Internet connectivity
to their internal user communities, and provide IPv6 internal
supporting servers (e.g., DNS, DHCP). IPv6-based Internet
connectivity MAY be via native IPv6 network service or MAY be
via IPv6 transition mechanisms.
2.3. Post-Transition Phase - January 2012 to the Future
In the Post-Transition Phase, end-site organizations provide all
Internet-facing services via IPv6-based connectivity, thus allowing
for new Internet customers connected solely by IPv6.
During the Post-Transition Phase, the following principles apply:
POST1: Service Providers MUST offer IPv6-based Internet Service to
their Internet customers. IPv6-based Internet Service SHOULD
be via native IPv6 network service.
POST2: Organizations MUST arrange for IPv6-based Internet
connectivity for any Internet-facing servers (e.g., web,
email, and domain name servers). Internet-facing IPv6 servers
MUST be treated as production by the organization, and SHOULD
be treated as production by other Internet organizations.
POST3: Organizations SHOULD provide IPv6-based Internet connectivity
to internal user communities, and provide IPv6 internal
supporting infrastructure (e.g., routers, DNS, DHCP, etc).
IPv6-based Internet connectivity SHOULD be via native IPv6
network service or MAY be via IPv6 transition mechanisms.
POST4: Service Providers MAY continue to offer IPv4-based Internet
connectivity to their Internet customers. Organizations MAY
continue to use IPv4-based Internet connectivity.
3. Summary
In order to facilitate full Internet-wide connectivity during the
transition from IPv4-based connectivity to IPv6-based connectivity, a
transition plan which provides clear guidance to organizations
regarding expectations is necessary. As the specific expectations
change over time, and vary greatly by organization, a phased approach
is specified in this document, with the timeline for each phase set
with the intention of allowing enough time for the necessary planning
and deployment steps which each organization much undertake. This
Internet Transition Plan provides for transition to predominantly
IPv6-connectivity by January 2012 which, with careful management, may
meet the overall requirements of allowing the Internet to scale as
specified in "The Recommendation for the IP Next Generation Protocol"
[RFC1752].
4. Security Considerations
This memo describes the transition of the Internet from IPv4-based
connectivity to predominantly IPv6-based connectivity. This change
inherently has security implications due to the widespread deployment
of a new version of the Internet Protocol but these are beyond the
scope of this document and are covered in [RFC4942]. This document
raises no new security issues itself.
5. IANA Considerations
While no new name or identifier space is created by this document,
the policies for management of Internet Protocol version 4 (IPv4)
address space may not provide for IPv4 availability through the
Transition Phase as intended by this plan. The IANA should work with
all parties to develop policies per [RFC2050] which allow continued
general availability of IPv4 address resources sufficiently long for
any transition plan that receives widespread community support.
6. Acknowledgments
This document would not have been possible without the abundant
suggestions made by members of the Internet community at large, but
specific thanks go to Fred Baker, Jim Bound, Scott Bradner, Bob
Braden, Randy Bush, David Divins, Geoff Huston, Chris Morrow, Jordi
Palet, Ken Shores, James Woodyatt, and the members of the IETF V6
Operations Working Group for their review and insightful suggestions
for improvement.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
for IPv6 Hosts and Routers", RFC 4213, October 2005.
[RFC4472] Durand, A., Ihren, J., and P. Savola, "Operational
Considerations and Issues with IPv6 DNS", RFC 4472, April
2006.
[RFC1752] Bradner, S. and A. Mankin, "The Recommendation for the IP
Next Generation Protocol", RFC 1752, January 1995.
7.2. Informative References
[RFC1958] Carpenter, B., Ed., "Architectural Principles of the
Internet", RFC 1958, June 1996.
[RFC1669] Curran, J., "Market Viability as a IPng Criteria", RFC
1669, August 1994.
[IPUSAGE] Huston, G., IPv4 Address Report, February 2008,
<http://www.potaroo.net/tools/ipv4/index.html>.
[RFC4057] Bound, J., Ed., "IPv6 Enterprise Network Scenarios", RFC
4057, June 2005.
[RFC3750] Huitema, C., Austein, R., Satapati, S., and R. van der
Pol, "Unmanaged Networks IPv6 Transition Scenarios", RFC
3750, April 2004.
[RFC2050] Hubbard, K., Kosters, M., Conrad, D., Karrenberg, D., and
J. Postel, "Internet Registry IP Allocation Guidelines",
BCP 12, RFC 2050, November 1996.
[RFC4942] Davies, E., Krishnan, S., and P. Savola, "IPv6
Transition/Co-existence Security Considerations", RFC
4942, September 2007.
Author's Address
John Curran
99 Otis Street
Cambridge, MA USA 20190
EMail: jcurran@istaff.org
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AI ELI5
On this page
§1The IPv4 Address Crisis and the Need for a Plan
IPv4 uses 32-bit addresses, giving the Internet about 4.3 billion unique addresses. By 2008, when RFC 5211 was published, the growth of mobile devices, IoT, and cloud computing was rapidly consuming remaining addresses, with exhaustion projected within a few years.
IPv6 uses 128-bit addresses—enough to give every grain of sand on Earth its own address. But IPv6 is fundamentally incompatible with IPv4. Switching the entire Internet is one of the largest infrastructure migrations in history.
RFC 5211 emphasizes that this document is a proposal and informational RFC, not an IETF mandate. Different regions, operators, and organizations will transition at different rates. The goal is to publish a plausible plan that demonstrates the transition is feasible and to coordinate expectations to maintain universal Internet connectivity throughout.
The old address system is almost full. A new one is ready but completely different. We need a plan so people switch at about the same pace and the Internet does not break.
§2Preparation Phase (2009)
In the Preparation Phase, service providers begin piloting IPv6 services, and organizations enable IPv6 on public-facing servers (those visible to the Internet) while keeping IPv4.
The plan expects: Service providers SHOULD pilot IPv6, using either native IPv6 networks or transition mechanisms (like IPv6-in-IPv4 tunnels). Organizations SHOULD arrange IPv6 connectivity for servers like web, email, and DNS servers, ideally using separate service names to avoid disrupting existing IPv4 customers. Organizations MAY provide IPv6 to internal users (optional in this phase).
The Preparation Phase allows organizations to gain experience, test their systems, and prepare infrastructure without forcing immediate change. It is not required to be production-ready; pilot status is acceptable.
Phase 1: Try it out. Set up IPv6 systems, test them, but keep running IPv4 as usual. No one has to commit yet.
§3Transition Phase (2010–2011)
In the Transition Phase, the stakes increase. Service providers MUST offer IPv6 as a production service (native IPv6 is preferred, but transition mechanisms are acceptable). Organizations MUST arrange IPv6 for public-facing servers, and IPv6 services should now be treated as production-quality by both the organization and by others consuming those services.
Additionally, organizations SHOULD provide IPv6 to internal user communities and internal supporting infrastructure like DNS and DHCP servers (with either native IPv6 or transition mechanisms).
This phase marks the shift from optional experimentation to mandatory deployment. The plan expects most public-facing infrastructure to be reachable via IPv6 by 2011, ensuring that organizations entering the post-transition phase can rely on significant IPv6 coverage.
Phase 2: Go live. All big services must work on IPv6 and be treated as production. Organizations that need IPv6-only connections will be able to reach most of the web.
§4Post-Transition Phase (2012 Onward)
In the Post-Transition Phase, the Internet is predominantly IPv6. Organizations MUST provide IPv6 for public-facing servers and MUST treat IPv6 as production. New customers can now be issued only IPv6 addresses and expect to reach nearly all public services.
Service providers MUST offer IPv6 connectivity, with native IPv6 as the default. Organizations SHOULD (but are not required to) provide IPv6 internally as well.
IPv4 is not abandoned: POST4 allows service providers and organizations to continue offering and using IPv4 service indefinitely. Dual-stack (supporting both IPv4 and IPv6) becomes the long-term reality.
The timeline sets January 2012 as the target for this phase, chosen to arrive before IPv4 address exhaustion projections. This ensures that pure-IPv6 customers can still reach a mature ecosystem of IPv6-enabled services.
Phase 3: IPv6 is the default. If you are a new company, you can get an IPv6-only internet connection and reach most of the web. Old IPv4 networks still exist but are no longer required.
§5The Key Insight: Public-Facing Servers First
RFC 5211's central insight is that adding IPv6 to public-facing servers is easier than transitioning an entire organization. A small team can enable IPv6 on a web server without changing internal networks. This is far less work than retrofitting an organization's entire infrastructure.
By requiring public-facing IPv6 in the Transition Phase, the plan creates an environment where post-transition IPv6-only customers have access to a critical mass of services. This economic incentive helps pull the Internet toward IPv6 adoption.
The RFC notes this is still a significant hurdle: organizations lack immediate financial incentives to upgrade, and RFC 5211 ultimately depends on a shared commitment among Internet participants that "connectivity is its own reward"—the belief that a connected, functioning Internet benefits everyone enough to justify the upgrade burden.
The clever part: If you only have to fix your public website (not your whole company), you will probably do it. Once enough websites support IPv6, new companies can use only IPv6.