Internet Engineering Task Force (IETF) B. Carpenter
BCP: 242 Univ. of Auckland
Request for Comments: 9812 S. Krishnan
Updates: 7249 Cisco
Category: Best Current Practice D. Farmer
ISSN: 2070-1721 Univ. of Minnesota
June 2025
Clarification of IPv6 Address Allocation Policy
Abstract
This document specifies the approval process for changes to the
"Internet Protocol Version 6 Address Space" registry. It also
updates RFC 7249.
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 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9812.
Copyright Notice
Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction
2. Approval Level of IPv6 Address Allocations
3. RFC Editor Considerations
4. IANA Considerations
5.
4. Security Considerations
6.
5. References
6.1.
5.1. Normative References
6.2.
5.2. Informative References
Appendix A. Acknowledgements
Authors' Addresses
1. Introduction
Internet Protocol Version 6 (IPv6) and its address space are defined
by [STD86] and [RFC4291]. The management of the IPv6 address space
was delegated to IANA by [RFC1881], some years before the
relationship between the IETF and IANA was formalized [RFC2860] and
registry details were clarified [RFC7020] [RFC7249].
Occasionally, IPv6 address space allocations are performed outside
the scope of routine allocations to Regional Internet Registries
(RIRs). For example, a substantial allocation was requested by an
IETF document approved by the IESG [RFC9602], which moved the range
5f00::/16 from the "Internet Protocol Version 6 Address Space"
registry [IANA1] to the "IANA IPv6 Special-Purpose Address Registry"
[IANA3].
At the time of writing, the allocation policy in the "Internet
Protocol Version 6 Address Space" registry [IANA1] was shown as "IESG
approval", whereas a more stringent policy is appropriate for major
allocations. The present document therefore strengthens the approval
level needed for non-routine address allocations, which requires an
update to [RFC7249].
This document also clarifies the status of [RFC1881]. This
clarification is necessary because [RFC1881], a joint publication of
the IAB and IESG following an IETF Last Call, was incorrectly listed
in the RFC index at the time of writing as "Legacy", whereas it is
part of the IETF Stream [RFC8729].
2. Approval Level of IPv6 Address Allocations
Portions of the IPv6 address space are shown in the registry as
"Reserved by IETF" [IANA1]. This is the address space held in
reserve for future use if ever the 125-bit unicast space (2000::/3)
is found inadequate or inappropriate.
[RFC1881] did not specify an allocation policy for this space. At
some point, IANA listed "IESG approval". As defined in [BCP26], this
is a rather weak requirement ("Although there is no requirement that
the request be documented in an RFC, the IESG has the discretion to
request documents...") and is "a fall-back mechanism in the case
where one of the other allowable approval mechanisms cannot be
employed...".
For something as important as the majority of the spare IPv6 address
space, this process is clearly insufficient. The present document
replaces the "IESG approval" process by the "IETF Review" process as
defined by [BCP26]. The stricter "Standards Action" policy is not
considered necessary, because there may be cases where opening up a
new range of address space does not in fact require a new protocol
standard.
It may be noted that the allocation for [RFC9602], which was
processed as a working group document, did indeed follow the more
stringent "IETF Review" process proposed by this document. Indeed,
the other two related registries [IANA2] [IANA3] cite the "IETF
Review" policy, consistent with [RFC7249].
This document therefore extends the first paragraph of Section 2.3 of
[RFC7249] as follows:
OLD:
| The vast bulk of the IPv6 address space (approximately 7/8ths of
| the whole address space) is reserved by the IETF [RFC4291], with
| the expectation that further assignment of globally unique unicast
| address space will be made from this reserved space in accordance
| with future needs.
NEW:
| The vast bulk of the IPv6 address space (approximately 7/8ths of
| the whole address space) is reserved by the IETF [RFC4291], with
| the expectation that further assignment of globally unique unicast
| address space will be made from this reserved space in accordance
| with future needs, through "IETF Review" as defined in [BCP26].
3. RFC Editor Considerations
Per this document, the RFC Editor has updated the Stream information
for [RFC1881] to IETF in place of Legacy.
4. IANA Considerations
IANA has updated the registration procedure of the "Internet Protocol
Version 6 Address Space" registry [IANA1] to "IETF Review".
5.
4. Security Considerations
The security considerations of [RFC7249] apply. While having no
direct security impact, carefully reviewed address allocation
mechanisms are necessary to ensure operational address
accountability.
6.
5. References
6.1.
5.1. Normative References
[BCP26] Best Current Practice 26,
<https://www.rfc-editor.org/info/bcp26>.
At the time of writing, this BCP comprises the following:
Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>.
[STD86] Internet Standard 86,
<https://www.rfc-editor.org/info/std86>.
At the time of writing, this STD comprises the following:
Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
6.2.
5.2. Informative References
[IANA1] IANA, "Internet Protocol Version 6 Address Space",
<https://www.iana.org/assignments/ipv6-address-space>.
[IANA2] IANA, "IPv6 Global Unicast Address Assignments",
<https://www.iana.org/assignments/ipv6-unicast-address-
assignments>.
[IANA3] IANA, "IANA IPv6 Special-Purpose Address Registry",
<https://www.iana.org/assignments/iana-ipv6-special-
registry>.
[RFC1881] IAB and IESG, "IPv6 Address Allocation Management",
RFC 1881, DOI 10.17487/RFC1881, December 1995,
<https://www.rfc-editor.org/info/rfc1881>.
[RFC2860] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of
Understanding Concerning the Technical Work of the
Internet Assigned Numbers Authority", RFC 2860,
DOI 10.17487/RFC2860, June 2000,
<https://www.rfc-editor.org/info/rfc2860>.
[RFC7020] Housley, R., Curran, J., Huston, G., and D. Conrad, "The
Internet Numbers Registry System", RFC 7020,
DOI 10.17487/RFC7020, August 2013,
<https://www.rfc-editor.org/info/rfc7020>.
[RFC7249] Housley, R., "Internet Numbers Registries", RFC 7249,
DOI 10.17487/RFC7249, May 2014,
<https://www.rfc-editor.org/info/rfc7249>.
[RFC8729] Housley, R., Ed. and L. Daigle, Ed., "The RFC Series and
RFC Editor", RFC 8729, DOI 10.17487/RFC8729, February
2020, <https://www.rfc-editor.org/info/rfc8729>.
[RFC9602] Krishnan, S., "Segment Routing over IPv6 (SRv6) Segment
Identifiers in the IPv6 Addressing Architecture",
RFC 9602, DOI 10.17487/RFC9602, October 2024,
<https://www.rfc-editor.org/info/rfc9602>.
Appendix A. Acknowledgements
Useful comments were received from Dale Carder, Bob Hinden, Scott
Kelly, Philipp Tiesel, and others.
Authors' Addresses
Brian E. Carpenter
The University of Auckland
School of Computer Science
PB 92019
Auckland 1142
New Zealand
Email: brian.e.carpenter@gmail.com
Suresh Krishnan
Cisco Systems, Inc.
Email: suresh.krishnan@gmail.com
David E. Farmer III
University of Minnesota
Office of Information Technology
Minneapolis, MN 55455
United States of America
Email: farmer@umn.edu