Internet Numbers Registries
The official registries that track Internet address space allocations.
Housley, R., "Internet Numbers Registries", RFC 7249, DOI 10.17487/RFC7249, May 2014, <https://www.rfc-editor.org/info/rfc7249>.
@misc{rfc7249,
series = {Request for Comments},
number = 7249,
howpublished = {RFC 7249},
publisher = {RFC Editor},
doi = {10.17487/RFC7249},
url = {https://www.rfc-editor.org/info/rfc7249},
author = {R. Housley},
title = {{Internet Numbers Registries}},
pagetotal = 6,
year = 2014,
month = may,
} RFC text
Contents
Internet Engineering Task Force (IETF) R. Housley
Request for Comments: 7249 Vigil Security
Category: Informational May 2014
ISSN: 2070-1721
Internet Numbers Registries
Abstract
RFC 7020 provides information about the Internet Numbers Registry
System and how it is used in the distribution of autonomous system
(AS) numbers and globally unique unicast Internet Protocol (IP)
address space.
This companion document identifies the IANA registries that are part
of the Internet Numbers Registry System at this time.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
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). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see 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/rfc7249.
Copyright Notice
Copyright (c) 2014 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.
1. Introduction
In accordance with the IETF-IANA Memorandum of Understanding
[RFC2860], RFC 7020 [RFC7020] provides information about the Internet
Numbers Registry System and how it is used in the distribution of
autonomous system (AS) numbers and globally unique unicast Internet
Protocol (IP) address space.
This companion document identifies the IANA registries that are part
of the Internet Numbers Registry System at this time.
2. Internet Numbers Registries
Three IANA registries are associated with the Internet Numbers
Registry System: "Autonomous System (AS) Numbers", "IANA IPv4 Address
Space Registry", and "IPv6 Global Unicast Address Assignments".
However, in each case, there are special-purpose values, and those
special-purpose values are outside the Internet Numbers Registry
System.
2.1. Autonomous System Numbers
For historical reasons, there are 16-bit AS numbers and 32-bit AS
numbers. However, the 16-bit AS numbers are really just zero through
65535 of the 32-bit AS number space.
The allocation and registration functions for all non-reserved AS
numbers are handled by the Internet Numbers Registry System in
accordance with policies developed by the Regional Internet
Registries (RIRs) in accordance with their processes.
Some special-purpose AS numbers have been reserved. Section 3 of
this document establishes an IANA registry for special-purpose AS
Numbers that have already been reserved. Future additions to this
registry can be made through "IETF Review" as defined in [RFC5226].
Once a reservation is approved, it is recorded in the special-purpose
AS numbers registry with a reference to the IESG-approved RFC that
documents the reservation.
2.2. IPv4 Addresses
The allocation and registration functions for all non-reserved,
globally unique unicast IPv4 addresses are handled by the Internet
Numbers Registry System in accordance with policies developed by the
RIRs in accordance with their processes.
Reservations of special-purpose IPv4 addresses can be found in the
IANA registry [IANA-IPv4-Reg]. Future additions to this registry can
be made through "IETF Review" as defined in [RFC5226]. Once a
reservation is approved, it is recorded in the special-purpose IPv4
address registry with a reference to the IESG-approved RFC that
documents the reservation.
2.3. IPv6 Addresses
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.
The allocation and registration functions for all non-reserved
globally unique unicast IPv6 addresses are handled by the Internet
Numbers Registry System in accordance with policies developed by the
RIRs in accordance with their processes.
Reservations of special-purpose IPv6 addresses can be found in the
IANA registry [IANA-IPv6-Reg]. Future additions to this registry can
be made through "IETF Review" as defined in [RFC5226]. Once a
reservation is approved, it is recorded in the special-purpose IPv6
address registry with a reference to the IESG-approved RFC that
documents the reservation.
3. IANA Considerations
IANA has created the "Special-Purpose AS Numbers" registry. Future
additions to this registry can be made through "IETF Review" as
defined in [RFC5226]. At this time, the special-purpose AS numbers
are:
AS Numbers Reason for Reservation
--------------------- -------------------------------------------
0 Reserved by [AS0-PROCESS]
23456 AS_TRANS; reserved by [RFC6793]
64496-64511 For documentation and sample code; reserved
by [RFC5398]
64512-65534 For private use; reserved by [RFC6996]
65535 Reserved by [RFC1930]
65536-65551 For documentation and sample code; reserved
by [RFC5398]
4200000000-4294967294 For private use; reserved by [RFC6996]
4294967295 Reserved by [LAST-AS-RES]
4. Security Considerations
This document identifies the IANA registries that are part of the
Internet Numbers Registry System at the time of publication. It does
not change the security posture of the Internet in any way.
Network operators should take care that special-purpose numbers and
addresses are used on the public Internet in a manner that is
consistent with their reserved purpose.
5. References
5.1. Normative References
[RFC2860] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of
Understanding Concerning the Technical Work of the Internet
Assigned Numbers Authority", RFC 2860, June 2000.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, May
2008.
[RFC7020] Housley, R., Curran, J., Huston, G., and D. Conrad, "The
Internet Numbers Registry System", RFC 7020, August 2013.
5.2. Informative References
[AS0-PROCESS]
Kumari, W., Bush, R., Schiller, H., and K. Patel,
"Codification of AS 0 processing", Work in Progress, August
2012.
[IANA-IPv4-Reg]
IANA, "IANA IPv4 Special-Purpose Address Registry",
<http://www.iana.org/assignments/
iana-ipv4-special-registry>.
[IANA-IPv6-Reg]
IANA, "IANA IPv6 Special-Purpose Address Registry",
<http://www.iana.org/assignments/
iana-ipv6-special-registry>.
[LAST-AS-RES]
Haas, J. and J. Mitchell, "Reservation of Last Autonomous
System (AS) Numbers", Work in Progress, April 2014.
[RFC1930] Hawkinson, J. and T. Bates, "Guidelines for creation,
selection, and registration of an Autonomous System (AS)",
BCP 6, RFC 1930, March 1996.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[RFC5398] Huston, G., "Autonomous System (AS) Number Reservation for
Documentation Use", RFC 5398, December 2008.
[RFC6793] Vohra, Q. and E. Chen, "BGP Support for Four-Octet
Autonomous System (AS) Number Space", RFC 6793, December
2012.
[RFC6996] Mitchell, J., "Autonomous System (AS) Reservation for
Private Use", BCP 6, RFC 6996, July 2013.
Acknowledgements
Many thanks to Jari Arkko, Scott Bradner, Brian Carpenter, David
Conrad, John Curran, David Farmer, Adrian Farrel, Stephen Farrell,
Brian Haberman, Geoff Huston, George Michaelson, S. Moonesamy, and
Thomas Narten for their insightful review and comment.
Author's Address
Russell Housley
Vigil Security, LLC
918 Spring Knoll Drive
Herndon, VA 20170
USA
EMail: housley@vigilsec.com
AI ELI5
On this page
§1What the Internet Numbers Registry System Is
RFC 7249 is a short companion to RFC 7020, which explains how the Internet Numbers Registry System distributes autonomous system (AS) numbers and globally unique IP address space. This document identifies exactly which registries are part of that system.
The Internet Numbers Registry System is a coordination of IANA registries and regional Internet registries (RIRs) that allocate network resources according to policies developed by the RIRs. The three registries at the heart of the system track AS numbers, IPv4 addresses, and IPv6 addresses.
The Internet Numbers Registry System is the official record of who gets what numbers and addresses. This document says which record books are part of that official system.
§2The Three Core Registries
Three IANA registries make up the Internet Numbers Registry System. However, each registry includes both allocated space and reserved special-purpose values, and the special-purpose values do not go through the Internet Numbers Registry System.
The three registries are: the Autonomous System (AS) Numbers registry, the IANA IPv4 Address Space Registry, and the IPv6 Global Unicast Address Assignments registry. Each handles the allocation of non-reserved space and maintains a registry of reserved values that serve specific purposes.
There are three main record books: one for AS numbers, one for IPv4 addresses, and one for IPv6 addresses. Each has both a list of numbers given out and a list of numbers saved for special uses.
§3Autonomous System Numbers
Historically, there are both 16-bit and 32-bit AS numbers, though the 16-bit AS numbers are simply the first 65,536 values of the 32-bit space (0 through 65535). The Internet Numbers Registry System handles allocation of all non-reserved AS numbers through the RIRs according to their policies.
Some AS numbers are reserved for special purposes: AS 0 is reserved, AS 23456 is used for AS number translation in RFC 6793, ranges like 64496-64511 and 64512-65534 are for documentation and private use respectively, and very large ranges such as 4200000000 to 4294967294 are also reserved for private use.
Every network on the Internet can have an AS number that tells other networks how to reach it. Some AS numbers are kept aside for special uses like examples in documentation.
§4IPv4 and IPv6 Address Space
The Internet Numbers Registry System handles allocation of globally unique unicast IP addresses in both IPv4 and IPv6. For IPv4, both allocated and reserved special-purpose addresses are tracked in the IANA registry.
For IPv6, about 7/8ths of the entire address space was reserved by the IETF for future global unicast use. The remaining unicast space is allocated through the Internet Numbers Registry System. Like IPv4, special-purpose IPv6 addresses are reserved and recorded separately.
Most IPv4 and IPv6 addresses are given out following rules, but some are saved for special purposes like testing or private networks.
§5Reserved and Special-Purpose Values
RFC 7249 explicitly establishes an IANA registry for special-purpose AS numbers. Future additions to this registry require IETF Review as defined in RFC 5226. Once a reservation is approved by the IETF, it is recorded in the special-purpose AS numbers registry with a reference to the RFC that documents it.
Similarly, special-purpose IPv4 and IPv6 addresses are maintained in separate IANA registries, each documented by approved RFCs. This separation ensures that the allocation system never hands out reserved numbers, and administrators know which values are reserved and why.
When the Internet needs to save some numbers for special uses, that decision goes through an official process and gets written down in a special list.