Internet Engineering Task Force (IETF)                         G. Huston
Request for Comments: 9637                                         APNIC
Updates: 3849                                                N. Buraglio
Category: Informational                          Energy Sciences Network
ISSN: 2070-1721                                              August 2024


                 Expanding the IPv6 Documentation Space

Abstract

   The document describes the reservation of an additional IPv6 address
   prefix for use in documentation.  This update to RFC 3849 expands on
   the existing 2001:db8::/32 address block with the reservation of an
   additional, larger prefix.  The addition of a /20 prefix allows
   documented examples to more closely reflect a broader range of
   realistic, current deployment scenarios and more closely aligns with
   contemporary allocation models for large networks.

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 candidates for any level of Internet
   Standard; see 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/rfc9637.

Copyright Notice

   Copyright (c) 2024 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
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   publication of this document.  Please review these documents
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   Trust Legal Provisions and are provided without warranty as described
   in the Revised BSD License.

Table of Contents

   1.  Introduction
   2.  Requirements Language
   3.  Current Assignment and Allocation Data
   4.  Filtering and Appropriate Use
   5.  Security Considerations
   6.  IANA Considerations
   7.  References
     7.1.  Normative References
     7.2.  Informative References
   Acknowledgments
   Authors' Addresses

1.  Introduction

   [RFC3849] introduced the IPv6 address prefix 2001:db8::/32 as a
   reserved prefix for use in documentation.  The rationale for this
   reservation was to reduce the likelihood of conflict and confusion
   when relating documented examples to deployed systems.

   As the global deployment of IPv6 expands and evolves, individual IPv6
   network deployment scenarios have also increased in size and
   diversity, and there is a requirement for documentation to reflect
   this increased diversity and scope.  The original 2001:db8::/32
   reservation is inadequate to describe many realistic, current
   deployment scenarios.

   Without this additional address allocation, documentation prefixes
   are drawn from address blocks already allocated or assigned to
   existing organizations or well-known ISPs, or they are drawn from the
   currently unallocated address pool.  Such use conflicts with existing
   or future allocations or assignments of IPv6 address space.  The
   reservation of a /20 IPv6 address prefix from the Global Unicast
   Address pool [RFC4291] for documentation purposes allows such
   conflicts to be avoided.

2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Current Assignment and Allocation Data

   According to the allocation and assignment data published by the
   Regional Internet Registries (RIRs) (see [NROStatsReport]), in August
   2023, 25.9% of the 62,770 recorded IPv6 unicast allocations and
   assignments were larger than a /32 in size.  The most common
   allocation or assignment size was a /29, used in 24.8% of cases.

   The four largest assignments made to end users have been /19s, but
   these allocations were made before the RIRs moved away from the use
   of a fixed /48 site address prefix in IPv6 address assignment
   policies, and in the foreseeable future, it is unlikely that
   individual networks will require more than a /20.  It is believed
   that reservation of a /20 will cover the documentation needs as they
   relate to the broad range of realistic network deployments.

4.  Filtering and Appropriate Use

   Documentation prefixes are for the use of relaying configuration and
   documentation examples, and as such, they MUST NOT be used for actual
   traffic, MUST NOT be globally advertised, and SHOULD NOT be used
   internally for routed production traffic or other connectivity.
   Documentation prefixes should be considered bogon [BOGON] and
   filtered in routing advertisements as appropriate.

5.  Security Considerations

   This special-use prefix should be marked as and considered bogon
   [BOGON].  As is appropriate with bogon prefixes, packets whose source
   or destination belongs to this prefix should be dropped and
   disallowed over the public Internet.

6.  IANA Considerations

   IANA has registered the following in the "IANA IPv6 Special-Purpose
   Address Registry" [IANA-IPv6-SPAR].

   Address Block:  3fff::/20
   Name:  Documentation
   RFC:  RFC 9637
   Allocation Date  2024-07
   Termination Date:  N/A
   Source:  False
   Destination:  False
   Forwardable:  False
   Globally Reachable :  False
   Reserved-by-Protocol:  False

7.  References

7.1.  Normative References

   [IANA-IPv6-SPAR]
              IANA, "IANA IPv6 Special-Purpose Address Registry",
              <https://www.iana.org/assignments/iana-ipv6-special-
              registry>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

7.2.  Informative References

   [BOGON]    Team Cymru, "Unravelling the Mystery of Bogons: A senior
              stakeholder and IT professional guide", July 2023,
              <https://www.team-cymru.com/post/unravelling-the-mystery-
              of-bogons-a-senior-stakeholder-and-it-professional-guide>.

   [NROStatsReport]
              "NRO Stats Reports",
              <https://ftp.ripe.net/pub/stats/ripencc/nro-stats>.

   [RFC3849]  Huston, G., Lord, A., and P. Smith, "IPv6 Address Prefix
              Reserved for Documentation", RFC 3849,
              DOI 10.17487/RFC3849, July 2004,
              <https://www.rfc-editor.org/info/rfc3849>.

   [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>.

Acknowledgments

   The authors would like to acknowledge the valuable input from XiPeng
   Xiao, Chris Cummings, Russ White, Kevin Myers, Ed Horley, Tom
   Coffeen, and Scott Hogg.

Authors' Addresses

   Geoff Huston
   APNIC
   Email: gih@apnic.net


   Nick Buraglio
   Energy Sciences Network
   Email: buraglio@forwardingplane.net







ERRATA