RFC 5398

RFC 5398: Autonomous System (AS) Number Reservation for Documentation Use 🦋

okay bestie, so this is RFC 5398 💖 It's from the Network Working Group, written by Geoff Huston (contact: gih@apnic.net 🫶), and it's dated December 2008. It's Informational, which means it's sharing useful info and is NOT an Internet standard 🌸 The title block doesn't list anything it obsoletes or updates, so there's nothing to chase there ✨

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. 💅

Copyright Notice ⚖️

Copyright (c) 2008 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. 🙈

Abstract 🌈

so, to cut down on conflicts and confusion when documented examples meet real deployed systems, two blocks of Autonomous System numbers (ASNs) are reserved for examples in RFCs, books, documentation, and stuff like that. This document is the one that reserves those two blocks as numbers for documentation use 🧚

1. Introduction 💜

bestie, same energy as the abstract: two blocks of ASNs are set aside so examples in RFCs, books, and documentation don't collide with real deployed systems 😭

The problems these conflicts cause have already shown up with IPv4 addresses. When someone copies a documented example literally into a production environment, it causes address and routing conflicts with existing services 💀 Private-use ASNs already have a context of use in deployed networks, so they can't be used in lots of example situations. By explicitly allocating a set of AS numbers for documentation use, the hope is that these operational problems get avoided going forward ✨

Similar thinking has already gone into IPv4 addresses [IANA.IPv4], IPv6 addresses [RFC3849], and domain names [RFC2606], and reservations were made for similar purposes there too 🦋

2. ASNs for Documentation Use 🍓

For documentation to describe deployment examples accurately, using public or private-use AS numbers is inappropriate, and a reserved block of AS numbers is required 🫶 This makes sure documentation doesn't clash with public or private-use AS numbers in deployed networks. It also lowers the risk to operational integrity that comes from using documentation to literally configure routing elements on production systems 🔥

Next up is the move to 32-bit AS numbers. To describe examples of that transition correctly, this document proposes reserving two blocks of AS numbers. The first is a block of 16 contiguous AS numbers in the range that can be written as a 16-bit AS number (values less than 65536). The second is a block of 16 contiguous AS numbers in the range that can only be written as 32-bit AS numbers (values greater than 65535) 👑

3. Operational Implications 🌸

This assignment implies that BGP operational configurations should not peer with neighboring ASes that are numbered from this reserved AS number set. so, don't peer with these 🙅‍♀️

4. IANA Considerations 🧚

IANA reserved a contiguous block of 16 Autonomous System numbers from the unallocated number range within the "16-bit" number set for documentation purposes: 64496 - 64511. IANA also reserved a contiguous block of 16 Autonomous System numbers from the "32-bit" number set for documentation: 65536 - 65551. These reservations are documented in the IANA AS Number Registry [IANA.AS] 💖

5. Security Considerations 💀

AS number reservations do not have any direct impact on Internet infrastructure security. Full stop. These numbers are a documentation tool, so the reservation itself doesn't touch the security of the Internet's infrastructure 🔒

6. Acknowledgements 🫶

The author thanks Tomoya Yoshida, Gaurab Upadhaya, and Philip Smith for writing a policy proposal submitted to the APNIC Policy Process in 2008 about reserving AS numbers for documentation purposes. Iconic teamwork 👑

7. Informative References 📚

[IANA.AS]    IANA, "Autonomous System (AS) Numbers", Sep 2008,
             <http://www.iana.org>.

[IANA.IPv4]  IANA, "IPv4 Global Unicast Address Assignments",
             Sep 2008, <http://www.iana.org>.

[RFC2606]    Eastlake, D. and A. Panitz, "Reserved Top Level DNS
             Names", BCP 32, RFC 2606, June 1999.

[RFC3849]    Huston, G., Lord, A., and P. Smith, "IPv6 Address Prefix
             Reserved for Documentation", RFC 3849, July 2004.

Author's Address 🎀

Geoff Huston

EMail: gih@apnic.net