Network Working Group J. Mitchell
Internet-Draft Microsoft Corporation
Updates: 1930 (if approved) December 21, 2012
Intended status: BCP
Expires: June 24, 2013
Autonomous System (AS) Reservation for Private Use
draft-ietf-idr-as-private-reservation-02
Abstract
This document describes the reservation of Autonomous System numbers
(ASNs) that are for Private Use only and MUST NOT be advertised to
the Internet, known as Private Use ASNs. This document enlarges the
total space available for Private Use ASNs by documenting the
reservation of a second, larger range and updates RFC 1930 by
replacing Section 10.
Status of this Memo
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Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
1. Introduction
The original IANA reservation of Autonomous System Numbers (ASNs) for
Private Use was a block of 1023 ASNs. This was also documented by
IETF in Section 10 of [RFC1930]. Since the time when that range was
reserved, BGP has seen much wider deployment in service provider,
enterprise, and datacenter networks. The places in these networks
where Private Use ASNs are in use include networks that are attached
to the Internet, utilizing implementation specific features to remove
them upon advertisement to Internet peers, and networks that are not
attached to the Internet.
The limited size of the current range of Private Use ASNs has led to
the re-use of the same ASN within a single organization, requiring
the use of a number of implementation specific features that
manipulate the AS_PATH or remove AS_PATH based loop prevention
described in Section 9 of [RFC4271]. These workarounds have
increased the operational complexity of the networks since the
implementations of these functions vary and are not defined in
existing BGP standards.
Since the introduction of BGP Support for Four-octet AS Number Space
[RFC6793], the total size of the ASN space has increased
dramatically, and a larger subset of the space should be available to
network operators to deploy in Private Use cases. The existing range
of Private Use ASNs is widely deployed and the ability to renumber
this resource in existing networks cannot be coordinated given these
ASNs by definition are not registered. Therefore this documents the
existing Private Use ASN reservation, while also introducing a
second, larger range that can also be utilized.
2. 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].
3. Private Use ASNs
To allow the continued growth of usage of the BGP protocol in
networks that utilize Private Use ASNs, two ranges of ASNs are
reserved by this document in Section 6. The first which was
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previously defined in [RFC1930] out of the original 16-bit Autonomous
System range and a second, larger range out of the higher part of the
Four-Octet AS Number Space [RFC6793].
4. Operational Considerations
If Private Use ASNs are used and prefixes are originated from these
ASNs which are destined to the Internet, Private Use ASNs MUST be
removed from the AS_PATH before being advertised to the global
Internet. Operators are cautioned to ensure any implementation
specific features that recognize Private Use ASNs have been updated
to recognize both ranges prior to making use of the newer,
numerically higher range of Private Use ASNs. Some existing
implementations that remove Private Use ASNs from the AS_PATH may
fail to remove Private Use ASNs if the AS_PATH contains a mixture of
Private Use and Non-Private Use ASNs. If such implementations have
not been updated to recognize the new range of ASNs in this document
and a mix of old and new range Private Use ASNs exist in the path,
these implementations may cease to remove any Private Use ASNs from
the AS_PATH. Normal AS_PATH filtering may be used to prevent
prefixes originating from Private Use ASNs from being advertised to
the global Internet. Using AS_PATH filtering to filter the new range
of Private Use ASNs on a network may also mitigate the leaking of
Private Use ASNs to the global Internet in certain cases. These
cases include the case where a network is reliant on AS_PATH
manipulation features that have not been updated to recognize the new
range as described above.
5. Acknowledgements
The author would like to acknowledge Christopher Morrow, Jason
Schiller, and John Scudder for their advice on how to pursue this
change. The author would also like to thank Brian Dickson, David
Farmer, Jeffrey Haas, Nick Hilliard, Warren Kumari, and Jeff Wheeler
for their comments and suggestions.
6. IANA Considerations
[Note to IANA, NOT for publication: The IANA should update the "16-
bit Autonomous System Numbers" registry to reference this RFC (when
published) for the existing Private Use reservation. Further, to
maintain consistency from an operator standpoint, it is suggested
that the end of the "32-bit Autonomous System Numbers" range be
reserved for Private Use, and a size of 94,967,295 (value to replace
TBD1 below) is suggested corresponding to the range of 4200000000
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(value to replace TBD2 below) to 4294967294 (value to replace TBD3
below).]
IANA has reserved, for Private Use, a contiguous block of 1023
Autonomous System numbers from the "16-bit Autonomous System Numbers"
registry, namely 64512 - 65534 inclusive.
IANA has also reserved, for Private Use, a contiguous block of TBD1
Autonomous System numbers from the "32-bit Autonomous System Numbers"
registry, namely TBD2 - TBD3 inclusive.
These reservations have been documented in the IANA Autonomous System
Numbers Registry [IANA.AS].
7. Security Considerations
This document does not introduce any additional security concerns in
regards to Private Use ASNs.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC6793] Vohra, Q. and E. Chen, "BGP Support for Four-Octet
Autonomous System (AS) Number Space", RFC 6793,
December 2012.
8.2. Informative References
[IANA.AS] IANA, "Autonomous System (AS) Numbers", December 2012,
<http://www.iana.org/assignments/as-numbers/>.
[RFC1930] Hawkinson, J. and T. Bates, "Guidelines for creation,
selection, and registration of an Autonomous System (AS)",
BCP 6, RFC 1930, March 1996.
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Author's Address
Jon Mitchell
Microsoft Corporation
12012 Sunset Hills Road
Reston, VA 20190
USA
Email: Jon.Mitchell@microsoft.com
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