Internet DRAFT - draft-mitchell-idr-as-private-reservation
draft-mitchell-idr-as-private-reservation
Network Working Group J. Mitchell
Internet-Draft Microsoft Corporation
Updates: 1930 (if approved) August 6, 2012
Intended status: Informational
Expires: February 7, 2013
Autonomous System (AS) Reservation for Private Use
draft-mitchell-idr-as-private-reservation-01
Abstract
This document describes the reservation of Autonomous System numbers
(ASNs) that are for private use only and should 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.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on February 7, 2013.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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 content provider 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 displacement of Frame
Relay and ATM based VPNs by BGP/MPLS IP VPNs [RFC4364] has also
increased the deployment of BGP to a larger number of sites,
especially in networks with requirements for multi-homing or provider
redundancy.
The limited size of the current range of private use ASNs has led to
the re-use of private use ASNs 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
[RFC4893], 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. Private Use ASNs
To allow the continued growth of usage of the BGP protocol in
networks that utilize private ASNs, two ranges of ASNs are reserved
by this document in Section 5. The first which was 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 [RFC4893].
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3. Operational Considerations
If private use ASNs are used and prefixes are originated from these
private use 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 filters or
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.
4. Acknowledgements
The author would like to acknowledge Christopher Morrow and Jason
Schiller for their advice on how to pursue this change. The author
also thanks Brian Dickson, David Farmer, and Jeffrey Haas for their
comments and suggestions.
5. 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 16777215 (value to replace
TBD1 below) is suggested corresponding to the range of 4278190080
(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].
6. Security Considerations
This document does not introduce any additional security concerns in
regards to private use ASNs.
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7. References
7.1. Normative References
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC4893] Vohra, Q. and E. Chen, "BGP Support for Four-octet AS
Number Space", RFC 4893, May 2007.
7.2. Informative References
[IANA.AS] IANA, "Autonomous System (AS) Numbers", August 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.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, February 2006.
Author's Address
Jon Mitchell
Microsoft Corporation
12012 Sunset Hills Road
Reston, VA 20190
USA
Email: Jon.Mitchell@microsoft.com
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