Internet DRAFT - draft-ietf-idr-as-private-reservation


Network Working Group                                        J. Mitchell
Internet-Draft                                     Microsoft Corporation
Updates: 1930 (if approved)                                 May 29, 2013
Intended status: Best Current Practice
Expires: November 30, 2013

           Autonomous System (AS) Reservation for Private Use


   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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   This Internet-Draft will expire on November 30, 2013.

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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, Border Gateway Protocol (BGP), documented in [RFC4271], has
   seen deployment in new application domains, such as datacenter
   networks, which require a larger Private Use AS Space.

   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 these 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",
   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 new
   network applications that utilize Private Use ASNs, two ranges of
   ASNs are reserved by this document in Section 6.  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 [RFC6793].

4.  Operational Considerations

   If Private Use ASNs are used and prefixes are originated from these
   ASNs, Private Use ASNs MUST be removed from AS path attributes
   (including AS4_PATH if utilizing four-octet AS number space) before
   being advertised to the global Internet.  Operators SHOULD ensure all
   EBGP speakers support [RFC6793] and 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 in the four-octet AS
   number space.  Some existing implementations that remove Private Use

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   ASNs from the AS_PATH are known to not 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 AS4_PATH, these implementations will likely
   cease to remove any Private Use ASNs from either of the AS path
   attributes.  Normal AS path filtering MAY also be used to prevent
   prefixes originating from Private Use ASNs from being advertised to
   the global Internet.

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, Joel Jaeggli, Warren Kumari, and
   Jeff Wheeler for their comments and suggestions.

6.  IANA Considerations

   [Note to IANA, this paragraph to be removed upon publication: The
   IANA should update the "16-bit Autonomous System Numbers" registry to
   reference this RFC for the existing Private Use reservation.  The end
   of the "32-bit Autonomous System Numbers" range will be reserved for
   Private Use, and a size of 94,967,295 (value to replace TBD1 below)
   corresponding to the range of 4200000000 (value to replace TBD2
   below) to 4294967294 (value to replace TBD3 below).  Text after this
   sentence should be published in the document.]

   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

   Private Use ASNs do not raise any unique security concerns.  Loss of
   connectivity might result from inappropriate use of them,
   specifically outside of a single organization, since they are not
   globally unique.  This loss of connectivity is limited to the
   organization using Private Use ASNs inappropriately or without
   reference to Section 4.  General BGP security considerations are

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   discussed in [RFC4271] and [RFC4272].  Identification of the
   originator of a route with a Private Use ASN in the AS path would
   have to be done by tracking the route back to the neighboring
   globally unique AS in the path or by inspecting other attributes.

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

8.2.  Informative References

   [IANA.AS]  IANA, "Autonomous System (AS) Numbers", May 2013,

   [RFC1930]  Hawkinson, J. and T. Bates, "Guidelines for creation,
              selection, and registration of an Autonomous System (AS)",
              BCP 6, RFC 1930, March 1996.

   [RFC4272]  Murphy, S., "BGP Security Vulnerabilities Analysis", RFC
              4272, January 2006.

Author's Address

   Jon Mitchell
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA  98052


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