Network Working Group                                        J. Mitchell
Internet-Draft                                     Microsoft Corporation
Updates: 1930 (if approved)                             October 11,                            December 20, 2012
Intended status: Informational
Expires: April 14, June 23, 2013

           Autonomous System (AS) Reservation for Private Use


   This document describes the reservation of Autonomous System numbers
   (ASNs) that are for private use Private Use only and should not be advertised to
   the Internet, known as private use Private Use ASNs.  This document enlarges the
   total space available for private use Private Use ASNs by documenting the
   reservation of a second, larger range and updates RFC 1930. 1930 by
   replacing Section 10.

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1.  Introduction

   The original IANA reservation of Autonomous System Numbers (ASNs) for
   private use
   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 datacenter networks.  The places in these networks
   where private use 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

   The limited size of the current range of private use Private Use ASNs has led to
   the re-use of private use ASNs 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 Private Use cases.  The existing range
   of private use 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 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 Private Use 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-
   Four-Octet AS Number Space [I-D.ietf-idr-rfc4893bis]. [RFC6793].

3.  Operational Considerations

   If private use Private Use ASNs are used and prefixes are originated from these
   private use
   ASNs which are destined to the Internet, private use 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 Private Use ASNs have been updated
   to recognize both ranges prior to making use of the newer,
   numerically higher range of private use Private Use ASNs.  Some implementations
   of such features will fail to remove any Private Use ASNs from the
   AS_PATH if the AS_PATH contains a mix of Private Use and non-Private
   Use ASNs and if these implementations are not updated, the newer
   range may be classified as the later.  Normal AS_PATH filtering may
   also be used to limit prefixes originating from Private Use ASNs from
   being advertised to the global Internet and can help in transition
   scenarios until the implementation specific features that manipulate
   AS_PATH are updated.

4.  Acknowledgements

   The author would like to acknowledge Christopher Morrow and Morrow, Jason
   Schiller, and John Scudder for their advice on how to pursue this
   change.  The author would also thanks like to thank Brian Dickson, David
   Farmer, and Jeffrey Haas Haas, Nick Hilliard, Warren Kumari, and Jeff Wheeler
   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 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 94,967,295 (value to replace
   TBD1 below) is suggested corresponding to the range of 4278190080 4200000000
   (value to replace TBD2 below) to 4294967294 (value to replace TBD3

   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 Private Use ASNs.

7.  References

7.1.  Normative References

              Vohra, Q. and E. Chen, "BGP Support for Four-octet AS
              Number Space", draft-ietf-idr-rfc4893bis-07 (work in
              progress), June 2012.

   [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.

7.2.  Informative References

   [IANA.AS]  IANA, "Autonomous System (AS) Numbers", October December 2012,

   [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