Network Working Group J. Mitchell Internet-Draft Microsoft Corporation Updates: 1930 (if approved) June 20, 2012 Intended status: Informational Expires: December 22, 2012 Autonomous System (AS) Reservation for Private Use draft-mitchell-idr-as-private-reservation-00 Abstract This document describes the reservation of Autonomous System numbers (ASNs) that may be used within networks but 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. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as Mitchell Expires December 22, 2012 [Page 1] Internet-Draft Private Use AS Reservation June 2012 described in the Simplified BSD License. 1. Introduction The original IANA reservation of ASNs for private use was a block of 1023 ASNs. This was documented by IETF in Section 10 of [RFC1930] that specified the private use ASN range as 64512 through 65535 (implying the inclusion of ASN 65535). Since that range was reserved and documented over a decade ago, BGP has seen much wider deployment in Service Provider, Enterprise and Content Provider networks. The use cases in these networks for private use ASNs 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 for networks with requirements for multi-homing or provider redundancy. The limited size of the current range of private use ASNs has led to the usage 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 have been largely out of scope of 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 for reassignment in existing networks cannot be coordinated given these ASNs by definition are not registered. Therefore this document clarifies the existing ASN range, while 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, reserved block available out of the higher part of the Four-Octet AS Number Space [RFC4893]. Mitchell Expires December 22, 2012 [Page 2] Internet-Draft Private Use AS Reservation June 2012 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. Prior to making use of the second, numerically higher, range of these ASNs network operators should be confident any implementation specific features or filters that recognize private use ASNs have been updated to recognize both ranges correctly so that no unintended announcement of private use ASNs to the Internet occurs. 4. Acknowledgements The author would like to acknowledge Christopher Morrow and Jason Schiller for their advice on how to pursue this change. 5. IANA Considerations [Note to IANA, not for publication: The IANA may wish to consider updating the existing private use AS number reservation to explicitly include ASN 65535 that has been documented in RFC 1930 as well as implemented in a number of implementations that recognize private use ASNs as part of the existing range. Further, to maintain consistency from an operator standpoint, it is suggested that the end of the "32- bit number set" be reserved for Private Use, and a size of 967,295 is suggested corresponding to the range of 4294000000 to 4294967295 inclusive, primarily motivated by being visibly recognizable while not consuming a large portion of the total ASN space.] [Note to WG, not for publication: a small poll of network implementors was taken and it was not felt optimizing the range to a bit boundary was important for control plane performance of any features that recognize private use ASNs - others implementors in WG may want to weigh in here. Also very interested in feedback on appropriate sizing of the future range given the many current and future uses of BGP in networks] (If approved) IANA has reserved, for Private Use, a contiguous block of TBD (1023 or 1024) Autonomous System numbers from the "16-bit Autonomous System Numbers" registry, namely 64512 - TBD1 (65534 or 65535) inclusive. (If approved) IANA has also reserved, for Private Use, a contiguous block of TBD Autonomous System numbers from the "32-bit Autonomous System Numbers" registry, namely TBD2 - TBD3 inclusive. Mitchell Expires December 22, 2012 [Page 3] Internet-Draft Private Use AS Reservation June 2012 (If approved) These reservations have been documented in the IANA AS Number Registry [IANA.AS]. 6. Security Considerations This document does not introduce any additional security concerns in regards to private use ASNs. 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", June 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 USA Email: Jon.Mitchell@microsoft.com Mitchell Expires December 22, 2012 [Page 4]