draft-ietf-idr-last-as-reservation-00.txt   draft-ietf-idr-last-as-reservation-01.txt 
IDR J. Haas IDR J. Haas
Internet-Draft Juniper Networks Internet-Draft Juniper Networks
Intended status: Informational J. Mitchell Intended status: Informational J. Mitchell
Expires: January 16, 2014 Microsoft Corporation Expires: April 18, 2014 Microsoft Corporation
July 15, 2013 October 15, 2013
Reservation of Last Autonomous System (AS) Numbers Reservation of Last Autonomous System (AS) Numbers
draft-ietf-idr-last-as-reservation-00 draft-ietf-idr-last-as-reservation-01
Abstract Abstract
This document reserves two Autonomous System numbers (ASNs) at the This document reserves two Autonomous System numbers (ASNs) at the
end of the 16 bit and 32 bit ranges, described in this document as end of the 16 bit and 32 bit ranges, described in this document as
"Last ASNs" and provides guidance to implementers and operators on "Last ASNs" and provides guidance to implementers and operators on
their use. their use.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 16, 2014. This Internet-Draft will expire on April 18, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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1. Introduction 1. Introduction
IANA has reserved the last Autonomous System Number (ASN), 65535, of IANA has reserved the last Autonomous System Number (ASN), 65535, of
the 16 bit autonomous system number range for over a decade with the the 16 bit autonomous system number range for over a decade with the
intention that it not be used by network operators running BGP intention that it not be used by network operators running BGP
[RFC4271]. Since the introduction of BGP Support for Four-Octet AS [RFC4271]. Since the introduction of BGP Support for Four-Octet AS
Number Space [RFC6793], IANA has also reserved the ASN of the 32 bit Number Space [RFC6793], IANA has also reserved the ASN of the 32 bit
autonomous system number range, 4294967295. This reservation has autonomous system number range, 4294967295. This reservation has
been documented in the IANA Autonomous System Numbers Registry been documented in the IANA Autonomous System Numbers Registry
[IANA.AS]. Although these "Last ASNs" border on Private Use ASN [IANA.AS]. Although these "Last ASNs" border on Private Use ASN
ranges, they are not defined as Private Use ASNs by [RFC6996] ranges, they are not defined or reserved as Private Use
[I-D.ietf-idr-as-private-reservation]. This document describes the ASNs by [IANA.AS]. This document describes the reasoning for
reasoning for reserving these Last ASNs and provides guidance both to reserving these Last ASNs and provides guidance both to operators and
operators and to implementers on their use. to implementers on their use.
2. Requirements Language 2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
3. Reasons for Last ASNs Reservation 3. Reasons for Last ASNs Reservation
The primary reason for reserving the Last ASN of both the 16 bit and A subset of the BGP communities of ASN 65535, the last ASN of the 16
32 bit ASN ranges is that these numbers are also at the end of bit range, are reserved for use by Well-known communities as
typical computational data structures holding the underlying number. described in [RFC1997] and [IANA.WK]. Although this is not currently
Programmatic errors are more common when handling of end of range true of ASN 4294967295, if there is a future need for another Special
values, and sometimes last values (binary all ones) have been used as Use ASN that is not designed to be globally routable, or the
"magic numbers", to represent a different number or behavior. associated BGP communities of such an ASN, ASN 4294967295 could be a
valid candidate for such purpose. This document does not prescribe
Secondly, a subset of the standard BGP communities of the last ASN of any such Special Use to this ASN at the time of publication.
the 16 bit range, 65535, are reserved for use by Well-known
communities as described in [RFC1997] and [IANA.WK]. Although this
not currently true of ASN 4294967295, if there is a future need for a
Special Use ASN that is not designed to be globally routable, or the
associated BGP attributes (such as communities) of such an ASN, this
could be a valid candidate for such purpose. This document does not
prescribe any such purpose to this ASN.
4. Operational Considerations 4. Operational Considerations
Operators MUST NOT use these Last ASNs as if they are Private Use Operators SHOULD NOT use these Last ASNs as if they are Private Use
ASNs, and SHOULD NOT use these Last ASNs for any other purpose, ASNs or for any other purpose. Operational use of these Last ASNs
except a Special Uses defined elsewhere. Any other operational use could have undesirable results. For example; use of AS 65535 as if
of these Last ASNs could have unpredictable or undesirable results. it were a Private Use ASN, may result in inadvertent use of BGP Well-
For example; use of AS 65535 as if it were a Private Use ASN, may known Community values [IANA.WK], causing undesireable routing
result in inadvertent use of BGP Well-known community values behavior.
[IANA.WK], causing undesired routing behavior.
Operators that choose to filter Private Use ASNs within the AS_PATH These last ASNs MUST NOT be advertised to the global Internet within
and AS4_PATH attributes SHOULD also filter these Last ASNs. These AS_PATH or AS4_PATH attributes. Operators that choose to do inbound
last ASNs MUST NOT be advertised to the global Internet within filtering of Private Use ASNs within the AS_PATH and AS4_PATH
AS_PATH or AS4_PATH attributes. attributes SHOULD also filter these Last ASNs.
5. Implementation Considerations 5. Implementation Considerations
While these Last ASNs are reserved, they remain valid ASNs from a BGP
While these Last ASNs are reserved, they remain valid ASNs from a
protocol perspective. Therefore, implementations of BGP [RFC4271] protocol perspective. Therefore, implementations of BGP [RFC4271]
SHOULD NOT treat the use of these Last ASNs as any type of protocol SHOULD NOT treat the use of these Last ASNs as any type of protocol
error. However, implementations MAY generate a local warning message error. However, implementations MAY generate a local warning message
indicating probable improper use of a reserved ASN. indicating improper use of a reserved ASN.
Implementations that provide tools that filter Private Use ASNs Implementations that provide tools that filter Private Use ASNs
within the AS_PATH and AS4_PATH attributes MAY also include these within the AS_PATH and AS4_PATH attributes MAY also include these
Last ASNs. Last ASNs.
6. IANA Considerations 6. IANA Considerations
IANA has reserved last Autonomous System number 65535 from the IANA has reserved last Autonomous System number 65535 from the
"16-bit Autonomous System Numbers" registry for the reasons described "16-bit Autonomous System Numbers" registry for the reasons described
in this document. in this document.
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This document does not introduce any additional security concerns in This document does not introduce any additional security concerns in
regards to usage of Last ASNs. Although the BGP protocol is designed regards to usage of Last ASNs. Although the BGP protocol is designed
to allow usage of these Last ASNs, security issues related to BGP to allow usage of these Last ASNs, security issues related to BGP
implementation errors could be triggered by Last ASN usage. implementation errors could be triggered by Last ASN usage.
8. References 8. References
8.1. Normative References 8.1. Normative References
[IANA.AS] IANA, ., "Autonomous System (AS) Numbers", July 2013, [IANA.AS] IANA, ., "Autonomous System (AS) Numbers", October 2013,
<http://www.iana.org/assignments/as-numbers/>. <http://www.iana.org/assignments/as-numbers/>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006. Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC6793] Vohra, Q. and E. Chen, "BGP Support for Four-Octet [RFC6793] Vohra, Q. and E. Chen, "BGP Support for Four-Octet
Autonomous System (AS) Number Space", RFC 6793, December Autonomous System (AS) Number Space", RFC 6793, December
2012. 2012.
8.2. Informative References 8.2. Informative References
[I-D.ietf-idr-as-private-reservation]
Mitchell, J., "Autonomous System (AS) Reservation for
Private Use", draft-ietf-idr-as-private-reservation-05
(work in progress), May 2013.
[IANA.WK] IANA, ., "Border Gateway Protocol (BGP) Well-known [IANA.WK] IANA, ., "Border Gateway Protocol (BGP) Well-known
Communities", July 2013, <http://www.iana.org/assignments/ Communities", October 2013, <http://www.iana.org/
bgp-well-known-communities/>. assignments/bgp-well-known-communities/>.
[RFC1997] Chandrasekeran, R., Traina, P., and T. Li, "BGP [RFC1997] Chandrasekeran, R., Traina, P., and T. Li, "BGP
Communities Attribute", RFC 1997, August 1996. Communities Attribute", RFC 1997, August 1996.
[RFC6996] Mitchell, J., "Autonomous System (AS) Reservation for
Private Use", BCP 6, RFC 6996, July 2013.
Appendix A. Acknowledgements Appendix A. Acknowledgements
The authors would like to thank Michelle Cotton and Elwyn Davis for The authors would like to thank Michelle Cotton and Elwyn Davis for
encouraging the proper documentation of the reservation of these encouraging the proper documentation of the reservation of these ASNs
ASNs. The authors would also like to thank David Farmer for his and David Farmer for his contributions to the document.
contributions to the document.
Authors' Addresses Authors' Addresses
Jeffrey Haas Jeffrey Haas
Juniper Networks Juniper Networks
Email: jhaas@juniper.net Email: jhaas@juniper.net
Jon Mitchell Jon Mitchell
Microsoft Corporation Microsoft Corporation
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