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2 IDR J. Haas
3 Internet-Draft Juniper Networks
4 Intended status: Informational J. Mitchell
5 Expires: April 18, 2014 Microsoft Corporation
6 October 15, 2013
8 Reservation of Last Autonomous System (AS) Numbers
9 draft-ietf-idr-last-as-reservation-01
11 Abstract
13 This document reserves two Autonomous System numbers (ASNs) at the
14 end of the 16 bit and 32 bit ranges, described in this document as
15 "Last ASNs" and provides guidance to implementers and operators on
16 their use.
18 Status of This Memo
20 This Internet-Draft is submitted in full conformance with the
21 provisions of BCP 78 and BCP 79.
23 Internet-Drafts are working documents of the Internet Engineering
24 Task Force (IETF). Note that other groups may also distribute
25 working documents as Internet-Drafts. The list of current Internet-
26 Drafts is at http://datatracker.ietf.org/drafts/current/.
28 Internet-Drafts are draft documents valid for a maximum of six months
29 and may be updated, replaced, or obsoleted by other documents at any
30 time. It is inappropriate to use Internet-Drafts as reference
31 material or to cite them other than as "work in progress."
33 This Internet-Draft will expire on April 18, 2014.
35 Copyright Notice
37 Copyright (c) 2013 IETF Trust and the persons identified as the
38 document authors. All rights reserved.
40 This document is subject to BCP 78 and the IETF Trust's Legal
41 Provisions Relating to IETF Documents
42 (http://trustee.ietf.org/license-info) in effect on the date of
43 publication of this document. Please review these documents
44 carefully, as they describe your rights and restrictions with respect
45 to this document. Code Components extracted from this document must
46 include Simplified BSD License text as described in Section 4.e of
47 the Trust Legal Provisions and are provided without warranty as
48 described in the Simplified BSD License.
50 1. Introduction
52 IANA has reserved the last Autonomous System Number (ASN), 65535, of
53 the 16 bit autonomous system number range for over a decade with the
54 intention that it not be used by network operators running BGP
55 [RFC4271]. Since the introduction of BGP Support for Four-Octet AS
56 Number Space [RFC6793], IANA has also reserved the ASN of the 32 bit
57 autonomous system number range, 4294967295. This reservation has
58 been documented in the IANA Autonomous System Numbers Registry
59 [IANA.AS]. Although these "Last ASNs" border on Private Use ASN
60 [RFC6996] ranges, they are not defined or reserved as Private Use
61 ASNs by [IANA.AS]. This document describes the reasoning for
62 reserving these Last ASNs and provides guidance both to operators and
63 to implementers on their use.
65 2. Requirements Language
67 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
68 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
69 document are to be interpreted as described in RFC 2119 [RFC2119].
71 3. Reasons for Last ASNs Reservation
73 A subset of the BGP communities of ASN 65535, the last ASN of the 16
74 bit range, are reserved for use by Well-known communities as
75 described in [RFC1997] and [IANA.WK]. Although this is not currently
76 true of ASN 4294967295, if there is a future need for another Special
77 Use ASN that is not designed to be globally routable, or the
78 associated BGP communities of such an ASN, ASN 4294967295 could be a
79 valid candidate for such purpose. This document does not prescribe
80 any such Special Use to this ASN at the time of publication.
82 4. Operational Considerations
84 Operators SHOULD NOT use these Last ASNs as if they are Private Use
85 ASNs or for any other purpose. Operational use of these Last ASNs
86 could have undesirable results. For example; use of AS 65535 as if
87 it were a Private Use ASN, may result in inadvertent use of BGP Well-
88 known Community values [IANA.WK], causing undesireable routing
89 behavior.
91 These last ASNs MUST NOT be advertised to the global Internet within
92 AS_PATH or AS4_PATH attributes. Operators that choose to do inbound
93 filtering of Private Use ASNs within the AS_PATH and AS4_PATH
94 attributes SHOULD also filter these Last ASNs.
96 5. Implementation Considerations
97 While these Last ASNs are reserved, they remain valid ASNs from a BGP
98 protocol perspective. Therefore, implementations of BGP [RFC4271]
99 SHOULD NOT treat the use of these Last ASNs as any type of protocol
100 error. However, implementations MAY generate a local warning message
101 indicating improper use of a reserved ASN.
103 Implementations that provide tools that filter Private Use ASNs
104 within the AS_PATH and AS4_PATH attributes MAY also include these
105 Last ASNs.
107 6. IANA Considerations
109 IANA has reserved last Autonomous System number 65535 from the
110 "16-bit Autonomous System Numbers" registry for the reasons described
111 in this document.
113 IANA has also reserved last Autonomous System number 4294967295 from
114 the "32-bit Autonomous System Numbers" registry for the reasons
115 described in this document.
117 This reservation has been documented in the IANA Autonomous System
118 Numbers Registry [IANA.AS].
120 7. Security Considerations
122 This document does not introduce any additional security concerns in
123 regards to usage of Last ASNs. Although the BGP protocol is designed
124 to allow usage of these Last ASNs, security issues related to BGP
125 implementation errors could be triggered by Last ASN usage.
127 8. References
129 8.1. Normative References
131 [IANA.AS] IANA, ., "Autonomous System (AS) Numbers", October 2013,
132 .
134 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
135 Requirement Levels", BCP 14, RFC 2119, March 1997.
137 [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
138 Protocol 4 (BGP-4)", RFC 4271, January 2006.
140 [RFC6793] Vohra, Q. and E. Chen, "BGP Support for Four-Octet
141 Autonomous System (AS) Number Space", RFC 6793, December
142 2012.
144 8.2. Informative References
146 [IANA.WK] IANA, ., "Border Gateway Protocol (BGP) Well-known
147 Communities", October 2013, .
150 [RFC1997] Chandrasekeran, R., Traina, P., and T. Li, "BGP
151 Communities Attribute", RFC 1997, August 1996.
153 [RFC6996] Mitchell, J., "Autonomous System (AS) Reservation for
154 Private Use", BCP 6, RFC 6996, July 2013.
156 Appendix A. Acknowledgements
158 The authors would like to thank Michelle Cotton and Elwyn Davis for
159 encouraging the proper documentation of the reservation of these ASNs
160 and David Farmer for his contributions to the document.
162 Authors' Addresses
164 Jeffrey Haas
165 Juniper Networks
167 Email: jhaas@juniper.net
169 Jon Mitchell
170 Microsoft Corporation
171 One Microsoft Way
172 Redmond, WA 98052
173 USA
175 Email: Jon.Mitchell@microsoft.com