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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: draft-ietf-idr-as-private-reservation has been published as RFC 6996 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group J. Haas 3 Internet-Draft Juniper Networks 4 Intended status: Informational J. Mitchell 5 Expires: November 17, 2013 Microsoft Corporation 6 May 16, 2013 8 Last Autonomous System (AS) Reservations 9 draft-jhjm-idr-last-as-reservations-00 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 recommends they not be used by operators. 17 Status of This Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at http://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on November 17, 2013. 34 Copyright Notice 36 Copyright (c) 2013 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (http://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 1. Introduction 51 IANA has reserved the last Autonomous System Number (ASN), 65535, of 52 the 16 bit autonomous system number range for over a decade with the 53 intention that it not be used by BGP [RFC4271] network operators. 54 Since the introduction of BGP Support for Four-Octet AS Number Space 55 [RFC6793], IANA has also reserved the ASN of the 32 bit autonomous 56 system number range, 4294967295. These reservations have been 57 documented in the IANA Autonomous System Numbers Registry [IANA.AS]. 58 Although these "Last ASNs" border on Private Use ASN ranges, they are 59 not defined as Private Use ASNs by 60 [I-D.ietf-idr-as-private-reservation]. This document describes the 61 reasoning for these reservations and provides guidance both to 62 operators and to authors of future protocol enhancements on their 63 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 ASN Reservations 73 The primary reason for reserving the Last ASNs of the 16 bit and 32 74 bit ASN ranges is that these numbers are also at the end of typical 75 computational data structures holding the underlying number. 76 Programmatic errors are more common when handling of end of range 77 values, and sometimes last values (binary all ones) have been used as 78 "magic numbers", to represent a different number or behavior. 80 Secondly, a subset of the standard BGP communities of the last ASN of 81 the 16 bit range, 65535, are reserved for use by Well-known 82 communities as described in RFC 1997 [RFC1997] and IANA [IANA.WK]. 83 Although this not currently true of ASN 4294967295, if there is a 84 future need for a Special Use ASN that is not designed to be globally 85 routable, or the associated BGP attributes (such as communities) of 86 such an ASN, this may be a valid candidate for such purpose. This 87 document does not prescribe any such purpose to this ASN. 89 4. Operational Considerations 91 Operators MUST NOT use Last ASNs as if they are Private Use ASNs, or 92 for any other purpose, since they are reserved and implementations 93 may have errors in regards to handling these ASNs. Implementations 94 SHOULD NOT handle Last ASNs in the same fashion as Private Use ASNs. 95 Operators are accustomed to being able to fully utilize the 96 communities associated with the ASN's they have deployed utilizing 97 the format described in RFC 1997 [RFC1997], even in the case of 98 Private Use ASNs. In the case of usage of ASN 65535 as if it was a 99 Private Use ASN, operators might not recognize these communities are 100 reserved as BGP Well-known community values [IANA.WK], causing 101 undesirable routing behavior if prefixes are tagged with such 102 communities within the network. 104 Operators that choose to filter or provide tools that filter AS_PATH, 105 MAY choose to filter Last ASNs in the same way as Private Use ASNs, 106 to prevent the use of these reserved ASNs on their networks. 108 5. Acknowledgements 110 The author would like to thank Michelle Cotton and Elwyn Davis for 111 encouraging the proper documentation of the reservation of these 112 ASNs. 114 6. IANA Considerations 116 IANA has reserved Autonomous System number 65535 from the "16-bit 117 Autonomous System Numbers" registry for the reasons described in this 118 document. 120 IANA has also reserved Autonomous System number 4294967295 from the 121 "32-bit Autonomous System Numbers" registry for the reasons described 122 in this document. 124 These reservations have been documented in the IANA Autonomous System 125 Numbers Registry [IANA.AS]. 127 7. Security Considerations 129 This document does not introduce any additional security concerns in 130 regards to the Last ASNs usage. Although the BGP protocol is 131 designed to allow usage of these Last ASNs, security issues related 132 to BGP implementation errors may be triggered by Last ASN usage. 134 8. References 136 8.1. Normative References 138 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 139 Requirement Levels", BCP 14, RFC 2119, March 1997. 141 [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway 142 Protocol 4 (BGP-4)", RFC 4271, January 2006. 144 [RFC6793] Vohra, Q. and E. Chen, "BGP Support for Four-Octet 145 Autonomous System (AS) Number Space", RFC 6793, December 146 2012. 148 8.2. Informative References 150 [I-D.ietf-idr-as-private-reservation] 151 Mitchell, J., "Autonomous System (AS) Reservation for 152 Private Use", draft-ietf-idr-as-private-reservation-04 153 (work in progress), April 2013. 155 [IANA.AS] IANA, "Autonomous System (AS) Numbers", May 2013, 156 . 158 [IANA.WK] IANA, "Border Gateway Protocol (BGP) Well-known 159 Communities", May 2013, . 162 [RFC1997] Chandrasekeran, R., Traina, P., and T. Li, "BGP 163 Communities Attribute", RFC 1997, August 1996. 165 Authors' Addresses 167 Jeffrey Haas 168 Juniper Networks 170 Email: jhaas@juniper.net 172 Jon Mitchell 173 Microsoft Corporation 174 One Microsoft Way 175 Redmond, WA 98052 176 USA 178 Email: Jon.Mitchell@microsoft.com