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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 4893 (Obsoleted by RFC 6793) Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group D. Rao 3 Internet-Draft Cisco Systems 4 Intended status: Standards Track P. Mohapatra 5 Expires: December 9, 2015 Sproute Networks 6 J. Haas 7 Juniper Networks 8 June 7, 2015 10 Generic Subtype for BGP Four-octet AS specific extended community 11 draft-ietf-idr-as4octet-extcomm-generic-subtype-08 13 Abstract 15 Maintaining the current best practices with communities, ISPs and 16 enterprises that are assigned a 4-octet AS number may want the BGP 17 UPDATE messages they receive from their customers or peers to include 18 a 4-octet AS specific BGP extended community. This document defines 19 a new sub-type within the four-octet AS specific extended community 20 to facilitate this practice. 22 Status of this Memo 24 This Internet-Draft is submitted to IETF in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on December 9, 2015. 39 Copyright Notice 41 Copyright (c) 2015 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 57 1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3 58 2. Generic Sub-type Definition . . . . . . . . . . . . . . . . . . 3 59 3. Deployment Considerations . . . . . . . . . . . . . . . . . . . 4 60 4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5 61 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 62 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 63 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 64 7.1. Normative References . . . . . . . . . . . . . . . . . . . 5 65 7.2. Informative References . . . . . . . . . . . . . . . . . . 6 66 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 68 1. Introduction 70 Maintaining the current best practices with communities, ISPs and 71 enterprises that are assigned a 4-octet AS number may want the BGP 72 UPDATE messages they receive from their customers or peers to include 73 a 4-octet AS specific extended community. This document defines a 74 new sub-type within the four-octet AS specific extended community to 75 facilitate this practice. 77 For example, [RFC1998] describes an application of BGP community 78 attribute ([RFC1997]) to implement flexible routing policies for 79 sites multi-homed to one or multiple providers. In a two-octet AS 80 environment, the advertised routes are usually associated with a 81 community attribute that encodes the provider's AS number in the 82 first two octets of the community and a LOCAL_PREF value in the 83 second two octets of the community. The community attribute signals 84 the provider edge routers connected to the site to set the 85 corresponding LOCAL_PREF on their advertisements to the IBGP mesh. In 86 this way, customers can put into practice topologies like active- 87 backup. 89 When such a provider is assigned a four-octet AS number, the existing 90 mechanism of using communities is not sufficient since the AS portion 91 of the RFC 1997 community cannot exceed two bytes. The natural 92 alternative is to extend the same mechanism using extended 93 communities since it allows for encoding eight bytes of information. 95 [RFC5668] defines a format for a four-octet AS specific extended 96 community with a designated type field. That document defines two 97 sub-types: Four-octet specific Route Target extended community and 98 Four-octet specific Route Origin extended community. This document 99 specifies a generic sub-type for the four-octet AS specific extended 100 community to provide benefits such as the one cited above as the 101 Internet migrates to four-octet AS space. 103 1.1. Requirements Language 105 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 106 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 107 document are to be interpreted as described in RFC 2119 [RFC2119]. 109 2. Generic Sub-type Definition 110 0 1 2 3 111 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 112 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 113 | 0x02 or 0x42 | 0x04 | Global | 114 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 115 | Administrator | Local Administrator | 116 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 118 This is an extended type with Type Field comprising of 2 octets and 119 Value Field comprising of 6 octets. 121 The high-order octet of this extended type is set to either 0x02 (for 122 transitive communities) or 0x42 (for non-transitive communities). The 123 low-order octet or the sub-type is set to 0x04. 125 The Value Field consists of two sub-fields: 127 Global Administrator sub-field: 4 octets 129 This sub-field contains a four-octet Autonomous System number. 131 Local Administrator sub-field: 2 octets 133 This sub-field contains a value that can influence routing 134 policies. This value has semantics that are of significance for 135 the Autonomous System in the Global Administrator field. 137 3. Deployment Considerations 139 There are situations in peering where a 4-octet AS specific generic 140 extended community cannot be used. 142 A speaker with a 4-octet AS may not support 4-octet extended 143 communities; or the speaker may have a customer or peer that does not 144 support 4-octet extended communities. In all such cases, the speaker 145 may need to define an appropriate standard community value for the 146 same purpose. As an example, a peer may tag its routes with a 147 community that encodes AS_TRANS [RFC4893] as the first two octets. 149 Similarly, as per [RFC4893], a 2-octet Autonomous System number can 150 be converted into a 4-octet Autonomous System number by setting the 151 two high-order octets of the 4-octet field to zero. As a 152 consequence, at least in principle, an Autonomous System that has a 153 2-octet AS number could use either a standard community or the 154 4-octet AS specific generic extended community. This is undesirable, 155 as they would be treated as different communities, even if they had 156 the same values. 158 Therefore, for backward compatibility with existing deployments and 159 to avoid inconsistencies between standard communities and 4-octet 160 extended communities, Autonomous Systems that use 2-octet Autonomous 161 System numbers SHOULD use standard 2-octet communities as defined in 162 RFC1997 rather than the 4-octet AS specific extended community as 163 defined in this document. 165 4. Acknowledgments 167 The authors would like to thank Paul Jakma, Bruno Decraene and Cayle 168 Spandon for their useful comments on the document. 170 5. IANA Considerations 172 This document defines a specific application of the four-octet AS 173 specific extended community. IANA is requested to to assign a sub- 174 type value of 0x04 for the generic four-octet AS specific extended 175 community. 177 This document makes the following assignments for the generic four- 178 octet AS specific extended community: 180 Name Value 181 ---- ----- 182 transitive generic four-octet AS specific 0x0204 183 non-transitive generic four-octet AS specific 0x4204 185 6. Security Considerations 187 There are no additional security risks introduced by this design. 189 7. References 191 7.1. Normative References 193 [RFC1997] Chandrasekeran, R., Traina, P., and T. Li, "BGP 194 Communities Attribute", RFC 1997, August 1996. 196 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 197 Requirement Levels", BCP 14, RFC 2119, March 1997. 199 [RFC4893] Vohra, Q. and E. Chen, "BGP Support for Four-octet AS 200 Number Space", RFC 4893, May 2007. 202 [RFC5668] Rekhter, Y., Sangli, S., and D. Tappan, "4-Octet AS 203 Specific BGP Extended Community", RFC 5668, October 2009. 205 7.2. Informative References 207 [RFC1998] Chen, E. and T. Bates, "An Application of the BGP 208 Community Attribute in Multi-home Routing", RFC 1998, 209 August 1996. 211 Authors' Addresses 213 Dhananjaya Rao 214 Cisco Systems 215 170 W. Tasman Drive 216 San Jose, CA 95134 217 USA 219 Email: dhrao@cisco.com 221 Pradosh Mohapatra 222 Sproute Networks 224 Email: mpradosh@yahoo.com 226 Jeffrey Haas 227 Juniper Networks 228 1194 North Mathilda Ave. 229 Sunnyvale, CA 94089 230 USA 232 Email: jhaas@pfrc.org