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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 P. Mohapatra 4 Intended status: Standards Track Cisco Systems 5 Expires: April 24, 2013 J. Haas 6 Juniper Networks 7 October 21, 2012 9 Generic Subtype for BGP Four-octet AS specific extended community 10 draft-ietf-idr-as4octet-extcomm-generic-subtype-06 12 Abstract 14 Maintaining the current best practices with communities, ISPs and 15 enterprises that are assigned a 4-octet AS number may want the BGP 16 UPDATE messages they receive from their customers or peers to include 17 a 4-octet AS specific BGP extended community. This document defines 18 a new sub-type within the four-octet AS specific extended community 19 to facilitate this practice. 21 Status of this Memo 23 This Internet-Draft is submitted to IETF in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at http://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on April 24, 2013. 38 Copyright Notice 40 Copyright (c) 2012 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (http://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 56 1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3 57 2. Generic Sub-type Definition . . . . . . . . . . . . . . . . . . 3 58 3. Deployment Considerations . . . . . . . . . . . . . . . . . . . 4 59 4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5 60 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 61 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 62 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 63 7.1. Normative References . . . . . . . . . . . . . . . . . . . 5 64 7.2. Informative References . . . . . . . . . . . . . . . . . . 6 65 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 67 1. Introduction 69 Maintaining the current best practices with communities, ISPs and 70 enterprises that are assigned a 4-octet AS number may want the BGP 71 UPDATE messages they receive from their customers or peers to include 72 a 4-octet AS specific extended community. This document defines a 73 new sub-type within the four-octet AS specific extended community to 74 facilitate this practice. 76 For example, [RFC1998] describes an application of BGP community 77 attribute ([RFC1997]) to implement flexible routing policies for 78 sites multi-homed to one or multiple providers. In a two-octet AS 79 environment, the advertised routes are usually associated with a 80 community attribute that encodes the provider's AS number in the 81 first two octets of the community and a LOCAL_PREF value in the 82 second two octets of the community. The community attribute signals 83 the provider edge routers connected to the site to set the 84 corresponding LOCAL_PREF on their advertisements to the IBGP mesh. 85 In this way, customers can put into practice topologies like active- 86 backup. 88 When such a provider is assigned a four-octet AS number, the existing 89 mechanism of using communities is not sufficient since the AS portion 90 of the RFC 1997 community cannot exceed two bytes. The natural 91 alternative is to extend the same mechanism using extended 92 communities since it allows for encoding eight bytes of information. 94 [RFC5668] defines a format for a four-octet AS specific extended 95 community with a designated type field. That document defines two 96 sub-types: Four-octet specific Route Target extended community and 97 Four-octet specific Route Origin extended community. This document 98 specifies a generic sub-type for the four-octet AS specific extended 99 community to provide benefits such as the one cited above as the 100 Internet migrates to four-octet AS space. 102 1.1. Requirements Language 104 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 105 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 106 document are to be interpreted as described in RFC 2119 [RFC2119]. 108 2. Generic Sub-type Definition 109 0 1 2 3 110 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 1 111 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 112 | 0x02 or 0x42 | 0x04 | Global | 113 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 114 | Administrator | Local Administrator | 115 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 117 This is an extended type with Type Field comprising of 2 octets and 118 Value Field comprising of 6 octets. 120 The high-order octet of this extended type is set to either 0x02 (for 121 transitive communities) or 0x42 (for non-transitive communities). 122 The low-order octet or the sub-type is set to 0x04. 124 The Value Field consists of two sub-fields: 126 Global Administrator sub-field: 4 octets 128 This sub-field contains a four-octet Autonomous System number. 130 Local Administrator sub-field: 2 octets 132 This sub-field contains a value that can influence routing 133 policies. This value has semantics that are of significance for 134 the Autonomous System in the Global Administrator field. 136 3. Deployment Considerations 138 There are situations in peering where a 4-octet AS specific generic 139 extended community cannot be used. 141 A speaker with a 4-octet AS may not support 4-octet extended 142 communities; or the speaker may have a customer or peer that does not 143 support 4-octet extended communities. In all such cases, the speaker 144 may need to define an appropriate standard community value for the 145 same purpose. As an example, a peer may tag its routes with a 146 community that encodes AS_TRANS [RFC4893] as the first two octets. 148 Similarly, as per [RFC4893], a 2-octet Autonomous System number can 149 be converted into a 4-octet Autonomous System number by setting the 150 two high-order octets of the 4-octet field to zero. As a 151 consequence, at least in principle, an Autonomous System that has a 152 2-octet AS number could use either a standard community or the 153 4-octet AS specific generic extended community. This is undesirable, 154 as they would be treated as different communities, even if they had 155 the same values. 157 Therefore, for backward compatibility with existing deployments and 158 to avoid inconsistencies between standard communities and 4-octet 159 extended communities, Autonomous Systems that use 2-octet Autonomous 160 System numbers SHOULD use standard 2-octet communities as defined in 161 RFC1997 rather than the 4-octet AS specific extended community as 162 defined in this document. 164 4. Acknowledgments 166 The authors would like to thank Paul Jakma, Bruno Decraene and Cayle 167 Spandon for their useful comments on the document. 169 5. IANA Considerations 171 This document defines a specific application of the four-octet AS 172 specific extended community. IANA is requested to to assign a sub- 173 type value of 0x04 for the generic four-octet AS specific extended 174 community. 176 This document makes the following assignments for the generic four- 177 octet AS specific extended community: 179 Name Value 180 ---- ----- 181 transitive generic four-octet AS specific 0x0204 182 non-transitive generic four-octet AS specific 0x4204 184 6. Security Considerations 186 There are no additional security risks introduced by this design. 188 7. References 190 7.1. Normative References 192 [RFC1997] Chandrasekeran, R., Traina, P., and T. Li, "BGP 193 Communities Attribute", RFC 1997, August 1996. 195 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 196 Requirement Levels", BCP 14, RFC 2119, March 1997. 198 [RFC4893] Vohra, Q. and E. Chen, "BGP Support for Four-octet AS 199 Number Space", RFC 4893, May 2007. 201 [RFC5668] Rekhter, Y., Sangli, S., and D. Tappan, "4-Octet AS 202 Specific BGP Extended Community", RFC 5668, October 2009. 204 7.2. Informative References 206 [RFC1998] Chen, E. and T. Bates, "An Application of the BGP 207 Community Attribute in Multi-home Routing", RFC 1998, 208 August 1996. 210 Authors' Addresses 212 Dhananjaya Rao 213 Cisco Systems 214 170 W. Tasman Drive 215 San Jose, CA 95134 216 USA 218 Email: dhrao@cisco.com 220 Pradosh Mohapatra 221 Cisco Systems 222 170 W. Tasman Drive 223 San Jose, CA 95134 224 USA 226 Email: pmohapat@cisco.com 228 Jeffrey Haas 229 Juniper Networks 230 1194 North Mathilda Ave. 231 Sunnyvale, CA 94089 232 USA 234 Email: jhaas@pfrc.org