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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: July 30, 2009 J. Haas 6 Arbor Networks 7 January 26, 2009 9 Generic Subtype for BGP Four-octet AS specific extended community 10 draft-ietf-idr-as4octet-extcomm-generic-subtype-00.txt 12 Status of this Memo 14 This Internet-Draft is submitted to IETF in full conformance with the 15 provisions of BCP 78 and BCP 79. 17 Internet-Drafts are working documents of the Internet Engineering 18 Task Force (IETF), its areas, and its working groups. Note that 19 other groups may also distribute working documents as Internet- 20 Drafts. 22 Internet-Drafts are draft documents valid for a maximum of six months 23 and may be updated, replaced, or obsoleted by other documents at any 24 time. It is inappropriate to use Internet-Drafts as reference 25 material or to cite them other than as "work in progress." 27 The list of current Internet-Drafts can be accessed at 28 http://www.ietf.org/ietf/1id-abstracts.txt. 30 The list of Internet-Draft Shadow Directories can be accessed at 31 http://www.ietf.org/shadow.html. 33 This Internet-Draft will expire on July 30, 2009. 35 Copyright Notice 37 Copyright (c) 2009 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. 47 Abstract 49 Maintaining the current best practices with communities, ISPs and 50 enterprises that are assigned a 4-octet AS number may want the BGP 51 UPDATE messages they receive from their customers or peers to include 52 a 4-octet AS specific extended community. This document defines a 53 new sub-type within the four-octet AS specific extended community to 54 facilitate this practice. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 59 1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3 60 2. Generic Sub-type Definition . . . . . . . . . . . . . . . . . . 3 61 3. Deployment Considerations . . . . . . . . . . . . . . . . . . . 4 62 4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5 63 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 64 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 65 7. Normative References . . . . . . . . . . . . . . . . . . . . . 5 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. 86 In 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 [I-D.ietf-l3vpn-as4octet-ext-community] defines a format for a four- 96 octet AS specific extended community with a designated type field. 97 That document defines two sub-types: Four-octet specific Route Target 98 extended community and Four-octet specific Route Origin extended 99 community. This document specifies a generic sub-type for the four- 100 octet AS specific extended community to provide benefits such as the 101 one cited above as the 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). 123 The 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. A speaker with a 4-octet AS may 141 not support 4-octet extended communities; or the speaker may have a 142 customer or peer that does not support 4-octet extended communities. 143 In all such cases, the speaker may need to define an appropriate 144 standard community value for the same purpose. As an example, a peer 145 may tag its routes with communities that encode AS_TRANS [RFC4893] as 146 the first two octets. 148 Similarly, a 2-octet AS number may have two valid representations as 149 either a standard community or a 4-octet extended community with the 150 upper two octets of the AS number set to zero. For backward 151 compatibility with existing deployments, and to avoid inconsistencies 152 between standard communities and 4-octet extended communities, two- 153 octet ASes SHOULD use standard 2-octet communities as defined in RFC 154 1997 rather than the 4-octet AS specific community as defined in this 155 document. 157 4. Acknowledgments 159 The authors would like to thank Paul Jakma, Bruno Decraene and Cayle 160 Spandon for their useful comments on the document. 162 5. IANA Considerations 164 This document defines a specific application of the four-octet AS 165 specific extended community. IANA is requested to to assign a sub- 166 type value of 0x04 for the generic four-octet AS specific extended 167 community. 169 This document makes the following assignments for the generic four- 170 octet AS specific extended community: 172 Name Value 173 ---- ----- 174 transitive generic four-octet AS specific 0x0204 175 non-transitive generic four-octet AS specific 0x4204 177 6. Security Considerations 179 There are no additional security risks introduced by this design. 181 7. Normative References 183 [I-D.ietf-l3vpn-as4octet-ext-community] 184 Rekhter, Y., Sangli, S., and D. Tappan, "Four-octet AS 185 Specific BGP Extended Community", 186 draft-ietf-l3vpn-as4octet-ext-community-02 (work in 187 progress), November 2008. 189 [RFC1997] Chandrasekeran, R., Traina, P., and T. Li, "BGP 190 Communities Attribute", RFC 1997, August 1996. 192 [RFC1998] Chen, E. and T. Bates, "An Application of the BGP 193 Community Attribute in Multi-home Routing", RFC 1998, 194 August 1996. 196 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 197 Requirement Levels", BCP 14, RFC 2119, March 1997. 199 [RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended 200 Communities Attribute", RFC 4360, February 2006. 202 [RFC4893] Vohra, Q. and E. Chen, "BGP Support for Four-octet AS 203 Number Space", RFC 4893, May 2007. 205 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 206 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 207 May 2008. 209 Authors' Addresses 211 Dhananjaya Rao 212 Cisco Systems 213 170 W. Tasman Drive 214 San Jose, CA 95134 215 USA 217 Email: dhrao@cisco.com 219 Pradosh Mohapatra 220 Cisco Systems 221 170 W. Tasman Drive 222 San Jose, CA 95134 223 USA 225 Email: pmohapat@cisco.com 227 Jeffrey Haas 228 Arbor Networks 229 2727 S. State St. 230 Ann Arbor, MI 48104 231 USA 233 Email: jhaas@arbor.net