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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) == Unused Reference: 'RFC4360' is defined on line 198, but no explicit reference was found in the text == Unused Reference: 'RFC5226' is defined on line 204, but no explicit reference was found in the text ** Downref: Normative reference to an Informational RFC: RFC 1998 ** Obsolete normative reference: RFC 4893 (Obsoleted by RFC 6793) ** Obsolete normative reference: RFC 5226 (Obsoleted by RFC 8126) Summary: 4 errors (**), 0 flaws (~~), 3 warnings (==), 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 29, 2010 J. Haas 6 Arbor Networks 7 October 26, 2009 9 Generic Subtype for BGP Four-octet AS specific extended community 10 draft-ietf-idr-as4octet-extcomm-generic-subtype-01.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 April 29, 2010. 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 in effect on the date of 42 publication of this document (http://trustee.ietf.org/license-info). 43 Please review these documents carefully, as they describe your rights 44 and restrictions with respect to this document. 46 Abstract 48 Maintaining the current best practices with communities, ISPs and 49 enterprises that are assigned a 4-octet AS number may want the BGP 50 UPDATE messages they receive from their customers or peers to include 51 a 4-octet AS specific extended community. This document defines a 52 new sub-type within the four-octet AS specific extended community to 53 facilitate this practice. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3 59 2. Generic Sub-type Definition . . . . . . . . . . . . . . . . . . 3 60 3. Deployment Considerations . . . . . . . . . . . . . . . . . . . 4 61 4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5 62 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 63 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 64 7. Normative References . . . . . . . . . . . . . . . . . . . . . 5 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 [I-D.ietf-l3vpn-as4octet-ext-community] defines a format for a four- 95 octet AS specific extended community with a designated type field. 96 That document defines two sub-types: Four-octet specific Route Target 97 extended community and Four-octet specific Route Origin extended 98 community. This document specifies a generic sub-type for the four- 99 octet AS specific extended community to provide benefits such as the 100 one cited above as the 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. A speaker with a 4-octet AS may 140 not support 4-octet extended communities; or the speaker may have a 141 customer or peer that does not support 4-octet extended communities. 142 In all such cases, the speaker may need to define an appropriate 143 standard community value for the same purpose. As an example, a peer 144 may tag its routes with communities that encode AS_TRANS [RFC4893] as 145 the first two octets. 147 Similarly, a 2-octet AS number may have two valid representations as 148 either a standard community or a 4-octet extended community with the 149 upper two octets of the AS number set to zero. For backward 150 compatibility with existing deployments, and to avoid inconsistencies 151 between standard communities and 4-octet extended communities, two- 152 octet ASes SHOULD use standard 2-octet communities as defined in RFC 153 1997 rather than the 4-octet AS specific community as defined in this 154 document. 156 4. Acknowledgments 158 The authors would like to thank Paul Jakma, Bruno Decraene and Cayle 159 Spandon for their useful comments on the document. 161 5. IANA Considerations 163 This document defines a specific application of the four-octet AS 164 specific extended community. IANA is requested to to assign a sub- 165 type value of 0x04 for the generic four-octet AS specific extended 166 community. 168 This document makes the following assignments for the generic four- 169 octet AS specific extended community: 171 Name Value 172 ---- ----- 173 transitive generic four-octet AS specific 0x0204 174 non-transitive generic four-octet AS specific 0x4204 176 6. Security Considerations 178 There are no additional security risks introduced by this design. 180 7. Normative References 182 [I-D.ietf-l3vpn-as4octet-ext-community] 183 Rekhter, Y., Sangli, S., and D. Tappan, "Four-octet AS 184 Specific BGP Extended Community", 185 draft-ietf-l3vpn-as4octet-ext-community-03 (work in 186 progress), March 2009. 188 [RFC1997] Chandrasekeran, R., Traina, P., and T. Li, "BGP 189 Communities Attribute", RFC 1997, August 1996. 191 [RFC1998] Chen, E. and T. Bates, "An Application of the BGP 192 Community Attribute in Multi-home Routing", RFC 1998, 193 August 1996. 195 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 196 Requirement Levels", BCP 14, RFC 2119, March 1997. 198 [RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended 199 Communities Attribute", RFC 4360, February 2006. 201 [RFC4893] Vohra, Q. and E. Chen, "BGP Support for Four-octet AS 202 Number Space", RFC 4893, May 2007. 204 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 205 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 206 May 2008. 208 Authors' Addresses 210 Dhananjaya Rao 211 Cisco Systems 212 170 W. Tasman Drive 213 San Jose, CA 95134 214 USA 216 Email: dhrao@cisco.com 218 Pradosh Mohapatra 219 Cisco Systems 220 170 W. Tasman Drive 221 San Jose, CA 95134 222 USA 224 Email: pmohapat@cisco.com 226 Jeffrey Haas 227 Arbor Networks 228 2727 S. State St. 229 Ann Arbor, MI 48104 230 USA 232 Email: jhaas@arbor.net