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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: 3 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 22, 2011 J. Haas 6 Juniper Networks 7 October 24, 2010 9 Generic Subtype for BGP Four-octet AS specific extended community 10 draft-ietf-idr-as4octet-extcomm-generic-subtype-03.txt 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 extended community. This document defines a 18 new sub-type within the four-octet AS specific extended community to 19 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 22, 2011. 38 Copyright Notice 40 Copyright (c) 2010 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. Normative References . . . . . . . . . . . . . . . . . . . . . 5 63 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 65 1. Introduction 67 Maintaining the current best practices with communities, ISPs and 68 enterprises that are assigned a 4-octet AS number may want the BGP 69 UPDATE messages they receive from their customers or peers to include 70 a 4-octet AS specific extended community. This document defines a 71 new sub-type within the four-octet AS specific extended community to 72 facilitate this practice. 74 For example, [RFC1998] describes an application of BGP community 75 attribute ([RFC1997]) to implement flexible routing policies for 76 sites multi-homed to one or multiple providers. In a two-octet AS 77 environment, the advertised routes are usually associated with a 78 community attribute that encodes the provider's AS number in the 79 first two octets of the community and a LOCAL_PREF value in the 80 second two octets of the community. The community attribute signals 81 the provider edge routers connected to the site to set the 82 corresponding LOCAL_PREF on their advertisements to the IBGP mesh. 83 In this way, customers can put into practice topologies like active- 84 backup. 86 When such a provider is assigned a four-octet AS number, the existing 87 mechanism of using communities is not sufficient since the AS portion 88 of the RFC 1997 community cannot exceed two bytes. The natural 89 alternative is to extend the same mechanism using extended 90 communities since it allows for encoding eight bytes of information. 92 [RFC5668] defines a format for a four-octet AS specific extended 93 community with a designated type field. That document defines two 94 sub-types: Four-octet specific Route Target extended community and 95 Four-octet specific Route Origin extended community. This document 96 specifies a generic sub-type for the four-octet AS specific extended 97 community to provide benefits such as the one cited above as the 98 Internet migrates to four-octet AS space. 100 1.1. Requirements Language 102 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 103 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 104 document are to be interpreted as described in RFC 2119 [RFC2119]. 106 2. Generic Sub-type Definition 107 0 1 2 3 108 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 1 109 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 110 | 0x02 or 0x42 | 0x04 | Global | 111 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 112 | Administrator | Local Administrator | 113 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 115 This is an extended type with Type Field comprising of 2 octets and 116 Value Field comprising of 6 octets. 118 The high-order octet of this extended type is set to either 0x02 (for 119 transitive communities) or 0x42 (for non-transitive communities). 120 The low-order octet or the sub-type is set to 0x04. 122 The Value Field consists of two sub-fields: 124 Global Administrator sub-field: 4 octets 126 This sub-field contains a four-octet Autonomous System number. 128 Local Administrator sub-field: 2 octets 130 This sub-field contains a value that can influence routing 131 policies. This value has semantics that are of significance for 132 the Autonomous System in the Global Administrator field. 134 3. Deployment Considerations 136 There are situations in peering where a 4-octet AS specific generic 137 extended community cannot be used. 139 A speaker with a 4-octet AS may not support 4-octet extended 140 communities; or the speaker may have a customer or peer that does not 141 support 4-octet extended communities. In all such cases, the speaker 142 may need to define an appropriate standard community value for the 143 same purpose. As an example, a peer may tag its routes with a 144 community that encodes AS_TRANS [RFC4893] as the first two octets. 146 Similarly, as per [RFC4893], a 2-octet Autonomous System number can 147 be converted into a 4-octet Autonomous System number by setting the 148 two high-order octets of the 4-octet field to zero. As a 149 consequence, at least in principle, an Autonomous System that has a 150 2-octet AS number could use either a standard community or the 151 4-octet AS specific generic extended community. This is undesirable, 152 as they would be treated as different communities, even if they had 153 the same values. 155 Therefore, for backward compatibility with existing deployments and 156 to avoid inconsistencies between standard communities and 4-octet 157 extended communities, Autonomous Systems that use 2-octet Autonomous 158 System numbers SHOULD use standard 2-octet communities as defined in 159 RFC1997 rather than the 4-octet AS specific extended community as 160 defined in this document. 162 4. Acknowledgments 164 The authors would like to thank Paul Jakma, Bruno Decraene and Cayle 165 Spandon for their useful comments on the document. 167 5. IANA Considerations 169 This document defines a specific application of the four-octet AS 170 specific extended community. IANA is requested to to assign a sub- 171 type value of 0x04 for the generic four-octet AS specific extended 172 community. 174 This document makes the following assignments for the generic four- 175 octet AS specific extended community: 177 Name Value 178 ---- ----- 179 transitive generic four-octet AS specific 0x0204 180 non-transitive generic four-octet AS specific 0x4204 182 6. Security Considerations 184 There are no additional security risks introduced by this design. 186 7. Normative References 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 [RFC5668] Rekhter, Y., Sangli, S., and D. Tappan, "4-Octet AS 209 Specific BGP Extended Community", RFC 5668, October 2009. 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 Cisco Systems 223 170 W. Tasman Drive 224 San Jose, CA 95134 225 USA 227 Email: pmohapat@cisco.com 229 Jeffrey Haas 230 Juniper Networks 231 1194 North Mathilda Ave. 232 Sunnyvale, CA 94089 233 USA 235 Email: jhaas@pfrc.org