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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) No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IDR J. Heitz 3 Internet-Draft Cisco 4 Intended status: Standards Track K. Sriram 5 Expires: 8 September 2022 NIST 6 B. Dickson 8 J. Heasly 9 7 March 2022 11 BGP Well Known Large Community 12 draft-heitz-idr-wklc-04 14 Abstract 16 A range of BGP Autonomous System Numbers is reserved to create a set 17 of BGP Well Known Large Communities. 19 Requirements Language 21 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 22 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 23 document are to be interpreted as described in [RFC2119]. 25 Status of This Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at https://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on 8 September 2022. 42 Copyright Notice 44 Copyright (c) 2022 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 49 license-info) in effect on the date of publication of this document. 50 Please review these documents carefully, as they describe your rights 51 and restrictions with respect to this document. Code Components 52 extracted from this document must include Revised BSD License text as 53 described in Section 4.e of the Trust Legal Provisions and are 54 provided without warranty as described in the Revised BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 59 2. Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 2 60 3. Transitivity . . . . . . . . . . . . . . . . . . . . . . . . 3 61 4. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 4 62 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 63 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 64 7. Normative References . . . . . . . . . . . . . . . . . . . . 5 65 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 67 1. Introduction 69 The Global Administrator field of the BGP Large community [RFC8092] 70 is an Autonomous System Number (ASN). To create a set of Well Known 71 Large Communities, a set of ASNs must be reserved for them, such that 72 a real ASN in the Global Administrator field cannot be mistaken for a 73 Well Known Large Community. 75 2. Encoding 77 Each BGP Well Known Large Community value is encoded as a 12-octet 78 quantity, as follows: 80 0 1 2 3 81 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 82 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 83 |1 1 1 1 0 1| T | WKLC ID | Data 1 | 84 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 85 | Data 2 | 86 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 87 | Data 3 | 88 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 90 The fields are as shown below: 92 T - Transitivity field (2 bits). This is further 93 described below. 95 WKLC ID - Well Known Large Community Identifier (1 octet). 96 See IANA Considerations. If an experimental type 97 is used, then it MUST NOT be hard coded in the BGP 98 speaker software; it MUST be configurable. 99 Different experiments can then run in the same 100 network without having to coordinate identifier 101 assignment during the coding stage. 103 Data 1,2,3 - A 10 octet value specific to the WKLC. Data 1 is 104 16 bits long and Data 2 and Data 3 are 32 bits long 105 each. The data portion is divided into the three 106 fields only to encourage a canonical representation 107 that follows [RFC8092]. If any WKLC cannot make 108 use of this data division, it is free to define 109 another division. 111 3. Transitivity 113 The Large Community path attribute is a transitive attribute. Thus, 114 BGP speakers that do not implement the transitivity described here 115 will transit the WKLC regardless. If such a speaker wishes not to 116 receive a particular large community, it MUST filter it out using 117 local policy. The transitivity field determines how BGP speakers 118 transfer the WKLC across real Autonomous System (AS) boundaries. The 119 values are: 121 0 - Transitive: The WKLC is transitive across ASes. 123 1 - Non-transitive: The WKLC is not transitive across ASes. 125 2 - Administration Transitive: The WKLC is transitive across 126 ASes under the same administration only. By default, every 127 AS boundary is also an administration boundary. If an 128 external BGP session is configured as a non-administrative 129 boundary, then it will send and receive WKLCs with 130 transitivity 2, else it will discard the WKLC from the 131 UPDATE message. 133 3 - One-time Transitive: The WKLC is transitive across ASes 134 under the same administration and into an AS under the 135 neighboring administration, but not into an AS under a 136 further administration. A BGP speaker that receives a WKLC 137 with transitivity 3 on an external BGP session on an 138 administrative boundary SHOULD change the transitivity to 2. 140 4. Discussion 142 A criterion considered important is the number of data octets 143 available for any WKLC type. This is maximized to 10 at the expense 144 of ASN space and type space. 146 8 bits for the type is considered to be plenty. 255 types are more 147 than enough for WKLC, considering how many extended community types 148 have been used so far (22 at time of this publication). If a large 149 set of types, each of which requires less than 10 octets of data, is 150 required, then they can all be specified under a single type code and 151 further distinguished by using the Data 1 field as a sub-type. An 152 equivalent example is the EVPN Extended Community type, which defines 153 further sub types. 155 The range of AS numbers currently unallocated by IANA is 399,261 to 156 4,199,999,999. The WKLC reserves 67,108,864 AS numbers. That still 157 leaves 4,132,491,874 unallocated AS numbers. For comparison, there 158 are 94,968,317 AS numbers reserved for private use. Thus, the number 159 of ASNs reserved for WKLCs is considered insignificant. 161 5. Security Considerations 163 The BGP Large Community Path attribute is transitive. Thus, a BGP 164 speaker that does not recognize the transitivity field may transmit 165 the WKLC contrary to the advisement of the transitivity field. If a 166 BGP speaker wishes not to receive any Large Community, it must 167 continue to filter it in the same way it was doing before the 168 transitivity field was introduced. 170 In some cases, a received route that contains an AS number from the 171 range assigned to WKLC in its AS_PATH may be considered unusual. A 172 receiving BGP speaker MAY drop such a received route in route-policy. 174 6. IANA Considerations 176 IANA is requested to assign the range 4093640704 (0xF4000000) to 177 4160749567 (0xF7FFFFFF) from the BGP ASN registry for BGP Well Known 178 Large Communities. 180 IANA is requested to create a registry of Well Known Large 181 Communities in the range 0 to 255. Numbers from this registry are to 182 be assigned in accordance with the policies defined in [RFC8126]. 183 The policies for the following number ranges are: 185 0-63 - RFC Required 187 64-223 - First Come First Served 188 224-255 - Experimental 190 7. Normative References 192 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 193 Requirement Levels", BCP 14, RFC 2119, 194 DOI 10.17487/RFC2119, March 1997, 195 . 197 [RFC8092] Heitz, J., Ed., Snijders, J., Ed., Patel, K., Bagdonas, 198 I., and N. Hilliard, "BGP Large Communities Attribute", 199 RFC 8092, DOI 10.17487/RFC8092, February 2017, 200 . 202 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 203 Writing an IANA Considerations Section in RFCs", BCP 26, 204 RFC 8126, DOI 10.17487/RFC8126, June 2017, 205 . 207 Authors' Addresses 209 Jakob Heitz 210 Cisco 211 170 West Tasman Drive 212 San Jose, CA 95134 213 United States of America 214 Email: jheitz@cisco.com 216 Kotikalapudi Sriram 217 USA National Institute of Standards and Technology 218 100 Bureau Drive 219 Gaithersburg, MD 20899 220 United States of America 221 Email: kotikalapudi.sriram@nist.gov 223 Brian Dickson 224 Email: brian.peter.dickson@gmail.com 226 John Heasly 227 Email: heas@shrubbery.net