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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 informational reference (is this intentional?): RFC 8920 (Obsoleted by RFC 9492) Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Lindem, Ed. 3 Internet-Draft P. Psenak 4 Intended status: Standards Track Cisco Systems 5 Expires: 7 September 2022 6 March 2022 7 Extensions to OSPF for Advertising Prefix Administrative Tags 8 draft-ietf-lsr-ospf-admin-tags-03 10 Abstract 12 It is useful for routers in an OSPFv2 or OSPFv3 routing domain to be 13 able to associate tags with prefixes. Previously, OSPFv2 and OSPFv3 14 were relegated to a single tag for AS External and Not-So-Stubby-Area 15 (NSSA) prefixes. With the flexible encodings provided by OSPFv2 16 Prefix/Link Attribute Advertisement and OSPFv3 Extended LSAs, 17 multiple administrative tags may advertised for all types of 18 prefixes. These administrative tags can be used for many 19 applications including route redistribution policy, selective prefix 20 prioritization, selective IP Fast-ReRoute (IPFRR) prefix protection, 21 and many others. 23 The ISIS protocol supports a similar mechanism that is described in 24 RFC 5130. 26 Status of This Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at https://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on 7 September 2022. 43 Copyright Notice 45 Copyright (c) 2022 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 50 license-info) in effect on the date of publication of this document. 51 Please review these documents carefully, as they describe your rights 52 and restrictions with respect to this document. Code Components 53 extracted from this document must include Revised BSD License text as 54 described in Section 4.e of the Trust Legal Provisions and are 55 provided without warranty as described in the Revised BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 60 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 61 2. 32-Bit Administrative Tag Sub-TLV . . . . . . . . . . . . . . 3 62 3. Administrative Tag Applicability . . . . . . . . . . . . . . 4 63 4. Protocol Operation . . . . . . . . . . . . . . . . . . . . . 5 64 4.1. Equal-Cost Multipath Applicability . . . . . . . . . . . 5 65 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 66 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 67 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 68 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 69 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 70 8.2. Informative References . . . . . . . . . . . . . . . . . 7 71 Appendix A. 64-Bit Administrative Tag Sub-TLV . . . . . . . . . 8 72 Appendix B. Link Administrative Tags . . . . . . . . . . . . . . 8 73 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 75 1. Introduction 77 It is useful for routers in an OSPFv2 [RFC2328] or OSPFv3 [RFC5340] 78 routing domain to be able to associate tags with prefixes. 79 Previously, OSPFv3 and OSPFv3 were relegated to a single tag for AS 80 External and Not-So-Stubby-Area (NSSA) prefixes. With the flexible 81 encodings provided by OSPFv2 Prefix/Link Attribute Advertisement 82 ([RFC7684]) and OSPFv3 Extended LSA ([RFC8362]), multiple 83 administrative tags may be advertised for all types of prefixes. 84 These administrative tags can be used many applications including 85 (but not limited to): 87 1. Controlling which routes are redistributed into other protocols 88 for readvertisement. 90 2. Prioritizing selected prefixes for faster convergence and 91 installation in the forwarding plane. 93 3. Identifying selected prefixes for Loop-Free Alternative (LFA) 94 protection. 96 Throughout this document, OSPF is used when the text applies to both 97 OSPFv2 and OSPFv3. OSPFv2 or OSPFv3 is used when the text is 98 specific to one version of the OSPF protocol. 100 The ISIS protocol supports a similar mechanism that is described in 101 RFC 5130 [RFC5130]. 103 1.1. Requirements Language 105 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 106 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 107 "OPTIONAL" in this document are to be interpreted as described in BCP 108 14 [RFC2119] [RFC8174] when, and only when, they appear in all 109 capitals, as shown here. 111 2. 32-Bit Administrative Tag Sub-TLV 113 This document creates a new Administrative Tag Sub-TLV for OSPFv2 and 114 OSPFv3. This Sub-TLV specifies one or more 32-bit unsigned integers 115 that may be associated with an OSPF advertised prefix. The precise 116 usage of these tags is beyond the scope of this document. 118 The format of this Sub-TLV is the same as the format used by the 119 Traffic Engineering Extensions to OSPF [RFC3630]. The LSA payload 120 consists of one or more nested Type/Length/Value (TLV) triplets. The 121 format of each TLV is: 123 0 1 2 3 124 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 1 125 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 126 | Type | Length | 127 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 128 | Value... | 129 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 131 Figure 1: TLV Format 133 The Length field defines the length of the value portion in octets 134 (thus a TLV with no value portion would have a length of 0). The TLV 135 is padded to 4-octet alignment; padding is not included in the length 136 field (so a 3-octet value would have a length of 3, but the total 137 size of the TLV would be 8 octets). 139 The format of the 32-bit Administrative Tag TLV is as follows: 141 0 1 2 3 142 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 1 143 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 144 | Type | Length | 145 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 146 | First 32-bit Administrative Tag | 147 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 148 | o | 149 o 150 | o | 151 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 152 | Last 32-bit Administrative Tag | 153 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 155 Type A 16-bit field set to TBD. The value MAY be different 156 depending upon the IANA registry from which it is 157 allocated. 159 Length A 16-bit field that indicates the length of the value 160 portion in octets and will be a multiple of 4 octets 161 dependent on the number of administrative tags 162 advertised. If the sub-TLV is specified, at least one 163 administrative tag must be advertised. 165 Value A variable length list of one or more administrative 166 tags. 168 Figure 2: 32-bit Administrative Tag Sub-TLV 170 This sub-TLV will carry one or more 32-bit unsigned integer values 171 that will be used as administrative tags. 173 3. Administrative Tag Applicability 175 The administrative tag TLV specified herein will be valid as a sub- 176 TLV of the following TLVs specified in [RFC7684]: 178 1. Extended Prefix TLV advertised in the OSPFv2 Extended Prefix LSA 180 The administrative tag TLV specified herein will be valid as a sub- 181 TLV of the following TLVs specified in [RFC8362]: 183 1. Inter-Area-Prefix TLV advertised in the E-Inter-Area-Prefix-LSA 185 2. Intra-Area-Prefix TLV advertised in the E-Link-LSA and the E- 186 Intra-Area-Prefix-LSA 188 3. External-Prefix TLV advertised in the E-AS-External-LSA and the 189 E-NSSA-LSA 191 4. Protocol Operation 193 An OSPF router supporting this specification MUST propagate 194 administrative tags when acting as an Area Border Router and 195 originating summary advertisements into other areas. Similarly, an 196 OSPF router supporting this specification and acting as an ABR for a 197 Not-So-Stubby Area (NSSA) MUST propagate tags when translating NSSA 198 routes to AS External advertisements [RFC3101]. The number of tags 199 supported MAY limit the number of tags that are propagated. When 200 propagating multiple tags, the order of the the tags must be 201 preserved. 203 For configured area ranges, NSSA ranges, and configurated 204 summarization of redistributed routes, tags from component routes 205 SHOULD NOT be propagated to the summary. Implementations SHOULD 206 provide a mechanism to configure tags for area ranges, NSSA ranges, 207 and redistributed route summaries. 209 An OSPF router supporting this specification MUST be able to 210 advertise and interpret one 32-bit tag for prefixes. An OSPF router 211 supporting this specification MAY be able to advertise and propagate 212 multiple 32-bit tags. The maximum tags that an implementation 213 supports is a local matter depending upon supported applications 214 using the prefix or link tags. 216 When a single tag is advertised for AS External or NSSA LSA prefix, 217 the existing tag in OSPFv2 and OSPFv3 AS-External-LSA and NSSA-LSA 218 encodings SHOULD be utilized. This will facilitate backward 219 compatibilty with implementations that do not support this 220 specification. 222 4.1. Equal-Cost Multipath Applicability 224 When multiple LSAs contribute to an OSPF route, it is possible that 225 these LSAs will all have different tags. In this situation, the OSPF 226 router MUST associate the tags from one of the LSAs contributing a 227 path and, if the implementation supports multiple tags, MAY associate 228 tags for multiple contributing LSAs up to the maximum number of tags 229 supported. 231 5. Security Considerations 233 This document describes a generic mechanism for advertising 234 administrative tags for OSPF prefixes. The administrative tags are 235 generally less critical than the topology information currently 236 advertised by the base OSPF protocol. The security considerations 237 for the generic mechanism are dependent on their application. One 238 such application is to control leaking of OSPF routes to other 239 protocols (e.g., BGP [RFC4271]). If an attacker were able to modify 240 the admin tags associated with OSPF routes and they were be used for 241 this application, such routes could be prevented from being 242 advertised in routing domains where they are required (subtle denial 243 or service) or they could be advertised into routing domains where 244 they shouldn't be advertised (routing vulnerability). Security 245 considerations for the base OSPF protocol are covered in [RFC2328] 246 and [RFC5340]. 248 6. IANA Considerations 250 The following values should be allocated from the OSPF Extended 251 Prefix TLV Sub-TLV Registry [RFC7684]: 253 * TBD - 32-bit Administrative Tag TLV 255 The following values should be allocated from the OSPFv3 Extended-LSA 256 Sub-TLV Registry [RFC8362]: 258 * TBD - 32-bit Administrative Tag TLV 260 7. Acknowledgments 262 The authors of RFC 5130 are acknowledged since this document draws 263 upon both the ISIS specification and deployment experience. 265 Thanks to Donnie Savage for his comments and questions. 267 The RFC text was produced using Marshall Rose's xml2rfc tool. 269 8. References 271 8.1. Normative References 273 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 274 Requirement Levels", BCP 14, RFC 2119, 275 DOI 10.17487/RFC2119, March 1997, 276 . 278 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 279 DOI 10.17487/RFC2328, April 1998, 280 . 282 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 283 (TE) Extensions to OSPF Version 2", RFC 3630, 284 DOI 10.17487/RFC3630, September 2003, 285 . 287 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 288 for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, 289 . 291 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 292 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 293 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 294 2015, . 296 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 297 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 298 May 2017, . 300 [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and 301 F. Baker, "OSPFv3 Link State Advertisement (LSA) 302 Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 303 2018, . 305 8.2. Informative References 307 [RFC3101] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option", 308 RFC 3101, DOI 10.17487/RFC3101, January 2003, 309 . 311 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 312 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 313 DOI 10.17487/RFC4271, January 2006, 314 . 316 [RFC5130] Previdi, S., Shand, M., Ed., and C. Martin, "A Policy 317 Control Mechanism in IS-IS Using Administrative Tags", 318 RFC 5130, DOI 10.17487/RFC5130, February 2008, 319 . 321 [RFC8920] Psenak, P., Ed., Ginsberg, L., Henderickx, W., Tantsura, 322 J., and J. Drake, "OSPF Application-Specific Link 323 Attributes", RFC 8920, DOI 10.17487/RFC8920, October 2020, 324 . 326 Appendix A. 64-Bit Administrative Tag Sub-TLV 328 The definition of the 64-bit tag was considered but discard given 329 that there is no strong requirement or use case. The specification 330 is included here for information. 332 This sub-TLV will carry one or more 64-bit unsigned integer values 333 that will be used as administrative tags. 335 The format of the 64-bit Administrative Tag TLV is as follows: 337 0 1 2 3 338 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 1 339 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 340 | Type | Length | 341 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 342 | First 64-bit Administrative Tag | 343 | | 344 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 345 | O | 346 o 347 | o | 348 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 349 | Last 64-bit Administrative Tag | 350 | | 351 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 353 Type A 16-bit field set to TBD. The value MAY be different 354 depending upon the registry from which it is allocated. 356 Length A 16-bit field that indicates the length of the value 357 portion in octets and will be a multiple of 8 octets 358 dependent on the number of administrative tags 359 advertised. If the sub-TLV is specified, at least one 360 administrative tag must be advertised. 362 Value A variable length list of one or more 64-bit 363 administrative tags. 365 Figure 3: 64-bit Administrative Tag TLV 367 Appendix B. Link Administrative Tags 369 The advertisement of administrative tags corresponding to links has 370 been removed from the document. The specification of advertising 371 link administrative groups as specified in [RFC8920] advertising 372 administrative tags for links. 374 Authors' Addresses 376 Acee Lindem (editor) 377 Cisco Systems 378 301 Midenhall Way 379 Cary, NC 27513 380 United States of America 381 Email: acee@cisco.com 383 Peter Psenak 384 Cisco Systems 385 Apollo Business Center 386 Mlynske nivy 43 387 Bratislava 388 Slovakia 389 Email: ppsenak@cisco.com