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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: March 17, 2022 September 13, 2021 7 Extensions to OSPF for Advertising Prefix Administrative Tags 8 draft-ietf-lsr-ospf-admin-tags-02 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 March 17, 2022. 43 Copyright Notice 45 Copyright (c) 2021 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 50 (https://trustee.ietf.org/license-info) in effect on the date of 51 publication of this document. Please review these documents 52 carefully, as they describe your rights and restrictions with respect 53 to this document. Code Components extracted from this document must 54 include Simplified BSD License text as described in Section 4.e of 55 the Trust Legal Provisions and are provided without warranty as 56 described in the Simplified BSD License. 58 Table of Contents 60 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 61 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 62 2. 32-Bit Administrative Tag Sub-TLV . . . . . . . . . . . . . . 3 63 3. Administrative Tag Applicability . . . . . . . . . . . . . . 4 64 4. Protocol Operation . . . . . . . . . . . . . . . . . . . . . 5 65 4.1. Equal-Cost Multipath Applicability . . . . . . . . . . . 5 66 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 67 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 68 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 69 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 70 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 71 8.2. Informative References . . . . . . . . . . . . . . . . . 7 72 Appendix A. 64-Bit Administrative Tag Sub-TLV . . . . . . . . . 8 73 Appendix B. Link Administrative Tags . . . . . . . . . . . . . . 8 74 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 76 1. Introduction 78 It is useful for routers in an OSPFv2 [RFC2328] or OSPFv3 [RFC5340] 79 routing domain to be able to associate tags with prefixes. 80 Previously, OSPFv3 and OSPFv3 were relegated to a single tag for AS 81 External and Not-So-Stubby-Area (NSSA) prefixes. With the flexible 82 encodings provided by OSPFv2 Prefix/Link Attribute Advertisement 83 ([RFC7684]) and OSPFv3 Extended LSA ([RFC8362]), multiple 84 administrative tags may be advertised for all types of prefixes. 85 These administrative tags can be used many applications including 86 (but not limited to): 88 1. Controlling which routes are redistributed into other protocols 89 for readvertisement. 91 2. Prioritizing selected prefixes for faster convergence and 92 installation in the forwarding plane. 94 3. Identifying selected prefixes for Loop-Free Alternative (LFA) 95 protection. 97 Throughout this document, OSPF is used when the text applies to both 98 OSPFv2 and OSPFv3. OSPFv2 or OSPFv3 is used when the text is 99 specific to one version of the OSPF protocol. 101 The ISIS protocol supports a similar mechanism that is described in 102 RFC 5130 [RFC5130]. 104 1.1. Requirements Language 106 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 107 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 108 "OPTIONAL" in this document are to be interpreted as described in BCP 109 14 [RFC2119] [RFC8174] when, and only when, they appear in all 110 capitals, as shown here. 112 2. 32-Bit Administrative Tag Sub-TLV 114 This document creates a new Administrative Tag Sub-TLV for OSPFv2 and 115 OSPFv3. This Sub-TLV specifies one or more 32-bit unsigned integers 116 that may be associated with an OSPF advertised prefix. The precise 117 usage of these tags is beyond the scope of this document. 119 The format of this Sub-TLV is the same as the format used by the 120 Traffic Engineering Extensions to OSPF [RFC3630]. The LSA payload 121 consists of one or more nested Type/Length/Value (TLV) triplets. The 122 format of each TLV is: 124 0 1 2 3 125 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 1 126 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 127 | Type | Length | 128 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 129 | Value... | 130 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 132 TLV Format 134 The Length field defines the length of the value portion in octets 135 (thus a TLV with no value portion would have a length of 0). The TLV 136 is padded to 4-octet alignment; padding is not included in the length 137 field (so a 3-octet value would have a length of 3, but the total 138 size of the TLV would be 8 octets). 140 The format of the 32-bit Administrative Tag TLV is as follows: 142 0 1 2 3 143 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 1 144 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 145 | Type | Length | 146 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 147 | First 32-bit Administrative Tag | 148 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 149 | o | 150 o 151 | o | 152 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 153 | Last 32-bit Administrative Tag | 154 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 156 Type A 16-bit field set to TBD. The value MAY be different 157 depending upon the IANA registry from which it is 158 allocated. 160 Length A 16-bit field that indicates the length of the value 161 portion in octets and will be a multiple of 4 octets 162 dependent on the number of administrative tags 163 advertised. If the sub-TLV is specified, at least one 164 administrative tag must be advertised. 166 Value A variable length list of one or more administrative 167 tags. 169 32-bit Administrative Tag Sub-TLV 171 This sub-TLV will carry one or more 32-bit unsigned integer values 172 that will be used as administrative tags. 174 3. Administrative Tag Applicability 176 The administrative tag TLV specified herein will be valid as a sub- 177 TLV of the following TLVs specified in [RFC7684]: 179 1. Extended Prefix TLV advertised in the OSPFv2 Extended Prefix LSA 181 The administrative tag TLV specified herein will be valid as a sub- 182 TLV of the following TLVs specified in [RFC8362]: 184 1. Inter-Area-Prefix TLV advertised in the E-Inter-Area-Prefix-LSA 186 2. Intra-Area-Prefix TLV advertised in the E-Link-LSA and the E- 187 Intra-Area-Prefix-LSA 189 3. External-Prefix TLV advertised in the E-AS-External-LSA and the 190 E-NSSA-LSA 192 4. Protocol Operation 194 An OSPF router supporting this specification MUST propagate 195 administrative tags when acting as an Area Border Router and 196 originating summary advertisements into other areas. Similarly, an 197 OSPF router supporting this specification and acting as an ABR for a 198 Not-So-Stubby Area (NSSA) MUST propagate tags when translating NSSA 199 routes to AS External advertisements [RFC3101]. The number of tags 200 supported MAY limit the number of tags that are propagated. When 201 propagating multiple tags, the order of the the tags must be 202 preserved. 204 For configured area ranges, NSSA ranges, and configurated 205 summarization of redistributed routes, tags from component routes 206 SHOULD NOT be propagated to the summary. Implementations SHOULD 207 provide a mechanism to configure tags for area ranges, NSSA ranges, 208 and redistributed route summaries. 210 An OSPF router supporting this specification MUST be able to 211 advertise and interpret one 32-bit tag for prefixes. An OSPF router 212 supporting this specification MAY be able to advertise and propagate 213 multiple 32-bit tags. The maximum tags that an implementation 214 supports is a local matter depending upon supported applications 215 using the prefix or link tags. 217 When a single tag is advertised for AS External or NSSA LSA prefix, 218 the existing tag in OSPFv2 and OSPFv3 AS-External-LSA and NSSA-LSA 219 encodings SHOULD be utilized. This will facilitate backward 220 compatibilty with implementations that do not support this 221 specification. 223 4.1. Equal-Cost Multipath Applicability 225 When multiple LSAs contribute to an OSPF route, it is possible that 226 these LSAs will all have different tags. In this situation, the OSPF 227 router MUST associate the tags from one of the LSAs contributing a 228 path and, if the implementation supports multiple tags, MAY associate 229 tags for multiple contributing LSAs up to the maximum number of tags 230 supported. 232 5. Security Considerations 234 This document describes a generic mechanism for advertising 235 administrative tags for OSPF prefixes. The administrative tags are 236 generally less critical than the topology information currently 237 advertised by the base OSPF protocol. The security considerations 238 for the generic mechanism are dependent on their application. One 239 such application is to control leaking of OSPF routes to other 240 protocols (e.g., BGP [RFC4271]). If an attacker were able to modify 241 the admin tags associated with OSPF routes and they were be used for 242 this application, such routes could be prevented from being 243 advertised in routing domains where they are required (subtle denial 244 or service) or they could be advertised into routing domains where 245 they shouldn't be advertised (routing vulnerability). Security 246 considerations for the base OSPF protocol are covered in [RFC2328] 247 and [RFC5340]. 249 6. IANA Considerations 251 The following values should be allocated from the OSPF Extended 252 Prefix TLV Sub-TLV Registry [RFC7684]: 254 o TBD - 32-bit Administrative Tag TLV 256 The following values should be allocated from the OSPFv3 Extended-LSA 257 Sub-TLV Registry [RFC8362]: 259 o TBD - 32-bit Administrative Tag TLV 261 7. Acknowledgments 263 The authors of RFC 5130 are acknowledged since this document draws 264 upon both the ISIS specification and deployment experience. 266 Thanks to Donnie Savage for his comments and questions. 268 The RFC text was produced using Marshall Rose's xml2rfc tool. 270 8. References 272 8.1. Normative References 274 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 275 Requirement Levels", BCP 14, RFC 2119, 276 DOI 10.17487/RFC2119, March 1997, 277 . 279 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 280 DOI 10.17487/RFC2328, April 1998, 281 . 283 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 284 (TE) Extensions to OSPF Version 2", RFC 3630, 285 DOI 10.17487/RFC3630, September 2003, 286 . 288 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 289 for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, 290 . 292 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 293 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 294 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 295 2015, . 297 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 298 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 299 May 2017, . 301 [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and 302 F. Baker, "OSPFv3 Link State Advertisement (LSA) 303 Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 304 2018, . 306 8.2. Informative References 308 [RFC3101] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option", 309 RFC 3101, DOI 10.17487/RFC3101, January 2003, 310 . 312 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 313 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 314 DOI 10.17487/RFC4271, January 2006, 315 . 317 [RFC5130] Previdi, S., Shand, M., Ed., and C. Martin, "A Policy 318 Control Mechanism in IS-IS Using Administrative Tags", 319 RFC 5130, DOI 10.17487/RFC5130, February 2008, 320 . 322 [RFC8920] Psenak, P., Ed., Ginsberg, L., Henderickx, W., Tantsura, 323 J., and J. Drake, "OSPF Application-Specific Link 324 Attributes", RFC 8920, DOI 10.17487/RFC8920, October 2020, 325 . 327 Appendix A. 64-Bit Administrative Tag Sub-TLV 329 The definition of the 64-bit tag was considered but discard given 330 that there is no strong requirement or use case. The specification 331 is included here for information. 333 This sub-TLV will carry one or more 64-bit unsigned integer values 334 that will be used as administrative tags. 336 The format of the 64-bit Administrative Tag TLV is as follows: 338 0 1 2 3 339 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 1 340 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 341 | Type | Length | 342 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 343 | First 64-bit Administrative Tag | 344 | | 345 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 346 | O | 347 o 348 | o | 349 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 350 | Last 64-bit Administrative Tag | 351 | | 352 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 354 Type A 16-bit field set to TBD. The value MAY be different 355 depending upon the registry from which it is allocated. 357 Length A 16-bit field that indicates the length of the value 358 portion in octets and will be a multiple of 8 octets 359 dependent on the number of administrative tags 360 advertised. If the sub-TLV is specified, at least one 361 administrative tag must be advertised. 363 Value A variable length list of one or more 64-bit 364 administrative tags. 366 64-bit Administrative Tag TLV 368 Appendix B. Link Administrative Tags 370 The advertisement of administrative tags corresponding to links has 371 been removed from the document. The specification of advertising 372 link administrative groups as specified in [RFC8920] advertising 373 administrative tags for links. 375 Authors' Addresses 377 Acee Lindem (editor) 378 Cisco Systems 379 301 Midenhall Way 380 Cary, NC 27513 381 USA 383 EMail: acee@cisco.com 385 Peter Psenak 386 Cisco Systems 387 Apollo Business Center 388 Mlynske nivy 43 389 Bratislava, 821 09 390 Slovakia 392 EMail: ppsenak@cisco.com