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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 7752 (Obsoleted by RFC 9552) Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 LSR Working Group A. Wang 3 Internet-Draft China Telecom 4 Intended status: Standards Track A. Lindem 5 Expires: April 23, 2021 Cisco Systems 6 J. Dong 7 Huawei Technologies 8 P. Psenak 9 K. Talaulikar 10 Cisco Systems 11 October 20, 2020 13 OSPF Prefix Originator Extensions 14 draft-ietf-lsr-ospf-prefix-originator-07 16 Abstract 18 This document defines OSPF extensions to include information 19 associated with the node originating a prefix along with the prefix 20 advertisement. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at https://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on April 23, 2021. 39 Copyright Notice 41 Copyright (c) 2020 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (https://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 58 2. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 3 59 2.1. Prefix Source Router-ID Sub-TLV . . . . . . . . . . . . . 3 60 2.2. Prefix Originator Sub-TLV . . . . . . . . . . . . . . . . 4 61 3. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 5 62 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6 63 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 64 6. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 7 65 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 66 7.1. Normative References . . . . . . . . . . . . . . . . . . 7 67 7.2. Informative References . . . . . . . . . . . . . . . . . 8 68 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 70 1. Introduction 72 Prefix attributes are advertised in OSPFv2 [RFC2328] using the 73 Extended Prefix Opaque Link State Advertisement (LSA) [RFC7684] and 74 in OSPFv3 [RFC5340] using the various Extended Prefix LSA types 75 [RFC8362]. 77 The identification of the originating router for a prefix in OSPF 78 varies by the type of the prefix and is currently not always 79 possible. For intra-area prefixes, the originating router is 80 identified by the advertising Router ID field of the area-scoped LSA 81 used for those prefix advertisements. However, for the inter-area 82 prefixes advertised by the Area Border Router (ABR), the advertising 83 Router ID field of their area-scoped LSAs is set to the ABR itself 84 and the information about the router originating the prefix 85 advertisement is lost in this process of prefix propagation across 86 areas. For Autonomous System (AS) external prefixes, the originating 87 router may be considered as the Autonomous System Border Router 88 (ASBR) and is identified by the advertising Router ID field of the 89 AS-scoped LSA used. However, the actual originating router for the 90 prefix may be a remote router outside the OSPF domain. Similarly, 91 when an ABR performs translation of Not-So-Stubby Area (NSSA) 92 [RFC3101] LSAs to AS-external LSAs, the information associated with 93 the NSSA ASBR (or the router outside the OSPF domain) is not conveyed 94 across the OSPF domain. 96 While typically the originator of information in OSPF is identified 97 by its OSPF Router ID, it does not necessarily represent a reachable 98 address for the router. The IPv4/IPv6 Router Address as defined in 99 [RFC3630] and [RFC5329] for OSPFv2 and OSPFv3 respectively provide an 100 address to reach that router. 102 The primary use case for the extensions proposed in this document is 103 to be able to identify the originator of the prefix in the network. 104 In cases where multiple prefixes are advertised by a given router, it 105 is also useful to be able to associate all these prefixes with a 106 single router even when prefixes are advertised outside of the area 107 in which they originated. It also helps to determine when the same 108 prefix is being originated by multiple routers across areas. 110 This document proposes extensions to the OSPF protocol for inclusion 111 of information associated with the router originating the prefix 112 along with the prefix advertisement. These extensions do not change 113 the core OSPF route computation functionality. They provide useful 114 information for topology analysis and traffic engineering, especially 115 on a controller when this information is advertised as an attribute 116 of the prefixes via mechanisms such as Border Gateway Protocol Link- 117 State (BGP-LS) [RFC7752]. 119 1.1. Requirements Language 121 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 122 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 123 "OPTIONAL" in this document are to be interpreted as described in BCP 124 14 [RFC2119] [RFC8174] when, and only when, they appear in all 125 capitals, as shown here. 127 2. Protocol Extensions 129 This document defines the Prefix Source Router-ID and the Prefix 130 Originator Sub-TLVs for inclusion of the Router ID and a reachable 131 address information for the router originating the prefix as a prefix 132 attribute. 134 2.1. Prefix Source Router-ID Sub-TLV 136 For OSPFv2, the Prefix Source Router-ID Sub-TLV is an optional Sub- 137 TLV of the OSPFv2 Extended Prefix TLV [RFC7684]. For OSPFv3, the 138 Prefix Source Router-ID Sub-TLV is an optional Sub-TLV of the Intra- 139 Area-Prefix TLV, Inter-Area-Prefix TLV, and External-Prefix TLV 140 [RFC8362] when originating either an IPv4 [RFC5838] or an IPv6 prefix 141 advertisement. 143 The Prefix Source Router-ID Sub-TLV has the following format: 145 0 1 2 3 146 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 1 147 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 148 | Type | Length | 149 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 150 | OSPF Router ID | 151 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 153 Figure 1: Prefix Source Router-ID Sub-TLV Format 155 Where: 157 o Type: 4 for OSPFv2 and 27 for OSPFv3 159 o Length: 4 161 o OSPF Router ID : the OSPF Router ID of the OSPF router that 162 originated the prefix advertisement in the OSPF domain. 164 A prefix advertisement MAY include more than one Prefix Source 165 Router-ID sub-TLV, one corresponding to each of the Equal-Cost Multi- 166 Path (ECMP) nodes that originated the given prefix. 168 A received Prefix Source Router-ID Sub-TLV with OSPF Router ID set to 169 0 MUST be considered invalid and ignored. Additionally, reception of 170 such Sub-TLV SHOULD be logged as an error (subject to rate-limiting). 172 2.2. Prefix Originator Sub-TLV 174 For OSPFv2, the Prefix Originator Sub-TLV is an optional Sub-TLV of 175 the OSPFv2 Extended Prefix TLV [RFC7684]. For OSPFv3, the Prefix 176 Originator Sub-TLV is an optional Sub-TLV of the Intra-Area-Prefix 177 TLV, Inter-Area-Prefix TLV, and External-Prefix TLV [RFC8362] when 178 originating either an IPv4 [RFC5838] or an IPv6 prefix advertisement. 180 The Prefix Originator Sub-TLV has the following format: 182 0 1 2 3 183 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 1 184 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 185 | Type | Length | 186 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 187 | Router Address (4 or 16 octets) | 188 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 190 Figure 2: Prefix Originator Sub-TLV Format 192 Where: 194 o Type: TBD1 for OSPFv2 and TBD2 for OSPFv3 196 o Length: 4 or 16 198 o Router Address: A reachable IPv4 or IPv6 router address for the 199 router that originated the IPv4 or IPv6 prefix advertisement. 200 Such an address would be semantically equivalent to what may be 201 advertised in the OSPFv2 Router Address TLV [RFC3630] or in the 202 OSPFv3 Router IPv6 Address TLV [RFC5329]. 204 A prefix advertisement MAY include more than one Prefix Originator 205 sub-TLV, one corresponding to each of the Equal-Cost Multi-Path 206 (ECMP) nodes that originated the given prefix. 208 A received Prefix Originator Sub-TLV that has an invalid length (not 209 4 or 16) or a Router Address containing an invalid IPv4 or IPv6 210 address (dependent on address family of the associated prefix) MUST 211 be considered invalid and ignored. Additionally, reception of such 212 Sub-TLV SHOULD be logged as an error (subject to rate-limiting). 214 [RFC7794] provides similar functionality for the Intermediate System 215 to Intermediate System (IS-IS) protocol. 217 3. Elements of Procedure 219 This section describes the procedure for advertisement of the Prefix 220 Source Router-ID and Prefix Originator Sub-TLVs along with the prefix 221 advertisement. 223 The OSPF Router ID of the Prefix Source Router-ID is set to the OSPF 224 Router ID of the node originating the prefix in the OSPF domain. 226 If the originating node is advertising an OSPFv2 Router Address TLV 227 [RFC3630] or an OSPFv3 Router IPv6 Address TLV [RFC5329], then that 228 value is set in the Router Address field of the Prefix Originator 229 Sub-TLV. When the originating node is not advertising such an 230 address, implementations MAY support mechanisms to determine a 231 reachable address (e.g., advertised with the N-flag set [RFC7684] or 232 N-bit set [RFC8362] and either matching the OSPF Router ID or the 233 highest IP address) belonging to the originating node to set in the 234 Router Address field. 236 Implementations MAY support the selection of specific prefixes for 237 which the originating node information needs to be included with 238 their prefix advertisements. 240 When an ABR generates inter-area prefix advertisements into its non- 241 backbone areas corresponding to an inter-area prefix advertisement 242 from the backbone area, the only way to determine the originating 243 node information is based on the Prefix Source Router-ID and Prefix 244 Originator Sub-TLVs present in the inter-area prefix advertisement 245 originated into the backbone area by an ABR for another non-backbone 246 area. The ABR performs its prefix calculation to determine the set 247 of nodes that contribute to the best prefix reachability. It MUST 248 use the prefix originator information only from this set of nodes. 249 The ABR MUST NOT include the Prefix Source Router-ID or the Prefix 250 Originator Sub-TLVs when it is unable to determine the information of 251 the best originating node. 253 Implementations MAY provide control on ABRs to selectively disable 254 the propagation of the originating node information across area 255 boundaries. 257 Implementations MAY support the propagation of the originating node 258 information along with a redistributed prefix into the OSPF domain 259 from another routing domain. The details of such mechanisms are 260 outside the scope of this document. Such implementations MAY also 261 provide control on whether the Router Address in the Prefix 262 Originator Sub-TLV is set as the ABSR node address or as the address 263 of the actual node outside the OSPF domain that owns the prefix. 265 When translating the NSSA prefix advertisements [RFC3101] to the AS 266 external prefix advertisements, the NSSA ABR, follows the same 267 procedures as an ABR generating inter-area prefix advertisements for 268 the propagation of the originating node information. 270 4. Security Considerations 272 Since this document extends the OSPFv2 Extended Prefix LSA, the 273 security considerations for [RFC7684] are applicable. Similarly, 274 since this document extends the OSPFv3 E-Intra-Area-Prefix-LSA, E- 275 Inter-Area-Prefix-LSA, E-AS-External LSA and E-NSSA-LSA, the security 276 considerations for [RFC8362] are applicable. 278 5. IANA Considerations 280 This document requests IANA for the allocation of the codepoint from 281 the "OSPFv2 Extended Prefix TLV Sub-TLVs" registry under the "Open 282 Shortest Path First v2 (OSPFv2) Parameters" registry. 284 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 285 | Code | Description | IANA Allocation | 286 | Point | | Status | 287 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 288 | 4 | Prefix Source Router-ID Sub-TLV | early allocation done | 289 | TBD1 | Prefix Originator Sub-TLV | pending | 290 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 292 Figure 3: Code Points in OSPFv2 Extended Prefix TLV Sub-TLVs 294 This document requests IANA for the allocation of the codepoint from 295 the "OSPFv3 Extended Prefix TLV Sub-TLVs" registry under the "Open 296 Shortest Path First v3 (OSPFv3) Parameters" registry. 298 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 299 | Code | Description | IANA Allocation | 300 | Point | | Status | 301 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 302 | 27 | Prefix Source Router-ID Sub-TLV | early allocation done | 303 | TBD2 | Prefix Originator Sub-TLV | pending | 304 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 306 Figure 4: Code Points in OSPFv3 Extended-LSA Sub-TLVs 308 6. Acknowledgement 310 Many thanks to Les Ginsberg for his suggestions on this draft. Also 311 thanks to Jeff Tantsura, Rob Shakir, Gunter Van De Velde, Goethals 312 Dirk, Smita Selot, Shaofu Peng, John E Drake and Baalajee S for their 313 review and valuable comments. 315 7. References 317 7.1. Normative References 319 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 320 Requirement Levels", BCP 14, RFC 2119, 321 DOI 10.17487/RFC2119, March 1997, 322 . 324 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 325 DOI 10.17487/RFC2328, April 1998, 326 . 328 [RFC3101] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option", 329 RFC 3101, DOI 10.17487/RFC3101, January 2003, 330 . 332 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 333 for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, 334 . 336 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 337 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 338 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 339 2015, . 341 [RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and 342 U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4 343 and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794, 344 March 2016, . 346 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 347 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 348 May 2017, . 350 [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and 351 F. Baker, "OSPFv3 Link State Advertisement (LSA) 352 Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 353 2018, . 355 7.2. Informative References 357 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 358 (TE) Extensions to OSPF Version 2", RFC 3630, 359 DOI 10.17487/RFC3630, September 2003, 360 . 362 [RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed., 363 "Traffic Engineering Extensions to OSPF Version 3", 364 RFC 5329, DOI 10.17487/RFC5329, September 2008, 365 . 367 [RFC5838] Lindem, A., Ed., Mirtorabi, S., Roy, A., Barnes, M., and 368 R. Aggarwal, "Support of Address Families in OSPFv3", 369 RFC 5838, DOI 10.17487/RFC5838, April 2010, 370 . 372 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 373 S. Ray, "North-Bound Distribution of Link-State and 374 Traffic Engineering (TE) Information Using BGP", RFC 7752, 375 DOI 10.17487/RFC7752, March 2016, 376 . 378 Authors' Addresses 380 Aijun Wang 381 China Telecom 382 Beiqijia Town, Changping District 383 Beijing 102209 384 China 386 Email: wangaj3@chinatelecom.cn 388 Acee Lindem 389 Cisco Systems 390 301 Midenhall Way 391 Cary, NC 27513 392 USA 394 Email: acee@cisco.com 396 Jie Dong 397 Huawei Technologies 398 Beijing 399 China 401 Email: jie.dong@huawei.com 403 Peter Psenak 404 Cisco Systems 405 Pribinova Street 10 406 Bratislava, Eurovea Centre, Central 3 81109 407 Slovakia 409 Email: ppsenak@cisco.com 411 Ketan Talaulikar 412 Cisco Systems 413 India 415 Email: ketant@cisco.com