idnits 2.17.1 draft-ietf-lsr-flex-algo-12.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year ** The document contains RFC2119-like boilerplate, but doesn't seem to mention RFC 2119. The boilerplate contains a reference [BCP14], but that reference does not seem to mention RFC 2119 either. -- The document date (October 7, 2020) is 1291 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Possible downref: Non-RFC (?) normative reference: ref. 'BCP14' == Outdated reference: A later version (-19) exists of draft-ietf-lsr-isis-srv6-extensions-10 == Outdated reference: A later version (-15) exists of draft-ietf-lsr-ospfv3-srv6-extensions-01 -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO10589' == Outdated reference: A later version (-13) exists of draft-ietf-rtgwg-segment-routing-ti-lfa-04 Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group P. Psenak, Ed. 3 Internet-Draft Cisco Systems 4 Intended status: Standards Track S. Hegde 5 Expires: April 10, 2021 Juniper Networks, Inc. 6 C. Filsfils 7 K. Talaulikar 8 Cisco Systems, Inc. 9 A. Gulko 10 Individual 11 October 7, 2020 13 IGP Flexible Algorithm 14 draft-ietf-lsr-flex-algo-12 16 Abstract 18 IGP protocols traditionally compute best paths over the network based 19 on the IGP metric assigned to the links. Many network deployments 20 use RSVP-TE based or Segment Routing based Traffic Engineering to 21 steer traffic over a path that is computed using different metrics or 22 constraints than the shortest IGP path. This document proposes a 23 solution that allows IGPs themselves to compute constraint-based 24 paths over the network. This document also specifies a way of using 25 Segment Routing (SR) Prefix-SIDs and SRv6 locators to steer packets 26 along the constraint-based paths. 28 Status of This Memo 30 This Internet-Draft is submitted in full conformance with the 31 provisions of BCP 78 and BCP 79. 33 Internet-Drafts are working documents of the Internet Engineering 34 Task Force (IETF). Note that other groups may also distribute 35 working documents as Internet-Drafts. The list of current Internet- 36 Drafts is at https://datatracker.ietf.org/drafts/current/. 38 Internet-Drafts are draft documents valid for a maximum of six months 39 and may be updated, replaced, or obsoleted by other documents at any 40 time. It is inappropriate to use Internet-Drafts as reference 41 material or to cite them other than as "work in progress." 43 This Internet-Draft will expire on April 10, 2021. 45 Copyright Notice 47 Copyright (c) 2020 IETF Trust and the persons identified as the 48 document authors. All rights reserved. 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (https://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. Code Components extracted from this document must 56 include Simplified BSD License text as described in Section 4.e of 57 the Trust Legal Provisions and are provided without warranty as 58 described in the Simplified BSD License. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 63 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4 64 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 65 4. Flexible Algorithm . . . . . . . . . . . . . . . . . . . . . 5 66 5. Flexible Algorithm Definition Advertisement . . . . . . . . . 6 67 5.1. ISIS Flexible Algorithm Definition Sub-TLV . . . . . . . 6 68 5.2. OSPF Flexible Algorithm Definition TLV . . . . . . . . . 7 69 5.3. Common Handling of Flexible Algorithm Definition TLV . . 9 70 6. Sub-TLVs of ISIS FAD Sub-TLV . . . . . . . . . . . . . . . . 10 71 6.1. ISIS Flexible Algorithm Exclude Admin Group Sub-TLV . . . 10 72 6.2. ISIS Flexible Algorithm Include-Any Admin Group Sub-TLV . 11 73 6.3. ISIS Flexible Algorithm Include-All Admin Group Sub-TLV . 12 74 6.4. ISIS Flexible Algorithm Definition Flags Sub-TLV . . . . 12 75 6.5. ISIS Flexible Algorithm Exclude SRLG Sub-TLV . . . . . . 13 76 7. Sub-TLVs of OSPF FAD TLV . . . . . . . . . . . . . . . . . . 14 77 7.1. OSPF Flexible Algorithm Exclude Admin Group Sub-TLV . . . 14 78 7.2. OSPF Flexible Algorithm Include-Any Admin Group Sub-TLV . 14 79 7.3. OSPF Flexible Algorithm Include-All Admin Group Sub-TLV . 15 80 7.4. OSPF Flexible Algorithm Definition Flags Sub-TLV . . . . 15 81 7.5. OSPF Flexible Algorithm Exclude SRLG Sub-TLV . . . . . . 16 82 8. ISIS Flexible Algorithm Prefix Metric Sub-TLV . . . . . . . . 17 83 9. OSPF Flexible Algorithm Prefix Metric Sub-TLV . . . . . . . . 18 84 10. Advertisement of Node Participation in a Flex-Algorithm . . . 19 85 10.1. Advertisement of Node Participation for Segment Routing 19 86 10.2. Advertisement of Node Participation for Other 87 Applications . . . . . . . . . . . . . . . . . . . . . . 19 88 11. Advertisement of Link Attributes for Flex-Algorithm . . . . . 20 89 12. Calculation of Flexible Algorithm Paths . . . . . . . . . . . 20 90 12.1. Multi-area and Multi-domain Considerations . . . . . . . 22 91 13. Flex-Algorithm and Forwarding Plane . . . . . . . . . . . . . 23 92 13.1. Segment Routing MPLS Forwarding for Flex-Algorithm . . . 23 93 13.2. SRv6 Forwarding for Flex-Algorithm . . . . . . . . . . . 24 94 13.3. Other Applications' Forwarding for Flex-Algorithm . . . 25 95 14. Operational considerations . . . . . . . . . . . . . . . . . 25 96 14.1. Inter-area Considerations . . . . . . . . . . . . . . . 25 97 14.2. Usage of SRLG Exclude Rule with Flex-Algorithm . . . . . 26 98 14.3. Max-metric consideration . . . . . . . . . . . . . . . . 26 99 15. Backward Compatibility . . . . . . . . . . . . . . . . . . . 27 100 16. Security Considerations . . . . . . . . . . . . . . . . . . . 27 101 17. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27 102 17.1. IGP IANA Considerations . . . . . . . . . . . . . . . . 27 103 17.1.1. IGP Algorithm Types Registry . . . . . . . . . . . . 27 104 17.1.2. IGP Metric-Type Registry . . . . . . . . . . . . . . 27 105 17.2. Flexible Algorithm Definition Flags Registry . . . . . . 28 106 17.3. ISIS IANA Considerations . . . . . . . . . . . . . . . . 28 107 17.3.1. Sub TLVs for Type 242 . . . . . . . . . . . . . . . 28 108 17.3.2. Sub TLVs for for TLVs 135, 235, 236, and 237 . . . . 29 109 17.3.3. Sub-Sub-TLVs for Flexible Algorithm Definition Sub- 110 TLV . . . . . . . . . . . . . . . . . . . . . . . . 29 111 17.4. OSPF IANA Considerations . . . . . . . . . . . . . . . . 30 112 17.4.1. OSPF Router Information (RI) TLVs Registry . . . . . 30 113 17.4.2. OSPFv2 Extended Prefix TLV Sub-TLVs . . . . . . . . 30 114 17.4.3. OSPFv3 Extended-LSA Sub-TLVs . . . . . . . . . . . . 30 115 17.4.4. OSPF Flexible Algorithm Definition TLV Sub-TLV 116 Registry . . . . . . . . . . . . . . . . . . . . . . 31 117 17.4.5. Link Attribute Applications Registry . . . . . . . . 32 118 18. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 32 119 19. References . . . . . . . . . . . . . . . . . . . . . . . . . 32 120 19.1. Normative References . . . . . . . . . . . . . . . . . . 32 121 19.2. Informative References . . . . . . . . . . . . . . . . . 34 122 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 36 124 1. Introduction 126 An IGP-computed path based on the shortest IGP metric must often be 127 replaced by a traffic-engineered path due to the traffic requirements 128 which are not reflected by the IGP metric. Some networks engineer 129 the IGP metric assignments in a way that the IGP metric reflects the 130 link bandwidth or delay. If, for example, the IGP metric is 131 reflecting the bandwidth on the link and the application traffic is 132 delay sensitive, the best IGP path may not reflect the best path from 133 such an application's perspective. 135 To overcome this limitation, various sorts of traffic engineering 136 have been deployed, including RSVP-TE and SR-TE, in which case the TE 137 component is responsible for computing paths based on additional 138 metrics and/or constraints. Such paths need to be installed in the 139 forwarding tables in addition to, or as a replacement for, the 140 original paths computed by IGPs. Tunnels are often used to represent 141 the engineered paths and mechanisms like one described in [RFC3906] 142 are used to replace the native IGP paths with such tunnel paths. 144 This document specifies a set of extensions to ISIS, OSPFv2, and 145 OSPFv3 that enable a router to advertise TLVs that identify (a) 146 calculation-type, (b) specify a metric-type, and (c) describe a set 147 of constraints on the topology, that are to be used to compute the 148 best paths along the constrained topology. A given combination of 149 calculation-type, metric-type, and constraints is known as a 150 "Flexible Algorithm Definition". A router that sends such a set of 151 TLVs also assigns a Flex-Algorithm value to the specified combination 152 of calculation-type, metric-type, and constraints. 154 This document also specifies a way for a router to use IGPs to 155 associate one or more SR Prefix-SIDs or SRv6 locators with a 156 particular Flex-Algorithm. Each such Prefix-SID or SRv6 locator then 157 represents a path that is computed according to the identified Flex- 158 Algorithm. 160 2. Requirements Language 162 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 163 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 164 "OPTIONAL" in this document are to be interpreted as described in 165 [BCP14] [RFC2119] [RFC8174] when, and only when, they appear in all 166 capitals, as shown here. 168 3. Terminology 170 This section defines terms that are often used in this document. 172 Flexible Algorithm Definition (FAD) - the set consisting of (a) 173 calculation-type, (b) metric-type, and (c) a set of constraints. 175 Flexible Algorithm - a numeric identifier in the range 128-255 that 176 is associated via configuration with the Flexible-Algorithm 177 Definition. 179 Local Flexible Algorithm Definition - Flexible Algorithm Definition 180 defined locally on the node. 182 Remote Flexible Algorithm Definition - Flexible Algorithm Definition 183 received from other nodes via IGP flooding. 185 Flexible Algorithm Participation - per application configuration 186 state that expresses whether the node is participating in a 187 particular Flexible Algorithm. 189 IGP Algorithm - value from the the "IGP Algorithm Types" registry 190 defined under "Interior Gateway Protocol (IGP) Parameters" IANA 191 registries. IGP Algorithms represents the triplet (Calculation Type, 192 Metric, Constraints), where the second and third elements of the 193 triple MAY be unspecified. 195 ABR - Area Border Router. In ISIS terminology it is also known as 196 L1/L2 router. 198 ASBR - Autonomous System Border Router. 200 4. Flexible Algorithm 202 Many possible constraints may be used to compute a path over a 203 network. Some networks are deployed as multiple planes. A simple 204 form of constraint may be to use a particular plane. A more 205 sophisticated form of constraint can include some extended metric as 206 described in [RFC8570]. Constraints which restrict paths to links 207 with specific affinities or avoid links with specific affinities are 208 also possible. Combinations of these are also possible. 210 To provide maximum flexibility, we want to provide a mechanism that 211 allows a router to (a) identify a particular calculation-type, (b) 212 metric-type, (c) describe a particular set of constraints, and (d) 213 assign a numeric identifier, referred to as Flex-Algorithm, to the 214 combination of that calculation-type, metric-type, and those 215 constraints. We want the mapping between the Flex-Algorithm and its 216 meaning to be flexible and defined by the user. As long as all 217 routers in the domain have a common understanding as to what a 218 particular Flex-Algorithm represents, the resulting routing 219 computation is consistent and traffic is not subject to any looping. 221 The set consisting of (a) calculation-type, (b) metric-type, and (c) 222 a set of constraints is referred to as a Flexible-Algorithm 223 Definition. 225 Flexible-Algorithm is a numeric identifier in the range 128-255 that 226 is associated via configuratin with the Flexible-Algorithm 227 Definition. 229 IANA "IGP Algorithm Types" registry defines the set of values for IGP 230 Algorithms. We propose to allocate the following values for Flex- 231 Algorithms from this registry: 233 128-255 - Flex-Algorithms 235 5. Flexible Algorithm Definition Advertisement 237 To guarantee the loop-free forwarding for paths computed for a 238 particular Flex-Algorithm, all routers that (a) are configured to 239 participate in a particular Flex-Algorithm, and (b) are in the same 240 Flex-Algorithm definition advertisement scope MUST agree on the 241 definition of the Flex-Algorithm. 243 5.1. ISIS Flexible Algorithm Definition Sub-TLV 245 The ISIS Flexible Algorithm Definition Sub-TLV (FAD Sub-TLV) is used 246 to advertise the definition of the Flex-Algorithm. 248 The ISIS FAD Sub-TLV is advertised as a Sub-TLV of the ISIS Router 249 Capability TLV-242 that is defined in [RFC7981]. 251 ISIS FAD Sub-TLV has the following format: 253 0 1 2 3 254 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 1 255 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 256 | Type | Length |Flex-Algorithm | Metric-Type | 257 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 258 | Calc-Type | Priority | 259 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 260 | Sub-TLVs | 261 + + 262 | ... | 264 | | 265 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 267 where: 269 Type: 26 271 Length: variable, dependent on the included Sub-TLVs 273 Flex-Algorithm: Single octet value between 128 and 255 inclusive. 275 Metric-Type: Type of metric to be used during the calculation. 276 Following values are defined: 278 0: IGP Metric 280 1: Min Unidirectional Link Delay as defined in [RFC8570], 281 section 4.2, encoded as application specific link attribute as 282 specified in [I-D.ietf-isis-te-app] and Section 11 of this 283 document. 285 2: Traffic Engineering Default Metric as defined in [RFC5305], 286 section 3.7, encoded as application specific link attribute as 287 specified in [I-D.ietf-isis-te-app] and Section 11 of this 288 document. 290 Calc-Type: value from 0 to 127 inclusive from the "IGP Algorithm 291 Types" registry defined under "Interior Gateway Protocol (IGP) 292 Parameters" IANA registries. IGP algorithms in the range of 0-127 293 have a defined triplet (Calculation Type, Metric, Constraints). 294 When used to specify the Calc-Type in the FAD Sub-TLV, only the 295 Calculation Type defined for the specified IGP Algorithm is used. 296 The Metric/Constraints MUST NOT be inherited. If the required 297 calculation type is Shortest Path First, the value 0 SHOULD appear 298 in this field. 300 Priority: Value between 0 and 255 inclusive that specifies the 301 priority of the advertisement. 303 Sub-TLVs - optional sub-TLVs. 305 The ISIS FAD Sub-TLV MAY be advertised in an LSP of any number, but a 306 router MUST NOT advertise more than one ISIS FAD Sub-TLV for a given 307 Flexible-Algorithm. A router receiving multiple ISIS FAD Sub-TLVs 308 for a given Flexible-Algorithm from the same originator SHOULD select 309 the first advertisement in the lowest numbered LSP. 311 The ISIS FAD Sub-TLV has an area scope. The Router Capability TLV in 312 which the FAD Sub-TLV is present MUST have the S-bit clear. 314 ISIS L1/L2 router MAY be configured to re-generate the winning FAD 315 from level 2, without any modification to it, to level 1 area. The 316 re-generation of the FAD Sub-TLV from level 2 to level 1 is 317 determined by the L1/L2 router, not by the originator of the FAD 318 advertisement in the level 2. In such case, the re-generated FAD 319 Sub-TLV will be advertised in the level 1 Router Capability TLV 320 originated by the L1/L2 router. 322 L1/L2 router MUST NOT re-generate any FAD Sub-TLV from level 1 to 323 level 2. 325 5.2. OSPF Flexible Algorithm Definition TLV 327 OSPF FAD TLV is advertised as a top-level TLV of the RI LSA that is 328 defined in [RFC7770]. 330 OSPF FAD TLV has the following format: 332 0 1 2 3 333 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 1 334 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 335 | Type | Length | 336 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 337 |Flex-Algorithm | Metric-Type | Calc-Type | Priority | 338 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 339 | Sub-TLVs | 340 + + 341 | ... | 343 | | 344 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 346 where: 348 Type: 16 350 Length: variable, dependent on the included Sub-TLVs 352 Flex-Algorithm:: Flex-Algorithm number. Value between 128 and 255 353 inclusive. 355 Metric-Type: Type of metric to be used during the calculation. 356 Following values are defined: 358 0: IGP Metric 360 1: Min Unidirectional Link Delay as defined in [RFC7471], 361 section 4.2, encoded as application specific link attribute as 362 specified in [I-D.ietf-ospf-te-link-attr-reuse] and Section 11 363 of this document. 365 2: Traffic Engineering metric as defined in [RFC3630], section 366 2.5.5, encoded as application specific link attribute as 367 specified in [I-D.ietf-ospf-te-link-attr-reuse] and Section 11 368 of this document. 370 Calc-Type: as described in Section 5.1 372 Priority: as described in Section 5.1 374 Sub-TLVs - optional sub-TLVs. 376 When multiple OSPF FAD TLVs, for the same Flexible-Algorithm, are 377 received from a given router, the receiver MUST use the first 378 occurrence of the TLV in the Router Information LSA. If the OSPF FAD 379 TLV, for the same Flex-Algorithm, appears in multiple Router 380 Information LSAs that have different flooding scopes, the OSPF FAD 381 TLV in the Router Information LSA with the area-scoped flooding scope 382 MUST be used. If the OSPF FAD TLV, for the same algorithm, appears 383 in multiple Router Information LSAs that have the same flooding 384 scope, the OSPF FAD TLV in the Router Information (RI) LSA with the 385 numerically smallest Instance ID MUST be used and subsequent 386 instances of the OSPF FAD TLV MUST be ignored. 388 The RI LSA can be advertised at any of the defined opaque flooding 389 scopes (link, area, or Autonomous System (AS)). For the purpose of 390 OSPF FAD TLV advertisement, area-scoped flooding is REQUIRED. The 391 Autonomous System flooding scope SHOULD NOT be used by default unless 392 local configuration policy on the originating router indicates domain 393 wide flooding. 395 5.3. Common Handling of Flexible Algorithm Definition TLV 397 This section describes the protocol-independent handling of the FAD 398 TLV (OSPF) or FAD Sub-TLV (ISIS). We will refer to it as FAD TLV in 399 this section, even though in case of ISIS it is a Sub-TLV. 401 The value of the Flex-Algorithm MUST be between 128 and 255 402 inclusive. If it is not, the FAD TLV MUST be ignored. 404 Only a subset of the routers participating in the particular Flex- 405 Algorithm need to advertise the definition of the Flex-Algorithm. 407 Every router, that is configured to participate in a particular Flex- 408 Algorithm, MUST select the Flex-Algorithm definition based on the 409 following ordered rules. This allows for the consistent Flex- 410 Algorithm definition selection in cases where different routers 411 advertise different definitions for a given Flex-Algorithm: 413 1. From the advertisements of the FAD in the area (including both 414 locally generated advertisements and received advertisements) 415 select the one(s) with the highest priority value. 417 2. If there are multiple advertisements of the FAD with the same 418 highest priority, select the one that is originated from the 419 router with the highest System-ID, in the case of ISIS, or Router 420 ID, in the case of OSPFv2 and OSPFv3. For ISIS, the System-ID is 421 described in [ISO10589]. For OSPFv2 and OSPFv3, standard Router 422 ID is described in [RFC2328] and [RFC5340] respectively. 424 A router that is not configured to participate in a particular Flex- 425 Algorithm MUST ignore FAD Sub-TLVs advertisements for such Flex- 426 Algorithm. 428 A router that is not participating in a particular Flex-Algorithm is 429 allowed to advertise FAD for such Flex-Algorithm. Receiving routers 430 MUST consider FAD advertisement regardless of the Flex-Algorithm 431 participation of the FAD originator. 433 Any change in the Flex-Algorithm definition may result in temporary 434 disruption of traffic that is forwarded based on such Flex-Algorithm 435 paths. The impact is similar to any other event that requires 436 network-wide convergence. 438 If a node is configured to participate in a particular Flexible- 439 Algorithm, but the selected Flex-Algorithm definition includes 440 calculation-type, metric-type, constraint, flag, or Sub-TLV that is 441 not supported by the node, it MUST stop participating in such 442 Flexible-Algorithm. That implies that it MUST NOT announce 443 participation for such Flexible-Algorithm as specified in Section 10 444 and it MUST remove any forwarding state associated with it. 446 Flex-Algorithm definition is topology independent. It applies to all 447 topologies that a router participates in. 449 6. Sub-TLVs of ISIS FAD Sub-TLV 451 6.1. ISIS Flexible Algorithm Exclude Admin Group Sub-TLV 453 The Flexible Algorithm definition can specify 'colors' that are used 454 by the operator to exclude links during the Flex-Algorithm path 455 computation. 457 The ISIS Flexible Algorithm Exclude Admin Group Sub-TLV is used to 458 advertise the exclude rule that is used during the Flex-Algorithm 459 path calculation as specified in Section 12. 461 The ISIS Flexible Algorithm Exclude Admin Group Sub-TLV (FAEAG Sub- 462 TLV) is a Sub-TLV of the ISIS FAD Sub-TLV. It has the following 463 format: 465 0 1 2 3 466 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 1 467 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 468 | Type | Length | 469 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 470 | Extended Admin Group | 471 +- -+ 472 | ... | 473 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 474 where: 476 Type: 1 478 Length: variable, dependent on the size of the Extended Admin 479 Group. MUST be a multiple of 4 octets. 481 Extended Administrative Group: Extended Administrative Group as 482 defined in [RFC7308]. 484 The ISIS FAEAG Sub-TLV MUST NOT appear more then once in an ISIS FAD 485 Sub-TLV. If it appears more then once, the ISIS FAD Sub-TLV MUST be 486 ignored by the receiver. 488 6.2. ISIS Flexible Algorithm Include-Any Admin Group Sub-TLV 490 The Flexible Algorithm definition can specify 'colors' that are used 491 by the operator to include links during the Flex-Algorithm path 492 computation. 494 The ISIS Flexible Algorithm Include-Any Admin Group Sub-TLV is used 495 to advertise include-any rule that is used during the Flex-Algorithm 496 path calculation as specified in Section 12. 498 The format of the ISIS Flexible Algorithm Include-Any Admin Group 499 Sub-TLV is identical to the format of the FAEAG Sub-TLV in 500 Section 6.1. 502 The ISIS Flexible Algorithm Include-Any Admin Group Sub-TLV Type is 503 2. 505 The ISIS Flexible Algorithm Include-Any Admin Group Sub-TLV MUST NOT 506 appear more then once in an ISIS FAD Sub-TLV. If it appears more 507 then once, the ISIS FAD Sub-TLV MUST be ignored by the receiver. 509 6.3. ISIS Flexible Algorithm Include-All Admin Group Sub-TLV 511 The Flexible Algorithm definition can specify 'colors' that are used 512 by the operator to include link during the Flex-Algorithm path 513 computation. 515 The ISIS Flexible Algorithm Include-All Admin Group Sub-TLV is used 516 to advertise include-all rule that is used during the Flex-Algorithm 517 path calculation as specified in Section 12. 519 The format of the ISIS Flexible Algorithm Include-All Admin Group 520 Sub-TLV is identical to the format of the FAEAG Sub-TLV in 521 Section 6.1. 523 The ISIS Flexible Algorithm Include-All Admin Group Sub-TLV Type is 524 3. 526 The ISIS Flexible Algorithm Include-All Admin Group Sub-TLV MUST NOT 527 appear more then once in an ISIS FAD Sub-TLV. If it appears more 528 then once, the ISIS FAD Sub-TLV MUST be ignored by the receiver. 530 6.4. ISIS Flexible Algorithm Definition Flags Sub-TLV 532 The ISIS Flexible Algorithm Definition Flags Sub-TLV (FADF Sub-TLV) 533 is a Sub-TLV of the ISIS FAD Sub-TLV. It has the following format: 535 0 1 2 3 536 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 1 537 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 538 | Type | Length | 539 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 540 | Flags | 541 +- -+ 542 | ... | 543 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 544 where: 546 Type: 4 548 Length: variable, non-zero number of octets of the Flags field 550 Flags: 552 0 1 2 3 4 5 6 7... 553 +-+-+-+-+-+-+-+-+... 554 |M| | | ... 555 +-+-+-+-+-+-+-+-+... 557 M-flag: when set, the Flex-Algorithm specific prefix metric 558 MUST be used, if advertised with the prefix. This flag is not 559 applicable to prefixes advertised as SRv6 locators. 561 Bits are defined/sent starting with Bit 0 defined above. Additional 562 bit definitions that may be defined in the future SHOULD be assigned 563 in ascending bit order so as to minimize the number of bits that will 564 need to be transmitted. 566 Undefined bits MUST be transmitted as 0. 568 Bits that are NOT transmitted MUST be treated as if they are set to 0 569 on receipt. 571 The ISIS FADF Sub-TLV MUST NOT appear more then once in an ISIS FAD 572 Sub-TLV. If it appears more then once, the ISIS FAD Sub-TLV MUST be 573 ignored by the receiver. 575 If the ISIS FADF Sub-TLV is not present inside the ISIS FAD Sub-TLV, 576 all the bits are assumed to be set to 0. 578 6.5. ISIS Flexible Algorithm Exclude SRLG Sub-TLV 580 The Flexible Algorithm definition can specify Shared Risk Link Groups 581 (SRLGs) that the operator wants to exclude during the Flex-Algorithm 582 path computation. 584 The ISIS Flexible Algorithm Exclude SRLG Sub-TLV (FAESRLG) is used to 585 advertise the exclude rule that is used during the Flex-Algorithm 586 path calculation as specified in Section 12. 588 The ISIS FAESRLG Sub-TLV is a Sub-TLV of the ISIS FAD Sub-TLV. It 589 has the following format: 591 0 1 2 3 592 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 1 593 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 594 | Type | Length | 595 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 596 | Shared Risk Link Group Value | 597 +- -+ 598 | ... | 599 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 600 where: 602 Type: 5 603 Length: variable, dependent on number of SRLG values. MUST be a 604 multiple of 4 octets. 606 Shared Risk Link Group Value: SRLG value as defined in [RFC5307]. 608 The ISIS FAESRLG Sub-TLV MUST NOT appear more then once in an ISIS 609 FAD Sub-TLV. If it appears more then once, the ISIS FAD Sub-TLV MUST 610 be ignored by the receiver. 612 7. Sub-TLVs of OSPF FAD TLV 614 7.1. OSPF Flexible Algorithm Exclude Admin Group Sub-TLV 616 The Flexible Algorithm Exclude Admin Group Sub-TLV (FAEAG Sub-TLV) is 617 a Sub-TLV of the OSPF FAD TLV. It's usage is described in 618 Section 6.1. It has the following format: 620 0 1 2 3 621 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 1 622 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 623 | Type | Length | 624 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 625 | Extended Admin Group | 626 +- -+ 627 | ... | 628 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 629 where: 631 Type: 1 633 Length: variable, dependent on the size of the Extended Admin 634 Group. MUST be a multiple of 4 octets. 636 Extended Administrative Group: Extended Administrative Group as 637 defined in [RFC7308]. 639 The OSPF FAEAG Sub-TLV MUST NOT appear more then once in an OSPF FAD 640 TLV. If it appears more then once, the OSPF FAD TLV MUST be ignored 641 by the receiver. 643 7.2. OSPF Flexible Algorithm Include-Any Admin Group Sub-TLV 645 The usage of this Sub-TLVs is described in Section 6.2. 647 The format of the OSPF Flexible Algorithm Include-Any Admin Group 648 Sub-TLV is identical to the format of the OSPF FAEAG Sub-TLV in 649 Section 7.1. 651 The OSPF Flexible Algorithm Include-Any Admin Group Sub-TLV Type is 652 2. 654 The OSPF Flexible Algorithm Include-Any Admin Group Sub-TLV MUST NOT 655 appear more then once in an OSPF FAD TLV. If it appears more then 656 once, the OSPF FAD TLV MUST be ignored by the receiver. 658 7.3. OSPF Flexible Algorithm Include-All Admin Group Sub-TLV 660 The usage of this Sub-TLVs is described in Section 6.3. 662 The format of the OSPF Flexible Algorithm Include-Any Admin Group 663 Sub-TLV is identical to the format of the OSPF FAEAG Sub-TLV in 664 Section 7.1. 666 The OSPF Flexible Algorithm Include-Any Admin Group Sub-TLV Type is 667 3. 669 The OSPF Flexible Algorithm Include-All Admin Group Sub-TLV MUST NOT 670 appear more then once in an OSPF FAD TLV. If it appears more then 671 once, the OSPF FAD TLV MUST be ignored by the receiver. 673 7.4. OSPF Flexible Algorithm Definition Flags Sub-TLV 675 The OSPF Flexible Algorithm Definition Flags Sub-TLV (FADF Sub-TLV) 676 is a Sub-TLV of the OSPF FAD TLV. It has the following format: 678 0 1 2 3 679 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 1 680 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 681 | Type | Length | 682 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 683 | Flags | 684 +- -+ 685 | ... | 686 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 687 where: 689 Type: 4 691 Length: variable, dependent on the size of the Flags field. MUST 692 be a multiple of 4 octets. 694 Flags: 696 0 1 2 3 4 5 6 7... 697 +-+-+-+-+-+-+-+-+... 698 |M| | | ... 699 +-+-+-+-+-+-+-+-+... 701 M-flag: when set, the Flex-Algorithm specific prefix metric 702 MUST be used, if advertised with the prefix. This flag is not 703 applicable to prefixes advertised as SRv6 locators. 705 Bits are defined/sent starting with Bit 0 defined above. Additional 706 bit definitions that may be defined in the future SHOULD be assigned 707 in ascending bit order so as to minimize the number of bits that will 708 need to be transmitted. 710 Undefined bits MUST be transmitted as 0. 712 Bits that are NOT transmitted MUST be treated as if they are set to 0 713 on receipt. 715 The OSPF FADF Sub-TLV MUST NOT appear more then once in an OSPF FAD 716 TLV. If it appears more then once, the OSPF FAD TLV MUST be ignored 717 by the receiver. 719 If the OSPF FADF Sub-TLV is not present inside the OSPF FAD TLV, all 720 the bits are assumed to be set to 0. 722 7.5. OSPF Flexible Algorithm Exclude SRLG Sub-TLV 724 The OSPF Flexible Algorithm Exclude SRLG Sub-TLV (FAESRLG Sub-TLV) is 725 a Sub-TLV of the OSPF FAD TLV. Its usage is described in 726 Section 6.5. It has the following format: 728 0 1 2 3 729 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 1 730 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 731 | Type | Length | 732 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 733 | Shared Risk Link Group Value | 734 +- -+ 735 | ... | 736 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 737 where: 739 Type: 5 741 Length: variable, dependent on the number of SRLGs. MUST be a 742 multiple of 4 octets. 744 Shared Risk Link Group Value: SRLG value as defined in [RFC4203]. 746 The OSPF FAESRLG Sub-TLV MUST NOT appear more then once in an OSPF 747 FAD TLV. If it appears more then once, the OSPF FAD TLV MUST be 748 ignored by the receiver. 750 8. ISIS Flexible Algorithm Prefix Metric Sub-TLV 752 The ISIS Flexible Algorithm Prefix Metric (FAPM) Sub-TLV supports the 753 advertisement of a Flex-Algorithm specific prefix metric associated 754 with a given prefix advertisement. 756 The ISIS FAPM Sub-TLV is a sub-TLV of TLVs 135, 235, 236, and 237 and 757 has the following format: 759 0 1 2 3 760 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 1 761 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 762 | Type | Length |Flex-Algorithm | 763 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 764 | Metric | 765 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 766 where: 768 Type: 6 770 Length: 5 octets 772 Flex-Algorithm: Single octet value between 128 and 255 inclusive. 774 Metric: 4 octets of metric information 776 The ISIS FAPM Sub-TLV MAY appear multiple times in its parent TLV. 777 If it appears more then once with the same Flex-Algorithm value, the 778 first instance MUST be used and any subsequent instances MUST be 779 ignored. 781 If a prefix is advertised with a Flex-Algorithm prefix metric larger 782 then MAX_PATH_METRIC as defined in [RFC5305] this prefix MUST NOT be 783 considered during the Flexible-Algorithm computation. 785 The usage of the Flex-Algorithm prefix metric is described in 786 Section 12. 788 The ISIS FAPM Sub-TLV MUST NOT be advertised as a sub-TLV of the ISIS 789 SRv6 Locator TLV [I-D.ietf-lsr-isis-srv6-extensions]. The ISIS SRv6 790 Locator TLV includes the Algorithm and Metric fields which MUST be 791 used instead. If the FAPM Sub-TLV is present as a sub-TLV of the 792 ISIS SRv6 Locator TLV in the received LSP, such FAPM Sub-TLV MUST be 793 ignored. 795 9. OSPF Flexible Algorithm Prefix Metric Sub-TLV 797 The OSPF Flexible Algorithm Prefix Metric (FAPM) Sub-TLV supports the 798 advertisement of a Flex-Algorithm specific prefix metric associated 799 with a given prefix advertisement. 801 The OSPF Flex-Algorithm Prefix Metric (FAPM) Sub-TLVis a Sub-TLV of 802 the: 804 - OSPFv2 Extended Prefix TLV [RFC7684] 806 - Following OSPFv3 TLVs as defined in [RFC8362]: 808 Intra-Area Prefix TLV 810 Inter-Area Prefix TLV 812 External Prefix TLV 814 OSPF FAPM Sub-TLV has the following format: 816 0 1 2 3 817 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 1 818 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 819 | Type | Length | 820 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 821 |Flex-Algorithm | Reserved | 822 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 823 | Metric | 824 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 826 where: 828 Type: 3 for OSPFv2, 26 for OSPFv3 830 Length: 8 octets 832 Flex-Algorithm: Single octet value between 128 and 255 inclusive. 834 Reserved: Must be set to 0, ignored at reception. 836 Metric: 4 octets of metric information 838 The OSPF FAPM Sub-TLV MAY appear multiple times in its parent TLV. 839 If it appears more then once with the same Flex-Algorithm value, the 840 first instance MUST be used and any subsequent instances MUST be 841 ignored. 843 The usage of the Flex-Algorithm prefix metric is described in 844 Section 12. 846 10. Advertisement of Node Participation in a Flex-Algorithm 848 When a router is configured to support a particular Flex-Algorithm, 849 we say it is participating in that Flex-Algorithm. 851 Paths computed for a specific Flex-Algorithm MAY be used by various 852 applications, each potentially using its own specific data plane for 853 forwarding traffic over such paths. To guarantee the presence of the 854 application specific forwarding state associated with a particular 855 Flex-Algorithm, a router MUST advertise its participation for a 856 particular Flex-Algorithm for each application specifically. 858 10.1. Advertisement of Node Participation for Segment Routing 860 [RFC8667], [RFC8665], and [RFC8666] (IGP Segment Routing extensions) 861 describe how the SR-Algorithm is used to compute the IGP best path. 863 Routers advertise the support for the SR-Algorithm as a node 864 capability as described in the above mentioned IGP Segment Routing 865 extensions. To advertise participation for a particular Flex- 866 Algorithm for Segment Routing, including both SR MPLS and SRv6, the 867 Flex-Algorithm value MUST be advertised in the SR-Algorithm TLV 868 (OSPF) or sub-TLV (ISIS). 870 Segment Routing Flex-Algorithm participation advertisement is 871 topology independent. When a router advertises participation in an 872 SR-Algorithm, the participation applies to all topologies in which 873 the advertising node participates. 875 10.2. Advertisement of Node Participation for Other Applications 877 This section describes considerations related to how other 878 applications can advertise their participation in a specific Flex- 879 Algorithm. 881 Application-specific Flex-Algorithm participation advertisements MAY 882 be topology specific or MAY be topology independent, depending on the 883 application itself. 885 Application-specific advertisement for Flex-Algorithm participation 886 MUST be defined for each application and is outside of the scope of 887 this document. 889 11. Advertisement of Link Attributes for Flex-Algorithm 891 Various link attributes may be used during the Flex-Algorithm path 892 calculation. For example, include or exclude rules based on link 893 affinities can be part of the Flex-Algorithm definition as defined in 894 Section 6 and Section 7. 896 Link attribute advertisements that are to be used during Flex- 897 Algorithm calculation MUST use the Application-Specific Link 898 Attribute (ASLA) advertisements defined in [I-D.ietf-isis-te-app] or 899 [I-D.ietf-ospf-te-link-attr-reuse]. In the case of IS-IS, this 900 includes use of the L-flag as defined in [I-D.ietf-isis-te-app] 901 Section 4.2 subject to the constraints discussed in Section 6 of the 902 [I-D.ietf-isis-te-app]. The mandatory use of ASLA advertisements 903 applies to link attributes specifically mentioned in this document 904 (Min Unidirectional Link Delay, TE Default Metric, Administrative 905 Group, Extended Administrative Group and Shared Risk Link Group) and 906 any other link attributes that may be used in support of Flex- 907 Algorithm in the future. 909 A new Application Identifier Bit is defined to indicate that the ASLA 910 advertisement is associated with the Flex-Algorithm application. 911 This bit is set in the Standard Application Bit Mask (SABM) defined 912 in [I-D.ietf-isis-te-app] or [I-D.ietf-ospf-te-link-attr-reuse]: 914 Bit-3: Flexible Algorithm (X-bit) 916 ASLA Admin Group Advertisements to be used by the Flexible Algorithm 917 Application MAY use either the Administrative Group or Extended 918 Administrative Group encodings. If the Administrative Group encoding 919 is used, then the first 32 bits of the corresponding FAD sub-TLVs are 920 mapped to the link attribute advertisements as specified in RFC 7308. 922 12. Calculation of Flexible Algorithm Paths 924 A router MUST be configured to participate in a given Flex-Algorithm 925 K and MUST select the FAD based on the rules defined in Section 5.3 926 before it can compute any path for that Flex-Algorithm. 928 As described in Section 10, participation for any particular Flex- 929 Algorithm MUST be advertised on a per-application basis. Calculation 930 of the paths for any particular Flex-Algorithm MUST be application 931 specific. 933 The way applications handle nodes that do not participate in 934 Flexible-Algorithm is application specific. If the application only 935 wants to consider participating nodes during the Flex-Algorithm 936 calculation, then when computing paths for a given Flex-Algorithm, 937 all nodes that do not advertise participation for that Flex-Algorithm 938 in their application-specific advertisements MUST be pruned from the 939 topology. Segment Routing, including both SR MPLS and SRv6, are 940 applications that MUST use such pruning when computing Flex-Algorithm 941 paths. 943 When computing the path for a given Flex-Algorithm, the metric-type 944 that is part of the Flex-Algorithm definition (Section 5) MUST be 945 used. 947 When computing the path for a given Flex-Algorithm, the calculation- 948 type that is part of the Flex-Algorithm definition (Section 5) MUST 949 be used. 951 Various link include or exclude rules can be part of the Flex- 952 Algorithm definition. To refer to a particular bit within an AG or 953 EAG we uses term 'color'. 955 Rules, in the order as specified below, MUST be used to prune links 956 from the topology during the Flex-Algorithm computation. 958 For all links in the topology: 960 1. Check if any exclude rule is part of the Flex-Algorithm 961 definition. If such exclude rule exists, check if any color that 962 is part of the exclude rule is also set on the link. If such a 963 color is set, the link MUST be pruned from the computation. 965 2. Check if any exclude SRLG rule is part of the Flex-Algorithm 966 definition. If such exclude rule exists, check if the link is 967 part of any SRLG that is also part of the SRLG exclude rule. If 968 the link is part of such SRLG, the link MUST be pruned from the 969 computation. 971 3. Check if any include-any rule is part of the Flex-Algorithm 972 definition. If such include-any rule exists, check if any color 973 that is part of the include-any rule is also set on the link. If 974 no such color is set, the link MUST be pruned from the 975 computation. 977 4. Check if any include-all rule is part of the Flex-Algorithm 978 definition. If such include-all rule exists, check if all colors 979 that are part of the include-all rule are also set on the link. 980 If all such colors are not set on the link, the link MUST be 981 pruned from the computation. 983 5. If the Flex-Algorithm definition uses other than IGP metric 984 (Section 5), and such metric is not advertised for the particular 985 link in a topology for which the computation is done, such link 986 MUST be pruned from the computation. A metric of value 0 MUST NOT 987 be assumed in such case. 989 12.1. Multi-area and Multi-domain Considerations 991 Any IGP Shortest Path Tree calculation is limited to a single area. 992 This applies to Flex-Algorithm calculations as well. Given that the 993 computing router does not have visibility of the topology of the next 994 areas or domain, the Flex-Algorithm specific path to an inter-area or 995 inter-domain prefix will be computed for the local area only. The 996 egress L1/L2 router (ABR in OSPF), or ASBR for inter-domain case, 997 will be selected based on the best path for the given Flex-Algorithm 998 in the local area and such egress ABR or ASBR router will be 999 responsible to compute the best Flex-Algorithm specific path over the 1000 next area or domain. This may produce an end-to-end path, which is 1001 sub-optimal based on Flex-Algorithm constraints. In cases where the 1002 ABR or ASBR has no reachability to a prefix for a given Flex- 1003 Algorithm in the next area or domain, the traffic may be dropped by 1004 the ABR/ASBR. 1006 To allow the optimal end-to-end path for an inter-area or inter- 1007 domain prefix for any Flex-Algorithm to be computed, the FAPM has 1008 been defined in Section 8 and Section 9. 1010 If the FAD selected based on the rules defined in Section 5.3 1011 includes the M-flag, an ABR or ASBR MUST include the FAPM (Section 8, 1012 Section 9) when advertising the prefix between areas or domains. 1013 Such metric will be equal to the metric to reach the prefix for a 1014 given Flex-Algorithm in a source area or domain. This is similar in 1015 nature to how the metric is set when prefixes are advertised between 1016 areas or domains for the default algorithm. 1018 If the FAD selected based on the rules defined in Section 5.3 1019 includes the M-flag, the FAPM MUST be used during calculation of 1020 prefix reachability for the inter-area and external prefixes. If the 1021 FAPM for the Flex-Algorithm is not advertised with the inter-area or 1022 external prefix reachability advertisement, the prefix MUST be 1023 considered as unreachable for that Flex-Algorithm. 1025 Flex-Algorithm prefix metrics MUST NOT be used during the Flex- 1026 Algorithm computation unless the FAD selected based on the rules 1027 defined in Section 5.3 includes the M-Flag, as described in 1028 (Section 6.4 or Section 7.4). 1030 If the FAD selected based on the rules defined in Section 5.3 does 1031 not includes the M-flag, it is NOT RECOMMENDED to use the Flex- 1032 Algorithm for inter-area or inter-domain prefix reachability. The 1033 reason is that without the explicit Flex-Algorithm Prefix Metric 1034 advertisement, it is not possible to conclude whether the ABR or ASBR 1035 has reachability to the inter-area or inter-domain prefix for a given 1036 Flex-Algorithm in the next area or domain. Sending the Flex-Algoritm 1037 traffic for such prefix towards the ABR or ASBR may result in traffic 1038 looping or black-holing. 1040 The FAPM MUST NOT be advertised with ISIS L1 or L2 intra-area, OSPFv2 1041 intra-area, or OSPFv3 intra-area routes. If the FAPM is advertised 1042 for these route-types, it MUST be ignored during the prefix 1043 reachability calculation. 1045 The M-flag in FAD is not applicable to prefixes advertised as SRv6 1046 locators. The ISIS SRv6 Locator TLV includes the Algorithm and 1047 Metric fields [I-D.ietf-lsr-isis-srv6-extensions]. When the ISIS 1048 SRv6 Locator is advertised between areas or domains, the metric field 1049 in the Locator TLV MUST be used irrespective of the M-flag in the FAD 1050 advertisement. 1052 13. Flex-Algorithm and Forwarding Plane 1054 This section describes how Flex-Algorithm paths are used in 1055 forwarding. 1057 13.1. Segment Routing MPLS Forwarding for Flex-Algorithm 1059 This section describes how Flex-Algorithm paths are used with SR MPLS 1060 forwarding. 1062 Prefix SID advertisements include an SR-Algorithm value and, as such, 1063 are associated with the specified SR-Algorithm. Prefix-SIDs are also 1064 associated with a specific topology which is inherited from the 1065 associated prefix reachability advertisement. When the algorithm 1066 value advertised is a Flex-Algorithm value, the Prefix SID is 1067 associated with paths calculated using that Flex-Algorithm in the 1068 associated topology. 1070 A Flex-Algorithm path MUST be installed in the MPLS forwarding plane 1071 using the MPLS label that corresponds to the Prefix-SID that was 1072 advertised for that Flex-algorithm. If the Prefix SID for a given 1073 Flex-algorithm is not known, the Flex-Algorithm specific path cannot 1074 be installed in the MPLS forwarding plane. 1076 Traffic that is supposed to be routed via Flex-Algorithm specific 1077 paths, MUST be dropped when there are no such paths available. 1079 Loop Free Alternate (LFA) paths for a given Flex-Algorithm MUST be 1080 computed using the same constraints as the calculation of the primary 1081 paths for that Flex-Algorithm. LFA paths MUST only use Prefix-SIDs 1082 advertised specifically for the given algorithm. LFA paths MUST NOT 1083 use an Adjacency-SID that belongs to a link that has been pruned from 1084 the Flex-Algorithm computation. 1086 If LFA protection is being used to protect a given Flex-Algorithm 1087 paths, all routers in the area participating in the given Flex- 1088 Algorithm SHOULD advertise at least one Flex-Algorithm specific Node- 1089 SID. These Node-SIDs are used to steer traffic over the LFA computed 1090 backup path. 1092 13.2. SRv6 Forwarding for Flex-Algorithm 1094 This section describes how Flex-Algorithm paths are used with SRv6 1095 forwarding. 1097 In SRv6 a node is provisioned with topology/algorithm specific 1098 locators for each of the topology/algorithm pairs supported by that 1099 node. Each locator is an aggregate prefix for all SIDs provisioned 1100 on that node which have the matching topology/algorithm. 1102 The SRv6 locator advertisement in IGPs 1103 ([I-D.ietf-lsr-isis-srv6-extensions] 1104 [I-D.ietf-lsr-ospfv3-srv6-extensions]) includes the MTID value that 1105 associates the locator with a specific topology. SRv6 locator 1106 advertisements also includes an Algorithm value that explicitly 1107 associates the locator with a specific algorithm. When the algorithm 1108 value advertised with a locator represents a Flex-Algorithm, the 1109 paths to the locator prefix MUST be calculated using the specified 1110 Flex-Algorithm in the associated topology. 1112 Forwarding entries for the locator prefixes advertised in IGPs MUST 1113 be installed in the forwarding plane of the receiving SRv6 capable 1114 routers when the associated topology/algorithm is participating in 1115 them. Forwarding entries for locators associated with Flex- 1116 Algorithms in which the node is not participating MUST NOT be 1117 installed in the forwarding palne. 1119 When the locator is associated with a Flex-Algorithm, LFA paths to 1120 the locator prefix MUST be calculated using such Flex-Algorithm in 1121 the associated topology, to guarantee that they follow the same 1122 constraints as the calculation of the primary paths. LFA paths MUST 1123 only use SRv6 SIDs advertised specifically for the given Flex- 1124 Algorithm. 1126 If LFA protection is being used to protect locators associated with a 1127 given Flex-Algorithm, all routers in the area participating in the 1128 given Flex-Algorithm SHOULD advertise at least one Flex-Algorithm 1129 specific locator and END SID per node and one END.X SID for every 1130 link that has not been pruned from such Flex-Algorithm computation. 1131 These locators and SIDs are used to steer traffic over the LFA- 1132 computed backup path. 1134 13.3. Other Applications' Forwarding for Flex-Algorithm 1136 Any application that wants to use Flex-Algorithm specific forwarding 1137 needs to install some form of Flex-Algorithm specific forwarding 1138 entries. 1140 Application-specific forwarding for Flex-Algorithm MUST be defined 1141 for each application and is outside of the scope of this document. 1143 14. Operational considerations 1145 14.1. Inter-area Considerations 1147 The scope of the FA computation is an area, so is the scope of the 1148 FAD. In ISIS, the Router Capability TLV in which the FAD Sub-TLV is 1149 advertised MUST have the S-bit clear, which prevents it to be flooded 1150 outside of the level in which it was originated. Even though in OSPF 1151 the FAD Sub-TLV can be flooded in an RI LSA that has AS flooding 1152 scope, the FAD selection is performed for each individual area in 1153 which it is being used. 1155 There is no requirement for the FAD for a particular Flex-Algorithm 1156 to be identical in all areas in the network. For example, traffic 1157 for the same Flex-Algorithm may be optimized for minimal delay (e.g., 1158 using delay metric) in one area or level, while being optimized for 1159 available bandwidth (e.g., using IGP metric) in another area or 1160 level. 1162 As described in Section 5.1, ISIS allows the re-generation of the 1163 winning FAD from level 2, without any modification to it, into a 1164 level 1 area. This allows the operator to configure the FAD in one 1165 or multiple routers in the level 2, without the need to repeat the 1166 same task in each level 1 area, if the intent is to have the same FAD 1167 for the particular Flex-Algorithm across all levels. This can 1168 similarly be achieved in OSPF by using the AS flooding scope of the 1169 RI LSA in which the FAD Sub-TLV for the particular Flex-Algoritm is 1170 advertised. 1172 Re-generation of FAD from a level 1 area to the level 2 area is not 1173 supported in ISIS, so if the intent is to regenerate the FAD between 1174 ISIS levels, the FAD MUST be defined on router(s) that are in level 1175 2. In OSPF, the FAD definition can be done in any area and be 1176 propagated to all routers in the OSPF routing domain by using the AS 1177 flooding scope of the RI LSA. 1179 14.2. Usage of SRLG Exclude Rule with Flex-Algorithm 1181 There are two different ways in which SRLG information can be used 1182 with Flex-Algorithm: 1184 In a context of a single Flex-Algorithm, it can be used for 1185 computation of backup paths, as described in 1186 [I-D.ietf-rtgwg-segment-routing-ti-lfa]. This usage does not 1187 require association of any specific SRLG constraint with the given 1188 Flex-Algorithm definition. 1190 In the context of multiple Flex-Algorithms, it can be used for 1191 creating disjoint sets of paths by pruning the links belonging to 1192 a specific SRLG from the topology on which a specific Flex- 1193 Algorithm computes its paths. This usage: 1195 Facilitates the usage of already deployed SRLG configurations 1196 for setup of disjoint paths between two or more Flex- 1197 Algorithms. 1199 Requires explicit association of a given Flex-Algorithm with a 1200 specific set of SRLG constraints as defined in Section 6.5 and 1201 Section 7.5. 1203 The two usages mentioned above are orthogonal. 1205 14.3. Max-metric consideration 1207 Both ISIS and OSPF have a mechanism to set the IGP metric on a link 1208 to a value that would make the link either non-reachable or to serve 1209 as the link of last resort. Similar functionality would be needed 1210 for the Min Unidirectional Link Delay and TE metric, as these can be 1211 used to compute Flex-Algorithm paths. 1213 The link can be made un-reachable for all Flex-Algorithms that use 1214 Min Unidirectional Link Delay as metric, as described in Section 5.1, 1215 by removing the Flex-Algorithm ASLA Min Unidirectional Link Delay 1216 advertisement for the link. The link can be made the link of last 1217 resort by setting the delay value in the Flex-Algorithm ASLA delay 1218 advertisement for the link to the value of 16,777,215 (2^24 - 1). 1220 The link can be made un-reachable for all Flex-Algorithms that use TE 1221 metric, as described in Section 5.1, by removing the Flex-Algorithm 1222 ASLA TE metric advertisement for the link. The link can be made the 1223 link of last resort by setting the TE metric value in the Flex- 1224 Algorithm ASLA delay advertisement for the link to the value of (2^24 1225 - 1) in ISIS and (2^32 - 1) in OSPF. 1227 15. Backward Compatibility 1229 This extension brings no new backward compatibility issues. 1231 16. Security Considerations 1233 This draft adds two new ways to disrupt IGP networks: 1235 An attacker can hijack a particular Flex-Algorithm by advertising 1236 a FAD with a priority of 255 (or any priority higher than that of 1237 the legitimate nodes). 1239 An attacker could make it look like a router supports a particular 1240 Flex-Algorithm when it actually doesn't, or vice versa. 1242 Both of these attacks can be addressed by the existing security 1243 extensions as described in [RFC5304] and [RFC5310] for ISIS, in 1244 [RFC2328] and [RFC7474] for OSPFv2, and in [RFC5340] and [RFC4552] 1245 for OSPFv3. 1247 17. IANA Considerations 1249 17.1. IGP IANA Considerations 1251 17.1.1. IGP Algorithm Types Registry 1253 This document makes the following registrations in the "IGP Algorithm 1254 Types" registry: 1256 Type: 128-255. 1258 Description: Flexible Algorithms. 1260 Reference: This document (Section 4). 1262 17.1.2. IGP Metric-Type Registry 1264 IANA is requested to set up a registry called "IGP Metric-Type 1265 Registry" under a "Interior Gateway Protocol (IGP) Parameters" IANA 1266 registries. The registration policy for this registry is "Standards 1267 Action" ([RFC8126] and [RFC7120]). 1269 Values in this registry come from the range 0-255. 1271 This document registers following values in the "IGP Metric-Type 1272 Registry": 1274 Type: 0 1276 Description: IGP metric 1278 Reference: This document (Section 5.1) 1280 Type: 1 1282 Description: Min Unidirectional Link Delay as defined in 1283 [RFC8570], section 4.2, and [RFC7471], section 4.2. 1285 Reference: This document (Section 5.1) 1287 Type: 2 1289 Description: Traffic Engineering Default Metric as defined in 1290 [RFC5305], section 3.7, and Traffic engineering metric as defined 1291 in [RFC3630], section 2.5.5 1293 Reference: This document (Section 5.1) 1295 17.2. Flexible Algorithm Definition Flags Registry 1297 IANA is requested to set up a registry called "ISIS Flexible 1298 Algorithm Definition Flags Registry" under a "Interior Gateway 1299 Protocol (IGP) Parameters" IANA registries. The registration policy 1300 for this registry is "Standards Action" ([RFC8126] and [RFC7120]). 1302 This document defines the following single bit in Flexible Algorithm 1303 Definition Flags registry: 1305 Bit # Name 1306 ----- ------------------------------ 1307 0 Prefix Metric Flag (M-flag) 1309 Reference: This document (Section 6.4, Section 7.4). 1311 17.3. ISIS IANA Considerations 1313 17.3.1. Sub TLVs for Type 242 1315 This document makes the following registrations in the "sub-TLVs for 1316 TLV 242" registry. 1318 Type: 26. 1320 Description: Flexible Algorithm Definition. 1322 Reference: This document (Section 5.1). 1324 17.3.2. Sub TLVs for for TLVs 135, 235, 236, and 237 1326 This document makes the following registrations in the "Sub-TLVs for 1327 for TLVs 135, 235, 236, and 237" registry. 1329 Type: 6 1331 Description: Flexible Algorithm Prefix Metric. 1333 Reference: This document (Section 8). 1335 17.3.3. Sub-Sub-TLVs for Flexible Algorithm Definition Sub-TLV 1337 This document creates the following Sub-Sub-TLV Registry: 1339 Registry: Sub-Sub-TLVs for Flexible Algorithm Definition Sub-TLV 1341 Registration Procedure: Expert review 1343 Reference: This document (Section 5.1) 1345 This document defines the following Sub-Sub-TLVs in the "Sub-Sub-TLVs 1346 for Flexible Algorithm Definition Sub-TLV" registry: 1348 Type: 1 1350 Description: Flexible Algorithm Exclude Admin Group 1352 Reference: This document (Section 6.1). 1354 Type: 2 1356 Description: Flexible Algorithm Include-Any Admin Group 1358 Reference: This document (Section 6.2). 1360 Type: 3 1362 Description: Flexible Algorithm Include-All Admin Group 1364 Reference: This document (Section 6.3). 1366 Type: 4 1368 Description: Flexible Algorithm Definition Flags 1370 Reference: This document (Section 6.4). 1372 Type: 5 1374 Description: Flexible Algorithm Exclude SRLG 1376 Reference: This document (Section 6.5). 1378 17.4. OSPF IANA Considerations 1380 17.4.1. OSPF Router Information (RI) TLVs Registry 1382 This specification updates the OSPF Router Information (RI) TLVs 1383 Registry. 1385 Type: 16 1387 Description: Flexible Algorithm Definition TLV. 1389 Reference: This document (Section 5.2). 1391 17.4.2. OSPFv2 Extended Prefix TLV Sub-TLVs 1393 This document makes the following registrations in the "OSPFv2 1394 Extended Prefix TLV Sub-TLVs" registry. 1396 Type: 3 1398 Description: Flexible Algorithm Prefix Metric. 1400 Reference: This document (Section 9). 1402 17.4.3. OSPFv3 Extended-LSA Sub-TLVs 1404 This document makes the following registrations in the "OSPFv3 1405 Extended-LSA Sub-TLVs" registry. 1407 Type: 26 1409 Description: Flexible Algorithm Prefix Metric. 1411 Reference: This document (Section 9). 1413 17.4.4. OSPF Flexible Algorithm Definition TLV Sub-TLV Registry 1415 This document creates the following registry: 1417 Registry: OSPF Flexible Algorithm Definition TLV sub-TLV 1419 Registration Procedure: Expert review 1421 Reference: This document (Section 5.2) 1423 The "OSPF Flexible Algorithm Definition TLV sub-TLV" registry will 1424 define sub-TLVs at any level of nesting for the Flexible Algorithm 1425 TLV and should be added to the "Open Shortest Path First (OSPF) 1426 Parameters" registries group. New values can be allocated via IETF 1427 Review or IESG Approval. 1429 This document registers following Sub-TLVs in the "TLVs for Flexible 1430 Algorithm Definition TLV" registry: 1432 Type: 1 1434 Description: Flexible Algorithm Exclude Admin Group 1436 Reference: This document (Section 7.1). 1438 Type: 2 1440 Description: Flexible Algorithm Include-Any Admin Group 1442 Reference: This document (Section 7.2). 1444 Type: 3 1446 Description: Flexible Algorithm Include-All Admin Group 1448 Reference: This document (Section 7.3). 1450 Type: 4 1452 Description: Flexible Algorithm Definition Flags 1454 Reference: This document (Section 7.4). 1456 Type: 5 1458 Description: Flexible Algorithm Exclude SRLG 1460 Reference: This document (Section 7.5). 1462 Types in the range 32768-33023 are for experimental use; these will 1463 not be registered with IANA, and MUST NOT be mentioned by RFCs. 1465 Types in the range 33024-65535 are not to be assigned at this time. 1466 Before any assignments can be made in the 33024-65535 range, there 1467 MUST be an IETF specification that specifies IANA Considerations that 1468 covers the range being assigned. 1470 17.4.5. Link Attribute Applications Registry 1472 This document registers following bit in the Link Attribute 1473 Applications Registry: 1475 Bit-3 1477 Description: Flexible Algorithm (X-bit) 1479 Reference: This document (Section 11). 1481 18. Acknowledgements 1483 This draft, among other things, is also addressing the problem that 1484 the [I-D.gulkohegde-routing-planes-using-sr] was trying to solve. 1485 All authors of that draft agreed to join this draft. 1487 Thanks to Eric Rosen, Tony Przygienda for their detailed review and 1488 excellent comments. 1490 Thanks to Cengiz Halit for his review and feedback during initial 1491 phase of the solution definition. 1493 Thanks to Kenji Kumaki for his comments. 1495 Thanks to William Britto A J. for his suggestions. 1497 Thanks to Acee Lindem for editorial comments. 1499 19. References 1501 19.1. Normative References 1503 [BCP14] "Key words for use in RFCs to Indicate Requirement 1504 Levels", . 1506 [I-D.ietf-isis-te-app] 1507 Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and 1508 J. Drake, "IS-IS Application-Specific Link Attributes", 1509 draft-ietf-isis-te-app-19 (work in progress), June 2020. 1511 [I-D.ietf-lsr-isis-srv6-extensions] 1512 Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and 1513 Z. Hu, "IS-IS Extension to Support Segment Routing over 1514 IPv6 Dataplane", draft-ietf-lsr-isis-srv6-extensions-10 1515 (work in progress), September 2020. 1517 [I-D.ietf-lsr-ospfv3-srv6-extensions] 1518 Li, Z., Hu, Z., Cheng, D., Talaulikar, K., and P. Psenak, 1519 "OSPFv3 Extensions for SRv6", draft-ietf-lsr- 1520 ospfv3-srv6-extensions-01 (work in progress), August 2020. 1522 [I-D.ietf-ospf-te-link-attr-reuse] 1523 Psenak, P., Ginsberg, L., Henderickx, W., Tantsura, J., 1524 and J. Drake, "OSPF Application-Specific Link Attributes", 1525 draft-ietf-ospf-te-link-attr-reuse-16 (work in progress), 1526 June 2020. 1528 [ISO10589] 1529 International Organization for Standardization, 1530 "Intermediate system to Intermediate system intra-domain 1531 routeing information exchange protocol for use in 1532 conjunction with the protocol for providing the 1533 connectionless-mode Network Service (ISO 8473)", ISO/ 1534 IEC 10589:2002, Second Edition, Nov 2002. 1536 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1537 Requirement Levels", BCP 14, RFC 2119, 1538 DOI 10.17487/RFC2119, March 1997, 1539 . 1541 [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in 1542 Support of Generalized Multi-Protocol Label Switching 1543 (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005, 1544 . 1546 [RFC5307] Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions 1547 in Support of Generalized Multi-Protocol Label Switching 1548 (GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008, 1549 . 1551 [RFC7308] Osborne, E., "Extended Administrative Groups in MPLS 1552 Traffic Engineering (MPLS-TE)", RFC 7308, 1553 DOI 10.17487/RFC7308, July 2014, 1554 . 1556 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 1557 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 1558 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 1559 2015, . 1561 [RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and 1562 S. Shaffer, "Extensions to OSPF for Advertising Optional 1563 Router Capabilities", RFC 7770, DOI 10.17487/RFC7770, 1564 February 2016, . 1566 [RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions 1567 for Advertising Router Information", RFC 7981, 1568 DOI 10.17487/RFC7981, October 2016, 1569 . 1571 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1572 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1573 May 2017, . 1575 [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and 1576 F. Baker, "OSPFv3 Link State Advertisement (LSA) 1577 Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 1578 2018, . 1580 [RFC8665] Psenak, P., Ed., Previdi, S., Ed., Filsfils, C., Gredler, 1581 H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 1582 Extensions for Segment Routing", RFC 8665, 1583 DOI 10.17487/RFC8665, December 2019, 1584 . 1586 [RFC8666] Psenak, P., Ed. and S. Previdi, Ed., "OSPFv3 Extensions 1587 for Segment Routing", RFC 8666, DOI 10.17487/RFC8666, 1588 December 2019, . 1590 [RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C., 1591 Bashandy, A., Gredler, H., and B. Decraene, "IS-IS 1592 Extensions for Segment Routing", RFC 8667, 1593 DOI 10.17487/RFC8667, December 2019, 1594 . 1596 19.2. Informative References 1598 [I-D.gulkohegde-routing-planes-using-sr] 1599 Hegde, S. and a. arkadiy.gulko@thomsonreuters.com, 1600 "Separating Routing Planes using Segment Routing", draft- 1601 gulkohegde-routing-planes-using-sr-00 (work in progress), 1602 March 2017. 1604 [I-D.ietf-rtgwg-segment-routing-ti-lfa] 1605 Litkowski, S., Bashandy, A., Filsfils, C., Decraene, B., 1606 Francois, P., Voyer, D., Clad, F., and P. Camarillo, 1607 "Topology Independent Fast Reroute using Segment Routing", 1608 draft-ietf-rtgwg-segment-routing-ti-lfa-04 (work in 1609 progress), August 2020. 1611 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 1612 DOI 10.17487/RFC2328, April 1998, 1613 . 1615 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 1616 (TE) Extensions to OSPF Version 2", RFC 3630, 1617 DOI 10.17487/RFC3630, September 2003, 1618 . 1620 [RFC3906] Shen, N. and H. Smit, "Calculating Interior Gateway 1621 Protocol (IGP) Routes Over Traffic Engineering Tunnels", 1622 RFC 3906, DOI 10.17487/RFC3906, October 2004, 1623 . 1625 [RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality 1626 for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006, 1627 . 1629 [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic 1630 Authentication", RFC 5304, DOI 10.17487/RFC5304, October 1631 2008, . 1633 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 1634 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 1635 2008, . 1637 [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., 1638 and M. Fanto, "IS-IS Generic Cryptographic 1639 Authentication", RFC 5310, DOI 10.17487/RFC5310, February 1640 2009, . 1642 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 1643 for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, 1644 . 1646 [RFC7120] Cotton, M., "Early IANA Allocation of Standards Track Code 1647 Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January 1648 2014, . 1650 [RFC7471] Giacalone, S., Ward, D., Drake, J., Atlas, A., and S. 1651 Previdi, "OSPF Traffic Engineering (TE) Metric 1652 Extensions", RFC 7471, DOI 10.17487/RFC7471, March 2015, 1653 . 1655 [RFC7474] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed., 1656 "Security Extension for OSPFv2 When Using Manual Key 1657 Management", RFC 7474, DOI 10.17487/RFC7474, April 2015, 1658 . 1660 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1661 Writing an IANA Considerations Section in RFCs", BCP 26, 1662 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1663 . 1665 [RFC8570] Ginsberg, L., Ed., Previdi, S., Ed., Giacalone, S., Ward, 1666 D., Drake, J., and Q. Wu, "IS-IS Traffic Engineering (TE) 1667 Metric Extensions", RFC 8570, DOI 10.17487/RFC8570, March 1668 2019, . 1670 Authors' Addresses 1672 Peter Psenak (editor) 1673 Cisco Systems 1674 Apollo Business Center 1675 Mlynske nivy 43 1676 Bratislava, 82109 1677 Slovakia 1679 Email: ppsenak@cisco.com 1681 Shraddha Hegde 1682 Juniper Networks, Inc. 1683 Embassy Business Park 1684 Bangalore, KA, 560093 1685 India 1687 Email: shraddha@juniper.net 1689 Clarence Filsfils 1690 Cisco Systems, Inc. 1691 Brussels 1692 Belgium 1694 Email: cfilsfil@cisco.com 1695 Ketan Talaulikar 1696 Cisco Systems, Inc. 1697 S.No. 154/6, Phase I, Hinjawadi 1698 PUNE, MAHARASHTRA 411 057 1699 India 1701 Email: ketant@cisco.com 1703 Arkadiy Gulko 1704 Individual 1706 Email: arkadiy.gulko@gmail.com