idnits 2.17.1 draft-bonica-lsr-ip-flexalgo-00.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 : ---------------------------------------------------------------------------- ** There is 1 instance of too long lines in the document, the longest one being 2 characters in excess of 72. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (September 29, 2020) is 1276 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in RFCs) == Unused Reference: 'RFC5340' is defined on line 545, but no explicit reference was found in the text == Outdated reference: A later version (-26) exists of draft-ietf-lsr-flex-algo-11 -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO10589' == Outdated reference: A later version (-28) exists of draft-ietf-spring-srv6-network-programming-20 Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 LSR Working Group W. Britto 3 Internet-Draft S. Hegde 4 Intended status: Standards Track P. Kaneriya 5 Expires: April 2, 2021 R. Shetty 6 R. Bonica 7 Juniper Networks 8 September 29, 2020 10 IGP Flexible Algorithms (Flexalgo) In IP Networks 11 draft-bonica-lsr-ip-flexalgo-00 13 Abstract 15 An IGP Flexible Algorithm computes a constraint-based path and maps 16 that path to an identifier. As currently defined, Flexalgo can only 17 map the paths that it computes to Segment Routing (SR) identifiers. 18 Therefore, Flexalgo cannot be deployed in the absence of SR. 20 This document extends Flexalgo, so that it can map the paths that it 21 computes to IP addresses. This allows Flexalgo to be deployed in any 22 IP network, even in the absence of SR. 24 Status of This Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at https://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on April 2, 2021. 41 Copyright Notice 43 Copyright (c) 2020 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (https://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 59 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 60 3. Egress Node Procedures . . . . . . . . . . . . . . . . . . . 3 61 4. Advertising Flexible Algorithm Definitions (FAD) . . . . . . 3 62 5. Advertising IP Reachability Using a Flexalgo . . . . . . . . 4 63 5.1. The ISIS IPv4 Flexalgo Prefix Reachability TLV . . . . . 4 64 5.2. The ISIS IPv6 Flexalgo Prefix Reachability TLV . . . . . 5 65 5.3. The ISIS MT IPv4 Flexalgo Prefix Reachability TLV . . . . 5 66 5.4. The ISIS MT IPv6 Flexalgo Prefix Reachability TLV . . . . 6 67 5.5. The OSPFv2 Flexalgo IP Prefix Opaque LSA . . . . . . . . 6 68 6. Advertising IGP Algorithm Support . . . . . . . . . . . . . . 8 69 6.1. The ISIS IGP Algorithm Sub-TLV . . . . . . . . . . . . . 8 70 6.2. The OSPFv2 IGP Algorithm TLV . . . . . . . . . . . . . . 9 71 7. Advertising Link Attributes . . . . . . . . . . . . . . . . . 10 72 8. Calculating Constraint-Based Paths . . . . . . . . . . . . . 10 73 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 74 10. Security Considerations . . . . . . . . . . . . . . . . . . . 11 75 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11 76 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 77 12.1. Normative References . . . . . . . . . . . . . . . . . . 11 78 12.2. Informative References . . . . . . . . . . . . . . . . . 13 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 81 1. Introduction 83 An IGP Flexible Algorithm (Flexalgo) [I-D.ietf-lsr-flex-algo]: 85 o Computes a constraint-based path to an egress node. 87 o Maps that path to an identifier. 89 As currently defined, Flexalgo can only map the paths that it 90 computes to: 92 o A Segment Routing (SR) [RFC8402] Segment Identifier (SID). 94 o An SRv6 [I-D.ietf-spring-srv6-network-programming] locator. 96 Therefore, Flexalgo cannot be deployed in the absence of SR and SRv6. 98 This document extends Flexalgo, allowing it to map the paths that it 99 computes to: 101 o An IPv4 [RFC0791] address. 103 o An IPv6 [RFC8200] address. 105 This allows Flexalgo to be deployed in any IP network, even in the 106 absence of SR and SRv6. 108 2. Requirements Language 110 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 111 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 112 "OPTIONAL" in this document are to be interpreted as described in BCP 113 14 [RFC2119] [RFC8174] when, and only when, they appear in all 114 capitals, as shown here. 116 3. Egress Node Procedures 118 Network operators configure multiple loopback interfaces on an egress 119 node. They can associate each loopback interface with: 121 o Zero or more IP addresses. 123 o Zero or one Flexible Algorithms. 125 If an IP address and a Flexible Algorithm are associated with the 126 same interface, they are also associated with one another. An IP 127 address MAY be associated with, at most, one interface. 129 If a packet is sent to a loopback address, and the loopback address 130 is not associated with a Flexible Algorithm, the packet follows the 131 IGP least-cost path to the egress node. If a packet is sent to a 132 loopback address, and the loopback address is associated with a 133 Flexible Algorithm, the packet follows the constraint-base path that 134 the Flexible Algorithm calculated. 136 4. Advertising Flexible Algorithm Definitions (FAD) 138 To guarantee loop free forwarding, all routers that participate in a 139 Flexible Algorithm MUST agree on the Flexible Algorithm Definition 140 (FAD). 142 Selected nodes within the IGP domain MUST advertise FADs as described 143 in Sections 5, 6 and 7 of [I-D.ietf-lsr-flex-algo]. 145 5. Advertising IP Reachability Using a Flexalgo 147 ISIS [ISO10589] nodes use the following TLVs to advertise prefix 148 reachability to prefixes that are associated with a Flexible 149 Algorithm. 151 o The IPv4 Flexalgo Prefix Reachability TLV 153 o The IPv6 Flexalgo Prefix Reachability TLV 155 o The MT IPv4 Flexalgo Prefix Reachability TLV 157 o The MT IPv6 Flexalgo Prefix Reachability TLV 159 OSPFv2 [RFC2328] nodes use the OSPFv2 Flexalgo IP Prefix Opaque LSA 160 to advertise prefix reachability to prefixes that are associated with 161 a Flexible Algorithm. 163 5.1. The ISIS IPv4 Flexalgo Prefix Reachability TLV 165 0 1 2 3 166 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 1 167 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 168 | Type | Length |U| Reserved |Flex-Algorithm | 169 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 170 | Metric | 171 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 172 | Prefix Len | Prefix ... 173 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 174 |Sub-TLV Len(*) | Sub-TLVs(*) ... 176 * - if present 178 Figure 1: The ISIS IPv4 Flexalgo Prefix Reachability TLV 180 Figure 1 represents the ISIS IPv4 Flexalgo Prefix Reachability TLV. 181 It contains the following fields: 183 o Type (8 bits): IPv4 Flexalgo Prefix Reachability TLV. Value TBD 184 by IANA. 186 o Length (8 bits) : TLV length. Measured in bytes. 188 o U (1 bit): Set indicates up. Clear indicates down. 190 o Reserved (7 bits): SHOULD be set to 0 by sender. MUST be ignored 191 by receiver. 193 o Flex-Algorithm (8 bits): Flexible Algorithm mapped to a prefix. 195 o Metric (32 bits): As described in [RFC5305]. 197 o Prefix Len (8 bits): Prefix length measured in bits. 199 o Prefix (variable length): Prefix mapped to Flexible Algorithm. 201 o Sub-TLV Len (8 bits): Optional. Sub-TLV length in bytes. 203 o Sub-TLVs (variable length): Optional 205 5.2. The ISIS IPv6 Flexalgo Prefix Reachability TLV 207 The ISIS IPv6 Flexalgo Prefix Reachability TLV is identical to the 208 ISIS IPv4 Flexalgo Prefix Reachability TLV except that it has a 209 unique type, The type is TBD by IANA. 211 5.3. The ISIS MT IPv4 Flexalgo Prefix Reachability TLV 213 0 1 2 3 214 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 1 215 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 216 | Type | Length | Reserved | MTID | 217 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 218 |Flex-Algorithm |U| Reserved | Metric .. | 219 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 220 | .. Metric | Prefix Len | Prefix ... 221 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 222 |Sub-TLV Len(*) | Sub-TLVs(*) ... 224 * - if present 226 Figure 2: The ISIS MT IPv4 Flexalgo Prefix Reachability TLV 228 Figure 2 represents the ISIS MT IPv4 Flexalgo Prefix Reachability 229 TLV. It contains the following fields: 231 o Type (8 bits): MT IPv4 Flexalgo Prefix Reachability TLV. Value 232 TBD by IANA. 234 o Length (8 bits) : TLV length. Measured in bytes. 236 o Reserved (8 bits): SHOULD be set to 0 by sender. MUST be ignored 237 by receiver. 239 o MTID: Multitopology Identifier as defined in [RFC5120]. Note that 240 the value 0 is legal. 242 o Flex-Algorithm (8 bits): Flexible Algorithm mapped to a prefix. 244 o U (1 bit): Set indicates up. Clear indicates down. 246 o Reserved (7 bits): SHOULD be set to 0 by sender. MUST be ignored 247 by receiver. 249 o Metric (32 bits): As described in [RFC5305]. 251 o Prefix Len (8 bits): Prefix length measured in bits. 253 o Prefix (variable length): Prefix mapped to Flexible Algorithm. 255 o Sub-TLV Len (8 bits): Optional. Sub-TLV length in bytes. 257 o Sub-TLVs (variable length): Optional 259 5.4. The ISIS MT IPv6 Flexalgo Prefix Reachability TLV 261 The ISIS MT IPv6 Flexalgo Prefix Reachability TLV is identical to the 262 ISIS MT IPv4 Flexalgo Prefix Reachability TLV except that it has a 263 unique type, The type is TBD by IANA. 265 5.5. The OSPFv2 Flexalgo IP Prefix Opaque LSA 267 The Flexalgo IP Prefix Opaque LSA begins with the standard LSA header 268 (Figure 3). It contains the OSPFv2 Flexalgo IP Prefix TLV 269 (Figure 4). 271 0 1 2 3 272 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 1 273 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 274 | LS age | Options | 10 or 11 | 275 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 276 | 11 | 0 | 277 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 278 | Advertising Router | 279 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 280 | LS sequence number | 281 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 282 | LS checksum | length | 283 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 284 | | 285 +- TLVs -+ 286 | ... | 288 Figure 3: Standard LSA Header 290 0 1 2 3 291 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 1 292 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 293 | Type(1) | Length | 294 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 295 | Reserved | Prefix Length | MT-ID |Flex-Algorithm | 296 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 297 | Metric | 298 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 299 | Prefix (variable) | 300 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 301 | Sub-TLVs (variable) | 302 +- -+ 303 | ... | 305 Figure 4: OSPFv2 Flexalgo IP Prefix TLV 307 Figure 4 represents the OSPFv2 Flexalgo IP Prefix TLV. It contains 308 the following fields: 310 o Type (8 bits): MT IPv4 Flexalgo Prefix Reachability TLV. Value 311 TBD by IANA. 313 o Length (8 bits) : TLV length. Measured in bytes. 315 o Reserved (8 bits): SHOULD be set to 0 by sender. MUST be ignored 316 by receiver. 318 o Prefix Len (8 bits): Prefix length measured in bits. 320 o MTID: Multitopology Identifier as defined in [RFC4915]. Note that 321 the value 0 is legal. 323 o Flex-Algorithm (8 bits): Flexible Algorithm mapped to a prefix. 325 o Metric (32 bits): As described in [RFC3630]. 327 o Prefix (variable length): Prefix mapped to Flexible Algorithm. 329 o Sub-TLVs (variable length): Optional 331 6. Advertising IGP Algorithm Support 333 A node may use various algorithms when calculating paths. Algorithm 334 values are defined in the IGP Algorithm Type Registry [IANA-ALG]. 335 The following values have been defined: 337 1. SPF algorithm based on link metric. This is the well-known 338 shortest path algorithm as computed by the IS-IS Decision 339 Process. Consistent with the deployed practice for link-state 340 protocols, algorithm 0 permits any node to overwrite the SPF path 341 with a different path based on local policy. 343 2. Strict SPF algorithm based on link metric. The algorithm is 344 identical to algorithm 0, but algorithm 1 requires that all nodes 345 along the path will honor the SPF routing decision. Local policy 346 MUST NOT alter the forwarding decision computed by algorithm 1 at 347 the node claiming to support algorithm 1. 349 ISIS and OSPFv2 use an IGP Algorithm TLV or sub-TLV to advertise IGP 350 Algorithms that they support. 352 6.1. The ISIS IGP Algorithm Sub-TLV 354 The IGP Algorithm Sub-TLV is advertised in the ISIS Router Capability 355 TLV. The Router Capability TLV specifies flags that control its 356 advertisement. The IGP Algorithm MUST be propagated throughout the 357 level and MUST NOT be advertised across level boundaries. Therefore, 358 Router Capability TLV distribution flags are set accordingly, i.e., 359 the S-Flag MUST NOT be set. 361 The IGP Algorithm sub-TLV is optional. It MUST NOT be advertised 362 more than once at a given level. A router receiving multiple IGP 363 Algorithm sub-TLVs from the same originator SHOULD select the first 364 advertisement in the lowest-numbered LSP. 366 When the originating router does not advertise the IGP Algorithm sub- 367 TLV, it implies that algorithm 0 is the only algorithm supported by 368 the routers that support the extensions defined in this document. 370 When the originating router does advertise the IGP Algorithm sub-TLV, 371 then algorithm 0 MUST be present while non-zero algorithms MAY be 372 present. 374 0 1 2 3 375 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 1 376 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 377 | Type | Length | 378 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 379 | Algorithm 1 | Algorithm 2 | Algorithm ... | Algorithm n | 380 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 382 Figure 5: ISIS IGP Algorithm Sub-TLV 384 Figure 5 depicts the IGP Algorithm Sub-TLV where: 386 o Type: IGP Algorithm (Value TBD by IANA) 388 o Length: Variable 390 o Algorithm: 1 octet of algorithm. 392 6.2. The OSPFv2 IGP Algorithm TLV 394 The IGP Algorithm TLV is a top-level TLV of the Router Information 395 Opaque LSA [RFC7770]. 397 The IGP Algorithm TLV is optional. It SHOULD only be advertised once 398 in the Router Information Opaque LSA. If the IGP Algorithm TLV is 399 not advertised by the node, the node is assumed to support algorithm 400 0 only. 402 When multiple IGP Algorithm TLVs are received from a given router, 403 the receiver MUST use the first occurrence of the TLV in the Router 404 Information Opaque LSA. If the IGP Algorithm TLV appears in multiple 405 Router Information Opaque LSAs that have different flooding scopes, 406 the IGP Algorithm TLV in the Router Information Opaque LSA with the 407 area-scoped flooding scope MUST be used. If the IGP Algorithm TLV 408 appears in multiple Router Information Opaque LSAs that have the same 409 flooding scope, the IGP Algorithm TLV in the Router Information (RI) 410 Opaque LSA with the numerically smallest Instance ID MUST be used and 411 subsequent instances of the IGP Algorithm TLV MUST be ignored. 413 The RI LSA can be advertised at any of the defined opaque flooding 414 scopes (link, area, or Autonomous System (AS)). For the purpose of 415 IGP Algorithm TLV advertisement, area-scoped flooding is REQUIRED. 417 0 1 2 3 418 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 1 419 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 420 | Type | Length | 421 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 422 | Algorithm 1 | Algorithm... | Algorithm n | | 423 +- -+ 424 | | 425 + + 427 Figure 6: OSPFv2 IGP Algorithm TLV 429 Figure 6 depicts the IGP Algorithm TLV where: 431 o Type: IGP Algorithm (Value TBD by IANA) 433 o Length: Variable 435 o Algorithm: 1 octet of algorithm. 437 7. Advertising Link Attributes 439 Various link attributes may be used during the Flex-Algorithm path 440 calculation. Section 12 of [I-D.ietf-lsr-flex-algo] describes link 441 advertisement procedures. 443 8. Calculating Constraint-Based Paths 445 Nodes calculate constraint-based paths as described in Section 12 of 446 [I-D.ietf-lsr-flex-algo]. 448 9. IANA Considerations 450 This specification updates the OSPF Router Information (RI) TLVs 451 Registry as follows: 453 +-------+---------------+---------------+ 454 | Value | TLV Name | Reference | 455 +-------+---------------+---------------+ 456 | TBD | IGP Algorithm | This Document | 457 +-------+---------------+---------------+ 459 This document also updates the "Sub-TLVs for TLV 242" registry as 460 follows: 462 +-------+---------------+---------------+ 463 | Value | TLV Name | Reference | 464 +-------+---------------+---------------+ 465 | TBD | IGP Algorithm | This Document | 466 +-------+---------------+---------------+ 468 This document also updates the "ISIS TLV Codepoints Registry" 469 registry as follows: 471 +-------+------------------------------------------+---------------+ 472 | Value | TLV Name | Reference | 473 +-------+------------------------------------------+---------------+ 474 | TBD | IPv4 Flexalgo Prefix Reachability TLV | This document | 475 | TBD | IPv6 Flexalgo Prefix Reachability TLV | This document | 476 | TBD | MT IPv4 Flexalgo Prefix Reachability TLV | This document | 477 | TBD | MT IPv6 Flexalgo Prefix Reachability TLV | This document | 478 +-------+------------------------------------------+---------------+ 480 This document updates the "Opaque Link-State Advertisements (LSA) 481 Option Types" registry as follows:: 483 +-------+---------------------------------------+---------------+ 484 | Value | TLV Name | Reference | 485 +-------+---------------------------------------+---------------+ 486 | TBD | OSPFvv2 Flexalgo IP Prefix Opaque LSA | This Document | 487 +-------+---------------------------------------+---------------+ 489 10. Security Considerations 491 TBD 493 11. Acknowledgements 495 TBD. 497 12. References 499 12.1. Normative References 501 [I-D.ietf-lsr-flex-algo] 502 Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and 503 A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex- 504 algo-11 (work in progress), September 2020. 506 [ISO10589] 507 IANA, "Intermediate system to Intermediate system routing 508 information exchange protocol for use in conjunction with 509 the Protocol for providing the Connectionless-mode Network 510 Service (ISO 8473)", August 1987, . 512 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 513 DOI 10.17487/RFC0791, September 1981, 514 . 516 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 517 Requirement Levels", BCP 14, RFC 2119, 518 DOI 10.17487/RFC2119, March 1997, 519 . 521 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 522 DOI 10.17487/RFC2328, April 1998, 523 . 525 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 526 (TE) Extensions to OSPF Version 2", RFC 3630, 527 DOI 10.17487/RFC3630, September 2003, 528 . 530 [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. 531 Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", 532 RFC 4915, DOI 10.17487/RFC4915, June 2007, 533 . 535 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 536 Topology (MT) Routing in Intermediate System to 537 Intermediate Systems (IS-ISs)", RFC 5120, 538 DOI 10.17487/RFC5120, February 2008, 539 . 541 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 542 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 543 2008, . 545 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 546 for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, 547 . 549 [RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and 550 S. Shaffer, "Extensions to OSPF for Advertising Optional 551 Router Capabilities", RFC 7770, DOI 10.17487/RFC7770, 552 February 2016, . 554 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 555 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 556 May 2017, . 558 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 559 (IPv6) Specification", STD 86, RFC 8200, 560 DOI 10.17487/RFC8200, July 2017, 561 . 563 12.2. Informative References 565 [I-D.ietf-spring-srv6-network-programming] 566 Filsfils, C., Camarillo, P., Leddy, J., Voyer, D., 567 Matsushima, S., and Z. Li, "SRv6 Network Programming", 568 draft-ietf-spring-srv6-network-programming-20 (work in 569 progress), September 2020. 571 [IANA-ALG] 572 IANA, "Sub-TLVs for TLV 242 (IS-IS Router CAPABILITY 573 TLV)", August 1987, . 576 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 577 Decraene, B., Litkowski, S., and R. Shakir, "Segment 578 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 579 July 2018, . 581 Authors' Addresses 583 William Britto 584 Juniper Networks 585 Elnath-Exora Business Park Survey 586 Bangalore, Karnataka 560103 587 India 589 Email: bwilliam@juniper.net 591 Shraddha Hegde 592 Juniper Networks 593 Elnath-Exora Business Park Survey 594 Bangalore, Karnataka 560103 595 India 597 Email: shraddha@juniper.net 598 Parag Kaneriya 599 Juniper Networks 600 Elnath-Exora Business Park Survey 601 Bangalore, Karnataka 560103 602 India 604 Email: pkaneria@juniper.net 606 Rejesh Shetty 607 Juniper Networks 608 Elnath-Exora Business Park Survey 609 Bangalore, Karnataka 560103 610 India 612 Email: mrajesh@juniper.net 614 Ron Bonica 615 Juniper Networks 616 2251 Corporate Park Drive 617 Herndon, Virginia 20171 618 USA 620 Email: rbonica@juniper.net