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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group P. Psenak 3 Internet-Draft A. Lindem 4 Intended status: Standards Track L. Ginsberg 5 Expires: April 30, 2018 Cisco Systems 6 W. Henderickx 7 Nokia 8 J. Tantsura 9 Individual 10 H. Gredler 11 RtBrick Inc. 12 J. Drake 13 Juniper Networks 14 October 27, 2017 16 OSPFv2 Link Traffic Engineering (TE) Attribute Reuse 17 draft-ietf-ospf-te-link-attr-reuse-02.txt 19 Abstract 21 Various link attributes have been defined in OSPFv2 in the context of 22 the MPLS Traffic Engineering (TE) and GMPLS. Many of these link 23 attributes can be used for purposes other than MPLS Traffic 24 Engineering or GMPLS. This documents defines how to distribute such 25 attributes in OSPFv2 for applications other than MPLS Traffic 26 Engineering or GMPLS purposes. 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 30, 2018. 45 Copyright Notice 47 Copyright (c) 2017 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 This document may contain material from IETF Documents or IETF 61 Contributions published or made publicly available before November 62 10, 2008. The person(s) controlling the copyright in some of this 63 material may not have granted the IETF Trust the right to allow 64 modifications of such material outside the IETF Standards Process. 65 Without obtaining an adequate license from the person(s) controlling 66 the copyright in such materials, this document may not be modified 67 outside the IETF Standards Process, and derivative works of it may 68 not be created outside the IETF Standards Process, except to format 69 it for publication as an RFC or to translate it into languages other 70 than English. 72 Table of Contents 74 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 75 1.1. Requirements notation . . . . . . . . . . . . . . . . . . 3 76 2. Link attributes examples . . . . . . . . . . . . . . . . . . 3 77 3. Advertising Link Attributes . . . . . . . . . . . . . . . . . 4 78 3.1. TE Opaque LSA . . . . . . . . . . . . . . . . . . . . . . 4 79 3.2. Extended Link Opaque LSA . . . . . . . . . . . . . . . . 5 80 3.3. Selected Approach . . . . . . . . . . . . . . . . . . . . 5 81 4. Reused TE link attributes . . . . . . . . . . . . . . . . . . 6 82 4.1. Shared Risk Link Group (SRLG) . . . . . . . . . . . . . . 6 83 4.2. Extended Metrics . . . . . . . . . . . . . . . . . . . . 6 84 4.3. Administrative Group . . . . . . . . . . . . . . . . . . 7 85 5. Advertisement of Application Specific Values . . . . . . . . 7 86 6. Deployment Considerations . . . . . . . . . . . . . . . . . . 10 87 7. Attribute Advertisements and Enablement . . . . . . . . . . . 10 88 8. Backward Compatibility . . . . . . . . . . . . . . . . . . . 11 89 9. Security Considerations . . . . . . . . . . . . . . . . . . . 12 90 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 91 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12 92 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 93 12.1. Normative References . . . . . . . . . . . . . . . . . . 12 94 12.2. Informative References . . . . . . . . . . . . . . . . . 13 95 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 97 1. Introduction 99 Various link attributes have been defined in OSPFv2 [RFC2328] in the 100 context of the MPLS traffic engineering and GMPLS. All these 101 attributes are distributed by OSPFv2 as sub-TLVs of the Link-TLV 102 advertised in the OSPFv2 TE Opaque LSA [RFC3630]. 104 Many of these link attributes are useful outside of the traditional 105 MPLS Traffic Engineering or GMPLS. This brings its own set of 106 problems, in particular how to distribute these link attributes in 107 OSPFv2 when MPLS TE or GMPLS are not deployed or are deployed in 108 parallel with other applications that use these link attributes. 110 [RFC7855] discusses use cases/requirements for SR. Included among 111 these use cases is SRTE. If both RSVP-TE and SRTE are deployed in a 112 network, link attribute advertisements can be used by one or both of 113 these applications. As there is no requirement for the link 114 attributes advertised on a given link used by SRTE to be identical to 115 the link attributes advertised on that same link used by RSVP-TE, 116 there is a clear requirement to indicate independently which link 117 attribute advertisements are to be used by each application. 119 As the number of applications which may wish to utilize link 120 attributes may grow in the future, an additional requirement is that 121 the extensions defined allow the association of additional 122 applications to link attributes without altering the format of the 123 advertisements or introducing new backwards compatibility issues. 125 Finally, there may still be many cases where a single attribute value 126 can be shared among multiple applications, so the solution should 127 minimize advertising duplicate link/attribute when possible. 129 1.1. Requirements notation 131 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 132 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 133 document are to be interpreted as described in [RFC2119]. 135 2. Link attributes examples 137 This section lists some of the link attributes originally defined for 138 MPLS Traffic Engineering that can be used for other purposes in 139 OSPFv2. The list doesn't necessarily contain all the required 140 attributes. 142 1. Remote Interface IP address [RFC3630] - OSPFv2 currently cannot 143 distinguish between parallel links between two OSPFv2 routers. 144 As a result, the two-way connectivity check performed during SPF 145 may succeed when the two routers disagree on which of the links 146 to use for data traffic. 148 2. Link Local/Remote Identifiers - [RFC4203] - Used for the two-way 149 connectivity check for parallel unnumbered links. Also used for 150 identifying adjacencies for unnumbered links in Segment Routing 151 traffic engineering. 153 3. Shared Risk Link Group (SRLG) [RFC4203] - In IPFRR, the SRLG is 154 used to compute diverse backup paths [RFC5714]. 156 4. Unidirectional Link Delay/Loss Metrics [RFC7471] - Could be used 157 for the shortest path first (SPF) computation using alternate 158 metrics within an OSPF area. 160 3. Advertising Link Attributes 162 This section outlines possible approaches for advertising link 163 attributes originally defined for MPLS Traffic Engineering purposes 164 or GMPLS when they are used for other applications. 166 3.1. TE Opaque LSA 168 One approach for advertising link attributes is to continue to use TE 169 Opaque LSA ([RFC3630]). There are several problems with this 170 approach: 172 1. Whenever the link is advertised in a TE Opaque LSA, the link 173 becomes a part of the TE topology, which may not match IP routed 174 topology. By making the link part of the TE topology, remote 175 nodes may mistakenly believe that the link is available for MPLS 176 TE or GMPLS, when, in fact, MPLS is not enabled on the link. 178 2. The TE Opaque LSA carries link attributes that are not used or 179 required by MPLS TE or GMPLS. There is no mechanism in a TE 180 Opaque LSA to indicate which of the link attributes are passed to 181 MPLS TE application and which are used by other applications 182 including OSPFv2 itself. 184 3. Link attributes used for non-TE purposes are partitioned across 185 multiple LSAs - the TE Opaque LSA and the Extended Link Opaque 186 LSA. This partitioning will require implementations to lookup 187 multiple LSAs to extract link attributes for a single link, 188 bringing needless complexity to OSPFv2 implementations. 190 The advantage of this approach is that there is no additional 191 standardization requirement to advertise the TE/GMPL attributes for 192 other applications. Additionally, link attributes are only 193 advertised once when both OSPF TE and other applications are deployed 194 on the same link. This is not expected to be a common deployment 195 scenario. 197 3.2. Extended Link Opaque LSA 199 An alternative approach for advertising link attributes is to use 200 Extended Link Opaque LSAs as defined in [RFC7684]. This LSA was 201 defined as a generic container for distribution of the extended link 202 attributes. There are several advantages in using Extended Link LSA: 204 1. Advertisement of the link attributes does not make the link part 205 of the TE topology. It avoids any conflicts and is fully 206 compatible with the [RFC3630]. 208 2. The TE Opaque LSA remains truly opaque to OSPFv2 as originally 209 defined in [RFC3630]. Its content is not inspected by OSPFv2 and 210 OSPFv2 acts as a pure transport. 212 3. There is clear distinction between link attributes used by TE and 213 link attributes used by other OSPFv2 applications. 215 4. All link attributes that are used by OSPFv2 applications are 216 advertised in a single LSA, the Extended Link Opaque LSA. 218 The disadvantage of this approach is that in rare cases, the same 219 link attribute is advertised in both the TE Opaque and Extended Link 220 Attribute LSAs. Additionally, there will be additional 221 standardization effort. However, this could also be viewed as an 222 advantage as the non-TE use cases for the TE link attributes are 223 documented and validated by the OSPF working group. 225 3.3. Selected Approach 227 It is RECOMMENDED to use the Extended Link Opaque LSA ([RFC7684] to 228 advertise any link attributes used for non-TE purposes in OSPFv2, 229 including those that have been originally defined for TE purposes. 230 TE link attributes used for TE purposes continue to use TE Opaque LSA 231 ([RFC3630]). 233 It is also RECOMMENDED to keep the format of the link attribute TLVs 234 that have been defined for TE purposes unchanged even when they are 235 used for non-TE purposes. 237 Finally, it is RECOMMENDED to allocate unique code points for link 238 attribute TLVs that have been defined for TE purposes for the OSPFv2 239 Extended Link TLV Sub-TLV Registry as defined in [RFC7684]. For each 240 reused TLV, the code point will be defined in an IETF document along 241 with the expected usecase(s). 243 4. Reused TE link attributes 245 This section defines the use case and code points for the OSPFv2 246 Extended Link TLV Sub-TLV Registry for some of the link attributes 247 that have been originally defined for TE or GMPLS purposes. 249 Remote interface IP address and Link Local/Remote Identifiers have 250 been added as sub-TLVs of OSPFv2 Extended Link TLV by 251 [I-D.ietf-ospf-link-overload]. 253 4.1. Shared Risk Link Group (SRLG) 255 The SRLG of a link can be used in IPFRR to compute a backup path that 256 does not share any SRLG group with the protected link. 258 To advertise the SRLG of the link in the OSPFv2 Extended Link TLV, 259 the same format of the sub-TLV as defined in section 1.3. of 260 [RFC4203] is used and TLV type TBD1 is used. 262 4.2. Extended Metrics 264 [RFC3630] defines several link bandwidth types. [RFC7471] defines 265 extended link metrics that are based on link bandwidth, delay and 266 loss characteristics. All these can be used to compute best paths 267 within an OSPF area to satisfy requirements for bandwidth, delay 268 (nominal or worst case) or loss. 270 To advertise extended link metrics in the OSPFv2 Extended Link TLV, 271 the same format of the sub-TLVs as defined in [RFC7471] is used with 272 following TLV types: 274 TBD2 - Unidirectional Link Delay 276 TBD3 - Min/Max Unidirectional Link Delay 278 TBD4 - Unidirectional Delay Variation 280 TBD5 - Unidirectional Link Loss 282 TBD6 - Unidirectional Residual Bandwidth 284 TBD7 - Unidirectional Available Bandwidth 285 TBD8 - Unidirectional Utilized Bandwidth 287 4.3. Administrative Group 289 [RFC3630] and [RFC7308] define Administrative Group and Extended 290 Administrative Group sub-TLVs. 292 One use case where advertisement of the Extended Administrative 293 Group(s) for a link is required is described in 294 [I-D.hegdeppsenak-isis-sr-flex-algo]. 296 To advertise Administrative Group and Extended Administrative Group 297 in the OSPFv2 Extended Link TLV, the same format of the sub-TLVs as 298 defined in [RFC3630] and [RFC7308] is used with following TLV types: 300 TBD9 - Administrative Group 302 TBD10 - Extended Administrative Group 304 5. Advertisement of Application Specific Values 306 Multiple applications can utilize link attributes that are flooded by 307 OSPFv2. Some examples of applications using the link attributes are 308 Segment Routing Traffic Engineering and LFA [RFC5286]. 310 In some cases the link attribute only has a single value that is 311 applicable to all applications. An example is a Remote interface IP 312 address or Link Local/Remote Identifiers 313 [I-D.ietf-ospf-link-overload]. 315 In some cases the link attribute MAY have different values for 316 different applications. An example could be SRLG [Section 4.1], 317 where values used by LFA could be different then the values used by 318 Segment Routing Traffic Engineering. 320 To allow advertisement of the application specific values of the link 321 attribute, a new Extended Link Attribute sub-TLV of the Extended Link 322 TLV [RFC7471] is defined. The Extended Link Attribute sub-TLV is an 323 optional sub-TLV and can appear multiple times in the Extended Link 324 TLV. It has following format: 326 0 1 2 3 327 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 1 328 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 329 | Type | Length | 330 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 331 | SABML | UDABML | Reserved | 332 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 333 | Standard Application Bit-Mask | 334 +- -+ 335 | ... | 336 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 337 | User Defined Application Bit-Mask | 338 +- -+ 339 | ... | 340 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 341 | Link Attribute sub-sub-TLVs | 342 +- -+ 343 | ... | 345 where: 347 Type: TBD11, suggested value 8 349 Length: variable 351 SABML: Standard Application Bit-Mask Length. If the Standard 352 Application Bit-Mask is not present, the Standard Application Bit- 353 Mask Length MUST be set to 0. 355 UDABML: User Defined Application Bit-Mask Length. If the User 356 Defined Application Bit-Mask is not present, the User Defined 357 Application Bit-Mask Length MUST be set to 0. 359 Standard Application Bit-Mask: Optional set of bits, where each 360 bit represents a single standard application. The following bits 361 are defined by this document: 363 Bit-0: RSVP Traffic Engineering 365 Bit-1: Segment Routing Traffic Engineering 367 Bit-2: Loop Free Alternate (LFA). Includes all LFA types. 369 Bit-3: Flexible Algorithm as describe in 370 [I-D.hegdeppsenak-isis-sr-flex-algo]. 372 User Defined Application Bit-Mask: Optional set of bits, where 373 each bit represents a single user defined application. 375 Standard Application Bits are defined/sent starting with Bit 0. 376 Additional bit definitions that may be defined in the future SHOULD 377 be assigned in ascending bit order so as to minimize the number of 378 octets that will need to be transmitted. 380 User Defined Application bits have no relationship to Standard 381 Application bits and are NOT managed by IANA or any other standards 382 body. It is recommended that bits are used starting with Bit 0 so as 383 to minimize the number of octets required to advertise all of them. 385 Undefined bits in both Bit-Masks MUST be transmitted as 0 and MUST be 386 ignored on receipt. Bits that are NOT transmitted MUST be treated as 387 if they are set to 0 on receipt. 389 If the link attribute advertisement is limited to be used by a 390 specific set of applications, corresponding Bit-Masks MUST be present 391 and application specific bit(s) MUST be set for all applications that 392 use the link attributes advertised in the Extended Link Attribute 393 sub-TLV. 395 Application Bit-Masks apply to all link attributes that support 396 application specific values and are advertised in the Extended Link 397 Attribute sub-TLV. 399 The advantage of not making the Application Bit-Masks part of the 400 attribute advertisement itself is that we can keep the format of the 401 link attributes that have been defined previously and reuse the same 402 format when advertising them in the Extended Link Attribute sub-TLV. 404 If the link attribute is advertised and there is no Application Bit- 405 Mask present in the Extended Link Attribute Sub-TLV, the link 406 attribute advertisement MAY be used by any application. If, however, 407 another advertisement of the same link attribute includes any 408 Application Bit-Mask in the Extended Link Attribute sub-TLV, 409 applications that are listed in the Application Bit-Masks of such 410 Extended Link Attribute sub-TLV SHOULD use the attribute 411 advertisement which has the application specific bit set in the 412 Application Bit-Masks. 414 If the same application is listed in the Application Bit-Masks of 415 more then one Extended Link Attribute sub-TLV, the application SHOULD 416 use the first advertisement and ignore any subsequent advertisements 417 of the same attribute. This situation SHOULD be logged as an error. 419 This document defines the set of link attributes for which the 420 Application Bit-Masks may be advertised. If any of the Application 421 Bit-Masks is included in the Extended Link Attribute sub-TLV that 422 advertises any link attribute(s) NOT listed below, the Application 423 Bit-Masks MUST NOT be used for such link attribute(s). It MUST be 424 used for those attribute(s) that support application specific values. 425 Documents which define new link attributes MUST state whether the new 426 attributes support application specific values. The link attributes 427 to which the Application Bit-Masks may apply are: 429 - Shared Risk Link Group 431 - Unidirectional Link Delay 433 - Min/Max Unidirectional Link Delay 435 - Unidirectional Delay Variation 437 - Unidirectional Link Loss 439 - Unidirectional Residual Bandwidth 441 - Unidirectional Available Bandwidth 443 - Unidirectional Utilized Bandwidth 445 - Administrative Group 447 - Extended Administrative Group 449 6. Deployment Considerations 451 If link attributes are advertised associated with zero length 452 application bit masks for both standard applications and user defined 453 applications, then that set of link attributes MAY be used by any 454 application. If support for a new application is introduced on any 455 node in a network in the presence of such advertisements, these 456 advertisements MAY be used by the new application. If this is not 457 what is intended, then existing advertisements MUST be readvertised 458 with an explicit set of applications specified before a new 459 application is introduced. 461 7. Attribute Advertisements and Enablement 463 This document defines extensions to support the advertisement of 464 application specific link attributes. 466 Whether the presence of link attribute advertisements for a given 467 application indicates that the application is enabled on that link 468 depends upon the application. Similarly, whether the absence of link 469 attribute advertisements indicates that the application is not 470 enabled depends upon the application. 472 In the case of RSVP-TE, the advertisement of application specific 473 link attributes implies that RSVP is enabled on that link. 475 In the case of SRTE, advertisement of application specific link 476 attributes does NOT indicate enablement of SRTE. The advertisements 477 are only used to support constraints which may be applied when 478 specifying an explicit path. SRTE is implicitly enabled on all links 479 which are part of the Segment Routing enabled topology independent of 480 the existence of link attribute advertisements. 482 In the case of LFA, advertisement of application specific link 483 attributes does NOT indicate enablement of LFA on that link. 484 Enablement is controlled by local configuration. 486 In the case of Flexible Algorithm, advertisement of application 487 specific link attributes does NOT indicate enablement of Flexible 488 Algorithm on that link. Rather the attributes are used to determine 489 what links are included/excluded in the algorithm specific 490 constrained SPF. This is fully specified in 491 [I-D.hegdeppsenak-isis-sr-flex-algo]. 493 If, in the future, additional standard applications are defined to 494 use this mechanism, the specification defining this use MUST define 495 the relationship between application specific link attribute 496 advertisements and enablement for that application. 498 8. Backward Compatibility 500 Link attributes may be concurrently advertised in both the TE Opaque 501 LSA [RFC3630] and the Extended Link Opaque LSA [RFC7684]. 503 In fact, there is at least one OSPF implementation that utilizes the 504 link attributes advertised in TE Opaque LSAs [RFC3630] for Non-RSVP 505 TE applications. For example, this implementation of LFA and remote 506 LFA utilizes links attributes such as Shared Risk Link Groups (SRLG) 507 [RFC4203] and Admin Group [[RFC3630]advertised in TE Opaque LSAs. 508 These applications are described in [RFC5286], [RFC7490], 509 [I-D.ietf-rtgwg-lfa-manageability] and 510 [I-D.psarkar-rtgwg-rlfa-node-protection]. 512 When an OSPF routing domain includes routers using link attributes 513 from TE Opaque LSAs for Non-RSVP TE applications such as LFA, OSPF 514 routers in that domain should continue to advertise such TE Opaque 515 LSAs. If there are also OSPF routers using the link attributes 516 described herein for any application, OSPF routers in the routing 517 domain will also need to advertise these attributes in OSPF Extended 518 Link Attributes LSAs [RFC7684]. In such a deployment, the advertised 519 attributes SHOULD be the same and Non-RSVP application access to link 520 attributes is a matter of local policy. 522 9. Security Considerations 524 Implementations must assure that malformed TLV and Sub-TLV 525 permutations do not result in errors that cause hard OSPFv2 failures. 527 10. IANA Considerations 529 OSPFv2 Extended Link TLV Sub-TLVs registry [RFC7684] defines sub-TLVs 530 at any level of nesting for OSPFv2 Extended Link TLVs. This 531 specification updates OSPFv2 Extended Link TLV sub-TLVs registry with 532 the following TLV types: 534 TBD1 (9 Recommended) - Shared Risk Link Group 536 TBD2 (10 Recommended) - Unidirectional Link Delay 538 TBD3 (11 Recommended) - Min/Max Unidirectional Link Delay 540 TBD4 (12 Recommended) - Unidirectional Delay Variation 542 TBD5 (13 Recommended) - Unidirectional Link Loss 544 TBD6 (14 Recommended) - Unidirectional Residual Bandwidth 546 TBD7 (15 Recommended) - Unidirectional Available Bandwidth 548 TBD8 (16 Recommended) - Unidirectional Utilized Bandwidth 550 TBD9 (17 Recommended) - Administrative Group 552 TBD10 (18 Recommended) - Extended Administrative Group 554 TBD11 (8 Recommended) - Extended Link Attribute 556 11. Acknowledgments 558 Thanks to Chris Bowers for his review and comments. 560 12. References 562 12.1. Normative References 564 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 565 Requirement Levels", BCP 14, RFC 2119, 566 DOI 10.17487/RFC2119, March 1997, 567 . 569 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 570 (TE) Extensions to OSPF Version 2", RFC 3630, 571 DOI 10.17487/RFC3630, September 2003, 572 . 574 [RFC5714] Shand, M. and S. Bryant, "IP Fast Reroute Framework", 575 RFC 5714, DOI 10.17487/RFC5714, January 2010, 576 . 578 [RFC7308] Osborne, E., "Extended Administrative Groups in MPLS 579 Traffic Engineering (MPLS-TE)", RFC 7308, 580 DOI 10.17487/RFC7308, July 2014, 581 . 583 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 584 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 585 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 586 2015, . 588 12.2. Informative References 590 [I-D.hegdeppsenak-isis-sr-flex-algo] 591 Psenak, P., Hegde, S., Filsfils, C., and a. 592 arkadiy.gulko@thomsonreuters.com, "ISIS Segment Routing 593 Flexible Algorithm", draft-hegdeppsenak-isis-sr-flex- 594 algo-01 (work in progress), October 2017. 596 [I-D.ietf-idr-ls-distribution] 597 Gredler, H., Medved, J., Previdi, S., Farrel, A., and S. 598 Ray, "North-Bound Distribution of Link-State and TE 599 Information using BGP", draft-ietf-idr-ls-distribution-13 600 (work in progress), October 2015. 602 [I-D.ietf-ospf-link-overload] 603 Hegde, S., Sarkar, P., Gredler, H., Nanduri, M., and L. 604 Jalil, "OSPF Link Overload", draft-ietf-ospf-link- 605 overload-09 (work in progress), August 2017. 607 [I-D.ietf-ospf-segment-routing-extensions] 608 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., 609 Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 610 Extensions for Segment Routing", draft-ietf-ospf-segment- 611 routing-extensions-21 (work in progress), October 2017. 613 [I-D.ietf-rtgwg-lfa-manageability] 614 Litkowski, S., Decraene, B., Filsfils, C., Raza, K., and 615 M. Horneffer, "Operational management of Loop Free 616 Alternates", draft-ietf-rtgwg-lfa-manageability-11 (work 617 in progress), June 2015. 619 [I-D.psarkar-rtgwg-rlfa-node-protection] 620 psarkar@juniper.net, p., Gredler, H., Hegde, S., Bowers, 621 C., Litkowski, S., and H. Raghuveer, "Remote-LFA Node 622 Protection and Manageability", draft-psarkar-rtgwg-rlfa- 623 node-protection-05 (work in progress), June 2014. 625 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 626 DOI 10.17487/RFC2328, April 1998, 627 . 629 [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in 630 Support of Generalized Multi-Protocol Label Switching 631 (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005, 632 . 634 [RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for 635 IP Fast Reroute: Loop-Free Alternates", RFC 5286, 636 DOI 10.17487/RFC5286, September 2008, 637 . 639 [RFC7471] Giacalone, S., Ward, D., Drake, J., Atlas, A., and S. 640 Previdi, "OSPF Traffic Engineering (TE) Metric 641 Extensions", RFC 7471, DOI 10.17487/RFC7471, March 2015, 642 . 644 [RFC7490] Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N. 645 So, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)", 646 RFC 7490, DOI 10.17487/RFC7490, April 2015, 647 . 649 [RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B., 650 Litkowski, S., Horneffer, M., and R. Shakir, "Source 651 Packet Routing in Networking (SPRING) Problem Statement 652 and Requirements", RFC 7855, DOI 10.17487/RFC7855, May 653 2016, . 655 Authors' Addresses 656 Peter Psenak 657 Cisco Systems 658 Apollo Business Center 659 Mlynske nivy 43 660 Bratislava, 821 09 661 Slovakia 663 Email: ppsenak@cisco.com 665 Acee Lindem 666 Cisco Systems 667 301 Midenhall Way 668 Cary, NC 27513 669 USA 671 Email: acee@cisco.com 673 Les Ginsberg 674 Cisco Systems 675 821 Alder Drive 676 MILPITAS, CA 95035 677 USA 679 Email: ginsberg@cisco.com 681 Wim Henderickx 682 Nokia 683 Copernicuslaan 50 684 Antwerp, 2018 94089 685 Belgium 687 Email: wim.henderickx@nokia.com 689 Jeff Tantsura 690 Individual 691 USA 693 Email: jefftant.ietf@gmail.com 695 Hannes Gredler 696 RtBrick Inc. 698 Email: hannes@rtbrick.com 699 John Drake 700 Juniper Networks 702 Email: jdrake@juniper.net