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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, Inc. 4 Intended status: Standards Track A. Lindem 5 Expires: August 3, 2018 L. Ginsberg 6 Cisco Systems 7 W. Henderickx 8 Nokia 9 J. Tantsura 10 Nuage Networks 11 H. Gredler 12 RtBrick Inc. 13 J. Drake 14 Juniper Networks 15 January 30, 2018 17 OSPFv2 Link Traffic Engineering (TE) Attribute Reuse 18 draft-ietf-ospf-te-link-attr-reuse-03.txt 20 Abstract 22 Various link attributes have been defined in OSPFv2 in the context of 23 the MPLS Traffic Engineering (TE) and GMPLS. Many of these link 24 attributes can be used for purposes other than MPLS Traffic 25 Engineering or GMPLS. This documents defines how to distribute such 26 attributes in OSPFv2 for applications other than MPLS Traffic 27 Engineering or GMPLS purposes. 29 Status of This Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at https://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on August 3, 2018. 46 Copyright Notice 48 Copyright (c) 2018 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (https://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 This document may contain material from IETF Documents or IETF 62 Contributions published or made publicly available before November 63 10, 2008. The person(s) controlling the copyright in some of this 64 material may not have granted the IETF Trust the right to allow 65 modifications of such material outside the IETF Standards Process. 66 Without obtaining an adequate license from the person(s) controlling 67 the copyright in such materials, this document may not be modified 68 outside the IETF Standards Process, and derivative works of it may 69 not be created outside the IETF Standards Process, except to format 70 it for publication as an RFC or to translate it into languages other 71 than English. 73 Table of Contents 75 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 76 1.1. Requirements notation . . . . . . . . . . . . . . . . . . 3 77 2. Link attributes examples . . . . . . . . . . . . . . . . . . 4 78 3. Advertising Link Attributes . . . . . . . . . . . . . . . . . 4 79 3.1. TE Opaque LSA . . . . . . . . . . . . . . . . . . . . . . 4 80 3.2. Extended Link Opaque LSA . . . . . . . . . . . . . . . . 5 81 3.3. Selected Approach . . . . . . . . . . . . . . . . . . . . 5 82 4. Reused TE link attributes . . . . . . . . . . . . . . . . . . 6 83 4.1. Shared Risk Link Group (SRLG) . . . . . . . . . . . . . . 6 84 4.2. Extended Metrics . . . . . . . . . . . . . . . . . . . . 6 85 4.3. Administrative Group . . . . . . . . . . . . . . . . . . 7 86 5. Advertisement of Application Specific Values . . . . . . . . 7 87 5.1. Special Considerations for Maximum Link Bandwidth . . . . 10 88 5.2. Special Considerations for Unreserved Bandwidth . . . . . 11 89 6. Deployment Considerations . . . . . . . . . . . . . . . . . . 11 90 7. Attribute Advertisements and Enablement . . . . . . . . . . . 11 91 8. Backward Compatibility . . . . . . . . . . . . . . . . . . . 12 92 9. Security Considerations . . . . . . . . . . . . . . . . . . . 13 93 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 94 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 95 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 96 12.1. Normative References . . . . . . . . . . . . . . . . . . 13 97 12.2. Informative References . . . . . . . . . . . . . . . . . 14 98 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 100 1. Introduction 102 Various link attributes have been defined in OSPFv2 [RFC2328] in the 103 context of the MPLS traffic engineering and GMPLS. All these 104 attributes are distributed by OSPFv2 as sub-TLVs of the Link-TLV 105 advertised in the OSPFv2 TE Opaque LSA [RFC3630]. 107 Many of these link attributes are useful outside of the traditional 108 MPLS Traffic Engineering or GMPLS. This brings its own set of 109 problems, in particular how to distribute these link attributes in 110 OSPFv2 when MPLS TE or GMPLS are not deployed or are deployed in 111 parallel with other applications that use these link attributes. 113 [RFC7855] discusses use cases/requirements for SR. Included among 114 these use cases is SRTE. If both RSVP-TE and SRTE are deployed in a 115 network, link attribute advertisements can be used by one or both of 116 these applications. As there is no requirement for the link 117 attributes advertised on a given link used by SRTE to be identical to 118 the link attributes advertised on that same link used by RSVP-TE, 119 there is a clear requirement to indicate independently which link 120 attribute advertisements are to be used by each application. 122 As the number of applications which may wish to utilize link 123 attributes may grow in the future, an additional requirement is that 124 the extensions defined allow the association of additional 125 applications to link attributes without altering the format of the 126 advertisements or introducing new backwards compatibility issues. 128 Finally, there may still be many cases where a single attribute value 129 can be shared among multiple applications, so the solution should 130 minimize advertising duplicate link/attribute when possible. 132 1.1. Requirements notation 134 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 135 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 136 document are to be interpreted as described in [RFC2119]. 138 2. Link attributes examples 140 This section lists some of the link attributes originally defined for 141 MPLS Traffic Engineering that can be used for other purposes in 142 OSPFv2. The list doesn't necessarily contain all the required 143 attributes. 145 1. Remote Interface IP address [RFC3630] - OSPFv2 currently cannot 146 distinguish between parallel links between two OSPFv2 routers. 147 As a result, the two-way connectivity check performed during SPF 148 may succeed when the two routers disagree on which of the links 149 to use for data traffic. 151 2. Link Local/Remote Identifiers - [RFC4203] - Used for the two-way 152 connectivity check for parallel unnumbered links. Also used for 153 identifying adjacencies for unnumbered links in Segment Routing 154 traffic engineering. 156 3. Shared Risk Link Group (SRLG) [RFC4203] - In IPFRR, the SRLG is 157 used to compute diverse backup paths [RFC5714]. 159 4. Unidirectional Link Delay/Loss Metrics [RFC7471] - Could be used 160 for the shortest path first (SPF) computation using alternate 161 metrics within an OSPF area. 163 3. Advertising Link Attributes 165 This section outlines possible approaches for advertising link 166 attributes originally defined for MPLS Traffic Engineering purposes 167 or GMPLS when they are used for other applications. 169 3.1. TE Opaque LSA 171 One approach for advertising link attributes is to continue to use TE 172 Opaque LSA ([RFC3630]). There are several problems with this 173 approach: 175 1. Whenever the link is advertised in a TE Opaque LSA, the link 176 becomes a part of the TE topology, which may not match IP routed 177 topology. By making the link part of the TE topology, remote 178 nodes may mistakenly believe that the link is available for MPLS 179 TE or GMPLS, when, in fact, MPLS is not enabled on the link. 181 2. The TE Opaque LSA carries link attributes that are not used or 182 required by MPLS TE or GMPLS. There is no mechanism in a TE 183 Opaque LSA to indicate which of the link attributes are passed to 184 MPLS TE application and which are used by other applications 185 including OSPFv2 itself. 187 3. Link attributes used for non-TE purposes are partitioned across 188 multiple LSAs - the TE Opaque LSA and the Extended Link Opaque 189 LSA. This partitioning will require implementations to lookup 190 multiple LSAs to extract link attributes for a single link, 191 bringing needless complexity to OSPFv2 implementations. 193 The advantage of this approach is that there is no additional 194 standardization requirement to advertise the TE/GMPL attributes for 195 other applications. Additionally, link attributes are only 196 advertised once when both OSPF TE and other applications are deployed 197 on the same link. This is not expected to be a common deployment 198 scenario. 200 3.2. Extended Link Opaque LSA 202 An alternative approach for advertising link attributes is to use 203 Extended Link Opaque LSAs as defined in [RFC7684]. This LSA was 204 defined as a generic container for distribution of the extended link 205 attributes. There are several advantages in using Extended Link LSA: 207 1. Advertisement of the link attributes does not make the link part 208 of the TE topology. It avoids any conflicts and is fully 209 compatible with the [RFC3630]. 211 2. The TE Opaque LSA remains truly opaque to OSPFv2 as originally 212 defined in [RFC3630]. Its content is not inspected by OSPFv2 and 213 OSPFv2 acts as a pure transport. 215 3. There is clear distinction between link attributes used by TE and 216 link attributes used by other OSPFv2 applications. 218 4. All link attributes that are used by OSPFv2 applications are 219 advertised in a single LSA, the Extended Link Opaque LSA. 221 The disadvantage of this approach is that in rare cases, the same 222 link attribute is advertised in both the TE Opaque and Extended Link 223 Attribute LSAs. Additionally, there will be additional 224 standardization effort. However, this could also be viewed as an 225 advantage as the non-TE use cases for the TE link attributes are 226 documented and validated by the OSPF working group. 228 3.3. Selected Approach 230 It is RECOMMENDED to use the Extended Link Opaque LSA ([RFC7684] to 231 advertise any link attributes used for non-TE purposes in OSPFv2, 232 including those that have been originally defined for TE purposes. 233 TE link attributes used for TE purposes continue to use TE Opaque LSA 234 ([RFC3630]). 236 It is also RECOMMENDED to keep the format of the link attribute TLVs 237 that have been defined for TE purposes unchanged even when they are 238 used for non-TE purposes. 240 Finally, it is RECOMMENDED to allocate unique code points for link 241 attribute TLVs that have been defined for TE purposes for the OSPFv2 242 Extended Link TLV Sub-TLV Registry as defined in [RFC7684]. For each 243 reused TLV, the code point will be defined in an IETF document along 244 with the expected usecase(s). 246 4. Reused TE link attributes 248 This section defines the use case and code points for the OSPFv2 249 Extended Link TLV Sub-TLV Registry for some of the link attributes 250 that have been originally defined for TE or GMPLS purposes. 252 Remote interface IP address and Link Local/Remote Identifiers have 253 been added as sub-TLVs of OSPFv2 Extended Link TLV by 254 [I-D.ietf-ospf-link-overload]. 256 4.1. Shared Risk Link Group (SRLG) 258 The SRLG of a link can be used in IPFRR to compute a backup path that 259 does not share any SRLG group with the protected link. 261 To advertise the SRLG of the link in the OSPFv2 Extended Link TLV, 262 the same format of the sub-TLV as defined in section 1.3. of 263 [RFC4203] is used and TLV type TBD1 is used. 265 4.2. Extended Metrics 267 [RFC3630] defines several link bandwidth types. [RFC7471] defines 268 extended link metrics that are based on link bandwidth, delay and 269 loss characteristics. All these can be used to compute best paths 270 within an OSPF area to satisfy requirements for bandwidth, delay 271 (nominal or worst case) or loss. 273 To advertise extended link metrics in the OSPFv2 Extended Link TLV, 274 the same format of the sub-TLVs as defined in [RFC7471] is used with 275 following TLV types: 277 TBD2 - Unidirectional Link Delay 279 TBD3 - Min/Max Unidirectional Link Delay 281 TBD4 - Unidirectional Delay Variation 283 TBD5 - Unidirectional Link Loss 284 TBD6 - Unidirectional Residual Bandwidth 286 TBD7 - Unidirectional Available Bandwidth 288 TBD8 - Unidirectional Utilized Bandwidth 290 4.3. Administrative Group 292 [RFC3630] and [RFC7308] define Administrative Group and Extended 293 Administrative Group sub-TLVs. 295 One use case where advertisement of the Extended Administrative 296 Group(s) for a link is required is described in 297 [I-D.hegdeppsenak-isis-sr-flex-algo]. 299 To advertise Administrative Group and Extended Administrative Group 300 in the OSPFv2 Extended Link TLV, the same format of the sub-TLVs as 301 defined in [RFC3630] and [RFC7308] is used with following TLV types: 303 TBD9 - Administrative Group 305 TBD10 - Extended Administrative Group 307 5. Advertisement of Application Specific Values 309 Multiple applications can utilize link attributes that are flooded by 310 OSPFv2. Some examples of applications using the link attributes are 311 Segment Routing Traffic Engineering and LFA [RFC5286]. 313 In some cases the link attribute only has a single value that is 314 applicable to all applications. An example is a Remote interface IP 315 address or Link Local/Remote Identifiers 316 [I-D.ietf-ospf-link-overload]. 318 In some cases the link attribute MAY have different values for 319 different applications. An example could be SRLG [Section 4.1], 320 where values used by LFA could be different then the values used by 321 Segment Routing Traffic Engineering. 323 To allow advertisement of the application specific values of the link 324 attribute, a new Extended Link Attribute sub-TLV of the Extended Link 325 TLV [RFC7471] is defined. The Extended Link Attribute sub-TLV is an 326 optional sub-TLV and can appear multiple times in the Extended Link 327 TLV. It has following format: 329 0 1 2 3 330 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 1 331 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 332 | Type | Length | 333 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 334 | SABML | UDABML | Reserved | 335 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 336 | Standard Application Bit-Mask | 337 +- -+ 338 | ... | 339 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 340 | User Defined Application Bit-Mask | 341 +- -+ 342 | ... | 343 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 344 | Link Attribute sub-sub-TLVs | 345 +- -+ 346 | ... | 348 where: 350 Type: TBD11, suggested value 8 352 Length: variable 354 SABML: Standard Application Bit-Mask Length. If the Standard 355 Application Bit-Mask is not present, the Standard Application Bit- 356 Mask Length MUST be set to 0. 358 UDABML: User Defined Application Bit-Mask Length. If the User 359 Defined Application Bit-Mask is not present, the User Defined 360 Application Bit-Mask Length MUST be set to 0. 362 Standard Application Bit-Mask: Optional set of bits, where each 363 bit represents a single standard application. The following bits 364 are defined by this document: 366 Bit-0: RSVP Traffic Engineering 368 Bit-1: Segment Routing Traffic Engineering 370 Bit-2: Loop Free Alternate (LFA). Includes all LFA types. 372 Bit-3: Flexible Algorithm as describe in 373 [I-D.hegdeppsenak-isis-sr-flex-algo]. 375 User Defined Application Bit-Mask: Optional set of bits, where 376 each bit represents a single user defined application. 378 Standard Application Bits are defined/sent starting with Bit 0. 379 Additional bit definitions that may be defined in the future SHOULD 380 be assigned in ascending bit order so as to minimize the number of 381 octets that will need to be transmitted. 383 User Defined Application bits have no relationship to Standard 384 Application bits and are NOT managed by IANA or any other standards 385 body. It is recommended that bits are used starting with Bit 0 so as 386 to minimize the number of octets required to advertise all of them. 388 Undefined bits in both Bit-Masks MUST be transmitted as 0 and MUST be 389 ignored on receipt. Bits that are NOT transmitted MUST be treated as 390 if they are set to 0 on receipt. 392 If the link attribute advertisement is limited to be used by a 393 specific set of applications, corresponding Bit-Masks MUST be present 394 and application specific bit(s) MUST be set for all applications that 395 use the link attributes advertised in the Extended Link Attribute 396 sub-TLV. 398 Application Bit-Masks apply to all link attributes that support 399 application specific values and are advertised in the Extended Link 400 Attribute sub-TLV. 402 The advantage of not making the Application Bit-Masks part of the 403 attribute advertisement itself is that we can keep the format of the 404 link attributes that have been defined previously and reuse the same 405 format when advertising them in the Extended Link Attribute sub-TLV. 407 If the link attribute is advertised and there is no Application Bit- 408 Mask present in the Extended Link Attribute Sub-TLV, the link 409 attribute advertisement MAY be used by any application. If, however, 410 another advertisement of the same link attribute includes any 411 Application Bit-Mask in the Extended Link Attribute sub-TLV, 412 applications that are listed in the Application Bit-Masks of such 413 Extended Link Attribute sub-TLV SHOULD use the attribute 414 advertisement which has the application specific bit set in the 415 Application Bit-Masks. 417 If the same application is listed in the Application Bit-Masks of 418 more then one Extended Link Attribute sub-TLV, the application SHOULD 419 use the first advertisement and ignore any subsequent advertisements 420 of the same attribute. This situation SHOULD be logged as an error. 422 This document defines the set of link attributes for which the 423 Application Bit-Masks may be advertised. If any of the Application 424 Bit-Masks is included in the Extended Link Attribute sub-TLV that 425 advertises any link attribute(s) NOT listed below, the Application 426 Bit-Masks MUST NOT be used for such link attribute(s). It MUST be 427 used for those attribute(s) that support application specific values. 428 Documents which define new link attributes MUST state whether the new 429 attributes support application specific values. The link attributes 430 to which the Application Bit-Masks may apply are: 432 - Shared Risk Link Group 434 - Unidirectional Link Delay 436 - Min/Max Unidirectional Link Delay 438 - Unidirectional Delay Variation 440 - Unidirectional Link Loss 442 - Unidirectional Residual Bandwidth 444 - Unidirectional Available Bandwidth 446 - Unidirectional Utilized Bandwidth 448 - Administrative Group 450 - Extended Administrative Group 452 5.1. Special Considerations for Maximum Link Bandwidth 454 Maximum link bandwidth is an application independent attribute of the 455 link. When advertised using the Application Specific Link Attributes 456 sub-TLV, multiple values for the same link MUST NOT be advertised. 457 This can be accomplished most efficiently by having a single 458 advertisement for a given link where both the Standard Application 459 Bit Mask and the User Defined Application Bit Mask are not present 460 (See Section Section 5). 462 Alternatively, similar can be achieved by having a single 463 advertisement for a given link where the Application Bit Mask 464 identifies all the applications which are making use of the value for 465 that link. 467 It is also possible to advertise the same value for a given link 468 multiple times with disjoint sets of applications specified in the 469 Application Bit Mask. This is less efficient but still valid. 471 If different values for Maximum Link Bandwidth for a given link are 472 advertised, all values MUST be ignored. 474 5.2. Special Considerations for Unreserved Bandwidth 476 Unreserved bandwidth is an attribute specific to RSVP. When 477 advertised using the Application Specific Link Attributes sub-TLV, 478 bits other than the RSVP-TE(R-bit) MUST NOT be set in the Application 479 Bit Mask. If an advertisement of Unreserved Bandwidth is received 480 with bits other than the RSVP-TE bit set, the advertisement MUST be 481 ignored. 483 6. Deployment Considerations 485 If link attributes are advertised associated with zero length 486 application bit masks for both standard applications and user defined 487 applications, then that set of link attributes MAY be used by any 488 application. If support for a new application is introduced on any 489 node in a network in the presence of such advertisements, these 490 advertisements MAY be used by the new application. If this is not 491 what is intended, then existing advertisements MUST be readvertised 492 with an explicit set of applications specified before a new 493 application is introduced. 495 7. Attribute Advertisements and Enablement 497 This document defines extensions to support the advertisement of 498 application specific link attributes. 500 Whether the presence of link attribute advertisements for a given 501 application indicates that the application is enabled on that link 502 depends upon the application. Similarly, whether the absence of link 503 attribute advertisements indicates that the application is not 504 enabled depends upon the application. 506 In the case of RSVP-TE, the advertisement of application specific 507 link attributes implies that RSVP is enabled on that link. 509 In the case of SRTE, advertisement of application specific link 510 attributes does NOT indicate enablement of SRTE. The advertisements 511 are only used to support constraints which may be applied when 512 specifying an explicit path. SRTE is implicitly enabled on all links 513 which are part of the Segment Routing enabled topology independent of 514 the existence of link attribute advertisements. 516 In the case of LFA, advertisement of application specific link 517 attributes does NOT indicate enablement of LFA on that link. 518 Enablement is controlled by local configuration. 520 In the case of Flexible Algorithm, advertisement of application 521 specific link attributes does NOT indicate enablement of Flexible 522 Algorithm on that link. Rather the attributes are used to determine 523 what links are included/excluded in the algorithm specific 524 constrained SPF. This is fully specified in 525 [I-D.hegdeppsenak-isis-sr-flex-algo]. 527 If, in the future, additional standard applications are defined to 528 use this mechanism, the specification defining this use MUST define 529 the relationship between application specific link attribute 530 advertisements and enablement for that application. 532 This document allows the advertisement of application specific link 533 attributes with no application identifiers i.e., both the Standard 534 Application Bit Mask and the User Defined Application Bit Mask are 535 not present (See Section Section 5). This supports the use of the 536 link attribute by any application. In the presence of an application 537 where the advertisement of link attribute advertisements is used to 538 infer the enablement of an application on that link (e.g., RSVP-TE), 539 the absence of the application identifier leaves ambiguous whether 540 that application is enabled on such a link. This needs to be 541 considered when making use of the "any application" encoding. 543 8. Backward Compatibility 545 Link attributes may be concurrently advertised in both the TE Opaque 546 LSA [RFC3630] and the Extended Link Opaque LSA [RFC7684]. 548 In fact, there is at least one OSPF implementation that utilizes the 549 link attributes advertised in TE Opaque LSAs [RFC3630] for Non-RSVP 550 TE applications. For example, this implementation of LFA and remote 551 LFA utilizes links attributes such as Shared Risk Link Groups (SRLG) 552 [RFC4203] and Admin Group [[RFC3630]advertised in TE Opaque LSAs. 553 These applications are described in [RFC5286], [RFC7490], 554 [I-D.ietf-rtgwg-lfa-manageability] and 555 [I-D.psarkar-rtgwg-rlfa-node-protection]. 557 When an OSPF routing domain includes routers using link attributes 558 from TE Opaque LSAs for Non-RSVP TE applications such as LFA, OSPF 559 routers in that domain should continue to advertise such TE Opaque 560 LSAs. If there are also OSPF routers using the link attributes 561 described herein for any application, OSPF routers in the routing 562 domain will also need to advertise these attributes in OSPF Extended 563 Link Attributes LSAs [RFC7684]. In such a deployment, the advertised 564 attributes SHOULD be the same and Non-RSVP application access to link 565 attributes is a matter of local policy. 567 9. Security Considerations 569 Implementations must assure that malformed TLV and Sub-TLV 570 permutations do not result in errors that cause hard OSPFv2 failures. 572 10. IANA Considerations 574 OSPFv2 Extended Link TLV Sub-TLVs registry [RFC7684] defines sub-TLVs 575 at any level of nesting for OSPFv2 Extended Link TLVs. This 576 specification updates OSPFv2 Extended Link TLV sub-TLVs registry with 577 the following TLV types: 579 TBD1 (9 Recommended) - Shared Risk Link Group 581 TBD2 (10 Recommended) - Unidirectional Link Delay 583 TBD3 (11 Recommended) - Min/Max Unidirectional Link Delay 585 TBD4 (12 Recommended) - Unidirectional Delay Variation 587 TBD5 (13 Recommended) - Unidirectional Link Loss 589 TBD6 (14 Recommended) - Unidirectional Residual Bandwidth 591 TBD7 (15 Recommended) - Unidirectional Available Bandwidth 593 TBD8 (16 Recommended) - Unidirectional Utilized Bandwidth 595 TBD9 (17 Recommended) - Administrative Group 597 TBD10 (18 Recommended) - Extended Administrative Group 599 TBD11 (8 Recommended) - Extended Link Attribute 601 11. Acknowledgments 603 Thanks to Chris Bowers for his review and comments. 605 12. References 607 12.1. Normative References 609 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 610 Requirement Levels", BCP 14, RFC 2119, 611 DOI 10.17487/RFC2119, March 1997, 612 . 614 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 615 (TE) Extensions to OSPF Version 2", RFC 3630, 616 DOI 10.17487/RFC3630, September 2003, 617 . 619 [RFC5714] Shand, M. and S. Bryant, "IP Fast Reroute Framework", 620 RFC 5714, DOI 10.17487/RFC5714, January 2010, 621 . 623 [RFC7308] Osborne, E., "Extended Administrative Groups in MPLS 624 Traffic Engineering (MPLS-TE)", RFC 7308, 625 DOI 10.17487/RFC7308, July 2014, 626 . 628 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 629 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 630 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 631 2015, . 633 12.2. Informative References 635 [I-D.hegdeppsenak-isis-sr-flex-algo] 636 Psenak, P., Hegde, S., Filsfils, C., and A. Gulko, "ISIS 637 Segment Routing Flexible Algorithm", draft-hegdeppsenak- 638 isis-sr-flex-algo-01 (work in progress), October 2017. 640 [I-D.ietf-idr-ls-distribution] 641 Gredler, H., Medved, J., Previdi, S., Farrel, A., and S. 642 Ray, "North-Bound Distribution of Link-State and TE 643 Information using BGP", draft-ietf-idr-ls-distribution-13 644 (work in progress), October 2015. 646 [I-D.ietf-ospf-link-overload] 647 Hegde, S., Sarkar, P., Gredler, H., Nanduri, M., and L. 648 Jalil, "OSPF Graceful Link shutdown", draft-ietf-ospf- 649 link-overload-14 (work in progress), January 2018. 651 [I-D.ietf-ospf-segment-routing-extensions] 652 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., 653 Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 654 Extensions for Segment Routing", draft-ietf-ospf-segment- 655 routing-extensions-24 (work in progress), December 2017. 657 [I-D.ietf-rtgwg-lfa-manageability] 658 Litkowski, S., Decraene, B., Filsfils, C., Raza, K., and 659 M. Horneffer, "Operational management of Loop Free 660 Alternates", draft-ietf-rtgwg-lfa-manageability-11 (work 661 in progress), June 2015. 663 [I-D.psarkar-rtgwg-rlfa-node-protection] 664 psarkar@juniper.net, p., Gredler, H., Hegde, S., Bowers, 665 C., Litkowski, S., and H. Raghuveer, "Remote-LFA Node 666 Protection and Manageability", draft-psarkar-rtgwg-rlfa- 667 node-protection-05 (work in progress), June 2014. 669 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 670 DOI 10.17487/RFC2328, April 1998, 671 . 673 [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in 674 Support of Generalized Multi-Protocol Label Switching 675 (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005, 676 . 678 [RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for 679 IP Fast Reroute: Loop-Free Alternates", RFC 5286, 680 DOI 10.17487/RFC5286, September 2008, 681 . 683 [RFC7471] Giacalone, S., Ward, D., Drake, J., Atlas, A., and S. 684 Previdi, "OSPF Traffic Engineering (TE) Metric 685 Extensions", RFC 7471, DOI 10.17487/RFC7471, March 2015, 686 . 688 [RFC7490] Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N. 689 So, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)", 690 RFC 7490, DOI 10.17487/RFC7490, April 2015, 691 . 693 [RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B., 694 Litkowski, S., Horneffer, M., and R. Shakir, "Source 695 Packet Routing in Networking (SPRING) Problem Statement 696 and Requirements", RFC 7855, DOI 10.17487/RFC7855, May 697 2016, . 699 Authors' Addresses 701 Peter Psenak (editor) 702 Cisco Systems, Inc. 703 Eurovea Centre, Central 3 704 Pribinova Street 10 705 Bratislava 81109 706 Slovakia 708 Email: ppsenak@cisco.com 709 Acee Lindem 710 Cisco Systems 711 301 Midenhall Way 712 Cary, NC 27513 713 USA 715 Email: acee@cisco.com 717 Les Ginsberg 718 Cisco Systems 719 821 Alder Drive 720 MILPITAS, CA 95035 721 USA 723 Email: ginsberg@cisco.com 725 Wim Henderickx 726 Nokia 727 Copernicuslaan 50 728 Antwerp, 2018 94089 729 Belgium 731 Email: wim.henderickx@nokia.com 733 Jeff Tantsura 734 Nuage Networks 735 US 737 Email: jefftant.ietf@gmail.com 739 Hannes Gredler 740 RtBrick Inc. 742 Email: hannes@rtbrick.com 744 John Drake 745 Juniper Networks 747 Email: jdrake@juniper.net