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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 LSR Working Group P. Psenak, Ed. 3 Internet-Draft Cisco Systems, Inc. 4 Intended status: Standards Track A. Lindem 5 Expires: December 17, 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 June 15, 2018 17 OSPF Link Traffic Engineering (TE) Attribute Reuse 18 draft-ietf-ospf-te-link-attr-reuse-04.txt 20 Abstract 22 Various link attributes have been defined in OSPF in the context of 23 the MPLS Traffic Engineering (TE) and GMPLS. Many of these link 24 attributes can be used for applications other than MPLS Traffic 25 Engineering or GMPLS. This document defines how to distribute such 26 attributes in OSPFv2 and OSPFv3 for applications other than MPLS 27 Traffic Engineering or GMPLS. 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 December 17, 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. OSPFv2 TE Opaque LSA and OSPFv3 Intra-Area-TE-LSA . . . . 4 80 3.2. OSPFv2 Extended Link Opaque LSA and OSPFv3 E-Router-LSA . 5 81 3.3. Selected Approach . . . . . . . . . . . . . . . . . . . . 6 82 4. Reused TE link attributes . . . . . . . . . . . . . . . . . . 6 83 4.1. Shared Risk Link Group (SRLG) . . . . . . . . . . . . . . 6 84 4.2. Extended Metrics . . . . . . . . . . . . . . . . . . . . 7 85 4.3. Administrative Group . . . . . . . . . . . . . . . . . . 8 86 5. Advertisement of Application Specific Values . . . . . . . . 8 87 6. Maximum Link Bandwidth . . . . . . . . . . . . . . . . . . . 11 88 7. Local Interface IPv6 Address Sub-TLV . . . . . . . . . . . . 11 89 8. Remote Interface IPv6 Address Sub-TLV . . . . . . . . . . . . 12 90 9. Deployment Considerations . . . . . . . . . . . . . . . . . . 12 91 10. Attribute Advertisements and Enablement . . . . . . . . . . . 12 92 11. Backward Compatibility . . . . . . . . . . . . . . . . . . . 13 93 12. Security Considerations . . . . . . . . . . . . . . . . . . . 14 94 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 95 13.1. OSPFv2 . . . . . . . . . . . . . . . . . . . . . . . . . 14 96 13.2. OSPFv3 . . . . . . . . . . . . . . . . . . . . . . . . . 14 97 14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15 98 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 99 15.1. Normative References . . . . . . . . . . . . . . . . . . 15 100 15.2. Informative References . . . . . . . . . . . . . . . . . 16 101 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 103 1. Introduction 105 Various link attributes have been defined in OSPFv2 [RFC2328] and 106 OSPFv3 [RFC5340] in the context of the MPLS traffic engineering and 107 GMPLS. All these attributes are distributed by OSPFv2 as sub-TLVs of 108 the Link-TLV advertised in the OSPFv2 TE Opaque LSA [RFC3630]. In 109 OSPFv3, they are distributed as sub-TLVs of the Link-TLV advertised 110 in the OSPFv3 Intra-Area-TE-LSA as defined in [RFC5329]. 112 Many of these link attributes are useful outside of traditional MPLS 113 Traffic Engineering or GMPLS. This brings its own set of problems, 114 in particular how to distribute these link attributes in OSPFv2 and 115 OSPFv3 when MPLS TE and GMPLS are not deployed or are deployed in 116 parallel with other applications that use these link attributes. 118 [RFC7855] discusses use cases/requirements for SR. Included among 119 these use cases is SRTE. If both RSVP-TE and SRTE are deployed in a 120 network, link attribute advertisements can be used by one or both of 121 these applications. As there is no requirement for the link 122 attributes advertised on a given link used by SRTE to be identical to 123 the link attributes advertised on that same link used by RSVP-TE, 124 there is a clear requirement to indicate independently which link 125 attribute advertisements are to be used by each application. 127 As the number of applications which may wish to utilize link 128 attributes may grow in the future, an additional requirement is that 129 the extensions defined allow the association of additional 130 applications to link attributes without altering the format of the 131 advertisements or introducing new backwards compatibility issues. 133 Finally, there may still be many cases where a single attribute value 134 can be shared among multiple applications, so the solution should 135 minimize advertising duplicate link/attribute when possible. 137 1.1. Requirements notation 139 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 140 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 141 document are to be interpreted as described in [RFC2119]. 143 2. Link attributes examples 145 This section lists some of the link attributes originally defined for 146 MPLS Traffic Engineering that can be used for other applications in 147 OSPFv2 and OSPFv3. The list doesn't necessarily contain all the 148 required attributes. 150 1. Remote Interface IP address [RFC3630] - OSPFv2 currently cannot 151 distinguish between parallel links between two OSPFv2 routers. 152 As a result, the two-way connectivity check performed during SPF 153 may succeed when the two routers disagree on which of the links 154 to use for data traffic. 156 2. Link Local/Remote Identifiers - [RFC4203] - Used for the two-way 157 connectivity check for parallel unnumbered links. Also used for 158 identifying adjacencies for unnumbered links in Segment Routing 159 traffic engineering. 161 3. Shared Risk Link Group (SRLG) [RFC4203] - In IPFRR, the SRLG is 162 used to compute diverse backup paths [RFC5714]. 164 4. Unidirectional Link Delay/Loss Metrics [RFC7471] - Could be used 165 for the shortest path first (SPF) computation using alternate 166 metrics within an OSPF area. 168 3. Advertising Link Attributes 170 This section outlines possible approaches for advertising link 171 attributes originally defined for MPLS Traffic Engineering or GMPLS 172 when they are used for other applications. 174 3.1. OSPFv2 TE Opaque LSA and OSPFv3 Intra-Area-TE-LSA 176 One approach for advertising link attributes is to continue to use 177 the OSPFv2 TE Opaque LSA [RFC3630] or the OSPFv3 Intra-Area-TE-LSA 178 [RFC5329]. There are several problems with this approach: 180 1. Whenever the link is advertised in an OSPFv2 TE Opaque LSA or in 181 an OSPFv3 Intra-Area-TE-LSA, the link becomes a part of the TE 182 topology, which may not match IP routed topology. By making the 183 link part of the TE topology, remote nodes may mistakenly believe 184 that the link is available for MPLS TE or GMPLS, when, in fact, 185 MPLS is not enabled on the link. 187 2. The OSPFv2 TE Opaque LSA and OSPFv3 Intra-Area-TE-LSA advertise 188 link attributes that are not used or required by MPLS TE or 189 GMPLS. There is no mechanism in these TE LSAs to indicate which 190 of the link attributes are passed to the MPLS TE application and 191 which are used by other applications including OSPF itself. 193 3. Link attributes used for non-TE applications are partitioned 194 across multiple LSAs - the TE Opaque LSA and the Extended Link 195 Opaque LSA in OSPFv2 and the OSPFv3 Intra-Area-TE-LSA and OSPFv3 196 Extended LSA Router-Link TLV [RFC8362] in OSPFv3. This 197 partitioning will require implementations to lookup multiple LSAs 198 to extract link attributes for a single link, bringing needless 199 complexity to OSPF implementations. 201 The advantage of this approach is that there is no additional 202 standardization requirement to advertise the TE/GMPL attributes for 203 other applications. Additionally, link attributes are only 204 advertised once when both OSPF TE and other applications are deployed 205 on the same link. This is not expected to be a common deployment 206 scenario. 208 3.2. OSPFv2 Extended Link Opaque LSA and OSPFv3 E-Router-LSA 210 An alternative approach for advertising link attributes is to use 211 Extended Link Opaque LSAs as defined in [RFC7684] for OSPFv2 and 212 Extended Router-LSAs [RFC8362] for OSPFv3. These LSAs were defined 213 as a generic containers for distribution of the extended link 214 attributes. There are several advantages in using them: 216 1. Advertisement of the link attributes does not make the link part 217 of the TE topology. It avoids any conflicts and is fully 218 compatible with the [RFC3630] and [RFC5329]. 220 2. The OSPFv2 TE Opaque LSA and OSPFv3 Intra-Area-TE-LSA remains 221 truly opaque to OSPFv2 and OSPFv3 as originally defined in 222 [RFC3630] and [RFC5329] respectively. Their contents are not 223 inspected by OSPF, that act as a pure transport. 225 3. There is clear distinction between link attributes used by TE and 226 link attributes used by other OSPFv2 or OSPFv3 applications. 228 4. All link attributes that are used by other applications are 229 advertised in a single LSA, the Extended Link Opaque LSA in 230 OSPFv2 or the OSPFv3 E-Router-LSA [RFC8362] in OSPFv3. 232 The disadvantage of this approach is that in rare cases, the same 233 link attribute is advertised in both the TE Opaque and Extended Link 234 Attribute LSAs in OSPFv2 or the Intra-Area-TE-LSA and E-Router-LSA in 235 OSPFv3. Additionally, there will be additional standardization 236 effort. However, this could also be viewed as an advantage as the 237 non-TE use cases for the TE link attributes are documented and 238 validated by the LSR working group. 240 3.3. Selected Approach 242 It is RECOMMENDED to use the Extended Link Opaque LSA [RFC7684] and 243 E-Router-LSA [RFC8362] to advertise any link attributes used for non- 244 TE applications in OSPFv2 or OSPFv3 respectively, including those 245 that have been originally defined for TE applications. 247 It is also RECOMMENDED that TE link attributes used for RSVP-TE/GMPLS 248 continue to use OSPFv2 TE Opaque LSA [RFC3630] and OSPFv3 Intra-Area- 249 TE-LSA [RFC5329]. 251 It is also RECOMMENDED to keep the format of the link attribute TLVs 252 that have been defined for TE applications unchanged even when they 253 are used for non-TE applications. 255 Finally, it is RECOMMENDED to allocate unique code points for these 256 TE link attribute TLVs in the OSPFv2 Extended Link TLV Sub-TLV 257 Registry [RFC7684] and in the OSPFv3 Extended LSA Sub-TLV Registry 258 [RFC8362]. For each reused TLV, the code point will be defined in an 259 IETF document along with the expected use-case(s). 261 4. Reused TE link attributes 263 This section defines the use case and code points for the OSPFv2 264 Extended Link TLV Sub-TLV Registry and OSPFv3 Extended LSA Sub-TLV 265 Registry for some of the link attributes that have been originally 266 defined for TE or GMPLS. 268 Remote interface IP address and Link Local/Remote Identifiers have 269 been added as sub-TLVs of OSPFv2 Extended Link TLV by [RFC8379]. 270 Link Local/Remote Identifiers are already included in the OSPFv3 271 Router-Link TLV [RFC8362]. 273 4.1. Shared Risk Link Group (SRLG) 275 The SRLG of a link can be used in IPFRR to compute a backup path that 276 does not share any SRLG group with the protected link. 278 To advertise the SRLG of the link in the OSPFv2 Extended Link TLV, 279 the same format for the sub-TLV defined in section 1.3 of [RFC4203] 280 is used and TLV type TBD1 is used. Similarly, for OSPFv3 to 281 advertise the SRLG in the OSPFv3 Router-Link TLV, TLV type TBD2 is 282 used. 284 4.2. Extended Metrics 286 [RFC3630] defines several link bandwidth types. [RFC7471] defines 287 extended link metrics that are based on link bandwidth, delay and 288 loss characteristics. All these can be used to compute best paths 289 within an OSPF area to satisfy requirements for bandwidth, delay 290 (nominal or worst case) or loss. 292 To advertise extended link metrics in the OSPFv2 Extended Link TLV, 293 the same format for the sub-TLVs defined in [RFC7471] is used with 294 the following TLV types: 296 TBD3 - Unidirectional Link Delay 298 TBD4 - Min/Max Unidirectional Link Delay 300 TBD5 - Unidirectional Delay Variation 302 TBD6 - Unidirectional Link Loss 304 TBD7 - Unidirectional Residual Bandwidth 306 TBD8 - Unidirectional Available Bandwidth 308 TBD9 - Unidirectional Utilized Bandwidth 310 To advertise extended link metrics in the OSPFv3 Extended LSA Router- 311 Link TLV, the same format for the sub-TLVs defined in [RFC7471] is 312 used with the following TLV types: 314 TBD10 - Unidirectional Link Delay 316 TBD11 - Min/Max Unidirectional Link Delay 318 TBD12 - Unidirectional Delay Variation 320 TBD13 - Unidirectional Link Loss 322 TBD14 - Unidirectional Residual Bandwidth 324 TBD15 - Unidirectional Available Bandwidth 326 TBD16 - Unidirectional Utilized Bandwidth 328 4.3. Administrative Group 330 [RFC3630] and [RFC7308] define the Administrative Group and Extended 331 Administrative Group sub-TLVs respectively. 333 One use case where advertisement of the Extended Administrative 334 Group(s) for a link is required is described in 335 [I-D.ietf-lsr-flex-algo]. 337 To advertise the Administrative Group and Extended Administrative 338 Group in the OSPFv2 Extended Link TLV, the same format for the sub- 339 TLVs defined in [RFC3630] and [RFC7308] is used with the following 340 TLV types: 342 TBD17 - Administrative Group 344 TBD18 - Extended Administrative Group 346 To advertise Administrative Group and Extended Administrative Group 347 in the OSPFv3 Router-Link TLV, the same format for the sub-TLVs 348 defined in [RFC3630] and [RFC7308] is used with the following TLV 349 types: 351 TBD19 - Administrative Group 353 TBD20 - Extended Administrative Group 355 5. Advertisement of Application Specific Values 357 Multiple applications can utilize link attributes that are advertised 358 by OSPF. Some examples of applications using the link attributes are 359 Segment Routing Traffic Engineering and LFA [RFC5286]. 361 In some cases the link attribute MAY have different values for 362 different applications. An example could be SRLG [Section 4.1], 363 where values used by LFA could be different then the values used by 364 Segment Routing Traffic Engineering. 366 To allow advertisement of the application specific values of the link 367 attribute, a new Application Specific Link Attributes (ASLA) sub-TLV 368 is defined. The ASLA sub-TLV is a sub-TLV of the OSPFv2 Extended 369 Link TLV [RFC7471] and OSPFv3 Router-Link TLV [RFC8362]. The ASLA 370 sub-TLV is an optional sub-TLV and can appear multiple times in the 371 OSPFv2 Extended Link TLV and OSPFv3 Router-Link TLV. It has the 372 following format: 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 | SABML | UDABML | Reserved | 380 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 381 | Standard Application Bit-Mask | 382 +- -+ 383 | ... | 384 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 385 | User Defined Application Bit-Mask | 386 +- -+ 387 | ... | 388 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 389 | Link Attribute sub-sub-TLVs | 390 +- -+ 391 | ... | 393 where: 395 Type: TBD21 (OSPFv2), TBD22 (OSPFv3) 397 Length: variable 399 SABML: Standard Application Bit-Mask Length. If the Standard 400 Application Bit-Mask is not present, the Standard Application Bit- 401 Mask Length MUST be set to 0. 403 UDABML: User Defined Application Bit-Mask Length. If the User 404 Defined Application Bit-Mask is not present, the User Defined 405 Application Bit-Mask Length MUST be set to 0. 407 Standard Application Bit-Mask: Optional set of bits, where each 408 bit represents a single standard application. The following bits 409 are defined by this document: 411 Bit-0: RSVP Traffic Engineering 413 Bit-1: Segment Routing Traffic Engineering 415 Bit-2: Loop Free Alternate (LFA). Includes all LFA types. 417 Bit-3: Flexible Algorithm as described in 418 [I-D.ietf-lsr-flex-algo]. 420 User Defined Application Bit-Mask: Optional set of bits, where 421 each bit represents a single user defined application. 423 Standard Application Bits are defined/sent starting with Bit 0. 424 Additional bit definitions that are defined in the future SHOULD be 425 assigned in ascending bit order so as to minimize the number of 426 octets that will need to be transmitted. 428 User Defined Application bits have no relationship to Standard 429 Application bits and are NOT managed by IANA or any other standards 430 body. It is recommended that bits are used starting with Bit 0 so as 431 to minimize the number of octets required to advertise all of them. 433 Undefined bits in both Bit-Masks MUST be transmitted as 0 and MUST be 434 ignored on receipt. Bits that are NOT transmitted MUST be treated as 435 if they are set to 0 on receipt. 437 If the link attribute advertisement is limited to be used by a 438 specific set of applications, corresponding Bit-Masks MUST be present 439 and application specific bit(s) MUST be set for all applications that 440 use the link attributes advertised in the ASLA sub-TLV. 442 Application Bit-Masks apply to all link attributes that support 443 application specific values and are advertised in the ASLA sub-TLV. 445 The advantage of not making the Application Bit-Masks part of the 446 attribute advertisement itself is that we can keep the format of the 447 link attributes that have been defined previously and reuse the same 448 format when advertising them in the ASLA sub-TLV. 450 When neither the Standard Application Bits nor the User Defined 451 Application bits are set (i.e., both SABML and UDABML are 0) in the 452 ASLA sub-TLV, then the link attributes included in it MUST be 453 considered as being applicable to all applications. 455 If, however, another advertisement of the same link attribute 456 includes any Application Bit-Mask in the ASLA sub-TLV, applications 457 that are listed in the Application Bit-Masks of such ASLA sub-TLV 458 SHOULD use the attribute advertisement which has the application 459 specific bit set in the Application Bit-Masks. 461 If the same application is listed in the Application Bit-Masks of 462 more then one ASLA sub-TLV, the application SHOULD use the first 463 advertisement and ignore any subsequent advertisements of the same 464 attribute. This situation SHOULD be logged as an error. 466 This document defines the initial set of link attributes that MUST 467 use ASLA sub-TLV if advertised in the OSPFv2 Extended Link TLV or in 468 the OSPFv3 Router-Link TLV. If the ASLA sub-TLV includes any link 469 attribute(s) NOT listed below, they MUST be ignored. Documents which 470 define new link attributes MUST state whether the new attributes 471 support application specific values and as such MUST be advertised in 472 an ASLA sub-TLV. The link attributes that MUST be advertised in ASLA 473 sub-TLVs are: 475 - Shared Risk Link Group 477 - Unidirectional Link Delay 479 - Min/Max Unidirectional Link Delay 481 - Unidirectional Delay Variation 483 - Unidirectional Link Loss 485 - Unidirectional Residual Bandwidth 487 - Unidirectional Available Bandwidth 489 - Unidirectional Utilized Bandwidth 491 - Administrative Group 493 - Extended Administrative Group 495 6. Maximum Link Bandwidth 497 Maximum link bandwidth is an application independent attribute of the 498 link that is defined in [RFC3630]. Because it is an application 499 independent attribute, it MUST NOT be advertised in ASLA sub-TLV. 500 Instead, it MAY be advertised as a sub-TLV of the Extended Link 501 Opaque LSA Extended Link TLV in OSPFv2 [RFC7684] or sub-TLV of OSPFv3 502 E-Router-LSA Router-Link TLV in OSPFv3 [RFC8362]. 504 To advertise the Maximum link bandwidth in the OSPFv2 Extended Link 505 TLV, the same format for sub-TLV defined in [RFC3630] is used with 506 TLV type TBD23. 508 To advertise the Maximum link bandwidth in the OSPFv3 Router-Link 509 TLV, the same format for sub-TLV defined in [RFC3630] is used with 510 TLV type TBD24. 512 7. Local Interface IPv6 Address Sub-TLV 514 The Local Interface IPv6 Address Sub-TLV is an application 515 independent attribute of the link that is defined in [RFC5329]. 516 Because it is an application independent attribute, it MUST NOT be 517 advertised in the ASLA sub-TLV. Instead, it MAY be advertised as a 518 sub-TLV of the OSPFv3 E-Router-LSA Router-Link TLV [RFC8362]. 520 To advertise the Local Interface IPv6 Address Sub-TLV in the OSPFv3 521 Router-Link TLV, the same format for sub-TLV defined in [RFC5329] is 522 used with TLV type TBD25. 524 8. Remote Interface IPv6 Address Sub-TLV 526 The Remote Interface IPv6 Address Sub-TLV is an application 527 independent attribute of the link that is defined in [RFC5329]. 528 Because it is an application independent attribute, it MUST NOT be 529 advertised in the ASLA sub-TLV. Instead, it MAY be advertised as a 530 sub-TLV of the OSPFv3 E-Router-LSA Router-Link TLV [RFC8362]. 532 To advertise the Remote Interface IPv6 Address Sub-TLV in the OSPFv3 533 Router-Link TLV, the same format for sub-TLV defined in [RFC5329] is 534 used with TLV type TBD26. 536 9. Deployment Considerations 538 If link attributes are advertised associated with zero length 539 application bit masks for both standard applications and user defined 540 applications, then that set of link attributes MAY be used by any 541 application. If support for a new application is introduced on any 542 node in a network in the presence of such advertisements, these 543 advertisements MAY be used by the new application. If this is not 544 what is intended, then existing advertisements MUST be readvertised 545 with an explicit set of applications specified before a new 546 application is introduced. 548 10. Attribute Advertisements and Enablement 550 This document defines extensions to support the advertisement of 551 application specific link attributes. 553 Whether the presence of link attribute advertisements for a given 554 application indicates that the application is enabled on that link 555 depends upon the application. Similarly, whether the absence of link 556 attribute advertisements indicates that the application is not 557 enabled depends upon the application. 559 In the case of RSVP-TE, the advertisement of application specific 560 link attributes implies that RSVP is enabled on that link. 562 In the case of SRTE, advertisement of application specific link 563 attributes does NOT indicate enablement of SRTE. The advertisements 564 are only used to support constraints which may be applied when 565 specifying an explicit path. SRTE is implicitly enabled on all links 566 which are part of the Segment Routing enabled topology independent of 567 the existence of link attribute advertisements. 569 In the case of LFA, advertisement of application specific link 570 attributes does NOT indicate enablement of LFA on that link. 571 Enablement is controlled by local configuration. 573 In the case of Flexible Algorithm, advertisement of application 574 specific link attributes does NOT indicate enablement of Flexible 575 Algorithm on that link. Rather the attributes are used to determine 576 what links are included/excluded in the algorithm specific 577 constrained SPF. This is fully specified in 578 [I-D.ietf-lsr-flex-algo]. 580 If, in the future, additional standard applications are defined to 581 use this mechanism, the specification defining this use MUST define 582 the relationship between application specific link attribute 583 advertisements and enablement for that application. 585 This document allows the advertisement of application specific link 586 attributes with no application identifiers i.e., both the Standard 587 Application Bit Mask and the User Defined Application Bit Mask are 588 not present Section 5. This supports the use of the link attribute 589 by any application. In the presence of an application where the 590 advertisement of link attribute advertisements is used to infer the 591 enablement of an application on that link (e.g., RSVP-TE), the 592 absence of the application identifier leaves ambiguous whether that 593 application is enabled on such a link. This needs to be considered 594 when making use of the "any application" encoding. 596 11. Backward Compatibility 598 Link attributes may be concurrently advertised in both the TE Opaque 599 LSA and the Extended Link Opaque LSA in OSPFv2 and the OSPFv3 Intra- 600 Area-TE-LSA and OSPFv3 Extended LSA Router-Link TLV in OSPFv3. 602 In fact, there is at least one OSPF implementation that utilizes the 603 link attributes advertised in TE Opaque LSAs [RFC3630] for Non-RSVP 604 TE applications. For example, this implementation of LFA and remote 605 LFA utilizes links attributes such as Shared Risk Link Groups (SRLG) 606 [RFC4203] and Admin Group [[RFC3630] advertised in TE Opaque LSAs. 607 These applications are described in [RFC5286], [RFC7490], [RFC7916] 608 and [RFC8102]. 610 When an OSPF routing domain includes routers using link attributes 611 from the OSPFv2 TE Opaque LSAs or the OSPFv3 Intra-Area-TE-LSA for 612 Non-RSVP TE applications such as LFA, OSPF routers in that domain 613 SHOULD continue to advertise such OSPFv2 TE Opaque LSAs or the OSPFv3 614 Intra-Area-TE-LSA. If there are also OSPF routers using the link 615 attributes described herein for any other application, OSPF routers 616 in the routing domain will also need to advertise these attributes in 617 OSPFv2 Extended Link Attributes LSAs or OSPFv3 E-Router-LSA. In such 618 a deployment, the advertised attributes SHOULD be the same and Non- 619 RSVP application access to link attributes is a matter of local 620 policy. 622 12. Security Considerations 624 Implementations must assure that malformed TLV and Sub-TLV 625 permutations do not result in errors that cause hard OSPF failures. 627 13. IANA Considerations 629 13.1. OSPFv2 631 OSPFv2 Extended Link TLV Sub-TLVs registry [RFC7684] defines sub-TLVs 632 at any level of nesting for OSPFv2 Extended Link TLVs. This 633 specification updates OSPFv2 Extended Link TLV sub-TLVs registry with 634 the following TLV types: 636 TBD21 (10 Recommended) - Application Specific Link Attributes 638 TBD1 (11 Recommended) - Shared Risk Link Group 640 TBD3 (12 Recommended) - Unidirectional Link Delay 642 TBD4 (13 Recommended) - Min/Max Unidirectional Link Delay 644 TBD5 (14 Recommended) - Unidirectional Delay Variation 646 TBD6 (15 Recommended) - Unidirectional Link Loss 648 TBD7 (16 Recommended) - Unidirectional Residual Bandwidth 650 TBD8 (17 Recommended) - Unidirectional Available Bandwidth 652 TBD9 (18 Recommended) - Unidirectional Utilized Bandwidth 654 TBD9 (19 Recommended) - Administrative Group 656 TBD17 (20 Recommended) - Extended Administrative Group 658 TBD23 (21 Recommended) - Maximum Link Bandwidth 660 13.2. OSPFv3 662 OSPFv3 Extended LSA Sub-TLV Registry [RFC8362] defines sub-TLVs at 663 any level of nesting for OSPFv3 Extended LSAs. This specification 664 updates OSPFv3 Extended LSA Sub-TLV Registry with the following TLV 665 types: 667 TBD22 (9 Recommended) - Application Specific Link Attributes 669 TBD2 (10 Recommended) - Shared Risk Link Group 671 TBD10 (11 Recommended) - Unidirectional Link Delay 673 TBD11 (12 Recommended) - Min/Max Unidirectional Link Delay 675 TBD12 (13 Recommended) - Unidirectional Delay Variation 677 TBD13 (14 Recommended) - Unidirectional Link Loss 679 TBD14 (15 Recommended) - Unidirectional Residual Bandwidth 681 TBD15 (16 Recommended) - Unidirectional Available Bandwidth 683 TBD16 (17 Recommended) - Unidirectional Utilized Bandwidth 685 TBD19 (18 Recommended) - Administrative Group 687 TBD20 (19 Recommended) - Extended Administrative Group 689 TBD24 (20 Recommended) - Maximum Link Bandwidth 691 TBD25 (21 Recommended) - Local Interface IPv6 Address Sub-TLV 693 TBD26 (22 Recommended) - Local Interface IPv6 Address Sub-TLV 695 14. Acknowledgments 697 Thanks to Chris Bowers for his review and comments. 699 15. References 701 15.1. Normative References 703 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 704 Requirement Levels", BCP 14, RFC 2119, 705 DOI 10.17487/RFC2119, March 1997, 706 . 708 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 709 (TE) Extensions to OSPF Version 2", RFC 3630, 710 DOI 10.17487/RFC3630, September 2003, 711 . 713 [RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed., 714 "Traffic Engineering Extensions to OSPF Version 3", 715 RFC 5329, DOI 10.17487/RFC5329, September 2008, 716 . 718 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 719 for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, 720 . 722 [RFC5714] Shand, M. and S. Bryant, "IP Fast Reroute Framework", 723 RFC 5714, DOI 10.17487/RFC5714, January 2010, 724 . 726 [RFC7308] Osborne, E., "Extended Administrative Groups in MPLS 727 Traffic Engineering (MPLS-TE)", RFC 7308, 728 DOI 10.17487/RFC7308, July 2014, 729 . 731 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 732 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 733 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 734 2015, . 736 [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and 737 F. Baker, "OSPFv3 Link State Advertisement (LSA) 738 Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 739 2018, . 741 15.2. Informative References 743 [I-D.ietf-idr-ls-distribution] 744 Gredler, H., Medved, J., Previdi, S., Farrel, A., and S. 745 Ray, "North-Bound Distribution of Link-State and TE 746 Information using BGP", draft-ietf-idr-ls-distribution-13 747 (work in progress), October 2015. 749 [I-D.ietf-lsr-flex-algo] 750 Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and 751 A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex- 752 algo-00 (work in progress), May 2018. 754 [I-D.ietf-ospf-segment-routing-extensions] 755 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., 756 Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 757 Extensions for Segment Routing", draft-ietf-ospf-segment- 758 routing-extensions-25 (work in progress), April 2018. 760 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 761 DOI 10.17487/RFC2328, April 1998, 762 . 764 [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in 765 Support of Generalized Multi-Protocol Label Switching 766 (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005, 767 . 769 [RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for 770 IP Fast Reroute: Loop-Free Alternates", RFC 5286, 771 DOI 10.17487/RFC5286, September 2008, 772 . 774 [RFC7471] Giacalone, S., Ward, D., Drake, J., Atlas, A., and S. 775 Previdi, "OSPF Traffic Engineering (TE) Metric 776 Extensions", RFC 7471, DOI 10.17487/RFC7471, March 2015, 777 . 779 [RFC7490] Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N. 780 So, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)", 781 RFC 7490, DOI 10.17487/RFC7490, April 2015, 782 . 784 [RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B., 785 Litkowski, S., Horneffer, M., and R. Shakir, "Source 786 Packet Routing in Networking (SPRING) Problem Statement 787 and Requirements", RFC 7855, DOI 10.17487/RFC7855, May 788 2016, . 790 [RFC7916] Litkowski, S., Ed., Decraene, B., Filsfils, C., Raza, K., 791 Horneffer, M., and P. Sarkar, "Operational Management of 792 Loop-Free Alternates", RFC 7916, DOI 10.17487/RFC7916, 793 July 2016, . 795 [RFC8102] Sarkar, P., Ed., Hegde, S., Bowers, C., Gredler, H., and 796 S. Litkowski, "Remote-LFA Node Protection and 797 Manageability", RFC 8102, DOI 10.17487/RFC8102, March 798 2017, . 800 [RFC8379] Hegde, S., Sarkar, P., Gredler, H., Nanduri, M., and L. 801 Jalil, "OSPF Graceful Link Shutdown", RFC 8379, 802 DOI 10.17487/RFC8379, May 2018, 803 . 805 Authors' Addresses 807 Peter Psenak (editor) 808 Cisco Systems, Inc. 809 Eurovea Centre, Central 3 810 Pribinova Street 10 811 Bratislava 81109 812 Slovakia 814 Email: ppsenak@cisco.com 816 Acee Lindem 817 Cisco Systems 818 301 Midenhall Way 819 Cary, NC 27513 820 USA 822 Email: acee@cisco.com 824 Les Ginsberg 825 Cisco Systems 826 821 Alder Drive 827 MILPITAS, CA 95035 828 USA 830 Email: ginsberg@cisco.com 832 Wim Henderickx 833 Nokia 834 Copernicuslaan 50 835 Antwerp, 2018 94089 836 Belgium 838 Email: wim.henderickx@nokia.com 840 Jeff Tantsura 841 Nuage Networks 842 US 844 Email: jefftant.ietf@gmail.com 845 Hannes Gredler 846 RtBrick Inc. 848 Email: hannes@rtbrick.com 850 John Drake 851 Juniper Networks 853 Email: jdrake@juniper.net