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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: draft-ietf-isis-te-app has been published as RFC 8919 == Outdated reference: A later version (-22) exists of draft-ietf-spring-segment-routing-policy-07 -- Obsolete informational reference (is this intentional?): RFC 5226 (Obsoleted by RFC 8126) Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 LSR Working Group P. Psenak, Ed. 3 Internet-Draft L. Ginsberg 4 Intended status: Standards Track Cisco Systems 5 Expires: December 24, 2020 W. Henderickx 6 Nokia 7 J. Tantsura 8 Apstra 9 J. Drake 10 Juniper Networks 11 June 22, 2020 13 OSPF Application-Specific Link Attributes 14 draft-ietf-ospf-te-link-attr-reuse-15.txt 16 Abstract 18 Existing traffic engineering related link attribute advertisements 19 have been defined and are used in RSVP-TE deployments. Since the 20 original RSVP-TE use case was defined, additional applications (e.g., 21 Segment Routing Policy, Loop Free Alternate) have been defined that 22 also make use of the link attribute advertisements. In cases where 23 multiple applications wish to make use of these link attributes the 24 current advertisements do not support application specific values for 25 a given attribute nor do they support indication of which 26 applications are using the advertised value for a given link. This 27 document introduces new link attribute advertisements in OSPFv2 and 28 OSPFv3 that address both of these shortcomings. 30 Status of This Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at https://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 This Internet-Draft will expire on December 24, 2020. 47 Copyright Notice 49 Copyright (c) 2020 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (https://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 65 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4 66 3. Existing Advertisement of Link Attributes . . . . . . . . . . 4 67 4. Advertisement of Link Attributes . . . . . . . . . . . . . . 4 68 4.1. OSPFv2 Extended Link Opaque LSA and OSPFv3 E-Router-LSA . 4 69 5. Advertisement of Application-Specific Values . . . . . . . . 5 70 6. Reused TE link attributes . . . . . . . . . . . . . . . . . . 9 71 6.1. Shared Risk Link Group (SRLG) . . . . . . . . . . . . . . 9 72 6.2. Extended Metrics . . . . . . . . . . . . . . . . . . . . 9 73 6.3. Administrative Group . . . . . . . . . . . . . . . . . . 10 74 6.4. Traffic Engineering Metric . . . . . . . . . . . . . . . 10 75 7. Maximum Link Bandwidth . . . . . . . . . . . . . . . . . . . 11 76 8. Considerations for Extended TE Metrics . . . . . . . . . . . 11 77 9. Local Interface IPv6 Address Sub-TLV . . . . . . . . . . . . 11 78 10. Remote Interface IPv6 Address Sub-TLV . . . . . . . . . . . . 12 79 11. Attribute Advertisements and Enablement . . . . . . . . . . . 12 80 12. Deployment Considerations . . . . . . . . . . . . . . . . . . 13 81 12.1. Use of Legacy RSVP-TE LSA Advertisements . . . . . . . . 13 82 12.2. Interoperability, Backwards Compatibility and Migration 83 Concerns . . . . . . . . . . . . . . . . . . . . . . . . 14 84 12.2.1. Multiple Applications: Common Attributes with RSVP- 85 TE . . . . . . . . . . . . . . . . . . . . . . . . . 14 86 12.2.2. Multiple Applications: Some Attributes Not Shared 87 with RSVP-TE . . . . . . . . . . . . . . . . . . . . 14 88 12.2.3. Interoperability with Legacy Routers . . . . . . . . 15 89 12.2.4. Use of Application-Specific Advertisements for RSVP- 90 TE . . . . . . . . . . . . . . . . . . . . . . . . . 15 91 13. Security Considerations . . . . . . . . . . . . . . . . . . . 16 92 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 93 14.1. OSPFv2 . . . . . . . . . . . . . . . . . . . . . . . . . 16 94 14.2. OSPFv3 . . . . . . . . . . . . . . . . . . . . . . . . . 17 96 15. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 18 97 16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18 98 17. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 99 17.1. Normative References . . . . . . . . . . . . . . . . . . 19 100 17.2. Informative References . . . . . . . . . . . . . . . . . 20 101 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 103 1. Introduction 105 Advertisement of link attributes by the OSPFv2 [RFC2328] and OSPFv3 106 [RFC5340] protocols in support of traffic engineering (TE) was 107 introduced by [RFC3630] and [RFC5329] respectively. It has been 108 extended by [RFC4203], [RFC7308] and [RFC7471]. Use of these 109 extensions has been associated with deployments supporting Traffic 110 Engineering over Multiprotocol Label Switching (MPLS) in the presence 111 of the Resource Reservation Protocol (RSVP) - more succinctly 112 referred to as RSVP-TE [RFC3209]. 114 For the purposes of this document an application is a technology that 115 makes use of link attribute advertisements, examples of which are 116 listed in Section 5. 118 In recent years new applications have been introduced that have use 119 cases for many of the link attributes historically used by RSVP-TE. 120 Such applications include Segment Routing (SR) Policy 121 [I-D.ietf-spring-segment-routing-policy] and Loop Free Alternates 122 (LFA) [RFC5286]. This has introduced ambiguity in that if a 123 deployment includes a mix of RSVP-TE support and SR Policy support 124 (for example) it is not possible to unambiguously indicate which 125 advertisements are to be used by RSVP-TE and which advertisements are 126 to be used by SR Policy. If the topologies are fully congruent this 127 may not be an issue, but any incongruence leads to ambiguity. 129 An example where this ambiguity causes a problem is a network in that 130 RSVP-TE is enabled only on a subset of its links. A link attribute 131 is advertised for the purpose of another application (e.g. SR 132 Policy) for a link that is not enabled for RSVP-TE. As soon as the 133 router that is an RSVP-TE head-end sees the link attribute being 134 advertised for that link, it assumes RSVP-TE is enabled on that link, 135 even though it is not. If such RSVP-TE head-end router tries to 136 setup an RSVP-TE path via that link, it will result in the path setup 137 failure. 139 An additional issue arises in cases where both applications are 140 supported on a link but the link attribute values associated with 141 each application differ. Current advertisements do not support 142 advertising application-specific values for the same attribute on a 143 specific link. 145 This document defines extensions that address these issues. Also, as 146 evolution of use cases for link attributes can be expected to 147 continue in the years to come, this document defines a solution that 148 is easily extensible for the introduction of new applications and new 149 use cases. 151 2. Requirements Language 153 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 154 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 155 "OPTIONAL" in this document are to be interpreted as described in BCP 156 14 [RFC2119] [RFC8174] when, and only when, they appear in all 157 capitals, as shown here. 159 3. Existing Advertisement of Link Attributes 161 There are existing advertisements used in support of RSVP-TE. These 162 advertisements are carried in the OSPFv2 TE Opaque LSA [RFC3630] and 163 OSPFv3 Intra-Area-TE-LSA [RFC5329]. Additional RSVP-TE link 164 attributes have been defined by [RFC4203], [RFC7308] and [RFC7471]. 166 Extended Link Opaque LSAs as defined in [RFC7684] for OSPFv2 and 167 Extended Router-LSAs [RFC8362] for OSPFv3 are used to advertise link 168 attributes that are used by applications other than RSVP-TE or GMPLS 169 [RFC4203]. These LSAs were defined as a generic containers for 170 distribution of the extended link attributes. 172 4. Advertisement of Link Attributes 174 This section outlines the solution for advertising link attributes 175 originally defined for RSVP-TE or GMPLS when they are used for other 176 applications. 178 4.1. OSPFv2 Extended Link Opaque LSA and OSPFv3 E-Router-LSA 180 Advantages of Extended Link Opaque LSAs as defined in [RFC7684] for 181 OSPFv2 and Extended Router-LSAs [RFC8362] for OSPFv3 with respect to 182 advertisement of link attributes originally defined for RSVP-TE when 183 used in packet networks and in GMPLS: 185 1. Advertisement of the link attributes does not make the link part 186 of the RSVP-TE topology. It avoids any conflicts and is fully 187 compatible with [RFC3630] and [RFC5329]. 189 2. The OSPFv2 TE Opaque LSA and OSPFv3 Intra-Area-TE-LSA remains 190 truly opaque to OSPFv2 and OSPFv3 as originally defined in 191 [RFC3630] and [RFC5329] respectively. Their contents are not 192 inspected by OSPF, which instead acts as a pure transport. 194 3. There is a clear distinction between link attributes used by 195 RSVP-TE and link attributes used by other OSPFv2 or OSPFv3 196 applications. 198 4. All link attributes that are used by other applications are 199 advertised in a single LSA, the Extended Link Opaque LSA in 200 OSPFv2 or the OSPFv3 E-Router-LSA [RFC8362] in OSPFv3. 202 The disadvantage of this approach is that in rare cases, the same 203 link attribute is advertised in both the TE Opaque and Extended Link 204 Attribute LSAs in OSPFv2 or the Intra-Area-TE-LSA and E-Router-LSA in 205 OSPFv3. 207 Extended Link Opaque LSA [RFC7684] and E-Router-LSA [RFC8362] are 208 used to advertise any link attributes used for non-RSVP-TE 209 applications in OSPFv2 or OSPFv3 respectively, including those that 210 have been originally defined for RSVP-TE applications (See 211 Section 6). 213 TE link attributes used for RSVP-TE/GMPLS continue to use OSPFv2 TE 214 Opaque LSA [RFC3630] and OSPFv3 Intra-Area-TE-LSA [RFC5329]. 216 The format of the link attribute TLVs that have been defined for 217 RSVP-TE applications will be kept unchanged even when they are used 218 for non-RSVP-TE applications. Unique code points are allocated for 219 these link attribute TLVs from the OSPFv2 Extended Link TLV Sub-TLV 220 Registry [RFC7684] and from the OSPFv3 Extended-LSA Sub-TLV Registry 221 [RFC8362], as specified in Section 14. 223 5. Advertisement of Application-Specific Values 225 To allow advertisement of the application-specific values of the link 226 attribute, a new Application-Specific Link Attributes (ASLA) sub-TLV 227 is defined. The ASLA sub-TLV is a sub-TLV of the OSPFv2 Extended 228 Link TLV [RFC7684] and OSPFv3 Router-Link TLV [RFC8362]. 230 On top of advertising the link attributes for standardized 231 applications, link attributes can be advertised for the purpose of 232 applications that are not standardized. We call such an application 233 a "User Defined Application" or "UDA". These applications are not 234 subject to standardization and are outside of the scope of this 235 specification. 237 The ASLA sub-TLV is an optional sub-TLV of OSPFv2 Extended Link TLV 238 and OSPFv3 Router-Link TLV. Multiple ASLA sub-TLVs can be present in 239 its parent TLV when different applications want to control different 240 link attributes or when different value of the same attribute needs 241 to be advertised by multiple applications. The ASLA sub-TLV MUST be 242 used for advertisement of the link attributes listed at the end on 243 this section if these are advertised inside OSPFv2 Extended Link TLV 244 and OSPFv3 Router-Link TLV. It has the following format: 246 0 1 2 3 247 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 1 248 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 249 | Type | Length | 250 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 251 | SABM Length | UDABM Length | Reserved | 252 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 253 | Standard Application Identifier Bit Mask | 254 +- -+ 255 | ... | 256 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 257 | User Defined Application Identifier Bit Mask | 258 +- -+ 259 | ... | 260 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 261 | Link Attribute sub-sub-TLVs | 262 +- -+ 263 | ... | 265 where: 267 Type: 10 (OSPFv2), 11 (OSPFv3) 269 Length: variable 271 SABM Length: Standard Application Identifier Bit Mask Length in 272 octets. The value MUST be 0, 4 or 8. If the Standard Application 273 Bit Mask is not present, the Standard Application Bit Mask Length 274 MUST be set to 0. 276 UDABM Length: User Defined Application Identifier Bit Mask Length 277 in octets. The value MUST be 0, 4 or 8. If the User Defined 278 Application Bit Mask is not present, the User Defined Application 279 Bit Mask Length MUST be set to 0. 281 Standard Application Identifier Bit Mask: Optional set of bits, 282 where each bit represents a single standard application. Bits are 283 defined in the Link Attribute Application Identifier Registry, 284 which has been defined in [I-D.ietf-isis-te-app]. Current 285 assignments are repeated here for informational purpose: 287 0 1 2 3 4 5 6 7 ... 288 +-+-+-+-+-+-+-+-+... 289 |R|S|F| ... 290 +-+-+-+-+-+-+-+-+... 292 Bit-0 (R-bit): RSVP-TE 294 Bit-1 (S-bit): Segment Routing Policy 296 Bit-2 (F-bit): Loop Free Alternate (LFA). Includes all LFA 297 types 299 User Defined Application Identifier Bit Mask: Optional set of 300 bits, where each bit represents a single user defined application. 302 If the SABM or UDABM length is other than 0, 4, or 8, the ASLA sub- 303 TLV MUST be ignored by the receiver. 305 Standard Application Identifier Bits are defined/sent starting with 306 Bit 0. Undefined bits that are transmitted MUST be transmitted as 0 307 and MUST be ignored on receipt. Bits that are not transmitted MUST 308 be treated as if they are set to 0 on receipt. Bits that are not 309 supported by an implementation MUST be ignored on receipt. 311 User Defined Application Identifier Bits have no relationship to 312 Standard Application Identifier Bits and are not managed by IANA or 313 any other standards body. It is recommended that bits are used 314 starting with Bit 0 so as to minimize the number of octets required 315 to advertise all UDAs. Undefined bits which are transmitted MUST be 316 transmitted as 0 and MUST be ignored on receipt. Bits that are not 317 transmitted MUST be treated as if they are set to 0 on receipt. Bits 318 that are not supported by an implementation MUST be ignored on 319 receipt. 321 If the link attribute advertisement is intended to be only used by a 322 specific set of applications, corresponding Bit Masks MUST be present 323 and application-specific bit(s) MUST be set for all applications that 324 use the link attributes advertised in the ASLA sub-TLV. 326 Application Bit Masks apply to all link attributes that support 327 application-specific values and are advertised in the ASLA sub-TLV. 329 The advantage of not making the Application Bit Masks part of the 330 attribute advertisement itself is that the format of any previously 331 defined link attributes can be kept and reused when advertising them 332 in the ASLA sub-TLV. 334 If the same attribute is advertised in more than single ASLA sub-TLVs 335 with the application listed in the Application Bit Masks, the 336 application SHOULD use the first instance of advertisement and ignore 337 any subsequent advertisements of that attribute. 339 If link attributes are advertised associated with zero length 340 Application Identifier Bit Masks for both standard applications and 341 user defined applications, then any Standard Application and/or any 342 User Defined Application is permitted to use that set of link 343 attributes. If support for a new application is introduced on any 344 node in a network in the presence of such advertisements, these 345 advertisements are permitted to be used by the new application. If 346 this is not what is intended, then existing advertisements MUST be 347 readvertised with an explicit set of applications specified before a 348 new application is introduced. 350 An application-specific advertisement (Application Identifier Bit 351 Mask with a matching Application Identifier Bit set) for an attribute 352 MUST always be preferred over the advertisement of the same attribute 353 with the zero length Application Identifier Bit Masks for both 354 standard applications and user defined applications on the same link. 356 This document defines the initial set of link attributes that MUST 357 use the ASLA sub-TLV if advertised in the OSPFv2 Extended Link TLV or 358 in the OSPFv3 Router-Link TLV. Documents which define new link 359 attributes MUST state whether the new attributes support application- 360 specific values and as such are advertised in an ASLA sub-TLV. The 361 standard link attributes that are advertised in ASLA sub-TLVs are: 363 - Shared Risk Link Group [RFC4203] 365 - Unidirectional Link Delay [RFC7471] 367 - Min/Max Unidirectional Link Delay [RFC7471] 369 - Unidirectional Delay Variation [RFC7471] 371 - Unidirectional Link Loss [RFC7471] 373 - Unidirectional Residual Bandwidth [RFC7471] 375 - Unidirectional Available Bandwidth [RFC7471] 377 - Unidirectional Utilized Bandwidth [RFC7471] 379 - Administrative Group [RFC3630] 381 - Extended Administrative Group [RFC7308] 382 - TE Metric [RFC3630] 384 6. Reused TE link attributes 386 This section defines the use case and indicates the code points 387 (Section 14) from the OSPFv2 Extended Link TLV Sub-TLV Registry and 388 OSPFv3 Extended-LSA Sub-TLV Registry for some of the link attributes 389 that have been originally defined for RSVP-TE or GMPLS. 391 6.1. Shared Risk Link Group (SRLG) 393 The SRLG of a link can be used in OSPF calculated IPFRR (IP Fast 394 Reroute) [RFC5714] to compute a backup path that does not share any 395 SRLG group with the protected link. 397 To advertise the SRLG of the link in the OSPFv2 Extended Link TLV, 398 the same format for the sub-TLV defined in section 1.3 of [RFC4203] 399 is used and TLV type 11 is used. Similarly, for OSPFv3 to advertise 400 the SRLG in the OSPFv3 Router-Link TLV, TLV type 12 is used. 402 6.2. Extended Metrics 404 [RFC3630] defines several link bandwidth types. [RFC7471] defines 405 extended link metrics that are based on link bandwidth, delay and 406 loss characteristics. All of these can be used to compute primary 407 and backup paths within an OSPF area to satisfy requirements for 408 bandwidth, delay (nominal or worst case) or loss. 410 To advertise extended link metrics in the OSPFv2 Extended Link TLV, 411 the same format for the sub-TLVs defined in [RFC7471] is used with 412 the following TLV types: 414 12 - Unidirectional Link Delay 416 13 - Min/Max Unidirectional Link Delay 418 14 - Unidirectional Delay Variation 420 15 - Unidirectional Link Loss 422 16 - Unidirectional Residual Bandwidth 424 17 - Unidirectional Available Bandwidth 426 18 - Unidirectional Utilized Bandwidth 428 To advertise extended link metrics in the OSPFv3 Extended-LSA Router- 429 Link TLV, the same format for the sub-TLVs defined in [RFC7471] is 430 used with the following TLV types: 432 13 - Unidirectional Link Delay 434 14 - Min/Max Unidirectional Link Delay 436 15 - Unidirectional Delay Variation 438 16 - Unidirectional Link Loss 440 17 - Unidirectional Residual Bandwidth 442 18 - Unidirectional Available Bandwidth 444 19 - Unidirectional Utilized Bandwidth 446 6.3. Administrative Group 448 [RFC3630] and [RFC7308] define the Administrative Group and Extended 449 Administrative Group sub-TLVs respectively. 451 To advertise the Administrative Group and Extended Administrative 452 Group in the OSPFv2 Extended Link TLV, the same format for the sub- 453 TLVs defined in [RFC3630] and [RFC7308] is used with the following 454 TLV types: 456 19 - Administrative Group 458 20 - Extended Administrative Group 460 To advertise Administrative Group and Extended Administrative Group 461 in the OSPFv3 Router-Link TLV, the same format for the sub-TLVs 462 defined in [RFC3630] and [RFC7308] is used with the following TLV 463 types: 465 20 - Administrative Group 467 21 - Extended Administrative Group 469 6.4. Traffic Engineering Metric 471 [RFC3630] defines Traffic Engineering Metric. 473 To advertise the Traffic Engineering Metric in the OSPFv2 Extended 474 Link TLV, the same format for the sub-TLV defined in section 2.5.5 of 475 [RFC3630] is used and TLV type 22 is used. Similarly, for OSPFv3 to 476 advertise the Traffic Engineering Metric in the OSPFv3 Router-Link 477 TLV, TLV type 22 is used. 479 7. Maximum Link Bandwidth 481 Maximum link bandwidth is an application independent attribute of the 482 link that is defined in [RFC3630]. Because it is an application 483 independent attribute, it MUST NOT be advertised in ASLA sub-TLV. 484 Instead, it MAY be advertised as a sub-TLV of the Extended Link 485 Opaque LSA Extended Link TLV in OSPFv2 [RFC7684] or sub-TLV of OSPFv3 486 E-Router-LSA Router-Link TLV in OSPFv3 [RFC8362]. 488 To advertise the Maximum link bandwidth in the OSPFv2 Extended Link 489 TLV, the same format for sub-TLV defined in [RFC3630] is used with 490 TLV type 23. 492 To advertise the Maximum link bandwidth in the OSPFv3 Router-Link 493 TLV, the same format for sub-TLV defined in [RFC3630] is used with 494 TLV type 23. 496 8. Considerations for Extended TE Metrics 498 [RFC7471] defines a number of dynamic performance metrics associated 499 with a link. It is conceivable that such metrics could be measured 500 specific to traffic associated with a specific application. 501 Therefore this document includes support for advertising these link 502 attributes specific to a given application. However, in practice it 503 may well be more practical to have these metrics reflect the 504 performance of all traffic on the link regardless of application. In 505 such cases, advertisements for these attributes can be associated 506 with all of the applications utilizing that link. This can be done 507 either by explicitly specifying the applications in the Application 508 Identifier Bit Mask or by using a zero length Application Identifier 509 Bit Mask. 511 9. Local Interface IPv6 Address Sub-TLV 513 The Local Interface IPv6 Address Sub-TLV is an application 514 independent attribute of the link that is defined in [RFC5329]. 515 Because it is an application independent attribute, it MUST NOT be 516 advertised in the ASLA sub-TLV. Instead, it MAY be advertised as a 517 sub-TLV of the OSPFv3 E-Router-LSA Router-Link TLV [RFC8362]. 519 To advertise the Local Interface IPv6 Address Sub-TLV in the OSPFv3 520 Router-Link TLV, the same format for sub-TLV defined in [RFC5329] is 521 used with TLV type 24. 523 10. Remote Interface IPv6 Address Sub-TLV 525 The Remote Interface IPv6 Address Sub-TLV is an application 526 independent attribute of the link that is defined in [RFC5329]. 527 Because it is an application independent attribute, it MUST NOT be 528 advertised in the ASLA sub-TLV. Instead, it MAY be advertised as a 529 sub-TLV of the OSPFv3 E-Router-LSA Router-Link TLV [RFC8362]. 531 To advertise the Remote Interface IPv6 Address Sub-TLV in the OSPFv3 532 Router-Link TLV, the same format for sub-TLV defined in [RFC5329] is 533 used with TLV type 25. 535 11. Attribute Advertisements and Enablement 537 This document defines extensions to support the advertisement of 538 application-specific link attributes. 540 There are applications where the application enablement on the link 541 is relevant - e.g., RSVP-TE - one needs to make sure that RSVP is 542 enabled on the link before sending a RSVP-TE signaling message over 543 it. 545 There are applications where the enablement of the application on the 546 link is irrelevant and has nothing to do with the fact that some link 547 attributes are advertised for the purpose of such application. An 548 example of this is LFA. 550 Whether the presence of link attribute advertisements for a given 551 application indicates that the application is enabled on that link 552 depends upon the application. Similarly, whether the absence of link 553 attribute advertisements indicates that the application is not 554 enabled depends upon the application. 556 In the case of RSVP-TE, the advertisement of application-specific 557 link attributes has no implication of RSVP-TE being enabled on that 558 link. The RSVP-TE enablement is solely derived from the information 559 carried in the OSPFv2 TE Opaque LSA [RFC3630] and OSPFv3 Intra-Area- 560 TE-LSA [RFC5329]. 562 In the case of SR Policy, advertisement of application-specific link 563 attributes does not indicate enablement of SR Policy. The 564 advertisements are only used to support constraints that may be 565 applied when specifying an explicit path. SR Policy is implicitly 566 enabled on all links that are part of the Segment Routing enabled 567 topology independent of the existence of link attribute 568 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 If, in the future, additional standard applications are defined to 574 use this mechanism, the specification defining this use MUST define 575 the relationship between application-specific link attribute 576 advertisements and enablement for that application. 578 This document allows the advertisement of application-specific link 579 attributes with no application identifiers i.e., both the Standard 580 Application Identifier Bit Mask and the User Defined Application 581 Identifier Bit Mask are not present (See Section 5). This supports 582 the use of the link attribute by any application. In the presence of 583 an application where the advertisement of link attribute 584 advertisements is used to infer the enablement of an application on 585 that link (e.g., RSVP-TE), the absence of the application identifier 586 leaves ambiguous whether that application is enabled on such a link. 587 This needs to be considered when making use of the "any application" 588 encoding. 590 12. Deployment Considerations 592 12.1. Use of Legacy RSVP-TE LSA Advertisements 594 Bit Identifiers for Standard Applications are defined in Section 5. 595 All of the identifiers defined in this document are associated with 596 applications that were already deployed in some networks prior to the 597 writing of this document. Therefore, such applications have been 598 deployed using the RSVP-TE LSA advertisements. The Standard 599 Applications defined in this document may continue to use RSVP-TE LSA 600 advertisements for a given link so long as at least one of the 601 following conditions is true: 603 The application is RSVP-TE 605 The application is SR Policy or LFA and RSVP-TE is not deployed 606 anywhere in the network 608 The application is SR Policy or LFA, RSVP-TE is deployed in the 609 network, and both the set of links on which SR Policy and/or LFA 610 advertisements are required and the attribute values used by SR 611 Policy and/or LFA on all such links is fully congruent with the 612 links and attribute values used by RSVP-TE 614 Under the conditions defined above, implementations that support the 615 extensions defined in this document have the choice of using RSVP-TE 616 LSA advertisements or application-specific advertisements in support 617 of SR Policy and/or LFA. This will require implementations to 618 provide controls specifying which type of advertisements are to be 619 sent/ processed on receive for these applications. Further 620 discussion of the associated issues can be found in Section 12.2. 622 New applications that future documents define to make use of the 623 advertisements defined in this document MUST NOT make use of RSVP-TE 624 LSA advertisements. This simplifies deployment of new applications 625 by eliminating the need to support multiple ways to advertise 626 attributes for the new applications. 628 12.2. Interoperability, Backwards Compatibility and Migration Concerns 630 Existing deployments of RSVP-TE, SR Policy, and/or LFA utilize the 631 legacy advertisements listed in Section 3. Routers which do not 632 support the extensions defined in this document will only process 633 legacy advertisements and are likely to infer that RSVP-TE is enabled 634 on the links for which legacy advertisements exist. It is expected 635 that deployments using the legacy advertisements will persist for a 636 significant period of time. Therefore deployments using the 637 extensions defined in this document in the presence of routers that 638 do not support these extensions need to be able to interoperate with 639 the use of legacy advertisements by the legacy routers. The 640 following sub-sections discuss interoperability and backwards 641 compatibility concerns for a number of deployment scenarios. 643 12.2.1. Multiple Applications: Common Attributes with RSVP-TE 645 In cases where multiple applications are utilizing a given link, one 646 of the applications is RSVP-TE, and all link attributes for a given 647 link are common to the set of applications utilizing that link, 648 interoperability is achieved by using legacy advertisements for RSVP- 649 TE. Attributes for applications other than RSVP-TE MUST be 650 advertised using application-specific advertisements. This results 651 in duplicate advertisements for those attributes. 653 12.2.2. Multiple Applications: Some Attributes Not Shared with RSVP-TE 655 In cases where one or more applications other than RSVP-TE are 656 utilizing a given link and one or more link attribute values are not 657 shared with RSVP-TE, interoperability is achieved by using legacy 658 advertisements for RSVP-TE. Attributes for applications other than 659 RSVP-TE MUST be advertised using application-specific advertisements. 660 In cases where some link attributes are shared with RSVP-TE, this 661 requires duplicate advertisements for those attributes 663 12.2.3. Interoperability with Legacy Routers 665 For the applications defined in this document, routers that do not 666 support the extensions defined in this document will send and receive 667 only legacy link attribute advertisements. So long as there is any 668 legacy router in the network that has any of the applications 669 enabled, all routers MUST continue to advertise link attributes using 670 legacy advertisements. In addition, the link attribute values 671 associated with the set of applications supported by legacy routers 672 (RSVP-TE, SR Policy, and/or LFA) are always shared since legacy 673 routers have no way of advertising or processing application-specific 674 values. Once all legacy routers have been upgraded, migration from 675 legacy advertisements to application specific advertisements can be 676 achieved via the following steps: 678 1)Send new application-specific advertisements while continuing to 679 advertise using the legacy advertisement (all advertisements are then 680 duplicated). Receiving routers continue to use legacy 681 advertisements. 683 2)Enable the use of the application-specific advertisements on all 684 routers 686 3)Keep legacy advertisements if needed for RSVP-TE purposes. 688 When the migration is complete, it then becomes possible to advertise 689 incongruent values per application on a given link. 691 Documents defining new applications that make use of the application- 692 specific advertisements defined in this document MUST discuss 693 interoperability and backwards compatibility issues that could occur 694 in the presence of routers that do not support the new application. 696 12.2.4. Use of Application-Specific Advertisements for RSVP-TE 698 The extensions defined in this document support RSVP-TE as one of the 699 supported applications. It is however RECOMMENDED to advertise all 700 link-attributes for RSVP-TE in the existing OSPFv2 TE Opaque LSA 701 [RFC3630] and OSPFv3 Intra-Area-TE-LSA [RFC5329] to maintain backward 702 compatibility. RSVP-TE can eventually utilize the application- 703 specific advertisements for newly defined link attributes, that are 704 defined as application-specific. 706 Link attributes that are not allowed to be advertised in the ASLA 707 Sub-TLV, such as Maximum Reservable Link Bandwidth and Unreserved 708 Bandwidth MUST use the OSPFv2 TE Opaque LSA [RFC3630] and OSPFv3 709 Intra-Area-TE-LSA [RFC5329] and MUST NOT be advertised in ASLA Sub- 710 TLV. 712 13. Security Considerations 714 Existing security extensions as described in [RFC2328], [RFC5340] and 715 [RFC8362] apply to extensions defined in this document. While OSPF 716 is under a single administrative domain, there can be deployments 717 where potential attackers have access to one or more networks in the 718 OSPF routing domain. In these deployments, stronger authentication 719 mechanisms such as those specified in [RFC5709], [RFC7474], [RFC4552] 720 or [RFC7166] SHOULD be used. 722 Implementations must assure that malformed TLV and Sub-TLV defined in 723 this document are detected and do not provide a vulnerability for 724 attackers to crash the OSPF router or routing process. Reception of 725 a malformed TLV or Sub-TLV SHOULD be counted and/or logged for 726 further analysis. Logging of malformed TLVs and Sub-TLVs SHOULD be 727 rate-limited to prevent a Denial of Service (DoS) attack (distributed 728 or otherwise) from overloading the OSPF control plane. 730 This document defines a new way to advertise link attributes. 731 Tampering with the information defined in this document may have an 732 effect on applications using it, including impacting Traffic 733 Engineering that uses various link attributes for its path 734 computation. This is similar in nature to the impacts associated 735 with (for example) [RFC3630]. As the advertisements defined in this 736 document limit the scope to specific applications, the impact of 737 tampering is similarly limited in scope. 739 14. IANA Considerations 741 This specifications updates two existing registries: 743 - OSPFv2 Extended Link TLV Sub-TLVs Registry 745 - OSPFv3 Extended-LSA Sub-TLV Registry 747 New values are allocated using the IETF Review procedure as described 748 in [RFC5226]. 750 14.1. OSPFv2 752 The OSPFv2 Extended Link TLV Sub-TLVs Registry [RFC7684] defines sub- 753 TLVs at any level of nesting for OSPFv2 Extended Link TLVs. IANA has 754 assigned the following Sub-TLV types from the OSPFv2 Extended Link 755 TLV Sub-TLVs Registry: 757 10 - Application-Specific Link Attributes 759 11 - Shared Risk Link Group 760 12 - Unidirectional Link Delay 762 13 - Min/Max Unidirectional Link Delay 764 14 - Unidirectional Delay Variation 766 15 - Unidirectional Link Loss 768 16 - Unidirectional Residual Bandwidth 770 17 - Unidirectional Available Bandwidth 772 18 - Unidirectional Utilized Bandwidth 774 19 - Administrative Group 776 20 - Extended Administrative Group 778 22 - TE Metric 780 23 - Maximum Link Bandwidth 782 14.2. OSPFv3 784 The OSPFv3 Extended-LSA Sub-TLV Registry [RFC8362] defines sub-TLVs 785 at any level of nesting for OSPFv3 Extended LSAs. IANA has assigned 786 the following Sub-TLV types from the OSPFv3 Extended-LSA Sub-TLV 787 Registry: 789 11 - Application-Specific Link Attributes 791 12 - Shared Risk Link Group 793 13 - Unidirectional Link Delay 795 14 - Min/Max Unidirectional Link Delay 797 15 - Unidirectional Delay Variation 799 16 - Unidirectional Link Loss 801 17 - Unidirectional Residual Bandwidth 803 18 - Unidirectional Available Bandwidth 805 19 - Unidirectional Utilized Bandwidth 807 20 - Administrative Group 808 21 - Extended Administrative Group 810 22 - TE Metric 812 23 - Maximum Link Bandwidth 814 24 - Local Interface IPv6 Address Sub-TLV 816 25 - Remote Interface IPv6 Address Sub-TLV 818 15. Contributors 820 The following people contributed to the content of this document and 821 should be considered as co-authors: 823 Acee Lindem 824 Cisco Systems 825 301 Midenhall Way 826 Cary, NC 27513 827 USA 829 Email: acee@cisco.com 831 Ketan Talaulikar 832 Cisco Systems, Inc. 833 India 835 Email: ketant@cisco.com 837 Hannes Gredler 838 RtBrick Inc. 839 Austria 841 Email: hannes@rtbrick.com 843 16. Acknowledgments 845 Thanks to Chris Bowers for his review and comments. 847 Thanks to Alvaro Retana for his detailed review and comments. 849 17. References 851 17.1. Normative References 853 [I-D.ietf-isis-te-app] 854 Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and 855 J. Drake, "IS-IS TE Attributes per application", draft- 856 ietf-isis-te-app-17 (work in progress), June 2020. 858 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 859 Requirement Levels", BCP 14, RFC 2119, 860 DOI 10.17487/RFC2119, March 1997, 861 . 863 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 864 DOI 10.17487/RFC2328, April 1998, 865 . 867 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 868 (TE) Extensions to OSPF Version 2", RFC 3630, 869 DOI 10.17487/RFC3630, September 2003, 870 . 872 [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in 873 Support of Generalized Multi-Protocol Label Switching 874 (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005, 875 . 877 [RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed., 878 "Traffic Engineering Extensions to OSPF Version 3", 879 RFC 5329, DOI 10.17487/RFC5329, September 2008, 880 . 882 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 883 for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, 884 . 886 [RFC7308] Osborne, E., "Extended Administrative Groups in MPLS 887 Traffic Engineering (MPLS-TE)", RFC 7308, 888 DOI 10.17487/RFC7308, July 2014, 889 . 891 [RFC7471] Giacalone, S., Ward, D., Drake, J., Atlas, A., and S. 892 Previdi, "OSPF Traffic Engineering (TE) Metric 893 Extensions", RFC 7471, DOI 10.17487/RFC7471, March 2015, 894 . 896 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 897 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 898 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 899 2015, . 901 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 902 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 903 May 2017, . 905 [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and 906 F. Baker, "OSPFv3 Link State Advertisement (LSA) 907 Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 908 2018, . 910 17.2. Informative References 912 [I-D.ietf-spring-segment-routing-policy] 913 Filsfils, C., Sivabalan, S., Voyer, D., Bogdanov, A., and 914 P. Mattes, "Segment Routing Policy Architecture", draft- 915 ietf-spring-segment-routing-policy-07 (work in progress), 916 May 2020. 918 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 919 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 920 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 921 . 923 [RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality 924 for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006, 925 . 927 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 928 IANA Considerations Section in RFCs", RFC 5226, 929 DOI 10.17487/RFC5226, May 2008, 930 . 932 [RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for 933 IP Fast Reroute: Loop-Free Alternates", RFC 5286, 934 DOI 10.17487/RFC5286, September 2008, 935 . 937 [RFC5709] Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M., 938 Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic 939 Authentication", RFC 5709, DOI 10.17487/RFC5709, October 940 2009, . 942 [RFC5714] Shand, M. and S. Bryant, "IP Fast Reroute Framework", 943 RFC 5714, DOI 10.17487/RFC5714, January 2010, 944 . 946 [RFC7166] Bhatia, M., Manral, V., and A. Lindem, "Supporting 947 Authentication Trailer for OSPFv3", RFC 7166, 948 DOI 10.17487/RFC7166, March 2014, 949 . 951 [RFC7474] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed., 952 "Security Extension for OSPFv2 When Using Manual Key 953 Management", RFC 7474, DOI 10.17487/RFC7474, April 2015, 954 . 956 Authors' Addresses 958 Peter Psenak (editor) 959 Cisco Systems 960 Eurovea Centre, Central 3 961 Pribinova Street 10 962 Bratislava 81109 963 Slovakia 965 Email: ppsenak@cisco.com 967 Les Ginsberg 968 Cisco Systems 969 821 Alder Drive 970 MILPITAS, CA 95035 971 USA 973 Email: ginsberg@cisco.com 975 Wim Henderickx 976 Nokia 977 Copernicuslaan 50 978 Antwerp, 2018 94089 979 Belgium 981 Email: wim.henderickx@nokia.com 982 Jeff Tantsura 983 Apstra 984 US 986 Email: jefftant.ietf@gmail.com 988 John Drake 989 Juniper Networks 990 1194 N. Mathilda Ave 991 Sunnyvale, California 94089 992 USA 994 Email: jdrake@juniper.net