idnits 2.17.1 draft-ietf-ospf-te-link-attr-reuse-16.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (June 30, 2020) is 1394 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'RFC7855' is mentioned on line 175, but not defined == Outdated reference: A later version (-22) exists of draft-ietf-spring-segment-routing-policy-07 -- Obsolete informational reference (is this intentional?): RFC 5226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: January 1, 2021 W. Henderickx 6 Nokia 7 J. Tantsura 8 Apstra 9 J. Drake 10 Juniper Networks 11 June 30, 2020 13 OSPF Application-Specific Link Attributes 14 draft-ietf-ospf-te-link-attr-reuse-16.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 January 1, 2021. 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. Requirements Discussion . . . . . . . . . . . . . . . . . . . 4 67 4. Existing Advertisement of Link Attributes . . . . . . . . . . 5 68 5. Advertisement of Link Attributes . . . . . . . . . . . . . . 5 69 5.1. OSPFv2 Extended Link Opaque LSA and OSPFv3 E-Router-LSA . 5 70 6. Advertisement of Application-Specific Values . . . . . . . . 6 71 7. Reused TE link attributes . . . . . . . . . . . . . . . . . . 9 72 7.1. Shared Risk Link Group (SRLG) . . . . . . . . . . . . . . 10 73 7.2. Extended Metrics . . . . . . . . . . . . . . . . . . . . 10 74 7.3. Administrative Group . . . . . . . . . . . . . . . . . . 11 75 7.4. Traffic Engineering Metric . . . . . . . . . . . . . . . 11 76 8. Maximum Link Bandwidth . . . . . . . . . . . . . . . . . . . 11 77 9. Considerations for Extended TE Metrics . . . . . . . . . . . 12 78 10. Local Interface IPv6 Address Sub-TLV . . . . . . . . . . . . 12 79 11. Remote Interface IPv6 Address Sub-TLV . . . . . . . . . . . . 12 80 12. Attribute Advertisements and Enablement . . . . . . . . . . . 13 81 13. Deployment Considerations . . . . . . . . . . . . . . . . . . 14 82 13.1. Use of Legacy RSVP-TE LSA Advertisements . . . . . . . . 14 83 13.2. Interoperability, Backwards Compatibility and Migration 84 Concerns . . . . . . . . . . . . . . . . . . . . . . . . 15 85 13.2.1. Multiple Applications: Common Attributes with RSVP- 86 TE . . . . . . . . . . . . . . . . . . . . . . . . . 15 87 13.2.2. Multiple Applications: Some Attributes Not Shared 88 with RSVP-TE . . . . . . . . . . . . . . . . . . . . 15 89 13.2.3. Interoperability with Legacy Routers . . . . . . . . 15 90 13.2.4. Use of Application-Specific Advertisements for RSVP- 91 TE . . . . . . . . . . . . . . . . . . . . . . . . . 16 92 14. Security Considerations . . . . . . . . . . . . . . . . . . . 16 93 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 94 15.1. OSPFv2 . . . . . . . . . . . . . . . . . . . . . . . . . 17 95 15.2. OSPFv3 . . . . . . . . . . . . . . . . . . . . . . . . . 18 96 16. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 19 97 17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19 98 18. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 99 18.1. Normative References . . . . . . . . . . . . . . . . . . 19 100 18.2. Informative References . . . . . . . . . . . . . . . . . 21 101 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 103 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 6. 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. Requirements Discussion 161 As stated previously, evolution of use cases for link attributes can 162 be expected to continue. Therefore, any discussion of existing use 163 cases is limited to requirements that are known at the time of this 164 writing. However, in order to determine the functionality required 165 beyond what already exists in OSPF, it is only necessary to discuss 166 use cases that justify the key points identified in the introduction, 167 which are: 169 1. Support for indicating which applications are using the link 170 attribute advertisements on a link 172 2. Support for advertising application-specific values for the same 173 attribute on a link 175 [RFC7855] discusses use cases/requirements for Segment Routing (SR). 176 Included among these use cases is SR Policy which is defined in 177 [I-D.ietf-spring-segment-routing-policy]. If both RSVP-TE and SR 178 Policy are deployed in a network, link attribute advertisements can 179 be used by one or both of these applications. As there is no 180 requirement for the link attributes advertised on a given link used 181 by SR Policy to be identical to the link attributes advertised on 182 that same link used by RSVP-TE, there is a clear requirement to 183 indicate independently which link attribute advertisements are to be 184 used by each application. 186 As the number of applications that may wish to utilize link 187 attributes may grow in the future, an additional requirement is that 188 the extensions defined allow the association of additional 189 applications to link attributes without altering the format of the 190 advertisements or introducing new backwards compatibility issues. 192 Finally, there may still be many cases where a single attribute value 193 can be shared among multiple applications, so the solution must 194 minimize advertising duplicate link/attribute pairs whenever 195 possible. 197 4. Existing Advertisement of Link Attributes 199 There are existing advertisements used in support of RSVP-TE. These 200 advertisements are carried in the OSPFv2 TE Opaque LSA [RFC3630] and 201 OSPFv3 Intra-Area-TE-LSA [RFC5329]. Additional RSVP-TE link 202 attributes have been defined by [RFC4203], [RFC7308] and [RFC7471]. 204 Extended Link Opaque LSAs as defined in [RFC7684] for OSPFv2 and 205 Extended Router-LSAs [RFC8362] for OSPFv3 are used to advertise link 206 attributes that are used by applications other than RSVP-TE or GMPLS 207 [RFC4203]. These LSAs were defined as a generic containers for 208 distribution of the extended link attributes. 210 5. Advertisement of Link Attributes 212 This section outlines the solution for advertising link attributes 213 originally defined for RSVP-TE or GMPLS when they are used for other 214 applications. 216 5.1. OSPFv2 Extended Link Opaque LSA and OSPFv3 E-Router-LSA 218 Advantages of Extended Link Opaque LSAs as defined in [RFC7684] for 219 OSPFv2 and Extended Router-LSAs [RFC8362] for OSPFv3 with respect to 220 advertisement of link attributes originally defined for RSVP-TE when 221 used in packet networks and in GMPLS: 223 1. Advertisement of the link attributes does not make the link part 224 of the RSVP-TE topology. It avoids any conflicts and is fully 225 compatible with [RFC3630] and [RFC5329]. 227 2. The OSPFv2 TE Opaque LSA and OSPFv3 Intra-Area-TE-LSA remains 228 truly opaque to OSPFv2 and OSPFv3 as originally defined in 229 [RFC3630] and [RFC5329] respectively. Their contents are not 230 inspected by OSPF, which instead acts as a pure transport. 232 3. There is a clear distinction between link attributes used by 233 RSVP-TE and link attributes used by other OSPFv2 or OSPFv3 234 applications. 236 4. All link attributes that are used by other applications are 237 advertised in a single LSA, the Extended Link Opaque LSA in 238 OSPFv2 or the OSPFv3 E-Router-LSA [RFC8362] in OSPFv3. 240 The disadvantage of this approach is that in rare cases, the same 241 link attribute is advertised in both the TE Opaque and Extended Link 242 Attribute LSAs in OSPFv2 or the Intra-Area-TE-LSA and E-Router-LSA in 243 OSPFv3. 245 Extended Link Opaque LSA [RFC7684] and E-Router-LSA [RFC8362] are 246 used to advertise any link attributes used for non-RSVP-TE 247 applications in OSPFv2 or OSPFv3 respectively, including those that 248 have been originally defined for RSVP-TE applications (See 249 Section 7). 251 TE link attributes used for RSVP-TE/GMPLS continue to use OSPFv2 TE 252 Opaque LSA [RFC3630] and OSPFv3 Intra-Area-TE-LSA [RFC5329]. 254 The format of the link attribute TLVs that have been defined for 255 RSVP-TE applications will be kept unchanged even when they are used 256 for non-RSVP-TE applications. Unique code points are allocated for 257 these link attribute TLVs from the OSPFv2 Extended Link TLV Sub-TLV 258 Registry [RFC7684] and from the OSPFv3 Extended-LSA Sub-TLV Registry 259 [RFC8362], as specified in Section 15. 261 6. Advertisement of Application-Specific Values 263 To allow advertisement of the application-specific values of the link 264 attribute, a new Application-Specific Link Attributes (ASLA) sub-TLV 265 is defined. The ASLA sub-TLV is a sub-TLV of the OSPFv2 Extended 266 Link TLV [RFC7684] and OSPFv3 Router-Link TLV [RFC8362]. 268 On top of advertising the link attributes for standardized 269 applications, link attributes can be advertised for the purpose of 270 applications that are not standardized. We call such an application 271 a "User Defined Application" or "UDA". These applications are not 272 subject to standardization and are outside of the scope of this 273 specification. 275 The ASLA sub-TLV is an optional sub-TLV of OSPFv2 Extended Link TLV 276 and OSPFv3 Router-Link TLV. Multiple ASLA sub-TLVs can be present in 277 its parent TLV when different applications want to control different 278 link attributes or when different value of the same attribute needs 279 to be advertised by multiple applications. The ASLA sub-TLV MUST be 280 used for advertisement of the link attributes listed at the end on 281 this section if these are advertised inside OSPFv2 Extended Link TLV 282 and OSPFv3 Router-Link TLV. It has the following format: 284 0 1 2 3 285 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 1 286 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 287 | Type | Length | 288 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 289 | SABM Length | UDABM Length | Reserved | 290 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 291 | Standard Application Identifier Bit Mask | 292 +- -+ 293 | ... | 294 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 295 | User Defined Application Identifier Bit Mask | 296 +- -+ 297 | ... | 298 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 299 | Link Attribute sub-sub-TLVs | 300 +- -+ 301 | ... | 303 where: 305 Type: 10 (OSPFv2), 11 (OSPFv3) 307 Length: variable 309 SABM Length: Standard Application Identifier Bit Mask Length in 310 octets. The value MUST be 0, 4 or 8. If the Standard Application 311 Bit Mask is not present, the Standard Application Bit Mask Length 312 MUST be set to 0. 314 UDABM Length: User Defined Application Identifier Bit Mask Length 315 in octets. The value MUST be 0, 4 or 8. If the User Defined 316 Application Bit Mask is not present, the User Defined Application 317 Bit Mask Length MUST be set to 0. 319 Standard Application Identifier Bit Mask: Optional set of bits, 320 where each bit represents a single standard application. Bits are 321 defined in the Link Attribute Application Identifier Registry, 322 which has been defined in [I-D.ietf-isis-te-app]. Current 323 assignments are repeated here for informational purpose: 325 0 1 2 3 4 5 6 7 ... 326 +-+-+-+-+-+-+-+-+... 327 |R|S|F| ... 328 +-+-+-+-+-+-+-+-+... 330 Bit-0 (R-bit): RSVP-TE 331 Bit-1 (S-bit): Segment Routing Policy 333 Bit-2 (F-bit): Loop Free Alternate (LFA). Includes all LFA 334 types 336 User Defined Application Identifier Bit Mask: Optional set of 337 bits, where each bit represents a single user defined application. 339 If the SABM or UDABM length is other than 0, 4, or 8, the ASLA sub- 340 TLV MUST be ignored by the receiver. 342 Standard Application Identifier Bits are defined/sent starting with 343 Bit 0. Undefined bits that are transmitted MUST be transmitted as 0 344 and MUST be ignored on receipt. Bits that are not transmitted MUST 345 be treated as if they are set to 0 on receipt. Bits that are not 346 supported by an implementation MUST be ignored on receipt. 348 User Defined Application Identifier Bits have no relationship to 349 Standard Application Identifier Bits and are not managed by IANA or 350 any other standards body. It is recommended that bits are used 351 starting with Bit 0 so as to minimize the number of octets required 352 to advertise all UDAs. Undefined bits which are transmitted MUST be 353 transmitted as 0 and MUST be ignored on receipt. Bits that are not 354 transmitted MUST be treated as if they are set to 0 on receipt. Bits 355 that are not supported by an implementation MUST be ignored on 356 receipt. 358 If the link attribute advertisement is intended to be only used by a 359 specific set of applications, corresponding Bit Masks MUST be present 360 and application-specific bit(s) MUST be set for all applications that 361 use the link attributes advertised in the ASLA sub-TLV. 363 Application Bit Masks apply to all link attributes that support 364 application-specific values and are advertised in the ASLA sub-TLV. 366 The advantage of not making the Application Bit Masks part of the 367 attribute advertisement itself is that the format of any previously 368 defined link attributes can be kept and reused when advertising them 369 in the ASLA sub-TLV. 371 If the same attribute is advertised in more than one ASLA sub-TLVs 372 with the application listed in the Application Bit Masks, the 373 application SHOULD use the first instance of advertisement and ignore 374 any subsequent advertisements of that attribute. 376 If link attributes are advertised with zero length Application 377 Identifier Bit Masks for both standard applications and user defined 378 applications, then any Standard Application and/or any User Defined 379 Application is permitted to use that set of link attributes. If 380 support for a new application is introduced on any node in a network 381 in the presence of such advertisements, these advertisements are 382 permitted to be used by the new application. If this is not what is 383 intended, then existing advertisements MUST be readvertised with an 384 explicit set of applications specified before a new application is 385 introduced. 387 An application-specific advertisement (Application Identifier Bit 388 Mask with a matching Application Identifier Bit set) for an attribute 389 MUST always be preferred over the advertisement of the same attribute 390 with the zero length Application Identifier Bit Masks for both 391 standard applications and user defined applications on the same link. 393 This document defines the initial set of link attributes that MUST 394 use the ASLA sub-TLV if advertised in the OSPFv2 Extended Link TLV or 395 in the OSPFv3 Router-Link TLV. Documents which define new link 396 attributes MUST state whether the new attributes support application- 397 specific values and as such are advertised in an ASLA sub-TLV. The 398 standard link attributes that are advertised in ASLA sub-TLVs are: 400 - Shared Risk Link Group [RFC4203] 402 - Unidirectional Link Delay [RFC7471] 404 - Min/Max Unidirectional Link Delay [RFC7471] 406 - Unidirectional Delay Variation [RFC7471] 408 - Unidirectional Link Loss [RFC7471] 410 - Unidirectional Residual Bandwidth [RFC7471] 412 - Unidirectional Available Bandwidth [RFC7471] 414 - Unidirectional Utilized Bandwidth [RFC7471] 416 - Administrative Group [RFC3630] 418 - Extended Administrative Group [RFC7308] 420 - TE Metric [RFC3630] 422 7. Reused TE link attributes 424 This section defines the use case and indicates the code points 425 (Section 15) from the OSPFv2 Extended Link TLV Sub-TLV Registry and 426 OSPFv3 Extended-LSA Sub-TLV Registry for some of the link attributes 427 that have been originally defined for RSVP-TE or GMPLS. 429 7.1. Shared Risk Link Group (SRLG) 431 The SRLG of a link can be used in OSPF calculated IPFRR (IP Fast 432 Reroute) [RFC5714] to compute a backup path that does not share any 433 SRLG group with the protected link. 435 To advertise the SRLG of the link in the OSPFv2 Extended Link TLV, 436 the same format for the sub-TLV defined in section 1.3 of [RFC4203] 437 is used and TLV type 11 is used. Similarly, for OSPFv3 to advertise 438 the SRLG in the OSPFv3 Router-Link TLV, TLV type 12 is used. 440 7.2. Extended Metrics 442 [RFC3630] defines several link bandwidth types. [RFC7471] defines 443 extended link metrics that are based on link bandwidth, delay and 444 loss characteristics. All of these can be used to compute primary 445 and backup paths within an OSPF area to satisfy requirements for 446 bandwidth, delay (nominal or worst case) or loss. 448 To advertise extended link metrics in the OSPFv2 Extended Link TLV, 449 the same format for the sub-TLVs defined in [RFC7471] is used with 450 the following TLV types: 452 12 - Unidirectional Link Delay 454 13 - Min/Max Unidirectional Link Delay 456 14 - Unidirectional Delay Variation 458 15 - Unidirectional Link Loss 460 16 - Unidirectional Residual Bandwidth 462 17 - Unidirectional Available Bandwidth 464 18 - Unidirectional Utilized Bandwidth 466 To advertise extended link metrics in the OSPFv3 Extended-LSA Router- 467 Link TLV, the same format for the sub-TLVs defined in [RFC7471] is 468 used with the following TLV types: 470 13 - Unidirectional Link Delay 472 14 - Min/Max Unidirectional Link Delay 473 15 - Unidirectional Delay Variation 475 16 - Unidirectional Link Loss 477 17 - Unidirectional Residual Bandwidth 479 18 - Unidirectional Available Bandwidth 481 19 - Unidirectional Utilized Bandwidth 483 7.3. Administrative Group 485 [RFC3630] and [RFC7308] define the Administrative Group and Extended 486 Administrative Group sub-TLVs respectively. 488 To advertise the Administrative Group and Extended Administrative 489 Group in the OSPFv2 Extended Link TLV, the same format for the sub- 490 TLVs defined in [RFC3630] and [RFC7308] is used with the following 491 TLV types: 493 19 - Administrative Group 495 20 - Extended Administrative Group 497 To advertise Administrative Group and Extended Administrative Group 498 in the OSPFv3 Router-Link TLV, the same format for the sub-TLVs 499 defined in [RFC3630] and [RFC7308] is used with the following TLV 500 types: 502 20 - Administrative Group 504 21 - Extended Administrative Group 506 7.4. Traffic Engineering Metric 508 [RFC3630] defines Traffic Engineering Metric. 510 To advertise the Traffic Engineering Metric in the OSPFv2 Extended 511 Link TLV, the same format for the sub-TLV defined in section 2.5.5 of 512 [RFC3630] is used and TLV type 22 is used. Similarly, for OSPFv3 to 513 advertise the Traffic Engineering Metric in the OSPFv3 Router-Link 514 TLV, TLV type 22 is used. 516 8. Maximum Link Bandwidth 518 Maximum link bandwidth is an application independent attribute of the 519 link that is defined in [RFC3630]. Because it is an application 520 independent attribute, it MUST NOT be advertised in ASLA sub-TLV. 522 Instead, it MAY be advertised as a sub-TLV of the Extended Link 523 Opaque LSA Extended Link TLV in OSPFv2 [RFC7684] or sub-TLV of OSPFv3 524 E-Router-LSA Router-Link TLV in OSPFv3 [RFC8362]. 526 To advertise the Maximum link bandwidth in the OSPFv2 Extended Link 527 TLV, the same format for sub-TLV defined in [RFC3630] is used with 528 TLV type 23. 530 To advertise the Maximum link bandwidth in the OSPFv3 Router-Link 531 TLV, the same format for sub-TLV defined in [RFC3630] is used with 532 TLV type 23. 534 9. Considerations for Extended TE Metrics 536 [RFC7471] defines a number of dynamic performance metrics associated 537 with a link. It is conceivable that such metrics could be measured 538 specific to traffic associated with a specific application. 539 Therefore this document includes support for advertising these link 540 attributes specific to a given application. However, in practice it 541 may well be more practical to have these metrics reflect the 542 performance of all traffic on the link regardless of application. In 543 such cases, advertisements for these attributes can be associated 544 with all of the applications utilizing that link. This can be done 545 either by explicitly specifying the applications in the Application 546 Identifier Bit Mask or by using a zero length Application Identifier 547 Bit Mask. 549 10. Local Interface IPv6 Address Sub-TLV 551 The Local Interface IPv6 Address Sub-TLV is an application 552 independent attribute of the link that is defined in [RFC5329]. 553 Because it is an application independent attribute, it MUST NOT be 554 advertised in the ASLA sub-TLV. Instead, it MAY be advertised as a 555 sub-TLV of the OSPFv3 E-Router-LSA Router-Link TLV [RFC8362]. 557 To advertise the Local Interface IPv6 Address Sub-TLV in the OSPFv3 558 Router-Link TLV, the same format for sub-TLV defined in [RFC5329] is 559 used with TLV type 24. 561 11. Remote Interface IPv6 Address Sub-TLV 563 The Remote Interface IPv6 Address Sub-TLV is an application 564 independent attribute of the link that is defined in [RFC5329]. 565 Because it is an application independent attribute, it MUST NOT be 566 advertised in the ASLA sub-TLV. Instead, it MAY be advertised as a 567 sub-TLV of the OSPFv3 E-Router-LSA Router-Link TLV [RFC8362]. 569 To advertise the Remote Interface IPv6 Address Sub-TLV in the OSPFv3 570 Router-Link TLV, the same format for sub-TLV defined in [RFC5329] is 571 used with TLV type 25. 573 12. Attribute Advertisements and Enablement 575 This document defines extensions to support the advertisement of 576 application-specific link attributes. 578 There are applications where the application enablement on the link 579 is relevant - e.g., RSVP-TE - one needs to make sure that RSVP is 580 enabled on the link before sending a RSVP-TE signaling message over 581 it. 583 There are applications where the enablement of the application on the 584 link is irrelevant and has nothing to do with the fact that some link 585 attributes are advertised for the purpose of such application. An 586 example of this is LFA. 588 Whether the presence of link attribute advertisements for a given 589 application indicates that the application is enabled on that link 590 depends upon the application. Similarly, whether the absence of link 591 attribute advertisements indicates that the application is not 592 enabled depends upon the application. 594 In the case of RSVP-TE, the advertisement of application-specific 595 link attributes has no implication of RSVP-TE being enabled on that 596 link. The RSVP-TE enablement is solely derived from the information 597 carried in the OSPFv2 TE Opaque LSA [RFC3630] and OSPFv3 Intra-Area- 598 TE-LSA [RFC5329]. 600 In the case of SR Policy, advertisement of application-specific link 601 attributes does not indicate enablement of SR Policy. The 602 advertisements are only used to support constraints that may be 603 applied when specifying an explicit path. SR Policy is implicitly 604 enabled on all links that are part of the Segment Routing enabled 605 topology independent of the existence of link attribute 606 advertisements 608 In the case of LFA, advertisement of application-specific link 609 attributes does not indicate enablement of LFA on that link. 610 Enablement is controlled by local configuration. 612 If, in the future, additional standard applications are defined to 613 use this mechanism, the specification defining this use MUST define 614 the relationship between application-specific link attribute 615 advertisements and enablement for that application. 617 This document allows the advertisement of application-specific link 618 attributes with no application identifiers i.e., both the Standard 619 Application Identifier Bit Mask and the User Defined Application 620 Identifier Bit Mask are not present (See Section 6). This supports 621 the use of the link attribute by any application. In the presence of 622 an application where the advertisement of link attribute 623 advertisements is used to infer the enablement of an application on 624 that link (e.g., RSVP-TE), the absence of the application identifier 625 leaves ambiguous whether that application is enabled on such a link. 626 This needs to be considered when making use of the "any application" 627 encoding. 629 13. Deployment Considerations 631 13.1. Use of Legacy RSVP-TE LSA Advertisements 633 Bit Identifiers for Standard Applications are defined in Section 6. 634 All of the identifiers defined in this document are associated with 635 applications that were already deployed in some networks prior to the 636 writing of this document. Therefore, such applications have been 637 deployed using the RSVP-TE LSA advertisements. The Standard 638 Applications defined in this document may continue to use RSVP-TE LSA 639 advertisements for a given link so long as at least one of the 640 following conditions is true: 642 The application is RSVP-TE 644 The application is SR Policy or LFA and RSVP-TE is not deployed 645 anywhere in the network 647 The application is SR Policy or LFA, RSVP-TE is deployed in the 648 network, and both the set of links on which SR Policy and/or LFA 649 advertisements are required and the attribute values used by SR 650 Policy and/or LFA on all such links is fully congruent with the 651 links and attribute values used by RSVP-TE 653 Under the conditions defined above, implementations that support the 654 extensions defined in this document have the choice of using RSVP-TE 655 LSA advertisements or application-specific advertisements in support 656 of SR Policy and/or LFA. This will require implementations to 657 provide controls specifying which type of advertisements are to be 658 sent/ processed on receive for these applications. Further 659 discussion of the associated issues can be found in Section 13.2. 661 New applications that future documents define to make use of the 662 advertisements defined in this document MUST NOT make use of RSVP-TE 663 LSA advertisements. This simplifies deployment of new applications 664 by eliminating the need to support multiple ways to advertise 665 attributes for the new applications. 667 13.2. Interoperability, Backwards Compatibility and Migration Concerns 669 Existing deployments of RSVP-TE, SR Policy, and/or LFA utilize the 670 legacy advertisements listed in Section 4. Routers which do not 671 support the extensions defined in this document will only process 672 legacy advertisements and are likely to infer that RSVP-TE is enabled 673 on the links for which legacy advertisements exist. It is expected 674 that deployments using the legacy advertisements will persist for a 675 significant period of time. Therefore deployments using the 676 extensions defined in this document in the presence of routers that 677 do not support these extensions need to be able to interoperate with 678 the use of legacy advertisements by the legacy routers. The 679 following sub-sections discuss interoperability and backwards 680 compatibility concerns for a number of deployment scenarios. 682 13.2.1. Multiple Applications: Common Attributes with RSVP-TE 684 In cases where multiple applications are utilizing a given link, one 685 of the applications is RSVP-TE, and all link attributes for a given 686 link are common to the set of applications utilizing that link, 687 interoperability is achieved by using legacy advertisements for RSVP- 688 TE. Attributes for applications other than RSVP-TE MUST be 689 advertised using application-specific advertisements. This results 690 in duplicate advertisements for those attributes. 692 13.2.2. Multiple Applications: Some Attributes Not Shared with RSVP-TE 694 In cases where one or more applications other than RSVP-TE are 695 utilizing a given link and one or more link attribute values are not 696 shared with RSVP-TE, interoperability is achieved by using legacy 697 advertisements for RSVP-TE. Attributes for applications other than 698 RSVP-TE MUST be advertised using application-specific advertisements. 699 In cases where some link attributes are shared with RSVP-TE, this 700 requires duplicate advertisements for those attributes 702 13.2.3. Interoperability with Legacy Routers 704 For the applications defined in this document, routers that do not 705 support the extensions defined in this document will send and receive 706 only legacy link attribute advertisements. So long as there is any 707 legacy router in the network that has any of the applications 708 enabled, all routers MUST continue to advertise link attributes using 709 legacy advertisements. In addition, the link attribute values 710 associated with the set of applications supported by legacy routers 711 (RSVP-TE, SR Policy, and/or LFA) are always shared since legacy 712 routers have no way of advertising or processing application-specific 713 values. Once all legacy routers have been upgraded, migration from 714 legacy advertisements to application specific advertisements can be 715 achieved via the following steps: 717 1)Send new application-specific advertisements while continuing to 718 advertise using the legacy advertisement (all advertisements are then 719 duplicated). Receiving routers continue to use legacy 720 advertisements. 722 2)Enable the use of the application-specific advertisements on all 723 routers 725 3)Keep legacy advertisements if needed for RSVP-TE purposes. 727 When the migration is complete, it then becomes possible to advertise 728 incongruent values per application on a given link. 730 Documents defining new applications that make use of the application- 731 specific advertisements defined in this document MUST discuss 732 interoperability and backwards compatibility issues that could occur 733 in the presence of routers that do not support the new application. 735 13.2.4. Use of Application-Specific Advertisements for RSVP-TE 737 The extensions defined in this document support RSVP-TE as one of the 738 supported applications. It is however RECOMMENDED to advertise all 739 link-attributes for RSVP-TE in the existing OSPFv2 TE Opaque LSA 740 [RFC3630] and OSPFv3 Intra-Area-TE-LSA [RFC5329] to maintain backward 741 compatibility. RSVP-TE can eventually utilize the application- 742 specific advertisements for newly defined link attributes, that are 743 defined as application-specific. 745 Link attributes that are not allowed to be advertised in the ASLA 746 Sub-TLV, such as Maximum Reservable Link Bandwidth and Unreserved 747 Bandwidth MUST use the OSPFv2 TE Opaque LSA [RFC3630] and OSPFv3 748 Intra-Area-TE-LSA [RFC5329] and MUST NOT be advertised in ASLA Sub- 749 TLV. 751 14. Security Considerations 753 Existing security extensions as described in [RFC2328], [RFC5340] and 754 [RFC8362] apply to extensions defined in this document. While OSPF 755 is under a single administrative domain, there can be deployments 756 where potential attackers have access to one or more networks in the 757 OSPF routing domain. In these deployments, stronger authentication 758 mechanisms such as those specified in [RFC5709], [RFC7474], [RFC4552] 759 or [RFC7166] SHOULD be used. 761 Implementations must assure that malformed TLV and Sub-TLV defined in 762 this document are detected and do not provide a vulnerability for 763 attackers to crash the OSPF router or routing process. Reception of 764 a malformed TLV or Sub-TLV SHOULD be counted and/or logged for 765 further analysis. Logging of malformed TLVs and Sub-TLVs SHOULD be 766 rate-limited to prevent a Denial of Service (DoS) attack (distributed 767 or otherwise) from overloading the OSPF control plane. 769 This document defines a new way to advertise link attributes. 770 Tampering with the information defined in this document may have an 771 effect on applications using it, including impacting Traffic 772 Engineering that uses various link attributes for its path 773 computation. This is similar in nature to the impacts associated 774 with (for example) [RFC3630]. As the advertisements defined in this 775 document limit the scope to specific applications, the impact of 776 tampering is similarly limited in scope. 778 15. IANA Considerations 780 This specifications updates two existing registries: 782 - OSPFv2 Extended Link TLV Sub-TLVs Registry 784 - OSPFv3 Extended-LSA Sub-TLV Registry 786 New values are allocated using the IETF Review procedure as described 787 in [RFC5226]. 789 15.1. OSPFv2 791 The OSPFv2 Extended Link TLV Sub-TLVs Registry [RFC7684] defines sub- 792 TLVs at any level of nesting for OSPFv2 Extended Link TLVs. IANA has 793 assigned the following Sub-TLV types from the OSPFv2 Extended Link 794 TLV Sub-TLVs Registry: 796 10 - Application-Specific Link Attributes 798 11 - Shared Risk Link Group 800 12 - Unidirectional Link Delay 802 13 - Min/Max Unidirectional Link Delay 804 14 - Unidirectional Delay Variation 806 15 - Unidirectional Link Loss 808 16 - Unidirectional Residual Bandwidth 809 17 - Unidirectional Available Bandwidth 811 18 - Unidirectional Utilized Bandwidth 813 19 - Administrative Group 815 20 - Extended Administrative Group 817 22 - TE Metric 819 23 - Maximum Link Bandwidth 821 15.2. OSPFv3 823 The OSPFv3 Extended-LSA Sub-TLV Registry [RFC8362] defines sub-TLVs 824 at any level of nesting for OSPFv3 Extended LSAs. IANA has assigned 825 the following Sub-TLV types from the OSPFv3 Extended-LSA Sub-TLV 826 Registry: 828 11 - Application-Specific Link Attributes 830 12 - Shared Risk Link Group 832 13 - Unidirectional Link Delay 834 14 - Min/Max Unidirectional Link Delay 836 15 - Unidirectional Delay Variation 838 16 - Unidirectional Link Loss 840 17 - Unidirectional Residual Bandwidth 842 18 - Unidirectional Available Bandwidth 844 19 - Unidirectional Utilized Bandwidth 846 20 - Administrative Group 848 21 - Extended Administrative Group 850 22 - TE Metric 852 23 - Maximum Link Bandwidth 854 24 - Local Interface IPv6 Address Sub-TLV 856 25 - Remote Interface IPv6 Address Sub-TLV 858 16. Contributors 860 The following people contributed to the content of this document and 861 should be considered as co-authors: 863 Acee Lindem 864 Cisco Systems 865 301 Midenhall Way 866 Cary, NC 27513 867 USA 869 Email: acee@cisco.com 871 Ketan Talaulikar 872 Cisco Systems, Inc. 873 India 875 Email: ketant@cisco.com 877 Hannes Gredler 878 RtBrick Inc. 879 Austria 881 Email: hannes@rtbrick.com 883 17. Acknowledgments 885 Thanks to Chris Bowers for his review and comments. 887 Thanks to Alvaro Retana for his detailed review and comments. 889 18. References 891 18.1. Normative References 893 [I-D.ietf-isis-te-app] 894 Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and 895 J. Drake, "IS-IS Application-Specific Link Attributes", 896 draft-ietf-isis-te-app-19 (work in progress), June 2020. 898 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 899 Requirement Levels", BCP 14, RFC 2119, 900 DOI 10.17487/RFC2119, March 1997, 901 . 903 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 904 DOI 10.17487/RFC2328, April 1998, 905 . 907 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 908 (TE) Extensions to OSPF Version 2", RFC 3630, 909 DOI 10.17487/RFC3630, September 2003, 910 . 912 [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in 913 Support of Generalized Multi-Protocol Label Switching 914 (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005, 915 . 917 [RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed., 918 "Traffic Engineering Extensions to OSPF Version 3", 919 RFC 5329, DOI 10.17487/RFC5329, September 2008, 920 . 922 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 923 for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, 924 . 926 [RFC7308] Osborne, E., "Extended Administrative Groups in MPLS 927 Traffic Engineering (MPLS-TE)", RFC 7308, 928 DOI 10.17487/RFC7308, July 2014, 929 . 931 [RFC7471] Giacalone, S., Ward, D., Drake, J., Atlas, A., and S. 932 Previdi, "OSPF Traffic Engineering (TE) Metric 933 Extensions", RFC 7471, DOI 10.17487/RFC7471, March 2015, 934 . 936 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 937 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 938 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 939 2015, . 941 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 942 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 943 May 2017, . 945 [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and 946 F. Baker, "OSPFv3 Link State Advertisement (LSA) 947 Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 948 2018, . 950 18.2. Informative References 952 [I-D.ietf-spring-segment-routing-policy] 953 Filsfils, C., Sivabalan, S., Voyer, D., Bogdanov, A., and 954 P. Mattes, "Segment Routing Policy Architecture", draft- 955 ietf-spring-segment-routing-policy-07 (work in progress), 956 May 2020. 958 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 959 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 960 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 961 . 963 [RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality 964 for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006, 965 . 967 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 968 IANA Considerations Section in RFCs", RFC 5226, 969 DOI 10.17487/RFC5226, May 2008, 970 . 972 [RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for 973 IP Fast Reroute: Loop-Free Alternates", RFC 5286, 974 DOI 10.17487/RFC5286, September 2008, 975 . 977 [RFC5709] Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M., 978 Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic 979 Authentication", RFC 5709, DOI 10.17487/RFC5709, October 980 2009, . 982 [RFC5714] Shand, M. and S. Bryant, "IP Fast Reroute Framework", 983 RFC 5714, DOI 10.17487/RFC5714, January 2010, 984 . 986 [RFC7166] Bhatia, M., Manral, V., and A. Lindem, "Supporting 987 Authentication Trailer for OSPFv3", RFC 7166, 988 DOI 10.17487/RFC7166, March 2014, 989 . 991 [RFC7474] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed., 992 "Security Extension for OSPFv2 When Using Manual Key 993 Management", RFC 7474, DOI 10.17487/RFC7474, April 2015, 994 . 996 Authors' Addresses 998 Peter Psenak (editor) 999 Cisco Systems 1000 Eurovea Centre, Central 3 1001 Pribinova Street 10 1002 Bratislava 81109 1003 Slovakia 1005 Email: ppsenak@cisco.com 1007 Les Ginsberg 1008 Cisco Systems 1009 821 Alder Drive 1010 MILPITAS, CA 95035 1011 USA 1013 Email: ginsberg@cisco.com 1015 Wim Henderickx 1016 Nokia 1017 Copernicuslaan 50 1018 Antwerp, 2018 94089 1019 Belgium 1021 Email: wim.henderickx@nokia.com 1023 Jeff Tantsura 1024 Apstra 1025 US 1027 Email: jefftant.ietf@gmail.com 1029 John Drake 1030 Juniper Networks 1031 1194 N. Mathilda Ave 1032 Sunnyvale, California 94089 1033 USA 1035 Email: jdrake@juniper.net