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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-19) exists of draft-ietf-isis-te-app-13 == Outdated reference: A later version (-22) exists of draft-ietf-spring-segment-routing-policy-07 Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). 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: November 20, 2020 W. Henderickx 6 Nokia 7 J. Tantsura 8 Apstra 9 J. Drake 10 Juniper Networks 11 May 19, 2020 13 OSPF Link Traffic Engineering Attribute Reuse 14 draft-ietf-ospf-te-link-attr-reuse-12.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 Traffic Engineering, Loop Free Alternate) have been 22 defined which also make use of the link attribute advertisements. In 23 cases where multiple applications wish to make use of these link 24 attributes the current advertisements do not support application 25 specific values for a given attribute nor do they support indication 26 of which applications are using the advertised value for a given 27 link. This document introduces new link attribute advertisements in 28 OSPFv2 and OSPFv3 which 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 November 20, 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 . . . . . . . . . . . . . . . . . . 8 71 6.1. Shared Risk Link Group (SRLG) . . . . . . . . . . . . . . 8 72 6.2. Extended Metrics . . . . . . . . . . . . . . . . . . . . 8 73 6.3. Administrative Group . . . . . . . . . . . . . . . . . . 9 74 6.4. Traffic Engineering Metric . . . . . . . . . . . . . . . 10 75 7. Maximum Link Bandwidth . . . . . . . . . . . . . . . . . . . 10 76 8. Considerations for Extended TE Metrics . . . . . . . . . . . 10 77 9. Local Interface IPv6 Address Sub-TLV . . . . . . . . . . . . 11 78 10. Remote Interface IPv6 Address Sub-TLV . . . . . . . . . . . . 11 79 11. Attribute Advertisements and Enablement . . . . . . . . . . . 11 80 12. Deployment Considerations . . . . . . . . . . . . . . . . . . 12 81 12.1. Use of Legacy RSVP-TE LSA Advertisements . . . . . . . . 12 82 12.2. Use of Zero Length Application Identifier Bit Masks . . 13 83 12.3. Interoperability, Backwards Compatibility and Migration 84 Concerns . . . . . . . . . . . . . . . . . . . . . . . . 13 85 12.3.1. Multiple Applications: Common Attributes with RSVP- 86 TE . . . . . . . . . . . . . . . . . . . . . . . . . 13 87 12.3.2. Multiple Applications: Some Attributes Not Shared 88 with RSVP-TE . . . . . . . . . . . . . . . . . . . . 14 89 12.3.3. Interoperability with Legacy Routers . . . . . . . . 14 90 12.3.4. Use of Application Specific Advertisements for RSVP- 91 TE . . . . . . . . . . . . . . . . . . . . . . . . . 15 92 13. Security Considerations . . . . . . . . . . . . . . . . . . . 15 93 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 94 14.1. OSPFv2 . . . . . . . . . . . . . . . . . . . . . . . . . 16 95 14.2. OSPFv3 . . . . . . . . . . . . . . . . . . . . . . . . . 16 96 15. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 17 97 16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18 98 17. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 99 17.1. Normative References . . . . . . . . . . . . . . . . . . 18 100 17.2. Informative References . . . . . . . . . . . . . . . . . 19 101 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 103 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 115 which makes use of link attribute advertisements - examples of which 116 are listed in Section 5. 118 In recent years new applications have been introduced which have use 119 cases for many of the link attributes historically used by RSVP-TE. 120 Such applications include Segment Routing Traffic Engineering (SRTE) 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 SRTE support (for 124 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 SRTE. If the topologies are fully congruent this may 127 not be an issue, but any incongruence leads to ambiguity. 129 An additional issue arises in cases where both applications are 130 supported on a link but the link attribute values associated with 131 each application differ. Current advertisements do not support 132 advertising application specific values for the same attribute on a 133 specific link. 135 This document defines extensions which address these issues. Also, 136 as evolution of use cases for link attributes can be expected to 137 continue in the years to come, this document defines a solution which 138 is easily extensible for the introduction of new applications and new 139 use cases. 141 2. Requirements Language 143 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 144 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 145 "OPTIONAL" in this document are to be interpreted as described in BCP 146 14 [RFC2119] [RFC8174] when, and only when, they appear in all 147 capitals, as shown here. 149 3. Existing Advertisement of Link Attributes 151 There are existing advertisements used in support of RSVP-TE. These 152 advertisements are carried in the OSPFv2 TE Opaque LSA [RFC3630] and 153 OSPFv3 Intra-Area-TE-LSA [RFC5329]. Additional RSVP-TE link 154 attributes have been defined by [RFC4203], [RFC7308] and [RFC7471]. 156 Extended Link Opaque LSAs as defined in [RFC7684] for OSPFv2 and 157 Extended Router-LSAs [RFC8362] for OSPFv3 are used to advertise link 158 attributes that are used by applications other then RSVP-TE or GMPLS. 159 These LSAs were defined as a generic containers for distribution of 160 the extended link attributes. 162 4. Advertisement of Link Attributes 164 This section outlines the solution for advertising link attributes 165 originally defined for RSVP-TE or GMPLS when they are used for other 166 applications. 168 4.1. OSPFv2 Extended Link Opaque LSA and OSPFv3 E-Router-LSA 170 Advantages of Extended Link Opaque LSAs as defined in [RFC7684] for 171 OSPFv2 and Extended Router-LSAs [RFC8362] for OSPFv3 when used for 172 advertisement of link attributes originally defined for RSVP-TE or 173 GMPLS: 175 1. Advertisement of the link attributes does not make the link part 176 of the RSVP-TE topology. It avoids any conflicts and is fully 177 compatible with [RFC3630] and [RFC5329]. 179 2. The OSPFv2 TE Opaque LSA and OSPFv3 Intra-Area-TE-LSA remains 180 truly opaque to OSPFv2 and OSPFv3 as originally defined in 181 [RFC3630] and [RFC5329] respectively. Their contents are not 182 inspected by OSPF, that acts as a pure transport. 184 3. There is a clear distinction between link attributes used by 185 RSVP-TE and link attributes used by other OSPFv2 or OSPFv3 186 applications. 188 4. All link attributes that are used by other applications are 189 advertised in a single LSA, the Extended Link Opaque LSA in 190 OSPFv2 or the OSPFv3 E-Router-LSA [RFC8362] in OSPFv3. 192 The disadvantage of this approach is that in rare cases, the same 193 link attribute is advertised in both the TE Opaque and Extended Link 194 Attribute LSAs in OSPFv2 or the Intra-Area-TE-LSA and E-Router-LSA in 195 OSPFv3. 197 Extended Link Opaque LSA [RFC7684] and E-Router-LSA [RFC8362] are 198 used to advertise any link attributes used for non-RSVP-TE 199 applications in OSPFv2 or OSPFv3 respectively, including those that 200 have been originally defined for RSVP-TE applications (See 201 Section 6). 203 TE link attributes used for RSVP-TE/GMPLS continue to use OSPFv2 TE 204 Opaque LSA [RFC3630] and OSPFv3 Intra-Area-TE-LSA [RFC5329]. 206 The format of the link attribute TLVs that have been defined for 207 RSVP-TE applications will be kept unchanged even when they are used 208 for non-RSVP-TE applications. Unique code points are allocated for 209 these link attribute TLVs from the OSPFv2 Extended Link TLV Sub-TLV 210 Registry [RFC7684] and from the OSPFv3 Extended LSA Sub-TLV Registry 211 [RFC8362], as specified in Section 14. 213 5. Advertisement of Application Specific Values 215 To allow advertisement of the application specific values of the link 216 attribute, a new Application Specific Link Attributes (ASLA) sub-TLV 217 is defined. The ASLA sub-TLV is a sub-TLV of the OSPFv2 Extended 218 Link TLV [RFC7684] and OSPFv3 Router-Link TLV [RFC8362]. 220 The ASLA sub-TLV is an optional sub-TLV and can appear multiple times 221 in the OSPFv2 Extended Link TLV and OSPFv3 Router-Link TLV. The ASLA 222 sub-TLV MUST be used for advertisement of the link attributes listed 223 at the end on this section if these are advertised inside OSPFv2 224 Extended Link TLV and OSPFv3 Router-Link TLV. It has the following 225 format: 227 0 1 2 3 228 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 1 229 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 230 | Type | Length | 231 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 232 | SABM Length | UDABM Length | Reserved | 233 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 234 | Standard Application Identifier Bit Mask | 235 +- -+ 236 | ... | 237 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 238 | User Defined Application Identifier Bit Mask | 239 +- -+ 240 | ... | 241 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 242 | Link Attribute sub-sub-TLVs | 243 +- -+ 244 | ... | 246 where: 248 Type: 10 (OSPFv2), 11 (OSPFv3) 250 Length: variable 252 SABM Length: Standard Application Identifier Bit Mask Length in 253 octets. The value MUST be 0, 4 or 8. If the Standard Application 254 Bit Mask is not present, the Standard Application Bit Mask Length 255 MUST be set to 0. 257 UDABM Length: User Defined Application Identifier Bit Mask Length 258 in octets. The legal values are 0, 4 or 8. If the User Defined 259 Application Bit Mask is not present, the User Defined Application 260 Bit Mask Length MUST be set to 0. 262 Standard Application Identifier Bit Mask: Optional set of bits, 263 where each bit represents a single standard application. Bits are 264 defined in [I-D.ietf-isis-te-app]. The bits are repeated here for 265 informational purpose: 267 Bit-0 (R-bit): RSVP-TE 269 Bit-1 (S-bit): Segment Routing TE 271 Bit-2 (F-bit): Loop Free Alternate (LFA). Includes all LFA 272 types 274 User Defined Application Identifier Bit Mask: Optional set of 275 bits, where each bit represents a single user defined application. 277 If the SABM or UDABM length is other than 0, 4, or 8, the ASLA sub- 278 TLV MUST be ignored by the receiver. 280 Standard Application Identifier Bits are defined/sent starting with 281 Bit 0. Undefined bits MUST be transmitted as 0 and MUST be ignored 282 on receipt. Bits that are NOT transmitted MUST be treated as if they 283 are set to 0 on receipt. Bits that are not supported by an 284 implementation MUST be ignored on receipt. 286 User Defined Application Identifier Bits have no relationship to 287 Standard Application Identifier Bits and are NOT managed by IANA or 288 any other standards body. It is recommended that bits are used 289 starting with Bit 0 so as to minimize the number of octets required 290 to advertise all UDAs. 292 If the link attribute advertisement is limited to be used by a 293 specific set of applications, corresponding Bit Masks MUST be present 294 and application specific bit(s) MUST be set for all applications that 295 use the link attributes advertised in the ASLA sub-TLV. 297 Application Bit Masks apply to all link attributes that support 298 application specific values and are advertised in the ASLA sub-TLV. 300 The advantage of not making the Application Bit Masks part of the 301 attribute advertisement itself is that the format of any previously 302 defined link attributes can be kept and reused when advertising them 303 in the ASLA sub-TLV. 305 If the same attribute is advertised in more than single ASLA sub-TLVs 306 with the application listed in the Application Bit Masks, the 307 application SHOULD use the first instance of advertisement and ignore 308 any subsequent advertisements of that attribute. 310 This document defines the initial set of link attributes that MUST 311 use the ASLA sub-TLV if advertised in the OSPFv2 Extended Link TLV or 312 in the OSPFv3 Router-Link TLV. Documents which define new link 313 attributes MUST state whether the new attributes support application 314 specific values and as such MUST be advertised in an ASLA sub-TLV. 315 The link attributes that MUST be advertised in ASLA sub-TLVs are: 317 - Shared Risk Link Group [RFC4203] 319 - Unidirectional Link Dela [RFC7471] 321 - Min/Max Unidirectional Link Delay [RFC7471] 322 - Unidirectional Delay Variation [RFC7471] 324 - Unidirectional Link Loss [RFC7471] 326 - Unidirectional Residual Bandwidth [RFC7471] 328 - Unidirectional Available Bandwidth [RFC7471] 330 - Unidirectional Utilized Bandwidth [RFC7471] 332 - Administrative Group [RFC3630] 334 - Extended Administrative Group [RFC7308] 336 - TE Metric [RFC3630] 338 6. Reused TE link attributes 340 This section defines the use case and indicates the code points 341 (Section 14) from the OSPFv2 Extended Link TLV Sub-TLV Registry and 342 OSPFv3 Extended LSA Sub-TLV Registry for some of the link attributes 343 that have been originally defined for RSVP-TE or GMPLS. 345 6.1. Shared Risk Link Group (SRLG) 347 The SRLG of a link can be used in OSPF calculated IPFRR [RFC5714] to 348 compute a backup path that does not share any SRLG group with the 349 protected link. 351 To advertise the SRLG of the link in the OSPFv2 Extended Link TLV, 352 the same format for the sub-TLV defined in section 1.3 of [RFC4203] 353 is used and TLV type 11 is used. Similarly, for OSPFv3 to advertise 354 the SRLG in the OSPFv3 Router-Link TLV, TLV type 12 is used. 356 6.2. Extended Metrics 358 [RFC3630] defines several link bandwidth types. [RFC7471] defines 359 extended link metrics that are based on link bandwidth, delay and 360 loss characteristics. All these can be used to compute primary and 361 backup paths within an OSPF area to satisfy requirements for 362 bandwidth, delay (nominal or worst case) or loss. 364 To advertise extended link metrics in the OSPFv2 Extended Link TLV, 365 the same format for the sub-TLVs defined in [RFC7471] is used with 366 the following TLV types: 368 12 - Unidirectional Link Delay 369 13 - Min/Max Unidirectional Link Delay 371 14 - Unidirectional Delay Variation 373 15 - Unidirectional Link Loss 375 16 - Unidirectional Residual Bandwidth 377 17 - Unidirectional Available Bandwidth 379 18 - Unidirectional Utilized Bandwidth 381 To advertise extended link metrics in the OSPFv3 Extended LSA Router- 382 Link TLV, the same format for the sub-TLVs defined in [RFC7471] is 383 used with the following TLV types: 385 13 - Unidirectional Link Delay 387 14 - Min/Max Unidirectional Link Delay 389 15 - Unidirectional Delay Variation 391 16 - Unidirectional Link Loss 393 17 - Unidirectional Residual Bandwidth 395 18 - Unidirectional Available Bandwidth 397 19 - Unidirectional Utilized Bandwidth 399 6.3. Administrative Group 401 [RFC3630] and [RFC7308] define the Administrative Group and Extended 402 Administrative Group sub-TLVs respectively. 404 To advertise the Administrative Group and Extended Administrative 405 Group in the OSPFv2 Extended Link TLV, the same format for the sub- 406 TLVs defined in [RFC3630] and [RFC7308] is used with the following 407 TLV types: 409 19 - Administrative Group 411 20 - Extended Administrative Group 413 To advertise Administrative Group and Extended Administrative Group 414 in the OSPFv3 Router-Link TLV, the same format for the sub-TLVs 415 defined in [RFC3630] and [RFC7308] is used with the following TLV 416 types: 418 20 - Administrative Group 420 21 - Extended Administrative Group 422 6.4. Traffic Engineering Metric 424 [RFC3630] defines Traffic Engineering Metric. 426 To advertise the Traffic Engineering Metric in the OSPFv2 Extended 427 Link TLV, the same format for the sub-TLV defined in section 2.5.5 of 428 [RFC3630] is used and TLV type 22 is used. Similarly, for OSPFv3 to 429 advertise the Traffic Engineering Metric in the OSPFv3 Router-Link 430 TLV, TLV type 22 is used. 432 7. Maximum Link Bandwidth 434 Maximum link bandwidth is an application independent attribute of the 435 link that is defined in [RFC3630]. Because it is an application 436 independent attribute, it MUST NOT be advertised in ASLA sub-TLV. 437 Instead, it MAY be advertised as a sub-TLV of the Extended Link 438 Opaque LSA Extended Link TLV in OSPFv2 [RFC7684] or sub-TLV of OSPFv3 439 E-Router-LSA Router-Link TLV in OSPFv3 [RFC8362]. 441 To advertise the Maximum link bandwidth in the OSPFv2 Extended Link 442 TLV, the same format for sub-TLV defined in [RFC3630] is used with 443 TLV type 23. 445 To advertise the Maximum link bandwidth in the OSPFv3 Router-Link 446 TLV, the same format for sub-TLV defined in [RFC3630] is used with 447 TLV type 23. 449 8. Considerations for Extended TE Metrics 451 [RFC7471] defines a number of dynamic performance metrics associated 452 with a link. It is conceivable that such metrics could be measured 453 specific to traffic associated with a specific application. 454 Therefore this document includes support for advertising these link 455 attributes specific to a given application. However, in practice it 456 may well be more practical to have these metrics reflect the 457 performance of all traffic on the link regardless of application. In 458 such cases, advertisements for these attributes can be associated 459 with all of the applications utilizing that link. This can be done 460 either by explicitly specifying the applications in the Application 461 Identifier Bit Mask or by using a zero length Application Identifier 462 Bit Mask. 464 9. Local Interface IPv6 Address Sub-TLV 466 The Local Interface IPv6 Address Sub-TLV is an application 467 independent attribute of the link that is defined in [RFC5329]. 468 Because it is an application independent attribute, it MUST NOT be 469 advertised in the ASLA sub-TLV. Instead, it MAY be advertised as a 470 sub-TLV of the OSPFv3 E-Router-LSA Router-Link TLV [RFC8362]. 472 To advertise the Local Interface IPv6 Address Sub-TLV in the OSPFv3 473 Router-Link TLV, the same format for sub-TLV defined in [RFC5329] is 474 used with TLV type 24. 476 10. Remote Interface IPv6 Address Sub-TLV 478 The Remote Interface IPv6 Address Sub-TLV is an application 479 independent attribute of the link that is defined in [RFC5329]. 480 Because it is an application independent attribute, it MUST NOT be 481 advertised in the ASLA sub-TLV. Instead, it MAY be advertised as a 482 sub-TLV of the OSPFv3 E-Router-LSA Router-Link TLV [RFC8362]. 484 To advertise the Remote Interface IPv6 Address Sub-TLV in the OSPFv3 485 Router-Link TLV, the same format for sub-TLV defined in [RFC5329] is 486 used with TLV type 25. 488 11. Attribute Advertisements and Enablement 490 This document defines extensions to support the advertisement of 491 application specific link attributes. 493 Whether the presence of link attribute advertisements for a given 494 application indicates that the application is enabled on that link 495 depends upon the application. Similarly, whether the absence of link 496 attribute advertisements indicates that the application is not 497 enabled depends upon the application. 499 In the case of RSVP-TE, the advertisement of application specific 500 link attributes has no implication of RSVP-TE being enabled on that 501 link. The RSVP-TE enablement is solely derived from the information 502 carried in the OSPFv2 TE Opaque LSA [RFC3630] and OSPFv3 Intra-Area- 503 TE-LSA [RFC5329]. 505 In the case of SRTE, advertisement of application specific link 506 attributes does NOT indicate enablement of SRTE. The advertisements 507 are only used to support constraints which may be applied when 508 specifying an explicit path. SRTE is implicitly enabled on all links 509 which are part of the Segment Routing enabled topology independent of 510 the existence of link attribute advertisements 511 In the case of LFA, advertisement of application specific link 512 attributes does NOT indicate enablement of LFA on that link. 513 Enablement is controlled by local configuration. 515 If, in the future, additional standard applications are defined to 516 use this mechanism, the specification defining this use MUST define 517 the relationship between application specific link attribute 518 advertisements and enablement for that application. 520 This document allows the advertisement of application specific link 521 attributes with no application identifiers i.e., both the Standard 522 Application Identifier Bit Mask and the User Defined Application 523 Identifier Bit Mask are not present (See Section 5). This supports 524 the use of the link attribute by any application. In the presence of 525 an application where the advertisement of link attribute 526 advertisements is used to infer the enablement of an application on 527 that link (e.g., RSVP-TE), the absence of the application identifier 528 leaves ambiguous whether that application is enabled on such a link. 529 This needs to be considered when making use of the "any application" 530 encoding. 532 12. Deployment Considerations 534 12.1. Use of Legacy RSVP-TE LSA Advertisements 536 Bit Identifiers for Standard Applications are defined in Section 5. 537 All of the identifiers defined in this document are associated with 538 applications which were already deployed in some networks prior to 539 the writing of this document. Therefore, such applications have been 540 deployed using the RSVP-TE LSA advertisements. The Standard 541 Applications defined in this document may continue to use RSVP-TE LSA 542 advertisements for a given link so long as at least one of the 543 following conditions is true: 545 The application is RSVP-TE 547 The application is SRTE or LFA and RSVP-TE is not deployed 548 anywhere in the network 550 The application is SRTE or LFA, RSVP-TE is deployed in the 551 network, and both the set of links on which SRTE and/or LFA 552 advertisements are required and the attribute values used by SRTE 553 and/or LFA on all such links is fully congruent with the links and 554 attribute values used by RSVP-TE 556 Under the conditions defined above, implementations which support the 557 extensions defined in this document have the choice of using RSVP-TE 558 LSA advertisements or application specific advertisements in support 559 of SRTE and/or LFA. This will require implementations to provide 560 controls specifying which type of advertisements are to be sent/ 561 processed on receive for these applications. Further discussion of 562 the associated issues can be found in Section 12.3. 564 New applications which future documents define to make use of the 565 advertisements defined in this document MUST NOT make use of RSVP-TE 566 LSA advertisements. This simplifies deployment of new applications 567 by eliminating the need to support multiple ways to advertise 568 attributes for the new applications. 570 12.2. Use of Zero Length Application Identifier Bit Masks 572 If link attributes are advertised associated with zero length 573 Application Identifier Bit Masks for both standard applications and 574 user defined applications, then any Standard Application and/or any 575 User Defined Application is permitted to use that set of link 576 attributes so long as there is not another set of attributes 577 advertised on that same link which is associated with a non-zero 578 length Application Identifier Bit Mask with a matching Application 579 Identifier Bit set. If support for a new application is introduced 580 on any node in a network in the presence of such advertisements, 581 these advertisements are permitted to be used by the new application. 582 If this is not what is intended, then existing advertisements MUST be 583 readvertised with an explicit set of applications specified before a 584 new application is introduced. 586 12.3. Interoperability, Backwards Compatibility and Migration Concerns 588 Existing deployments of RSVP-TE, SRTE, and/or LFA utilize the legacy 589 advertisements listed in Section 3. Routers which do not support the 590 extensions defined in this document will only process legacy 591 advertisements and are likely to infer that RSVP-TE is enabled on the 592 links for which legacy advertisements exist. It is expected that 593 deployments using the legacy advertisements will persist for a 594 significant period of time. Therefore deployments using the 595 extensions defined in this document must be able to co-exist with use 596 of the legacy advertisements by routers which do not support the 597 extensions defined in this document. The following sub-sections 598 discuss interoperability and backwards compatibility concerns for a 599 number of deployment scenarios. 601 12.3.1. Multiple Applications: Common Attributes with RSVP-TE 603 In cases where multiple applications are utilizing a given link, one 604 of the applications is RSVP-TE, and all link attributes for a given 605 link are common to the set of applications utilizing that link, 606 interoperability is achieved by using legacy advertisements for RSVP- 607 TE. Attributes for applications other than RSVP-TE MUST be 608 advertised using application specific advertisements. This results 609 in duplicate advertisements for those attributes. 611 12.3.2. Multiple Applications: Some Attributes Not Shared with RSVP-TE 613 In cases where one or more applications other than RSVP-TE are 614 utilizing a given link and one or more link attribute values are NOT 615 shared with RSVP-TE, interoperability is achieved by using legacy 616 advertisements for RSVP-TE. Attributes for applications other than 617 RSVP-TE MUST be advertised using application specific advertisements. 618 In cases where some link attributes are shared with RSVP-TE, this 619 requires duplicate advertisements for those attributes 621 12.3.3. Interoperability with Legacy Routers 623 For the applications defined in this document, routers which do not 624 support the extensions defined in this document will send and receive 625 only legacy link attribute advertisements. So long as there is any 626 legacy router in the network which has any of the applications 627 enabled, all routers MUST continue to advertise link attributes using 628 legacy advertisements. In addition, the link attribute values 629 associated with the set of applications supported by legacy routers 630 (RSVP-TE, SRTE, and/or LFA) are always shared since legacy routers 631 have no way of advertising or processing application specific values. 632 Once all legacy routers have been upgraded, migration from legacy 633 advertisements to application specific advertisements can be achieved 634 via the following steps: 636 1)Send application specific advertisements while continuing to 637 advertise using legacy (all advertisements are then duplicated). 638 Receiving routers continue to use legacy advertisements. 640 2)Enable the use of the application specific advertisements on all 641 routers 643 3)Keep legacy advertisements if needed for RSVP-TE purposes. 645 When the migration is complete, it then becomes possible to advertise 646 incongruent values per application on a given link. 648 Documents defining new applications which make use of the application 649 specific advertisements defined in this document MUST discuss 650 interoperability and backwards compatibility issues that could occur 651 in the presence of routers which do not support the new application. 653 12.3.4. Use of Application Specific Advertisements for RSVP-TE 655 The extensions defined in this document support RSVP-TE as one of the 656 supported applications. It is however RECOMMENDED to advertise all 657 link-attributes for RSVP-TE in the existing OSPFv2 TE Opaque LSA 658 [RFC3630] and OSPFv3 Intra-Area-TE-LSA [RFC5329] to maintain backward 659 compatibility. RSVP-TE can eventually utilize the application 660 specific advertisements for newly defined link attributes, which are 661 defined as application specific. 663 Link attributes that are NOT allowed to be advertised in the ASLA 664 Sub-TLV, such as Maximum Reservable Link Bandwidth and Unreserved 665 Bandwidth MUST use the OSPFv2 TE Opaque LSA [RFC3630] and OSPFv3 666 Intra-Area-TE-LSA [RFC5329] and MUST NOT be advertised in ASLA Sub- 667 TLV. 669 13. Security Considerations 671 Existing security extensions as described in [RFC2328], [RFC5340] and 672 [RFC8362] apply to extensions defined in this document. While OSPF 673 is under a single administrative domain, there can be deployments 674 where potential attackers have access to one or more networks in the 675 OSPF routing domain. In these deployments, stronger authentication 676 mechanisms such as those specified in [RFC5709], [RFC7474], [RFC4552] 677 or [RFC7166] SHOULD be used. 679 Implementations must assure that malformed TLV and Sub-TLV defined in 680 this document are detected and do not provide a vulnerability for 681 attackers to crash the OSPF router or routing process. Reception of 682 a malformed TLV or Sub-TLV SHOULD be counted and/or logged for 683 further analysis. Logging of malformed TLVs and Sub-TLVs SHOULD be 684 rate-limited to prevent a Denial of Service (DoS) attack (distributed 685 or otherwise) from overloading the OSPF control plane. 687 This document defines a new way to advertise link attributes. 688 Tampering with the information defined in this document may have an 689 effect on applications using it, including impacting Traffic 690 Engineering. This is similar in nature to the impacts associated 691 with (for example) [RFC3630]. As the advertisements defined in this 692 document limit the scope to specific applications, the impact of 693 tampering is similarly limited in scope. 695 14. IANA Considerations 696 14.1. OSPFv2 698 The OSPFv2 Extended Link TLV Sub-TLVs registry [RFC7684] defines sub- 699 TLVs at any level of nesting for OSPFv2 Extended Link TLVs. IANA has 700 assigned the following Sub-TLV types from the OSPFv2 Extended Link 701 TLV Sub-TLVs Registry: 703 10 - Application Specific Link Attributes 705 11 - Shared Risk Link Group 707 12 - Unidirectional Link Delay 709 13 - Min/Max Unidirectional Link Delay 711 14 - Unidirectional Delay Variation 713 15 - Unidirectional Link Loss 715 16 - Unidirectional Residual Bandwidth 717 17 - Unidirectional Available Bandwidth 719 18 - Unidirectional Utilized Bandwidth 721 19 - Administrative Group 723 20 - Extended Administrative Group 725 22 - TE Metric 727 23 - Maximum Link Bandwidth 729 14.2. OSPFv3 731 The OSPFv3 Extended LSA Sub-TLV Registry [RFC8362] defines sub-TLVs 732 at any level of nesting for OSPFv3 Extended LSAs. IANA has assigned 733 the following Sub-TLV types from the OSPFv3 Extended LSA Sub-TLV 734 Registry: 736 11 - Application Specific Link Attributes 738 12 - Shared Risk Link Group 740 13 - Unidirectional Link Delay 742 14 - Min/Max Unidirectional Link Delay 743 15 - Unidirectional Delay Variation 745 16 - Unidirectional Link Loss 747 16 - Unidirectional Residual Bandwidth 749 18 - Unidirectional Available Bandwidth 751 19 - Unidirectional Utilized Bandwidth 753 20 - Administrative Group 755 21 - Extended Administrative Group 757 22 - TE Metric 759 23 - Maximum Link Bandwidth 761 24 - Local Interface IPv6 Address Sub-TLV 763 25 - Remote Interface IPv6 Address Sub-TLV 765 15. Contributors 767 The following people contributed to the content of this document and 768 should be considered as co-authors: 770 Acee Lindem 771 Cisco Systems 772 301 Midenhall Way 773 Cary, NC 27513 774 USA 776 Email: acee@cisco.com 778 Ketan Talaulikar 779 Cisco Systems, Inc. 780 India 782 Email: ketant@cisco.com 784 Hannes Gredler 785 RtBrick Inc. 786 Austria 788 Email: hannes@rtbrick.com 790 16. Acknowledgments 792 Thanks to Chris Bowers for his review and comments. 794 Thanks to Alvaro Retana for his detailed review and comments. 796 17. References 798 17.1. Normative References 800 [I-D.ietf-isis-te-app] 801 Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and 802 J. Drake, "IS-IS TE Attributes per application", draft- 803 ietf-isis-te-app-13 (work in progress), May 2020. 805 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 806 Requirement Levels", BCP 14, RFC 2119, 807 DOI 10.17487/RFC2119, March 1997, 808 . 810 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 811 DOI 10.17487/RFC2328, April 1998, 812 . 814 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 815 (TE) Extensions to OSPF Version 2", RFC 3630, 816 DOI 10.17487/RFC3630, September 2003, 817 . 819 [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in 820 Support of Generalized Multi-Protocol Label Switching 821 (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005, 822 . 824 [RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed., 825 "Traffic Engineering Extensions to OSPF Version 3", 826 RFC 5329, DOI 10.17487/RFC5329, September 2008, 827 . 829 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 830 for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, 831 . 833 [RFC7308] Osborne, E., "Extended Administrative Groups in MPLS 834 Traffic Engineering (MPLS-TE)", RFC 7308, 835 DOI 10.17487/RFC7308, July 2014, 836 . 838 [RFC7471] Giacalone, S., Ward, D., Drake, J., Atlas, A., and S. 839 Previdi, "OSPF Traffic Engineering (TE) Metric 840 Extensions", RFC 7471, DOI 10.17487/RFC7471, March 2015, 841 . 843 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 844 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 845 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 846 2015, . 848 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 849 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 850 May 2017, . 852 [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and 853 F. Baker, "OSPFv3 Link State Advertisement (LSA) 854 Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 855 2018, . 857 17.2. Informative References 859 [I-D.ietf-spring-segment-routing-policy] 860 Filsfils, C., Sivabalan, S., Voyer, D., Bogdanov, A., and 861 P. Mattes, "Segment Routing Policy Architecture", draft- 862 ietf-spring-segment-routing-policy-07 (work in progress), 863 May 2020. 865 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 866 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 867 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 868 . 870 [RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality 871 for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006, 872 . 874 [RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for 875 IP Fast Reroute: Loop-Free Alternates", RFC 5286, 876 DOI 10.17487/RFC5286, September 2008, 877 . 879 [RFC5709] Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M., 880 Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic 881 Authentication", RFC 5709, DOI 10.17487/RFC5709, October 882 2009, . 884 [RFC5714] Shand, M. and S. Bryant, "IP Fast Reroute Framework", 885 RFC 5714, DOI 10.17487/RFC5714, January 2010, 886 . 888 [RFC7166] Bhatia, M., Manral, V., and A. Lindem, "Supporting 889 Authentication Trailer for OSPFv3", RFC 7166, 890 DOI 10.17487/RFC7166, March 2014, 891 . 893 [RFC7474] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed., 894 "Security Extension for OSPFv2 When Using Manual Key 895 Management", RFC 7474, DOI 10.17487/RFC7474, April 2015, 896 . 898 Authors' Addresses 899 Peter Psenak (editor) 900 Cisco Systems 901 Eurovea Centre, Central 3 902 Pribinova Street 10 903 Bratislava 81109 904 Slovakia 906 Email: ppsenak@cisco.com 908 Les Ginsberg 909 Cisco Systems 910 821 Alder Drive 911 MILPITAS, CA 95035 912 USA 914 Email: ginsberg@cisco.com 916 Wim Henderickx 917 Nokia 918 Copernicuslaan 50 919 Antwerp, 2018 94089 920 Belgium 922 Email: wim.henderickx@nokia.com 924 Jeff Tantsura 925 Apstra 926 US 928 Email: jefftant.ietf@gmail.com 930 John Drake 931 Juniper Networks 932 1194 N. Mathilda Ave 933 Sunnyvale, California 94089 934 USA 936 Email: jdrake@juniper.net