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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-19) exists of draft-ietf-isis-te-app-14 == Outdated reference: A later version (-22) exists of draft-ietf-spring-segment-routing-policy-07 -- Obsolete informational reference (is this intentional?): RFC 5226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 9, 2020 W. Henderickx 6 Nokia 7 J. Tantsura 8 Apstra 9 J. Drake 10 Juniper Networks 11 June 7, 2020 13 OSPF Link Traffic Engineering Attribute Reuse 14 draft-ietf-ospf-te-link-attr-reuse-14.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 December 9, 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 . . . . . . . . . . . . . . . . . . . . . . . . 14 85 12.3.1. Multiple Applications: Common Attributes with RSVP- 86 TE . . . . . . . . . . . . . . . . . . . . . . . . . 14 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 . . . . . . . . . . . . . . . . . . . . . 16 94 14.1. OSPFv2 . . . . . . . . . . . . . . . . . . . . . . . . . 16 95 14.2. OSPFv3 . . . . . . . . . . . . . . . . . . . . . . . . . 17 96 15. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 18 97 16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18 98 17. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 99 17.1. Normative References . . . . . . . . . . . . . . . . . . 18 100 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 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 example where this ambiguity causes a problem is a network in 130 which RSVP-TE is enabled only on a subset of its links. A link 131 attribute is advertised for the purpose of another application (e.g. 132 SRTE) for a link that is not enabled for RSV-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 which address these issues. Also, 146 as evolution of use cases for link attributes can be expected to 147 continue in the years to come, this document defines a solution which 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 then RSVP-TE or GMPLS. 169 These LSAs were defined as a generic containers for distribution of 170 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, that 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 application that is not defined as standardized one. We call such 233 application a user defined application. What such application might 234 be is not subject to the standardization and is outside of the scope 235 of this specification. 237 The ASLA sub-TLV is an optional sub-TLV and can appear multiple times 238 in the OSPFv2 Extended Link TLV and OSPFv3 Router-Link TLV. The ASLA 239 sub-TLV MUST be used for advertisement of the link attributes listed 240 at the end on this section if these are advertised inside OSPFv2 241 Extended Link TLV and OSPFv3 Router-Link TLV. It has the following 242 format: 244 0 1 2 3 245 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 1 246 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 247 | Type | Length | 248 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 249 | SABM Length | UDABM Length | Reserved | 250 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 251 | Standard Application Identifier Bit Mask | 252 +- -+ 253 | ... | 254 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 255 | User Defined Application Identifier Bit Mask | 256 +- -+ 257 | ... | 258 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 259 | Link Attribute sub-sub-TLVs | 260 +- -+ 261 | ... | 263 where: 265 Type: 10 (OSPFv2), 11 (OSPFv3) 267 Length: variable 269 SABM Length: Standard Application Identifier Bit Mask Length in 270 octets. The value MUST be 0, 4 or 8. If the Standard Application 271 Bit Mask is not present, the Standard Application Bit Mask Length 272 MUST be set to 0. 274 UDABM Length: User Defined Application Identifier Bit Mask Length 275 in octets. The value MUST be 0, 4 or 8. If the User Defined 276 Application Bit Mask is not present, the User Defined Application 277 Bit Mask Length MUST be set to 0. 279 Standard Application Identifier Bit Mask: Optional set of bits, 280 where each bit represents a single standard application. Bits are 281 defined in the Link Attribute Application Identifier Registry, 282 which has been defined in [I-D.ietf-isis-te-app]. Current 283 assignments are repeated here for informational purpose: 285 Bit-0 (R-bit): RSVP-TE 287 Bit-1 (S-bit): Segment Routing TE 289 Bit-2 (F-bit): Loop Free Alternate (LFA). Includes all LFA 290 types 292 User Defined Application Identifier Bit Mask: Optional set of 293 bits, where each bit represents a single user defined application. 295 If the SABM or UDABM length is other than 0, 4, or 8, the ASLA sub- 296 TLV MUST be ignored by the receiver. 298 Standard Application Identifier Bits are defined/sent starting with 299 Bit 0. Undefined bits which are transmitted MUST be transmitted as 0 300 and MUST be ignored on receipt. Bits that are not transmitted MUST 301 be treated as if they are set to 0 on receipt. Bits that are not 302 supported by an implementation MUST be ignored on receipt. 304 User Defined Application Identifier Bits have no relationship to 305 Standard Application Identifier Bits and are not managed by IANA or 306 any other standards body. It is recommended that bits are used 307 starting with Bit 0 so as to minimize the number of octets required 308 to advertise all UDAs. 310 If the link attribute advertisement is intended to be only used by a 311 specific set of applications, corresponding Bit Masks MUST be present 312 and application specific bit(s) MUST be set for all applications that 313 use the link attributes advertised in the ASLA sub-TLV. 315 Application Bit Masks apply to all link attributes that support 316 application specific values and are advertised in the ASLA sub-TLV. 318 The advantage of not making the Application Bit Masks part of the 319 attribute advertisement itself is that the format of any previously 320 defined link attributes can be kept and reused when advertising them 321 in the ASLA sub-TLV. 323 If the same attribute is advertised in more than single ASLA sub-TLVs 324 with the application listed in the Application Bit Masks, the 325 application SHOULD use the first instance of advertisement and ignore 326 any subsequent advertisements of that attribute. 328 This document defines the initial set of link attributes that MUST 329 use the ASLA sub-TLV if advertised in the OSPFv2 Extended Link TLV or 330 in the OSPFv3 Router-Link TLV. Documents which define new link 331 attributes MUST state whether the new attributes support application 332 specific values and as such MUST be advertised in an ASLA sub-TLV. 333 The link attributes that MUST be advertised in ASLA sub-TLVs are: 335 - Shared Risk Link Group [RFC4203] 337 - Unidirectional Link Delay [RFC7471] 339 - Min/Max Unidirectional Link Delay [RFC7471] 341 - Unidirectional Delay Variation [RFC7471] 343 - Unidirectional Link Loss [RFC7471] 345 - Unidirectional Residual Bandwidth [RFC7471] 347 - Unidirectional Available Bandwidth [RFC7471] 349 - Unidirectional Utilized Bandwidth [RFC7471] 351 - Administrative Group [RFC3630] 353 - Extended Administrative Group [RFC7308] 355 - TE Metric [RFC3630] 357 6. Reused TE link attributes 359 This section defines the use case and indicates the code points 360 (Section 14) from the OSPFv2 Extended Link TLV Sub-TLV Registry and 361 OSPFv3 Extended-LSA Sub-TLV Registry for some of the link attributes 362 that have been originally defined for RSVP-TE or GMPLS. 364 6.1. Shared Risk Link Group (SRLG) 366 The SRLG of a link can be used in OSPF calculated IPFRR [RFC5714] to 367 compute a backup path that does not share any SRLG group with the 368 protected link. 370 To advertise the SRLG of the link in the OSPFv2 Extended Link TLV, 371 the same format for the sub-TLV defined in section 1.3 of [RFC4203] 372 is used and TLV type 11 is used. Similarly, for OSPFv3 to advertise 373 the SRLG in the OSPFv3 Router-Link TLV, TLV type 12 is used. 375 6.2. Extended Metrics 377 [RFC3630] defines several link bandwidth types. [RFC7471] defines 378 extended link metrics that are based on link bandwidth, delay and 379 loss characteristics. All these can be used to compute primary and 380 backup paths within an OSPF area to satisfy requirements for 381 bandwidth, delay (nominal or worst case) or loss. 383 To advertise extended link metrics in the OSPFv2 Extended Link TLV, 384 the same format for the sub-TLVs defined in [RFC7471] is used with 385 the following TLV types: 387 12 - Unidirectional Link Delay 389 13 - Min/Max Unidirectional Link Delay 391 14 - Unidirectional Delay Variation 393 15 - Unidirectional Link Loss 395 16 - Unidirectional Residual Bandwidth 397 17 - Unidirectional Available Bandwidth 399 18 - Unidirectional Utilized Bandwidth 401 To advertise extended link metrics in the OSPFv3 Extended-LSA Router- 402 Link TLV, the same format for the sub-TLVs defined in [RFC7471] is 403 used with the following TLV types: 405 13 - Unidirectional Link Delay 407 14 - Min/Max Unidirectional Link Delay 409 15 - Unidirectional Delay Variation 411 16 - Unidirectional Link Loss 413 17 - Unidirectional Residual Bandwidth 415 18 - Unidirectional Available Bandwidth 417 19 - Unidirectional Utilized Bandwidth 419 6.3. Administrative Group 421 [RFC3630] and [RFC7308] define the Administrative Group and Extended 422 Administrative Group sub-TLVs respectively. 424 To advertise the Administrative Group and Extended Administrative 425 Group in the OSPFv2 Extended Link TLV, the same format for the sub- 426 TLVs defined in [RFC3630] and [RFC7308] is used with the following 427 TLV types: 429 19 - Administrative Group 431 20 - Extended Administrative Group 433 To advertise Administrative Group and Extended Administrative Group 434 in the OSPFv3 Router-Link TLV, the same format for the sub-TLVs 435 defined in [RFC3630] and [RFC7308] is used with the following TLV 436 types: 438 20 - Administrative Group 440 21 - Extended Administrative Group 442 6.4. Traffic Engineering Metric 444 [RFC3630] defines Traffic Engineering Metric. 446 To advertise the Traffic Engineering Metric in the OSPFv2 Extended 447 Link TLV, the same format for the sub-TLV defined in section 2.5.5 of 448 [RFC3630] is used and TLV type 22 is used. Similarly, for OSPFv3 to 449 advertise the Traffic Engineering Metric in the OSPFv3 Router-Link 450 TLV, TLV type 22 is used. 452 7. Maximum Link Bandwidth 454 Maximum link bandwidth is an application independent attribute of the 455 link that is defined in [RFC3630]. Because it is an application 456 independent attribute, it MUST NOT be advertised in ASLA sub-TLV. 457 Instead, it MAY be advertised as a sub-TLV of the Extended Link 458 Opaque LSA Extended Link TLV in OSPFv2 [RFC7684] or sub-TLV of OSPFv3 459 E-Router-LSA Router-Link TLV in OSPFv3 [RFC8362]. 461 To advertise the Maximum link bandwidth in the OSPFv2 Extended Link 462 TLV, the same format for sub-TLV defined in [RFC3630] is used with 463 TLV type 23. 465 To advertise the Maximum link bandwidth in the OSPFv3 Router-Link 466 TLV, the same format for sub-TLV defined in [RFC3630] is used with 467 TLV type 23. 469 8. Considerations for Extended TE Metrics 471 [RFC7471] defines a number of dynamic performance metrics associated 472 with a link. It is conceivable that such metrics could be measured 473 specific to traffic associated with a specific application. 474 Therefore this document includes support for advertising these link 475 attributes specific to a given application. However, in practice it 476 may well be more practical to have these metrics reflect the 477 performance of all traffic on the link regardless of application. In 478 such cases, advertisements for these attributes can be associated 479 with all of the applications utilizing that link. This can be done 480 either by explicitly specifying the applications in the Application 481 Identifier Bit Mask or by using a zero length Application Identifier 482 Bit Mask. 484 9. Local Interface IPv6 Address Sub-TLV 486 The Local Interface IPv6 Address Sub-TLV is an application 487 independent attribute of the link that is defined in [RFC5329]. 488 Because it is an application independent attribute, it MUST NOT be 489 advertised in the ASLA sub-TLV. Instead, it MAY be advertised as a 490 sub-TLV of the OSPFv3 E-Router-LSA Router-Link TLV [RFC8362]. 492 To advertise the Local Interface IPv6 Address Sub-TLV in the OSPFv3 493 Router-Link TLV, the same format for sub-TLV defined in [RFC5329] is 494 used with TLV type 24. 496 10. Remote Interface IPv6 Address Sub-TLV 498 The Remote Interface IPv6 Address Sub-TLV is an application 499 independent attribute of the link that is defined in [RFC5329]. 500 Because it is an application independent attribute, it MUST NOT be 501 advertised in the ASLA sub-TLV. Instead, it MAY be advertised as a 502 sub-TLV of the OSPFv3 E-Router-LSA Router-Link TLV [RFC8362]. 504 To advertise the Remote Interface IPv6 Address Sub-TLV in the OSPFv3 505 Router-Link TLV, the same format for sub-TLV defined in [RFC5329] is 506 used with TLV type 25. 508 11. Attribute Advertisements and Enablement 510 This document defines extensions to support the advertisement of 511 application specific link attributes. 513 There are applications where the application enablement on the link 514 is relevant - e.g. RSVP-TE - one need to make sure that RSVP is 515 enabled on the link before sending a RSVP-TE signaling message over 516 it. 518 There are applications, where the enablement of the application on 519 the link is irrelevant and has nothing to do with the fact that some 520 link attributes are advertised for the purpose of such application - 521 e.g. LFA. 523 Whether the presence of link attribute advertisements for a given 524 application indicates that the application is enabled on that link 525 depends upon the application. Similarly, whether the absence of link 526 attribute advertisements indicates that the application is not 527 enabled depends upon the application. 529 In the case of RSVP-TE, the advertisement of application specific 530 link attributes has no implication of RSVP-TE being enabled on that 531 link. The RSVP-TE enablement is solely derived from the information 532 carried in the OSPFv2 TE Opaque LSA [RFC3630] and OSPFv3 Intra-Area- 533 TE-LSA [RFC5329]. 535 In the case of SRTE, advertisement of application specific link 536 attributes does not indicate enablement of SRTE. The advertisements 537 are only used to support constraints which may be applied when 538 specifying an explicit path. SRTE is implicitly enabled on all links 539 which are part of the Segment Routing enabled topology independent of 540 the existence of link attribute advertisements 542 In the case of LFA, advertisement of application specific link 543 attributes does not indicate enablement of LFA on that link. 544 Enablement is controlled by local configuration. 546 If, in the future, additional standard applications are defined to 547 use this mechanism, the specification defining this use MUST define 548 the relationship between application specific link attribute 549 advertisements and enablement for that application. 551 This document allows the advertisement of application specific link 552 attributes with no application identifiers i.e., both the Standard 553 Application Identifier Bit Mask and the User Defined Application 554 Identifier Bit Mask are not present (See Section 5). This supports 555 the use of the link attribute by any application. In the presence of 556 an application where the advertisement of link attribute 557 advertisements is used to infer the enablement of an application on 558 that link (e.g., RSVP-TE), the absence of the application identifier 559 leaves ambiguous whether that application is enabled on such a link. 560 This needs to be considered when making use of the "any application" 561 encoding. 563 12. Deployment Considerations 565 12.1. Use of Legacy RSVP-TE LSA Advertisements 567 Bit Identifiers for Standard Applications are defined in Section 5. 568 All of the identifiers defined in this document are associated with 569 applications which were already deployed in some networks prior to 570 the writing of this document. Therefore, such applications have been 571 deployed using the RSVP-TE LSA advertisements. The Standard 572 Applications defined in this document may continue to use RSVP-TE LSA 573 advertisements for a given link so long as at least one of the 574 following conditions is true: 576 The application is RSVP-TE 578 The application is SRTE or LFA and RSVP-TE is not deployed 579 anywhere in the network 581 The application is SRTE or LFA, RSVP-TE is deployed in the 582 network, and both the set of links on which SRTE and/or LFA 583 advertisements are required and the attribute values used by SRTE 584 and/or LFA on all such links is fully congruent with the links and 585 attribute values used by RSVP-TE 587 Under the conditions defined above, implementations which support the 588 extensions defined in this document have the choice of using RSVP-TE 589 LSA advertisements or application specific advertisements in support 590 of SRTE and/or LFA. This will require implementations to provide 591 controls specifying which type of advertisements are to be sent/ 592 processed on receive for these applications. Further discussion of 593 the associated issues can be found in Section 12.3. 595 New applications which future documents define to make use of the 596 advertisements defined in this document MUST NOT make use of RSVP-TE 597 LSA advertisements. This simplifies deployment of new applications 598 by eliminating the need to support multiple ways to advertise 599 attributes for the new applications. 601 12.2. Use of Zero Length Application Identifier Bit Masks 603 If link attributes are advertised associated with zero length 604 Application Identifier Bit Masks for both standard applications and 605 user defined applications, then any Standard Application and/or any 606 User Defined Application is permitted to use that set of link 607 attributes so long as there is not another set of attributes 608 advertised on that same link which is associated with a non-zero 609 length Application Identifier Bit Mask with a matching Application 610 Identifier Bit set. If support for a new application is introduced 611 on any node in a network in the presence of such advertisements, 612 these advertisements are permitted to be used by the new application. 613 If this is not what is intended, then existing advertisements MUST be 614 readvertised with an explicit set of applications specified before a 615 new application is introduced. 617 12.3. Interoperability, Backwards Compatibility and Migration Concerns 619 Existing deployments of RSVP-TE, SRTE, and/or LFA utilize the legacy 620 advertisements listed in Section 3. Routers which do not support the 621 extensions defined in this document will only process legacy 622 advertisements and are likely to infer that RSVP-TE is enabled on the 623 links for which legacy advertisements exist. It is expected that 624 deployments using the legacy advertisements will persist for a 625 significant period of time. Therefore deployments using the 626 extensions defined in this document in the presence of routers which 627 do not support these extensions need to be able to interoperate with 628 the use of legacy advertisements by the legacy routers. The 629 following sub-sections discuss interoperability and backwards 630 compatibility concerns for a number of deployment scenarios. 632 12.3.1. Multiple Applications: Common Attributes with RSVP-TE 634 In cases where multiple applications are utilizing a given link, one 635 of the applications is RSVP-TE, and all link attributes for a given 636 link are common to the set of applications utilizing that link, 637 interoperability is achieved by using legacy advertisements for RSVP- 638 TE. Attributes for applications other than RSVP-TE MUST be 639 advertised using application specific advertisements. This results 640 in duplicate advertisements for those attributes. 642 12.3.2. Multiple Applications: Some Attributes Not Shared with RSVP-TE 644 In cases where one or more applications other than RSVP-TE are 645 utilizing a given link and one or more link attribute values are not 646 shared with RSVP-TE, interoperability is achieved by using legacy 647 advertisements for RSVP-TE. Attributes for applications other than 648 RSVP-TE MUST be advertised using application specific advertisements. 649 In cases where some link attributes are shared with RSVP-TE, this 650 requires duplicate advertisements for those attributes 652 12.3.3. Interoperability with Legacy Routers 654 For the applications defined in this document, routers which do not 655 support the extensions defined in this document will send and receive 656 only legacy link attribute advertisements. So long as there is any 657 legacy router in the network which has any of the applications 658 enabled, all routers MUST continue to advertise link attributes using 659 legacy advertisements. In addition, the link attribute values 660 associated with the set of applications supported by legacy routers 661 (RSVP-TE, SRTE, and/or LFA) are always shared since legacy routers 662 have no way of advertising or processing application specific values. 663 Once all legacy routers have been upgraded, migration from legacy 664 advertisements to application specific advertisements can be achieved 665 via the following steps: 667 1)Send new application specific advertisements while continuing to 668 advertise using the legacy advertisement (all advertisements are then 669 duplicated). Receiving routers continue to use legacy 670 advertisements. 672 2)Enable the use of the application specific advertisements on all 673 routers 675 3)Keep legacy advertisements if needed for RSVP-TE purposes. 677 When the migration is complete, it then becomes possible to advertise 678 incongruent values per application on a given link. 680 Documents defining new applications which make use of the application 681 specific advertisements defined in this document MUST discuss 682 interoperability and backwards compatibility issues that could occur 683 in the presence of routers which do not support the new application. 685 12.3.4. Use of Application Specific Advertisements for RSVP-TE 687 The extensions defined in this document support RSVP-TE as one of the 688 supported applications. It is however RECOMMENDED to advertise all 689 link-attributes for RSVP-TE in the existing OSPFv2 TE Opaque LSA 690 [RFC3630] and OSPFv3 Intra-Area-TE-LSA [RFC5329] to maintain backward 691 compatibility. RSVP-TE can eventually utilize the application 692 specific advertisements for newly defined link attributes, which are 693 defined as application specific. 695 Link attributes that are NOT allowed to be advertised in the ASLA 696 Sub-TLV, such as Maximum Reservable Link Bandwidth and Unreserved 697 Bandwidth MUST use the OSPFv2 TE Opaque LSA [RFC3630] and OSPFv3 698 Intra-Area-TE-LSA [RFC5329] and MUST NOT be advertised in ASLA Sub- 699 TLV. 701 13. Security Considerations 703 Existing security extensions as described in [RFC2328], [RFC5340] and 704 [RFC8362] apply to extensions defined in this document. While OSPF 705 is under a single administrative domain, there can be deployments 706 where potential attackers have access to one or more networks in the 707 OSPF routing domain. In these deployments, stronger authentication 708 mechanisms such as those specified in [RFC5709], [RFC7474], [RFC4552] 709 or [RFC7166] SHOULD be used. 711 Implementations must assure that malformed TLV and Sub-TLV defined in 712 this document are detected and do not provide a vulnerability for 713 attackers to crash the OSPF router or routing process. Reception of 714 a malformed TLV or Sub-TLV SHOULD be counted and/or logged for 715 further analysis. Logging of malformed TLVs and Sub-TLVs SHOULD be 716 rate-limited to prevent a Denial of Service (DoS) attack (distributed 717 or otherwise) from overloading the OSPF control plane. 719 This document defines a new way to advertise link attributes. 720 Tampering with the information defined in this document may have an 721 effect on applications using it, including impacting Traffic 722 Engineering. This is similar in nature to the impacts associated 723 with (for example) [RFC3630]. As the advertisements defined in this 724 document limit the scope to specific applications, the impact of 725 tampering is similarly limited in scope. 727 14. IANA Considerations 729 This specifications updates two existing registries: 731 - OSPFv2 Extended Link TLV Sub-TLVs Registry 733 - OSPFv3 Extended-LSA Sub-TLV Registry 735 New values are allocated using the IETF Review procedure as described 736 in [RFC5226]. 738 14.1. OSPFv2 740 The OSPFv2 Extended Link TLV Sub-TLVs Registry [RFC7684] defines sub- 741 TLVs at any level of nesting for OSPFv2 Extended Link TLVs. IANA has 742 assigned the following Sub-TLV types from the OSPFv2 Extended Link 743 TLV Sub-TLVs Registry: 745 10 - Application Specific Link Attributes 747 11 - Shared Risk Link Group 749 12 - Unidirectional Link Delay 751 13 - Min/Max Unidirectional Link Delay 753 14 - Unidirectional Delay Variation 755 15 - Unidirectional Link Loss 757 16 - Unidirectional Residual Bandwidth 758 17 - Unidirectional Available Bandwidth 760 18 - Unidirectional Utilized Bandwidth 762 19 - Administrative Group 764 20 - Extended Administrative Group 766 22 - TE Metric 768 23 - Maximum Link Bandwidth 770 14.2. OSPFv3 772 The OSPFv3 Extended-LSA Sub-TLV Registry [RFC8362] defines sub-TLVs 773 at any level of nesting for OSPFv3 Extended LSAs. IANA has assigned 774 the following Sub-TLV types from the OSPFv3 Extended-LSA Sub-TLV 775 Registry: 777 11 - Application Specific Link Attributes 779 12 - Shared Risk Link Group 781 13 - Unidirectional Link Delay 783 14 - Min/Max Unidirectional Link Delay 785 15 - Unidirectional Delay Variation 787 16 - Unidirectional Link Loss 789 17 - Unidirectional Residual Bandwidth 791 18 - Unidirectional Available Bandwidth 793 19 - Unidirectional Utilized Bandwidth 795 20 - Administrative Group 797 21 - Extended Administrative Group 799 22 - TE Metric 801 23 - Maximum Link Bandwidth 803 24 - Local Interface IPv6 Address Sub-TLV 805 25 - Remote Interface IPv6 Address Sub-TLV 807 15. Contributors 809 The following people contributed to the content of this document and 810 should be considered as co-authors: 812 Acee Lindem 813 Cisco Systems 814 301 Midenhall Way 815 Cary, NC 27513 816 USA 818 Email: acee@cisco.com 820 Ketan Talaulikar 821 Cisco Systems, Inc. 822 India 824 Email: ketant@cisco.com 826 Hannes Gredler 827 RtBrick Inc. 828 Austria 830 Email: hannes@rtbrick.com 832 16. Acknowledgments 834 Thanks to Chris Bowers for his review and comments. 836 Thanks to Alvaro Retana for his detailed review and comments. 838 17. References 840 17.1. Normative References 842 [I-D.ietf-isis-te-app] 843 Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and 844 J. Drake, "IS-IS TE Attributes per application", draft- 845 ietf-isis-te-app-14 (work in progress), June 2020. 847 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 848 Requirement Levels", BCP 14, RFC 2119, 849 DOI 10.17487/RFC2119, March 1997, 850 . 852 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 853 DOI 10.17487/RFC2328, April 1998, 854 . 856 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 857 (TE) Extensions to OSPF Version 2", RFC 3630, 858 DOI 10.17487/RFC3630, September 2003, 859 . 861 [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in 862 Support of Generalized Multi-Protocol Label Switching 863 (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005, 864 . 866 [RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed., 867 "Traffic Engineering Extensions to OSPF Version 3", 868 RFC 5329, DOI 10.17487/RFC5329, September 2008, 869 . 871 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 872 for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, 873 . 875 [RFC7308] Osborne, E., "Extended Administrative Groups in MPLS 876 Traffic Engineering (MPLS-TE)", RFC 7308, 877 DOI 10.17487/RFC7308, July 2014, 878 . 880 [RFC7471] Giacalone, S., Ward, D., Drake, J., Atlas, A., and S. 881 Previdi, "OSPF Traffic Engineering (TE) Metric 882 Extensions", RFC 7471, DOI 10.17487/RFC7471, March 2015, 883 . 885 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 886 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 887 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 888 2015, . 890 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 891 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 892 May 2017, . 894 [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and 895 F. Baker, "OSPFv3 Link State Advertisement (LSA) 896 Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 897 2018, . 899 17.2. Informative References 901 [I-D.ietf-spring-segment-routing-policy] 902 Filsfils, C., Sivabalan, S., Voyer, D., Bogdanov, A., and 903 P. Mattes, "Segment Routing Policy Architecture", draft- 904 ietf-spring-segment-routing-policy-07 (work in progress), 905 May 2020. 907 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 908 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 909 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 910 . 912 [RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality 913 for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006, 914 . 916 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 917 IANA Considerations Section in RFCs", RFC 5226, 918 DOI 10.17487/RFC5226, May 2008, 919 . 921 [RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for 922 IP Fast Reroute: Loop-Free Alternates", RFC 5286, 923 DOI 10.17487/RFC5286, September 2008, 924 . 926 [RFC5709] Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M., 927 Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic 928 Authentication", RFC 5709, DOI 10.17487/RFC5709, October 929 2009, . 931 [RFC5714] Shand, M. and S. Bryant, "IP Fast Reroute Framework", 932 RFC 5714, DOI 10.17487/RFC5714, January 2010, 933 . 935 [RFC7166] Bhatia, M., Manral, V., and A. Lindem, "Supporting 936 Authentication Trailer for OSPFv3", RFC 7166, 937 DOI 10.17487/RFC7166, March 2014, 938 . 940 [RFC7474] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed., 941 "Security Extension for OSPFv2 When Using Manual Key 942 Management", RFC 7474, DOI 10.17487/RFC7474, April 2015, 943 . 945 Authors' Addresses 947 Peter Psenak (editor) 948 Cisco Systems 949 Eurovea Centre, Central 3 950 Pribinova Street 10 951 Bratislava 81109 952 Slovakia 954 Email: ppsenak@cisco.com 956 Les Ginsberg 957 Cisco Systems 958 821 Alder Drive 959 MILPITAS, CA 95035 960 USA 962 Email: ginsberg@cisco.com 964 Wim Henderickx 965 Nokia 966 Copernicuslaan 50 967 Antwerp, 2018 94089 968 Belgium 970 Email: wim.henderickx@nokia.com 972 Jeff Tantsura 973 Apstra 974 US 976 Email: jefftant.ietf@gmail.com 978 John Drake 979 Juniper Networks 980 1194 N. Mathilda Ave 981 Sunnyvale, California 94089 982 USA 984 Email: jdrake@juniper.net