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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) ** Obsolete normative reference: RFC 4970 (Obsoleted by RFC 7770) -- Obsolete informational reference (is this intentional?): RFC 5226 (ref. 'IANA-GUIDE') (Obsoleted by RFC 8126) Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Lindem, Ed. 3 Internet-Draft N. Shen 4 Obsoletes: 4970 (if approved) J. Vasseur 5 Intended status: Standards Track Cisco Systems 6 Expires: March 26, 2016 R. Aggarwal 7 Arktan 8 S. Shaffer 9 Akamai 10 September 23, 2015 12 Extensions to OSPF for Advertising Optional Router Capabilities 13 draft-ietf-ospf-rfc4970bis-03.txt 15 Abstract 17 It is useful for routers in an OSPFv2 or OSPFv3 routing domain to 18 know the capabilities of their neighbors and other routers in the 19 routing domain. This document proposes extensions to OSPFv2 and 20 OSPFv3 for advertising optional router capabilities. The Router 21 Information (RI) Link State Advertisement (LSA) is defined for this 22 purpose. In OSPFv2, the RI LSA will be implemented with an opaque 23 LSA type ID. In OSPFv3, the RI LSA will be implemented with a unique 24 LSA type function code. In both protocols, the RI LSA can be 25 advertised at any of the defined flooding scopes (link, area, or 26 autonomous system (AS)). This document obsoletes RFC 4970 by 27 providing a revised specification including support for advertisement 28 of multiple instances of the RI LSA and a TLV for functional 29 capabilities. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at http://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on March 26, 2016. 48 Copyright Notice 50 Copyright (c) 2015 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents 55 (http://trustee.ietf.org/license-info) in effect on the date of 56 publication of this document. Please review these documents 57 carefully, as they describe your rights and restrictions with respect 58 to this document. Code Components extracted from this document must 59 include Simplified BSD License text as described in Section 4.e of 60 the Trust Legal Provisions and are provided without warranty as 61 described in the Simplified BSD License. 63 Table of Contents 65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 66 1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 3 67 1.2. Summary of Changes from RFC 4970 . . . . . . . . . . . . 3 68 2. OSPF Router Information (RI) LSA . . . . . . . . . . . . . . 3 69 2.1. OSPFv2 Router Information (RI) Opaque LSA . . . . . . . . 4 70 2.2. OSPFv3 Router Information (RI) Opaque LSA . . . . . . . . 6 71 2.3. OSPF Router Informational Capabilities TLV . . . . . . . 6 72 2.4. Assigned OSPF Router Informational Capability Bits . . . 7 73 2.5. OSPF Router Functional Capabilities TLV . . . . . . . . . 8 74 2.6. Flooding Scope of the Router Information LSA . . . . . . 9 75 3. Backward Compatibility . . . . . . . . . . . . . . . . . . . 10 76 4. Security Considerations . . . . . . . . . . . . . . . . . . . 10 77 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 78 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 79 6.1. Normative References . . . . . . . . . . . . . . . . . . 13 80 6.2. Informative References . . . . . . . . . . . . . . . . . 13 81 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 13 82 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 84 1. Introduction 86 It is useful for routers in an OSPFv2 [OSPF] or OSPFv3 [OSPFV3] 87 routing domain to know the capabilities of their neighbors and other 88 routers in the routing domain. This can be useful for both the 89 advertisement and discovery of OSPFv2 and OSPFv3 capabilities. 90 Throughout this document, OSPF will be used when the specification is 91 applicable to both OSPFv2 and OSPFv3. Similarly, OSPFv2 or OSPFv3 92 will be used when the text is protocol specific. 94 OSPF uses the options field in LSAs and hello packets to advertise 95 optional router capabilities. In the case of OSPFv2, all the bits in 96 this field have been allocated so additional optional capabilities 97 cannot be advertised. This document describes extensions to OSPF to 98 advertise these optional capabilities via opaque LSAs in OSPFv2 and 99 LSAs with a unique type in OSPFv3. For existing OSPF capabilities, 100 backward-compatibility issues dictate that this advertisement is used 101 primarily for informational purposes. For future OSPF extensions, 102 this advertisement MAY be used as the sole mechanism for 103 advertisement and discovery. 105 This document obsoletes RFC 4970 by providing a revised specification 106 including support for advertisement of multiple instances of the RI 107 LSA and a TLV for functional capabilities. 109 1.1. Requirements Notation 111 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 112 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 113 document are to be interpreted as described in [RFC-KEYWORDS]. 115 1.2. Summary of Changes from RFC 4970 117 This document includes the following changes from RFC 4970 [RFC4970]: 119 1. The main change is that an OSPF router will be able to advertise 120 multiple instances of the OSPF Router Information LSA. This 121 change permeates through much of the document 123 2. Additionally, Section 2.5 includes an additional TLV for 124 functional capabilities. This is in contrast to the existing TLV 125 which is used to advertise capabilities for informational 126 purposes only. 128 3. Finally, references have been updated for drafts that have become 129 RFCs and RFCs that have been obsoleted since the publication of 130 RFC 4970. 132 2. OSPF Router Information (RI) LSA 134 OSPFv2 routers will advertise a link scoped, area-scoped, or AS- 135 scoped Opaque-LSA [OPAQUE]. The OSPFv2 Router Information (RI) LSA 136 has an Opaque type of 4 and the Opaque ID is the RI LSA instance ID. 137 The first Opaque ID, i.e., 0, SHOULD always contain the Router 138 Informational Capabilities TLV and, if advertised, the Router 139 Functional Capabilities TLV. RI LSAs subsequence to the first can be 140 used for information that doesn't fit in the first instance. 142 2.1. OSPFv2 Router Information (RI) Opaque LSA 144 OSPFv2 routers will advertise a link scoped, area-scoped, or AS- 145 scoped Opaque-LSA [OPAQUE]. The OSPFv2 Router Information LSA has an 146 Opaque type of 4 and Opaque ID specifies the LSA instance ID with the 147 first instance always having an Instance ID of 0. 149 0 1 2 3 150 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 1 151 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 152 | LS age | Options | 9, 10, or 11 | 153 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 154 | 4 | Opaque ID (Instance ID) | 155 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 156 | Advertising Router | 157 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 158 | LS sequence number | 159 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 160 | LS checksum | length | 161 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 162 | | 163 +- TLVs -+ 164 | ... | 166 OSPFv2 Router Information Opaque LSA 168 The format of the TLVs within the body of an RI LSA is the same as 169 the format used by the Traffic Engineering Extensions to OSPF [TE]. 170 The LSA payload consists of one or more nested Type/Length/Value 171 (TLV) triplets. The format of each TLV is: 173 0 1 2 3 174 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 1 175 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 176 | Type | Length | 177 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 178 | Value... | 179 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 181 TLV Format 183 The Length field defines the length of the value portion in octets 184 (thus a TLV with no value portion would have a length of 0). The TLV 185 is padded to 4-octet alignment; padding is not included in the length 186 field (so a 3-octet value would have a length of 3, but the total 187 size of the TLV would be 8 octets). Nested TLVs are also 32-bit 188 aligned. For example, a 1-byte value would have the length field set 189 to 1, and 3 octets of padding would be added to the end of the value 190 portion of the TLV. The padding is composed of zeros. Unrecognized 191 types are ignored. 193 2.2. OSPFv3 Router Information (RI) Opaque LSA 195 The OSPFv3 Router Information LSA has a function code of 12 while the 196 S1/S2 bits are dependent on the desired flooding scope for the LSA. 197 The U bit will be set indicating that the OSPFv3 RI LSA should be 198 flooded even if it is not understood. The Link State ID (LSID) value 199 for this LSA is the instance ID. The first instance ID, i.e., 0, 200 SHOULD always contain the Router Informational Capabilities TLV and, 201 if advertised, the Router Functional Capabilities TLV. OSPFv3 Router 202 Information LSAs subsequence to the first can be used for information 203 that doesn't fit in the first instance. OSPFv3 routers MAY advertise 204 multiple RI LSAs per flooding scope. 206 0 1 2 3 207 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 1 208 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 209 | LS age |1|S12| 12 | 210 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 211 | Link State ID (Instance ID) | 212 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 213 | Advertising Router | 214 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 215 | LS sequence number | 216 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 217 | LS checksum | Length | 218 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 219 | | 220 +- TLVs -+ 221 | ... | 223 OSPFv3 Router Information LSA 225 The format of the TLVs within the body of an RI LSA is as defined in 226 Section 2.1 228 When a new Router Information LSA TLV is defined, the specification 229 MUST explicitly state whether the TLV is applicable to OSPFv2 only, 230 OSPFv3 only, or both OSPFv2 and OSPFv3. 232 2.3. OSPF Router Informational Capabilities TLV 234 An OSPF router advertising an OSPF RI LSA MAY include the Router 235 Informational Capabilities TLV. If included, it MUST be the first 236 TLV in the first instance, i.e., instance 0, of the OSPF RI LSA. 237 Additionally, the TLV MUST accurately reflect the OSPF router's 238 capabilities in the scope advertised. However, the informational 239 capabilities advertised have no impact on the OSPF's operation, they 240 are advertised purely for informational purposes. 242 The format of the Router Informational Capabilities TLV is as 243 follows: 245 0 1 2 3 246 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 1 247 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 248 | Type | Length | 249 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 250 | Informational Capabilities | 251 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 253 Type A 16-bit field set to 1. 255 Length A 16-bit field that indicates the length of the value 256 portion in octets and will be a multiple of 4 octets 257 dependent on the number of capabilities advertised. 258 Initially, the length will be 4, denoting 4 octets of 259 informational capability bits. 261 Value A variable length sequence of capability bits rounded 262 to a multiple of 4 octets padded with undefined bits. 263 Initially, there are 4 octets of capability bits. Bits 264 are numbered left-to-right starting with the most 265 significant bit being bit 0. 267 OSPF Router Informational Capabilities TLV 269 The Router Informational Capabilities TLV MAY be followed by optional 270 TLVs that further specify a capability. 272 2.4. Assigned OSPF Router Informational Capability Bits 274 The following informational capability bits are assigned: 276 Bit Capabilities 278 0 OSPF graceful restart capable [GRACE] 279 1 OSPF graceful restart helper [GRACE] 280 2 OSPF Stub Router support [STUB] 281 3 OSPF Traffic Engineering support [TE] 282 4 OSPF point-to-point over LAN [P2PLAN] 283 5 OSPF Experimental TE [EXP-TE] 284 6-31 Unassigned (IETF Review) 286 OSPF Router Informational Capabilities Bits 288 References for [GRACE], [STUB], [TE], [P2PLAN], and [EXP-TE] are 289 included herein. 291 2.5. OSPF Router Functional Capabilities TLV 293 This specification also defines the Router Functional Capabilities 294 TLV for advertisement within the OSPF Router Information LSA. An 295 OSPF router advertising an OSPF RI LSA MAY include the Router 296 Functional Capabilities TLV. If included, it MUST be the included in 297 the first instance of the LSA. Additionally, the TLV MUST be used to 298 reflect OSPF router functional capabilities. If the TLV is not 299 included or the length doesn't include the assigned OSPF functional 300 capability bit, the corresponding OSPF functional capability is 301 implicitly advertised as not being supported by the advertising OSPF 302 router. 304 The format of the Router Functional Capabilities TLV is as follows: 306 0 1 2 3 307 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 1 308 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 309 | Type | Length | 310 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 311 | Functional Capabilities | 312 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 314 Type A 16-bit field set to IANA TBD (Suggested value 2). 316 Length A 16-bit field that indicates the length of the value 317 portion in octets and will be a multiple of 4 octets 318 dependent on the number of capabilities advertised. 319 Initially, the length will be 4, denoting 4 octets of 320 informational capability bits. 322 Value A variable length sequence of capability bits rounded 323 to a multiple of 4 octets padded with undefined bits. 324 Initially, there are 4 octets of capability bits. Bits 325 are numbered left-to-right starting with the most 326 significant bit being bit 0. 328 OSPF Router Functional Capabilities TLV 330 The Router Functional Capabilities TLV MAY be followed by optional 331 TLVs that further specify a capability. In contrast to the Router 332 Informational Capabilities TLV, the OSPF extensions advertised in 333 this TLV MAY be used by other OSPF routers to dictate protocol 334 operation. The specifications for functional capabilities advertised 335 in this TLV MUST describe protocol behavior and address backward 336 compatibility. 338 2.6. Flooding Scope of the Router Information LSA 340 The flooding scope for a Router Information LSA is determined by the 341 LSA type. For OSPFv2, type 9 (link-scoped), type 10 (area-scoped), 342 or a type 11 (AS-scoped) opaque LSA may be flooded. For OSPFv3, the 343 S1 and S2 bits in the LSA type determine the flooding scope. If AS- 344 wide flooding scope is chosen, the originating router should also 345 advertise area-scoped LSA(s) into any attached Not-So-Stubby Area 346 (NSSA) area(s). An OSPF router MAY advertise different capabilities 347 when both NSSA area scoped LSA(s) and an AS-scoped LSA are 348 advertised. This allows functional capabilities to be limited in 349 scope. For example, a router may be an area border router but only 350 support traffic engineering (TE) in a subset of its attached areas. 352 The choice of flooding scope is made by the advertising router and is 353 a matter of local policy. The originating router MAY advertise 354 multiple RI LSAs with the same instance ID as long as the flooding 355 scopes differ. TLV flooding scope rules will be specified on a per- 356 TLV basis and MUST be specified in the accompanying specifications 357 for future Router Information LSA TLVs. 359 3. Backward Compatibility 361 For backward compatibility, previously advertised Router Information 362 TLVs SHOULD continue to be advertised in the first instance, i.e., 0, 363 of the Router Information LSA. If a Router Information TLV is 364 advertised in multiple Router Information LSA instances and the 365 multiple instance processing is not explicitly specified in the RFC 366 defining that Router Information TLV, the Router Instance TLV in the 367 Router Information LSA with the numerically smallest Instance ID will 368 be used and subsequent instances will be ignored. 370 4. Security Considerations 372 This document describes both a generic mechanism for advertising 373 router capabilities and a TLV for advertising informational and 374 functional capability bits. The capability TLVs are less critical 375 than the topology information currently advertised by the base OSPF 376 protocol. The security considerations for the generic mechanism are 377 dependent on the future application and, as such, should be described 378 as additional capabilities are proposed for advertisement. Security 379 considerations for the base OSPF protocol are covered in [OSPF] and 380 [OSPFV3]. 382 5. IANA Considerations 384 The following IANA assignment was made from an existing registry: 386 The OSPFv2 opaque LSA type 4 has been reserved for the OSPFv2 RI 387 opaque LSA. 389 The following registries have been defined for the following 390 purposes: 392 1. Registry for OSPFv3 LSA Function Codes - This top-level registry 393 will be comprised of the fields Value, LSA function code name, 394 and Document Reference. The OSPFv3 LSA function code is defined 395 in section A.4.2.1 of [OSPFV3]. The OSPFv3 LSA function code 12 396 has been reserved for the OSPFv3 Router Information (RI) LSA. 398 +-----------+-------------------------------------+ 399 | Range | Assignment Policy | 400 +-----------+-------------------------------------+ 401 | 0 | Reserved (not to be assigned) | 402 | | | 403 | 1-11 | Already assigned | 404 | | | 405 | 12 | OSPFv3 RI LSA (Assigned herein) | 406 | | | 407 | 13-15 | Already assigned | 408 | | | 409 | 16-255 | Unassigned (IETF Review) | 410 | | | 411 | 256-8175 | Reserved (No assignments) | 412 | | | 413 | 8176-8183 | Experimentation (No assignments) | 414 | | | 415 | 8184-8191 | Vendor Private Use (No assignments) | 416 +-----------+-------------------------------------+ 418 OSPFv3 LSA Function Codes 420 * OSPFv3 LSA function codes in the range 16-255 are not be 421 assigned subject to IETF Review. New values are assigned only 422 through RFCs that have been shepherded through the IESG as AD- 423 Sponsored or IETF WG Documents [IANA-GUIDE]. 425 * OSPFv3 LSA function codes in the range 8176-8181 are for 426 experimental use; these will not be registered with IANA and 427 MUST NOT be mentioned by RFCs. 429 * OSPFv3 LSAs with an LSA Function Code in the Vendor Private 430 Use range 8184-8191 MUST include the Vendor Enterprise Code as 431 the first 4 octets following the 20 octets of LSA header. 433 * If a new LSA Function Code is documented, the documentation 434 MUST include the valid combinations of the U, S2, and S1 bits 435 for the LSA. It SHOULD also describe how the Link State ID is 436 to be assigned. 438 2. Registry for OSPF RI TLVs - This top-level registry will be 439 comprised of the fields Value, TLV Name, and Document Reference. 440 The value of 1 for the informational capabilities TLV is defined 441 herein. The value IANA TBD (suggested value 2) for the Router 442 Functional Capabilities TLV is also defined herein. 444 +-------------+-----------------------------------+ 445 | Range | Assignment Policy | 446 +-------------+-----------------------------------+ 447 | 0 | Reserved (not to be assigned) | 448 | | | 449 | 1 | Informational Capabilities | 450 | | | 451 | 2 | Unassigned (IETF Review) | 452 | | | 453 | TBD | Functional Capabilities | 454 | | | 455 | 3-9 | Already Assigned | 456 | | | 457 | 10-32767 | Unassigned (IETF Review) | 458 | | | 459 | 32768-32777 | Experimentation (No assignments) | 460 | | | 461 | 32778-65535 | Reserved (Not to be assigned) | 462 +-----------+-------------------------------------+ 464 OSPF RI TLVs 466 * Types in the range 2, 10-32767 are to be assigned subject to 467 IETF Review. New values are assigned only through RFCs that 468 have been shepherded through the IESG as AD-Sponsored or IETF 469 WG Documents [IANA-GUIDE]. 471 * Types in the range 32778-65535 are reserved and are not to be 472 assigned at this time. Before any assignments can be made in 473 this range, there MUST be a Standards Track RFC that specifies 474 IANA Considerations that covers the range being assigned. 476 3. Registry for OSPF Router Informational Capability Bits - This 477 sub-registry of the OSPF RI TLV registry will be comprised of the 478 fields Bit Number, Capability Name, and Document Reference. The 479 values are defined in Section 2.4. All Router Informational 480 Capability TLV additions are to be assigned through IETF Review. 482 4. Registry for OSPF Router Functional Capability Bits - This sub- 483 registry of the OSPF RI TLV registry will be comprised of the 484 fields Bit Number, Capability Name, and Document Reference. 485 Initially, the sub-registry will be empty but will be available 486 for future capabilities. All Router Functional Capability TLV 487 additions are to be assigned through IETF Review. 489 6. References 491 6.1. Normative References 493 [OPAQUE] Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The 494 OSPF Opaque LSA Option", RFC 5250, July 2008. 496 [OSPF] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. 498 [OSPFV3] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 499 for IPv6", RFC 5340, July 2008. 501 [RFC-KEYWORDS] 502 Bradner, S., "Key words for use in RFC's to Indicate 503 Requirement Levels", BCP 14, RFC 2119, March 1997. 505 [RFC4970] Lindem, A., Shen, N., Vasseur, J., Aggarwal, R., and S. 506 Shaffer, "Extensions to OSPF for Advertising Optional 507 Router Capabilities", RFC 4970, July 2007. 509 [TE] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 510 Extensions to OSPF", RFC 3630, September 2003. 512 6.2. Informative References 514 [EXP-TE] Srisuresh, P. and P. Joseph, "OSPF-xTE: Experimental 515 Extension to OSPF for Traffic Engineering", RFC 4973, July 516 2007. 518 [GRACE] Moy, J., Pillay-Esnault, P., and A. Lindem, "Graceful OSPF 519 Restart", RFC 3623, November 2003. 521 [IANA-GUIDE] 522 Narten, T. and H. Alvestrand, "Guidelines for Writing an 523 IANA Considerations Section in RFCs", RFC 5226, May 2008. 525 [P2PLAN] Shen, N. and A. Zinin, "Point-to-point operation over LAN 526 in link-state routing protocols", RFC 5309, October 2008. 528 [STUB] Retana, A., Nguyen, L., White, R., Zinin, A., and D. 529 McPherson, "OSPF Stub Router Advertisement", RFC 6987, 530 September 2013. 532 Appendix A. Acknowledgments 534 The idea for this work grew out of a conversation with Andrew Partan 535 and we would like to thank him for his contribution. The authors 536 would like to thanks Peter Psenak for his review and helpful comments 537 on early versions of the document. 539 Comments from Abhay Roy, Vishwas Manral, Vivek Dubey, and Adrian 540 Farrel have been incorporated into later versions. 542 Thanks to Chris Bowers, Shraddha Hegde, and Alia Atlas for review of 543 the BIS version of this document. 545 The RFC text was produced using Marshall Rose's xml2rfc tool. 547 Authors' Addresses 549 Acee Lindem (editor) 550 Cisco Systems 551 301 Midenhall Way 552 Cary, NC 27513 553 USA 555 Email: acee@cisco.com 557 Naiming Shen 558 Cisco Systems 559 225 West Tasman Drive 560 San Jose, CA 95134 561 USA 563 Email: naiming@cisco.com 565 Jean-Philippe Vasseur 566 Cisco Systems 567 1414 Massachusetts Avenue 568 Boxborough, MA 01719 569 USA 571 Email: jpv@cisco.com 573 Rahul Aggarwal 574 Arktan 576 Email: raggarwa_1@yahoo.com 577 Scott Shaffer 578 Akamai 579 8 Cambridge Center 580 Cambridge, MA 02142 581 USA 583 Email: sshaffer@akamai.com