idnits 2.17.1 draft-ietf-ospf-link-overload-08.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (July 17, 2017) is 2475 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 7752 (Obsoleted by RFC 9552) Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Open Shortest Path First IGP S. Hegde 3 Internet-Draft Juniper Networks, Inc. 4 Intended status: Standards Track P. Sarkar 5 Expires: January 18, 2018 H. Gredler 6 Individual 7 M. Nanduri 8 ebay Corporation 9 L. Jalil 10 Verizon 11 July 17, 2017 13 OSPF Link Overload 14 draft-ietf-ospf-link-overload-08 16 Abstract 18 When a link is being prepared to be taken out of service, the traffic 19 needs to be diverted from both ends of the link. Increasing the 20 metric to the highest metric on one side of the link is not 21 sufficient to divert the traffic flowing in the other direction. 23 It is useful for routers in an OSPFv2 or OSPFv3 routing domain to be 24 able to advertise a link being in an overload state to indicate 25 impending maintenance activity on the link. This information can be 26 used by the network devices to re-route the traffic effectively. 28 This document describes the protocol extensions to disseminate link- 29 overload information in OSPFv2 and OSPFv3. 31 Requirements Language 33 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 34 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 35 document are to be interpreted as described in RFC 2119 [RFC2119]. 37 Status of This Memo 39 This Internet-Draft is submitted in full conformance with the 40 provisions of BCP 78 and BCP 79. 42 Internet-Drafts are working documents of the Internet Engineering 43 Task Force (IETF). Note that other groups may also distribute 44 working documents as Internet-Drafts. The list of current Internet- 45 Drafts is at http://datatracker.ietf.org/drafts/current/. 47 Internet-Drafts are draft documents valid for a maximum of six months 48 and may be updated, replaced, or obsoleted by other documents at any 49 time. It is inappropriate to use Internet-Drafts as reference 50 material or to cite them other than as "work in progress." 52 This Internet-Draft will expire on January 18, 2018. 54 Copyright Notice 56 Copyright (c) 2017 IETF Trust and the persons identified as the 57 document authors. All rights reserved. 59 This document is subject to BCP 78 and the IETF Trust's Legal 60 Provisions Relating to IETF Documents 61 (http://trustee.ietf.org/license-info) in effect on the date of 62 publication of this document. Please review these documents 63 carefully, as they describe your rights and restrictions with respect 64 to this document. Code Components extracted from this document must 65 include Simplified BSD License text as described in Section 4.e of 66 the Trust Legal Provisions and are provided without warranty as 67 described in the Simplified BSD License. 69 Table of Contents 71 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 72 2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3 73 3. Flooding Scope . . . . . . . . . . . . . . . . . . . . . . . 4 74 4. Link-Overload sub-TLV . . . . . . . . . . . . . . . . . . . . 4 75 4.1. OSPFv2 Link-overload sub-TLV . . . . . . . . . . . . . . 4 76 4.2. Remote IPv4 address sub-TLV . . . . . . . . . . . . . . . 4 77 4.3. Local/Remote Interface ID . . . . . . . . . . . . . . . . 5 78 4.4. OSPFv3 Link-Overload sub-TLV . . . . . . . . . . . . . . 6 79 5. Elements of procedure . . . . . . . . . . . . . . . . . . . . 6 80 5.1. Point-to-point links . . . . . . . . . . . . . . . . . . 6 81 5.2. Broadcast/NBMA links . . . . . . . . . . . . . . . . . . 7 82 5.3. Point-to-multipoint links . . . . . . . . . . . . . . . . 7 83 5.4. Unnumbered interfaces . . . . . . . . . . . . . . . . . . 8 84 5.5. Hybrid Broadcast and P2MP interfaces . . . . . . . . . . 8 85 6. Backward compatibility . . . . . . . . . . . . . . . . . . . 8 86 7. Applications . . . . . . . . . . . . . . . . . . . . . . . . 8 87 7.1. Pseudowire Services . . . . . . . . . . . . . . . . . . . 8 88 7.2. Controller based Traffic Engineering Deployments . . . . 9 89 7.3. L3VPN Services and sham-links . . . . . . . . . . . . . . 10 90 7.4. Hub and spoke deployment . . . . . . . . . . . . . . . . 11 91 8. Security Considerations . . . . . . . . . . . . . . . . . . . 11 92 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 93 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11 94 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 95 11.1. Normative References . . . . . . . . . . . . . . . . . . 12 96 11.2. Informative References . . . . . . . . . . . . . . . . . 12 98 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 100 1. Introduction 102 When a node is being prepared for a planned maintenance or upgrade, 103 [RFC6987] provides mechanisms to advertise the node being in an 104 overload state by setting all outgoing link costs to MAX-METRIC 105 (0xffff). These procedures are specific to the maintenance activity 106 on a node and cannot be used when a single link attached to the node 107 requires maintenance. 109 In traffic-engineering deployments, LSPs need to be diverted from the 110 link without disrupting the services. It is useful to be able to 111 advertise the impending maintenance activity on the link and to have 112 LSP re-routing policies at the ingress to route the LSPs away from 113 the link. 115 Many OSPFv2 or OSPFv3 deployments run on overlay networks provisioned 116 by means of pseudo-wires or L2-circuits. Prior to devices in the 117 underlying network going offline for maintenance, it is useful to 118 divert the traffic away from the node before the maintenance is 119 actually scheduled. Since the nodes in the underlying network are 120 not visible to OSPF, the existing stub router mechanism described in 121 [RFC6987] cannot be used. An application specific to this use case 122 is described in Section 7.1 124 This document provides mechanisms to advertise link-overload state in 125 the flexible encodings provided by OSPFv2 Prefix/Link Attribute 126 Advertisement([RFC7684]). Throughout this document, OSPF is used 127 when the text applies to both OSPFv2 and OSPFv3. OSPFv2 or OSPFv3 is 128 used when the text is specific to one version of the OSPF protocol. 130 2. Motivation 132 The motivation of this document is to reduce manual intervention 133 during maintenance activities. The following objectives help to 134 accomplish this in a range of deployment scenarios. 136 1. Advertise impending maintenance activity so that traffic from 137 both directions can be diverted away from the link. 139 2. Allow the solution to be backward compatible so that nodes that 140 do not understand the new advertisement do not cause routing 141 loops. 143 3. Advertise the maintenance activity to other nodes in the network 144 so that LSP ingress routers/controllers can learn of the 145 impending maintenance activity and apply specific policies to re- 146 route the LSPs for traffic-engineering based deployments. 148 4. Allow the link to be used as last resort link to prevent traffic 149 disruption when alternate paths are not available. 151 3. Flooding Scope 153 The link-overload information is flooded in area scoped Extended Link 154 Opaque LSA [RFC7684]. The Link-Overload sub-TLV MAY be processed by 155 the head-end nodes or the controller as described in the Section 7. 156 The procedures for processing the Link-Overload sub-TLV is described 157 in Section 5. 159 4. Link-Overload sub-TLV 161 4.1. OSPFv2 Link-overload sub-TLV 163 The Link-Overload sub-TLV identifies the link being in overload 164 state. It is carried in extended Link TLV in the Extended Link 165 Opaque LSA as defined in [RFC7684]. 167 0 1 2 3 168 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 1 169 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 170 | Type | Length | 171 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 173 Figure 1: Link-Overload sub-TLV for OSPFv2 175 Type : TBA (suggested value 5) 177 Length: 0 179 4.2. Remote IPv4 address sub-TLV 181 This sub-TLV specifies the IPv4 address of the link on remote side. 182 It is carried in extended Link TLV as defined in [RFC7684].This sub- 183 TLV is optional and MAY be advertised in area scoped Extended Link 184 Opaque LSA to identify the link when there are multiple parallel 185 interfaces between two nodes. 187 0 1 2 3 188 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 1 189 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 190 | Type | Length | 191 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 192 | Remote IPv4 address | 193 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 195 Figure 2: Remote IPv4 address sub-TLV 197 Type : TBA (suggested value 4) 199 Length: 4 201 Value: Remote IPv4 address. The remote IP4 address is used to 202 identify the particular link when there are multiple parallel links 203 between two nodes. 205 4.3. Local/Remote Interface ID 207 This sub-TLV specifies local and remote interface identifiers. It is 208 carried in extended Link TLV as defined in [RFC7684].This sub-TLV is 209 optional and MAY be advertised in area scoped Extended Link Opaque 210 LSA to identify the link when there are multiple parallel unnumbered 211 interfaces between two nodes. The local interface-id is generally 212 readily available. One of the mechanisms to obtain remote interface- 213 id is described in [RFC4203]. 215 0 1 2 3 216 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 1 217 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 218 | Type | Length | 219 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 220 | Local Interface ID | 221 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 222 | Remote Interface ID | 223 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 225 Figure 3: Local/Remote Interface ID sub-TLV 227 Type : TBA (suggested value 11) 229 Length: 8 230 Value: 4 octets of Local Interface ID followed by 4 octets of Remote 231 interface ID. 233 4.4. OSPFv3 Link-Overload sub-TLV 235 The definition of OSPFv3 Link-Overload sub-TLV is defined below. The 236 area scope advertisement of Link-Overload sub-TLV for OSPFv3 will be 237 described in a separate document. 239 0 1 2 3 240 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 1 241 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 242 | Type | Length | 243 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 245 Figure 4: Link-Overload sub-TLV for OSPFv3 247 Type : TBA (Suggested value 4) 249 Length: 0 251 5. Elements of procedure 253 The Link-Overload sub-TLV indicates that the link identified by the 254 sub-TLV is overloaded. The node that has the link to be taken out of 255 service SHOULD originate the Link-Overload sub-TLV in the Extended 256 Link TLV in the Extended Link Opaque LSA as defined in [RFC7684] for 257 OSPFv2. The Link-Overload information is carried as a property of 258 the link and is flooded across the area. This information can be 259 used by ingress routers or controllers to take special actions. An 260 application specific to this use case is described in Section 7.2. 262 The precise action taken by the remote node at the other end of the 263 link identified as overloaded depends on the link type. 265 5.1. Point-to-point links 267 The node that has the link to be taken out of service MUST set metric 268 of the link to MAX-METRIC (0xffff) and re- originate the Router-LSA. 269 The TE metric SHOULD be set to MAX-TE-METRIC -1 (0xfffffffe) and the 270 node SHOULD re-originate the TE Link Opaque LSAs. When a Link- 271 Overload sub-TLV is received for a point-to-point link, the remote 272 node MUST identify the local link which corresponds to the overloaded 273 link and set the metric to MAX-METRIC (0xffff)and the remote node 274 MUST re-originate the router-LSA with the changed metric. The TE 275 metric SHOULD be set to MAX-TE-METRIC -1 (0xfffffffe) and the TE 276 opaque LSA for the link SHOULD be re-originated with new value. 278 Extended link opaque LSAs and the Extended link TLV are not scoped 279 for multi-topology [RFC4915]. In multi-topology deployments 280 [RFC4915], the Link-Overload sub-TLV carried in an Extended Link 281 opaque LSA corresponds to all the topologies the link belongs to. 282 The receiver node SHOULD change the metric in the reverse direction 283 corresponding to all the topologies to which the reverse link belongs 284 and re-originate the Router LSA as defined in [RFC4915]. 286 When the originator of the Link-Overload sub-TLV purges the Extended 287 Link Opaque LSA or re-originates it without the Link-Overload sub- 288 TLV, the remote node must re-originate the appropriate LSAs with the 289 metric and TE metric values set to their original values. 291 5.2. Broadcast/NBMA links 293 Broadcast or NBMA networks in OSPF are represented by a star topology 294 where the Designated Router (DR) is the central point to which all 295 other routers on the broadcast or NBMA network connect logically. As 296 a result, routers on the broadcast or NBMA network advertise only 297 their adjacency to the DR. Routers that do not act as DR do not form 298 or advertise adjacencies with each other. For the Broadcast links, 299 the MAX-METRIC on the remote link cannot be changed since all the 300 neighbours are on same link. Setting the link cost to MAX-METRIC 301 would impact paths going via all neighbours. 303 The node that has the link to be taken out of service MUST set metric 304 of the link to MAX-METRIC(0xffff) and re-originate the Router-LSA. 305 The TE metric SHOULD be set to MAX-TE-METRIC -1(0xfffffffe) and the 306 node SHOULD re-originate the TE Link Opaque LSAs. For a broadcast 307 link, the two part metric as described in [RFC8042] is used. The 308 node originating the Link-Overload sub-TLV MUST set the metric in the 309 Network-to-Router Metric sub-TLV to MAX-METRIC 0xffff for OSPFv2 and 310 OSPFv3 and re-originate the LSAs the TLV is carried-in. The nodes 311 that receive the two part metric should follow the procedures 312 described in [RFC8042]. The backward compatibility procedures 313 described in [RFC8042] should be followed to ensure loop free 314 routing. 316 5.3. Point-to-multipoint links 318 Operation for the point-to-multipoint links is similar to the point- 319 to-point links. When a Link-Overload sub-TLV is received for a 320 point-to-multipoint link the remote node MUST identify the neighbour 321 which corresponds to the overloaded link and set the metric to MAX- 322 METRIC (0xffff). The remote node MUST re-originate the Router-LSA 323 with the changed metric and flood into the OSPF area. 325 5.4. Unnumbered interfaces 327 Unnumbered interface do not have a unique IP addresses and borrow 328 address from other interfaces. [RFC2328] describes procedures to 329 handle unnumbered interfaces in the context of the Router LSA. We 330 apply a similar procedure to the Extended Link TLV carrying the Link- 331 Overload sub-TLV in to handle unnumbered interfaces. The link-data 332 field in the Extended Link TLV carries the Local interface-id instead 333 of the IP address. The Local/Remote Interface ID sub-TLV MUST be 334 originated when there are multiple parallel unnumbered interfaces 335 between two nodes. One of the mechanisms to obtain interface-id of 336 the remote side are defined in [RFC4203]. 338 5.5. Hybrid Broadcast and P2MP interfaces 340 Hybrid Broadcast and P2MP interfaces represent a broadcast network 341 modeled as P2MP interfaces. [RFC6845] describes procedures to handle 342 these interfaces. Operation for the Hybrid interfaces is similar to 343 the P2MP interfaces. When a Link-Overload sub-TLV is received for a 344 hybrid link the remote node MUST identify the neighbour which 345 corresponds to the overloaded link and set the metric to MAX-METRIC 346 (0xffff). All the remote nodes connected to originator MUST re- 347 originate the Router-LSA with the changed metric and flood into the 348 OSPF area. 350 6. Backward compatibility 352 The mechanism described in the document is fully backward compatible. 353 It is required that the originator of the Link-Overload sub-TLV as 354 well as the node at the remote end of the link identified as 355 overloaded understand the extensions defined in this document. In 356 the case of broadcast links, the backward compatibility procedures as 357 described in [RFC8042] are applicable. 359 7. Applications 361 7.1. Pseudowire Services 363 Many service providers offer pseudo-wire services to customers using 364 L2 circuits. The IGP protocol that runs in the customer network 365 would also run over the pseudo-wire to create seamless private 366 network for the customer. Service providers want to offer overload 367 kind of functionality when the PE device is taken-out for 368 maintenance. The provider should guarantee that the PE is taken out 369 for maintenance only after the service is successfully diverted on an 370 alternate path. There can be large number of customers attached to a 371 PE node and the remote end-points for these pseudo-wires are spread 372 across the service provider's network. It is a tedious and error- 373 prone process to change the metric for all pseudo-wires in both 374 directions. The link-overload feature simplifies the process by 375 increasing the metric on the link in the reverse direction as well so 376 that traffic in both directions is diverted away from the PE 377 undergoing maintenance. The Link-Overload feature allows the link to 378 be used as a last resort link so that traffic is not disrupted when 379 alternative paths are not available. 381 Private VLAN 382 ======================================= 383 | | 384 | | 385 | ------PE3---------------PE4------CE3 386 | / \ 387 | / \ 388 CE1---------PE1----------PE2---------CE2 389 | \ 390 | \ 391 | ------CE4 392 | | 393 | | 394 | | 395 ================================= 396 Private VLAN 398 Figure 5: Pseudowire Services 400 In the example shown in Figure 5, when the PE1 node is going for 401 maintenance, service providers set the PE1 to overload state. The 402 PE1 going in overload state triggers all the CEs (In this example 403 CE1)connected to the PE to set their pseudowire links passing via PE1 404 to link-overload state. The mechanisms used to communicate between 405 PE1 and CE1 is outside the scope of this document. CE1 sets the 406 link-overload state on its private VLAN connecting CE3, CE2 and CE4 407 and modifies the metric to MAX_METRIC and floods the information, the 408 remote end of the link at CE3, CE2, and CE4 also set the metric on 409 the link to MAX-METRIC and the traffic from both directions gets 410 diverted away from the link. 412 7.2. Controller based Traffic Engineering Deployments 414 In controller-based deployments where the controller participates in 415 the IGP protocol, the controller can also receive the link-overload 416 information as a warning that link maintenance is imminent. Using 417 this information, the controller can find alternate paths for traffic 418 which use the affected link. The controller can apply various 419 policies and re-route the LSPs away from the link undergoing 420 maintenance. If there are no alternate paths satisfying the traffic 421 engineering constraints, the controller might temporarily relax those 422 constraints and put the service on a different path. Increasing the 423 link metric alone does not specify the maintenance activity as the 424 metric could increase in events such as LDP-IGP synchronisation. An 425 explicit indication from the router using the link-overload sub-TLV 426 is needed to inform the Controller or head-end routers. 428 _____________ 429 | | 430 -------------| Controller |-------------- 431 | |____________ | | 432 | | 433 |--------- Primary Path ------------------| 434 PE1---------P1----------------P2---------PE2 435 | | 436 | | 437 |________P3________| 439 Alternate Path 441 Figure 6: Controller based Traffic Engineering 443 In the above example, PE1->PE2 LSP is set-up to satisfy a constraint 444 of 10 Gbps bandwidth on each link. The links P1->P3 and P3->P2 have 445 only 1 Gbps capacity and there is no alternate path satisfying the 446 bandwidth constraint of 10GB. When P1->P2 link is being prepared for 447 maintenance, the controller receives the link-overload information, 448 as there is no alternate path available which satisfies the 449 constraints, controller chooses a path that is less optimal and 450 temporarily sets up an alternate path via P1->P3->P2. Once the 451 traffic is diverted, the P1->P2 link can be taken out of service for 452 maintenance/upgrade. 454 7.3. L3VPN Services and sham-links 456 Many service providers offer L3VPN services to customers and CE-PE 457 links run OSPF [RFC4577]. When PE goes for maintenance, all the 458 links on the PE can be set to link-overlaod state which will gurantee 459 that the traffic from CEs also gets diverted. The interaction 460 between OSPF and BGP is outside the scope of this document. 462 Another useful usecase is when ISPs provide sham-link services to 463 customers [RFC4577].When PE goes for maintenance, all sham-links on 464 the PE can be set to link-overload state and traffic can be divered 465 from both ends without having to touch the configurations on the 466 remote end of the sham-links. 468 7.4. Hub and spoke deployment 470 OSPF is largely deployed in Hub and Spoke deployments with a number 471 of spokes connecting to the Hub. It is a general practice to deploy 472 multiple Hubs with all spokes connecting to these Hubs to achieve 473 redundancy. When a Hub node goes down for maintenance, all links on 474 the Hub can be set to link-overload state and traffic gets divered 475 from spoke sites as well without having to make configuration changes 476 on the spokes. 478 8. Security Considerations 480 This document does not introduce any further security issues other 481 than those discussed in [RFC2328] and [RFC5340]. 483 9. IANA Considerations 485 This specification updates one OSPF registry: 487 OSPF Extended Link TLVs Registry 489 i) TBD - Link-Overload sub-TLV 491 OSPFV3 Router Link TLV Registry 493 i) TBD - Link-Overload sub-TLV 495 OSPF RI TLV Registry 497 i) TBD - Link-Overload sub-TLV 499 BGP-LS Link NLRI Registry [RFC7752] 501 i)TBD - Link-Overload sub-TLV 503 10. Acknowledgements 505 Thanks to Chris Bowers for valuable inputs and edits to the document. 506 Thanks to Jeffrey Zhang,Acee Lindem and Ketan Talaulikar for inputs. 507 Thanks to Karsten Thomann for careful review and inputs on the 508 applications where link-overload is useful. 510 11. References 512 11.1. Normative References 514 [RFC6845] Sheth, N., Wang, L., and J. Zhang, "OSPF Hybrid Broadcast 515 and Point-to-Multipoint Interface Type", RFC 6845, 516 DOI 10.17487/RFC6845, January 2013, 517 . 519 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 520 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 521 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 522 2015, . 524 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 525 S. Ray, "North-Bound Distribution of Link-State and 526 Traffic Engineering (TE) Information Using BGP", RFC 7752, 527 DOI 10.17487/RFC7752, March 2016, 528 . 530 [RFC8042] Zhang, Z., Wang, L., and A. Lindem, "OSPF Two-Part 531 Metric", RFC 8042, DOI 10.17487/RFC8042, December 2016, 532 . 534 11.2. Informative References 536 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 537 Requirement Levels", BCP 14, RFC 2119, 538 DOI 10.17487/RFC2119, March 1997, 539 . 541 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 542 DOI 10.17487/RFC2328, April 1998, 543 . 545 [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in 546 Support of Generalized Multi-Protocol Label Switching 547 (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005, 548 . 550 [RFC4577] Rosen, E., Psenak, P., and P. Pillay-Esnault, "OSPF as the 551 Provider/Customer Edge Protocol for BGP/MPLS IP Virtual 552 Private Networks (VPNs)", RFC 4577, DOI 10.17487/RFC4577, 553 June 2006, . 555 [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. 556 Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", 557 RFC 4915, DOI 10.17487/RFC4915, June 2007, 558 . 560 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 561 for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, 562 . 564 [RFC6987] Retana, A., Nguyen, L., Zinin, A., White, R., and D. 565 McPherson, "OSPF Stub Router Advertisement", RFC 6987, 566 DOI 10.17487/RFC6987, September 2013, 567 . 569 Authors' Addresses 571 Shraddha Hegde 572 Juniper Networks, Inc. 573 Embassy Business Park 574 Bangalore, KA 560093 575 India 577 Email: shraddha@juniper.net 579 Pushpasis Sarkar 580 Individual 582 Email: pushpasis.ietf@gmail.com 584 Hannes Gredler 585 Individual 587 Email: hannes@gredler.at 589 Mohan Nanduri 590 ebay Corporation 591 2025 Hamilton Avenue 592 San Jose, CA 98052 593 US 595 Email: mnanduri@ebay.com 596 Luay Jalil 597 Verizon 599 Email: luay.jalil@verizon.com