idnits 2.17.1 draft-ietf-ospf-link-overload-02.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 7, 2016) is 2840 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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-10) exists of draft-ietf-ospf-two-part-metric-01 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--).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 8, 2017 H. Gredler 6 Individual 7 M. Nanduri 8 Microsoft Corporation 9 L. Jalil 10 Verizon 11 July 7, 2016 13 OSPF Link Overload 14 draft-ietf-ospf-link-overload-02 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 8, 2017. 54 Copyright Notice 56 Copyright (c) 2016 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. Link overload sub-TLV . . . . . . . . . . . . . . . . . . . . 4 74 3.1. OSPF Link overload sub-TLV . . . . . . . . . . . . . . . 4 75 4. Flooding Scope . . . . . . . . . . . . . . . . . . . . . . . 4 76 4.1. Area scope flooding . . . . . . . . . . . . . . . . . . . 4 77 4.2. Link scope flooding . . . . . . . . . . . . . . . . . . . 5 78 5. Elements of procedure . . . . . . . . . . . . . . . . . . . . 5 79 5.1. Point-to-point links . . . . . . . . . . . . . . . . . . 5 80 5.2. Broadcast/NBMA links . . . . . . . . . . . . . . . . . . 6 81 5.3. Point-to-multipoint links . . . . . . . . . . . . . . . . 6 82 5.4. Unnumbered interfaces . . . . . . . . . . . . . . . . . . 6 83 6. Backward compatibility . . . . . . . . . . . . . . . . . . . 7 84 7. Applications . . . . . . . . . . . . . . . . . . . . . . . . 7 85 7.1. Pseudowire Services . . . . . . . . . . . . . . . . . . . 7 86 7.2. Controller based Traffic Engineering Deployments . . . . 8 87 8. Security Considerations . . . . . . . . . . . . . . . . . . . 8 88 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 89 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 90 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 91 11.1. Normative References . . . . . . . . . . . . . . . . . . 9 92 11.2. Informative References . . . . . . . . . . . . . . . . . 10 93 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 95 1. Introduction 97 When a node is being prepared for a planned maintenance or upgrade, 98 [RFC6987] provides mechanisms to advertise the node being in an 99 overload state by setting all outgoing link costs to MAX-METRIC 100 (0xffff). These procedures are specific to the maintenance activity 101 on a node and cannot be used when a single link attached to the node 102 requires maintenance. 104 In traffic-engineering deployments, LSPs need to be moved away from 105 the link without disrupting the services. It is useful to be able to 106 advertise the impending maintenance activity on the link and to have 107 LSP re-routing policies at the ingress to route the LSPs away from 108 the link. 110 Many OSPFv2 or OSPFv3 deployments run on overlay networks provisioned 111 by means of pseudo-wires or L2-circuits. When the devices in the 112 underlying network go for maintenance, it is useful to divert the 113 traffic away from the node before the maintenance is actually 114 scheduled. Since the nodes in the underlying network are not visible 115 to OSPF, the existing stub router mechanism described in [RFC6987] 116 cannot be used. Application specific to this use case is described 117 in Section 7.1 119 This document provides mechanisms to advertise link overload state in 120 the flexible encodings provided by RI LSA( [RFC7770]) for OSPFv2 and 121 OSPFv3. Throughout this document, OSPF is used when the text applies 122 to both OSPFv2 and OSPFv3. OSPFv2 or OSPFv3 is used when the text is 123 specific to one version of the OSPF protocol. 125 2. Motivation 127 The motivation of this document is to reduce manual intervention 128 during maintenance activities. The following objectives help to 129 accomplish this in a range of deployment scenarios. 131 1. Advertise impending maintenance activity so that the traffic from 132 both directions can be diverted away from the link. 134 2. Allow the solution to be backward compatible so that nodes that 135 do not understand the new advertisement do not cause routing 136 loops. 138 3. Advertise the maintenance activity to other nodes in the network 139 so that LSP ingress routers/controllers can learn the impending 140 maintenance activity and apply specific policies to re-route the 141 LSP for traffic-engineering based deployments. 143 4. Allow the link to be used as last resort link to prevent traffic 144 disruption when alternate paths are not available. 146 3. Link overload sub-TLV 148 3.1. OSPF Link overload sub-TLV 150 The Link Overload sub-TLV is defined as below. This sub-TLV is 151 attached to the Link TLV [RFC3630] and carried in RI LSA [RFC7770] 152 for OSPFv2 and OSPFv3 154 0 1 2 3 155 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 1 156 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 157 | Type | Length | 158 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 160 Figure 1: Link Overload sub-TLV for OSPFv2 162 Type : TBA (suggested value 35) 164 Length: 0 166 4. Flooding Scope 168 The link overload information can be flood in area scoped RI LSA or 169 link scoped RI LSA or both based on the need of the application. 170 Section 7 describes applications requiring area scope as well as link 171 scope Link-overload information. The Link TLV and the link-overload 172 sub-tlv MAY appear in any instance of the RI-LSA. 174 4.1. Area scope flooding 176 For OSPFv2, Link overload Sub-TLV is carried in the Link TLV as 177 defined in [RFC3630]. Link TLV is carried in area scoped RI LSA 178 [RFC7770]. When there are more than one parallel links between two 179 nodes, the link carrying link-overload information, need to be 180 uniquely identified among the parallel links. Remote interface IP 181 address sub-tlv as defined by [RFC3630] is also carried in the Link 182 TLV which is used by the remote nodes to uniquely identify the 183 overloaded link. 185 For OSPFv3, Link-overload sub-tlv is carried in Link TLV as defined 186 in [RFC5329] Link TLV is carried in the OSPFv3 area scoped RI-LSA 187 [RFC7770] 189 4.2. Link scope flooding 191 The link local scope RI-LSA corresponds to the link on which the LSA 192 arrives and there is no need to explicitly carry the link TLV. The 193 Link overload sub-TLV is carried in the RI-LSA for both OSPFv2 and 194 OSPFv3. 196 5. Elements of procedure 198 The Link Overload sub-TLV indicates that the link identified in which 199 it is carried is overloaded. The node that has the link to be taken 200 out of service SHOULD originate the Link Overload sub-TLV in the Link 201 TLV in the RI LSA as defined in [RFC7770]. The link-overload 202 information is carried as a property of the link and is flooded 203 across the area. This information can be used by ingress routers or 204 controllers to take special actions. Application specific to this 205 use case is described in Section 7.2. 207 The precise action taken by the remote node at the other end of the 208 link identified as overloaded depends on the link type. 210 5.1. Point-to-point links 212 The node that has the link to be taken out of service SHOULD set 213 metric of the link to MAX-METRIC (0xffff) and re- originate the 214 Router-LSA. The TE metric SHOULD be set to MAX-TE-METRIC-1 215 (0xfffffffe) and the node SHOULD re-originate the TE Link Opaque 216 LSAs. When a Link Overload sub-TLV is received for a point-to-point 217 link either by link local or area scoped RI-LSA, the remote node 218 SHOULD identify the local link which corresponds to the overloaded 219 link and set the metric to MAX-METRIC (0xffff). The remote node MUST 220 re-originate the router-LSA with the changed metric and flood into 221 the OSPF area. The TE metric SHOULD be set to MAX-TE-METRIC-1 222 (0xfffffffe) and the TE opaque LSA for the link MUST be re-originated 223 with new value. 225 In multi-topology deployments [RFC4915], the Link overload Sub-TLV 226 carried in an RI LSA corresponds to all the topologies the link 227 belongs to. The receiver node SHOULD change the metric in the 228 reverse direction corresponding to all the topologies to which the 229 reverse link belongs. 231 When the originator of the Link Overload sub-TLV purges the RI-LSA or 232 re-originates it without the Link Overload sub-TLV, the remote node 233 must re-originate the appropriate LSAs with the metric and TE metric 234 values set to their original values. 236 5.2. Broadcast/NBMA links 238 Broadcast or NBMA networks in OSPF are represented by a star topology 239 where the Designated Router (DR) is the central point to which all 240 other routers on the broadcast or NBMA network connect logically. As 241 a result, routers on the broadcast or NBMA network advertise only 242 their adjacency to the DR. Routers that do not act as DR do not form 243 or advertise adjacencies with each other. For the Broadcast links, 244 the MAX-METRIC on the remote link cannot be changed since all the 245 neighbours are on same link. Setting the link cost to MAX-METRIC 246 would impact paths going via all neighbours. 248 The node that has the link to be taken out of service SHOULD set 249 metric of the link to MAX-METRIC (0xffff) and re-originate the 250 Router-LSA. The TE metric SHOULD be set to MAX-TE-METRIC- 251 1(0xfffffffe) and the node SHOULD re-originate the TE Link Opaque 252 LSAs. For a broadcast link, the two part metric as described in 253 [I-D.ietf-ospf-two-part-metric] is used. The node originating the 254 Link Overload sub-TLV MUST set the metric in the Network-to-Router 255 Metric sub-TLV to MAX-METRIC 0xffff for OSPFv2 and OSPFv3 and re- 256 originate the LSAs the TLV is carried-in. 258 The nodes that receive the two part metric should follow the 259 procedures described in [I-D.ietf-ospf-two-part-metric]. The 260 backward compatibility procedures described in 261 [I-D.ietf-ospf-two-part-metric] should be followed to ensure loop 262 free routing. 264 5.3. Point-to-multipoint links 266 Operation for the point-to-multipoint links is similar to the point- 267 to-point links. When a Link Overload sub-TLV is received for a 268 point-to-multipoint link the remote node SHOULD identify the link 269 which corresponds to the overloaded link and set the metric to MAX- 270 METRIC (0xffff). The remote node MUST re-originate the Router-LSA 271 with the changed metric and flood into the OSPF area. 273 5.4. Unnumbered interfaces 275 Unnumbered interface do not have a unique IP addresses and borrow 276 address from other interfaces. The Link TLV carries the local and 277 remote interface ids to uniquely identify the link when there are 278 more than one parallel links between the nodes. Procedures to obtain 279 interface-id of the remote side is defined in [RFC4203] and are 280 applicable to the Link TLV added in the RI LSA for the purpose of 281 carrying the Link overload sub-tlv. 283 6. Backward compatibility 285 The mechanism described in the document is fully backward 286 compatible.It is required that the originator of the Link Overload 287 sub-TLV as well as the node at the remote end of the link identified 288 as overloaded understand the extensions defined in this document. In 289 the case of broadcast links, the backward compatibility procedures as 290 described in [I-D.ietf-ospf-two-part-metric] are applicable. . 292 7. Applications 294 7.1. Pseudowire Services 296 ---------PE3----------------PE4---------- 297 | | 298 | | 299 CE1---------PE1----------------PE2---------CE2 300 | | 301 | | 302 ----------------------------------------- 303 Private VLAN 305 Figure 2: Pseudowire Services 307 Many service providers offer pseudo-wire services to customers using 308 L2 circuits. The IGP protocol that runs in the customer network 309 would also run over the pseudo-wire to create seamless private 310 network for the customer. Service providers want to offer overload 311 kind of functionality when the PE device is taken-out for 312 maintenance. The provider should guarantee that the PE is taken out 313 for maintenance only after the service is successfully diverted on an 314 alternate path. There can be large number of customers attached to a 315 PE node and the remote end-points for these pseudo-wires are spread 316 across the service provider's network. It is a tedious and error- 317 prone process to change the metric for all pseudo-wires in both 318 directions.The link overload feature simplifies the process by 319 increasing the metric on the link in the reverse direction as well so 320 that traffic in both directions is diverted away from the PE 321 undergoing maintenance. The link-overload feature allows the link to 322 be used as a last resort link so that traffic is not disrupted when 323 alternative paths are not available. 325 7.2. Controller based Traffic Engineering Deployments 327 _____________ 328 | | 329 -------------| Controller |-------------- 330 | |____________ | | 331 | | 332 |--------- Primary Path ------------------| 333 PE1---------P1----------------P2---------PE2 334 | | 335 | | 336 |________P3________| 338 Alternate Path 340 Figure 3: Controller based Traffic Engineering 342 In controller-based deployments where the controller participates in 343 the IGP protocol, the controller can also receive the link-overload 344 information as a warning that link maintenance is imminent. Using 345 this information, the controller can find alternate paths for traffic 346 which use the affected link. The controller can apply various 347 policies and re-route the LSPs away from the link undergoing 348 maintenance. If there are no alternate paths satisfying the traffic 349 engineering constraints, the controller might temporarily relax those 350 constraints and put the service on a different path. 352 In the above example, PE1->PE2 LSP is set-up which satisfies a 353 constraint of 10 GB bandwidth on each link.The links P1->P3 and 354 P3->P2 have only 1 GB capacity. and there is no alternate path 355 satisfying the bandwidth constraint of 10GB. When P1->P2 link is 356 being prepared for maintenance, the controller receives the link- 357 overload information, as there is no alternate path available which 358 satisfies the constraints, controller chooses a path that is less 359 optimal and sets up an alternate path via P1->P3->P2 temporarily. 360 Once the traffic is diverted, P1->P2 link can be taken out for 361 maintenance/upgrade. 363 8. Security Considerations 365 This document does not introduce any further security issues other 366 than those discussed in [RFC2328] and [RFC5340]. 368 9. IANA Considerations 370 This specification updates one OSPF registry: 372 OSPF Link TLVs Registry 374 i) TBD - Link Overload sub TLV 376 OSPFV3 Link TLV Registry 378 i) TBD - Link Overload sub TLV 380 OSPF Router Information (RI)TLVs Registry 382 i) TBD - Link TLV 384 10. Acknowledgements 386 Thanks to Chris Bowers for valuable inputs and edits to the document. 387 Thanks to Jeffrey Zhang and Acee Lindem for inputs. 389 11. References 391 11.1. Normative References 393 [I-D.ietf-ospf-two-part-metric] 394 Wang, L., Lindem, A., DuBois, D., Julka, V., and T. 395 McMillan, "OSPF Two-part Metric", draft-ietf-ospf-two- 396 part-metric-01 (work in progress), July 2015. 398 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 399 (TE) Extensions to OSPF Version 2", RFC 3630, 400 DOI 10.17487/RFC3630, September 2003, 401 . 403 [RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed., 404 "Traffic Engineering Extensions to OSPF Version 3", 405 RFC 5329, DOI 10.17487/RFC5329, September 2008, 406 . 408 [RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and 409 S. Shaffer, "Extensions to OSPF for Advertising Optional 410 Router Capabilities", RFC 7770, DOI 10.17487/RFC7770, 411 February 2016, . 413 11.2. Informative References 415 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 416 Requirement Levels", BCP 14, RFC 2119, 417 DOI 10.17487/RFC2119, March 1997, 418 . 420 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 421 DOI 10.17487/RFC2328, April 1998, 422 . 424 [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in 425 Support of Generalized Multi-Protocol Label Switching 426 (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005, 427 . 429 [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. 430 Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", 431 RFC 4915, DOI 10.17487/RFC4915, June 2007, 432 . 434 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 435 for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, 436 . 438 [RFC6987] Retana, A., Nguyen, L., Zinin, A., White, R., and D. 439 McPherson, "OSPF Stub Router Advertisement", RFC 6987, 440 DOI 10.17487/RFC6987, September 2013, 441 . 443 Authors' Addresses 445 Shraddha Hegde 446 Juniper Networks, Inc. 447 Embassy Business Park 448 Bangalore, KA 560093 449 India 451 Email: shraddha@juniper.net 453 Pushpasis Sarkar 454 Individual 456 Email: pushpasis.ietf@gmail.com 457 Hannes Gredler 458 Individual 460 Email: hannes@gredler.at 462 Mohan Nanduri 463 Microsoft Corporation 464 One Microsoft Way 465 Redmond, WA 98052 466 US 468 Email: mnanduri@microsoft.com 470 Luay Jalil 471 Verizon 473 Email: luay.jalil@verizon.com