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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Z. Hu 3 Internet-Draft H. Chen 4 Intended status: Standards Track Huawei Technologies 5 Expires: October 2, 2019 H. Chen 6 China Telecom 7 P. Wu 8 Huawei Technologies 9 March 31, 2019 11 SRv6 Path Egress Protection 12 draft-hu-rtgwg-srv6-egress-protection-01 14 Abstract 16 This document describes protocol extensions and procedures for 17 protecting the egress node of a Segment Routing for IPv6 (SRv6) path. 19 Requirements Language 21 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 22 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 23 document are to be interpreted as described in RFC 2119 [RFC2119]. 25 Status of This Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at https://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on October 2, 2019. 42 Copyright Notice 44 Copyright (c) 2019 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (https://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 60 2. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 2 61 3. SR Path Egress Protection . . . . . . . . . . . . . . . . . . 3 62 4. Extensions to IGP for Egress Protection . . . . . . . . . . . 5 63 4.1. Extensions to IS-IS . . . . . . . . . . . . . . . . . . . 5 64 4.2. Extensions to OSPF . . . . . . . . . . . . . . . . . . . 7 65 5. Behavior for SRv6 Mirror SID . . . . . . . . . . . . . . . . 9 66 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 67 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 68 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 69 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 70 9.1. Normative References . . . . . . . . . . . . . . . . . . 10 71 9.2. Informative References . . . . . . . . . . . . . . . . . 11 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 74 1. Introduction 76 Fast protection of a transit node of a Segment Routing (SR) path is 77 described in [I-D.bashandy-rtgwg-segment-routing-ti-lfa] and 78 [I-D.hu-spring-segment-routing-proxy-forwarding]. However, these 79 documents do not discuss the procedures for fast protection of the 80 egress node of a Segment Routing for IPv6 (SRv6) path. 82 [RFC8400] describes the fast protection of egress node(s) of an MPLS 83 TE LSP tunnel including P2P TE LSP tunnel and P2MP TE LSP tunnel in 84 details. 86 This document specifies protocol extensions and procedures for fast 87 protection of the egress node of an SRv6 path. Egress node and 88 egress as well as fast protection and protection will be used 89 exchangeably. 91 2. Terminologies 93 The following terminologies are used in this document. 95 SR: Segment Routing 96 SRv6: SR for IPv6 98 SRH: Segment Routing Header 100 SID: Segment Identifier 102 LSP: Label Switched Path 104 TE: Traffic Engineering 106 P2MP: Point-to-MultiPoint 108 P2P: Point-to-Point 110 CE: Customer Edge 112 PE: Provider Edge 114 LFA: Loop-Free Alternate 116 TI-LFA: Topology Independent LFA 118 BFD: Bidirectional Forwarding Detection 120 VPN: Virtual Private Network 122 L3VPN: Layer 3 VPN 124 VRF: Virtual Routing and Forwarding 126 FIB: Forwarding Information Base 128 PLR: Point of Local Repair 130 BGP: Border Gateway Protocol 132 IGP: Interior Gateway Protocol 134 OSPF: Open Shortest Path First 136 IS-IS: Intermediate System to Intermediate System 138 3. SR Path Egress Protection 140 Figure 1 shows an example of protecting egress PE3 of a SR path, 141 which is from ingress PE1 to egress PE3. 143 Locator: A3:1::/64 144 ******* ******* VPN SID: A3:1::B100 145 [PE1]-----[P1]-----[PE3] 146 / | |& | \ PE3 Egress 147 / | |& | \ CEx Customer Edge 148 [CE1] | |& | [CE2] Px Non-Egress 149 \ | |& | / *** SR Path 150 \ | |& &&&&& | / &&& Backup Path 151 [PE2]-----[P2]-----[PE4] 152 Locator: A4:1::/64 153 VPN SID: A4:1::B100 154 Mirror SID: A4:1::3, protect A3:1::/64 156 Figure 1: Protecting SR Path Egress PE3 158 Node P1's pre-computed TI-LFA backup path for PE3 is from P1 to PE4 159 via P2. In normal operations, after receiving a packet with 160 destination PE3, P1 forwards the packet to PE3 according to its FIB. 161 When PE3 receives the packet, it sends the packet to CE2. 163 When PE3 fails, P1 detects the failure through BFD and forwards the 164 packet to PE4 via the backup path. When PE4 receives the packet, it 165 sends the packet to the same CE2. 167 In Figure 1, CE2 is dual home to PE3 and PE4. PE3 has a locator 168 A3:1::/64 and a VPN SID A3:1::B100. PE4 has a locator A4:1::/64 and 169 a VPN SID A4:1::B100. A mirror SID A4:1::3 is configured on PE4 for 170 protecting PE3 with locator A3:1::/64. 172 After the mirror SID is configured on a local PE (e.g., PE4), when 173 the local PE (e.g., BGP on the local PE) receives a prefix whose VPN 174 SID belongs to a remote PE (e.g., PE3) with the locator that is 175 protected by the local PE through mirror SID, the local PE (e.g., 176 PE4) creates a mapping from the remote PE's (e.g., PE3's) VPN SID and 177 the mirror SID to the local PE's (e.g., PE4's) VPN SID. The remote 178 PE is protected by the local PE. 180 For example, local PE4 has Prefix 1.1.1.1 with VPN SID:A4:1::B100, 181 when PE4 receives prefix 1.1.1.1 with remote PE3's VPN SID 182 A3:1::B100, it creates a mapping from remote PE3's VPN SID and the 183 mirror SID (i.e., "A3:1::B100, A4:1::3") to local PE4's VPN SID 184 (i.e., "A4:1::B100"). 186 Node P1's pre-computed TI-LFA backup path for destination PE3 having 187 locator A3:1::/64 is from P1 to PE4 having mirror SID A4:1::3. It is 188 installed as a T.Insert transit behavior. When P1 receives a packet 189 destined to PE3's VPN SID A3:1::B100, in normal operations, it 190 forwards the packet with source A1:1:: and destination PE3's VPN SID 191 A3:1::B100 according to the FIB using the destination PE3's VPN SID 192 A3:1::B100. 194 When PE3 fails, node P1 protects PE3 through sending the packet to 195 PE4 via the backup path pre-computed. P1 modifies the packet before 196 sending it to PE4. The modified packet has destination PE4 with 197 mirror SID A4:1::3, and SRH with PE3's VPN SID A3:1::B100 and the 198 mirror SID A4:1::3 (i.e., "A3:1::B100, A4:1::3; SL=1"). 200 When PE4 receives the packet, it forwards the packet to CE2 through 201 executing END.M instruction according to the local VPN SID (i.e., 202 A4:1::B100). 204 4. Extensions to IGP for Egress Protection 206 This section describes extensions to IS-IS and OSPF for advertising 207 the information about SRv6 path egress protection. 209 4.1. Extensions to IS-IS 211 A new sub-TLV, called IS-IS SRv6 End.m SID sub-TLV, is defined. It 212 is used in the SRv6 Locator TLV defined in 213 [I-D.bashandy-isis-srv6-extensions] to advertise SRv6 Segment 214 Identifiers (SIDs) with END.M function for SRv6 path egress 215 protection. The SRv6 End.m SIDs inherit the topology/algorithm from 216 the parent locator. The format of the sub-TLV is illustrated below. 218 0 1 2 3 219 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 1 220 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 221 | Type (TBD1) | Length | 222 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 223 | Flags | SRv6 Endpoint Function | 224 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 225 | SID (16 octets) | 226 : : 227 | | 228 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 229 | sub-TLVs | 230 : : 231 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 233 Figure 2: IS-IS SRv6 End.m SID sub-TLV 235 Type: TBD1 (suggested value 8) is to be assigned by IANA. 237 Length: variable. 239 Flags: 1 octet. No flags are currently defined. 241 SRv6 Endpoint Function: 2 octets. Add a new endpoint function 40 242 for end.m SID. 244 SID: 16 octets. This field contains the SRv6 end.m SID to be 245 advertised. 247 Two sub-TLVs are defined. One is the protected locators sub-TLV, and 248 the other is the protected SIDs sub-TLV. 250 A protected locators sub-TLV is used to carry the Locators to be 251 protected by the SRv6 mirror SID. It has the following format. 253 0 1 2 3 254 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 1 255 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 256 | Type (TBD2) | Length | 257 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 258 | Locator-Size | Locator (variable) ~ 259 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 260 : : 261 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 262 | Locator-Size | Locator (variable) ~ 263 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 265 Figure 3: IS-IS Protected Locators sub-TLV 267 Type: TBD2 (suggested value 1) is to be assigned by IANA. 269 Length: variable. 271 Locator-Size: 1 octet. Number of bits (1 - 128) in the Locator 272 field. 274 Locator: 1-16 octets. This field encodes an SRv6 Locator to be 275 protected by the SRv6 mirror SID. The Locator is encoded in the 276 minimal number of octets for the given number of bits. 278 A protected SIDs sub-TLV is used to carry the SIDs to be protected by 279 the SRv6 mirror SID. It has the following format. 281 0 1 2 3 282 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 1 283 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 284 | Type (TBD3) | Length | 285 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 286 | SID (16 octets) ~ 287 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 288 : : 289 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 290 | SID (16 octets) ~ 291 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 293 Figure 4: IS-IS Protected SIDs sub-TLV 295 Type: TBD3 (suggested value 2) is to be assigned by IANA. 297 Length: variable. 299 SID: 16 octets. This field encodes an SRv6 SID to be advertised. 301 4.2. Extensions to OSPF 303 Similarly, a new sub-TLV, called OSPF SRv6 End.m SID sub-TLV, is 304 defined. It is used to advertise SRv6 Segment Identifiers (SIDs) 305 with END.M function for SRv6 path egress protection. Its format is 306 illustrated below. 308 0 1 2 3 309 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 1 310 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 311 | Type (TBD4) | Length | 312 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 313 | Flags | SRv6 Endpoint Function | 314 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 315 | SID (16 octets) | 316 : : 317 | | 318 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 319 | sub-TLVs | 320 : : 321 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 323 Figure 5: OSPF SRv6 End.m SID sub-TLV 325 Type: TBD4 (suggested value 8) is to be assigned by IANA. 327 Length: variable. 329 Flags: 1 octet. No flags are currently defined. 331 SRv6 Endpoint Function: 2 octets. Add a new endpoint function 40 332 for end.m SID. 334 SID: 16 octets. This field contains the SRv6 end.m SID to be 335 advertised. 337 Two sub-TLVs are defined. One is the protected locators sub-TLV, and 338 the other is the protected SIDs sub-TLV. 340 A protected locators sub-TLV is used to carry the Locators to be 341 protected by the SRv6 mirror SID. It has the following format. 343 0 1 2 3 344 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 1 345 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 346 | Type (TBD5) | Length | 347 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 348 | Locator-Size | Locator (variable) ~ 349 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 350 : : 351 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 352 | Locator-Size | Locator (variable) ~ 353 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 355 Figure 6: OSPF Protected Locators sub-TLV 357 Type: TBD5 (suggested value 1) is to be assigned by IANA. 359 Length: variable. 361 Locator-Size: 1 octet. Number of bits (1 - 128) in the Locator 362 field. 364 Locator: 1-16 octets. This field encodes an SRv6 Locator to be 365 protected by the SRv6 mirror SID. The Locator is encoded in the 366 minimal number of octets for the given number of bits. 368 A protected SIDs sub-TLV is used to carry the SIDs to be protected by 369 the SRv6 mirror SID. It has the following format. 371 0 1 2 3 372 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 1 373 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 374 | Type (TBD6) | Length | 375 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 376 | SID (16 octets) ~ 377 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 378 : : 379 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 380 | SID (16 octets) ~ 381 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 383 Figure 7: OSPF Protected SIDs sub-TLV 385 Type: TBD6 (suggested value 2) is to be assigned by IANA. 387 Length: variable. 389 SID: 16 octets. This field encodes an SRv6 SID to be advertised. 391 5. Behavior for SRv6 Mirror SID 393 The "Endpoint with mirror protection to a vpn SID" function (End.M 394 for short) is a variant of the End function. The End.M is used for 395 SRv6 VPN egress protection. It is described below. 397 End.M: Mirror protection 398 When N receives a packet destined to S and S is a local End.M SID, 399 N does: 400 IF NH=SRH and SL = 1 ;; Ref1 401 SL-- 402 Map to a local VPN SID based on Mirror SID and SRH[SL] ;; Ref1 403 forward according to the local VPN SID ;; Ref2 404 ELSE 405 drop the packet 407 Figure 8: SRv6 Mirror SID Procedure 409 Ref1: An End.M SID must always be the penultimate SID. 411 Ref2: The rest forwarding behavior is the same as the corresponding 412 VPN sid. 414 6. Security Considerations 416 TBD 418 7. IANA Considerations 420 TBD 422 8. Acknowledgements 424 TBD 426 9. References 428 9.1. Normative References 430 [I-D.bashandy-isis-srv6-extensions] 431 Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and 432 Z. Hu, "IS-IS Extensions to Support Routing over IPv6 433 Dataplane", draft-bashandy-isis-srv6-extensions-05 (work 434 in progress), March 2019. 436 [I-D.hu-spring-segment-routing-proxy-forwarding] 437 Hu, Z., Chen, H., Yao, J., and C. Bowers, "Segment Routing 438 Proxy Forwarding", draft-hu-spring-segment-routing-proxy- 439 forwarding-01 (work in progress), March 2019. 441 [I-D.ietf-isis-segment-routing-extensions] 442 Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A., 443 Gredler, H., and B. Decraene, "IS-IS Extensions for 444 Segment Routing", draft-ietf-isis-segment-routing- 445 extensions-23 (work in progress), March 2019. 447 [I-D.ietf-ospf-segment-routing-extensions] 448 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., 449 Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 450 Extensions for Segment Routing", draft-ietf-ospf-segment- 451 routing-extensions-27 (work in progress), December 2018. 453 [I-D.li-ospf-ospfv3-srv6-extensions] 454 Li, Z., Hu, Z., Cheng, D., Talaulikar, K., and P. Psenak, 455 "OSPFv3 Extensions for SRv6", draft-li-ospf- 456 ospfv3-srv6-extensions-03 (work in progress), March 2019. 458 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 459 Requirement Levels", BCP 14, RFC 2119, 460 DOI 10.17487/RFC2119, March 1997, 461 . 463 [RFC7356] Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding 464 Scope Link State PDUs (LSPs)", RFC 7356, 465 DOI 10.17487/RFC7356, September 2014, 466 . 468 [RFC8400] Chen, H., Liu, A., Saad, T., Xu, F., and L. Huang, 469 "Extensions to RSVP-TE for Label Switched Path (LSP) 470 Egress Protection", RFC 8400, DOI 10.17487/RFC8400, June 471 2018, . 473 9.2. Informative References 475 [I-D.bashandy-rtgwg-segment-routing-ti-lfa] 476 Bashandy, A., Filsfils, C., Decraene, B., Litkowski, S., 477 Francois, P., daniel.voyer@bell.ca, d., Clad, F., and P. 478 Camarillo, "Topology Independent Fast Reroute using 479 Segment Routing", draft-bashandy-rtgwg-segment-routing-ti- 480 lfa-05 (work in progress), October 2018. 482 [I-D.hegde-spring-node-protection-for-sr-te-paths] 483 Hegde, S., Bowers, C., Litkowski, S., Xu, X., and F. Xu, 484 "Node Protection for SR-TE Paths", draft-hegde-spring- 485 node-protection-for-sr-te-paths-04 (work in progress), 486 October 2018. 488 [I-D.ietf-spring-segment-routing-policy] 489 Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d., 490 bogdanov@google.com, b., and P. Mattes, "Segment Routing 491 Policy Architecture", draft-ietf-spring-segment-routing- 492 policy-02 (work in progress), October 2018. 494 [I-D.sivabalan-pce-binding-label-sid] 495 Sivabalan, S., Filsfils, C., Tantsura, J., Hardwick, J., 496 Previdi, S., and C. Li, "Carrying Binding Label/Segment-ID 497 in PCE-based Networks.", draft-sivabalan-pce-binding- 498 label-sid-06 (work in progress), February 2019. 500 [RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching 501 (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic 502 Class" Field", RFC 5462, DOI 10.17487/RFC5462, February 503 2009, . 505 Authors' Addresses 506 Zhibo Hu 507 Huawei Technologies 508 Huawei Bld., No.156 Beiqing Rd. 509 Beijing 100095 510 China 512 Email: huzhibo@huawei.com 514 Huaimo Chen 515 Huawei Technologies 516 Boston, MA 517 USA 519 Email: Huaimo.chen@huawei.com 521 Huanan Chen 522 China Telecom 523 109, West Zhongshan Road, Tianhe District 524 Guangzhou 510000 525 China 527 Email: chenhn8.gd@chinatelecom.cn 529 Peng Wu 530 Huawei Technologies 531 Huawei Bld., No.156 Beiqing Rd. 532 Beijing 100095 533 China 535 Email: baggio.wupeng@huawei.com