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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 Huawei 4 Intended status: Standards Track H. Chen 5 Expires: July 9, 2020 Futurewei 6 H. Chen 7 China Telecom 8 P. Wu 9 Huawei 10 M. Toy 11 Verizon 12 C. Cao 13 T. He 14 China Unicom 15 L. Liu 16 Fujitsu 17 X. Liu 18 Volta Networks 19 January 6, 2020 21 SRv6 Path Egress Protection 22 draft-hu-rtgwg-srv6-egress-protection-04 24 Abstract 26 This document describes protocol extensions for protecting the egress 27 node of a Segment Routing for IPv6 (SRv6) path or tunnel. 29 Requirements Language 31 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 32 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 33 document are to be interpreted as described in RFC 2119 [RFC2119]. 35 Status of This Memo 37 This Internet-Draft is submitted in full conformance with the 38 provisions of BCP 78 and BCP 79. 40 Internet-Drafts are working documents of the Internet Engineering 41 Task Force (IETF). Note that other groups may also distribute 42 working documents as Internet-Drafts. The list of current Internet- 43 Drafts is at https://datatracker.ietf.org/drafts/current/. 45 Internet-Drafts are draft documents valid for a maximum of six months 46 and may be updated, replaced, or obsoleted by other documents at any 47 time. It is inappropriate to use Internet-Drafts as reference 48 material or to cite them other than as "work in progress." 49 This Internet-Draft will expire on July 9, 2020. 51 Copyright Notice 53 Copyright (c) 2020 IETF Trust and the persons identified as the 54 document authors. All rights reserved. 56 This document is subject to BCP 78 and the IETF Trust's Legal 57 Provisions Relating to IETF Documents 58 (https://trustee.ietf.org/license-info) in effect on the date of 59 publication of this document. Please review these documents 60 carefully, as they describe your rights and restrictions with respect 61 to this document. Code Components extracted from this document must 62 include Simplified BSD License text as described in Section 4.e of 63 the Trust Legal Provisions and are provided without warranty as 64 described in the Simplified BSD License. 66 Table of Contents 68 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 69 2. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 3 70 3. SR Path Egress Protection . . . . . . . . . . . . . . . . . . 4 71 4. Extensions to IGP for Egress Protection . . . . . . . . . . . 5 72 4.1. Extensions to IS-IS . . . . . . . . . . . . . . . . . . . 5 73 4.2. Extensions to OSPF . . . . . . . . . . . . . . . . . . . 7 74 5. Behavior for SRv6 Mirror SID . . . . . . . . . . . . . . . . 9 75 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10 76 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 77 7.1. IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . . 10 78 7.2. OSPFv3 . . . . . . . . . . . . . . . . . . . . . . . . . 11 79 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11 80 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 81 9.1. Normative References . . . . . . . . . . . . . . . . . . 11 82 9.2. Informative References . . . . . . . . . . . . . . . . . 12 83 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 85 1. Introduction 87 The fast protection of a transit node of a Segment Routing (SR) path 88 or tunnel is described in [I-D.ietf-rtgwg-segment-routing-ti-lfa] and 89 [I-D.hu-spring-segment-routing-proxy-forwarding]. [RFC8400] 90 specifies the fast protection of egress node(s) of an MPLS TE LSP 91 tunnel including P2P TE LSP tunnel and P2MP TE LSP tunnel in details. 92 However, these documents do not discuss the fast protection of the 93 egress node of a Segment Routing for IPv6 (SRv6) path or tunnel. 95 This document fills that void and presents protocol extensions for 96 the fast protection of the egress node of an SRv6 path or tunnel. 98 Egress node and egress, fast protection and protection as well as 99 SRv6 path and SRv6 tunnel will be used exchangeably below. 101 2. Terminologies 103 The following terminologies are used in this document. 105 SR: Segment Routing 107 SRv6: SR for IPv6 109 SRH: Segment Routing Header 111 SID: Segment Identifier 113 LSP: Label Switched Path 115 TE: Traffic Engineering 117 P2MP: Point-to-MultiPoint 119 P2P: Point-to-Point 121 CE: Customer Edge 123 PE: Provider Edge 125 LFA: Loop-Free Alternate 127 TI-LFA: Topology Independent LFA 129 BFD: Bidirectional Forwarding Detection 131 VPN: Virtual Private Network 133 L3VPN: Layer 3 VPN 135 VRF: Virtual Routing and Forwarding 137 FIB: Forwarding Information Base 139 PLR: Point of Local Repair 141 BGP: Border Gateway Protocol 143 IGP: Interior Gateway Protocol 145 OSPF: Open Shortest Path First 146 IS-IS: Intermediate System to Intermediate System 148 3. SR Path Egress Protection 150 Figure 1 shows an example of protecting egress PE3 of a SR path, 151 which is from ingress PE1 to egress PE3. 153 Locator: A3:1::/64 154 ******* ******* VPN SID: A3:1::B100 155 [PE1]-----[P1]-----[PE3] 156 / | |& | \ PE3 Egress 157 / | |& | \ CEx Customer Edge 158 [CE1] | |& | [CE2] Px Non-Provider Edge 159 \ | |& | / *** SR Path 160 \ | |& &&&&& | / &&& Backup Path 161 [PE2]-----[P2]-----[PE4] 162 Locator: A4:1::/64 163 VPN SID: A4:1::B100 164 Mirror SID: A4:1::3, protect A3:1::/64 166 Figure 1: Protecting SR Path Egress PE3 168 Node P1's pre-computed TI-LFA backup path for PE3 is from P1 to PE4 169 via P2. In normal operations, after receiving a packet with 170 destination PE3, P1 forwards the packet to PE3 according to its FIB. 171 When PE3 receives the packet, it sends the packet to CE2. 173 When PE3 fails, P1 detects the failure through BFD and forwards the 174 packet to PE4 via the backup path. When PE4 receives the packet, it 175 sends the packet to the same CE2. 177 In Figure 1, CE2 is dual home to PE3 and PE4. PE3 has a locator 178 A3:1::/64 and a VPN SID A3:1::B100. PE4 has a locator A4:1::/64 and 179 a VPN SID A4:1::B100. A mirror SID A4:1::3 is configured on PE4 for 180 protecting PE3 with locator A3:1::/64. 182 After the mirror SID is configured on a local PE (e.g., PE4), when 183 the local PE (e.g., BGP on the local PE) receives a prefix whose VPN 184 SID belongs to a remote PE (e.g., PE3) with the locator that is 185 protected by the local PE through mirror SID, the local PE (e.g., 186 PE4) creates a mapping from the remote PE's (e.g., PE3's) VPN SID and 187 the mirror SID to the local PE's (e.g., PE4's) VPN SID. The remote 188 PE is protected by the local PE. 190 For example, local PE4 has Prefix 1.1.1.1 with VPN SID:A4:1::B100, 191 when PE4 receives prefix 1.1.1.1 with remote PE3's VPN SID 192 A3:1::B100, it creates a mapping from remote PE3's VPN SID and the 193 mirror SID (i.e., "A3:1::B100, A4:1::3") to local PE4's VPN SID 194 (i.e., "A4:1::B100"). 196 Node P1's pre-computed TI-LFA backup path for destination PE3 having 197 locator A3:1::/64 is from P1 to PE4 having mirror SID A4:1::3. When 198 P1 receives a packet destined to PE3's VPN SID A3:1::B100, in normal 199 operations, it forwards the packet with source A1:1:: and destination 200 PE3's VPN SID A3:1::B100 according to the FIB using the destination 201 PE3's VPN SID A3:1::B100. 203 When PE3 fails, node P1 protects PE3 through sending the packet to 204 PE4 via the backup path pre-computed. P1 modifies the packet before 205 sending it to PE4. The modified packet has destination PE4 with 206 mirror SID A4:1::3, and SRH with PE3's VPN SID A3:1::B100 and the 207 mirror SID A4:1::3 (i.e., "A3:1::B100, A4:1::3; SL=1"). 209 When PE4 receives the packet, it forwards the packet to CE2 through 210 executing END.M instruction according to the local VPN SID (i.e., 211 A4:1::B100). 213 4. Extensions to IGP for Egress Protection 215 This section describes extensions to IS-IS and OSPF for advertising 216 the information about SRv6 path egress protection. 218 4.1. Extensions to IS-IS 220 A new sub-TLV, called IS-IS SRv6 End.M SID sub-TLV, is defined. It 221 is used in the SRv6 Locator TLV defined in 222 [I-D.ietf-lsr-isis-srv6-extensions] to advertise SRv6 Segment 223 Identifiers (SIDs) with END.M function for SRv6 path egress 224 protection. The SRv6 End.M SIDs inherit the topology/algorithm from 225 the parent locator. The format of the sub-TLV is illustrated below. 227 0 1 2 3 228 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 1 229 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 230 | Type (TBD1) | Length | 231 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 232 | Flags | SRv6 Endpoint Function | 233 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 234 | SID (16 octets) | 235 : : 236 | | 237 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 238 | sub-TLVs | 239 : : 240 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 242 Figure 2: IS-IS SRv6 End.M SID sub-TLV 244 Type: TBD1 (suggested value 8) is to be assigned by IANA. 246 Length: variable. 248 Flags: 1 octet. No flags are currently defined. 250 SRv6 Endpoint Function: 2 octets. Add a new endpoint function 40 251 for End.M SID. 253 SID: 16 octets. This field contains the SRv6 End.M SID to be 254 advertised. 256 Two sub-TLVs are defined. One is the protected locators sub-TLV, and 257 the other is the protected SIDs sub-TLV. 259 A protected locators sub-TLV is used to carry the Locators to be 260 protected by the SRv6 mirror SID. It has the following format. 262 0 1 2 3 263 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 1 264 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 265 | Type (TBD2) | Length | 266 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 267 | Locator-Size | Locator (variable) ~ 268 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 269 : : 270 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 271 | Locator-Size | Locator (variable) ~ 272 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 274 Figure 3: IS-IS Protected Locators sub-TLV 276 Type: TBD2 (suggested value 1) is to be assigned by IANA. 278 Length: variable. 280 Locator-Size: 1 octet. Number of bits (1 - 128) in the Locator 281 field. 283 Locator: 1-16 octets. This field encodes an SRv6 Locator to be 284 protected by the SRv6 mirror SID. The Locator is encoded in the 285 minimal number of octets for the given number of bits. 287 A protected SIDs sub-TLV is used to carry the SIDs to be protected by 288 the SRv6 mirror SID. It has the following format. 290 0 1 2 3 291 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 1 292 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 293 | Type (TBD3) | Length | 294 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 295 | SID (16 octets) ~ 296 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 297 : : 298 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 299 | SID (16 octets) ~ 300 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 302 Figure 4: IS-IS Protected SIDs sub-TLV 304 Type: TBD3 (suggested value 2) is to be assigned by IANA. 306 Length: variable. 308 SID: 16 octets. This field encodes an SRv6 SID to be advertised. 310 4.2. Extensions to OSPF 312 Similarly, a new sub-TLV, called OSPF SRv6 End.M SID sub-TLV, is 313 defined. It is used to advertise SRv6 Segment Identifiers (SIDs) 314 with END.M function for SRv6 path egress protection. Its format is 315 illustrated below. 317 0 1 2 3 318 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 1 319 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 320 | Type (TBD4) | Length | 321 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 322 | Flags | SRv6 Endpoint Function | 323 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 324 | SID (16 octets) | 325 : : 326 | | 327 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 328 | sub-TLVs | 329 : : 330 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 332 Figure 5: OSPF SRv6 End.M SID sub-TLV 334 Type: TBD4 (suggested value 8) is to be assigned by IANA. 336 Length: variable. 338 Flags: 1 octet. No flags are currently defined. 340 SRv6 Endpoint Function: 2 octets. Add a new endpoint function 40 341 for End.M SID. 343 SID: 16 octets. This field contains the SRv6 End.M SID to be 344 advertised. 346 Two sub-TLVs are defined. One is the protected locators sub-TLV, and 347 the other is the protected SIDs sub-TLV. 349 A protected locators sub-TLV is used to carry the Locators to be 350 protected by the SRv6 mirror SID. It has the following format. 352 0 1 2 3 353 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 1 354 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 355 | Type (TBD5) | Length | 356 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 357 | Locator-Size | Locator (variable) ~ 358 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 359 : : 360 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 361 | Locator-Size | Locator (variable) ~ 362 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 364 Figure 6: OSPF Protected Locators sub-TLV 366 Type: TBD5 (suggested value 1) is to be assigned by IANA. 368 Length: variable. 370 Locator-Size: 1 octet. Number of bits (1 - 128) in the Locator 371 field. 373 Locator: 1-16 octets. This field encodes an SRv6 Locator to be 374 protected by the SRv6 mirror SID. The Locator is encoded in the 375 minimal number of octets for the given number of bits. 377 A protected SIDs sub-TLV is used to carry the SIDs to be protected by 378 the SRv6 mirror SID. It has the following format. 380 0 1 2 3 381 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 1 382 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 383 | Type (TBD6) | Length | 384 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 385 | SID (16 octets) ~ 386 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 387 : : 388 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 389 | SID (16 octets) ~ 390 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 392 Figure 7: OSPF Protected SIDs sub-TLV 394 Type: TBD6 (suggested value 2) is to be assigned by IANA. 396 Length: variable. 398 SID: 16 octets. This field encodes an SRv6 SID to be advertised. 400 5. Behavior for SRv6 Mirror SID 402 The "Endpoint with mirror protection to a VPN SID" function (End.M 403 for short) is a variant of the End function. The End.M is used for 404 SRv6 VPN egress protection. It is described below. 406 End.M: Mirror protection 407 When N receives a packet destined to S and S is a local End.M SID, 408 N does: 409 IF NH=SRH and SL = 1 ;; Ref1 410 SL-- 411 Map to a local VPN SID based on Mirror SID and SRH[SL] ;; Ref1 412 forward according to the local VPN SID ;; Ref2 413 ELSE 414 drop the packet 416 Figure 8: SRv6 Mirror SID Procedure 418 Ref1: An End.M SID must always be the penultimate SID. 420 Ref2: The rest forwarding behavior is the same as the corresponding 421 VPN sid. 423 6. Security Considerations 425 The extensions to OSPF and IS-IS described in this document should 426 not cause extra security issues. 428 7. IANA Considerations 430 7.1. IS-IS 432 Under "Sub-TLVs for TLVs 27, 135, 235, 236 and 237 registry" 433 [I-D.ietf-lsr-isis-srv6-extensions], IANA is requested to add the 434 following new Sub-TLV: 436 +==============+========================+===============+ 437 | Sub-TLV Type | Sub-TLV Name | Reference | 438 +==============+========================+===============+ 439 | 8 | SRv6 End.M SID Sub-TLV | This document | 440 +--------------+------------------------+---------------+ 442 IANA is requested to create and maintain a new registry for sub-sub- 443 TLVs of the SRv6 End.M SID Sub-TLV. The suggested registry name is 445 o Sub-Sub-TLVs for SRv6 End.M SID Sub-TLV 447 Initial values for the registry are given below. The future 448 assignments are to be made through IETF Review [RFC5226]. 450 Value Sub-Sub-TLV Name Definition 451 ----- ----------------------- ------------- 452 0 Reserved 453 1 Protected Locators Sub-Sub-TLV This Document 454 2 Protected SIDs Sub-Sub-TLV 455 3-255 Unassigned 457 7.2. OSPFv3 459 Under registry "OSPFv3 Locator LSA Sub-TLVs" 460 [I-D.li-ospf-ospfv3-srv6-extensions], IANA is requested to assign the 461 following new Sub-TLV: 463 +==============+========================+===============+ 464 | Sub-TLV Type | Sub-TLV Name | Reference | 465 +==============+========================+===============+ 466 | 8 | SRv6 End.M SID Sub-TLV | This document | 467 +--------------+------------------------+---------------+ 469 IANA is requested to create and maintain a new registry for sub-sub- 470 TLVs of the SRv6 End.M SID Sub-TLV. The suggested registry name is 472 o Sub-Sub-TLVs for SRv6 End.M SID Sub-TLV 474 Initial values for the registry are given below. The future 475 assignments are to be made through IETF Review [RFC5226]. 477 Value Sub-Sub-TLV Name Definition 478 ----- ----------------------- ------------- 479 0 Reserved 480 1 Protected Locators Sub-Sub-TLV This Document 481 2 Protected SIDs Sub-Sub-TLV 482 3-65535 Unassigned 484 8. Acknowledgements 486 The authors would like to thank Peter Psenak, Zhenqiang Li, Bruno 487 Decraene and Jeff Tantsura for their comments to this work. 489 9. References 491 9.1. Normative References 493 [I-D.ietf-isis-segment-routing-extensions] 494 Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A., 495 Gredler, H., and B. Decraene, "IS-IS Extensions for 496 Segment Routing", draft-ietf-isis-segment-routing- 497 extensions-25 (work in progress), May 2019. 499 [I-D.ietf-lsr-isis-srv6-extensions] 500 Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and 501 Z. Hu, "IS-IS Extension to Support Segment Routing over 502 IPv6 Dataplane", draft-ietf-lsr-isis-srv6-extensions-03 503 (work in progress), October 2019. 505 [I-D.ietf-ospf-segment-routing-extensions] 506 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., 507 Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 508 Extensions for Segment Routing", draft-ietf-ospf-segment- 509 routing-extensions-27 (work in progress), December 2018. 511 [I-D.li-ospf-ospfv3-srv6-extensions] 512 Li, Z., Hu, Z., Cheng, D., Talaulikar, K., and P. Psenak, 513 "OSPFv3 Extensions for SRv6", draft-li-ospf- 514 ospfv3-srv6-extensions-07 (work in progress), November 515 2019. 517 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 518 Requirement Levels", BCP 14, RFC 2119, 519 DOI 10.17487/RFC2119, March 1997, 520 . 522 [RFC7356] Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding 523 Scope Link State PDUs (LSPs)", RFC 7356, 524 DOI 10.17487/RFC7356, September 2014, 525 . 527 [RFC8400] Chen, H., Liu, A., Saad, T., Xu, F., and L. Huang, 528 "Extensions to RSVP-TE for Label Switched Path (LSP) 529 Egress Protection", RFC 8400, DOI 10.17487/RFC8400, June 530 2018, . 532 9.2. Informative References 534 [I-D.hegde-spring-node-protection-for-sr-te-paths] 535 Hegde, S., Bowers, C., Litkowski, S., Xu, X., and F. Xu, 536 "Node Protection for SR-TE Paths", draft-hegde-spring- 537 node-protection-for-sr-te-paths-05 (work in progress), 538 July 2019. 540 [I-D.hu-spring-segment-routing-proxy-forwarding] 541 Hu, Z., Chen, H., Yao, J., Bowers, C., and Y. Zhu, "SR-TE 542 Path Midpoint Protection", draft-hu-spring-segment- 543 routing-proxy-forwarding-06 (work in progress), October 544 2019. 546 [I-D.ietf-rtgwg-segment-routing-ti-lfa] 547 Litkowski, S., Bashandy, A., Filsfils, C., Decraene, B., 548 Francois, P., Voyer, D., Clad, F., and P. Camarillo, 549 "Topology Independent Fast Reroute using Segment Routing", 550 draft-ietf-rtgwg-segment-routing-ti-lfa-01 (work in 551 progress), March 2019. 553 [I-D.ietf-spring-segment-routing-policy] 554 Filsfils, C., Sivabalan, S., Voyer, D., Bogdanov, A., and 555 P. Mattes, "Segment Routing Policy Architecture", draft- 556 ietf-spring-segment-routing-policy-06 (work in progress), 557 December 2019. 559 [I-D.sivabalan-pce-binding-label-sid] 560 Sivabalan, S., Filsfils, C., Tantsura, J., Hardwick, J., 561 Previdi, S., and C. Li, "Carrying Binding Label/Segment-ID 562 in PCE-based Networks.", draft-sivabalan-pce-binding- 563 label-sid-07 (work in progress), July 2019. 565 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 566 IANA Considerations Section in RFCs", RFC 5226, 567 DOI 10.17487/RFC5226, May 2008, 568 . 570 [RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching 571 (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic 572 Class" Field", RFC 5462, DOI 10.17487/RFC5462, February 573 2009, . 575 Authors' Addresses 577 Zhibo Hu 578 Huawei 579 Huawei Bld., No.156 Beiqing Rd. 580 Beijing 100095 581 China 583 Email: huzhibo@huawei.com 585 Huaimo Chen 586 Futurewei 587 Boston, MA 588 USA 590 Email: Huaimo.chen@futurewei.com 591 Huanan Chen 592 China Telecom 593 109, West Zhongshan Road, Tianhe District 594 Guangzhou 510000 595 China 597 Email: chenhn8.gd@chinatelecom.cn 599 Peng Wu 600 Huawei 601 Huawei Bld., No.156 Beiqing Rd. 602 Beijing 100095 603 China 605 Email: baggio.wupeng@huawei.com 607 Mehmet Toy 608 Verizon 609 USA 611 Email: mehmet.toy@verizon.com 613 Chang Cao 614 China Unicom 615 Beijing China 617 Email: caoc15@chinaunicom.cn 619 Tao He 620 China Unicom 621 Beijing China 623 Email: het21@chinaunicom.cn 625 Lei Liu 626 Fujitsu 627 USA 629 Email: liulei.kddi@gmail.com 630 Xufeng Liu 631 Volta Networks 632 McLean, VA 633 USA 635 Email: xufeng.liu.ietf@gmail.com