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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 P. Wu 5 Expires: September 6, 2019 Huawei Technologies 6 March 5, 2019 8 SRv6 Path Egress Protection 9 draft-hu-rtgwg-srv6-egress-protection-00 11 Abstract 13 This document describes protocol extensions and procedures for 14 protecting the egress node of a Segment Routing for IPv6 (SRv6) path. 16 Requirements Language 18 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 19 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 20 document are to be interpreted as described in RFC 2119 [RFC2119]. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at https://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on September 6, 2019. 39 Copyright Notice 41 Copyright (c) 2019 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (https://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 2. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 2 58 3. SR Path Egress Protection . . . . . . . . . . . . . . . . . . 3 59 4. Extensions to IGP for Egress Protection . . . . . . . . . . . 5 60 4.1. Extensions to IS-IS . . . . . . . . . . . . . . . . . . . 5 61 4.2. Extensions to OSPF . . . . . . . . . . . . . . . . . . . 7 62 5. Behavior for SRv6 Mirror SID . . . . . . . . . . . . . . . . 9 63 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 64 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 65 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 66 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 67 9.1. Normative References . . . . . . . . . . . . . . . . . . 9 68 9.2. Informative References . . . . . . . . . . . . . . . . . 10 69 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 71 1. Introduction 73 Fast protection of a transit node of a Segment Routing (SR) path is 74 described in [I-D.bashandy-rtgwg-segment-routing-ti-lfa] and 75 [I-D.hu-spring-segment-routing-proxy-forwarding]. However, these 76 documents do not discuss the procedures for fast protection of the 77 egress node of a Segment Routing for IPv6 (SRv6) path. 79 This document fills that void and specifies protocol extensions and 80 procedures for fast protection of the egress node of an SRv6 path. 81 Egress node and egress as well as fast protection and protection will 82 be used exchangeably. 84 2. Terminologies 86 The following terminologies are used in this document. 88 SR: Segment Routing 90 SRv6: SR for IPv6 92 SRH: Segment Routing Header 94 SID: Segment Identifier 96 CE: Customer Edge 97 PE: Provider Edge 99 LFA: Loop-Free Alternate 101 TI-LFA: Topology Independent LFA 103 TE: Traffic Engineering 105 BFD: Bidirectional Forwarding Detection 107 VPN: Virtual Private Network 109 L3VPN: Layer 3 VPN 111 VRF: Virtual Routing and Forwarding 113 FIB: Forwarding Information Base 115 PLR: Point of Local Repair 117 BGP: Border Gateway Protocol 119 IGP: Interior Gateway Protocol 121 OSPF: Open Shortest Path First 123 IS-IS: Intermediate System to Intermediate System 125 3. SR Path Egress Protection 127 Figure 1 shows an example of protecting egress PE3 of a SR path, 128 which is from ingress PE1 to egress PE3. 130 Locator: A3:1::/64 131 ******* ******* VPN SID: A3:1::B100 132 [PE1]-----[P1]-----[PE3] 133 / | |& | \ PE3 Egress 134 / | |& | \ CEx Customer Edge 135 [CE1] | |& | [CE2] Px Non-Egress 136 \ | |& | / *** SR Path 137 \ | |& &&&&& | / &&& Backup Path 138 [PE2]-----[P2]-----[PE4] 139 Locator: A4:1::/64 140 VPN SID: A4:1::B100 141 Mirror SID: A4:1::3, protect A3:1::/64 143 Figure 1: Protecting SR Path Egress PE3 145 Node P1's pre-computed TI-LFA backup path for PE3 is from P1 to PE4 146 via P2. In normal operations, after receiving a packet with 147 destination PE3, P1 forwards the packet to PE3 according to its FIB. 148 When PE3 receives the packet, it sends the packet to CE2. 150 When PE3 fails, P1 detects the failure through BFD and forwards the 151 packet to PE4 via the backup path. When PE4 receives the packet, it 152 sends the packet to the same CE2. 154 In Figure 1, CE2 is dual home to PE3 and PE4. PE3 has a locator 155 A3:1::/64 and a VPN SID A3:1::B100. PE4 has a locator A4:1::/64 and 156 a VPN SID A4:1::B100. A mirror SID A4:1::3 is configured on PE4 for 157 protecting PE3 with locator A3:1::/64. 159 After the mirror SID is configured on a local PE (e.g., PE4), when 160 the local PE (e.g., BGP on the local PE) receives a prefix whose VPN 161 SID belongs to a remote PE (e.g., PE3) with the locator that is 162 protected by the local PE through mirror SID, the local PE (e.g., 163 PE4) creates a mapping from the remote PE's (e.g., PE3's) VPN SID and 164 the mirror SID to the local PE's (e.g., PE4's) VPN SID. The remote 165 PE is protected by the local PE. 167 For example, local PE4 has Prefix 1.1.1.1 with VPN SID:A4:1::B100, 168 when PE4 receives prefix 1.1.1.1 with remote PE3's VPN SID 169 A3:1::B100, it creates a mapping from remote PE3's VPN SID and the 170 mirror SID (i.e., "A3:1::B100, A4:1::3") to local PE4's VPN SID 171 (i.e., "A4:1::B100"). 173 Node P1's pre-computed TI-LFA backup path for destination PE3 having 174 locator A3:1::/64 is from P1 to PE4 having mirror SID A4:1::3. It is 175 installed as a T.Insert transit behavior. When P1 receives a packet 176 destined to PE3's VPN SID A3:1::B100, in normal operations, it 177 forwards the packet with source A1:1:: and destination PE3's VPN SID 178 A3:1::B100 according to the FIB using the destination PE3's VPN SID 179 A3:1::B100. 181 When PE3 fails, node P1 protects PE3 through sending the packet to 182 PE4 via the backup path pre-computed. P1 modifies the packet before 183 sending it to PE4. The modified packet has destination PE4 with 184 mirror SID A4:1::3, and SRH with PE3's VPN SID A3:1::B100 and the 185 mirror SID A4:1::3 (i.e., "A3:1::B100, A4:1::3; SL=1"). 187 When PE4 receives the packet, it forwards the packet to CE2 through 188 executing END.M instruction according to the local VPN SID (i.e., 189 A4:1::B100). 191 4. Extensions to IGP for Egress Protection 193 This section describes extensions to IS-IS and OSPF for advertising 194 the information about SRv6 path egress protection. 196 4.1. Extensions to IS-IS 198 A new sub-TLV, called IS-IS SRv6 End.m SID sub-TLV, is defined. It 199 is used in the SRv6 Locator TLV defined in 200 [I-D.bashandy-isis-srv6-extensions] to advertise SRv6 Segment 201 Identifiers (SIDs) with END.M function for SRv6 path egress 202 protection. The SRv6 End.m SIDs inherit the topology/algorithm from 203 the parent locator. The format of the sub-TLV is illustrated below. 205 0 1 2 3 206 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 1 207 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 208 | Type (TBD1) | Length | 209 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 210 | Flags | SRv6 Endpoint Function | 211 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 212 | SID (16 octets) | 213 : : 214 | | 215 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 216 | sub-TLVs | 217 : : 218 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 220 Figure 2: IS-IS SRv6 End.m SID sub-TLV 222 Type: TBD1 (suggested value 8) is to be assigned by IANA. 224 Length: variable. 226 Flags: 1 octet. No flags are currently defined. 228 SRv6 Endpoint Function: 2 octets. Add a new endpoint function 40 229 for end.m SID. 231 SID: 16 octets. This field contains the SRv6 end.m SID to be 232 advertised. 234 Two sub-TLVs are defined. One is the protected locators sub-TLV, and 235 the other is the protected SIDs sub-TLV. 237 A protected locators sub-TLV is used to carry the Locators to be 238 protected by the SRv6 mirror SID. It has the following format. 240 0 1 2 3 241 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 1 242 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 243 | Type (TBD2) | Length | 244 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 245 | Locator-Size | Locator (variable) ~ 246 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 247 : : 248 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 249 | Locator-Size | Locator (variable) ~ 250 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 252 Figure 3: IS-IS Protected Locators sub-TLV 254 Type: TBD2 (suggested value 1) is to be assigned by IANA. 256 Length: variable. 258 Locator-Size: 1 octet. Number of bits (1 - 128) in the Locator 259 field. 261 Locator: 1-16 octets. This field encodes an SRv6 Locator to be 262 protected by the SRv6 mirror SID. The Locator is encoded in the 263 minimal number of octets for the given number of bits. 265 A protected SIDs sub-TLV is used to carry the SIDs to be protected by 266 the SRv6 mirror SID. It has the following format. 268 0 1 2 3 269 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 1 270 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 271 | Type (TBD3) | Length | 272 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 273 | SID (16 octets) ~ 274 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 275 : : 276 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 277 | SID (16 octets) ~ 278 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 280 Figure 4: IS-IS Protected SIDs sub-TLV 282 Type: TBD3 (suggested value 2) is to be assigned by IANA. 284 Length: variable. 286 SID: 16 octets. This field encodes an SRv6 SID to be advertised. 288 4.2. Extensions to OSPF 290 Similarly, a new sub-TLV, called OSPF SRv6 End.m SID sub-TLV, is 291 defined. It is used to advertise SRv6 Segment Identifiers (SIDs) 292 with END.M function for SRv6 path egress protection. Its format is 293 illustrated below. 295 0 1 2 3 296 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 1 297 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 298 | Type (TBD4) | Length | 299 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 300 | Flags | SRv6 Endpoint Function | 301 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 302 | SID (16 octets) | 303 : : 304 | | 305 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 306 | sub-TLVs | 307 : : 308 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 310 Figure 5: OSPF SRv6 End.m SID sub-TLV 312 Type: TBD4 (suggested value 8) is to be assigned by IANA. 314 Length: variable. 316 Flags: 1 octet. No flags are currently defined. 318 SRv6 Endpoint Function: 2 octets. Add a new endpoint function 40 319 for end.m SID. 321 SID: 16 octets. This field contains the SRv6 end.m SID to be 322 advertised. 324 Two sub-TLVs are defined. One is the protected locators sub-TLV, and 325 the other is the protected SIDs sub-TLV. 327 A protected locators sub-TLV is used to carry the Locators to be 328 protected by the SRv6 mirror SID. It has the following format. 330 0 1 2 3 331 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 1 332 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 333 | Type (TBD5) | Length | 334 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 335 | Locator-Size | Locator (variable) ~ 336 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 337 : : 338 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 339 | Locator-Size | Locator (variable) ~ 340 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 342 Figure 6: OSPF Protected Locators sub-TLV 344 Type: TBD5 (suggested value 1) is to be assigned by IANA. 346 Length: variable. 348 Locator-Size: 1 octet. Number of bits (1 - 128) in the Locator 349 field. 351 Locator: 1-16 octets. This field encodes an SRv6 Locator to be 352 protected by the SRv6 mirror SID. The Locator is encoded in the 353 minimal number of octets for the given number of bits. 355 A protected SIDs sub-TLV is used to carry the SIDs to be protected by 356 the SRv6 mirror SID. It has the following format. 358 0 1 2 3 359 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 1 360 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 361 | Type (TBD6) | Length | 362 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 363 | SID (16 octets) ~ 364 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 365 : : 366 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 367 | SID (16 octets) ~ 368 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 370 Figure 7: OSPF Protected SIDs sub-TLV 372 Type: TBD6 (suggested value 2) is to be assigned by IANA. 374 Length: variable. 376 SID: 16 octets. This field encodes an SRv6 SID to be advertised. 378 5. Behavior for SRv6 Mirror SID 380 The "Endpoint with mirror protection to a vpn SID" function (End.M 381 for short) is a variant of the End function. The End.M is used for 382 SRv6 VPN egress protection. It is described below. 384 End.M: Mirror protection 385 When N receives a packet destined to S and S is a local End.M SID, 386 N does: 387 IF NH=SRH and SL = 1 ;; Ref1 388 SL-- 389 Map to a local VPN SID based on Mirror SID and SRH[SL] ;; Ref1 390 forward according to the local VPN SID ;; Ref2 391 ELSE 392 drop the packet 394 Figure 8: SRv6 Mirror SID Procedure 396 Ref1: An End.M SID must always be the penultimate SID. 398 Ref2: The rest forwarding behavior is the same as the corresponding 399 VPN sid. 401 6. Security Considerations 403 TBD 405 7. IANA Considerations 407 TBD 409 8. Acknowledgements 411 TBD 413 9. References 415 9.1. Normative References 417 [I-D.bashandy-isis-srv6-extensions] 418 Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and 419 Z. Hu, "IS-IS Extensions to Support Routing over IPv6 420 Dataplane", draft-bashandy-isis-srv6-extensions-04 (work 421 in progress), October 2018. 423 [I-D.hu-spring-segment-routing-proxy-forwarding] 424 Hu, Z., Chen, H., Yao, J., and C. Bowers, "Segment Routing 425 Proxy Forwarding", draft-hu-spring-segment-routing-proxy- 426 forwarding-01 (work in progress), March 2019. 428 [I-D.ietf-isis-segment-routing-extensions] 429 Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A., 430 Gredler, H., and B. Decraene, "IS-IS Extensions for 431 Segment Routing", draft-ietf-isis-segment-routing- 432 extensions-22 (work in progress), December 2018. 434 [I-D.ietf-ospf-segment-routing-extensions] 435 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., 436 Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 437 Extensions for Segment Routing", draft-ietf-ospf-segment- 438 routing-extensions-27 (work in progress), December 2018. 440 [I-D.li-ospf-ospfv3-srv6-extensions] 441 Li, Z., Hu, Z., Cheng, D., Talaulikar, K., and P. Psenak, 442 "OSPFv3 Extensions for SRv6", draft-li-ospf- 443 ospfv3-srv6-extensions-02 (work in progress), September 444 2018. 446 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 447 Requirement Levels", BCP 14, RFC 2119, 448 DOI 10.17487/RFC2119, March 1997, 449 . 451 [RFC7356] Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding 452 Scope Link State PDUs (LSPs)", RFC 7356, 453 DOI 10.17487/RFC7356, September 2014, 454 . 456 9.2. Informative References 458 [I-D.bashandy-rtgwg-segment-routing-ti-lfa] 459 Bashandy, A., Filsfils, C., Decraene, B., Litkowski, S., 460 Francois, P., daniel.voyer@bell.ca, d., Clad, F., and P. 461 Camarillo, "Topology Independent Fast Reroute using 462 Segment Routing", draft-bashandy-rtgwg-segment-routing-ti- 463 lfa-05 (work in progress), October 2018. 465 [I-D.hegde-spring-node-protection-for-sr-te-paths] 466 Hegde, S., Bowers, C., Litkowski, S., Xu, X., and F. Xu, 467 "Node Protection for SR-TE Paths", draft-hegde-spring- 468 node-protection-for-sr-te-paths-04 (work in progress), 469 October 2018. 471 [I-D.ietf-spring-segment-routing-policy] 472 Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d., 473 bogdanov@google.com, b., and P. Mattes, "Segment Routing 474 Policy Architecture", draft-ietf-spring-segment-routing- 475 policy-02 (work in progress), October 2018. 477 [I-D.sivabalan-pce-binding-label-sid] 478 Sivabalan, S., Filsfils, C., Tantsura, J., Hardwick, J., 479 Previdi, S., and C. Li, "Carrying Binding Label/Segment-ID 480 in PCE-based Networks.", draft-sivabalan-pce-binding- 481 label-sid-06 (work in progress), February 2019. 483 [RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching 484 (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic 485 Class" Field", RFC 5462, DOI 10.17487/RFC5462, February 486 2009, . 488 Authors' Addresses 490 Zhibo Hu 491 Huawei Technologies 492 Huawei Bld., No.156 Beiqing Rd. 493 Beijing 100095 494 China 496 Email: huzhibo@huawei.com 498 Huaimo Chen 499 Huawei Technologies 500 Boston, MA 501 USA 503 Email: Huaimo.chen@huawei.com 505 Peng Wu 506 Huawei Technologies 507 Huawei Bld., No.156 Beiqing Rd. 508 Beijing 100095 509 China 511 Email: baggio.wupeng@huawei.com