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'I-D.mirsky-bfd-mpls-demand') == Outdated reference: A later version (-14) exists of draft-ietf-mpls-static-yang-05 == Outdated reference: A later version (-03) exists of draft-ietf-spring-mpls-anycast-segments-02 Summary: 2 errors (**), 0 flaws (~~), 6 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 SPRING Working Group G. Mirsky 3 Internet-Draft ZTE Corp. 4 Intended status: Standards Track J. Tantsura 5 Expires: February 24, 2019 Nuage Networks 6 I. Varlashkin 7 Google 8 M. Chen 9 Huawei 10 August 23, 2018 12 Bidirectional Forwarding Detection (BFD) in Segment Routing Networks 13 Using MPLS Dataplane 14 draft-mirsky-spring-bfd-06 16 Abstract 18 Segment Routing (SR) architecture leverages the paradigm of source 19 routing. It can be realized in the Multiprotocol Label Switching 20 (MPLS) network without any change to the data plane. A segment is 21 encoded as an MPLS label, and an ordered list of segments is encoded 22 as a stack of labels. Bidirectional Forwarding Detection (BFD) is 23 expected to monitor any existing path between systems. This document 24 defines how to use Label Switched Path Ping to bootstrap a BFD 25 session, control path in reverse direction of the SR-MPLS tunnel and 26 applicability of BFD Demand mode in the SR-MPLS domain. 28 Status of This Memo 30 This Internet-Draft is submitted in full conformance with the 31 provisions of BCP 78 and BCP 79. 33 Internet-Drafts are working documents of the Internet Engineering 34 Task Force (IETF). Note that other groups may also distribute 35 working documents as Internet-Drafts. The list of current Internet- 36 Drafts is at https://datatracker.ietf.org/drafts/current/. 38 Internet-Drafts are draft documents valid for a maximum of six months 39 and may be updated, replaced, or obsoleted by other documents at any 40 time. It is inappropriate to use Internet-Drafts as reference 41 material or to cite them other than as "work in progress." 43 This Internet-Draft will expire on February 24, 2019. 45 Copyright Notice 47 Copyright (c) 2018 IETF Trust and the persons identified as the 48 document authors. All rights reserved. 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (https://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. Code Components extracted from this document must 56 include Simplified BSD License text as described in Section 4.e of 57 the Trust Legal Provisions and are provided without warranty as 58 described in the Simplified BSD License. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 63 1.1. Conventions . . . . . . . . . . . . . . . . . . . . . . . 3 64 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3 65 1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3 66 2. Bootstrapping BFD Session over Segment Routed Tunnel with 67 MPLS Data Plane . . . . . . . . . . . . . . . . . . . . . . . 3 68 3. Use BFD Reverse Path TLV over Segment Routed MPLS Tunnel . . 5 69 4. Use Non-FEC Path TLV . . . . . . . . . . . . . . . . . . . . 5 70 5. BFD Reverse Path TLV over Segment Routed MPLS Tunnel with 71 Dynamic Control Plane . . . . . . . . . . . . . . . . . . . . 7 72 6. Applicability of BFD Demand Mode in SR-MPLS Domain . . . . . 7 73 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 74 7.1. Non-FEC Path TLV . . . . . . . . . . . . . . . . . . . . 7 75 7.2. Return Code . . . . . . . . . . . . . . . . . . . . . . . 8 76 8. Security Considerations . . . . . . . . . . . . . . . . . . . 9 77 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 78 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 79 10.1. Normative References . . . . . . . . . . . . . . . . . . 9 80 10.2. Informative References . . . . . . . . . . . . . . . . . 11 81 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 83 1. Introduction 85 [RFC5880], [RFC5881], and [RFC5883] defined the operation of 86 Bidirectional Forwarding Detection (BFD) protocol between the two 87 systems over IP networks. [RFC5884] and [RFC7726] set rules for 88 using BFD Asynchronous mode over point-to-point (p2p) Multiprotocol 89 Label Switching (MPLS) Label Switched Path (LSP). These latter 90 standards implicitly assume that the egress BFD peer, which is the 91 egress Label Edge Router (LER), will use the shortest path route 92 regardless of the path the ingress LER uses to send BFD Control 93 packets towards it. 95 This document defines the use of LSP Ping for Segment Routing 96 networks over MPLS data plane [RFC8287] to bootstrap and control path 97 of a BFD session from the egress to ingress LER using Segment Routing 98 tunnel with MPLS data plane (SR-MPLS). 100 1.1. Conventions 102 1.1.1. Terminology 104 BFD: Bidirectional Forwarding Detection 106 FEC: Forwarding Equivalence Class 108 MPLS: Multiprotocol Label Switching 110 SR-MPLS Segment Routing with MPLS data plane 112 LSP: Label Switched Path 114 LSR Label Switching Router 116 LER Label Edge Router 118 p2p Point-to-point 120 SID Segment Identifier 122 SR Segment Routing 124 1.1.2. Requirements Language 126 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 127 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 128 "OPTIONAL" in this document are to be interpreted as described in BCP 129 14 [RFC2119] [RFC8174] when, and only when, they appear in all 130 capitals, as shown here. 132 2. Bootstrapping BFD Session over Segment Routed Tunnel with MPLS Data 133 Plane 135 Use of an LSP Ping to bootstrap BFD over MPLS LSP is required, as 136 documented in [RFC5884], to establish an association between a fault 137 detection message, i.e., BFD Control message, and the Forwarding 138 Equivalency Class (FEC) of a single label stack LSP in case of 139 Penultimate Hop Popping or when the egress Label Switching Router 140 (LSR) distributes the Explicit NULL label to the penultimate hop 141 router. The Explicit NULL label is not advertised as a Segment 142 Identifier (SID) by an SR node but, as demonstrated in section 3.1 143 [I-D.ietf-spring-segment-routing-mpls] if the operation at the 144 penultimate hop is NEXT; then the egress SR node will receive an IP 145 encapsulated packet. Thus the conclusion is that LSP Ping MUST be 146 used to bootstrap a BFD session in SR-MPLS domain. 148 As demonstrated in [RFC8287], the introduction of Segment Routing 149 network domains with an MPLS data plane requires three new sub-TLVs 150 that MAY be used with Target FEC TLV. Section 6.1 addresses use of 151 the new sub-TLVs in Target FEC TLV in LSP ping and LSP traceroute. 152 For the case of LSP ping, the [RFC8287] states that: 154 The initiator, i.e., ingress LSR, MUST include FEC(s) 155 corresponding to the destination segment. 157 The initiator MAY include FECs corresponding to some or all of 158 segments imposed in the label stack by the ingress LSR to 159 communicate the segments traversed. 161 It has been noted in [RFC5884] that a BFD session monitors for 162 defects particular tuple. [RFC7726] clarified how to 163 establish and operate multiple BFD sessions for the same tuple. Because only ingress edge router is aware of the SR- 165 based explicit route, the egress edge router can associate the LSP 166 ping with BFD Discriminator TLV with only one of the FECs it 167 advertised for the particular segment. Thus this document clarifies 168 that: 170 When LSP Ping is used to bootstraping a BFD session for SR-MPLS 171 tunnel the FEC corresponding to the segment to be associated with 172 the BFD session MUST be as the very last sub-TLV in the Target FEC 173 TLV. 175 If the target segment is an anycast prefix segment 176 ([I-D.ietf-spring-mpls-anycast-segments]) the corresponding Anycast 177 SID MUST be included in the Target TLV as the very last sub-TLV. 178 Also, for BFD control packet the ingress SR node MUST use precisely 179 the same label stack encapsulation, especially Entropy Label 180 ([RFC6790]), as for the LSP ping with the BFD Discriminator TLV that 181 bootstrapped the BFD session. Other operational aspects of using BFD 182 to monitor the continuity of the path to the particular Anycast SID, 183 advertised by a group of SR-MPLS capable nodes, will be considered in 184 the future versions of the document. 186 Encapsulation of a BFD Control packet in Segment Routing network with 187 MPLS data plane MUST follow Section 7 [RFC5884] when the IP/UDP 188 header used and MUST follow Section 3.4 [RFC6428] without IP/UDP 189 header being used. 191 3. Use BFD Reverse Path TLV over Segment Routed MPLS Tunnel 193 For BFD over MPLS LSP case, per [RFC5884], egress LER MAY send BFD 194 control packet to the ingress LER either over IP network or an MPLS 195 LSP. Similarly, for the case of BFD over p2p SR-MPLS tunnel, the 196 egress LER MAY route BFD control packet over the IP network, as 197 described in [RFC5883], or transmit over a segment tunnel, as 198 described in Section 7 [RFC5884]. In some cases, there may be a need 199 to direct egress BFD peer to use specific path for the reverse 200 direction of the BFD session by using the BFD Reverse Path TLV and 201 following all procedures as defined in [I-D.ietf-mpls-bfd-directed]. 203 4. Use Non-FEC Path TLV 205 For the case of MPLS data plane, Segment Routing Architecture 206 [RFC8402] explains that "a segment is encoded as an MPLS label. An 207 ordered list of segments is encoded as a stack of labels." YANG Data 208 Model for MPLS Static LSPs [I-D.ietf-mpls-static-yang] models 209 outgoing MPLS labels to be imposed as leaf-list [RFC6020], i.e., as 210 array of rt-types:mpls-label [RFC8294]. 212 This document defines new optional Non-FEC Path TLV. The format of 213 the Non-FEC Path TLV is presented in Figure 1 215 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 | Non-FEC Path TLV Type | Length | 219 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 220 | | 221 ~ Non-FEC Path ~ 222 | | 223 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 225 Figure 1: Non-FEC Path TLV Format 227 Non-FEC Path TLV Type is two octets in length and has a value of TBD1 228 (to be assigned by IANA as requested in Section 7.1). 230 Length field is two octets long and defines the length in octets of 231 the Non-FEC Path field. 233 Non-FEC Path field contains a sub-TLV. Any Non-FEC Path sub-TLV 234 (defined in this document or to be defined in the future) for Non-FEC 235 Path TLV type MAY be used in this field. None or one sub-TLV MAY be 236 included in the Non-FEC Path TLV. If no sub-TLV has been found in 237 the Non-FEC Path TLV, the egress BFD peer MUST revert to using the 238 reverse path selected based on its local policy. If there is more 239 than one sub-TLV, then the Return Code in echo reply MUST be set to 240 value TBD3 "Too Many TLVs Detected" (to be assigned by IANA as 241 requested in Table 4). 243 Non-FEC Path TLV MAY be used to specify the reverse path of the BFD 244 session identified in the BFD Discriminator TLV. If the Non-FEC Path 245 TLV is present in the echo request message the BFD Discriminator TLV 246 MUST be present as well. If the BFD Discriminator TLV is absent when 247 the Non-FEC Path TLV is included, then it MUST be treated as 248 malformed Echo Request, as described in [RFC8029]. 250 This document defines Static Routing MPLS Tunnel sub-TLV that MAY be 251 used with the Non-FEC Path TLV. The format of the sub-TLV is 252 presented in Figure 2. 254 0 1 2 3 255 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 1 256 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 257 | SR MPLS Tunnel sub-TLV Type | Length | 258 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 259 | Label Entry 1 (Top Label) | 260 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 261 | Label Entry 2 | 262 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 263 ~ ~ 264 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 265 | Label Entry N (Bottom Label) | 266 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 268 Figure 2: Segment Routing MPLS Tunnel sub-TLV 270 The Segment Routing MPLS Tunnel sub-TLV Type is two octets in length, 271 and has a value of TBD2 (to be assigned by IANA as requested in 272 Section 7.1). 274 The egress LSR MUST use the Value field as label stack for BFD 275 control packets for the BFD session identified by the source IP 276 address of the MPLS LSP Ping packet and the value in the BFD 277 Discriminator TLV. Label Entries MUST be in network order. 279 5. BFD Reverse Path TLV over Segment Routed MPLS Tunnel with Dynamic 280 Control Plane 282 When Segment Routed domain with MPLS data plane uses distributed 283 tunnel computation BFD Reverse Path TLV MAY use Target FEC sub-TLVs 284 defined in [RFC8287]. 286 6. Applicability of BFD Demand Mode in SR-MPLS Domain 288 [I-D.mirsky-bfd-mpls-demand] defines how Demand mode of BFD, 289 specified in sections 6.6 and 6.18.4 of [RFC5880], can be used to 290 monitor uni-directional MPLS LSP. Similar procedures can be 291 following in SR-MPLS to monitor uni-directional SR tunnels: 293 o ingress SR node bootstraps BFD session over SR-MPLS in Async BFD 294 mode; 296 o once BFD session is Up, the ingress node switches the egress BFD 297 node into the Demand mode by setting D field in BFD Control packet 298 it transmits; 300 o if the egress BFD node detects the failure of the BFD session, it 301 sends its BFD control packet to the ingress over the IP network 302 with Poll sequence; 304 o if the ingress node receives a BFD control packet from the remote 305 node in a Demand mode with Poll sequence and Diag field indicating 306 the failure, the ingress transmits BFD control packet with Final 307 over IP and switches the BFD over SR-MPLS back into Async mode, 308 sending BFD Control packets one per second. 310 7. IANA Considerations 312 7.1. Non-FEC Path TLV 314 IANA is requested to assign new TLV type from the from Standards 315 Action range of the registry "Multiprotocol Label Switching 316 Architecture (MPLS) Label Switched Paths (LSPs) Ping Parameters - 317 TLVs" as defined in Table 1. 319 +-------+------------------+---------------+ 320 | Value | TLV Name | Reference | 321 +-------+------------------+---------------+ 322 | TBD1 | Non-FEC Path TLV | This document | 323 +-------+------------------+---------------+ 325 Table 1: New Non-FEC Path TLV 327 IANA is requested to create new Non-FEC Path sub-TLV registry for the 328 Non-FEC Path TLV as described in Table 2. 330 +-------------+---------------+-------------------------------------+ 331 | Range | Registration | Note | 332 | | Procedures | | 333 +-------------+---------------+-------------------------------------+ 334 | 0-16383 | Standards | This range is for mandatory TLVs or | 335 | | Action | for optional TLVs that require an | 336 | | | error message if not recognized. | 337 | 16384-31743 | Specification | Experimental RFC needed | 338 | | Required | | 339 | 32768-49161 | Standards | This range is for optional TLVs | 340 | | Action | that can be silently dropped if not | 341 | | | recognized. | 342 | 49162-64511 | Specification | Experimental RFC needed | 343 | | Required | | 344 | 64512-65535 | Private Use | | 345 +-------------+---------------+-------------------------------------+ 347 Table 2: Non-FEC Path sub-TLV registry 349 IANA is requested to allocate the following values from the Non-FEC 350 Path sub-TLV registry as defined in Table 3. 352 +-------+-------------------------------------+---------------+ 353 | Value | Description | Reference | 354 +-------+-------------------------------------+---------------+ 355 | 0 | Reserved | This document | 356 | TBD2 | Segment Routing MPLS Tunnel sub-TLV | This document | 357 | 65535 | Reserved | This document | 358 +-------+-------------------------------------+---------------+ 360 Table 3: New Segment Routing Tunnel sub-TLV 362 7.2. Return Code 364 IANA is requested to create Non-FEC Path sub-TLV sub-registry for the 365 new Non-FEC Path TLV and assign a new Return Code value from the 366 "Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs) 367 Ping Parameters" registry, "Return Codes" sub-registry, as follows 368 using a Standards Action value. 370 +--------+-------------------------+---------------+ 371 | Value | Description | Reference | 372 +--------+-------------------------+---------------+ 373 | X TBD3 | Too Many TLVs Detected. | This document | 374 +--------+-------------------------+---------------+ 376 Table 4: New Return Code 378 8. Security Considerations 380 Security considerations discussed in [RFC5880], [RFC5884], [RFC7726], 381 and [RFC8029] apply to this document. 383 9. Acknowledgments 385 TBD 387 10. References 389 10.1. Normative References 391 [I-D.ietf-mpls-bfd-directed] 392 Mirsky, G., Tantsura, J., Varlashkin, I., and M. Chen, 393 "Bidirectional Forwarding Detection (BFD) Directed Return 394 Path", draft-ietf-mpls-bfd-directed-09 (work in progress), 395 August 2018. 397 [I-D.ietf-spring-segment-routing-mpls] 398 Bashandy, A., Filsfils, C., Previdi, S., Decraene, B., 399 Litkowski, S., and R. Shakir, "Segment Routing with MPLS 400 data plane", draft-ietf-spring-segment-routing-mpls-14 401 (work in progress), June 2018. 403 [I-D.mirsky-bfd-mpls-demand] 404 Mirsky, G., "BFD in Demand Mode over Point-to-Point MPLS 405 LSP", draft-mirsky-bfd-mpls-demand-03 (work in progress), 406 June 2018. 408 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 409 Requirement Levels", BCP 14, RFC 2119, 410 DOI 10.17487/RFC2119, March 1997, 411 . 413 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 414 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 415 . 417 [RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 418 (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, 419 DOI 10.17487/RFC5881, June 2010, 420 . 422 [RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 423 (BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883, 424 June 2010, . 426 [RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, 427 "Bidirectional Forwarding Detection (BFD) for MPLS Label 428 Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884, 429 June 2010, . 431 [RFC6428] Allan, D., Ed., Swallow, G., Ed., and J. Drake, Ed., 432 "Proactive Connectivity Verification, Continuity Check, 433 and Remote Defect Indication for the MPLS Transport 434 Profile", RFC 6428, DOI 10.17487/RFC6428, November 2011, 435 . 437 [RFC7726] Govindan, V., Rajaraman, K., Mirsky, G., Akiya, N., and S. 438 Aldrin, "Clarifying Procedures for Establishing BFD 439 Sessions for MPLS Label Switched Paths (LSPs)", RFC 7726, 440 DOI 10.17487/RFC7726, January 2016, 441 . 443 [RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N., 444 Aldrin, S., and M. Chen, "Detecting Multiprotocol Label 445 Switched (MPLS) Data-Plane Failures", RFC 8029, 446 DOI 10.17487/RFC8029, March 2017, 447 . 449 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 450 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 451 May 2017, . 453 [RFC8287] Kumar, N., Ed., Pignataro, C., Ed., Swallow, G., Akiya, 454 N., Kini, S., and M. Chen, "Label Switched Path (LSP) 455 Ping/Traceroute for Segment Routing (SR) IGP-Prefix and 456 IGP-Adjacency Segment Identifiers (SIDs) with MPLS Data 457 Planes", RFC 8287, DOI 10.17487/RFC8287, December 2017, 458 . 460 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 461 Decraene, B., Litkowski, S., and R. Shakir, "Segment 462 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 463 July 2018, . 465 10.2. Informative References 467 [I-D.ietf-mpls-static-yang] 468 Saad, T., Raza, K., Gandhi, R., Liu, X., and V. Beeram, "A 469 YANG Data Model for MPLS Static LSPs", draft-ietf-mpls- 470 static-yang-05 (work in progress), February 2018. 472 [I-D.ietf-spring-mpls-anycast-segments] 473 Sarkar, P., Gredler, H., Filsfils, C., Previdi, S., 474 Decraene, B., and M. Horneffer, "Anycast Segments in MPLS 475 based Segment Routing", draft-ietf-spring-mpls-anycast- 476 segments-02 (work in progress), January 2018. 478 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for 479 the Network Configuration Protocol (NETCONF)", RFC 6020, 480 DOI 10.17487/RFC6020, October 2010, 481 . 483 [RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and 484 L. Yong, "The Use of Entropy Labels in MPLS Forwarding", 485 RFC 6790, DOI 10.17487/RFC6790, November 2012, 486 . 488 [RFC8294] Liu, X., Qu, Y., Lindem, A., Hopps, C., and L. Berger, 489 "Common YANG Data Types for the Routing Area", RFC 8294, 490 DOI 10.17487/RFC8294, December 2017, 491 . 493 Authors' Addresses 495 Greg Mirsky 496 ZTE Corp. 498 Email: gregimirsky@gmail.com 500 Jeff Tantsura 501 Nuage Networks 503 Email: jefftant.ietf@gmail.com 505 Ilya Varlashkin 506 Google 508 Email: Ilya@nobulus.com 509 Mach(Guoyi) Chen 510 Huawei 512 Email: mach.chen@huawei.com