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Tantsura 5 Expires: April 27, 2018 Individual 6 I. Varlashkin 7 Google 8 M. Chen 9 Huawei 10 October 24, 2017 12 Bidirectional Forwarding Detection (BFD) in Segment Routing Networks 13 Using MPLS Dataplane 14 draft-mirsky-spring-bfd-02 16 Abstract 18 Segment Routing 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 kind of paths between systems. This document 24 defines how to use Label Switched Path Ping to bootstrap and control 25 path in reverse direction of a BFD session on the Segment Routing 26 static MPLS tunnel. 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 April 27, 2018. 45 Copyright Notice 47 Copyright (c) 2017 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 used in this document . . . . . . . . . . . . 3 64 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3 65 1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3 66 2. Bootstrapping BFD session over Segment Routed tunnel . . . . 3 67 3. Use BFD Reverse Path TLV over SDN-provisioned Segment Routed 68 MPLS Tunnel . . . . . . . . . . . . . . . . . . . . . . . . . 4 69 4. BFD Reverse Path TLV over Segment Routed MPLS Tunnel with 70 Dynamic Control Plane . . . . . . . . . . . . . . . . . . . . 5 71 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 72 5.1. Segment Routing Static MPLS Tunnel sub-TLV . . . . . . . 6 73 5.2. Return Code . . . . . . . . . . . . . . . . . . . . . . . 6 74 6. Security Considerations . . . . . . . . . . . . . . . . . . . 6 75 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 76 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 77 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 78 8.2. Informative References . . . . . . . . . . . . . . . . . 8 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 81 1. Introduction 83 [RFC5880], [RFC5881], and [RFC5883] established the Bidirectional 84 Forwarding Detection (BFD) protocol for IP networks. [RFC5884] and 85 [RFC7726] set rules of using BFD Asynchronous mode over Multiprotocol 86 Label Switching (MPLS) Label Switched Path (LSP). These latter 87 standards implicitly assume that the egress BFD peer, which is the 88 egress Label Edge Router (LER), will use the shortest path route 89 regardless of the path the ingress LER uses to send BFD control 90 packets towards it. 92 This document defines use of LSP Ping for Segment Routing networks 93 over MPLS dataplane [I-D.ietf-mpls-spring-lsp-ping] to bootstrap and 94 control path of a BFD session from the egress to ingress LER using 95 static MPLS tunnel. 97 1.1. Conventions used in this document 99 1.1.1. Terminology 101 BFD: Bidirectional Forwarding Detection 103 FEC: Forwarding Equivalence Class 105 MPLS: Multiprotocol Label Switching 107 LSP: Label Switching Path 109 LER: Label Edge Router 111 1.1.2. Requirements Language 113 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 114 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 115 "OPTIONAL" in this document are to be interpreted as described in BCP 116 14 [RFC2119] [RFC8174] when, and only when, they appear in all 117 capitals, as shown here. 119 2. Bootstrapping BFD session over Segment Routed tunnel 121 As demonstrated in [I-D.ietf-mpls-spring-lsp-ping] introduction of 122 Segment Routing network domains with an MPLS data plane requires 123 three new sub-TLVs that MAY be used with Target Forwarding 124 Equivalence Class (FEC) TLV. Section 6.1 addresses use of the new 125 sub-TLVs in Target FEC TLV in LSP ping and LSP traceroute. For the 126 case of LSP ping the [I-D.ietf-mpls-spring-lsp-ping] states that: 128 Initiator MUST include FEC(s) corresponding to the destination 129 segment. 131 Initiator, i.e. ingress LSR, MAY include FECs corresponding to 132 some or all of segments imposed in the label stack by the ingress 133 LSR to communicate the segments traversed. 135 It has been noted in [RFC5884] that a BFD session monitors for 136 defects particular tuple. [RFC7726] clarified how to 137 establish and operate multiple BFD sessions for the same tuple. Because only ingress edge router is aware of the SR- 139 based explicit route the egress edge router can associate the LSP 140 ping with BFD Discriminator TLV with only one of the FECs it 141 advertised for the particular segment. Thus this document clarifies 142 that: 144 When LSP Ping is used to bootstrap a BFD session the FEC 145 corresponding to the destination segment to be associated with the 146 BFD session MUST be as the very last sub-TLV in the Target FEC 147 TLV. 149 Encapsulation of a BFD Control packet in Segment Routing network with 150 MPLS dataplane MUST follow Section 7 [RFC5884] when IP/UDP header 151 used and MUST follow Section 3.4 [RFC6428] without IP/UDP header 152 being used. 154 3. Use BFD Reverse Path TLV over SDN-provisioned Segment Routed MPLS 155 Tunnel 157 For BFD over MPLS LSP case, per [RFC5884], egress LER MAY send BFD 158 control packet to the ingress LER either over IP network or an MPLS 159 LSP. Similarly, for the case of BFD over p2p segment tunnel with 160 MPLS data plane, the ingress LER MAY route BFD control packet over IP 161 network, as described in [RFC5883], or transmit over a segment 162 tunnel, as described in Section 7 [RFC5884]. In some cases there may 163 be a need to direct egress BFD peer to use specific path for the 164 reverse direction of the BFD session by using the BFD Reverse Path 165 TLV [I-D.ietf-mpls-bfd-directed]. For the case of MPLS dataplane, 166 Segment Routing Architecture [I-D.ietf-spring-segment-routing] 167 explains that "a segment is encoded as an MPLS label. An ordered 168 list of segments is encoded as a stack of labels." YANG Data Model 169 for MPLS Static LSPs [I-D.ietf-mpls-static-yang] models outgoing MPLS 170 labels to be imposed as leaf-list [RFC6020], i.e., as array of rt- 171 types:mpls-label [I-D.ietf-rtgwg-routing-types] Following on that, 172 this document defines Segment Routing Static MPLS Tunnel sub-TLV that 173 MAY be used with the BFD Reverse Path TLV 174 [I-D.ietf-mpls-bfd-directed]. The format of the sub-TLV is presented 175 in Figure 1. BFD Reverse TLV MAY include zero or one SR Static MPLS 176 Tunnel sub-TLV. 178 0 1 2 3 179 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 1 180 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 181 | SegRouting MPLS sub-TLV Type | Length | 182 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 183 | Label Entry 1 | 184 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 185 | Label Entry 2 | 186 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 187 ~ ~ 188 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 189 | Label Entry N | 190 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 192 Figure 1: Segment Routing Static MPLS Tunnel sub-TLV 194 The Segment Routing Tunnel sub-TLV Type is two octets in length, and 195 has a value of TBD (to be assigned by IANA as requested in 196 Section 5). 198 The egress LSR MUST use the Value field as label stack for BFD 199 control packets for the BFD session identified by the source IP 200 address of the MPLS LSP Ping packet and the value in the BFD 201 Discriminator TLV. Label Entries MUST be in network order. 203 As in [I-D.ietf-mpls-bfd-directed], empty BFD Reverse TLV requires 204 the egress BFD peer switch the reverse path of the BFD session, 205 specified by BFD Discriminator TLV, to the path selected based on 206 locally defined policy. If more than one SR Static MPLS Tunnel sub- 207 TLV is present, then the egress BFD peer MUST send Echo Reply with 208 Return Code field set to "Too Many TLVs Detected" Table 2. 210 The Segment Routing Tunnel sub-TLV MAY be used in Reply Path TLV 211 defined in [RFC7110] 213 4. BFD Reverse Path TLV over Segment Routed MPLS Tunnel with Dynamic 214 Control Plane 216 When Segment Routed domain with MPLS data plane uses distributed 217 tunnel computation BFD Reverse Path TLV MAY use Target FEC sub-TLVs 218 defined in [I-D.ietf-mpls-spring-lsp-ping]. 220 5. IANA Considerations 221 5.1. Segment Routing Static MPLS Tunnel sub-TLV 223 The IANA is requested to assign new sub-TLV type from "Multiprotocol 224 Label Switching Architecture (MPLS) Label Switched Paths (LSPs) Ping 225 Parameters - TLVs" registry, "Sub-TLVs for TLV Types 1, 16, and 21" 226 sub-registry. 228 +----------+----------------------------------------+---------------+ 229 | Value | Description | Reference | 230 +----------+----------------------------------------+---------------+ 231 | X (TBD1) | Segment Routing Static MPLS Tunnel | This document | 232 | | sub-TLV | | 233 +----------+----------------------------------------+---------------+ 235 Table 1: New Segment Routing Tunnel sub-TLV 237 5.2. Return Code 239 The IANA is requested to assign a new Return Code value from the 240 "Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs) 241 Ping Parameters" registry, "Return Codes" sub-registry, as follows 242 using a Standards Action value. 244 +----------+-------------------------+---------------+ 245 | Value | Description | Reference | 246 +----------+-------------------------+---------------+ 247 | X (TBD2) | Too Many TLVs Detected. | This document | 248 +----------+-------------------------+---------------+ 250 Table 2: New Return Code 252 6. Security Considerations 254 Security considerations discussed in [RFC5880], [RFC5884], [RFC7726], 255 and [RFC8029] apply to this document. 257 7. Acknowledgements 259 TBD 261 8. References 263 8.1. Normative References 265 [I-D.ietf-mpls-bfd-directed] 266 Mirsky, G., Tantsura, J., Varlashkin, I., and M. Chen, 267 "Bidirectional Forwarding Detection (BFD) Directed Return 268 Path", draft-ietf-mpls-bfd-directed-07 (work in progress), 269 June 2017. 271 [I-D.ietf-mpls-spring-lsp-ping] 272 Kumar, N., Pignataro, C., Swallow, G., Akiya, N., Kini, 273 S., and M. Chen, "Label Switched Path (LSP) Ping/ 274 Traceroute for Segment Routing IGP Prefix and Adjacency 275 SIDs with MPLS Data-plane", draft-ietf-mpls-spring-lsp- 276 ping-13 (work in progress), October 2017. 278 [I-D.ietf-spring-segment-routing] 279 Filsfils, C., Previdi, S., Decraene, B., Litkowski, S., 280 and R. Shakir, "Segment Routing Architecture", draft-ietf- 281 spring-segment-routing-12 (work in progress), June 2017. 283 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 284 Requirement Levels", BCP 14, RFC 2119, 285 DOI 10.17487/RFC2119, March 1997, 286 . 288 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 289 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 290 . 292 [RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 293 (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, 294 DOI 10.17487/RFC5881, June 2010, 295 . 297 [RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 298 (BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883, 299 June 2010, . 301 [RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, 302 "Bidirectional Forwarding Detection (BFD) for MPLS Label 303 Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884, 304 June 2010, . 306 [RFC6428] Allan, D., Ed., Swallow, G., Ed., and J. Drake, Ed., 307 "Proactive Connectivity Verification, Continuity Check, 308 and Remote Defect Indication for the MPLS Transport 309 Profile", RFC 6428, DOI 10.17487/RFC6428, November 2011, 310 . 312 [RFC7110] Chen, M., Cao, W., Ning, S., Jounay, F., and S. Delord, 313 "Return Path Specified Label Switched Path (LSP) Ping", 314 RFC 7110, DOI 10.17487/RFC7110, January 2014, 315 . 317 [RFC7726] Govindan, V., Rajaraman, K., Mirsky, G., Akiya, N., and S. 318 Aldrin, "Clarifying Procedures for Establishing BFD 319 Sessions for MPLS Label Switched Paths (LSPs)", RFC 7726, 320 DOI 10.17487/RFC7726, January 2016, 321 . 323 [RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N., 324 Aldrin, S., and M. Chen, "Detecting Multiprotocol Label 325 Switched (MPLS) Data-Plane Failures", RFC 8029, 326 DOI 10.17487/RFC8029, March 2017, 327 . 329 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 330 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 331 May 2017, . 333 8.2. Informative References 335 [I-D.ietf-mpls-static-yang] 336 Saad, T., Raza, K., Gandhi, R., Liu, X., Beeram, V., Shah, 337 H., Bryskin, I., Chen, X., Jones, R., and B. Wen, "A YANG 338 Data Model for MPLS Static LSPs", draft-ietf-mpls-static- 339 yang-04 (work in progress), July 2017. 341 [I-D.ietf-rtgwg-routing-types] 342 Liu, X., Qu, Y., Lindem, A., Hopps, C., and L. Berger, 343 "Routing Area Common YANG Data Types", draft-ietf-rtgwg- 344 routing-types-17 (work in progress), October 2017. 346 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for 347 the Network Configuration Protocol (NETCONF)", RFC 6020, 348 DOI 10.17487/RFC6020, October 2010, 349 . 351 Authors' Addresses 353 Greg Mirsky 354 ZTE Corp. 356 Email: gregimirsky@gmail.com 357 Jeff Tantsura 358 Individual 360 Email: jefftant.ietf@gmail.com 362 Ilya Varlashkin 363 Google 365 Email: Ilya@nobulus.com 367 Mach(Guoyi) Chen 368 Huawei 370 Email: mach.chen@huawei.com