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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: December 24, 2017 Individual 6 I. Varlashkin 7 Google 8 M. Chen 9 Huawei 10 June 22, 2017 12 Bidirectional Forwarding Detection (BFD) in Segment Routing Networks 13 Using MPLS Dataplane 14 draft-mirsky-spring-bfd-01 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 http://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 December 24, 2017. 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 (http://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 When a BFD session is used to monitor a source routed unidirectional 158 path there may be a need to direct egress BFD peer to use specific 159 path for the reverse direction of the BFD session by using the BFD 160 Reverse Path TLV [I-D.ietf-mpls-bfd-directed]. For the case of MPLS 161 dataplane, Segment Routing Architecture 162 [I-D.ietf-spring-segment-routing] explains that "a segment is encoded 163 as an MPLS label. An ordered list of segments is encoded as a stack 164 of labels." YANG Data Model for MPLS Static LSPs 165 [I-D.ietf-mpls-static-yang] models outgoing MPLS labels to be imposed 166 as leaf-list [RFC6020], i.e., as array of rt-types:mpls-label 167 [I-D.ietf-rtgwg-routing-types] Following on that, this document 168 defines Segment Routing Static MPLS Tunnel sub-TLV that MAY be used 169 with the BFD Reverse Path TLV [I-D.ietf-mpls-bfd-directed]. The 170 format of the sub-TLV is presented in Figure 1. BFD Reverse TLV MAY 171 include zero or one SR Static MPLS Tunnel sub-TLV. 173 0 1 2 3 174 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 1 175 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 176 | SegRouting MPLS sub-TLV Type | Length | 177 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 178 | Label Entry 1 | 179 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 180 | Label Entry 2 | 181 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 182 ~ ~ 183 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 184 | Label Entry N | 185 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 187 Figure 1: Segment Routing Static MPLS Tunnel sub-TLV 189 The Segment Routing Tunnel sub-TLV Type is two octets in length, and 190 has a value of TBD (to be assigned by IANA as requested in 191 Section 5). 193 The egress LSR MUST use the Value field as label stack for BFD 194 control packets for the BFD session identified by the source IP 195 address of the MPLS LSP Ping packet and the value in the BFD 196 Discriminator TLV. Label Entries MUST be in network order. 198 As in [I-D.ietf-mpls-bfd-directed], empty BFD Reverse TLV requires 199 the egress BFD peer switch the reverse path of the BFD session, 200 specified by BFD Discriminator TLV, to IP network. If more than one 201 SR Static MPLS Tunnel sub-TLV is present, then the egress BFD peer 202 MUST send Echo Reply with Return Code field set to "Too Many TLVs 203 Detected" Table 2. 205 The Segment Routing Tunnel sub-TLV MAY be used in Reply Path TLV 206 defined in [RFC7110] 208 4. BFD Reverse Path TLV over Segment Routed MPLS Tunnel with Dynamic 209 Control Plane 211 When Segment Routed domain with MPLS data plane uses distributed 212 tunnel computation BFD Reverse Path TLV MAY use Target FEC sub-TLVs 213 defined in [I-D.ietf-mpls-spring-lsp-ping]. 215 5. IANA Considerations 216 5.1. Segment Routing Static MPLS Tunnel sub-TLV 218 The IANA is requested to assign new sub-TLV type from "Multiprotocol 219 Label Switching Architecture (MPLS) Label Switched Paths (LSPs) Ping 220 Parameters - TLVs" registry, "Sub-TLVs for TLV Types 1, 16, and 21" 221 sub-registry. 223 +----------+----------------------------------------+---------------+ 224 | Value | Description | Reference | 225 +----------+----------------------------------------+---------------+ 226 | X (TBD1) | Segment Routing Static MPLS Tunnel | This document | 227 | | sub-TLV | | 228 +----------+----------------------------------------+---------------+ 230 Table 1: New Segment Routing Tunnel sub-TLV 232 5.2. Return Code 234 The IANA is requested to assign a new Return Code value from the 235 "Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs) 236 Ping Parameters" registry, "Return Codes" sub-registry, as follows 237 using a Standards Action value. 239 +----------+-------------------------+---------------+ 240 | Value | Description | Reference | 241 +----------+-------------------------+---------------+ 242 | X (TBD2) | Too Many TLVs Detected. | This document | 243 +----------+-------------------------+---------------+ 245 Table 2: New Return Code 247 6. Security Considerations 249 Security considerations discussed in [RFC5880], [RFC5884], [RFC7726], 250 and [RFC8029] apply to this document. 252 7. Acknowledgements 254 TBD 256 8. References 258 8.1. Normative References 260 [I-D.ietf-mpls-bfd-directed] 261 Mirsky, G., Tantsura, J., Varlashkin, I., and M. Chen, 262 "Bidirectional Forwarding Detection (BFD) Directed Return 263 Path", draft-ietf-mpls-bfd-directed-07 (work in progress), 264 June 2017. 266 [I-D.ietf-mpls-spring-lsp-ping] 267 Kumar, N., Swallow, G., Pignataro, C., Akiya, N., Kini, 268 S., Gredler, H., and M. Chen, "Label Switched Path (LSP) 269 Ping/Traceroute for Segment Routing Networks with MPLS 270 Dataplane", draft-ietf-mpls-spring-lsp-ping-03 (work in 271 progress), June 2017. 273 [I-D.ietf-mpls-static-yang] 274 Saad, T., Raza, K., Gandhi, R., Liu, X., Beeram, V., Shah, 275 H., Bryskin, I., Chen, X., Jones, R., and B. Wen, "A YANG 276 Data Model for MPLS Static LSPs", draft-ietf-mpls-static- 277 yang-03 (work in progress), March 2017. 279 [I-D.ietf-spring-segment-routing] 280 Filsfils, C., Previdi, S., Decraene, B., Litkowski, S., 281 and R. Shakir, "Segment Routing Architecture", draft-ietf- 282 spring-segment-routing-12 (work in progress), June 2017. 284 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 285 Requirement Levels", BCP 14, RFC 2119, 286 DOI 10.17487/RFC2119, March 1997, 287 . 289 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 290 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 291 . 293 [RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 294 (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, 295 DOI 10.17487/RFC5881, June 2010, 296 . 298 [RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 299 (BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883, 300 June 2010, . 302 [RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, 303 "Bidirectional Forwarding Detection (BFD) for MPLS Label 304 Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884, 305 June 2010, . 307 [RFC6428] Allan, D., Ed., Swallow, G., Ed., and J. Drake, Ed., 308 "Proactive Connectivity Verification, Continuity Check, 309 and Remote Defect Indication for the MPLS Transport 310 Profile", RFC 6428, DOI 10.17487/RFC6428, November 2011, 311 . 313 [RFC7110] Chen, M., Cao, W., Ning, S., Jounay, F., and S. Delord, 314 "Return Path Specified Label Switched Path (LSP) Ping", 315 RFC 7110, DOI 10.17487/RFC7110, January 2014, 316 . 318 [RFC7726] Govindan, V., Rajaraman, K., Mirsky, G., Akiya, N., and S. 319 Aldrin, "Clarifying Procedures for Establishing BFD 320 Sessions for MPLS Label Switched Paths (LSPs)", RFC 7726, 321 DOI 10.17487/RFC7726, January 2016, 322 . 324 [RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N., 325 Aldrin, S., and M. Chen, "Detecting Multiprotocol Label 326 Switched (MPLS) Data-Plane Failures", RFC 8029, 327 DOI 10.17487/RFC8029, March 2017, 328 . 330 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 331 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 332 May 2017, . 334 8.2. Informative References 336 [I-D.ietf-rtgwg-routing-types] 337 Liu, X., Qu, Y., Lindem, A., Hopps, C., and L. Berger, 338 "Routing Area Common YANG Data Types", draft-ietf-rtgwg- 339 routing-types-06 (work in progress), June 2017. 341 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for 342 the Network Configuration Protocol (NETCONF)", RFC 6020, 343 DOI 10.17487/RFC6020, October 2010, 344 . 346 Authors' Addresses 348 Greg Mirsky 349 ZTE Corp. 351 Email: gregimirsky@gmail.com 352 Jeff Tantsura 353 Individual 355 Email: jefftant.ietf@gmail.com 357 Ilya Varlashkin 358 Google 360 Email: Ilya@nobulus.com 362 Mach(Guoyi) Chen 363 Huawei 365 Email: mach.chen@huawei.com