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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-04) exists of draft-ietf-bfd-rfc5884-clarifications-02 == Outdated reference: A later version (-06) exists of draft-kumarkini-mpls-spring-lsp-ping-04 == Outdated reference: A later version (-08) exists of draft-previdi-6man-segment-routing-header-07 ** Obsolete normative reference: RFC 4379 (Obsoleted by RFC 8029) Summary: 1 error (**), 0 flaws (~~), 5 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 MPLS Working Group G. Mirsky 3 Internet-Draft J. Tantsura 4 Intended status: Standards Track Ericsson 5 Expires: March 11, 2016 I. Varlashkin 6 Google 7 M. Chen 8 Huawei 9 September 8, 2015 11 Bidirectional Forwarding Detection (BFD) Directed Return Path 12 draft-ietf-mpls-bfd-directed-01 14 Abstract 16 Bidirectional Forwarding Detection (BFD) is expected to monitor bi- 17 directional paths. When a BFD session monitors in its forward 18 direction an explicitly routed path there is a need to be able to 19 direct egress BFD peer to use specific path as reverse direction of 20 the BFD session. 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 http://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 March 11, 2016. 39 Copyright Notice 41 Copyright (c) 2015 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 (http://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 1.1. Conventions used in this document . . . . . . . . . . . . 3 58 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3 59 1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3 60 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 61 3. Direct Reverse BFD Path . . . . . . . . . . . . . . . . . . . 4 62 3.1. Case of MPLS Data Plane . . . . . . . . . . . . . . . . . 4 63 3.1.1. BFD Reverse Path TLV . . . . . . . . . . . . . . . . 4 64 3.1.2. Static and RSVP-TE sub-TLVs . . . . . . . . . . . . . 5 65 3.1.3. Segment Routing Tunnel sub-TLV . . . . . . . . . . . 5 66 3.2. Case of IPv6 Data Plane . . . . . . . . . . . . . . . . . 6 67 3.3. Bootstrapping BFD session with BFD Reverse Path over 68 Segment Routed tunnel . . . . . . . . . . . . . . . . . . 6 69 3.4. Return Codes . . . . . . . . . . . . . . . . . . . . . . 7 70 4. Use Case Scenario . . . . . . . . . . . . . . . . . . . . . . 7 71 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 72 5.1. TLV . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 73 5.2. Sub-TLV . . . . . . . . . . . . . . . . . . . . . . . . . 8 74 5.3. Return Codes . . . . . . . . . . . . . . . . . . . . . . 8 75 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 76 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 77 8. Normative References . . . . . . . . . . . . . . . . . . . . 9 78 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 80 1. Introduction 82 RFC 5880 [RFC5880], RFC 5881 [RFC5881], and RFC 5883 [RFC5883] 83 established the BFD protocol for IP networks and RFC 5884 [RFC5884] 84 set rules of using BFD asynchronous mode over IP/MPLS LSPs. All 85 standards implicitly assume that the egress BFD peer will use the 86 shortest path route regardless of route being used to send BFD 87 control packets towards it. As result, if the ingress BFD peer sends 88 its BFD control packets over explicit path that is diverging from the 89 best route, then reverse direction of the BFD session is likely not 90 to be on co-routed bi-directional path with the forward direction of 91 the BFD session. And because BFD control packets are not guaranteed 92 to cross the same links and nodes in both directions detection of 93 Loss of Continuity (LoC) defect in forward direction may demonstrate 94 positive negatives. 96 This document defines the extension to LSP Ping [RFC4379], BFD 97 Reverse Path TLV, and proposes that it to be used to instruct the 98 egress BFD peer to use explicit path for its BFD control packets 99 associated with the particular BFD session. The TLV will be 100 allocated from the TLV and sub-TLV registry defined by RFC 4379 101 [RFC4379]. As a special case, forward and reverse directions of the 102 BFD session can form bi-directional co-routed associated channel. 104 1.1. Conventions used in this document 106 1.1.1. Terminology 108 BFD: Bidirectional Forwarding Detection 110 MPLS: Multiprotocol Label Switching 112 LSP: Label Switching Path 114 LoC: Loss of Continuity 116 1.1.2. Requirements Language 118 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 119 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 120 "OPTIONAL" in this document are to be interpreted as described in 121 [RFC2119]. 123 2. Problem Statement 125 BFD is best suited to monitor bi-directional co-routed paths. In 126 most cases, given stable environments, the forward and reverse 127 direction between two nodes is likely to be co-routed, this 128 fulfilling the implicit BFD requirements. If BFD is used to monitor 129 unidirectional explicitly routed paths, e.g. MPLS-TE LSPs, its 130 control packets in forward direction would be in-band using the 131 mechanism defined in [RFC5884] and [RFC5586]. But the reverse 132 direction of the BFD session would still follow the shortest path 133 route and that might lead to the following problem in detecting 134 failures on the unidirectional explicit path: 136 o a failure detection by ingress node on the reverse path cannot be 137 interpreted as bi-directional failure with all the certainty and 138 thus trigger, for example, protection switchover of the forward 139 direction without possibility of being false positive or false 140 negative. 142 To address these challenges the egress BFD peer should be instructed 143 to use specific path for its control packets. 145 3. Direct Reverse BFD Path 147 3.1. Case of MPLS Data Plane 149 LSP ping, defined in [RFC4379], uses BFD Discriminator TLV [RFC5884] 150 to bootstrap a BFD session over an MPLS LSP. This document defines a 151 new TLV, BFD Reverse Path TLV, that MUST contain a single sub-TLV 152 that can be used to carry information about reverse path for the 153 specified in BFD Discriminator TLV session. 155 3.1.1. BFD Reverse Path TLV 157 The BFD Reverse Path TLV is an optional TLV within the LSP ping 158 protocol. However, if used, the BFD Discriminator TLV MUST be 159 included in an Echo Request message as well. If the BFD 160 Discriminator TLV is not present when the BFD Reverse Path TLV is 161 included, then it MUST be treated as malformed Echo Request, as 162 described in [RFC4379]. 164 The BFD Reverse Path TLV carries the specified path that BFD control 165 packets of the BFD session referenced in the BFD Discriminator TLV 166 are required to follow. The format of the BFD Reverse Path TLV is as 167 presented in Figure 1. 169 0 1 2 3 170 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 1 171 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 172 | BFD Reverse Path TLV Type | Length | 173 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 174 | Reverse Path | 175 ~ ~ 176 | | 177 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 179 Figure 1: BFD Reverse Path TLV 181 BFD Reverse Path TLV Type is 2 octets in length and value to be 182 assigned by IANA. 184 Length is 2 octets in length and defines the length in octets of the 185 Reverse Path field. 187 Reverse Path field contains a sub-TLV. Any Target FEC sub-TLV, 188 already or in the future defined, from IANA sub-registry Sub-TLVs for 189 TLV Types 1, 16, and 21 of MPLS LSP Ping Parameters registry MAY be 190 used in this field. Only one sub-TLV MUST be included in the Reverse 191 Path TLV. If more than one sub-TLVs are present in the Reverse Path 192 TLV, then only the first sub-TLV MUST be used and the rest MUST be 193 silently discarded. 195 If the egress LSR cannot find path specified in the Reverse Path TLV 196 it MUST send Echo Reply with the received Reverse Path TLV and set 197 the return code to "Failed to establish the BFD session. The 198 specified reverse path was not found" Section 3.4. The egress LSR 199 MAY establish the BFD session over IP network according to [RFC5884]. 201 3.1.2. Static and RSVP-TE sub-TLVs 203 When explicit path on MPLS data plane set either as Static or RSVP-TE 204 LSP respective sub-TLVs defined in [RFC7110] identify explicit return 205 path. 207 3.1.3. Segment Routing Tunnel sub-TLV 209 In addition to Static and RSVP-TE, Segment Routing with MPLS data 210 plane can be used to set explicit path. In this case a new sub-TLV 211 is defined in this document as presented in Figure 2. 213 0 1 2 3 214 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 1 215 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 216 | SegRouting MPLS sub-TLV Type | Length | 217 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 218 | Label Entry 1 | 219 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 220 | Label Entry 2 | 221 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 222 ~ ~ 223 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 224 | Label Entry N | 225 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 227 Figure 2: Segment Routing MPLS Tunnel sub-TLV 229 The Segment Routing Tunnel sub-TLV Type is two octets in length, and 230 will be allocated by IANA. 232 The egress LSR MUST use the Value field as label stack for BFD 233 control packets for the BFD session identified by source IP address 234 and value in BFD Discriminator TLV. 236 The Segment Routing Tunnel sub-TLV MAY be used in Reply Path TLV 237 defined in [RFC7110] 239 3.2. Case of IPv6 Data Plane 241 IPv6 can be data plane of choice for Segment Routed tunnels 242 [I-D.previdi-6man-segment-routing-header]. In such networks the BFD 243 Reverse Path TLV described in Section 3.1.1 can be used as well. To 244 specify reverse path of a BFD session in IPv6 environment the BFD 245 Discriminator TLV MUST be used along with the BFD Reverse Path TLV. 246 The BFD Reverse Path TLV in IPv6 network MUST include sub-TLV. 248 0 1 2 3 249 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 1 250 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 251 | SegRouting IPv6 sub-TLV Type | Length | 252 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 253 | | 254 | IPv6 Prefix | 255 | | 256 | | 257 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 258 | | 259 | IPv6 Prefix | 260 | | 261 | | 262 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 263 ~ ~ 264 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 266 Figure 3: Segment Routing IPv6 Tunnel sub-TLV 268 3.3. Bootstrapping BFD session with BFD Reverse Path over Segment 269 Routed tunnel 271 As discussed in [I-D.kumarkini-mpls-spring-lsp-ping] introduction of 272 Segment Routing network domains with MPLS data plane adds three new 273 sub-TLVs that may be used with Target FEC TLV. Section 6.1 addresses 274 use of new sub-TLVs in Target FEC TLV in LSP ping and LSP traceroute. 275 For the case of LSP ping the [I-D.kumarkini-mpls-spring-lsp-ping] 276 states that: 278 "Initiator MUST include FEC(s) corresponding to the destination 279 segment. 281 Initiator, i.e. ingress LSR, MAY include FECs corresponding to some 282 or all of segments imposed in the label stack by the ingress LSR to 283 communicate the segments traversed. " 285 When LSP ping is used to bootstrap BFD session this document updates 286 this and defines that LSP Ping MUST include the FEC corresponding to 287 the destination segment and SHOULD NOT include FECs corresponding to 288 some or all of segment imposed by the ingress LSR. Operationally 289 such restriction would not cause any problem or uncertainty as LSP 290 ping with FECs corresponding to some or all segments or traceroute 291 MAY precede the LSP ping that bootstraps the BFD session. 293 3.4. Return Codes 295 This document defines the following Return Codes: 297 o "Failed to establish the BFD session. The specified reverse path 298 was not found", (TBD4). When a specified reverse path is not 299 available at the egress LSR, an Echo Reply with the return code 300 set to "Failed to establish the BFD session. The specified 301 reverse path was not found" MUST be sent back to the ingress LSR . 302 (Section 3.1.1) 304 4. Use Case Scenario 306 In network presented in Figure 4 node A monitors two tunnels to node 307 H: A-B-C-D-G-H and A-B-E-F-G-H. To bootstrap BFD session to monitor 308 the first tunnel, node A MUST include BFD Discriminator TLV with 309 Discriminator value foobar-1 and MAY include BFD Reverse Path TLV 310 that references H-G-D-C-B-A tunnel. To bootstrap BFD session to 311 monitor the second tunnel, node A MUST include BFD Discriminator TLV 312 with Discriminator value foobar-2 313 [I-D.ietf-bfd-rfc5884-clarifications] and MAY include BFD Reverse 314 Path TLV that references H-G-F-E-B-A tunnel. 316 C---------D 317 | | 318 A-------B G-----H 319 | | 320 E---------F 322 Figure 4: Use Case for BFD Reverse Path TLV 324 If an operator needs node H to monitor path to node A, e.g. 325 H-G-D-C-B-A tunnel, then by looking up list of known Reverse Paths it 326 MAY find and use existing BFD sessions. 328 5. IANA Considerations 330 5.1. TLV 332 The IANA is requested to assign a new value for BFD Reverse Path TLV 333 from the "Multiprotocol Label Switching Architecture (MPLS) Label 334 Switched Paths (LSPs) Ping Parameters - TLVs" registry, "TLVs and 335 sub-TLVs" sub-registry. 337 +----------+----------------------+---------------+ 338 | Value | Description | Reference | 339 +----------+----------------------+---------------+ 340 | X (TBD1) | BFD Reverse Path TLV | This document | 341 +----------+----------------------+---------------+ 343 Table 1: New BFD Reverse Type TLV 345 5.2. Sub-TLV 347 The IANA is requested to assign two new sub-TLV types from 348 "Multiprotocol Label Switching Architecture (MPLS) Label Switched 349 Paths (LSPs) Ping Parameters - TLVs" registry, "Sub-TLVs for TLV 350 Types 1, 16, and 21" sub-registry. 352 +----------+-------------------------------------+---------------+ 353 | Value | Description | Reference | 354 +----------+-------------------------------------+---------------+ 355 | X (TBD2) | Segment Routing MPLS Tunnel sub-TLV | This document | 356 | X (TBD3) | Segment Routing IPv6 Tunnel sub-TLV | This document | 357 +----------+-------------------------------------+---------------+ 359 Table 2: New Segment Routing Tunnel sub-TLV 361 5.3. Return Codes 363 The IANA is requested to assign a new Return Code value from the 364 "Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs) 365 Ping Parameters" registry, "Return Codes" sub-registry, as follows 366 using a Standards Action value. 368 +----------+----------------------------------------+---------------+ 369 | Value | Description | Reference | 370 +----------+----------------------------------------+---------------+ 371 | X (TBD4) | Failed to establish the BFD session. | This document | 372 | | The specified reverse path was not | | 373 | | found. | | 374 +----------+----------------------------------------+---------------+ 376 Table 3: New Return Code 378 6. Security Considerations 380 Security considerations discussed in [RFC5880], [RFC5884], and 381 [RFC4379], apply to this document. 383 7. Acknowledgements 385 8. Normative References 387 [I-D.ietf-bfd-rfc5884-clarifications] 388 Govindan, V., Rajaraman, K., Mirsky, G., Akiya, N., and S. 389 Aldrin, "Clarifications to RFC 5884", draft-ietf-bfd- 390 rfc5884-clarifications-02 (work in progress), June 2015. 392 [I-D.kumarkini-mpls-spring-lsp-ping] 393 Kumar, N., Swallow, G., Pignataro, C., Akiya, N., Kini, 394 S., Gredler, H., and M. Chen, "Label Switched Path (LSP) 395 Ping/Trace for Segment Routing Networks Using MPLS 396 Dataplane", draft-kumarkini-mpls-spring-lsp-ping-04 (work 397 in progress), July 2015. 399 [I-D.previdi-6man-segment-routing-header] 400 Previdi, S., Filsfils, C., Field, B., Leung, I., Vyncke, 401 E., and D. Lebrun, "IPv6 Segment Routing Header (SRH)", 402 draft-previdi-6man-segment-routing-header-07 (work in 403 progress), July 2015. 405 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 406 Requirement Levels", BCP 14, RFC 2119, 407 DOI 10.17487/RFC2119, March 1997, 408 . 410 [RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol 411 Label Switched (MPLS) Data Plane Failures", RFC 4379, 412 DOI 10.17487/RFC4379, February 2006, 413 . 415 [RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed., 416 "MPLS Generic Associated Channel", RFC 5586, 417 DOI 10.17487/RFC5586, June 2009, 418 . 420 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 421 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 422 . 424 [RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 425 (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, 426 DOI 10.17487/RFC5881, June 2010, 427 . 429 [RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 430 (BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883, 431 June 2010, . 433 [RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, 434 "Bidirectional Forwarding Detection (BFD) for MPLS Label 435 Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884, 436 June 2010, . 438 [RFC7110] Chen, M., Cao, W., Ning, S., Jounay, F., and S. Delord, 439 "Return Path Specified Label Switched Path (LSP) Ping", 440 RFC 7110, DOI 10.17487/RFC7110, January 2014, 441 . 443 Authors' Addresses 445 Greg Mirsky 446 Ericsson 448 Email: gregory.mirsky@ericsson.com 450 Jeff Tantsura 451 Ericsson 453 Email: jeff.tantsura@ericsson.com 455 Ilya Varlashkin 456 Google 458 Email: Ilya@nobulus.com 460 Mach(Guoyi) Chen 461 Huawei 463 Email: mach.chen@huawei.com