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Pignataro 4 Updates: 5885 (if approved) Cisco 5 Intended status: Standards Track April 28, 2016 6 Expires: October 30, 2016 8 Seamless BFD for VCCV 9 draft-ietf-pals-seamless-vccv-03 11 Abstract 13 This document extends the procedures and Connectivity Verification 14 (CV) types already defined for Bidirectional Forwarding Detection 15 (BFD) for Virtual Circuit Connectivity Verification (VCCV) to define 16 Seamless BFD (S-BFD) for VCCV. This document updates RFC 5885, 17 extending the CV Values and the Capability Selection. 19 Status of This Memo 21 This Internet-Draft is submitted in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at http://datatracker.ietf.org/drafts/current/. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 This Internet-Draft will expire on October 30, 2016. 36 Copyright Notice 38 Copyright (c) 2016 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (http://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. Code Components extracted from this document must 47 include Simplified BSD License text as described in Section 4.e of 48 the Trust Legal Provisions and are provided without warranty as 49 described in the Simplified BSD License. 51 Table of Contents 53 1. Background . . . . . . . . . . . . . . . . . . . . . . . . . 2 54 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 55 2. S-BFD Connectivity Verification . . . . . . . . . . . . . . . 3 56 2.1. Co-existence of S-BFD and BFD Capabilites . . . . . . . . 4 57 2.2. S-BFD CV Operation . . . . . . . . . . . . . . . . . . . 4 58 2.2.1. S-BFD Initiator Operation . . . . . . . . . . . . . . 4 59 2.2.2. S-BFD Reflector Operation . . . . . . . . . . . . . . 5 60 2.2.2.1. Demultiplexing . . . . . . . . . . . . . . . . . 5 61 2.2.2.2. Transmission of Control Packets . . . . . . . . . 5 62 2.2.2.3. Advertisement of Target Discriminators Using LDP 5 63 2.2.2.4. Advertisement of Target Discriminators Using L2TP 5 64 2.2.2.5. Provisioning of Target Discriminators . . . . . . 6 65 2.3. S-BFD Encapsulation . . . . . . . . . . . . . . . . . . . 6 66 2.4. S-BFD CV Types . . . . . . . . . . . . . . . . . . . . . 6 67 3. Capability Selection . . . . . . . . . . . . . . . . . . . . 6 68 4. Security Considerations . . . . . . . . . . . . . . . . . . . 7 69 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 70 5.1. MPLS CV Types for the VCCV Interface Parameters Sub-TLV . 7 71 5.2. L2TPv3 CV Types for the VCCV Capability AVP . . . . . . . 8 72 5.3. PW Associated Channel Type . . . . . . . . . . . . . . . 8 73 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 74 7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9 75 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 76 8.1. Normative References . . . . . . . . . . . . . . . . . . 9 77 8.2. Informative References . . . . . . . . . . . . . . . . . 10 78 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 80 1. Background 82 BFD for VCCV [RFC5885] defines the CV types for BFD using VCCV, 83 protocol operation and the required packet encapsulation formats. 84 This document extends those procedures, CV type values to enable 85 S-BFD [I-D.ietf-bfd-seamless-base] operation for VCCV. 87 The new S-BFD CV Types are Pseudowire (PW) demultiplexer-agnostic, 88 and hence applicable for both MPLS and Layer Two Tunneling Protocol 89 version 3 (L2TPv3) pseudowire demultiplexers. This document concerns 90 itself with the S-BFD VCCV operation over single-segment pseudowires 91 (SS-PWs). The scope of this document is as follows: 93 This specification describes procedures only for S-BFD 94 asynchronous mode. 96 S-BFD Echo mode is outside the scope of this specification. 98 S-BFD operation for fault detection and status signaling is 99 outside the scope of this specification. 101 This document specifies the use of a single S-BFD discriminator per 102 Pseudowire. There are cases where multiple S-BFD discriminators per 103 PW can be useful. One such cases is using different S-BFD 104 discriminators per Flow within a FAT PW [RFC6391]; however, the 105 mapping between Flows and discriminators is a prerequisite. FAT PWs 106 can be supported as described in Section 7 of [RFC6391]. 108 1.1. Requirements Language 110 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 111 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 112 "OPTIONAL" in this document are to be interpreted as described in 113 [RFC2119]. 115 2. S-BFD Connectivity Verification 117 S-BFD protocol provides continuity check services by monitoring the 118 S-BFD control packets sent and received over the VCCV channel of the 119 PW. The term "Connectivity Verification" is used throughout this 120 document to be consistent with [RFC5885]. 122 This section defines the CV types to be used for S-BFD. It also 123 defines the procedures for the S-BFD reflector and S-BFD Initiator 124 operation. 126 Two CV Types are defined for S-BFD. Table 1 summarizes the S-BFD CV 127 Types, grouping them by encapsulation (i.e., with versus without IP/ 128 UDP headers) for fault detection only. S-BFD for fault detection and 129 status signaling is outside the scope of this specification. 131 +----------------------------------------+-----------+--------------+ 132 | | Fault | Fault | 133 | | Detection | Detection | 134 | | Only | and Status | 135 | | | Signaling | 136 +----------------------------------------+-----------+--------------+ 137 | S-BFD, IP/UDP Encapsulation (with | TBD1 | N/A | 138 | IP/UDP Headers) | | | 139 | | | | 140 | S-BFD, PW-ACH Encapsulation when using | TBD2 | N/A | 141 | MPLS PW or L2-Specific Sublayer (L2SS) | | | 142 | Encapsulation when using L2TP PW | | | 143 | (without IP/UDP Headers) | | | 144 +----------------------------------------+-----------+--------------+ 146 Table 1: Bitmask Values for BFD CV Types 148 Two new bits are requested from IANA to indicate S-BFD operation. 150 2.1. Co-existence of S-BFD and BFD Capabilites 152 Since the CV types for S-BFD and BFD are unique, BFD and S-BFD 153 capabilities can be advertised concurrently. 155 2.2. S-BFD CV Operation 157 2.2.1. S-BFD Initiator Operation 159 The S-BFD Initiator SHOULD bootstrap S-BFD sessions after it learns 160 the discriminator of the remote target identifier. This can be 161 achieved, for example but not limited to, through one or more of the 162 following methods: 164 1. Advertisements of S-BFD discriminators made through a PW 165 signaling protocol, for example AVP/TLVs defined in L2TP/LDP. 167 2. Provisioning of S-BFD discriminators by manual configuration of 168 the PE/LCCEs. 170 3. Assignment of S-BFD discriminators by a controller. 172 4. Probing remote S-BFD discriminators through a mechanism such as 173 S-BFD Alert discriminators [I-D.akiya-bfd-seamless-alert-discrim] 175 S-BFD Initiator operation MUST be according to the specifications in 176 Section 7.2 of [I-D.ietf-bfd-seamless-base]. 178 2.2.2. S-BFD Reflector Operation 180 When a pseudowire signaling protocol such as LDP or L2TPv3 is in 181 use, the S-BFD Reflector can advertise its target discriminators 182 using that signaling protocol. When static PWs are in use the 183 target discriminator of S-BFD needs to be provisioned on the S-BFD 184 Initiator nodes. 186 All point to point pseudowires are bidirectional, the S-BFD 187 Reflector therefore reflects the S-BFD packet back to the 188 Initiator using the VCCV channel of the reverse direction of the 189 PW on which it was received. 191 It is observed that the reflector has enough information to 192 reflect the S-BFD Async packet received by it back to the S-BFD 193 initiator using the PW context (e.g., fields of the L2TPv3 194 headers). 196 S-BFD Reflector operation for BFD protocol fields MUST be 197 according to the specifications of [I-D.ietf-bfd-seamless-base]. 199 2.2.2.1. Demultiplexing 201 Demultiplexing of S-BFD is achieved using the PW context, following 202 the procedures in Section 7.1 of [I-D.ietf-bfd-seamless-base]. 204 2.2.2.2. Transmission of Control Packets 206 The procedures of S-BFD Reflector described in 207 [I-D.ietf-bfd-seamless-base] apply for S-BFD using VCCV. 209 2.2.2.3. Advertisement of Target Discriminators Using LDP 211 The advertisement of the target discriminator using LDP is left for 212 further study. It should be noted that S-BFD can still be used with 213 signaled PWs over an MPLS PSN, by provisioning of the S-BFD 214 discriminators or by learning the S-BFD discriminators by other 215 means. 217 2.2.2.4. Advertisement of Target Discriminators Using L2TP 219 The S-BFD Reflector MUST use the AVP 220 [I-D.ietf-l2tpext-sbfd-discriminator] defined for advertising its 221 target discriminators using L2TP. 223 2.2.2.5. Provisioning of Target Discriminators 225 S-BFD target discriminators MAY be provisioned when static PWs are 226 used. 228 2.3. S-BFD Encapsulation 230 Unless specified differently below, the encapsulation of S-BFD 231 packets is identical to the method specified in Section 3.2 [RFC5885] 232 and in [RFC5880] for the encapsulation of BFD packets. 234 o IP/UDP BFD Encapsulation (BFD with IP/UDP Headers) 236 * The destination UDP port for the IP encapsulated S-BFD packet 237 MUST be 7784 [I-D.ietf-bfd-seamless-ip]. 239 * The encapsulation of the S-BFD header fields MUST be according 240 to Section 7.3.2 of [I-D.ietf-bfd-seamless-base]. 242 * The Time to Live (TTL) (IPv4) or Hop Limit (IPv6) is set to 243 255. 245 o PW-ACH/ L2SS BFD Encapsulation (BFD without IP/UDP Headers) 247 * The encapsulation of S-BFD packets using this format MUST be 248 according to Section 3.2 of [RFC5885] with the exception of the 249 value for the PW-ACH/L2SS type. 251 * When VCCV carries PW-ACH/ L2SS-encapsulated S-BFD (i.e., "raw" 252 S-BFD), the PW-ACH (pseudowire CW's) or L2SS' Channel Type MUST 253 be set to TBD3 to indicate "S-BFD Control, PW-ACH/ L2SS- 254 encapsulated" (i.e., S-BFD without IP/UDP headers; see 255 Section 5.3). This is to allow the identification of the 256 encased S-BFD payload when demultiplexing the VCCV control 257 channel. 259 2.4. S-BFD CV Types 261 3. Capability Selection 263 When multiple S-BFD CV Types are advertised, and after applying the 264 rules in [RFC5885], the set that both ends of the pseudowire have in 265 common is determined. If the two ends have more than one S-BFD CV 266 Type in common, the following list of S-BFD CV Types is considered in 267 the order of the lowest list number CV Type to the highest list 268 number CV Type, and the CV Type with the lowest list number is used: 270 1. TBD1 - S-BFD IP/UDP-encapsulated, for PW Fault Detection only. 272 2. TBD2 - S-BFD PW-ACH/ L2SS-encapsulated (without IP/UDP headers), 273 for PW Fault Detection only. 275 The order of capability selection between S-BFD and BFD is defined as 276 follows: 278 +----------------------------+---------+----------+-----------------+ 279 | Advertised capabilities of | BFD | SBFD | Both S-BFD and | 280 | PE1/ PE2 | Only | Only | BFD | 281 +----------------------------+---------+----------+-----------------+ 282 | BFD Only | BFD | None | BFD Only | 283 | | | | | 284 | S-BFD Only | None | S-BFD | S-BFD only | 285 | | | | | 286 | Both S-BFD and BFD | BFD | S-BFD | Both SBFD and | 287 | | only | only | BFD | 288 +----------------------------+---------+----------+-----------------+ 290 Table 2: Capability Selection Matrix for BFD and S-BFD 292 4. Security Considerations 294 Security considerations for VCCV are addressed in Section 10 of 295 [RFC5085]. The introduction of the S-BFD Connectivity Verification 296 (CV) Types introduces no new security risks for VCCV. 297 Implementations of the additional CV Types defined herein are subject 298 to the same security considerations as defined in [RFC5085] as well 299 as [I-D.ietf-bfd-seamless-base]. 301 The IP/UDP encasulation of S-BFD makes use of the TTL/Hop Limit 302 procedures described in the Generalized TTL Security Mechanism (GTSM) 303 [RFC5082]) as a security mechanism. 305 This specification does not raise any additional security issues 306 beyond these. 308 5. IANA Considerations 310 5.1. MPLS CV Types for the VCCV Interface Parameters Sub-TLV 312 The VCCV Interface Parameters Sub-TLV codepoint is defined in 313 [RFC4446], and the VCCV CV Types registry is defined in [RFC5085]. 315 This section lists the new BFD CV Types. 317 IANA has augmented the "MPLS VCCV Connectivity Verification (CV) 318 Types" registry in the Pseudowire Name Spaces reachable from 320 [IANA-PWE3]. These are bitfield values. CV Type values are 321 specified in Section 2 of this document. 323 MPLS Connectivity Verification (CV) Types: 325 Bit (Value) Description Reference 326 =========== =========== ============== 327 TBD1(0xY) S-BFD IP/UDP-encapsulated, This document 328 for PW Fault Detection only 329 TBD2(0xZ) S-BFD PW-ACH-encapsulated, This document 330 for PW Fault Detection only 332 5.2. L2TPv3 CV Types for the VCCV Capability AVP 334 This section lists the new requests for S-BFD "L2TPv3 Connectivity 335 Verification (CV) Types" to be added to the existing "VCCV Capability 336 AVP" registry in the L2TP name spaces. The Layer Two Tunneling 337 Protocol "L2TP" Name Spaces are reachable from [IANA-L2TP]. IANA is 338 requested to assign the following L2TPv3 Connectivity Verification 339 (CV) Types in the VCCV Capability AVP Values registry. 341 VCCV Capability AVP (Attribute Type 96) Values 342 ---------------------------------------------- 344 L2TPv3 Connectivity Verification (CV) Types: 346 Bit (Value) Description Reference 347 =========== =========== ============== 348 TBD1(0xY) S-BFD IP/UDP-encapsulated, This document 349 for PW Fault Detection only 350 TBD2(0xZ) S-BFD L2SS-encapsulated, This document 351 for PW Fault Detection only 353 5.3. PW Associated Channel Type 355 As per the IANA considerations in [RFC5586], IANA is requested to 356 allocate the following Channel Types in the "MPLS Generalized 357 Associated Channel (G-ACh) Types" registry: 359 IANA has reserved a new Pseudowire Associated Channel Type value as 360 follows: 362 Registry: 363 TLV 364 Value Description Follows Reference 365 ------ ---------------------------------- ------- --------------- 366 TBD3 S-BFD Control, PW-ACH/L2SS No [This document] 367 encapsulation 368 (without IP/UDP Headers) 370 6. Acknowledgments 372 The authors would like to thank Nobo Akiya, Stewart Bryant, Greg 373 Mirsky, and Pawel Sowinski, Yuanlong, Andrew Malis, and Alexander 374 Vainshtein for providing input to this document and for performing 375 thorough reviews and useful comments. 377 7. Contributors 379 Mallik Mudigonda 380 Cisco Systems, Inc. 382 Email: mmudigon@cisco.com 384 8. References 386 8.1. Normative References 388 [I-D.ietf-bfd-seamless-base] 389 Akiya, N., Pignataro, C., Ward, D., Bhatia, M., and J. 390 Networks, "Seamless Bidirectional Forwarding Detection 391 (S-BFD)", draft-ietf-bfd-seamless-base-09 (work in 392 progress), April 2016. 394 [I-D.ietf-bfd-seamless-ip] 395 Akiya, N., Pignataro, C., and D. Ward, "Seamless 396 Bidirectional Forwarding Detection (S-BFD) for IPv4, IPv6 397 and MPLS", draft-ietf-bfd-seamless-ip-04 (work in 398 progress), April 2016. 400 [I-D.ietf-l2tpext-sbfd-discriminator] 401 Govindan, V. and C. Pignataro, "Advertising Seamless 402 Bidirectional Forwarding Detection (S-BFD) Discriminators 403 in Layer Two Tunneling Protocol, Version 3 (L2TPv3)", 404 draft-ietf-l2tpext-sbfd-discriminator-05 (work in 405 progress), April 2016. 407 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 408 Requirement Levels", BCP 14, RFC 2119, 409 DOI 10.17487/RFC2119, March 1997, 410 . 412 [RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge 413 Emulation (PWE3)", BCP 116, RFC 4446, 414 DOI 10.17487/RFC4446, April 2006, 415 . 417 [RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C. 418 Pignataro, "The Generalized TTL Security Mechanism 419 (GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007, 420 . 422 [RFC5085] Nadeau, T., Ed. and C. Pignataro, Ed., "Pseudowire Virtual 423 Circuit Connectivity Verification (VCCV): A Control 424 Channel for Pseudowires", RFC 5085, DOI 10.17487/RFC5085, 425 December 2007, . 427 [RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed., 428 "MPLS Generic Associated Channel", RFC 5586, 429 DOI 10.17487/RFC5586, June 2009, 430 . 432 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 433 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 434 . 436 [RFC5885] Nadeau, T., Ed. and C. Pignataro, Ed., "Bidirectional 437 Forwarding Detection (BFD) for the Pseudowire Virtual 438 Circuit Connectivity Verification (VCCV)", RFC 5885, 439 DOI 10.17487/RFC5885, June 2010, 440 . 442 8.2. Informative References 444 [I-D.akiya-bfd-seamless-alert-discrim] 445 Akiya, N., Pignataro, C., and D. Ward, "Seamless 446 Bidirectional Forwarding Detection (S-BFD) Alert 447 Discriminator", draft-akiya-bfd-seamless-alert-discrim-03 448 (work in progress), October 2014. 450 [IANA-L2TP] 451 Internet Assigned Numbers Authority, "Layer Two Tunneling 452 Protocol "L2TP"", May 2015, 453 . 455 [IANA-PWE3] 456 Internet Assigned Numbers Authority, "Pseudowire Name 457 Spaces (PWE3)", January 2016, 458 . 460 [RFC6391] Bryant, S., Ed., Filsfils, C., Drafz, U., Kompella, V., 461 Regan, J., and S. Amante, "Flow-Aware Transport of 462 Pseudowires over an MPLS Packet Switched Network", 463 RFC 6391, DOI 10.17487/RFC6391, November 2011, 464 . 466 Authors' Addresses 468 Vengada Prasad Govindan 469 Cisco Systems, Inc. 471 Email: venggovi@cisco.com 473 Carlos Pignataro 474 Cisco Systems, Inc. 476 Email: cpignata@cisco.com