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Pignataro 4 Updates: 5885 (if approved) Cisco Systems 5 Intended status: Standards Track June 30, 2015 6 Expires: January 1, 2016 8 Seamless BFD for VCCV 9 draft-gp-pals-seamless-vccv-01 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 will be extended in 17 future to include definition of procedures for S-BFD over Tunnels. 18 This document extends the CV values defined in RFC5885. 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at http://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on January 1, 2016. 37 Copyright Notice 39 Copyright (c) 2015 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Background . . . . . . . . . . . . . . . . . . . . . . . . . 2 55 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 56 2. S-BFD Connectivity Verification . . . . . . . . . . . . . . . 3 57 2.1. Co-existence of S-BFD and BFD capabilites . . . . . . . . 4 58 2.2. S-BFD CV Operation . . . . . . . . . . . . . . . . . . . 4 59 2.2.1. S-BFD Initiator Operation . . . . . . . . . . . . . . 4 60 2.2.2. S-BFD Reflector Operation . . . . . . . . . . . . . . 4 61 2.2.2.1. S-BFD Reflector Demultiplexing . . . . . . . . . 5 62 2.2.2.2. S-BFD Reflector transmission of control packets . 5 63 2.2.2.3. S-BFD Reflector advertisement of target 64 discriminators using LDP . . . . . . . . . . . . 5 65 2.2.2.4. S-BFD Reflector advertisement of target 66 discriminators using L2TP . . . . . . . . . . . . 5 67 2.2.2.5. Provisioning of S-BFD Reflector target 68 discriminators . . . . . . . . . . . . . . . . . 5 69 2.2.2.6. Probing of S-BFD Reflector target discriminators 70 using alert discriminators . . . . . . . . . . . 5 71 2.3. S-BFD Encapsulation . . . . . . . . . . . . . . . . . . . 6 72 2.4. S-BFD CV Types . . . . . . . . . . . . . . . . . . . . . 6 73 3. Capability Selection . . . . . . . . . . . . . . . . . . . . 6 74 4. Security Considerations . . . . . . . . . . . . . . . . . . . 7 75 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 76 5.1. MPLS CV Types for the VCCV Interface Parameters Sub-TLV . 7 77 5.2. L2TPv3 CV Types for the VCCV Capability AVP . . . . . . . 8 78 5.3. PW Associated Channel Type . . . . . . . . . . . . . . . 8 79 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 80 7. Contributing Authors . . . . . . . . . . . . . . . . . . . . 9 81 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 82 8.1. Normative References . . . . . . . . . . . . . . . . . . 9 83 8.2. Informative References . . . . . . . . . . . . . . . . . 10 84 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 86 1. Background 88 BFD for VCCV [RFC5885] defines the CV types for BFD using VCCV, 89 protocol operation and the required packet encapsulation formats. 90 This document extends those procedures, CV type values to enable 91 S-BFD [I-D.ietf-bfd-seamless-base] operation for VCCV. 93 The new S-BFD CV Types are PW demultiplexer-agnostic, and hence 94 applicable for both MPLS and Layer Two Tunneling Protocol version 3 95 (L2TPv3) pseudowire demultiplexers. This document concerns itself 96 with the S-BFD VCCV operation over single-segment pseudowires (SS- 97 PWs). The scope of this document is as follows: 99 This specification describes procedures only for S-BFD 100 asynchronous mode. 102 S-BFD Echo mode is outside the scope of this specification. 104 S-BFD operation for fault detection and status signaling is 105 outside the scope of this specification. 107 1.1. Requirements Language 109 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 110 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 111 "OPTIONAL" in this document are to be interpreted as described in 112 [RFC2119]. 114 2. S-BFD Connectivity Verification 116 S-BFD protocol provides continuity check services by monitoring the 117 S-BFD control packets sent and received over the VCCV channel of the 118 PW. The term is used throughout this 119 document to be consistent with [RFC5885]. 121 This section defines the CV types to be used for S-BFD. It also 122 defines the procedures for S-BFD discriminator advertisement for the 123 SBD reflector and the procedure for S-BFD Initiator operation. 125 Two CV Types are defined for S-BFD. Table 1 summarizes the S-BFD CV 126 Types, grouping them by encapsulation (i.e., with versus without IP/ 127 UDP headers) for fault detection only. S-BFD for fault detection and 128 status signaling is outside the scope of this specification. 130 +---------------------------------------+-----------+---------------+ 131 | | Fault | Fault | 132 | | Detection | Detection and | 133 | | Only | Status | 134 | | | Signaling | 135 +---------------------------------------+-----------+---------------+ 136 | S-BFD, IP/UDP Encapsulation (with | TBD1 | N/A | 137 | IP/UDP Headers) | (Note1) | | 138 | | | | 139 | S-BFD, PW-ACH Encapsulation when | TBD2 | N/A | 140 | using MPLS PW or L2SS Encapsulation | (Note2) | | 141 | when using L2TP PW (without IP/UDP | | | 142 | Headers) | | | 143 +---------------------------------------+-----------+---------------+ 145 Table 1: Bitmask Values for BFD CV Types 147 Two new bits are requested from IANA to indicate S-BFD operation. 149 2.1. Co-existence of S-BFD and BFD capabilites 151 Since the CV types for S-BFD and BFD are unique, BFD and S-BFD 152 capabilities can be advertised concurrently. 154 2.2. S-BFD CV Operation 156 2.2.1. S-BFD Initiator Operation 158 The S-BFD Initiator SHOULD bootstrap S-BFD sessions after it learns 159 the discriminator of the remote target identifier through one or more 160 of the following methods: 162 1. Advertisements of S-BFD discriminators made through AVP/ TLVs 163 defined in L2TP/ LDP. 165 2. Provisioning of S-BFD discriminators. 167 3. Probing remote S-BFD discriminators through S-BFD Alert 168 discriminators [I-D.akiya-bfd-seamless-alert-discrim] 170 S-BFD Initiator operation MUST be according to the specifications in 171 Section 7.2 of [I-D.ietf-bfd-seamless-base]. 173 2.2.2. S-BFD Reflector Operation 175 When as pseudowire signalling protocol such as LDP or L2TPv3 is in 176 use the S-BFD Reflector advertises its target discriminators using 177 that signalling protocol. When static PWs are in use the target 178 discriminator of S-BFD needs to be provisioned on the S-BFD 179 Initiator nodes. 181 All point to point pseudowires are bidirectional, the S-BFD 182 Reflector therefore reflects the S-BFD packet back to the 183 Initiator using the VCCV channel of the reverse direction of the 184 PW on which it was received. 186 It is observed that the reflector has enough information to 187 reflect the S-BFD Async packet received by it back to the S-BFD 188 initiator using the fields of the L2TPv3 headers. 190 S-BFD Reflector operation for BFD protocol fields MUST be 191 according to the specifications in Section TBD of 192 [I-D.ietf-bfd-seamless-base]. 194 2.2.2.1. S-BFD Reflector Demultiplexing 196 TBD 198 2.2.2.2. S-BFD Reflector transmission of control packets 200 The procedures of S-BFD Reflector described in 201 [I-D.ietf-bfd-seamless-base] apply for S-BFD using VCCV. 203 2.2.2.3. S-BFD Reflector advertisement of target discriminators using 204 LDP 206 TBD. 208 2.2.2.4. S-BFD Reflector advertisement of target discriminators using 209 L2TP 211 The S-BFD Reflector MUST use the AVP 212 [I-D.gp-l2tpext-sbfd-discriminator] defined for advertising its 213 target discriminators using L2TP. 215 2.2.2.5. Provisioning of S-BFD Reflector target discriminators 217 S-BFD target discriminators MAY be provisioned when static PWs are 218 used. 220 2.2.2.6. Probing of S-BFD Reflector target discriminators using alert 221 discriminators 223 S-BFD alert discriminators MAY be used to probe S-BFD target 224 discriminators. If a node implements S-BFD reflector, it SHOULD 225 respond to Alert discriminator requests received from potential S-BFD 226 Initiators. 228 2.3. S-BFD Encapsulation 230 Unless specified differently below, the encapsulation of S-BFD 231 packets is the identical the method specified in Sec.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-base]. 239 * The encapsulation of the S-BFD header fields MUST be according 240 to Sec.7.2.2 of [I-D.ietf-bfd-seamless-base]. 242 o PW-ACH/ L2SS BFD Encapsulation (BFD without IP/UDP Headers) 244 * The encapsulation of S-BFD packets using this format MUST be 245 according to Sec.3.2 of [RFC5885] with the exception of the PW- 246 ACH/ L2SS type. 248 * When VCCV carries PW-ACH/ L2SS-encapsulated S-BFD (i.e., "raw" 249 S-BFD), the PW-ACH (pseudowire CW's) or L2SS' Channel Type MUST 250 be set to TBD2 to indicate "S-BFD Control, PW-ACH/ L2SS- 251 encapsulated" (i.e., S-BFD without IP/UDP headers; see 252 Section 5.3). This is to allow the identification of the 253 encased S-BFD payload when demultiplexing the VCCV control 254 channel. 256 2.4. S-BFD CV Types 258 3. Capability Selection 260 When multiple S-BFD CV Types are advertised, and after applying the 261 rules in [RFC5885], the set that both ends of the pseudowire have in 262 common is determined. If the two ends have more than one S-BFD CV 263 Type in common, the following list of S-BFD CV Types is considered in 264 the order of the lowest list number CV Type to the highest list 265 number CV Type, and the CV Type with the lowest list number is used: 267 1. TBD1 - S-BFD IP/UDP-encapsulated, for PW Fault Detection only. 269 2. TBD2 - S-BFD PW-ACH/ L2SS-encapsulated (without IP/UDP headers), 270 for PW Fault Detection only. 272 The order of capability selection between S-BFD and BFD is defined as 273 follows: 275 +--------------------------+-----------+-----------+----------------+ 276 | Advertised capabilities | BFD Only | SBFD Only | Both S-BFD and | 277 | of PE1/ PE2 | | | BFD | 278 +--------------------------+-----------+-----------+----------------+ 279 | BFD Only | BFD | None | BFD Only | 280 | | | (Note1) | | 281 | | | | | 282 | S-BFD Only | None | S-BFD | S-BFD only | 283 | | (Note1) | | | 284 | | | | | 285 | Both S-BFD and BFD | BFD only | S-BFD | Both SBFD and | 286 | | | only | BFD | 287 +--------------------------+-----------+-----------+----------------+ 289 Table 2: Capability Selection Matrix for BFD and S-BFD 291 Note1: Can we mandate failing the bringup of the PW in case of a 292 capability mismatch? 294 4. Security Considerations 296 Security measures described in [RFC5885] and 297 [I-D.ietf-bfd-seamless-base] are to be followed. 299 5. IANA Considerations 301 5.1. MPLS CV Types for the VCCV Interface Parameters Sub-TLV 303 The VCCV Interface Parameters Sub-TLV codepoint is defined in 304 [RFC4446], and the VCCV CV Types registry is defined in [RFC5085]. 306 This section lists the new BFD CV Types. 308 IANA has augmented the "VCCV Connectivity Verification (CV) Types" 309 registry in the Pseudowire Name Spaces reachable from [IANA]. These 310 are bitfield values. CV Type values TBD are specified in Section 2 311 of this document. 313 MPLS Connectivity Verification (CV) Types: 315 Bit (Value) Description Reference 316 =========== =========== ============== 317 TBD1(0xY) S-BFD IP/UDP-encapsulated, this document 318 for PW Fault Detection only 319 TBD2(0xZ) S-BFD PW-ACH/L2SS-encapsulated, this document 320 for PW Fault Detection only 322 5.2. L2TPv3 CV Types for the VCCV Capability AVP 324 This section lists the new requests for S-BFD CV Types to be added to 325 the existing "VCCV Capability AVP" registry in the L2TP name spaces. 326 The Layer Two Tunneling Protocol "L2TP" Name Spaces are reachable 327 from [IANA]. IANA is requested to assign the following L2TPv3 328 Connectivity Verification (CV) Types in the VCCV Capability AVP 329 Values registry. 331 VCCV Capability AVP (Attribute Type 96) Values 332 ---------------------------------------------- 334 L2TPv3 Connectivity Verification (CV) Types: 336 Bit (Value) Description Reference 337 =========== =========== ============== 338 TBD1(0xY) S-BFD IP/UDP-encapsulated, this document 339 for PW Fault Detection only 340 TBD2(0xZ) S-BFD L2SS-encapsulated, this document 341 for PW Fault Detection only 343 5.3. PW Associated Channel Type 345 As per the IANA considerations in [RFC5586], IANA is requested to 346 allocate the following Channel Types in the "MPLS Generalized 347 Associated Channel (G-ACh) Types" registry: 349 IANA has reserved a new Pseudowire Associated Channel Type value as 350 follows: 352 Registry: 353 TLV 354 Value Description Follows Reference 355 ------ ---------------------------------- ------- --------------- 356 TBD2 S-BFD Control, PW-ACH/L2SS No [This document] 357 encapsulation 358 (without IP/UDP Headers) 360 6. Acknowledgements 362 Authors would like to thank Nobo Akiya, Stewart Bryant, Pawel 363 Sowinski and Greg Mirsky for providing the core inputs of this 364 document and for performing thorough reviews and providing number of 365 comments. Authors would also like to thank Yuanlong for comments 366 received. 368 7. Contributing Authors 370 Mallik Mudigonda 371 Cisco Systems 372 Email: mmudigon@cisco.com 374 8. References 376 8.1. Normative References 378 [I-D.akiya-bfd-seamless-alert-discrim] 379 Akiya, N., Pignataro, C., and D. Ward, "Seamless 380 Bidirectional Forwarding Detection (S-BFD) Alert 381 Discriminator", draft-akiya-bfd-seamless-alert-discrim-03 382 (work in progress), October 2014. 384 [I-D.gp-l2tpext-sbfd-discriminator] 385 Govindan, V. and C. Pignataro, "Advertising S-BFD 386 Discriminators in L2TPv3", draft-gp-l2tpext-sbfd- 387 discriminator-00 (work in progress), March 2015. 389 [I-D.ietf-bfd-seamless-base] 390 Akiya, N., Pignataro, C., Ward, D., Bhatia, M., and J. 391 Networks, "Seamless Bidirectional Forwarding Detection 392 (S-BFD)", draft-ietf-bfd-seamless-base-05 (work in 393 progress), June 2015. 395 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 396 Requirement Levels", BCP 14, RFC 2119, March 1997. 398 [RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson, 399 "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for 400 Use over an MPLS PSN", RFC 4385, February 2006. 402 [RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge 403 Emulation (PWE3)", BCP 116, RFC 4446, April 2006. 405 [RFC5085] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit 406 Connectivity Verification (VCCV): A Control Channel for 407 Pseudowires", RFC 5085, December 2007. 409 [RFC5586] Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic 410 Associated Channel", RFC 5586, June 2009. 412 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 413 (BFD)", RFC 5880, June 2010. 415 [RFC5885] Nadeau, T. and C. Pignataro, "Bidirectional Forwarding 416 Detection (BFD) for the Pseudowire Virtual Circuit 417 Connectivity Verification (VCCV)", RFC 5885, June 2010. 419 8.2. Informative References 421 [IANA] Internet Assigned Numbers Authority, "Protocol 422 Registries", . 424 Authors' Addresses 426 Vengada Prasad Govindan 427 Cisco Systems 429 Email: venggovi@cisco.com 431 Carlos Pignataro 432 Cisco Systems 434 Email: cpignata@cisco.com