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Mirsky 3 Internet-Draft ZTE Corp. 4 Intended status: Informational June 2, 2018 5 Expires: December 4, 2018 7 Operations, Administration and Maintenance (OAM) for Deterministic 8 Networks (DetNet) 9 draft-mirsky-detnet-oam-00 11 Abstract 13 This document lists functional requirements for Operations, 14 Administration and Maintenance (OAM) toolset in Deterministic 15 Networks (DetNet) and, using these requirements, and analyzes 16 possible DetNet data plane solutions. 18 Status of This Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at https://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on December 4, 2018. 35 Copyright Notice 37 Copyright (c) 2018 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (https://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 53 2. Conventions used in this document . . . . . . . . . . . . . . 2 54 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2 55 2.2. Keywords . . . . . . . . . . . . . . . . . . . . . . . . 3 56 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 3 57 4. DetNet Data Plane in Support of Active OAM . . . . . . . . . 4 58 4.1. DetNet Active OAM Encapsulation . . . . . . . . . . . . . 6 59 4.2. DetNet PREF Interaction with Active OAM . . . . . . . . . 6 60 4.3. Alternative Encapsulation for DetNet . . . . . . . . . . 7 61 5. Use of Hybrid OAM in DetNet . . . . . . . . . . . . . . . . . 8 62 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 63 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 64 8. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . 9 65 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 66 9.1. Normative References . . . . . . . . . . . . . . . . . . 9 67 9.2. Informational References . . . . . . . . . . . . . . . . 10 68 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10 70 1. Introduction 72 [I-D.ietf-detnet-architecture] introduces and explains Deterministic 73 Networks (DetNet) architecture and how the Packet Replication and 74 Elimination function (PREF) can be used to ensure low packet drop 75 ratio in DetNet domain. 77 Operations, Administration and Maintenance (OAM) protocols are used 78 to detect, localize defects in the network, and monitor network 79 performance. Some OAM functions, e.g., failure detection, work in 80 the network proactively, while others, e.g., defect localization, 81 usually performed on-demand. These tasks achieved by a combination 82 of active and hybrid, as defined in [RFC7799], OAM methods. 84 This document lists the functional requirements toward OAM for DetNet 85 domain. The list can further be used to for gap analysis of 86 available OAM tools to identify possible enhancements of existing or 87 whether new OAM tools are required to support proactive and on-demand 88 path monitoring and service validation. 90 2. Conventions used in this document 92 2.1. Terminology 94 The term "DetNet OAM" used in this document interchangeably with 95 longer version "set of OAM protocols, methods and tools for 96 Deterministic Networks". 98 AC Associated Channel 100 CW Control Word 102 DetNet Deterministic Networks 104 d-CW DetNet Control Word 106 OAM: Operations, Administration and Maintenance 108 PREF Packet Replication and Elimination Function 110 PW Pseudowire 112 RDI Remote Defect Indication 114 Underlay Network or Underlay Layer: The network that provides 115 connectivity between the DetNet nodes. MPLS network providing LSP 116 connectivity between DetNet nodes is an example of underlay layer. 118 DetNet Node - a node that is an actor in the DetNet domain. DetNet 119 domain edge node and node that performs PREF within the domain are 120 examples of DetNet node. 122 2.2. Keywords 124 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 125 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 126 "OPTIONAL" in this document are to be interpreted as described in BCP 127 14 [RFC2119] [RFC8174] when, and only when, they appear in all 128 capitals, as shown here. 130 3. Requirements 132 This section lists requirements for OAM in DetNet domain: 134 1. The listed requirements MUST be supported with any type of 135 underlay network over which a DetNet domain can be realized. 137 2. It MUST be possible to initiate DetNet OAM session from any 138 DetNet node towards another DetNet node(s) within given domain. 140 3. It SHOULD be possible to initialize DetNet OAM session from a 141 centralized controller. 143 4. DetNet OAM MUST support proactive and on-demand OAM monitoring 144 and measurement methods. 146 5. DetNet OAM packets MUST be in-band, i.e. follow exactly the same 147 path as DetNet data plane traffic both for unidirectional and 148 bi-directional DetNet paths. 150 6. DetNet OAM MUST support unidirectional OAM methods, continuity 151 check, connectivity verification, and performance measurement. 153 7. DetNet OAM MUST support bi-directional OAM methods. Such OAM 154 methods MAY combine in-band monitoring or measurement in the 155 forward direction and out-of-bound notification in the reverse 156 direction, i.e. from egress to ingress end point of the OAM test 157 session. 159 8. DetNet OAM MUST support proactive monitoring of a DetNet node 160 availability in the given DetNet domain. 162 9. DetNet OAM MUST support Path Maximum Transmission Unit 163 discovery. 165 10. DetNet OAM MUST support Remote Defect Indication (RDI) 166 notification to the DetNet node performing continuity checking. 168 11. DetNet OAM MUST support performance measurement methods. 170 12. DetNet OAM MUST support unidirectional performance measurement 171 methods. Calculated performance metrics MUST include but are 172 not limited to throughput, loss, delay and delay variation 173 metrics. [RFC6374] provides great details on performance 174 measurement and performance metrics. 176 13. DetNet OAM MUST support defect notification mechanism, like 177 Alarm Indication Signal. Any DetNet node in the given DetNet 178 domain MAY originate a defect notification addressed to any 179 subset of nodes within the domain. 181 14. DetNet OAM MUST support methods to enable survivability of the 182 DetNet domain. These recovery methods MAY use protection 183 switching and restoration. 185 4. DetNet Data Plane in Support of Active OAM 187 OAM protocols and mechanisms act within the data plane of the 188 particular networking layer. And thus it is critical that the data 189 plane encapsulation supports OAM mechanisms in such a way to comply 190 with the above-listed requirements. One of such examples that 191 require special consideration is requirement #5: 193 DetNet OAM packets MUST be in-band, i.e. follow exactly the same 194 path as DetNet data plane traffic both for unidirectional and bi- 195 directional DetNet paths. 197 The data plane encapsulation for DetNet specified in 198 [I-D.ietf-detnet-dp-sol] has been analyzed in details in 199 [I-D.bryant-detnet-mpls-dp] and [I-D.malis-detnet-ip-dp] for use in 200 MPLS and IP networks respectively. For the MPLS underlay network 201 DetNet flows to be encapsulated analogous to pseudowires (PW) over 202 MPLS packet switched network, as described in [RFC3985], [RFC4385]. 203 Generic PW MPLS Control Word (CW), defined in [RFC4385], for DetNet 204 displayed in Figure 1. 206 0 1 2 3 207 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 1 208 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 209 |0 0 0 0| Sequence Number | 210 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 212 Figure 1: DetNet Control Word Format 214 PREF in the DetNet domain composed by a combination of nodes that 215 perform replication and elimination sub-functions. The elimination 216 sub-function always uses packet sequencing information, e.g., value 217 in the Sequence Number field of DetNet CW (d-CW). The replication 218 sub-function uses one of two options: 220 o use S-Label and d-CW information; 222 o use S-Label information. 224 For data packets Figure 2 presents an example of PREF in DetNet 225 domain regardless of how the replication sub-function realized in the 226 domain. 228 1111 11111111 111111 112212 112212 132213 229 CE1----EN1--------R1-------R2-------R3--------EN2----CE2 230 \2 22222/ 3 / 231 \2222222 /----+ 3 / 232 +------R4------------------------+ 233 333333333333333333333333 235 Figure 2: DetNet Data Plane Based on PW 237 4.1. DetNet Active OAM Encapsulation 239 DetNet OAM, like PW OAM, uses PW Associated Channel Header defined in 240 [RFC4385]. Figure 3 displays encapsulation of a DetNet active OAM 241 packet. Figure 4 displays format of the DetNet Associated Channel 242 (AC). 244 +---------------------------------+ 245 | | 246 | DetNet Flow | 247 | OAM Packet | 248 | | 249 +---------------------------------+ <--\ 250 | DetNet Associated Channel | | 251 +=================================+ +--> DetNet OAM data plane 252 | S-Label | | MPLS encapsulation 253 +---------------------------------+ <--/ 254 | T-Label(s) | 255 +---------------------------------+ 256 | Data-Link | 257 +---------------------------------+ 258 | Physical | 259 +---------------------------------+ 261 Figure 3: DetNet PW OAM Packet Encapsulation 263 0 1 2 3 264 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 1 265 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 266 |0 0 0 1|0 0 0 0|0 0 0 0 0 0 0 0| Channel Type | 267 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 269 Figure 4: DetNet Associated Channel Header Format 271 4.2. DetNet PREF Interaction with Active OAM 273 Consider the scenario when EN1 injects DetNet active OAM packet with 274 the same S-Label as the DetNet service reflected in Figure 2. EN1 is 275 the first node with the replication sub-function. If the replication 276 uses S-Label information and the sequencing information in d-CW (the 277 first option), then EN1 will only forward the OAM packet without 278 replicating it because OAM encapsulation doesn't include d-CW. The 279 path that active OAM packet traverses through the DetNet domain 280 presented in Figure 5 with 'O'. The figure clearly demonstrates that 281 the DetNet OAM packet does not traverse all the segments that are 282 traversed by the DetNet data packet as displayed in Figure 2. 284 O O O O 285 CE1----EN1--------R1-------R2-------R3--------EN2----CE2 286 \ / / 287 \ /----+ / 288 +------R4------------------------+ 290 Figure 5: OAM in DetNet Data Plane Based on PW 292 If the replication is based solely on S-Label (the second option), 293 EN1 node will replicate the OAM packet accordingly. The replicated 294 packet will be processed by the replication function at R4. As 295 result, the same OAM packet will be forwarded and another copy 296 injected into the network. This case displayed in Figure 6. The OAM 297 packet does traverse all links and nodes that the DetNet data packet 298 of the monitored flow traverses but the egress node EN2 receives 299 multiple, three in this example, copies of the same packet because 300 the elimination function cannot be applied to the DetNet active OAM 301 packet. 303 O O OO OO 304 CE1----EN1--------R1-------R2-------R3--------EN2----CE2 305 \O O/ O/ 306 \ O/----+ / 307 +------R4------------------------+ 308 O 310 Figure 6: Over-Replication of Active OAM Packets 312 4.3. Alternative Encapsulation for DetNet 314 Introduction of DetNet header, that includes all necessary 315 characteristic information to efficiently, among other scenarios, use 316 multipath underlay, perform PERF, as part of DetNet service layer 317 encapsulation allows DetNet active OAM packets to be in-band with the 318 monitored DetNet data flow. Figure 7 presents the format of DetNet 319 packet with MPLS encapsulation. 321 +---------------------------------+ 322 | | 323 | DetNet Flow | 324 | Payload or OAM | 325 | Packet | 326 +---------------------------------+ 327 | DetNet Header | 328 ~ ~ 329 | | 330 +=================================+ 331 | S-Label | 332 +---------------------------------+ 333 | T-Label(s) | 334 +---------------------------------+ 335 | Data-Link | 336 +---------------------------------+ 337 | Physical | 338 +---------------------------------+ 340 Figure 7: DetNet Packet with DetNet Header Encapsulation over MPLS 341 Underlay 343 Demultiplexing of type of the payload encapsulated in the DetNet 344 packet achieved using a field that explicitly identifies, e.g., OAM, 345 Ethernet, or IPvX. 347 5. Use of Hybrid OAM in DetNet 349 Hybrid OAM methods are used in performance monitoring and defined in 350 [RFC7799] as: 352 Hybrid Methods are Methods of Measurement that use a combination 353 of Active Methods and Passive Methods ... 355 A hybrid measurement method may produce metrics as close to passive 356 but it still alters something in a data packet even if that is value 357 of a designated field in the packet encapsulation. One example of 358 such hybrid measurement method is the Alternate Marking method 359 described in [RFC8321]. Reserving the field for the Alternate 360 Marking method in the DetNet Header will enhance available to an 361 operator set of DetNet OAM tools. 363 6. IANA Considerations 365 This document does not propose any IANA consideration. This section 366 may be removed. 368 7. Security Considerations 370 This document lists the OAM requirements for a DetNet domain and does 371 not raise any security concerns or issues in addition to ones common 372 to networking. 374 8. Acknowledgment 376 TBD 378 9. References 380 9.1. Normative References 382 [I-D.bryant-detnet-mpls-dp] 383 Bryant, S. and M. Chen, "Operation of Deterministic 384 Networks over MPLS", draft-bryant-detnet-mpls-dp-00 (work 385 in progress), March 2018. 387 [I-D.ietf-detnet-architecture] 388 Finn, N., Thubert, P., Varga, B., and J. Farkas, 389 "Deterministic Networking Architecture", draft-ietf- 390 detnet-architecture-05 (work in progress), May 2018. 392 [I-D.ietf-detnet-dp-sol] 393 Korhonen, J., Andersson, L., Jiang, Y., Finn, N., Varga, 394 B., Farkas, J., Bernardos, C., Mizrahi, T., and L. Berger, 395 "DetNet Data Plane Encapsulation", draft-ietf-detnet-dp- 396 sol-04 (work in progress), March 2018. 398 [I-D.malis-detnet-ip-dp] 399 Malis, A., Bryant, S., Chen, M., and B. Varga, "DetNet IP 400 Encapsulation", draft-malis-detnet-ip-dp-00 (work in 401 progress), March 2018. 403 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 404 Requirement Levels", BCP 14, RFC 2119, 405 DOI 10.17487/RFC2119, March 1997, 406 . 408 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 409 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 410 May 2017, . 412 9.2. Informational References 414 [RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation 415 Edge-to-Edge (PWE3) Architecture", RFC 3985, 416 DOI 10.17487/RFC3985, March 2005, 417 . 419 [RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson, 420 "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for 421 Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385, 422 February 2006, . 424 [RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay 425 Measurement for MPLS Networks", RFC 6374, 426 DOI 10.17487/RFC6374, September 2011, 427 . 429 [RFC7799] Morton, A., "Active and Passive Metrics and Methods (with 430 Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799, 431 May 2016, . 433 [RFC8321] Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli, 434 L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi, 435 "Alternate-Marking Method for Passive and Hybrid 436 Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321, 437 January 2018, . 439 Author's Address 441 Greg Mirsky 442 ZTE Corp. 444 Email: gregimirsky@gmail.com