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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-13) exists of draft-ietf-detnet-architecture-04 == Outdated reference: A later version (-09) exists of draft-ietf-detnet-problem-statement-02 == Outdated reference: A later version (-20) exists of draft-ietf-detnet-use-cases-13 == Outdated reference: A later version (-15) exists of draft-ietf-spring-segment-routing-14 Summary: 0 errors (**), 0 flaws (~~), 6 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 DetNet P. Thubert, Ed. 3 Internet-Draft Cisco 4 Intended status: Standards Track Z. Brodard 5 Expires: July 19, 2018 Ecole Polytechnique 6 H. Jiang 7 Telecom Bretagne 8 January 15, 2018 10 BIER-TE-based OAM, Replication and Elimination 11 draft-thubert-bier-replication-elimination-02 13 Abstract 15 This specification leverages Bit Index Explicit Replication - Traffic 16 Engineering to control in the data plane the DetNet Replication and 17 Elimination activities, and to provide traceability on links where 18 replication and loss happen, in a manner that is abstract to the 19 forwarding information. 21 Status of This Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at https://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on July 19, 2018. 38 Copyright Notice 40 Copyright (c) 2018 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (https://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 56 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 57 3. On BIER - Traffic Engineering . . . . . . . . . . . . . . . . 3 58 4. BIER-TE-based Replication and Elimination Control . . . . . . 4 59 5. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 60 6. Implementation Status . . . . . . . . . . . . . . . . . . . . 8 61 7. Security considerations . . . . . . . . . . . . . . . . . . . 9 62 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 63 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 64 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 65 10.1. Normative References . . . . . . . . . . . . . . . . . . 9 66 10.2. Informative References . . . . . . . . . . . . . . . . . 10 67 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 69 1. Introduction 71 Deterministic Networking (DetNet) [I-D.ietf-detnet-problem-statement] 72 provides a capability to carry unicast or multicast data flows for 73 real-time applications with extremely low data loss rates and known 74 upper bound maximum latency [I-D.ietf-detnet-architecture]. 76 DetNet applies to multiple environments where there is a desire to 77 replace a point to point serial cable or a multidrop bus by a 78 switched or routed infrastucture, in order to scale, lower costs, and 79 simplify management. One classical use case is found in particular 80 in the context of the convergence of IT with Operational Technology 81 (OT), also referred to as the Industrial Internet. But there are 82 many others use cases [I-D.ietf-detnet-use-cases], for instance in in 83 professional audio and video, automotive, radio fronthauls, etc.. 85 The DetNet data plane alternatives [I-D.dt-detnet-dp-alt] studies the 86 applicability of existing and emerging dataplane techniques that can 87 be leveraged to enable DetNet properties in IP networks. One 88 critical feature in the dataplane is traceability, the capability to 89 control the activity of intermediate nodes on a packet. For 90 instance, if Replication and Elimination is applied to a packet, then 91 it is desirable to determine which node performed a certain copy of 92 that packet that is circulating in the network. 94 Traceability belongs to Operations, Administration, and Maintenance 95 (OAM) which is the toolset for fault detection and isolation, and for 96 performance measurement. More can be found on OAM Tools in "An 97 Overview of Operations, Administration and Maintenance (OAM) Tools" 98 [I-D.ietf-opsawg-oam-overview]. 100 This document proposes a new set to OAM tools based on Bit Indexed 101 Explicit Replication [I-D.ietf-bier-architecture] (BIER) and more 102 specifically BIER Traffic Engineering [I-D.eckert-bier-te-arch] 103 (BIER-TE) to control the process or Replication and Elimination, and 104 provide traceability of these operations, in the DetNet dataplane. 105 An adjacency, which is represented by a bit in the BIER header, can 106 correspond in the dataplane to an Ethernet hop, a Label Switched 107 Path, or it can correspond to an IPv6 loose or strict source routed 108 path. 110 2. Terminology 112 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 113 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 114 document are to be interpreted as described in [RFC2119]. 116 3. On BIER - Traffic Engineering 118 BIER [I-D.ietf-bier-architecture] is a network plane replication 119 technique that was initially intended as a new method for multicast 120 distribution. In a nutshell, a BIER header includes a bitmap that 121 explicitly signals the listeners that are intended for a particular 122 packet, which means that 1) the sender is aware of the individual 123 listeners and 2) the BIER control plane is a simple extension of the 124 unicast routing as opposed to a dedicated multicast data plane, which 125 represents a considerable reduction in OPEX. For this reason, the 126 technology faces a lot of traction from Service Providers. 128 The simplicity of the BIER technology makes it very versatile as a 129 network plane signaling protocol. Already, a new Traffic Engineering 130 variation is emerging that uses bits to signal segments along a TE 131 path. While BIER is mainly a multicast technology that typically 132 leverages a unicast distributed control plane through IGP extensions, 133 BIER-TE [I-D.eckert-bier-te-arch] is mainly a unicast technology that 134 leverages a central computation to setup path, compute segments and 135 install the mapping in the intermediate nodes. 137 BIER-TE supports a Traffic Engineered forwarding plane by explicit 138 hop-by-hop forwarding and loose hop forwarding of packets. 140 From the BIER-TE architecture, the key differences over BIER are: 142 o BIER-TE replaces in-network autonomous path calculation by 143 explicit paths calculated off path by the BIER-TE controller host. 145 o In BIER-TE every BitPosition of the BitString of a BIER-TE packet 146 indicates one or more adjacencies - instead of a BFER as in BIER. 147 o BIER-TE in each BFR has no routing table but only a BIER-TE 148 Forwarding Table (BIFT) indexed by SI:BitPosition and populated 149 with only those adjacencies to which the BFR should replicate 150 packets to. 152 The generic view of an adjacency can be over a link, a tunnel or 153 along a path segment. 155 With Segment Routing [I-D.ietf-spring-segment-routing] a segment can 156 be signaled as an MPLS label, or an IPv6 routing header . A segment 157 may be loosely of strictly source routed, depending on the need for 158 full non-congruence and the confidence that loose routing may still 159 achieve that need. 161 4. BIER-TE-based Replication and Elimination Control 163 In a nutshell, BIER-TE is used as follows: 165 o A controller computes a complex path, sometimes called a track, 166 which takes the general form of a ladder. The steps and the side 167 rails between them are the adjacencies that can be activated on 168 demand on a per-packet basis using bits in the BIER header. 170 ===> (A) ====> (C) ==== 171 // ^ | ^ | \\ 172 ingress (I) | | | | (E) egress 173 \\ | v | v // 174 ===> (B) ====> (D) ==== 176 Figure 1: Ladder Shape with Replication and Elimination Points 178 o The controller assigns a BIER domain, and inside that domain, 179 assigns bits to the adjacencies. The controller assigns each bit 180 to a replication node that sends towards the adjacency, for 181 instance the ingress router into a segment that will insert a 182 routing header in the packet. A single bit may be used for a step 183 in the ladder, indicating the other end of the step in both 184 directions. 186 ===> (A) ====> (C) ==== 187 // 1 ^ | 4 ^ | 7 \\ 188 ingress (I) |2| |6| (E) egress 189 \\ 3 | v 5 | v 8 // 190 ===> (B) ====> (D) ==== 192 Figure 2: Assigning Bits 194 o The controller activates the replication by deciding the setting 195 of the bits associated with the adjacencies. This decision can be 196 modified at any time, but takes the latency of a controller round 197 trip to effectively take place. Below is an example that uses 198 Replication and Elimination to protect the A->C adjacency. 200 +-------+-----------+-------+---------------------+ 201 | Bit # | Adjacency | Owner | Example Bit Setting | 202 +-------+-----------+-------+---------------------+ 203 | 1 | I->A | I | 1 | 204 | 2 | A->B | A | 1 | 205 | | B->A | B | | 206 | 3 | I->C | I | 0 | 207 | 4 | A->C | A | 1 | 208 | 5 | B->D | B | 1 | 209 | 6 | C->D | C | 1 | 210 | | D->C | D | | 211 | 7 | C->E | C | 1 | 212 | 8 | D->E | D | 0 | 213 +-------+-----------+-------+---------------------+ 215 Replication and Elimination Protecting A->C 217 Table 1: Controlling Replication 219 o The BIER header with the controlling BitString is injected in the 220 packet by the ingress node of the deterministic path. That node 221 may act as a replication point, in which case it may issue 222 multiple copies of the packet 224 ====> Repl ===> Elim ==== 225 // | ^ \\ 226 ingress | | egress 227 v | 228 Fwd ====> Fwd 230 Figure 3: Enabled Adjacencies 232 o For each of its bits that is set in the BIER header, the owner 233 replication point resets the bit and transmits towards the 234 associated adjacency; to achieve this, the replication point 235 copies the packet and inserts the relevant data plane information, 236 such as a source route header, towards the adjacency that 237 corresponds to the bit 239 +-----------+----------------+ 240 | Adjacency | BIER BitString | 241 +-----------+----------------+ 242 | I->A | 01011110 | 243 | A->B | 00011110 | 244 | B->D | 00010110 | 245 | D->C | 00010010 | 246 | A->C | 01001110 | 247 +-----------+----------------+ 249 BitString in BIER Header as Packet Progresses 251 Table 2: BIER-TE in Action 253 o Adversely, an elimination node on the way strips the data plane 254 information and performs a bitwise AND on the BitStrings from the 255 various copies of the packet that it has received, before it 256 forwards the packet with the resulting BitString. 258 +-----------+----------------+ 259 | Operation | BIER BitString | 260 +-----------+----------------+ 261 | D->C | 00010010 | 262 | A->C | 01001110 | 263 | | -------- | 264 | AND in C | 00000010 | 265 | | | 266 | C->E | 00000000 | 267 +-----------+----------------+ 269 BitString Processing at Elimination Point C 271 Table 3: BIER-TE in Action (cont.) 273 o In this example, all the transmissions succeeded and the BitString 274 at arrival has all the bits reset - note that the egress may be an 275 Elimination Point in which case this is evaluated after this node 276 has performed its AND operation on the received BitStrings). 278 +-------------------+-----------------------+ 279 | Failing Adjacency | Egress BIER BitString | 280 +-------------------+-----------------------+ 281 | I->A | Frame Lost | 282 | I->B | Not Tried | 283 | A->C | 00010000 | 284 | A->B | 01001100 | 285 | B->D | 01001100 | 286 | D->C | 01001100 | 287 | C->E | Frame Lost | 288 | D->E | Not Tried | 289 +-------------------+-----------------------+ 291 BitString indicating failures 293 Table 4: BIER-TE in Action (cont.) 295 o But if a transmission failed along the way, one (or more) bit is 296 never cleared. Table 4 provides the possible outcomes of a 297 transmission. If the frame is lost, then it is probably due to a 298 failure in either I->A or C->E, and the controller should enable 299 I->B and D->E to find out. A BitString of 00010000 indicates 300 unequivocally a transmission error on the A->C adjacency, and a 301 BitString of 01001100 indicates a loss in either A->B, B->D or 302 D->C; enabling D->E on the next packets may provide more 303 information to sort things out. 305 In more details: 307 The BIER header is of variable size, and a DetNet network of a 308 limited size can use a model with 64 bits if 64 adjacencies are 309 enough, whereas a larger deployment may be able to signal up to 256 310 adjacencies for use in very complex paths. The format of this header 311 is common to BIER and BIER-TE. 313 For the DetNet data plane, a replication point is an ingress point 314 for more than one adjacency, and an elimination point is an egress 315 point for more than one adjacency. 317 A pre-populated state in a replication node indicates which bits are 318 served by this node and to which adjacency each of these bits 319 corresponds. With DetNet, the state is typically installed by a 320 controller entity such as a PCE. The way the adjacency is signaled 321 in the packet is fully abstracted in the bit representation and must 322 be provisioned to the replication nodes and maintained as a local 323 state, together with the timing or shaping information for the 324 associated flow. 326 The DetNet data plane uses BIER-TE to control which adjacencies are 327 used for a given packet. This is signaled from the path ingress, 328 which sets the appropriate bits in the BIER BitString to indicate 329 which replication must happen. 331 The replication point clears the bit associated to the adjacency 332 where the replica is placed, and the elimination points perform a 333 logical AND of the BitStrings of the copies that it gets before 334 forwarding. 336 As is apparent in the examples above, clearing the bits enables to 337 trace a packet to the replication points that made any particular 338 copy. BIER-TE also enables to detect the failing adjacencies or 339 sequences of adjacencies along a path and to activate additional 340 replications to counter balance the failures. 342 Finally, using the same BIER-TE bit for both directions of the steps 343 of the ladder enables to avoid replication in both directions along 344 the crossing adjacencies. At the time of sending along the step of 345 the ladder, the bit may have been already reset by performing the AND 346 operation with the copy from the other side, in which case the 347 transmission is not needed and does not occur (since the control bit 348 is now off). 350 5. Summary 352 BIER-TE occupies a particular position in the DetNet dataplane. In 353 the one hand it is optional, and only useful if replication and 354 elimination is taking place. In the other hand, it has unique 355 capabilities to: 357 o control which replication take place on a per packet basis, so 358 that replication points can be configured but not actually 359 utilized 360 o trace the replication activity and determine which node replicated 361 a particular packet 362 o measure the quality of transmission of the actual data packet 363 along the replication segments and use that in a control loop to 364 adapt the setting of the bits and maintain the reliability. 366 6. Implementation Status 368 A research-stage implementation of the forwarding plane fir a 6TiSCH 369 IOT use case was developed at Cisco's Paris Innovation Lab (PIRL) by 370 Zacharie Brodard. It was implemented on OpenWSN Open-source firmware 371 and tested on the OpenMote-CC2538 hardware. It implements the header 372 types 15,16, 17, 18 and 19 (bit-by-bit encoding without group ID) in 373 order to allow a BIER-TE protocol over IEE802.15.4e. 375 This work was complemented with a Controller-based control loop by 376 Hao Jiang. The controller builds the complex paths (called Tracks in 377 6TiSCH) and decides the setting oif the BitStrings in real time in 378 order to optimize the delivery ratio within a minimal energy budget. 380 Links: 382 github: https://github.com/zach-b/openwsn-fw/tree/BIER 383 OpenWSN firmware: https://openwsn.atlassian.net/wiki/pages/ 384 viewpage.action?pageId=688187 385 OpenMote hardware: http://www.openmote.com/ 387 7. Security considerations 389 TBD. 391 8. IANA Considerations 393 This document has no IANA considerations. 395 9. Acknowledgements 397 The method presented in this document was discussed and worked out 398 together with the DetNet Data Plane Design Team: 400 Jouni Korhonen 401 Janos Farkas 402 Norman Finn 403 Olivier Marce 404 Gregory Mirsky 405 Pascal Thubert 406 Zhuangyan Zhuang 408 The authors also like to thank the DetNet chairs Lou Berger and Pat 409 Thaler, as well as Thomas Watteyne, 6TiSCH co-chair, for their 410 contributions and support to this work. 412 10. References 414 10.1. Normative References 416 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 417 Requirement Levels", BCP 14, RFC 2119, 418 DOI 10.17487/RFC2119, March 1997, 419 . 421 10.2. Informative References 423 [I-D.dt-detnet-dp-alt] 424 Korhonen, J., Farkas, J., Mirsky, G., Thubert, P., 425 Zhuangyan, Z., and L. Berger, "DetNet Data Plane Protocol 426 and Solution Alternatives", draft-dt-detnet-dp-alt-04 427 (work in progress), September 2016. 429 [I-D.eckert-bier-te-arch] 430 Eckert, T., Cauchie, G., Braun, W., and M. Menth, "Traffic 431 Engineering for Bit Index Explicit Replication BIER-TE", 432 draft-eckert-bier-te-arch-06 (work in progress), November 433 2017. 435 [I-D.ietf-bier-architecture] 436 Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and 437 S. Aldrin, "Multicast using Bit Index Explicit 438 Replication", draft-ietf-bier-architecture-08 (work in 439 progress), September 2017. 441 [I-D.ietf-detnet-architecture] 442 Finn, N., Thubert, P., Varga, B., and J. Farkas, 443 "Deterministic Networking Architecture", draft-ietf- 444 detnet-architecture-04 (work in progress), October 2017. 446 [I-D.ietf-detnet-problem-statement] 447 Finn, N. and P. Thubert, "Deterministic Networking Problem 448 Statement", draft-ietf-detnet-problem-statement-02 (work 449 in progress), September 2017. 451 [I-D.ietf-detnet-use-cases] 452 Grossman, E., Gunther, C., Thubert, P., Wetterwald, P., 453 Raymond, J., Korhonen, J., Kaneko, Y., Das, S., Zha, Y., 454 Varga, B., Farkas, J., Goetz, F., Schmitt, J., Vilajosana, 455 X., Mahmoodi, T., Spirou, S., Vizarreta, P., Huang, D., 456 Geng, X., Dujovne, D., and M. Seewald, "Deterministic 457 Networking Use Cases", draft-ietf-detnet-use-cases-13 458 (work in progress), September 2017. 460 [I-D.ietf-opsawg-oam-overview] 461 Mizrahi, T., Sprecher, N., Bellagamba, E., and Y. 462 Weingarten, "An Overview of Operations, Administration, 463 and Maintenance (OAM) Tools", draft-ietf-opsawg-oam- 464 overview-16 (work in progress), March 2014. 466 [I-D.ietf-spring-segment-routing] 467 Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B., 468 Litkowski, S., and R. Shakir, "Segment Routing 469 Architecture", draft-ietf-spring-segment-routing-14 (work 470 in progress), December 2017. 472 Authors' Addresses 474 Pascal Thubert (editor) 475 Cisco Systems 476 Village d'Entreprises Green Side 477 400, Avenue de Roumanille 478 Batiment T3 479 Biot - Sophia Antipolis 06410 480 FRANCE 482 Phone: +33 4 97 23 26 34 483 Email: pthubert@cisco.com 485 Zacharie Brodard 486 Ecole Polytechnique 487 Route de Saclay 488 Palaiseau 91128 489 FRANCE 491 Phone: +33 6 73 73 35 09 492 Email: zacharie.brodard@polytechnique.edu 494 Hao Jiang 495 Telecom Bretagne 496 2, rue de la Chataigneraie 497 Cesson-Sevigne 35510 498 FRANCE 500 Phone: +33 7 53 70 97 34 501 Email: hao.jiang@telecom-bretagne.eu