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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Missing Reference: 'PCE' is mentioned on line 633, but not defined == Outdated reference: A later version (-30) exists of draft-ietf-6tisch-architecture-28 == Outdated reference: A later version (-05) exists of draft-thubert-raw-technologies-04 == Outdated reference: A later version (-04) exists of draft-bernardos-raw-use-cases-03 -- Obsolete informational reference (is this intentional?): RFC 3272 (ref. 'TE') (Obsoleted by RFC 9522) == Outdated reference: A later version (-03) exists of draft-mirsky-detnet-ip-oam-02 Summary: 0 errors (**), 0 flaws (~~), 8 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 RAW P. Thubert, Ed. 3 Internet-Draft Cisco Systems 4 Intended status: Informational G.Z. Papadopoulos 5 Expires: 26 November 2020 IMT Atlantique 6 R. Buddenberg 7 25 May 2020 9 Reliable and Available Wireless Architecture/Framework 10 draft-pthubert-raw-architecture-03 12 Abstract 14 Due to uncontrolled interferences, including the self-induced 15 multipath fading, deterministic networking can only be approached on 16 wireless links. The radio conditions may change -way- faster than a 17 centralized routing can adapt and reprogram, in particular when the 18 controller is distant and connectivity is slow and limited. RAW 19 separates the routing time scale at which a complex path is 20 recomputed from the forwarding time scale at which the forwarding 21 decision is taken for an individual packet. RAW operates at the 22 forwarding time scale. The RAW problem is to decide, within the 23 redundant solutions that are proposed by the routing, which will be 24 used for each individual packet to provide a DetNet service while 25 minimizing the waste of resources. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at https://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on 26 November 2020. 44 Copyright Notice 46 Copyright (c) 2020 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 51 license-info) in effect on the date of publication of this document. 52 Please review these documents carefully, as they describe your rights 53 and restrictions with respect to this document. Code Components 54 extracted from this document must include Simplified BSD License text 55 as described in Section 4.e of the Trust Legal Provisions and are 56 provided without warranty as described in the Simplified BSD License. 58 Table of Contents 60 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 61 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 62 3. Related Work at The IETF . . . . . . . . . . . . . . . . . . 6 63 4. Use Cases and Requirements Served . . . . . . . . . . . . . . 6 64 4.1. Radio Access Protection . . . . . . . . . . . . . . . . . 7 65 4.2. End-to-End Protection in a Wireless Mesh . . . . . . . . 8 66 5. RAW Considerations . . . . . . . . . . . . . . . . . . . . . 8 67 5.1. Reliability and Availability . . . . . . . . . . . . . . 8 68 5.1.1. High Availability Engineering Principles . . . . . . 8 69 5.1.2. Applying Reliability Concepts to Networking . . . . . 11 70 5.1.3. Reliability in the Context of RAW . . . . . . . . . . 11 71 5.2. RAW Scope and Prerequisites . . . . . . . . . . . . . . . 13 72 5.3. Routing Time Scale vs. Forwarding Time Scale . . . . . . 14 73 6. RAW Architecture Elements . . . . . . . . . . . . . . . . . . 15 74 6.1. Wireless Tracks . . . . . . . . . . . . . . . . . . . . . 15 75 6.2. PAREO Functions . . . . . . . . . . . . . . . . . . . . . 16 76 6.2.1. Packet Replication . . . . . . . . . . . . . . . . . 17 77 6.2.2. Packet Elimination . . . . . . . . . . . . . . . . . 18 78 6.2.3. Promiscuous Overhearing . . . . . . . . . . . . . . . 18 79 6.2.4. Constructive Interference . . . . . . . . . . . . . . 18 80 7. RAW Architecture . . . . . . . . . . . . . . . . . . . . . . 19 81 7.1. PCE vs. PSE . . . . . . . . . . . . . . . . . . . . . . . 20 82 7.2. RAW OAM . . . . . . . . . . . . . . . . . . . . . . . . . 21 83 7.3. Source-Routed vs. Distributed Forwarding Decision . . . . 22 84 7.4. Flow Identification . . . . . . . . . . . . . . . . . . . 23 85 8. Security Considerations . . . . . . . . . . . . . . . . . . . 24 86 8.1. Forced Access . . . . . . . . . . . . . . . . . . . . . . 24 87 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 88 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 24 89 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24 90 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 24 91 12.1. Normative References . . . . . . . . . . . . . . . . . . 24 92 12.2. Informative References . . . . . . . . . . . . . . . . . 26 93 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 95 1. Introduction 97 Bringing determinism in a packet network means eliminating the 98 statistical effects of multiplexing that result in probabilistic 99 jitter and loss. This can be approached with a tight control of the 100 physical resources to maintain the amount of traffic within a 101 budgetted volume of data per unit of time that fits the physical 102 capabilities of the underlying technology, and the use of time-shared 103 resources (bandwidth and buffers) per circuit, and/or by shaping and/ 104 or scheduling the packets at every hop. 106 Wireless networks operate on a shared medium where uncontrolled 107 interference, including the self-induced multipath fading, adds 108 another dimension to the statistical effects that affect the 109 delivery. Scheduling transmissions can alleviate those effects by 110 leveraging diversity in the spatial, time, code, and frequency 111 domains, and provide a Reliable and Available Wireless (RAW) service 112 while preserving energy and optimizing the use of the shared 113 spectrum. 115 Deterministic Networking is an attempt to mostly eliminate packet 116 loss for a committed bandwidth with a guaranteed worst-case end-to- 117 end latency, even when co-existing with best-effort traffic in a 118 shared network. This innovation is enabled by recent developments in 119 technologies including IEEE 802.1 TSN (for Ethernet LANs) and IETF 120 DetNet (for wired IP networks). It is getting traction in various 121 industries including manufacturing, online gaming, professional A/V, 122 cellular radio and others, making possible many cost and performance 123 optimizations. 125 The "Deterministic Networking Architecture" [RFC8655] is composed of 126 three planes: the Application (User) Plane, the Controller Plane, and 127 the Network Plane. RAW extends DetNet to focus on issues that are 128 mostly a concern on wireless links, and inherits the architecture and 129 the planes. A RAW Network Plane is thus a Network Plane inherited by 130 RAW from DetNet, composed of one or multiple hops of homogeneous or 131 heterogeneous technologies, e.g. a Wi-Fi6 Mesh or one-hop CBRS access 132 links federated by a 5G backhaul. 134 RAW networking aims at providing highly available and reliable end- 135 to-end performances in a network with scheduled wireless segments. 136 Uncontrolled interference and transmission obstacles may impede the 137 transmission, and techniques such as beamforming with Multi-User MIMO 138 can only alleviate some of those issues, so the term "deterministic" 139 is usually not associated with short range radios, in particular in 140 the ISM band. This uncertainty places limits to the amount of 141 traffic that can be transmitted on a link while conforming to a RAW 142 Service Level Agreement (SLA) that may vary rapidly. 144 The wireless and wired media are fundamentally different at the 145 physical level, and while the generic "Deterministic Networking 146 Problem Statement" [RFC8557] applies to both the wired and the 147 wireless media, the methods to achieve RAW must extend those used to 148 support time-sensitive networking over wires, as a RAW solution has 149 to address less consistent transmissions, energy conservation and 150 shared spectrum efficiency. 152 The development of RAW technologies has been lagging behind 153 deterministic efforts for wired systems both at the IEEE and the 154 IETF. But recent efforts at the IEEE and 3GPP indicate that wireless 155 is finally catching up at the lower layer and that it is now possible 156 for the IETF to extend DetNet for wireless segments that are capable 157 of scheduled wireless transmissions. 159 The intent for RAW is to provide DetNet elements that are specialized 160 for short range radios. From this inheritance, RAW stays agnostic to 161 the radio layer underneath though the capability to schedule 162 transmissions is assumed. How the PHY is programmed to do so, and 163 whether the radio is single-hop or meshed, are unknown at the IP 164 layer and not part of the RAW abstraction. 166 The establishment of a path is not in-scope for RAW. It may be the 167 product of a centralized Controller Plane as described for DetNet. 168 As opposed to wired networks, the action of installing a path over a 169 set of wireless links may be very slow relative to the speed at which 170 the radio conditions vary, and it makes sense in the wireless case to 171 provide redundant forwarding solutions along a complex path and to 172 leave it to the Network Plane to select which of those forwarding 173 solutions are to be used for a given packet based on the current 174 conditions. 176 RAW distinguishes the longer time scale at which routes are computed 177 from the the shorter forwarding time scale where per-packet decisions 178 are made. RAW operates within the Network Plane at the forwarding 179 time scale on one DetNet flow over a complex path called a Track. 180 The Track is preestablished and installed by means outside of the 181 scope of RAW; it may be strict or loose depending on whether each or 182 just a subset of the hops are observed and controlled by RAW. 184 The scope of the RAW WG comprises Network plane protocol elements 185 such as Operations, Administration and Maintenance (OAM) to observe 186 some or all hops along a Track, as well as the end-to-end packet 187 delivery, and in-band control to optimize the use of redundancy to 188 achieve the required SLA. 190 2. Terminology 192 RAW reuses terminology defined for DetNet in the "Deterministic 193 Networking Architecture" [RFC8655], e.g., PREOF for Packet 194 Replication, Elimination and Ordering Functions. 196 RAW also reuses terminology defined for 6TiSCH in [6TiSCH-ARCHI] such 197 as the term Track. A Track as a complex path with associated PAREO 198 operations. The concept is abstract to the underlaying technology 199 and applies to any fully or partially wireless mesh, including, e.g., 200 a Wi-Fi mesh. RAW specifies strict and loose Tracks depending on 201 whether the path is fully controlled by RAW or traverses an opaque 202 network where RAW cannot observe and control the individual hops. 204 RAW uses the term OAM as defined in [RFC6291]. 206 RAW defines the following terms: 208 PAREO: Packet (hybrid) ARQ, Replication, Elimination and Ordering. 209 PAREO is a superset Of DetNet's PREOF that includes radio-specific 210 techniques such as short range broadcast, MUMIMO, constructive 211 interference and overhearing, which can be leveraged separately or 212 combined to increase the reliability. 214 Flapping: In the context of RAW, a link flaps when the reliability 215 of the wireless connectivity drops abruptly for a short period of 216 time, typically of a subsecond to seconds duration. 218 In the context of the RAW work, Reliability and Availability are 219 defined as follows: 221 Reliability: Reliability is a measure of the probability that an 222 item will perform its intended function for a specified interval 223 under stated conditions. For RAW, the service that is expected is 224 delivery within a bounded latency and a failure is when the packet 225 is either lost or delivered too late. RAW expresses reliability 226 in terms of Mean Time Between Failure (MTBF) and Maximum 227 Consecutive Failures (MCF). More in [NASA]. 229 Availability: Availability is a measure of the relative amount of 230 time where a path operates in stated condition, in other words 231 (uptime)/(uptime+downtime). Because a serial wireless path may 232 not be good enough to provide the required availability, and even 233 2 parallel paths may not be over a longer period of time, the RAW 234 availability implies a path that is a lot more complex than what 235 DetNet typically envisages (a Track). 237 3. Related Work at The IETF 239 RAW intersects with protocols or practices in development at the IETF 240 as follows: 242 * The Dynamic Link Exchange Protocol (DLEP) [RFC8175] from [MANET] 243 can be leveraged at each hop to derive generic radio metrics 244 (e.g., based on LQI, RSSI, queueing delays and ETX) on individual 245 hops. 247 * OAM work at [detnet] such as [DetNet-IP-OAM] for the case of the 248 IP Data Plane observes the state of DetNet paths, typically MPLS 249 and IPv6 pseudowires [DetNet-DP-FW], in the direction of the 250 traffic. RAW needs feedback that flows on the reverse path and 251 gathers instantaneous values from the radio receivers at each hop 252 to inform back the source and replicating relays so they can make 253 optimized forwarding decisions. The work named ICAN may be 254 related as well. 256 * [BFD] detect faults in the path between an ingress and an egress 257 forwarding engines, but is unaware of the complexity of a path 258 with replication, and expects bidirectionality. BFD considers 259 delivery as success whereas with RAW the bounded latency can be as 260 important as the delivery itself. 262 * [SPRING] and [BIER] define in-band signaling that influences the 263 routing when decided at the head-end on the path. There's already 264 one RAW-related draft at BIER [BIER-PREF] more may follow. RAW 265 will need new in-band signaling when the decision is distributed, 266 e.g., required chances of reliable delivery to destination within 267 latency. This signaling enables relays to tune retries and 268 replication to meet the required SLA. 270 * [CCAMP] defines protocol-independent metrics and parameters 271 (measurement attributes) for describing links and paths that are 272 required for routing and signaling in technology-specific 273 networks. RAW would be a source of requirements for CCAMP to 274 define metrics that are significant to the focus radios. 276 4. Use Cases and Requirements Served 278 In order to focus on real-worlds issues and assert the feasibility of 279 the proposed capabilities, RAW focuses on selected technologies that 280 can be scheduled at the lower layers: IEEE Std. 802.15.4 timeslotted 281 channel hopping (TSCH), 3GPP 5G ultra-reliable low latency 282 communications (URLLC), IEEE 802.11ax/be where 802.11be is extreme 283 high throughput (EHT), and L-band Digital Aeronautical Communications 284 System (LDACS). See [RAW-TECHNOS] for more. 286 "Deterministic Networking Use Cases" [RFC8578] presents a number of 287 wireless use cases including Wireless, such as application to 288 Industrial Applications, Pro-Audio, and SmartGrid Automation. 289 [RAW-USE-CASES] adds a number of use cases that demonstrate the need 290 for RAW capabilities for new applications such as Pro-Gaming and 291 drones. The use cases can be abstracted in two families, Loose 292 Protection, e.g., protecting the first hop in Radio Access Protection 293 and Strict Protection, e.g., providing End-to-End Protection in a 294 wireless mesh. 296 4.1. Radio Access Protection 298 To maintain the required SLA at all times, a wireless Host may use 299 more than one Radio Access Network (RAN) in parallel. 301 ... .. 302 RAN 1 ----- ... .. ... 303 / . .. .... 304 +--------+ / . .... +-----------+ 305 |Wireless|- . ..... | Service | 306 | Device |-***-- RAN 2 -- . Internet ....---| / | 307 |(STA/UE)|- .. ..... |Application| 308 +--------+ $$$ . ....... +-----------+ 309 \ ... ... ..... 310 RAN n -------- ... ..... 312 *** = flapping at this time $$$ expensive 314 Figure 1: Radio Access Protection 316 The RANs may be heterogeneous, e.g., 3GPP 5G [RAW-5G] and Wi-Fi 317 [RAW-TECHNOS] for high-speed communication, in which case a Layer-3 318 abstraction becomes useful to select which of the RANs are used at a 319 particular point of time, and the amount of traffic that is 320 distributed over each RAN. 322 The idea is that the rest of the path to the destination(s) is 323 protected separately (e.g., uses non-congruent paths, leverages 324 DetNet / TSN, etc...) and is a lot more reliable, e.g., wired. In 325 that case, RAW observes the reliability of the end-to-end operation 326 through each of the RANs but only observes and controls the wireless 327 operation the first hop. 329 A variation of that use case has a pair of wireless Hosts connected 330 over a wired core / backbone network. In that case, RAW observes and 331 controls the ingress and egress RANs, while neglecting the hops in 332 the core. The resulting loose Track may be instanciated, e.g., using 333 tunneling or loose source routing between the RANs. 335 4.2. End-to-End Protection in a Wireless Mesh 337 In radio technologies that support mesh networking (e.g., Wi-Fi and 338 TSCH), a Track is a complex path with distributed PAREO capabilities. 339 In that case, RAW operates through the multipath and makes decisions 340 either at the Ingress or at every hop (more in Section 6.1). 342 A-------B-------C-----D 343 / \ / / \ 344 Ingress ----M-------N--zzzzz--- Egress 345 \ \ / / 346 P--zzz--Q-------------R 348 zzz = flapping now 350 Figure 2: End-to-End Protection 352 The Protection may be imposed by the source based on end-to-end OAM, 353 or performed hop-by-hop, in which case the OAM must enables the 354 intermediate Nodes to estimate the quality of the rest of the 355 feasible paths in the remainder of the Track to the destination. 357 5. RAW Considerations 359 5.1. Reliability and Availability 361 5.1.1. High Availability Engineering Principles 363 The reliability criteria of a critical system pervade through its 364 elements, and if the system comprises a data network then the data 365 network is also subject to the inherited reliability and availability 366 criteria. It is only natural to consider the art of high 367 availability engineering and apply it to wireless communicaitons in 368 the context of RAW. 370 There are three principles [pillars] of high availability 371 engineering: 373 1. elimination of single points of failure 374 2. reliable crossover 375 3. prompt detection of failures as they occur. 377 These principles are common to all high availability systems, not 378 just ones with Internet technology at the center. Examples of both 379 non-Internet and Internet are included. 381 5.1.1.1. Elimination of Single Points of Failure 383 Physical and logical components in a system happen to fail, either as 384 the effect of wear and tear, when used beyond acceptable limits, or 385 due to a software bug. It is necessary to decouple component failure 386 from system failure to avoid the latter. This allows failed 387 components to be restored while the rest of the system continues to 388 function. 390 IP Routers leverage routing protocols to compute alternate routes in 391 case of a failure. There is a rather open-ended issue over alternate 392 routes -- for example, when links are cabled through the same 393 conduit, they form a shared risk link group (SRLG), and will share 394 the same fate if the bundle is cut. The same effect can happen with 395 virtual links that end up in a same physical transport through the 396 games of encapsulation. In a same fashion, an interferer or an 397 obstacle may affect multiple wireless transmissions at the same time, 398 even between different sets of peers. 400 Intermediate network Nodes such as routers, switches and APs, wire 401 bundles and the air medium itself can become single points of 402 failure. For High Availability, it is thus required to use 403 physically link- and Node-disjoint paths; in the wireless space, it 404 is also required to use the highest possible degree of diversity in 405 the transmissions over the air to combat the additional causes of 406 transmission loss. 408 From an economics standpoint, executing this principle properly 409 generally increases capitalization expense because of the redundant 410 equipment. In a constrained network where the waste of energy and 411 bandwidth should be minimized, an excessive use of redundant links 412 must be avoided; for RAW this means that the extra bandwidth must be 413 used wisely and with parcimony. 415 5.1.1.2. Reliable Crossover 417 Having a backup equipment has a limited value unless it can be 418 reliably switched into use within the down-time parameters. IP 419 Routers execute reliable crossover continuously because the routers 420 will use any alternate routes that are available [RFC0791]. This is 421 due to the stateless nature of IP datagrams and the dissociation of 422 the datagrams from the forwarding routes they take. The "IP Fast 423 Reroute Framework" [FRR] analyzes mechanisms for fast failure 424 detection and path repair for IP Fast-Reroute, and discusses the case 425 of multiple failures and SRLG. Examples of FRR techniques include 426 Remote Loop-Free Alternate [RLFA-FRR] and backup label-switched path 427 (LSP) tunnels for the local repair of LSP tunnels using RSVP-TE 428 [RFC4090]. 430 Deterministic flows, on the contrary, are attached to specific paths 431 where dedicated resources are reserved for each flow. This is why 432 each DetNet path must inherently provide sufficient redundancy to 433 provide the guaranteed SLA at all times. The DetNet PREOF typically 434 leverages 1+1 redundancy whereby a packet is sent twice, over non- 435 congruent paths. This avoids the gap during the fast reroute 436 operation, but doubles the traffic in the network. 438 In the case of RAW, the expectation is that multiple transient faults 439 may happen in overlapping time windows, in which case the 1+1 440 redundancy with delayed reestablishment of the second path will not 441 provide the required guarantees. The Data Plane must be configured 442 with a sufficient degree of redundancy to select an alternate 443 redundant path immediately upon a fault, without the need for a slow 444 intervention from the controller plane. 446 5.1.1.3. Prompt Notification of Failures 448 The execution of the two above principles is likely to render a 449 system where the user will rarely see a failure. But someone needs 450 to in order to direct maintenance. 452 There are many reasons for system monitoring (FCAPS for fault, 453 configuration, accounting, performance, security is a handy mental 454 checklist) but fault monitoring is sufficient reason. 456 "An Architecture for Describing Simple Network Management Protocol 457 (SNMP) Management Frameworks" [STD 62] describes how to use SNMP to 458 observe and correct long-term faults. 460 "Overview and Principles of Internet Traffic Engineering" [TE] 461 discusses the importance of measurement for network protection, and 462 provides abstract an method for network survivability with the 463 analysis of a traffic matrix as observed by SNMP, probing techniques, 464 FTP, IGP link state advertisements, and more. 466 Those measurements are needed in the context of RAW to inform the 467 controller and make the long term reactive decision to rebuild a 468 complex path. But RAW itself operates in the Network Plane at a 469 faster time scale. To act on the Data Plane, RAW needs live 470 information from the Operational Plane , e.g., using Bidirectional 471 Forwarding Detection [BFD] and its variants (bidirectional and remote 472 BFD) to protect a link, and OAM techniques to protect a path. 474 5.1.2. Applying Reliability Concepts to Networking 476 The terms Reliaility and Availability are defined for use in RAW in 477 Section 2 and the reader is invited to read [NASA] for more details 478 on the general definition of Reliability. Practically speaking a 479 number of nines is often used to indicate the reliability of a data 480 link, e.g., 5 nines indicate a Packet Delivery Ratio (PDR) of 481 99.999%. 483 This number is typical in a wired environment where the loss is due 484 to a random event such as a solar particle that affects the 485 transmission of a particular frame, but does not affect the previous 486 or next frame, nor frames transmitted on other links. Note that the 487 QoS requirements in RAW may include a bounded latency, and a packet 488 that arrives too late is a fault and not considered as delivered. 490 For a periodic networking pattern such as an automation control loop, 491 this number is proportional to the Mean Time Between Failures (MTBF). 492 When a single fault can have dramatic consequences, the MTBF 493 expresses the chances that the unwanted fault event occurs. In data 494 networks, this is rarely the case. Packet loss cannot never be fully 495 avoided and the systems are built to resist to one loss, e.g., using 496 redundancy with Retries (HARQ) or Packet Replication and Elimination 497 (PRE), or, in a typical control loop, by linear interpolation from 498 the previous measuremnents. 500 But the linear interpolation method can not resist multiple 501 consecutive losses, and a high MTBF is desired as a guarantee that 502 this will not happen, IOW that the number of losses-in-a-row can be 503 bounded. In that case, what is really desired is a Maximum 504 Consecutive Failures (MCF). If the number of losses in a row passes 505 the MCF, the control loop has to abort and the system, e.g., the 506 production line, may need to enter an emergency stop condition. 508 Engineers that build automated processes may use the network 509 reliability expressed in nines or as an MTBF as a proxy to indicate 510 an MCF, e.g., as described in section 7.4 of the "Deterministic 511 Networking Use Cases" [RFC8578]. 513 5.1.3. Reliability in the Context of RAW 515 In contrast with wired networks, errors in transmission are the 516 predominent source of packet loss in wireless networks. 518 The root cause for the loss may be of multiple origins, calling for 519 the use of different forms of diversity: 521 Multipath Fading: A destructive interference by a reflection of the 522 original signal. 524 A radio signal may be received directly (line-of-sight) and/or as 525 a reflection on a physical structure (echo). The reflections take 526 a longer path and are delayed by the extra distance divided by the 527 speed of light in the medium. Depending on the frequency, the 528 echo lands with a different phase which may add up to 529 (constructive interference) or cancel the direct signal 530 (destructive interference). 532 The affected frequencies depend on the relative position of the 533 sender, the receiver, and all the reflecting objects in the 534 environment. A given hop will suffer from multipath fading for 535 multiple packets in a row till the something moves that changes 536 the reflection patterns. 538 Co-channel Interference: Energy in the spectrum used for the 539 transmission confuses the receiver. 541 The wireless medium itself is a Shared Risk Link Group (SRLG) for 542 nearby users of the same spectrum, as an interference may affect 543 multiple co-channel transmissions between different peers within 544 the interference domain of the interferer, possibly even when they 545 use different technologies. 547 Obstacle in Fresnel Zone: The optimal transmission happens when the 548 Fresnel Zone between the sender and the receiver is free of 549 obstacles. 551 As long as a physical object (e.g., a metallic trolley between 552 peers) that affects the transmission is not removed, the quality 553 of the link is affected. 555 In an environment that is rich of metallic structures and mobile 556 objects, a single radio link will provide a fuzzy service, meaning 557 that it cannot be trusted to transport the traffic reliably over a 558 long period of time. 560 Transmission losses are typically not independent, and their nature 561 and duration are unpredictable; as long as a physical object (e.g., a 562 metallic trolley between peers) that affects the transmission is not 563 removed, or as long as the interferer (e.g., a radar) keeps 564 transmitting, a continuous stream of packets will be affected. 566 The key technique to combat those unpredictable losses is diversity. 567 Different forms of diversity are necessary to combat different causes 568 of loss and the use of diversity must be maximised to optimize the 569 PDR. 571 A single packet may be sent at different times (time diversity) over 572 diverse paths (spatial diversity) that rely on diverse radio channels 573 (frequency diversity) and diverse PHY technologies, e.g., narrowband 574 vs. spread spectrum, or diverse codes. Using time diversity will 575 defeat short-term interferences; spatial diversity combats very local 576 causes such as multipath fading; narrowband and spread spectrum are 577 relatively innocuous to one another and can be used for diversity in 578 the presence of the other. 580 5.2. RAW Scope and Prerequisites 582 A prerequisite to the RAW work is that an end-to-end routing function 583 computes a complex sub-topology along which forwarding can happen 584 between a source and one or more destinations. The concept of Track 585 is specified in the 6TiSCH Architecture [6TiSCH-ARCHI] to represent 586 that complex sub-topology. Tracks provide a high degree of 587 redundancy and diversity and enable the DetNet PREOF, network coding, 588 and possibly RAW specific techniques such as PAREO, leveraging 589 frequency diversity, time diversity, and possibly other forms of 590 diversity as well. 592 How the routing operation (e.g., PCE) in the Controlloer Plane 593 computes the Track is out of scope for RAW. The scope of the RAW 594 operation is one Track, and the goal of the RAW operation is to 595 optimize the use of the Track at the forwarding timescale to maintain 596 the expected SLA while optimizing the usage of constrained resources 597 such as energy and spectrum. 599 Another prerequisite is that an IP link can be established over the 600 radio with some guarantees in terms of service reliability, e.g., it 601 can be relied upon to transmit a packet within a bounded latency and 602 provides a guaranteed BER/PDR outside rare but existing transient 603 outage windows that can last from split seconds to minutes. The 604 radio layer can be programmed with abstract parameters, and can 605 return an abstract view of the state of the Link to help the Network 606 Layer forwarding decision (think DLEP from MANET). 608 How the radio interface manages its lower layers is out of control 609 and out of scope for RAW. In the same fashion, the non-RAW portion 610 along a loose Track is by definition out of control and out of scope 611 for RAW. Whether it is a single hop or a mesh is also unknown and 612 out of scope. 614 5.3. Routing Time Scale vs. Forwarding Time Scale 616 With DetNet, the Controller Plane Function that handles the routing 617 computation and maintenance (the PCE) can be centralized and can 618 reside outside the network. In a wireless mesh, the path to the PCE 619 can be expensive and slow, possibly going across the whole mesh and 620 back. Reaching to the PCE can also be slow in regards to the speed 621 of events that affect the forwarding operation at the radio layer. 623 Due to that cost and latency, the Controller Plane is not expected to 624 be sensitive/reactive to transient changes. The abstraction of a 625 link at the routing level is expected to use statistical metrics that 626 aggregate the behavior of a link over long periods of time, and 627 represent its properties as shades of gray as opposed to numerical 628 values such as a link quality indicator, or a boolean value for 629 either up or down. 631 +----------------+ 632 | Controller | 633 | [PCE] | 634 +----------------+ 635 ^ 636 | 637 Slow 638 | 639 _-._-._-._-._-._-. | ._-._-._-._-._-._-._-._-._-._-._-._- 640 _-._-._-._-._-._-._-. | _-._-._-._-._-._-._-._-._-._-._-._- 641 | 642 Expensive 643 | 644 .... | ....... 645 .... . | . ....... 646 .... v ... 647 .. A-------B-------C---D .. 648 ... / \ / / \ .. 649 . I ----M-------N--***-- E .. 650 .. \ \ / / ... 651 .. P--***--Q----------R .... 652 .. .... 653 . <----- Fast -------> .... 654 ....... .... 655 ................. 657 *** = flapping at this time 659 Figure 3: Time Scales 661 In the case of wireless, the changes that affect the forwarding 662 decision can happen frequently and often for short durations, e.g., a 663 mobile object moves between a transmitter and a receiver, and will 664 cancel the line of sight transmission for a few seconds, or a radar 665 measures the depth of a pool and interferes on a particular channel 666 for a split second. 668 There is thus a desire to separate the long term computation of the 669 route and the short term forwarding decision. In that model, the 670 routing operation computes a complex Track that enables multiple Non- 671 Equal Cost Multi-Path (N-ECMP) forwarding solutions, and leaves it to 672 the Data Plane to make the per-packet decision of which of these 673 possibilities should be used. 675 In the wired world, and more specifically in the context of Traffic 676 Engineering (TE), an alternate path can be used upon the detection of 677 a failure in the main path, e.g., using OAM in MPLS-TP or BFD over a 678 collection of SD-WAN tunnels. RAW formalizes a forwarding time scale 679 that is an order(s) of magnitude shorter than the controller plane 680 routing time scale, and separates the protocols and metrics that are 681 used at both scales. Routing can operate on long term statistics 682 such as delivery ratio over minutes to hours, but as a first 683 approximation can ignore flapping. On the other hand, the RAW 684 forwarding decision is made at the scale of the packet rate, and uses 685 information that must be pertinent at the present time for the 686 current transmission(s). 688 6. RAW Architecture Elements 690 A RAW Network Plane may be strict or loose, depending on whether RAW 691 observes and takes actions on all hops or not. For instance, the 692 packets between two wireless entities may be relayed over a wired 693 infrastructure such as a Wi-Fi extended service set (ESS) or a 5G 694 Core; in that case, RAW observes and control the transmission over 695 the wireless first and last hops, as well as end-to-end metrics such 696 as latency, jitter, and delivery ratio. This operation is loose 697 since the structure and properties of the wired infrastructure are 698 ignored, and may be either controlled by other means such as DetNet/ 699 TSN, or neglected in the face of the wireless hops. 701 6.1. Wireless Tracks 703 The "6TiSCH Architecture" [6TiSCH-ARCHI] introduces the concept of 704 Track a possibly complex path with the PAREO functions operated 705 within. RAW extends the concept to any wireless mesh technology, 706 including, e.g., Wi-Fi. 708 A simple Track is composed of a direct sequence of reserved hops to 709 ensure the transmission of a single packet from a source Node to a 710 destination Node across a multihop path. 712 A Complex Track is designed as a directed acyclic graph from a source 713 Node towards a destination Node to support multi-path forwarding. By 714 employing PRE functions [RFC8655], several paths may be computed, and 715 these paths may be more or less independent. For example, a complex 716 Track may branch off and rejoin over non-congruent paths (branches). 718 6.2. PAREO Functions 720 RAW may control whether and how to use packet replication and 721 elimination (PRE), Automatic Repeat reQuest (ARQ), Hybrid ARQ (HARQ) 722 that includes Forward Error Correction (FEC) and coding, and other 723 wireless-specific techniques such as overhearing and constructive 724 interferences, in order to increase the reliabiility and availability 725 of the end-to-end transmission. 727 Collectively, those function are called PAREO for Packet (hybrid) 728 ARQ, Replication, Elimination and Ordering. By tuning dynamically 729 the use of PAREO functions, RAW avoids the waste of critical 730 resources such as spectrum and energy while providing that the 731 guaranteed SLA, e.g., by adding redundancy only when a spike of loss 732 is observed. 734 In a nutshell, PAREO establishes several paths in a network to 735 provide redundancy and parallel transmissions to bound the end-to-end 736 delay to traverse the network. Optionally, promiscuous listening 737 between paths is possible, such that the Nodes on one path may 738 overhear transmissions along the other path. Considering the 739 scenario shown in Figure 4, many different paths are possible for S 740 to reach R. A simple way to benefit from this topology could be to 741 use the two independent paths via Nodes A, C, E and via B, D, F. But 742 more complex paths are possible by interleaving transmissions from 743 the lower level of the path to the upper level. 745 (A) -- (C) -- (E) 746 / \ 747 ingress | | | egress 748 \ / 749 (B) -- (D) -- (F) 751 Figure 4: A Ladder Shape with Two Parallel Paths 753 PAREO may also take advantage of the shared properties of the 754 wireless medium to compensate for the potential loss that is incurred 755 with radio transmissions. 757 For instance, when the source sends to Node A, Node B may listen 758 promiscuously and get a second chance to receive the frame without an 759 additional transmission. Note that B would not have to listen if it 760 already received that particular frame at an earlier timeslot in a 761 dedicated transmission towards B. 763 The PAREO model can be implemented in both centralized and 764 distributed scheduling approaches. In the centralized approach, a 765 Path Computation Element (PCE) scheduler calculates a Track and 766 schedules the communication. In the distributed approach, the Track 767 is computed within the network, and signaled in the packets, e.g., 768 using BIER-TE, Segment Routing, or a Source Routing Header. 770 6.2.1. Packet Replication 772 By employing a Packet Replication procedure, a Node forwards a copy 773 of each data packet to more than one successor. To do so, each Node 774 (i.e., ingress and intermediate Node) sends the data packet multiple 775 times as separate unicast transmissions. For instance, in Figure 5, 776 the ingress Node is transmitting the packet to both successors, nodes 777 A and B, at two different times. 779 ===> (A) => (C) => (E) === 780 // \\// \\// \\ 781 ingress //\\ //\\ egress 782 \\ // \\ // \\ // 783 ===> (B) => (D) => (F) === 785 Figure 5: Packet Replication 787 An example schedule is shown in Table 1. This way, the transmission 788 leverages with the time and spatial forms of diversity. 790 +---------+------+------+------+------+------+------+------+ 791 | Channel | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 792 +=========+======+======+======+======+======+======+======+ 793 | 0 | S->A | S->B | B->C | B->D | C->F | E->R | F->R | 794 +---------+------+------+------+------+------+------+------+ 795 | 1 | | A->C | A->D | C->E | D->E | D->F | | 796 +---------+------+------+------+------+------+------+------+ 798 Table 1: Packet Replication: Sample schedule 800 6.2.2. Packet Elimination 802 The replication operation increases the traffic load in the network, 803 due to packet duplications. This may occur at several stages inside 804 the Track, and to avoid an explosion of the number of copies, a 805 Packet Elimination procedure must be applied as well. To this aim, 806 once a Node receives the first copy of a data packet, it discards the 807 subsequent copies. 809 The logical functions of Replication and Elimination may be 810 collocated in an intermediate Node, the Node first eliminating the 811 redundant copies and then sending the packet exactly once to each of 812 the selected successors. 814 6.2.3. Promiscuous Overhearing 816 Considering that the wireless medium is broadcast by nature, any 817 neighbor of a transmitter may overhear a transmission. By employing 818 the Promiscuous Overhearing operation, the next hops have additional 819 opportunities to capture the data packets. In Figure 6, when Node A 820 is transmitting to its DP (Node C), the AP (Node D) and its sibling 821 (Node B) may decode this data packet as well. As a result, by 822 employing corellated paths, a Node may have multiple opportunities to 823 receive a given data packet. This feature not only enhances the end- 824 to-end reliability but also it reduces the end-to-end delay and 825 increases energy efficiency. 827 ===> (A) ====> (C) ====> (E) ==== 828 // ^ | \\ \\ 829 ingress | | \\ egress 830 \\ | v \\ // 831 ===> (B) ====> (D) ====> (F) ==== 833 Figure 6: Unicast with Overhearing 835 6.2.4. Constructive Interference 837 Constructive Interference can be seen as the reverse of Promiscuous 838 Overhearing, and refers to the case where two senders transmit the 839 exact same signal in a fashion that the emitted symbols add up at the 840 receiver and permit a reception that would not be possible with a 841 single sender at the same PHY mode and the same power level. 843 Constructive Interference was proposed on 5G, Wi-Fi7 and even tested 844 on IEEE Std 802.14.5. The hard piece is to synchronize the senders 845 to the point that the signals are emitted at slightly different time 846 to offset the difference of propagation delay that corresponds to the 847 difference of distance of the transmitters to the receiver at the 848 speed of light to the point that the symbols are superposed long 849 enough to be recognizable. 851 7. RAW Architecture 853 RAW inherits the conceptual model described in section 4 of the 854 DetNet Architecture [RFC8655]. 856 A Controller Plane Function (CPF) called the Path Computation Element 857 (PCE) [RFC4655] interacts with RAW Nodes over a Southbound API. The 858 RAW Nodes are DetNet relays that are capable of additional diversity 859 mechanisms and measurement functions related to the radio interface, 860 in particular the PAREO diversity mechanisms. 862 The PCE defines a complex Track between an Ingress End System and an 863 Egress End System, and indicates to the RAW Nodes where the PAREO 864 operations may be actioned in the Network Plane. The Track may be 865 loosely expressed in order to traverse a non-RAW subnetwork. In that 866 case, the expectation is that the non-RAW subnetwork can be neglected 867 in the RAW computation, that is, considered infinitely fast, reliable 868 and/or available in comparison with the links between RAW nodes. 870 CPF CPF CPF CPF 872 Southbound API 873 _-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._- 874 _-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._- 876 RAW --z RAW --z RAW --z RAW 877 z-- Node z-- Node z-- Node z-- Node --z 878 Ingress --z / / z-- Egress 879 End \ \ End 880 Node ---z / / ..... z-- Node 881 z-- RAW --z RAW ( non-RAW ) --- RAW ---z 882 Node z-- Node --- ( Nodes ) Node 883 ... 884 --z wireless wired 885 z-- link --- link 887 Figure 7: RAW Nodes 889 The Link-Layer metrics are reported to the PCE in a time-aggregated, 890 e.g., statistical fashion. Example Link-Layer metrics include 891 typical Link bandwidth (the medium speed depends dynamically on the 892 PHY mode and the number of users sharing the spectrum) and average 893 availability and reliability figures such as Packet Delivery Ratio 894 (PDR) over long periods of time. 896 Based on those metrics, the PCE installs the Track with enough 897 redundant forwarding solutions to ensure that the Network Plane can 898 reliably deliver the packets within a System Level Agreement (SLA) 899 associated to the flow. The SLA defines end-to-end reliability and 900 availability figures, where reliability may be expressed a successful 901 delivery within a bounded delay. Once a Track is established, end- 902 to-end subpath and overall reliability and availability metrics are 903 also reported to the PCE to assure that the SLA is continuously met 904 and to have it recompute the Track if not. 906 Depending on the SLA, the Track or a leg of the Track may include 907 non-RAW Nodes, either interleaved inside the Track, or more typically 908 till the Egress End Node. RAW observes the Lower-Layer Links between 909 RAW nodes (typically, radio links) and the end-to-end Network Layer 910 subpath to decide at all times which of the PAREO diversity is 911 actioned by which RAW Nodes. 913 7.1. PCE vs. PSE 915 Section 5.3 shows that the time scale at which RAW operates is not 916 that of the Controller Plane that needs to deal with a possibly large 917 whole network and make global optimization across multiple flows that 918 may contend for limited resources. 920 RAW separates the path computation time scale at which a complex path 921 is recomputed from the path selection time scale at which the 922 forwarding decision is taken for one or a few packets. RAW operates 923 at the path selection time scale. The RAW problem is to decide, 924 within the redundant solutions that are proposed by the PCE, which 925 will be used for each packet to provide a Reliable and Available 926 service while minimizing the waste of constrained resources. 928 To that effect, RAW defines the Path Selection Engine (PSE) that is 929 the counter-part of the PCE to perform rapid local adjustments of the 930 forwarding tables within the diversity that the PCE has selected for 931 the Track. The PSE enables to exploit the richer forwarding 932 capabilities with PAREO and scheduled transmissions at a faster time 933 scale over the smaller domain that is the Track, in either a loose or 934 a strict fashion. 936 +---------------+------------------------+-------------------+ 937 | | PCE (Not in Scope) | PSE (In Scope) | 938 +===============+========================+===================+ 939 | Operation | Centralized | Source-Routed or | 940 | | | Distributed | 941 +---------------+------------------------+-------------------+ 942 | Communication | Slow, expensive | Fast, local | 943 +---------------+------------------------+-------------------+ 944 | Time Scale | Long (hours, days) | Short (seconds, | 945 | | | sub-second) | 946 +---------------+------------------------+-------------------+ 947 | Network Size | Large, many Tracks to | Small, within one | 948 | | optimize globally | Track | 949 +---------------+------------------------+-------------------+ 950 | Considered | Averaged, Statistical, | Instant values / | 951 | Metrics | Shade of grey | boolean condition | 952 +---------------+------------------------+-------------------+ 954 Table 2: PCE vs. PSE 956 7.2. RAW OAM 958 The RAW OAM operation in the Network Plane observes a subset of the 959 links along that redundant path and the RAW PSE makes the decision on 960 which PAREO function in actioned at which RAW Node, for a packet or a 961 small collection of packets. 963 ... .. 964 RAN 1 ----- ... .. ... 965 / . .. .... 966 +-------+ / . .. .... +------+ 967 |Ingress|- . ..... |Egress| 968 | End |------ RAN 2 -- . Internet ....---| End | 969 |System |- .. ..... |System| 970 +-------+ \ . ...... +------+ 971 \ ... ... ..... 972 RAN n -------- ... ..... 974 <------------------> <--------------------> 975 Observed by OAM Opaque to OAM 977 Figure 8: Observed Links in Radio Access Protection 979 In the case of a End-to-End Protection in a Wireless Mesh, the Track 980 is strict and congruent with the path so all links are observed. 981 Conversely, in the case of Radio Access Protection, the Track is 982 Loose and in that case only the first hop is observed; the rest of 983 the path is abstracted and considered infinitely reliable. 985 In the case of the Radio Access Protection, only the first hop is 986 protected; the loss of a packet that was sent over one of the 987 possible first hops is attributed to that first hop, even if a 988 particular loss effectively happens farther down the path. 990 The Links that are not observed by OAM are opaque to it, meaning that 991 the OAM information is carried across and possibly echoed as data, 992 but there is no information capture in intermediate nodes. In the 993 example above, the Internet is opaque and not controlled by RAW; 994 still the RAW OAM measures the end-to-end latency and delivery ratio 995 for packets sent via each if RAN 1, RAN 2 and RAN 3, and determines 996 whether a packet should be sent over either or a collection of those 997 access links. 999 7.3. Source-Routed vs. Distributed Forwarding Decision 1001 Within a large routed topology, the route-over mesh operation builds 1002 a particular complex Track with one source and one or more 1003 destinations; within the Track, packets may follow different paths 1004 and may be subject to RAW forwarding operations that include 1005 replication, elimination, retries, overhearing and reordering. 1007 The RAW forwarding decisions include the selection of points of 1008 replication and elimination, how many retries can take place, and a 1009 limit of validity for the packet beyond which the packet should be 1010 destroyed rather than forwarded uselessly further down the Track. 1012 The decision to apply the RAW techniques must be done quickly, and 1013 depends on a very recent and precise knowledge of the forwarding 1014 conditions within the complex Track. There is a need for an 1015 observation method to provide the RAW Data Plane with the specific 1016 knowledge of the state of the Track for the type of flow of interest 1017 (e.g., for a QoS level of interest). To observe the whole Track in 1018 quasi real time, RAW considers existing tools such as L2-triggers, 1019 DLEP, BFD and leverages in-band and out-of-band OAM to capture and 1020 repotr that information to the SRE. 1022 One possible way of making the RAW forwarding decisions within a 1023 Track is to position a unique SRE at the ingress and express its 1024 decision in-band in the packet, which requires new loose or strict 1025 signaling. To control the RAW forwarding operation along a Track for 1026 the individual packets, RAW leverages and extends known techniques 1027 such as DetNet tagging, Segment Routing (SRv6) or BIER-TE such as 1028 done with [BIER-PREF]. 1030 The alternate way is to operate the SRE in each forwarding Node, 1031 which makes the RAW forwarding decisions for a packet on its own, 1032 based on its knowledge of the expectation (timeliness and 1033 reliability) for that packet and a recent observation of the rest of 1034 the way across the possible paths based on OAM. Information about 1035 the desired service should be placed in the packet and matched with 1036 the forwarding Node's capabilities and policies. 1038 In either case, a per-flow state is installed in all intermediate 1039 Nodes to recognize the flow and determine the forwarding policy to be 1040 applied. 1042 7.4. Flow Identification 1044 Section 4.7 of the DetNet Architecture [RFC8655] ties the app-flow 1045 identification which is an appliation layer concept with the network 1046 path identification that depends on the networking technology by 1047 "exporting of flow identification", e.g., to a MPLS label. 1049 With RAW, this exporting operation is injective but not bijective. 1050 e.g., a flow is fully placed within one RAW Track, but not all 1051 packets along that Track are necessarily part of the same flow. For 1052 instance, out-of-band OAM packets must circulate in the exact same 1053 fashion as the flows that they observe. It results that the flow 1054 identification that maps to to app-flow at the network layer must be 1055 separate from the path identification that is used to forward a 1056 packet. 1058 Flow 1 (6-tuple) ----+ 1059 | 1060 Flow 2 (6-tuple) ---+ | 1061 | | 1062 OAM -----------+ | | 1063 | | | 1064 | | | 1065 | | | | | 1066 | v v v | 1067 | | 1068 +---------+---------+ 1069 | 1070 | 1071 +------------> Track 1 1072 (IP address, instanceId) 1074 Figure 9: Flow Injection 1076 Section 3.4 of the DetNet data-plane framework [DetNet-DP-FW] 1077 indicates that for a DetNet IP Data Plane, a flow is identified by an 1078 IPv6 6-tuple. With RAW, that 6-tuple is not what indicates the 1079 Track, in other words, the flow ID is not the Track ID. 1081 For instance, the 6TiSCH Architecture [6TiSCH-ARCHI] uses a 1082 combination of the address of the Ingress End System and an instance 1083 identifier in a Hop-by-hop option to indicate a Track. Packets that 1084 are tagged with the same (address, instance ID) tuple will experience 1085 the same forwarding behavior regardless of the IPv6 6-tuple, and 1086 regardless of whether they transport application flows or OAM. 1088 8. Security Considerations 1090 RAW uses all forms of diversity including radio technology and 1091 physical path to increase the reliability and availability in the 1092 face of unpredictable conditions. While this is not done 1093 specifically to defeat an attacker, the amount of diversity used in 1094 RAW makes an attack harder to achieve. 1096 8.1. Forced Access 1098 RAW will typically select the cheapest collection of links that 1099 matches the requested SLA, for instance, leverage free WI-Fi vs. paid 1100 3GPP access. By defeating the cheap connectivity (e.g., PHY-layer 1101 interference) the attacker can force an End System to use the paid 1102 access and increase the cost of the transmission for the user. 1104 9. IANA Considerations 1106 This document has no IANA actions. 1108 10. Contributors 1110 Xavi Vilajosana: Wireless Networks Research Lab, Universitat Oberta 1111 de Catalunya 1113 Rex Buddenberg: 1115 Remous-Aris Koutsiamanis: IMT Atlantique 1117 Nicolas Montavont: IMT Atlantique 1119 11. Acknowledgments 1121 TBD 1123 12. References 1125 12.1. Normative References 1127 [6TiSCH-ARCHI] 1128 Thubert, P., "An Architecture for IPv6 over the TSCH mode 1129 of IEEE 802.15.4", Work in Progress, Internet-Draft, 1130 draft-ietf-6tisch-architecture-28, 29 October 2019, 1131 . 1134 [RAW-TECHNOS] 1135 Thubert, P., Cavalcanti, D., Vilajosana, X., and C. 1136 Schmitt, "Reliable and Available Wireless Technologies", 1137 Work in Progress, Internet-Draft, draft-thubert-raw- 1138 technologies-04, 6 January 2020, 1139 . 1142 [RAW-USE-CASES] 1143 Papadopoulos, G., Thubert, P., Theoleyre, F., and C. 1144 Bernardos, "RAW use cases", Work in Progress, Internet- 1145 Draft, draft-bernardos-raw-use-cases-03, 8 March 2020, 1146 . 1149 [RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path 1150 Computation Element (PCE)-Based Architecture", RFC 4655, 1151 DOI 10.17487/RFC4655, August 2006, 1152 . 1154 [BFD] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 1155 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 1156 . 1158 [RFC6291] Andersson, L., van Helvoort, H., Bonica, R., Romascanu, 1159 D., and S. Mansfield, "Guidelines for the Use of the "OAM" 1160 Acronym in the IETF", BCP 161, RFC 6291, 1161 DOI 10.17487/RFC6291, June 2011, 1162 . 1164 [RFC8578] Grossman, E., Ed., "Deterministic Networking Use Cases", 1165 RFC 8578, DOI 10.17487/RFC8578, May 2019, 1166 . 1168 [RFC8175] Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and B. 1169 Berry, "Dynamic Link Exchange Protocol (DLEP)", RFC 8175, 1170 DOI 10.17487/RFC8175, June 2017, 1171 . 1173 [RFC8557] Finn, N. and P. Thubert, "Deterministic Networking Problem 1174 Statement", RFC 8557, DOI 10.17487/RFC8557, May 2019, 1175 . 1177 [RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas, 1178 "Deterministic Networking Architecture", RFC 8655, 1179 DOI 10.17487/RFC8655, October 2019, 1180 . 1182 12.2. Informative References 1184 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 1185 DOI 10.17487/RFC0791, September 1981, 1186 . 1188 [TE] Awduche, D., Chiu, A., Elwalid, A., Widjaja, I., and X. 1189 Xiao, "Overview and Principles of Internet Traffic 1190 Engineering", RFC 3272, DOI 10.17487/RFC3272, May 2002, 1191 . 1193 [STD 62] Harrington, D., Presuhn, R., and B. Wijnen, "An 1194 Architecture for Describing Simple Network Management 1195 Protocol (SNMP) Management Frameworks", STD 62, RFC 3411, 1196 DOI 10.17487/RFC3411, December 2002, 1197 . 1199 [RFC4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast 1200 Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090, 1201 DOI 10.17487/RFC4090, May 2005, 1202 . 1204 [FRR] Shand, M. and S. Bryant, "IP Fast Reroute Framework", 1205 RFC 5714, DOI 10.17487/RFC5714, January 2010, 1206 . 1208 [RLFA-FRR] Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N. 1209 So, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)", 1210 RFC 7490, DOI 10.17487/RFC7490, April 2015, 1211 . 1213 [BIER-PREF] 1214 Thubert, P., Eckert, T., Brodard, Z., and H. Jiang, "BIER- 1215 TE extensions for Packet Replication and Elimination 1216 Function (PREF) and OAM", Work in Progress, Internet- 1217 Draft, draft-thubert-bier-replication-elimination-03, 3 1218 March 2018, . 1221 [DetNet-IP-OAM] 1222 Mirsky, G., Chen, M., and D. Black, "Operations, 1223 Administration and Maintenance (OAM) for Deterministic 1224 Networks (DetNet) with IP Data Plane", Work in Progress, 1225 Internet-Draft, draft-mirsky-detnet-ip-oam-02, 23 March 1226 2020, . 1229 [DetNet-DP-FW] 1230 Varga, B., Farkas, J., Berger, L., Malis, A., and S. 1231 Bryant, "DetNet Data Plane Framework", Work in Progress, 1232 Internet-Draft, draft-ietf-detnet-data-plane-framework-06, 1233 6 May 2020, . 1236 [RAW-5G] Farkas, J., Dudda, T., Shapin, A., and S. Sandberg, "5G - 1237 Ultra-Reliable Wireless Technology with Low Latency", Work 1238 in Progress, Internet-Draft, draft-farkas-raw-5g-00, 1 1239 April 2020, 1240 . 1242 [NASA] Adams, T., "RELIABILITY: Definition & Quantitative 1243 Illustration", . 1246 [MANET] IETF, "Mobile Ad hoc Networking", 1247 . 1249 [detnet] IETF, "Deterministic Networking", 1250 . 1252 [SPRING] IETF, "Source Packet Routing in Networking", 1253 . 1255 [BIER] IETF, "Bit Indexed Explicit Replication", 1256 . 1258 [BFD] IETF, "Bidirectional Forwarding Detection", 1259 . 1261 [CCAMP] IETF, "Common Control and Measurement Plane", 1262 . 1264 Authors' Addresses 1266 Pascal Thubert (editor) 1267 Cisco Systems, Inc 1268 Building D 1269 45 Allee des Ormes - BP1200 1270 06254 MOUGINS - Sophia Antipolis 1271 France 1273 Phone: +33 497 23 26 34 1274 Email: pthubert@cisco.com 1276 Georgios Z. Papadopoulos 1277 IMT Atlantique 1278 Office B00 - 114A 1279 2 Rue de la Chataigneraie 1280 35510 Cesson-Sevigne - Rennes 1281 France 1283 Phone: +33 299 12 70 04 1284 Email: georgios.papadopoulos@imt-atlantique.fr 1286 Rex Buddenberg 1287 CA 1288 United States of America 1290 Email: buddenbergr@gmail.com