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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force E. Grossman, Ed. 3 Internet-Draft DOLBY 4 Intended status: Informational June 26, 2018 5 Expires: December 28, 2018 7 Deterministic Networking Use Cases 8 draft-ietf-detnet-use-cases-17 10 Abstract 12 This draft documents requirements in several diverse industries to 13 establish multi-hop paths for characterized flows with deterministic 14 properties. In this context deterministic implies that flows can be 15 established which provide guaranteed bandwidth and latency which can 16 be established from either a Layer 2 or Layer 3 (IP) interface, and 17 which can co-exist on an IP network with best-effort traffic. 19 Additional requirements include optional redundant paths, very high 20 reliability paths, time synchronization, and clock distribution. 21 Industries considered include professional audio, electrical 22 utilities, building automation systems, wireless for industrial, 23 cellular radio, industrial machine-to-machine, mining, private 24 blockchain, and network slicing. 26 For each case, this document will identify the application, identify 27 representative solutions used today, and the improvements IETF DetNet 28 solutions may enable. 30 Status of This Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at https://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 This Internet-Draft will expire on December 28, 2018. 47 Copyright Notice 49 Copyright (c) 2018 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (https://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5 65 2. Pro Audio and Video . . . . . . . . . . . . . . . . . . . . . 6 66 2.1. Use Case Description . . . . . . . . . . . . . . . . . . 6 67 2.1.1. Uninterrupted Stream Playback . . . . . . . . . . . . 7 68 2.1.2. Synchronized Stream Playback . . . . . . . . . . . . 7 69 2.1.3. Sound Reinforcement . . . . . . . . . . . . . . . . . 8 70 2.1.4. Deterministic Time to Establish Streaming . . . . . . 8 71 2.1.5. Secure Transmission . . . . . . . . . . . . . . . . . 8 72 2.1.5.1. Safety . . . . . . . . . . . . . . . . . . . . . 8 73 2.2. Pro Audio Today . . . . . . . . . . . . . . . . . . . . . 9 74 2.3. Pro Audio Future . . . . . . . . . . . . . . . . . . . . 9 75 2.3.1. Layer 3 Interconnecting Layer 2 Islands . . . . . . . 9 76 2.3.2. High Reliability Stream Paths . . . . . . . . . . . . 9 77 2.3.3. Integration of Reserved Streams into IT Networks . . 9 78 2.3.4. Use of Unused Reservations by Best-Effort Traffic . . 10 79 2.3.5. Traffic Segregation . . . . . . . . . . . . . . . . . 10 80 2.3.5.1. Packet Forwarding Rules, VLANs and Subnets . . . 10 81 2.3.5.2. Multicast Addressing (IPv4 and IPv6) . . . . . . 11 82 2.3.6. Latency Optimization by a Central Controller . . . . 11 83 2.3.7. Reduced Device Cost Due To Reduced Buffer Memory . . 11 84 2.4. Pro Audio Asks . . . . . . . . . . . . . . . . . . . . . 12 85 3. Electrical Utilities . . . . . . . . . . . . . . . . . . . . 12 86 3.1. Use Case Description . . . . . . . . . . . . . . . . . . 12 87 3.1.1. Transmission Use Cases . . . . . . . . . . . . . . . 12 88 3.1.1.1. Protection . . . . . . . . . . . . . . . . . . . 12 89 3.1.1.2. Intra-Substation Process Bus Communications . . . 18 90 3.1.1.3. Wide Area Monitoring and Control Systems . . . . 19 91 3.1.1.4. IEC 61850 WAN engineering guidelines requirement 92 classification . . . . . . . . . . . . . . . . . 20 93 3.1.2. Generation Use Case . . . . . . . . . . . . . . . . . 21 94 3.1.2.1. Control of the Generated Power . . . . . . . . . 21 95 3.1.2.2. Control of the Generation Infrastructure . . . . 22 96 3.1.3. Distribution use case . . . . . . . . . . . . . . . . 27 97 3.1.3.1. Fault Location Isolation and Service Restoration 98 (FLISR) . . . . . . . . . . . . . . . . . . . . . 27 99 3.2. Electrical Utilities Today . . . . . . . . . . . . . . . 28 100 3.2.1. Security Current Practices and Limitations . . . . . 28 101 3.3. Electrical Utilities Future . . . . . . . . . . . . . . . 30 102 3.3.1. Migration to Packet-Switched Network . . . . . . . . 31 103 3.3.2. Telecommunications Trends . . . . . . . . . . . . . . 31 104 3.3.2.1. General Telecommunications Requirements . . . . . 31 105 3.3.2.2. Specific Network topologies of Smart Grid 106 Applications . . . . . . . . . . . . . . . . . . 32 107 3.3.2.3. Precision Time Protocol . . . . . . . . . . . . . 33 108 3.3.3. Security Trends in Utility Networks . . . . . . . . . 34 109 3.4. Electrical Utilities Asks . . . . . . . . . . . . . . . . 36 110 4. Building Automation Systems . . . . . . . . . . . . . . . . . 36 111 4.1. Use Case Description . . . . . . . . . . . . . . . . . . 36 112 4.2. Building Automation Systems Today . . . . . . . . . . . . 37 113 4.2.1. BAS Architecture . . . . . . . . . . . . . . . . . . 37 114 4.2.2. BAS Deployment Model . . . . . . . . . . . . . . . . 38 115 4.2.3. Use Cases for Field Networks . . . . . . . . . . . . 40 116 4.2.3.1. Environmental Monitoring . . . . . . . . . . . . 40 117 4.2.3.2. Fire Detection . . . . . . . . . . . . . . . . . 40 118 4.2.3.3. Feedback Control . . . . . . . . . . . . . . . . 41 119 4.2.4. Security Considerations . . . . . . . . . . . . . . . 41 120 4.3. BAS Future . . . . . . . . . . . . . . . . . . . . . . . 41 121 4.4. BAS Asks . . . . . . . . . . . . . . . . . . . . . . . . 42 122 5. Wireless for Industrial . . . . . . . . . . . . . . . . . . . 42 123 5.1. Use Case Description . . . . . . . . . . . . . . . . . . 42 124 5.1.1. Network Convergence using 6TiSCH . . . . . . . . . . 43 125 5.1.2. Common Protocol Development for 6TiSCH . . . . . . . 43 126 5.2. Wireless Industrial Today . . . . . . . . . . . . . . . . 44 127 5.3. Wireless Industrial Future . . . . . . . . . . . . . . . 44 128 5.3.1. Unified Wireless Network and Management . . . . . . . 44 129 5.3.1.1. PCE and 6TiSCH ARQ Retries . . . . . . . . . . . 46 130 5.3.2. Schedule Management by a PCE . . . . . . . . . . . . 47 131 5.3.2.1. PCE Commands and 6TiSCH CoAP Requests . . . . . . 47 132 5.3.2.2. 6TiSCH IP Interface . . . . . . . . . . . . . . . 48 133 5.3.3. 6TiSCH Security Considerations . . . . . . . . . . . 49 134 5.4. Wireless Industrial Asks . . . . . . . . . . . . . . . . 49 135 6. Cellular Radio . . . . . . . . . . . . . . . . . . . . . . . 49 136 6.1. Use Case Description . . . . . . . . . . . . . . . . . . 49 137 6.1.1. Network Architecture . . . . . . . . . . . . . . . . 49 138 6.1.2. Delay Constraints . . . . . . . . . . . . . . . . . . 50 139 6.1.3. Time Synchronization Constraints . . . . . . . . . . 52 140 6.1.4. Transport Loss Constraints . . . . . . . . . . . . . 54 141 6.1.5. Security Considerations . . . . . . . . . . . . . . . 54 142 6.2. Cellular Radio Networks Today . . . . . . . . . . . . . . 55 143 6.2.1. Fronthaul . . . . . . . . . . . . . . . . . . . . . . 55 144 6.2.2. Midhaul and Backhaul . . . . . . . . . . . . . . . . 55 145 6.3. Cellular Radio Networks Future . . . . . . . . . . . . . 56 146 6.4. Cellular Radio Networks Asks . . . . . . . . . . . . . . 58 147 7. Industrial M2M . . . . . . . . . . . . . . . . . . . . . . . 59 148 7.1. Use Case Description . . . . . . . . . . . . . . . . . . 59 149 7.2. Industrial M2M Communication Today . . . . . . . . . . . 60 150 7.2.1. Transport Parameters . . . . . . . . . . . . . . . . 60 151 7.2.2. Stream Creation and Destruction . . . . . . . . . . . 61 152 7.3. Industrial M2M Future . . . . . . . . . . . . . . . . . . 61 153 7.4. Industrial M2M Asks . . . . . . . . . . . . . . . . . . . 62 154 8. Mining Industry . . . . . . . . . . . . . . . . . . . . . . . 62 155 8.1. Use Case Description . . . . . . . . . . . . . . . . . . 62 156 8.2. Mining Industry Today . . . . . . . . . . . . . . . . . . 63 157 8.3. Mining Industry Future . . . . . . . . . . . . . . . . . 63 158 8.4. Mining Industry Asks . . . . . . . . . . . . . . . . . . 64 159 9. Private Blockchain . . . . . . . . . . . . . . . . . . . . . 64 160 9.1. Use Case Description . . . . . . . . . . . . . . . . . . 64 161 9.1.1. Blockchain Operation . . . . . . . . . . . . . . . . 65 162 9.1.2. Blockchain Network Architecture . . . . . . . . . . . 65 163 9.1.3. Security Considerations . . . . . . . . . . . . . . . 66 164 9.2. Private Blockchain Today . . . . . . . . . . . . . . . . 66 165 9.3. Private Blockchain Future . . . . . . . . . . . . . . . . 66 166 9.4. Private Blockchain Asks . . . . . . . . . . . . . . . . . 66 167 10. Network Slicing . . . . . . . . . . . . . . . . . . . . . . . 67 168 10.1. Use Case Description . . . . . . . . . . . . . . . . . . 67 169 10.2. DetNet Applied to Network Slicing . . . . . . . . . . . 67 170 10.2.1. Resource Isolation Across Slices . . . . . . . . . . 67 171 10.2.2. Deterministic Services Within Slices . . . . . . . . 67 172 10.3. A Network Slicing Use Case Example - 5G Bearer Network . 68 173 10.4. Non-5G Applications of Network Slicing . . . . . . . . . 68 174 10.5. Limitations of DetNet in Network Slicing . . . . . . . . 69 175 10.6. Network Slicing Today and Future . . . . . . . . . . . . 69 176 10.7. Network Slicing Asks . . . . . . . . . . . . . . . . . . 69 177 11. Use Case Common Themes . . . . . . . . . . . . . . . . . . . 69 178 11.1. Unified, standards-based network . . . . . . . . . . . . 69 179 11.1.1. Extensions to Ethernet . . . . . . . . . . . . . . . 69 180 11.1.2. Centrally Administered . . . . . . . . . . . . . . . 69 181 11.1.3. Standardized Data Flow Information Models . . . . . 70 182 11.1.4. L2 and L3 Integration . . . . . . . . . . . . . . . 70 183 11.1.5. Consideration for IPv4 . . . . . . . . . . . . . . . 70 184 11.1.6. Guaranteed End-to-End Delivery . . . . . . . . . . . 70 185 11.1.7. Replacement for Multiple Proprietary Deterministic 186 Networks . . . . . . . . . . . . . . . . . . . . . . 70 187 11.1.8. Mix of Deterministic and Best-Effort Traffic . . . . 71 188 11.1.9. Unused Reserved BW to be Available to Best Effort 189 Traffic . . . . . . . . . . . . . . . . . . . . . . 71 190 11.1.10. Lower Cost, Multi-Vendor Solutions . . . . . . . . . 71 192 11.2. Scalable Size . . . . . . . . . . . . . . . . . . . . . 71 193 11.3. Scalable Timing Parameters and Accuracy . . . . . . . . 71 194 11.3.1. Bounded Latency . . . . . . . . . . . . . . . . . . 71 195 11.3.2. Low Latency . . . . . . . . . . . . . . . . . . . . 72 196 11.3.3. Symmetrical Path Delays . . . . . . . . . . . . . . 72 197 11.4. High Reliability and Availability . . . . . . . . . . . 72 198 11.5. Security . . . . . . . . . . . . . . . . . . . . . . . . 72 199 11.6. Deterministic Flows . . . . . . . . . . . . . . . . . . 73 200 12. Use Cases Explicitly Out of Scope for DetNet . . . . . . . . 73 201 12.1. DetNet Scope Limitations . . . . . . . . . . . . . . . . 73 202 12.2. Internet-based Applications . . . . . . . . . . . . . . 74 203 12.2.1. Use Case Description . . . . . . . . . . . . . . . . 74 204 12.2.1.1. Media Content Delivery . . . . . . . . . . . . . 74 205 12.2.1.2. Online Gaming . . . . . . . . . . . . . . . . . 74 206 12.2.1.3. Virtual Reality . . . . . . . . . . . . . . . . 74 207 12.2.2. Internet-Based Applications Today . . . . . . . . . 74 208 12.2.3. Internet-Based Applications Future . . . . . . . . . 74 209 12.2.4. Internet-Based Applications Asks . . . . . . . . . . 75 210 12.3. Pro Audio and Video - Digital Rights Management (DRM) . 75 211 12.4. Pro Audio and Video - Link Aggregation . . . . . . . . . 75 212 13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 76 213 14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 77 214 14.1. Pro Audio . . . . . . . . . . . . . . . . . . . . . . . 77 215 14.2. Utility Telecom . . . . . . . . . . . . . . . . . . . . 78 216 14.3. Building Automation Systems . . . . . . . . . . . . . . 78 217 14.4. Wireless for Industrial . . . . . . . . . . . . . . . . 78 218 14.5. Cellular Radio . . . . . . . . . . . . . . . . . . . . . 78 219 14.6. Industrial M2M . . . . . . . . . . . . . . . . . . . . . 79 220 14.7. Internet Applications and CoMP . . . . . . . . . . . . . 79 221 14.8. Electrical Utilities . . . . . . . . . . . . . . . . . . 79 222 14.9. Network Slicing . . . . . . . . . . . . . . . . . . . . 79 223 14.10. Mining . . . . . . . . . . . . . . . . . . . . . . . . . 79 224 14.11. Private Blockchain . . . . . . . . . . . . . . . . . . . 79 225 15. Informative References . . . . . . . . . . . . . . . . . . . 79 226 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 90 228 1. Introduction 230 This draft presents use cases from diverse industries which have in 231 common a need for deterministic flows, but which also differ notably 232 in their network topologies and specific desired behavior. Together, 233 they provide broad industry context for DetNet and a yardstick 234 against which proposed DetNet designs can be measured (to what extent 235 does a proposed design satisfy these various use cases?) 237 For DetNet, use cases explicitly do not define requirements; The 238 DetNet WG will consider the use cases, decide which elements are in 239 scope for DetNet, and the results will be incorporated into future 240 drafts. Similarly, the DetNet use case draft explicitly does not 241 suggest any specific design, architecture or protocols, which will be 242 topics of future drafts. 244 We present for each use case the answers to the following questions: 246 o What is the use case? 248 o How is it addressed today? 250 o How would you like it to be addressed in the future? 252 o What do you want the IETF to deliver? 254 The level of detail in each use case should be sufficient to express 255 the relevant elements of the use case, but not more. 257 At the end we consider the use cases collectively, and examine the 258 most significant goals they have in common. 260 2. Pro Audio and Video 262 2.1. Use Case Description 264 The professional audio and video industry ("ProAV") includes: 266 o Music and film content creation 268 o Broadcast 270 o Cinema 272 o Live sound 274 o Public address, media and emergency systems at large venues 275 (airports, stadiums, churches, theme parks). 277 These industries have already transitioned audio and video signals 278 from analog to digital. However, the digital interconnect systems 279 remain primarily point-to-point with a single (or small number of) 280 signals per link, interconnected with purpose-built hardware. 282 These industries are now transitioning to packet-based infrastructure 283 to reduce cost, increase routing flexibility, and integrate with 284 existing IT infrastructure. 286 Today ProAV applications have no way to establish deterministic flows 287 from a standards-based Layer 3 (IP) interface, which is a fundamental 288 limitation to the use cases described here. Today deterministic 289 flows can be created within standards-based layer 2 LANs (e.g. using 290 IEEE 802.1 AVB) however these are not routable via IP and thus are 291 not effective for distribution over wider areas (for example 292 broadcast events that span wide geographical areas). 294 It would be highly desirable if such flows could be routed over the 295 open Internet, however solutions with more limited scope (e.g. 296 enterprise networks) would still provide a substantial improvement. 298 The following sections describe specific ProAV use cases. 300 2.1.1. Uninterrupted Stream Playback 302 Transmitting audio and video streams for live playback is unlike 303 common file transfer because uninterrupted stream playback in the 304 presence of network errors cannot be achieved by re-trying the 305 transmission; by the time the missing or corrupt packet has been 306 identified it is too late to execute a re-try operation. Buffering 307 can be used to provide enough delay to allow time for one or more 308 retries, however this is not an effective solution in applications 309 where large delays (latencies) are not acceptable (as discussed 310 below). 312 Streams with guaranteed bandwidth can eliminate congestion on the 313 network as a cause of transmission errors that would lead to playback 314 interruption. Use of redundant paths can further mitigate 315 transmission errors to provide greater stream reliability. 317 2.1.2. Synchronized Stream Playback 319 Latency in this context is the time between when a signal is 320 initially sent over a stream and when it is received. A common 321 example in ProAV is time-synchronizing audio and video when they take 322 separate paths through the playback system. In this case the latency 323 of both the audio and video streams must be bounded and consistent if 324 the sound is to remain matched to the movement in the video. A 325 common tolerance for audio/video sync is one NTSC video frame (about 326 33ms) and to maintain the audience perception of correct lip sync the 327 latency needs to be consistent within some reasonable tolerance, for 328 example 10%. 330 A common architecture for synchronizing multiple streams that have 331 different paths through the network (and thus potentially different 332 latencies) is to enable measurement of the latency of each path, and 333 have the data sinks (for example speakers) delay (buffer) all packets 334 on all but the slowest path. Each packet of each stream is assigned 335 a presentation time which is based on the longest required delay. 337 This implies that all sinks must maintain a common time reference of 338 sufficient accuracy, which can be achieved by any of various 339 techniques. 341 This type of architecture is commonly implemented using a central 342 controller that determines path delays and arbitrates buffering 343 delays. 345 2.1.3. Sound Reinforcement 347 Consider the latency (delay) from when a person speaks into a 348 microphone to when their voice emerges from the speaker. If this 349 delay is longer than about 10-15 milliseconds it is noticeable and 350 can make a sound reinforcement system unusable (see slide 6 of 351 [SRP_LATENCY]). (If you have ever tried to speak in the presence of 352 a delayed echo of your voice you may know this experience). 354 Note that the 15ms latency bound includes all parts of the signal 355 path, not just the network, so the network latency must be 356 significantly less than 15ms. 358 In some cases local performers must perform in synchrony with a 359 remote broadcast. In such cases the latencies of the broadcast 360 stream and the local performer must be adjusted to match each other, 361 with a worst case of one video frame (33ms for NTSC video). 363 In cases where audio phase is a consideration, for example beam- 364 forming using multiple speakers, latency requirements can be in the 365 10 microsecond range (1 audio sample at 96kHz). 367 2.1.4. Deterministic Time to Establish Streaming 369 Note: The WG has decided that guidelines for deterministic time to 370 establish stream startup is not within scope of DetNet. If bounded 371 timing of establishing or re-establish streams is required in a given 372 use case, it is up to the application/system to achieve this. (The 373 supporting text from this section has been removed as of draft 12). 375 2.1.5. Secure Transmission 377 2.1.5.1. Safety 379 Professional audio systems can include amplifiers that are capable of 380 generating hundreds or thousands of watts of audio power which if 381 used incorrectly can cause hearing damage to those in the vicinity. 382 Apart from the usual care required by the systems operators to 383 prevent such incidents, the network traffic that controls these 384 devices must be secured (as with any sensitive application traffic). 386 2.2. Pro Audio Today 388 Some proprietary systems have been created which enable deterministic 389 streams at Layer 3 however they are "engineered networks" which 390 require careful configuration to operate, often require that the 391 system be over-provisioned, and it is implied that all devices on the 392 network voluntarily play by the rules of that network. To enable 393 these industries to successfully transition to an interoperable 394 multi-vendor packet-based infrastructure requires effective open 395 standards, and we believe that establishing relevant IETF standards 396 is a crucial factor. 398 2.3. Pro Audio Future 400 2.3.1. Layer 3 Interconnecting Layer 2 Islands 402 It would be valuable to enable IP to connect multiple Layer 2 LANs. 404 As an example, ESPN recently constructed a state-of-the-art 194,000 405 sq ft, $125 million broadcast studio called DC2. The DC2 network is 406 capable of handling 46 Tbps of throughput with 60,000 simultaneous 407 signals. Inside the facility are 1,100 miles of fiber feeding four 408 audio control rooms (see [ESPN_DC2] ). 410 In designing DC2 they replaced as much point-to-point technology as 411 they could with packet-based technology. They constructed seven 412 individual studios using layer 2 LANS (using IEEE 802.1 AVB) that 413 were entirely effective at routing audio within the LANs. However to 414 interconnect these layer 2 LAN islands together they ended up using 415 dedicated paths in a custom SDN (Software Defined Networking) router 416 because there is no standards-based routing solution available. 418 2.3.2. High Reliability Stream Paths 420 On-air and other live media streams are often backed up with 421 redundant links that seamlessly act to deliver the content when the 422 primary link fails for any reason. In point-to-point systems this is 423 provided by an additional point-to-point link; the analogous 424 requirement in a packet-based system is to provide an alternate path 425 through the network such that no individual link can bring down the 426 system. 428 2.3.3. Integration of Reserved Streams into IT Networks 430 A commonly cited goal of moving to a packet based media 431 infrastructure is that costs can be reduced by using off the shelf, 432 commodity network hardware. In addition, economy of scale can be 433 realized by combining media infrastructure with IT infrastructure. 435 In keeping with these goals, stream reservation technology should be 436 compatible with existing protocols, and not compromise use of the 437 network for best effort (non-time-sensitive) traffic. 439 2.3.4. Use of Unused Reservations by Best-Effort Traffic 441 In cases where stream bandwidth is reserved but not currently used 442 (or is under-utilized) that bandwidth must be available to best- 443 effort (i.e. non-time-sensitive) traffic. For example a single 444 stream may be nailed up (reserved) for specific media content that 445 needs to be presented at different times of the day, ensuring timely 446 delivery of that content, yet in between those times the full 447 bandwidth of the network can be utilized for best-effort tasks such 448 as file transfers. 450 This also addresses a concern of IT network administrators that are 451 considering adding reserved bandwidth traffic to their networks that 452 ("users will reserve large quantities of bandwidth and then never un- 453 reserve it even though they are not using it, and soon the network 454 will have no bandwidth left"). 456 2.3.5. Traffic Segregation 458 Note: It is still under WG discussion whether this topic will be 459 addressed by DetNet. 461 Sink devices may be low cost devices with limited processing power. 462 In order to not overwhelm the CPUs in these devices it is important 463 to limit the amount of traffic that these devices must process. 465 As an example, consider the use of individual seat speakers in a 466 cinema. These speakers are typically required to be cost reduced 467 since the quantities in a single theater can reach hundreds of seats. 468 Discovery protocols alone in a one thousand seat theater can generate 469 enough broadcast traffic to overwhelm a low powered CPU. Thus an 470 installation like this will benefit greatly from some type of traffic 471 segregation that can define groups of seats to reduce traffic within 472 each group. All seats in the theater must still be able to 473 communicate with a central controller. 475 There are many techniques that can be used to support this 476 requirement including (but not limited to) the following examples. 478 2.3.5.1. Packet Forwarding Rules, VLANs and Subnets 480 Packet forwarding rules can be used to eliminate some extraneous 481 streaming traffic from reaching potentially low powered sink devices, 482 however there may be other types of broadcast traffic that should be 483 eliminated using other means for example VLANs or IP subnets. 485 2.3.5.2. Multicast Addressing (IPv4 and IPv6) 487 Multicast addressing is commonly used to keep bandwidth utilization 488 of shared links to a minimum. 490 Because of the MAC Address forwarding nature of Layer 2 bridges it is 491 important that a multicast MAC address is only associated with one 492 stream. This will prevent reservations from forwarding packets from 493 one stream down a path that has no interested sinks simply because 494 there is another stream on that same path that shares the same 495 multicast MAC address. 497 Since each multicast MAC Address can represent 32 different IPv4 498 multicast addresses there must be a process put in place to make sure 499 this does not occur. Requiring use of IPv6 address can achieve this, 500 however due to their continued prevalence, solutions that are 501 effective for IPv4 installations are also required. 503 2.3.6. Latency Optimization by a Central Controller 505 A central network controller might also perform optimizations based 506 on the individual path delays, for example sinks that are closer to 507 the source can inform the controller that they can accept greater 508 latency since they will be buffering packets to match presentation 509 times of farther away sinks. The controller might then move a stream 510 reservation on a short path to a longer path in order to free up 511 bandwidth for other critical streams on that short path. See slides 512 3-5 of [SRP_LATENCY]. 514 Additional optimization can be achieved in cases where sinks have 515 differing latency requirements, for example in a live outdoor concert 516 the speaker sinks have stricter latency requirements than the 517 recording hardware sinks. See slide 7 of [SRP_LATENCY]. 519 2.3.7. Reduced Device Cost Due To Reduced Buffer Memory 521 Device cost can be reduced in a system with guaranteed reservations 522 with a small bounded latency due to the reduced requirements for 523 buffering (i.e. memory) on sink devices. For example, a theme park 524 might broadcast a live event across the globe via a layer 3 protocol; 525 in such cases the size of the buffers required is proportional to the 526 latency bounds and jitter caused by delivery, which depends on the 527 worst case segment of the end-to-end network path. For example on 528 todays open internet the latency is typically unacceptable for audio 529 and video streaming without many seconds of buffering. In such 530 scenarios a single gateway device at the local network that receives 531 the feed from the remote site would provide the expensive buffering 532 required to mask the latency and jitter issues associated with long 533 distance delivery. Sink devices in the local location would have no 534 additional buffering requirements, and thus no additional costs, 535 beyond those required for delivery of local content. The sink device 536 would be receiving the identical packets as those sent by the source 537 and would be unaware that there were any latency or jitter issues 538 along the path. 540 2.4. Pro Audio Asks 542 o Layer 3 routing on top of AVB (and/or other high QoS networks) 544 o Content delivery with bounded, lowest possible latency 546 o IntServ and DiffServ integration with AVB (where practical) 548 o Single network for A/V and IT traffic 550 o Standards-based, interoperable, multi-vendor 552 o IT department friendly 554 o Enterprise-wide networks (e.g. size of San Francisco but not the 555 whole Internet (yet...)) 557 3. Electrical Utilities 559 3.1. Use Case Description 561 Many systems that an electrical utility deploys today rely on high 562 availability and deterministic behavior of the underlying networks. 563 Here we present use cases in Transmission, Generation and 564 Distribution, including key timing and reliability metrics. We also 565 discuss security issues and industry trends which affect the 566 architecture of next generation utility networks 568 3.1.1. Transmission Use Cases 570 3.1.1.1. Protection 572 Protection means not only the protection of human operators but also 573 the protection of the electrical equipment and the preservation of 574 the stability and frequency of the grid. If a fault occurs in the 575 transmission or distribution of electricity then severe damage can 576 occur to human operators, electrical equipment and the grid itself, 577 leading to blackouts. 579 Communication links in conjunction with protection relays are used to 580 selectively isolate faults on high voltage lines, transformers, 581 reactors and other important electrical equipment. The role of the 582 teleprotection system is to selectively disconnect a faulty part by 583 transferring command signals within the shortest possible time. 585 3.1.1.1.1. Key Criteria 587 The key criteria for measuring teleprotection performance are command 588 transmission time, dependability and security. These criteria are 589 defined by the IEC standard 60834 as follows: 591 o Transmission time (Speed): The time between the moment where state 592 changes at the transmitter input and the moment of the 593 corresponding change at the receiver output, including propagation 594 delay. Overall operating time for a teleprotection system 595 includes the time for initiating the command at the transmitting 596 end, the propagation delay over the network (including equipments) 597 and the selection and decision time at the receiving end, 598 including any additional delay due to a noisy environment. 600 o Dependability: The ability to issue and receive valid commands in 601 the presence of interference and/or noise, by minimizing the 602 probability of missing command (PMC). Dependability targets are 603 typically set for a specific bit error rate (BER) level. 605 o Security: The ability to prevent false tripping due to a noisy 606 environment, by minimizing the probability of unwanted commands 607 (PUC). Security targets are also set for a specific bit error 608 rate (BER) level. 610 Additional elements of the the teleprotection system that impact its 611 performance include: 613 o Network bandwidth 615 o Failure recovery capacity (aka resiliency) 617 3.1.1.1.2. Fault Detection and Clearance Timing 619 Most power line equipment can tolerate short circuits or faults for 620 up to approximately five power cycles before sustaining irreversible 621 damage or affecting other segments in the network. This translates 622 to total fault clearance time of 100ms. As a safety precaution, 623 however, actual operation time of protection systems is limited to 624 70- 80 percent of this period, including fault recognition time, 625 command transmission time and line breaker switching time. 627 Some system components, such as large electromechanical switches, 628 require particularly long time to operate and take up the majority of 629 the total clearance time, leaving only a 10ms window for the 630 telecommunications part of the protection scheme, independent of the 631 distance to travel. Given the sensitivity of the issue, new networks 632 impose requirements that are even more stringent: IEC standard 61850 633 limits the transfer time for protection messages to 1/4 - 1/2 cycle 634 or 4 - 8ms (for 60Hz lines) for the most critical messages. 636 3.1.1.1.3. Symmetric Channel Delay 638 Teleprotection channels which are differential must be synchronous, 639 which means that any delays on the transmit and receive paths must 640 match each other. Teleprotection systems ideally support zero 641 asymmetric delay; typical legacy relays can tolerate delay 642 discrepancies of up to 750us. 644 Some tools available for lowering delay variation below this 645 threshold are: 647 o For legacy systems using Time Division Multiplexing (TDM), jitter 648 buffers at the multiplexers on each end of the line can be used to 649 offset delay variation by queuing sent and received packets. The 650 length of the queues must balance the need to regulate the rate of 651 transmission with the need to limit overall delay, as larger 652 buffers result in increased latency. 654 o For jitter-prone IP packet networks, traffic management tools can 655 ensure that the teleprotection signals receive the highest 656 transmission priority to minimize jitter. 658 o Standard packet-based synchronization technologies, such as 659 1588-2008 Precision Time Protocol (PTP) and Synchronous Ethernet 660 (Sync-E), can help keep networks stable by maintaining a highly 661 accurate clock source on the various network devices. 663 3.1.1.1.4. Teleprotection Network Requirements (IEC 61850) 665 The following table captures the main network metrics as based on the 666 IEC 61850 standard. 668 +-----------------------------+-------------------------------------+ 669 | Teleprotection Requirement | Attribute | 670 +-----------------------------+-------------------------------------+ 671 | One way maximum delay | 4-10 ms | 672 | Asymetric delay required | Yes | 673 | Maximum jitter | less than 250 us (750 us for legacy | 674 | | IED) | 675 | Topology | Point to point, point to Multi- | 676 | | point | 677 | Availability | 99.9999 | 678 | precise timing required | Yes | 679 | Recovery time on node | less than 50ms - hitless | 680 | failure | | 681 | performance management | Yes, Mandatory | 682 | Redundancy | Yes | 683 | Packet loss | 0.1% to 1% | 684 +-----------------------------+-------------------------------------+ 686 Table 1: Teleprotection network requirements 688 3.1.1.1.5. Inter-Trip Protection scheme 690 "Inter-tripping" is the signal-controlled tripping of a circuit 691 breaker to complete the isolation of a circuit or piece of apparatus 692 in concert with the tripping of other circuit breakers. 694 +--------------------------------+----------------------------------+ 695 | Inter-Trip protection | Attribute | 696 | Requirement | | 697 +--------------------------------+----------------------------------+ 698 | One way maximum delay | 5 ms | 699 | Asymetric delay required | No | 700 | Maximum jitter | Not critical | 701 | Topology | Point to point, point to Multi- | 702 | | point | 703 | Bandwidth | 64 Kbps | 704 | Availability | 99.9999 | 705 | precise timing required | Yes | 706 | Recovery time on node failure | less than 50ms - hitless | 707 | performance management | Yes, Mandatory | 708 | Redundancy | Yes | 709 | Packet loss | 0.1% | 710 +--------------------------------+----------------------------------+ 712 Table 2: Inter-Trip protection network requirements 714 3.1.1.1.6. Current Differential Protection Scheme 716 Current differential protection is commonly used for line protection, 717 and is typical for protecting parallel circuits. At both end of the 718 lines the current is measured by the differential relays, and both 719 relays will trip the circuit breaker if the current going into the 720 line does not equal the current going out of the line. This type of 721 protection scheme assumes some form of communications being present 722 between the relays at both end of the line, to allow both relays to 723 compare measured current values. Line differential protection 724 schemes assume a very low telecommunications delay between both 725 relays, often as low as 5ms. Moreover, as those systems are often 726 not time-synchronized, they also assume symmetric telecommunications 727 paths with constant delay, which allows comparing current measurement 728 values taken at the exact same time. 730 +----------------------------------+--------------------------------+ 731 | Current Differential protection | Attribute | 732 | Requirement | | 733 +----------------------------------+--------------------------------+ 734 | One way maximum delay | 5 ms | 735 | Asymetric delay Required | Yes | 736 | Maximum jitter | less than 250 us (750us for | 737 | | legacy IED) | 738 | Topology | Point to point, point to | 739 | | Multi-point | 740 | Bandwidth | 64 Kbps | 741 | Availability | 99.9999 | 742 | precise timing required | Yes | 743 | Recovery time on node failure | less than 50ms - hitless | 744 | performance management | Yes, Mandatory | 745 | Redundancy | Yes | 746 | Packet loss | 0.1% | 747 +----------------------------------+--------------------------------+ 749 Table 3: Current Differential Protection metrics 751 3.1.1.1.7. Distance Protection Scheme 753 Distance (Impedance Relay) protection scheme is based on voltage and 754 current measurements. The network metrics are similar (but not 755 identical to) Current Differential protection. 757 +-------------------------------+-----------------------------------+ 758 | Distance protection | Attribute | 759 | Requirement | | 760 +-------------------------------+-----------------------------------+ 761 | One way maximum delay | 5 ms | 762 | Asymetric delay Required | No | 763 | Maximum jitter | Not critical | 764 | Topology | Point to point, point to Multi- | 765 | | point | 766 | Bandwidth | 64 Kbps | 767 | Availability | 99.9999 | 768 | precise timing required | Yes | 769 | Recovery time on node failure | less than 50ms - hitless | 770 | performance management | Yes, Mandatory | 771 | Redundancy | Yes | 772 | Packet loss | 0.1% | 773 +-------------------------------+-----------------------------------+ 775 Table 4: Distance Protection requirements 777 3.1.1.1.8. Inter-Substation Protection Signaling 779 This use case describes the exchange of Sampled Value and/or GOOSE 780 (Generic Object Oriented Substation Events) message between 781 Intelligent Electronic Devices (IED) in two substations for 782 protection and tripping coordination. The two IEDs are in a master- 783 slave mode. 785 The Current Transformer or Voltage Transformer (CT/VT) in one 786 substation sends the sampled analog voltage or current value to the 787 Merging Unit (MU) over hard wire. The MU sends the time-synchronized 788 61850-9-2 sampled values to the slave IED. The slave IED forwards 789 the information to the Master IED in the other substation. The 790 master IED makes the determination (for example based on sampled 791 value differentials) to send a trip command to the originating IED. 792 Once the slave IED/Relay receives the GOOSE trip for breaker 793 tripping, it opens the breaker. It then sends a confirmation message 794 back to the master. All data exchanges between IEDs are either 795 through Sampled Value and/or GOOSE messages. 797 +----------------------------------+--------------------------------+ 798 | Inter-Substation protection | Attribute | 799 | Requirement | | 800 +----------------------------------+--------------------------------+ 801 | One way maximum delay | 5 ms | 802 | Asymetric delay Required | No | 803 | Maximum jitter | Not critical | 804 | Topology | Point to point, point to | 805 | | Multi-point | 806 | Bandwidth | 64 Kbps | 807 | Availability | 99.9999 | 808 | precise timing required | Yes | 809 | Recovery time on node failure | less than 50ms - hitless | 810 | performance management | Yes, Mandatory | 811 | Redundancy | Yes | 812 | Packet loss | 1% | 813 +----------------------------------+--------------------------------+ 815 Table 5: Inter-Substation Protection requirements 817 3.1.1.2. Intra-Substation Process Bus Communications 819 This use case describes the data flow from the CT/VT to the IEDs in 820 the substation via the MU. The CT/VT in the substation send the 821 analog voltage or current values to the MU over hard wire. The MU 822 converts the analog values into digital format (typically time- 823 synchronized Sampled Values as specified by IEC 61850-9-2) and sends 824 them to the IEDs in the substation. The GPS Master Clock can send 825 1PPS or IRIG-B format to the MU through a serial port or IEEE 1588 826 protocol via a network. Process bus communication using 61850 827 simplifies connectivity within the substation and removes the 828 requirement for multiple serial connections and removes the slow 829 serial bus architectures that are typically used. This also ensures 830 increased flexibility and increased speed with the use of multicast 831 messaging between multiple devices. 833 +----------------------------------+--------------------------------+ 834 | Intra-Substation protection | Attribute | 835 | Requirement | | 836 +----------------------------------+--------------------------------+ 837 | One way maximum delay | 5 ms | 838 | Asymetric delay Required | No | 839 | Maximum jitter | Not critical | 840 | Topology | Point to point, point to | 841 | | Multi-point | 842 | Bandwidth | 64 Kbps | 843 | Availability | 99.9999 | 844 | precise timing required | Yes | 845 | Recovery time on Node failure | less than 50ms - hitless | 846 | performance management | Yes, Mandatory | 847 | Redundancy | Yes - No | 848 | Packet loss | 0.1% | 849 +----------------------------------+--------------------------------+ 851 Table 6: Intra-Substation Protection requirements 853 3.1.1.3. Wide Area Monitoring and Control Systems 855 The application of synchrophasor measurement data from Phasor 856 Measurement Units (PMU) to Wide Area Monitoring and Control Systems 857 promises to provide important new capabilities for improving system 858 stability. Access to PMU data enables more timely situational 859 awareness over larger portions of the grid than what has been 860 possible historically with normal SCADA (Supervisory Control and Data 861 Acquisition) data. Handling the volume and real-time nature of 862 synchrophasor data presents unique challenges for existing 863 application architectures. Wide Area management System (WAMS) makes 864 it possible for the condition of the bulk power system to be observed 865 and understood in real-time so that protective, preventative, or 866 corrective action can be taken. Because of the very high sampling 867 rate of measurements and the strict requirement for time 868 synchronization of the samples, WAMS has stringent telecommunications 869 requirements in an IP network that are captured in the following 870 table: 872 +----------------------+--------------------------------------------+ 873 | WAMS Requirement | Attribute | 874 +----------------------+--------------------------------------------+ 875 | One way maximum | 50 ms | 876 | delay | | 877 | Asymetric delay | No | 878 | Required | | 879 | Maximum jitter | Not critical | 880 | Topology | Point to point, point to Multi-point, | 881 | | Multi-point to Multi-point | 882 | Bandwidth | 100 Kbps | 883 | Availability | 99.9999 | 884 | precise timing | Yes | 885 | required | | 886 | Recovery time on | less than 50ms - hitless | 887 | Node failure | | 888 | performance | Yes, Mandatory | 889 | management | | 890 | Redundancy | Yes | 891 | Packet loss | 1% | 892 | Consecutive Packet | At least 1 packet per application cycle | 893 | Loss | must be received. | 894 +----------------------+--------------------------------------------+ 896 Table 7: WAMS Special Communication Requirements 898 3.1.1.4. IEC 61850 WAN engineering guidelines requirement 899 classification 901 The IEC (International Electrotechnical Commission) has recently 902 published a Technical Report which offers guidelines on how to define 903 and deploy Wide Area Networks for the interconnections of electric 904 substations, generation plants and SCADA operation centers. The IEC 905 61850-90-12 is providing a classification of WAN communication 906 requirements into 4 classes. Table 8 summarizes these requirements: 908 +----------------+------------+------------+------------+-----------+ 909 | WAN | Class WA | Class WB | Class WC | Class WD | 910 | Requirement | | | | | 911 +----------------+------------+------------+------------+-----------+ 912 | Application | EHV (Extra | HV (High | MV (Medium | General | 913 | field | High | Voltage) | Voltage) | purpose | 914 | | Voltage) | | | | 915 | Latency | 5 ms | 10 ms | 100 ms | > 100 ms | 916 | Jitter | 10 us | 100 us | 1 ms | 10 ms | 917 | Latency | 100 us | 1 ms | 10 ms | 100 ms | 918 | Asymetry | | | | | 919 | Time Accuracy | 1 us | 10 us | 100 us | 10 to 100 | 920 | | | | | ms | 921 | Bit Error rate | 10-7 to | 10-5 to | 10-3 | | 922 | | 10-6 | 10-4 | | | 923 | Unavailability | 10-7 to | 10-5 to | 10-3 | | 924 | | 10-6 | 10-4 | | | 925 | Recovery delay | Zero | 50 ms | 5 s | 50 s | 926 | Cyber security | extremely | High | Medium | Medium | 927 | | high | | | | 928 +----------------+------------+------------+------------+-----------+ 930 Table 8: 61850-90-12 Communication Requirements; Courtesy of IEC 932 3.1.2. Generation Use Case 934 Energy generation systems are complex infrastructures that require 935 control of both the generated power and the generation 936 infrastructure. 938 3.1.2.1. Control of the Generated Power 940 The electrical power generation frequency must be maintained within a 941 very narrow band. Deviations from the acceptable frequency range are 942 detected and the required signals are sent to the power plants for 943 frequency regulation. 945 Automatic Generation Control (AGC) is a system for adjusting the 946 power output of generators at different power plants, in response to 947 changes in the load. 949 +---------------------------------------------------+---------------+ 950 | FCAG (Frequency Control Automatic Generation) | Attribute | 951 | Requirement | | 952 +---------------------------------------------------+---------------+ 953 | One way maximum delay | 500 ms | 954 | Asymetric delay Required | No | 955 | Maximum jitter | Not critical | 956 | Topology | Point to | 957 | | point | 958 | Bandwidth | 20 Kbps | 959 | Availability | 99.999 | 960 | precise timing required | Yes | 961 | Recovery time on Node failure | N/A | 962 | performance management | Yes, | 963 | | Mandatory | 964 | Redundancy | Yes | 965 | Packet loss | 1% | 966 +---------------------------------------------------+---------------+ 968 Table 9: FCAG Communication Requirements 970 3.1.2.2. Control of the Generation Infrastructure 972 The control of the generation infrastructure combines requirements 973 from industrial automation systems and energy generation systems. In 974 this section we present the use case of the control of the generation 975 infrastructure of a wind turbine. 977 | 978 | 979 | +-----------------+ 980 | | +----+ | 981 | | |WTRM| WGEN | 982 WROT x==|===| | | 983 | | +----+ WCNV| 984 | |WNAC | 985 | +---+---WYAW---+--+ 986 | | | 987 | | | +----+ 988 |WTRF | |WMET| 989 | | | | 990 Wind Turbine | +--+-+ 991 Controller | | 992 WTUR | | | 993 WREP | | | 994 WSLG | | | 995 WALG | WTOW | | 997 Figure 1: Wind Turbine Control Network 999 Figure 1 presents the subsystems that operate a wind turbine. These 1000 subsystems include 1002 o WROT (Rotor Control) 1004 o WNAC (Nacelle Control) (nacelle: housing containing the generator) 1006 o WTRM (Transmission Control) 1008 o WGEN (Generator) 1010 o WYAW (Yaw Controller) (of the tower head) 1012 o WCNV (In-Turbine Power Converter) 1014 o WMET (External Meteorological Station providing real time 1015 information to the controllers of the tower) 1017 Traffic characteristics relevant for the network planning and 1018 dimensioning process in a wind turbine scenario are listed below. 1019 The values in this section are based mainly on the relevant 1020 references [Ahm14] and [Spe09]. Each logical node (Figure 1) is a 1021 part of the metering network and produces analog measurements and 1022 status information which must comply with their respective data rate 1023 constraints. 1025 +-----------+--------+--------+-------------+---------+-------------+ 1026 | Subsystem | Sensor | Analog | Data Rate | Status | Data rate | 1027 | | Count | Sample | (bytes/sec) | Sample | (bytes/sec) | 1028 | | | Count | | Count | | 1029 +-----------+--------+--------+-------------+---------+-------------+ 1030 | WROT | 14 | 9 | 642 | 5 | 10 | 1031 | WTRM | 18 | 10 | 2828 | 8 | 16 | 1032 | WGEN | 14 | 12 | 73764 | 2 | 4 | 1033 | WCNV | 14 | 12 | 74060 | 2 | 4 | 1034 | WTRF | 12 | 5 | 73740 | 2 | 4 | 1035 | WNAC | 12 | 9 | 112 | 3 | 6 | 1036 | WYAW | 7 | 8 | 220 | 4 | 8 | 1037 | WTOW | 4 | 1 | 8 | 3 | 6 | 1038 | WMET | 7 | 7 | 228 | - | - | 1039 +-----------+--------+--------+-------------+---------+-------------+ 1041 Table 10: Wind Turbine Data Rate Constraints 1043 Quality of Service (QoS) constraints for different services are 1044 presented in Table 11. These constraints are defined by IEEE 1646 1045 standard [IEEE1646] and IEC 61400 standard [IEC61400]. 1047 +---------------------+---------+-------------+---------------------+ 1048 | Service | Latency | Reliability | Packet Loss Rate | 1049 +---------------------+---------+-------------+---------------------+ 1050 | Analogue measure | 16 ms | 99.99% | < 10-6 | 1051 | Status information | 16 ms | 99.99% | < 10-6 | 1052 | Protection traffic | 4 ms | 100.00% | < 10-9 | 1053 | Reporting and | 1 s | 99.99% | < 10-6 | 1054 | logging | | | | 1055 | Video surveillance | 1 s | 99.00% | No specific | 1056 | | | | requirement | 1057 | Internet connection | 60 min | 99.00% | No specific | 1058 | | | | requirement | 1059 | Control traffic | 16 ms | 100.00% | < 10-9 | 1060 | Data polling | 16 ms | 99.99% | < 10-6 | 1061 +---------------------+---------+-------------+---------------------+ 1063 Table 11: Wind Turbine Reliability and Latency Constraints 1065 3.1.2.2.1. Intra-Domain Network Considerations 1067 A wind turbine is composed of a large set of subsystems including 1068 sensors and actuators which require time-critical operation. The 1069 reliability and latency constraints of these different subsystems is 1070 shown in Table 11. These subsystems are connected to an intra-domain 1071 network which is used to monitor and control the operation of the 1072 turbine and connect it to the SCADA subsystems. The different 1073 components are interconnected using fiber optics, industrial buses, 1074 industrial Ethernet, EtherCat, or a combination of them. Industrial 1075 signaling and control protocols such as Modbus, Profibus, Profinet 1076 and EtherCat are used directly on top of the Layer 2 transport or 1077 encapsulated over TCP/IP. 1079 The Data collected from the sensors and condition monitoring systems 1080 is multiplexed onto fiber cables for transmission to the base of the 1081 tower, and to remote control centers. The turbine controller 1082 continuously monitors the condition of the wind turbine and collects 1083 statistics on its operation. This controller also manages a large 1084 number of switches, hydraulic pumps, valves, and motors within the 1085 wind turbine. 1087 There is usually a controller both at the bottom of the tower and in 1088 the nacelle. The communication between these two controllers usually 1089 takes place using fiber optics instead of copper links. Sometimes, a 1090 third controller is installed in the hub of the rotor and manages the 1091 pitch of the blades. That unit usually communicates with the nacelle 1092 unit using serial communications. 1094 3.1.2.2.2. Inter-Domain network considerations 1096 A remote control center belonging to a grid operator regulates the 1097 power output, enables remote actuation, and monitors the health of 1098 one or more wind parks in tandem. It connects to the local control 1099 center in a wind park over the Internet (Figure 2) via firewalls at 1100 both ends. The AS path between the local control center and the Wind 1101 Park typically involves several ISPs at different tiers. For 1102 example, a remote control center in Denmark can regulate a wind park 1103 in Greece over the normal public AS path between the two locations. 1105 The remote control center is part of the SCADA system, setting the 1106 desired power output to the wind park and reading back the result 1107 once the new power output level has been set. Traffic between the 1108 remote control center and the wind park typically consists of 1109 protocols like IEC 60870-5-104 [IEC-60870-5-104], OPC XML-DA 1110 [OPCXML], Modbus [MODBUS], and SNMP [RFC3411]. Currently, traffic 1111 flows between the wind farm and the remote control center are best 1112 effort. QoS requirements are not strict, so no SLAs or service 1113 provisioning mechanisms (e.g., VPN) are employed. In case of events 1114 like equipment failure, tolerance for alarm delay is on the order of 1115 minutes, due to redundant systems already in place. 1117 +--------------+ 1118 | | 1119 | | 1120 | Wind Park #1 +----+ 1121 | | | XXXXXX 1122 | | | X XXXXXXXX +----------------+ 1123 +--------------+ | XXXX X XXXXX | | 1124 +---+ XXX | Remote Control | 1125 XXX Internet +----+ Center | 1126 +----+X XXX | | 1127 +--------------+ | XXXXXXX XX | | 1128 | | | XX XXXXXXX +----------------+ 1129 | | | XXXXX 1130 | Wind Park #2 +----+ 1131 | | 1132 | | 1133 +--------------+ 1135 Figure 2: Wind Turbine Control via Internet 1137 We expect future use cases which require bounded latency, bounded 1138 jitter and extraordinary low packet loss for inter-domain traffic 1139 flows due to the softwarization and virtualization of core wind farm 1140 equipment (e.g. switches, firewalls and SCADA server components). 1141 These factors will create opportunities for service providers to 1142 install new services and dynamically manage them from remote 1143 locations. For example, to enable fail-over of a local SCADA server, 1144 a SCADA server in another wind farm site (under the administrative 1145 control of the same operator) could be utilized temporarily 1146 (Figure 3). In that case local traffic would be forwarded to the 1147 remote SCADA server and existing intra-domain QoS and timing 1148 parameters would have to be met for inter-domain traffic flows. 1150 +--------------+ 1151 | | 1152 | | 1153 | Wind Park #1 +----+ 1154 | | | XXXXXX 1155 | | | X XXXXXXXX +----------------+ 1156 +--------------+ | XXXX XXXXX | | 1157 +---+ Operator XXX | Remote Control | 1158 XXX Administered +----+ Center | 1159 +----+X WAN XXX | | 1160 +--------------+ | XXXXXXX XX | | 1161 | | | XX XXXXXXX +----------------+ 1162 | | | XXXXX 1163 | Wind Park #2 +----+ 1164 | | 1165 | | 1166 +--------------+ 1168 Figure 3: Wind Turbine Control via Operator Administered WAN 1170 3.1.3. Distribution use case 1172 3.1.3.1. Fault Location Isolation and Service Restoration (FLISR) 1174 Fault Location, Isolation, and Service Restoration (FLISR) refers to 1175 the ability to automatically locate the fault, isolate the fault, and 1176 restore service in the distribution network. This will likely be the 1177 first widespread application of distributed intelligence in the grid. 1179 Static power switch status (open/closed) in the network dictates the 1180 power flow to secondary substations. Reconfiguring the network in 1181 the event of a fault is typically done manually on site to energize/ 1182 de-energize alternate paths. Automating the operation of substation 1183 switchgear allows the flow of power to be altered automatically under 1184 fault conditions. 1186 FLISR can be managed centrally from a Distribution Management System 1187 (DMS) or executed locally through distributed control via intelligent 1188 switches and fault sensors. 1190 +----------------------+--------------------------------------------+ 1191 | FLISR Requirement | Attribute | 1192 +----------------------+--------------------------------------------+ 1193 | One way maximum | 80 ms | 1194 | delay | | 1195 | Asymetric delay | No | 1196 | Required | | 1197 | Maximum jitter | 40 ms | 1198 | Topology | Point to point, point to Multi-point, | 1199 | | Multi-point to Multi-point | 1200 | Bandwidth | 64 Kbps | 1201 | Availability | 99.9999 | 1202 | precise timing | Yes | 1203 | required | | 1204 | Recovery time on | Depends on customer impact | 1205 | Node failure | | 1206 | performance | Yes, Mandatory | 1207 | management | | 1208 | Redundancy | Yes | 1209 | Packet loss | 0.1% | 1210 +----------------------+--------------------------------------------+ 1212 Table 12: FLISR Communication Requirements 1214 3.2. Electrical Utilities Today 1216 Many utilities still rely on complex environments formed of multiple 1217 application-specific proprietary networks, including TDM networks. 1219 In this kind of environment there is no mixing of OT and IT 1220 applications on the same network, and information is siloed between 1221 operational areas. 1223 Specific calibration of the full chain is required, which is costly. 1225 This kind of environment prevents utility operations from realizing 1226 the operational efficiency benefits, visibility, and functional 1227 integration of operational information across grid applications and 1228 data networks. 1230 In addition, there are many security-related issues as discussed in 1231 the following section. 1233 3.2.1. Security Current Practices and Limitations 1235 Grid monitoring and control devices are already targets for cyber 1236 attacks, and legacy telecommunications protocols have many intrinsic 1237 network-related vulnerabilities. For example, DNP3, Modbus, 1238 PROFIBUS/PROFINET, and other protocols are designed around a common 1239 paradigm of request and respond. Each protocol is designed for a 1240 master device such as an HMI (Human Machine Interface) system to send 1241 commands to subordinate slave devices to retrieve data (reading 1242 inputs) or control (writing to outputs). Because many of these 1243 protocols lack authentication, encryption, or other basic security 1244 measures, they are prone to network-based attacks, allowing a 1245 malicious actor or attacker to utilize the request-and-respond system 1246 as a mechanism for command-and-control like functionality. Specific 1247 security concerns common to most industrial control, including 1248 utility telecommunication protocols include the following: 1250 o Network or transport errors (e.g. malformed packets or excessive 1251 latency) can cause protocol failure. 1253 o Protocol commands may be available that are capable of forcing 1254 slave devices into inoperable states, including powering-off 1255 devices, forcing them into a listen-only state, disabling 1256 alarming. 1258 o Protocol commands may be available that are capable of restarting 1259 communications and otherwise interrupting processes. 1261 o Protocol commands may be available that are capable of clearing, 1262 erasing, or resetting diagnostic information such as counters and 1263 diagnostic registers. 1265 o Protocol commands may be available that are capable of requesting 1266 sensitive information about the controllers, their configurations, 1267 or other need-to-know information. 1269 o Most protocols are application layer protocols transported over 1270 TCP; therefore it is easy to transport commands over non-standard 1271 ports or inject commands into authorized traffic flows. 1273 o Protocol commands may be available that are capable of 1274 broadcasting messages to many devices at once (i.e. a potential 1275 DoS). 1277 o Protocol commands may be available to query the device network to 1278 obtain defined points and their values (i.e. a configuration 1279 scan). 1281 o Protocol commands may be available that will list all available 1282 function codes (i.e. a function scan). 1284 These inherent vulnerabilities, along with increasing connectivity 1285 between IT an OT networks, make network-based attacks very feasible. 1287 Simple injection of malicious protocol commands provides control over 1288 the target process. Altering legitimate protocol traffic can also 1289 alter information about a process and disrupt the legitimate controls 1290 that are in place over that process. A man-in-the-middle attack 1291 could provide both control over a process and misrepresentation of 1292 data back to operator consoles. 1294 3.3. Electrical Utilities Future 1296 The business and technology trends that are sweeping the utility 1297 industry will drastically transform the utility business from the way 1298 it has been for many decades. At the core of many of these changes 1299 is a drive to modernize the electrical grid with an integrated 1300 telecommunications infrastructure. However, interoperability 1301 concerns, legacy networks, disparate tools, and stringent security 1302 requirements all add complexity to the grid transformation. Given 1303 the range and diversity of the requirements that should be addressed 1304 by the next generation telecommunications infrastructure, utilities 1305 need to adopt a holistic architectural approach to integrate the 1306 electrical grid with digital telecommunications across the entire 1307 power delivery chain. 1309 The key to modernizing grid telecommunications is to provide a 1310 common, adaptable, multi-service network infrastructure for the 1311 entire utility organization. Such a network serves as the platform 1312 for current capabilities while enabling future expansion of the 1313 network to accommodate new applications and services. 1315 To meet this diverse set of requirements, both today and in the 1316 future, the next generation utility telecommunnications network will 1317 be based on open-standards-based IP architecture. An end-to-end IP 1318 architecture takes advantage of nearly three decades of IP technology 1319 development, facilitating interoperability and device management 1320 across disparate networks and devices, as it has been already 1321 demonstrated in many mission-critical and highly secure networks. 1323 IPv6 is seen as a future telecommunications technology for the Smart 1324 Grid; the IEC (International Electrotechnical Commission) and 1325 different National Committees have mandated a specific adhoc group 1326 (AHG8) to define the migration strategy to IPv6 for all the IEC TC57 1327 power automation standards. The AHG8 has recently finalised the work 1328 on the migration strategy and the following Technical Report has been 1329 issued: IEC TR 62357-200:2015: Guidelines for migration from Internet 1330 Protocol version 4 (IPv4) to Internet Protocol version 6 (IPv6). 1332 We expect cloud-based SCADA systems to control and monitor the 1333 critical and non-critical subsystems of generation systems, for 1334 example wind farms. 1336 3.3.1. Migration to Packet-Switched Network 1338 Throughout the world, utilities are increasingly planning for a 1339 future based on smart grid applications requiring advanced 1340 telecommunications systems. Many of these applications utilize 1341 packet connectivity for communicating information and control signals 1342 across the utility's Wide Area Network (WAN), made possible by 1343 technologies such as multiprotocol label switching (MPLS). The data 1344 that traverses the utility WAN includes: 1346 o Grid monitoring, control, and protection data 1348 o Non-control grid data (e.g. asset data for condition-based 1349 monitoring) 1351 o Physical safety and security data (e.g. voice and video) 1353 o Remote worker access to corporate applications (voice, maps, 1354 schematics, etc.) 1356 o Field area network backhaul for smart metering, and distribution 1357 grid management 1359 o Enterprise traffic (email, collaboration tools, business 1360 applications) 1362 WANs support this wide variety of traffic to and from substations, 1363 the transmission and distribution grid, generation sites, between 1364 control centers, and between work locations and data centers. To 1365 maintain this rapidly expanding set of applications, many utilities 1366 are taking steps to evolve present time-division multiplexing (TDM) 1367 based and frame relay infrastructures to packet systems. Packet- 1368 based networks are designed to provide greater functionalities and 1369 higher levels of service for applications, while continuing to 1370 deliver reliability and deterministic (real-time) traffic support. 1372 3.3.2. Telecommunications Trends 1374 These general telecommunications topics are in addition to the use 1375 cases that have been addressed so far. These include both current 1376 and future telecommunications related topics that should be factored 1377 into the network architecture and design. 1379 3.3.2.1. General Telecommunications Requirements 1381 o IP Connectivity everywhere 1383 o Monitoring services everywhere and from different remote centers 1384 o Move services to a virtual data center 1386 o Unify access to applications / information from the corporate 1387 network 1389 o Unify services 1391 o Unified Communications Solutions 1393 o Mix of fiber and microwave technologies - obsolescence of SONET/ 1394 SDH or TDM 1396 o Standardize grid telecommunications protocol to opened standard to 1397 ensure interoperability 1399 o Reliable Telecommunications for Transmission and Distribution 1400 Substations 1402 o IEEE 1588 time synchronization Client / Server Capabilities 1404 o Integration of Multicast Design 1406 o QoS Requirements Mapping 1408 o Enable Future Network Expansion 1410 o Substation Network Resilience 1412 o Fast Convergence Design 1414 o Scalable Headend Design 1416 o Define Service Level Agreements (SLA) and Enable SLA Monitoring 1418 o Integration of 3G/4G Technologies and future technologies 1420 o Ethernet Connectivity for Station Bus Architecture 1422 o Ethernet Connectivity for Process Bus Architecture 1424 o Protection, teleprotection and PMU (Phaser Measurement Unit) on IP 1426 3.3.2.2. Specific Network topologies of Smart Grid Applications 1428 Utilities often have very large private telecommunications networks. 1429 It covers an entire territory / country. The main purpose of the 1430 network, until now, has been to support transmission network 1431 monitoring, control, and automation, remote control of generation 1432 sites, and providing FCAPS (Fault, Configuration, Accounting, 1433 Performance, Security) services from centralized network operation 1434 centers. 1436 Going forward, one network will support operation and maintenance of 1437 electrical networks (generation, transmission, and distribution), 1438 voice and data services for ten of thousands of employees and for 1439 exchange with neighboring interconnections, and administrative 1440 services. To meet those requirements, utility may deploy several 1441 physical networks leveraging different technologies across the 1442 country: an optical network and a microwave network for instance. 1443 Each protection and automatism system between two points has two 1444 telecommunications circuits, one on each network. Path diversity 1445 between two substations is key. Regardless of the event type 1446 (hurricane, ice storm, etc.), one path shall stay available so the 1447 system can still operate. 1449 In the optical network, signals are transmitted over more than tens 1450 of thousands of circuits using fiber optic links, microwave and 1451 telephone cables. This network is the nervous system of the 1452 utility's power transmission operations. The optical network 1453 represents ten of thousands of km of cable deployed along the power 1454 lines, with individual runs as long as 280 km. 1456 3.3.2.3. Precision Time Protocol 1458 Some utilities do not use GPS clocks in generation substations. One 1459 of the main reasons is that some of the generation plants are 30 to 1460 50 meters deep under ground and the GPS signal can be weak and 1461 unreliable. Instead, atomic clocks are used. Clocks are 1462 synchronized amongst each other. Rubidium clocks provide clock and 1463 1ms timestamps for IRIG-B. 1465 Some companies plan to transition to the Precision Time Protocol 1466 (PTP, [IEEE1588]), distributing the synchronization signal over the 1467 IP/MPLS network. PTP provides a mechanism for synchronizing the 1468 clocks of participating nodes to a high degree of accuracy and 1469 precision. 1471 PTP operates based on the following assumptions: 1473 It is assumed that the network eliminates cyclic forwarding of PTP 1474 messages within each communication path (e.g. by using a spanning 1475 tree protocol). 1477 PTP is tolerant of an occasional missed message, duplicated 1478 message, or message that arrived out of order. However, PTP 1479 assumes that such impairments are relatively rare. 1481 PTP was designed assuming a multicast communication model, however 1482 PTP also supports a unicast communication model as long as the 1483 behavior of the protocol is preserved. 1485 Like all message-based time transfer protocols, PTP time accuracy 1486 is degraded by delay asymmetry in the paths taken by event 1487 messages. Asymmetry is not detectable by PTP, however, if such 1488 delays are known a priori, PTP can correct for asymmetry. 1490 IEC 61850 defines the use of IEC/IEEE 61850-9-3:2016. The title is: 1491 Precision time protocol profile for power utility automation. It is 1492 based on Annex B/IEC 62439 which offers the support of redundant 1493 attachment of clocks to Parallel Redundancy Protocol (PRP) and High- 1494 availability Seamless Redundancy (HSR) networks. 1496 3.3.3. Security Trends in Utility Networks 1498 Although advanced telecommunications networks can assist in 1499 transforming the energy industry by playing a critical role in 1500 maintaining high levels of reliability, performance, and 1501 manageability, they also introduce the need for an integrated 1502 security infrastructure. Many of the technologies being deployed to 1503 support smart grid projects such as smart meters and sensors can 1504 increase the vulnerability of the grid to attack. Top security 1505 concerns for utilities migrating to an intelligent smart grid 1506 telecommunications platform center on the following trends: 1508 o Integration of distributed energy resources 1510 o Proliferation of digital devices to enable management, automation, 1511 protection, and control 1513 o Regulatory mandates to comply with standards for critical 1514 infrastructure protection 1516 o Migration to new systems for outage management, distribution 1517 automation, condition-based maintenance, load forecasting, and 1518 smart metering 1520 o Demand for new levels of customer service and energy management 1522 This development of a diverse set of networks to support the 1523 integration of microgrids, open-access energy competition, and the 1524 use of network-controlled devices is driving the need for a converged 1525 security infrastructure for all participants in the smart grid, 1526 including utilities, energy service providers, large commercial and 1527 industrial, as well as residential customers. Securing the assets of 1528 electric power delivery systems (from the control center to the 1529 substation, to the feeders and down to customer meters) requires an 1530 end-to-end security infrastructure that protects the myriad of 1531 telecommunications assets used to operate, monitor, and control power 1532 flow and measurement. 1534 "Cyber security" refers to all the security issues in automation and 1535 telecommunications that affect any functions related to the operation 1536 of the electric power systems. Specifically, it involves the 1537 concepts of: 1539 o Integrity : data cannot be altered undetectably 1541 o Authenticity : the telecommunications parties involved must be 1542 validated as genuine 1544 o Authorization : only requests and commands from the authorized 1545 users can be accepted by the system 1547 o Confidentiality : data must not be accessible to any 1548 unauthenticated users 1550 When designing and deploying new smart grid devices and 1551 telecommunications systems, it is imperative to understand the 1552 various impacts of these new components under a variety of attack 1553 situations on the power grid. Consequences of a cyber attack on the 1554 grid telecommunications network can be catastrophic. This is why 1555 security for smart grid is not just an ad hoc feature or product, 1556 it's a complete framework integrating both physical and Cyber 1557 security requirements and covering the entire smart grid networks 1558 from generation to distribution. Security has therefore become one 1559 of the main foundations of the utility telecom network architecture 1560 and must be considered at every layer with a defense-in-depth 1561 approach. Migrating to IP based protocols is key to address these 1562 challenges for two reasons: 1564 o IP enables a rich set of features and capabilities to enhance the 1565 security posture 1567 o IP is based on open standards, which allows interoperability 1568 between different vendors and products, driving down the costs 1569 associated with implementing security solutions in OT networks. 1571 Securing OT (Operation technology) telecommunications over packet- 1572 switched IP networks follow the same principles that are foundational 1573 for securing the IT infrastructure, i.e., consideration must be given 1574 to enforcing electronic access control for both person-to-machine and 1575 machine-to-machine communications, and providing the appropriate 1576 levels of data privacy, device and platform integrity, and threat 1577 detection and mitigation. 1579 3.4. Electrical Utilities Asks 1581 o Mixed L2 and L3 topologies 1583 o Deterministic behavior 1585 o Bounded latency and jitter 1587 o Tight feedback intervals 1589 o High availability, low recovery time 1591 o Redundancy, low packet loss 1593 o Precise timing 1595 o Centralized computing of deterministic paths 1597 o Distributed configuration may also be useful 1599 4. Building Automation Systems 1601 4.1. Use Case Description 1603 A Building Automation System (BAS) manages equipment and sensors in a 1604 building for improving residents' comfort, reducing energy 1605 consumption, and responding to failures and emergencies. For 1606 example, the BAS measures the temperature of a room using sensors and 1607 then controls the HVAC (heating, ventilating, and air conditioning) 1608 to maintain a set temperature and minimize energy consumption. 1610 A BAS primarily performs the following functions: 1612 o Periodically measures states of devices, for example humidity and 1613 illuminance of rooms, open/close state of doors, FAN speed, etc. 1615 o Stores the measured data. 1617 o Provides the measured data to BAS systems and operators. 1619 o Generates alarms for abnormal state of devices. 1621 o Controls devices (e.g. turn off room lights at 10:00 PM). 1623 4.2. Building Automation Systems Today 1625 4.2.1. BAS Architecture 1627 A typical BAS architecture of today is shown in Figure 4. 1629 +----------------------------+ 1630 | | 1631 | BMS HMI | 1632 | | | | 1633 | +----------------------+ | 1634 | | Management Network | | 1635 | +----------------------+ | 1636 | | | | 1637 | LC LC | 1638 | | | | 1639 | +----------------------+ | 1640 | | Field Network | | 1641 | +----------------------+ | 1642 | | | | | | 1643 | Dev Dev Dev Dev | 1644 | | 1645 +----------------------------+ 1647 BMS := Building Management Server 1648 HMI := Human Machine Interface 1649 LC := Local Controller 1651 Figure 4: BAS architecture 1653 There are typically two layers of network in a BAS. The upper one is 1654 called the Management Network and the lower one is called the Field 1655 Network. In management networks an IP-based communication protocol 1656 is used, while in field networks non-IP based communication protocols 1657 ("field protocols") are mainly used. Field networks have specific 1658 timing requirements, whereas management networks can be best-effort. 1660 A Human Machine Interface (HMI) is typically a desktop PC used by 1661 operators to monitor and display device states, send device control 1662 commands to Local Controllers (LCs), and configure building schedules 1663 (for example "turn off all room lights in the building at 10:00 PM"). 1665 A Building Management Server (BMS) performs the following operations. 1667 o Collect and store device states from LCs at regular intervals. 1669 o Send control values to LCs according to a building schedule. 1671 o Send an alarm signal to operators if it detects abnormal devices 1672 states. 1674 The BMS and HMI communicate with LCs via IP-based "management 1675 protocols" (see standards [bacnetip], [knx]). 1677 A LC is typically a Programmable Logic Controller (PLC) which is 1678 connected to several tens or hundreds of devices using "field 1679 protocols". An LC performs the following kinds of operations: 1681 o Measure device states and provide the information to BMS or HMI. 1683 o Send control values to devices, unilaterally or as part of a 1684 feedback control loop. 1686 There are many field protocols used today; some are standards-based 1687 and others are proprietary (see standards [lontalk], [modbus], 1688 [profibus] and [flnet]). The result is that BASs have multiple MAC/ 1689 PHY modules and interfaces. This makes BASs more expensive, slower 1690 to develop, and can result in "vendor lock-in" with multiple types of 1691 management applications. 1693 4.2.2. BAS Deployment Model 1695 An example BAS for medium or large buildings is shown in Figure 5. 1696 The physical layout spans multiple floors, and there is a monitoring 1697 room where the BAS management entities are located. Each floor will 1698 have one or more LCs depending upon the number of devices connected 1699 to the field network. 1701 +--------------------------------------------------+ 1702 | Floor 3 | 1703 | +----LC~~~~+~~~~~+~~~~~+ | 1704 | | | | | | 1705 | | Dev Dev Dev | 1706 | | | 1707 |--- | ------------------------------------------| 1708 | | Floor 2 | 1709 | +----LC~~~~+~~~~~+~~~~~+ Field Network | 1710 | | | | | | 1711 | | Dev Dev Dev | 1712 | | | 1713 |--- | ------------------------------------------| 1714 | | Floor 1 | 1715 | +----LC~~~~+~~~~~+~~~~~+ +-----------------| 1716 | | | | | | Monitoring Room | 1717 | | Dev Dev Dev | | 1718 | | | BMS HMI | 1719 | | Management Network | | | | 1720 | +--------------------------------+-----+ | 1721 | | | 1722 +--------------------------------------------------+ 1724 Figure 5: BAS Deployment model for Medium/Large Buildings 1726 Each LC is connected to the monitoring room via the Management 1727 network, and the management functions are performed within the 1728 building. In most cases, fast Ethernet (e.g. 100BASE-T) is used for 1729 the management network. Since the management network is non- 1730 realtime, use of Ethernet without quality of service is sufficient 1731 for today's deployment. 1733 In the field network a variety of physical interfaces such as RS232C 1734 and RS485 are used, which have specific timing requirements. Thus if 1735 a field network is to be replaced with an Ethernet or wireless 1736 network, such networks must support time-critical deterministic 1737 flows. 1739 In Figure 6, another deployment model is presented in which the 1740 management system is hosted remotely. This is becoming popular for 1741 small office and residential buildings in which a standalone 1742 monitoring system is not cost-effective. 1744 +---------------+ 1745 | Remote Center | 1746 | | 1747 | BMS HMI | 1748 +------------------------------------+ | | | | 1749 | Floor 2 | | +---+---+ | 1750 | +----LC~~~~+~~~~~+ Field Network| | | | 1751 | | | | | | Router | 1752 | | Dev Dev | +-------|-------+ 1753 | | | | 1754 |--- | ------------------------------| | 1755 | | Floor 1 | | 1756 | +----LC~~~~+~~~~~+ | | 1757 | | | | | | 1758 | | Dev Dev | | 1759 | | | | 1760 | | Management Network | WAN | 1761 | +------------------------Router-------------+ 1762 | | 1763 +------------------------------------+ 1765 Figure 6: Deployment model for Small Buildings 1767 Some interoperability is possible today in the Management Network, 1768 but not in today's field networks due to their non-IP-based design. 1770 4.2.3. Use Cases for Field Networks 1772 Below are use cases for Environmental Monitoring, Fire Detection, and 1773 Feedback Control, and their implications for field network 1774 performance. 1776 4.2.3.1. Environmental Monitoring 1778 The BMS polls each LC at a maximum measurement interval of 100ms (for 1779 example to draw a historical chart of 1 second granularity with a 10x 1780 sampling interval) and then performs the operations as specified by 1781 the operator. Each LC needs to measure each of its several hundred 1782 sensors once per measurement interval. Latency is not critical in 1783 this scenario as long as all sensor values are completed in the 1784 measurement interval. Availability is expected to be 99.999 %. 1786 4.2.3.2. Fire Detection 1788 On detection of a fire, the BMS must stop the HVAC, close the fire 1789 shutters, turn on the fire sprinklers, send an alarm, etc. There are 1790 typically ~10s of sensors per LC that BMS needs to manage. In this 1791 scenario the measurement interval is 10-50ms, the communication delay 1792 is 10ms, and the availability must be 99.9999 %. 1794 4.2.3.3. Feedback Control 1796 BAS systems utilize feedback control in various ways; the most time- 1797 critial is control of DC motors, which require a short feedback 1798 interval (1-5ms) with low communication delay (10ms) and jitter 1799 (1ms). The feedback interval depends on the characteristics of the 1800 device and a target quality of control value. There are typically 1801 ~10s of such devices per LC. 1803 Communication delay is expected to be less than 10ms, jitter less 1804 than 1ms while the availability must be 99.9999% . 1806 4.2.4. Security Considerations 1808 When BAS field networks were developed it was assumed that the field 1809 networks would always be physically isolated from external networks 1810 and therefore security was not a concern. In today's world many BASs 1811 are managed remotely and are thus connected to shared IP networks and 1812 so security is definitely a concern, yet security features are not 1813 available in the majority of BAS field network deployments . 1815 The management network, being an IP-based network, has the protocols 1816 available to enable network security, but in practice many BAS 1817 systems do not implement even the available security features such as 1818 device authentication or encryption for data in transit. 1820 4.3. BAS Future 1822 In the future we expect more fine-grained environmental monitoring 1823 and lower energy consumption, which will require more sensors and 1824 devices, thus requiring larger and more complex building networks. 1826 We expect building networks to be connected to or converged with 1827 other networks (Enterprise network, Home network, and Internet). 1829 Therefore better facilities for network management, control, 1830 reliability and security are critical in order to improve resident 1831 and operator convenience and comfort. For example the ability to 1832 monitor and control building devices via the internet would enable 1833 (for example) control of room lights or HVAC from a resident's 1834 desktop PC or phone application. 1836 4.4. BAS Asks 1838 The community would like to see an interoperable protocol 1839 specification that can satisfy the timing, security, availability and 1840 QoS constraints described above, such that the resulting converged 1841 network can replace the disparate field networks. Ideally this 1842 connectivity could extend to the open Internet. 1844 This would imply an architecture that can guarantee 1846 o Low communication delays (from <10ms to 100ms in a network of 1847 several hundred devices) 1849 o Low jitter (< 1 ms) 1851 o Tight feedback intervals (1ms - 10ms) 1853 o High network availability (up to 99.9999% ) 1855 o Availability of network data in disaster scenario 1857 o Authentication between management and field devices (both local 1858 and remote) 1860 o Integrity and data origin authentication of communication data 1861 between field and management devices 1863 o Confidentiality of data when communicated to a remote device 1865 5. Wireless for Industrial 1867 5.1. Use Case Description 1869 Wireless networks are useful for industrial applications, for example 1870 when portable, fast-moving or rotating objects are involved, and for 1871 the resource-constrained devices found in the Internet of Things 1872 (IoT). 1874 Such network-connected sensors, actuators, control loops (etc.) 1875 typically require that the underlying network support real-time 1876 quality of service (QoS), as well as specific classes of other 1877 network properties such as reliability, redundancy, and security. 1879 These networks may also contain very large numbers of devices, for 1880 example for factories, "big data" acquisition, and the IoT. Given 1881 the large numbers of devices installed, and the potential 1882 pervasiveness of the IoT, this is a huge and very cost-sensitive 1883 market. For example, a 1% cost reduction in some areas could save 1884 $100B 1886 5.1.1. Network Convergence using 6TiSCH 1888 Some wireless network technologies support real-time QoS, and are 1889 thus useful for these kinds of networks, but others do not. For 1890 example WiFi is pervasive but does not provide guaranteed timing or 1891 delivery of packets, and thus is not useful in this context. 1893 In this use case we focus on one specific wireless network technology 1894 which does provide the required deterministic QoS, which is "IPv6 1895 over the TSCH mode of IEEE 802.15.4e" (6TiSCH, where TSCH stands for 1896 "Time-Slotted Channel Hopping", see [I-D.ietf-6tisch-architecture], 1897 [IEEE802154], [IEEE802154e], and [RFC7554]). 1899 There are other deterministic wireless busses and networks available 1900 today, however they are imcompatible with each other, and 1901 incompatible with IP traffic (for example [ISA100], [WirelessHART]). 1903 Thus the primary goal of this use case is to apply 6TiSCH as a 1904 converged IP- and standards-based wireless network for industrial 1905 applications, i.e. to replace multiple proprietary and/or 1906 incompatible wireless networking and wireless network management 1907 standards. 1909 5.1.2. Common Protocol Development for 6TiSCH 1911 Today there are a number of protocols required by 6TiSCH which are 1912 still in development, and a second intent of this use case is to 1913 highlight the ways in which these "missing" protocols share goals in 1914 common with DetNet. Thus it is possible that some of the protocol 1915 technology developed for DetNet will also be applicable to 6TiSCH. 1917 These protocol goals are identified here, along with their 1918 relationship to DetNet. It is likely that ultimately the resulting 1919 protocols will not be identical, but will share design principles 1920 which contribute to the eficiency of enabling both DetNet and 6TiSCH. 1922 One such commonality is that although at a different time scale, in 1923 both TSN [IEEE802.1TSNTG] and TSCH a packet crosses the network from 1924 node to node follows a precise schedule, as a train that leaves 1925 intermediate stations at precise times along its path. This kind of 1926 operation reduces collisions, saves energy, and enables engineering 1927 the network for deterministic properties. 1929 Another commonality is remote monitoring and scheduling management of 1930 a TSCH network by a Path Computation Element (PCE) and Network 1931 Management Entity (NME). The PCE/NME manage timeslots and device 1932 resources in a manner that minimizes the interaction with and the 1933 load placed on resource-constrained devices. For example, a tiny IoT 1934 device may have just enough buffers to store one or a few IPv6 1935 packets, and will have limited bandwidth between peers such that it 1936 can maintain only a small amount of peer information, and will not be 1937 able to store many packets waiting to be forwarded. It is 1938 advantageous then for it to only be required to carry out the 1939 specific behavior assigned to it by the PCE/NME (as opposed to 1940 maintaining its own IP stack, for example). 1942 Note: Current WG discussion indicates that some peer-to-peer 1943 communication must be assumed, i.e. the PCE may communicate only 1944 indirectly with any given device, enabling hierarchical configuration 1945 of the system. 1947 6TiSCH depends on [PCE] and [I-D.ietf-detnet-architecture]. 1949 6TiSCH also depends on the fact that DetNet will maintain consistency 1950 with [IEEE802.1TSNTG]. 1952 5.2. Wireless Industrial Today 1954 Today industrial wireless is accomplished using multiple 1955 deterministic wireless networks which are incompatible with each 1956 other and with IP traffic. 1958 6TiSCH is not yet fully specified, so it cannot be used in today's 1959 applications. 1961 5.3. Wireless Industrial Future 1963 5.3.1. Unified Wireless Network and Management 1965 We expect DetNet and 6TiSCH together to enable converged transport of 1966 deterministic and best-effort traffic flows between real-time 1967 industrial devices and wide area networks via IP routing. A high 1968 level view of a basic such network is shown in Figure 7. 1970 ---+-------- ............ ------------ 1971 | External Network | 1972 | +-----+ 1973 +-----+ | NME | 1974 | | LLN Border | | 1975 | | router +-----+ 1976 +-----+ 1977 o o o 1978 o o o o 1979 o o LLN o o o 1980 o o o o 1981 o 1983 Figure 7: Basic 6TiSCH Network 1985 Figure 8 shows a backbone router federating multiple synchronized 1986 6TiSCH subnets into a single subnet connected to the external 1987 network. 1989 ---+-------- ............ ------------ 1990 | External Network | 1991 | +-----+ 1992 | +-----+ | NME | 1993 +-----+ | +-----+ | | 1994 | | Router | | PCE | +-----+ 1995 | | +--| | 1996 +-----+ +-----+ 1997 | | 1998 | Subnet Backbone | 1999 +--------------------+------------------+ 2000 | | | 2001 +-----+ +-----+ +-----+ 2002 | | Backbone | | Backbone | | Backbone 2003 o | | router | | router | | router 2004 +-----+ +-----+ +-----+ 2005 o o o o o 2006 o o o o o o o o o o o 2007 o o o LLN o o o o 2008 o o o o o o o o o o o o 2010 Figure 8: Extended 6TiSCH Network 2012 The backbone router must ensure end-to-end deterministic behavior 2013 between the LLN and the backbone. We would like to see this 2014 accomplished in conformance with the work done in 2015 [I-D.ietf-detnet-architecture] with respect to Layer-3 aspects of 2016 deterministic networks that span multiple Layer-2 domains. 2018 The PCE must compute a deterministic path end-to-end across the TSCH 2019 network and IEEE802.1 TSN Ethernet backbone, and DetNet protocols are 2020 expected to enable end-to-end deterministic forwarding. 2022 +-----+ 2023 | IoT | 2024 | G/W | 2025 +-----+ 2026 ^ <---- Elimination 2027 | | 2028 Track branch | | 2029 +-------+ +--------+ Subnet Backbone 2030 | | 2031 +--|--+ +--|--+ 2032 | | | Backbone | | | Backbone 2033 o | | | router | | | router 2034 +--/--+ +--|--+ 2035 o / o o---o----/ o 2036 o o---o--/ o o o o o 2037 o \ / o o LLN o 2038 o v <---- Replication 2039 o 2041 Figure 9: 6TiSCH Network with PRE 2043 5.3.1.1. PCE and 6TiSCH ARQ Retries 2045 Note: The possible use of ARQ techniques in DetNet is currently 2046 considered a possible design alternative. 2048 6TiSCH uses the IEEE802.15.4 Automatic Repeat-reQuest (ARQ) mechanism 2049 to provide higher reliability of packet delivery. ARQ is related to 2050 packet replication and elimination because there are two independent 2051 paths for packets to arrive at the destination, and if an expected 2052 packed does not arrive on one path then it checks for the packet on 2053 the second path. 2055 Although to date this mechanism is only used by wireless networks, 2056 this may be a technique that would be appropriate for DetNet and so 2057 aspects of the enabling protocol could be co-developed. 2059 For example, in Figure 9, a Track is laid out from a field device in 2060 a 6TiSCH network to an IoT gateway that is located on a IEEE802.1 TSN 2061 backbone. 2063 In ARQ the Replication function in the field device sends a copy of 2064 each packet over two different branches, and the PCE schedules each 2065 hop of both branches so that the two copies arrive in due time at the 2066 gateway. In case of a loss on one branch, hopefully the other copy 2067 of the packet still arrives within the allocated time. If two copies 2068 make it to the IoT gateway, the Elimination function in the gateway 2069 ignores the extra packet and presents only one copy to upper layers. 2071 At each 6TiSCH hop along the Track, the PCE may schedule more than 2072 one timeSlot for a packet, so as to support Layer-2 retries (ARQ). 2074 In current deployments, a TSCH Track does not necessarily support PRE 2075 but is systematically multi-path. This means that a Track is 2076 scheduled so as to ensure that each hop has at least two forwarding 2077 solutions, and the forwarding decision is to try the preferred one 2078 and use the other in case of Layer-2 transmission failure as detected 2079 by ARQ. 2081 5.3.2. Schedule Management by a PCE 2083 A common feature of 6TiSCH and DetNet is the action of a PCE to 2084 configure paths through the network. Specifically, what is needed is 2085 a protocol and data model that the PCE will use to get/set the 2086 relevant configuration from/to the devices, as well as perform 2087 operations on the devices. We expect that this protocol will be 2088 developed by DetNet with consideration for its reuse by 6TiSCH. The 2089 remainder of this section provides a bit more context from the 6TiSCH 2090 side. 2092 5.3.2.1. PCE Commands and 6TiSCH CoAP Requests 2094 The 6TiSCH device does not expect to place the request for bandwidth 2095 between itself and another device in the network. Rather, an 2096 operation control system invoked through a human interface specifies 2097 the required traffic specification and the end nodes (in terms of 2098 latency and reliability). Based on this information, the PCE must 2099 compute a path between the end nodes and provision the network with 2100 per-flow state that describes the per-hop operation for a given 2101 packet, the corresponding timeslots, and the flow identification that 2102 enables recognizing that a certain packet belongs to a certain path, 2103 etc. 2105 For a static configuration that serves a certain purpose for a long 2106 period of time, it is expected that a node will be provisioned in one 2107 shot with a full schedule, which incorporates the aggregation of its 2108 behavior for multiple paths. 6TiSCH expects that the programing of 2109 the schedule will be done over COAP as discussed in 2110 [I-D.ietf-6tisch-coap]. 2112 6TiSCH expects that the PCE commands will be mapped back and forth 2113 into CoAP by a gateway function at the edge of the 6TiSCH network. 2114 For instance, it is possible that a mapping entity on the backbone 2115 transforms a non-CoAP protocol such as PCEP into the RESTful 2116 interfaces that the 6TiSCH devices support. This architecture will 2117 be refined to comply with DetNet [I-D.ietf-detnet-architecture] when 2118 the work is formalized. Related information about 6TiSCH can be 2119 found at [I-D.ietf-6tisch-6top-interface] and RPL [RFC6550]. 2121 A protocol may be used to update the state in the devices during 2122 runtime, for example if it appears that a path through the network 2123 has ceased to perform as expected, but in 6TiSCH that flow was not 2124 designed and no protocol was selected. We would like to see DetNet 2125 define the appropriate end-to-end protocols to be used in that case. 2126 The implication is that these state updates take place once the 2127 system is configured and running, i.e. they are not limited to the 2128 initial communication of the configuration of the system. 2130 A "slotFrame" is the base object that a PCE would manipulate to 2131 program a schedule into an LLN node ([I-D.ietf-6tisch-architecture]). 2133 We would like to see the PCE read energy data from devices, and 2134 compute paths that will implement policies on how energy in devices 2135 is consumed, for instance to ensure that the spent energy does not 2136 exceeded the available energy over a period of time. Note: this 2137 statement implies that an extensible protocol for communicating 2138 device info to the PCE and enabling the PCE to act on it will be part 2139 of the DetNet architecture, however for subnets with specific 2140 protocols (e.g. CoAP) a gateway may be required. 2142 6TiSCH devices can discover their neighbors over the radio using a 2143 mechanism such as beacons, but even though the neighbor information 2144 is available in the 6TiSCH interface data model, 6TiSCH does not 2145 describe a protocol to proactively push the neighborhood information 2146 to a PCE. We would like to see DetNet define such a protocol; one 2147 possible design alternative is that it could operate over CoAP, 2148 alternatively it could be converted to/from CoAP by a gateway. We 2149 would like to see such a protocol carry multiple metrics, for example 2150 similar to those used for RPL operations [RFC6551] 2152 5.3.2.2. 6TiSCH IP Interface 2154 "6top" ([I-D.wang-6tisch-6top-sublayer]) is a logical link control 2155 sitting between the IP layer and the TSCH MAC layer which provides 2156 the link abstraction that is required for IP operations. The 6top 2157 data model and management interfaces are further discussed in 2158 [I-D.ietf-6tisch-6top-interface] and [I-D.ietf-6tisch-coap]. 2160 An IP packet that is sent along a 6TiSCH path uses the Differentiated 2161 Services Per-Hop-Behavior Group called Deterministic Forwarding, as 2162 described in [I-D.svshah-tsvwg-deterministic-forwarding]. 2164 5.3.3. 6TiSCH Security Considerations 2166 On top of the classical requirements for protection of control 2167 signaling, it must be noted that 6TiSCH networks operate on limited 2168 resources that can be depleted rapidly in a DoS attack on the system, 2169 for instance by placing a rogue device in the network, or by 2170 obtaining management control and setting up unexpected additional 2171 paths. 2173 5.4. Wireless Industrial Asks 2175 6TiSCH depends on DetNet to define: 2177 o Configuration (state) and operations for deterministic paths 2179 o End-to-end protocols for deterministic forwarding (tagging, IP) 2181 o Protocol for packet replication and elimination 2183 6. Cellular Radio 2185 6.1. Use Case Description 2187 This use case describes the application of deterministic networking 2188 in the context of cellular telecom transport networks. Important 2189 elements include time synchronization, clock distribution, and ways 2190 of establishing time-sensitive streams for both Layer-2 and Layer-3 2191 user plane traffic. 2193 6.1.1. Network Architecture 2195 Figure 10 illustrates a typical 3GPP-defined cellular network 2196 architecture, which includes "Fronthaul", "Midhaul" and "Backhaul" 2197 network segments. The "Fronthaul" is the network connecting base 2198 stations (baseband processing units) to the remote radio heads 2199 (antennas). The "Midhaul" is the network inter-connecting base 2200 stations (or small cell sites). The "Backhaul" is the network or 2201 links connecting the radio base station sites to the network 2202 controller/gateway sites (i.e. the core of the 3GPP cellular 2203 network). 2205 In Figure 10 "eNB" ("E-UTRAN Node B") is the hardware that is 2206 connected to the mobile phone network which communicates directly 2207 with mobile handsets ([TS36300]). 2209 Y (remote radio heads (antennas)) 2210 \ 2211 Y__ \.--. .--. +------+ 2212 \_( `. +---+ _(Back`. | 3GPP | 2213 Y------( Front )----|eNB|----( Haul )----| core | 2214 ( ` .Haul ) +---+ ( ` . ) ) | netw | 2215 /`--(___.-' \ `--(___.-' +------+ 2216 Y_/ / \.--. \ 2217 Y_/ _( Mid`. \ 2218 ( Haul ) \ 2219 ( ` . ) ) \ 2220 `--(___.-'\_____+---+ (small cell sites) 2221 \ |SCe|__Y 2222 +---+ +---+ 2223 Y__|eNB|__Y 2224 +---+ 2225 Y_/ \_Y ("local" radios) 2227 Figure 10: Generic 3GPP-based Cellular Network Architecture 2229 6.1.2. Delay Constraints 2231 The available processing time for Fronthaul networking overhead is 2232 limited to the available time after the baseband processing of the 2233 radio frame has completed. For example in Long Term Evolution (LTE) 2234 radio, processing of a radio frame is allocated 3ms but typically the 2235 processing uses most of it, allowing only a small fraction to be used 2236 by the Fronthaul network (e.g. up to 250us one-way delay, though the 2237 existing spec ([NGMN-fronth]) supports delay only up to 100us). This 2238 ultimately determines the distance the remote radio heads can be 2239 located from the base stations (e.g., 100us equals roughly 20 km of 2240 optical fiber-based transport). Allocation options of the available 2241 time budget between processing and transport are under heavy 2242 discussions in the mobile industry. 2244 For packet-based transport the allocated transport time (e.g. CPRI 2245 would allow for 100us delay [CPRI]) is consumed by all nodes and 2246 buffering between the remote radio head and the baseband processing 2247 unit, plus the distance-incurred delay. 2249 The baseband processing time and the available "delay budget" for the 2250 fronthaul is likely to change in the forthcoming "5G" due to reduced 2251 radio round trip times and other architectural and service 2252 requirements [NGMN]. 2254 The transport time budget, as noted above, places limitations on the 2255 distance that remote radio heads can be located from base stations 2256 (i.e. the link length). In the above analysis, the entire transport 2257 time budget is assumed to be available for link propagation delay. 2258 However the transport time budget can be broken down into three 2259 components: scheduling /queueing delay, transmission delay, and link 2260 propagation delay. Using today's Fronthaul networking technology, 2261 the queuing, scheduling and transmission components might become the 2262 dominant factors in the total transport time rather than the link 2263 propagation delay. This is especially true in cases where the 2264 Fronthaul link is relatively short and it is shared among multiple 2265 Fronthaul flows, for example in indoor and small cell networks, 2266 massive MIMO antenna networks, and split Fronthaul architectures. 2268 DetNet technology can improve this application by controlling and 2269 reducing the time required for the queuing, scheduling and 2270 transmission operations by properly assigning the network resources, 2271 thus leaving more of the transport time budget available for link 2272 propagation, and thus enabling longer link lengths. However, link 2273 length is usually a given parameter and is not a controllable network 2274 parameter, since RRH and BBU sights are usually located in 2275 predetermined locations. However, the number of antennas in an RRH 2276 sight might increase for example by adding more antennas, increasing 2277 the MIMO capability of the network or support of massive MIMO. This 2278 means increasing the number of the fronthaul flows sharing the same 2279 fronthaul link. DetNet can now control the bandwidth assignment of 2280 the fronthaul link and the scheduling of fronthaul packets over this 2281 link and provide adequate buffer provisioning for each flow to reduce 2282 the packet loss rate. 2284 Another way in which DetNet technology can aid Fronthaul networks is 2285 by providing effective isolation from best-effort (and other classes 2286 of) traffic, which can arise as a result of network slicing in 5G 2287 networks where Fronthaul traffic generated in different network 2288 slices might have differing performance requirements. DetNet 2289 technology can also dynamically control the bandwidth assignment, 2290 scheduling and packet forwarding decisions and the buffer 2291 provisioning of the Fronthaul flows to guarantee the end-to-end delay 2292 of the Fronthaul packets and minimize the packet loss rate. 2294 [METIS] documents the fundamental challenges as well as overall 2295 technical goals of the future 5G mobile and wireless system as the 2296 starting point. These future systems should support much higher data 2297 volumes and rates and significantly lower end-to-end latency for 100x 2298 more connected devices (at similar cost and energy consumption levels 2299 as today's system). 2301 For Midhaul connections, delay constraints are driven by Inter-Site 2302 radio functions like Coordinated Multipoint Processing (CoMP, see 2303 [CoMP]). CoMP reception and transmission is a framework in which 2304 multiple geographically distributed antenna nodes cooperate to 2305 improve the performance of the users served in the common cooperation 2306 area. The design principal of CoMP is to extend the current single- 2307 cell to multi-UE (User Equipment) transmission to a multi-cell-to- 2308 multi-UEs transmission by base station cooperation. 2310 CoMP has delay-sensitive performance parameters, which are "midhaul 2311 latency" and "CSI (Channel State Information) reporting and 2312 accuracy". The essential feature of CoMP is signaling between eNBs, 2313 so Midhaul latency is the dominating limitation of CoMP performance. 2314 Generally, CoMP can benefit from coordinated scheduling (either 2315 distributed or centralized) of different cells if the signaling delay 2316 between eNBs is within 1-10ms. This delay requirement is both rigid 2317 and absolute because any uncertainty in delay will degrade the 2318 performance significantly. 2320 Inter-site CoMP is one of the key requirements for 5G and is also a 2321 near-term goal for the current 4.5G network architecture. 2323 6.1.3. Time Synchronization Constraints 2325 Fronthaul time synchronization requirements are given by [TS25104], 2326 [TS36104], [TS36211], and [TS36133]. These can be summarized for the 2327 current 3GPP LTE-based networks as: 2329 Delay Accuracy: 2330 +-8ns (i.e. +-1/32 Tc, where Tc is the UMTS Chip time of 1/3.84 2331 MHz) resulting in a round trip accuracy of +-16ns. The value is 2332 this low to meet the 3GPP Timing Alignment Error (TAE) measurement 2333 requirements. Note: performance guarantees of low nanosecond 2334 values such as these are considered to be below the DetNet layer - 2335 it is assumed that the underlying implementation, e.g. the 2336 hardware, will provide sufficient support (e.g. buffering) to 2337 enable this level of accuracy. These values are maintained in the 2338 use case to give an indication of the overall application. 2340 Timing Alignment Error: 2341 Timing Alignment Error (TAE) is problematic to Fronthaul networks 2342 and must be minimized. If the transport network cannot guarantee 2343 low enough TAE then additional buffering has to be introduced at 2344 the edges of the network to buffer out the jitter. Buffering is 2345 not desirable as it reduces the total available delay budget. 2346 Packet Delay Variation (PDV) requirements can be derived from TAE 2347 for packet based Fronthaul networks. 2349 * For multiple input multiple output (MIMO) or TX diversity 2350 transmissions, at each carrier frequency, TAE shall not exceed 2351 65 ns (i.e. 1/4 Tc). 2353 * For intra-band contiguous carrier aggregation, with or without 2354 MIMO or TX diversity, TAE shall not exceed 130 ns (i.e. 1/2 2355 Tc). 2357 * For intra-band non-contiguous carrier aggregation, with or 2358 without MIMO or TX diversity, TAE shall not exceed 260 ns (i.e. 2359 one Tc). 2361 * For inter-band carrier aggregation, with or without MIMO or TX 2362 diversity, TAE shall not exceed 260 ns. 2364 Transport link contribution to radio frequency error: 2365 +-2 PPB. This value is considered to be "available" for the 2366 Fronthaul link out of the total 50 PPB budget reserved for the 2367 radio interface. Note: the reason that the transport link 2368 contributes to radio frequency error is as follows. The current 2369 way of doing Fronthaul is from the radio unit to remote radio head 2370 directly. The remote radio head is essentially a passive device 2371 (without buffering etc.) The transport drives the antenna 2372 directly by feeding it with samples and everything the transport 2373 adds will be introduced to radio as-is. So if the transport 2374 causes additional frequency error that shows immediately on the 2375 radio as well. Note: performance guarantees of low nanosecond 2376 values such as these are considered to be below the DetNet layer - 2377 it is assumed that the underlying implementation, e.g. the 2378 hardware, will provide sufficient support to enable this level of 2379 performance. These values are maintained in the use case to give 2380 an indication of the overall application. 2382 The above listed time synchronization requirements are difficult to 2383 meet with point-to-point connected networks, and more difficult when 2384 the network includes multiple hops. It is expected that networks 2385 must include buffering at the ends of the connections as imposed by 2386 the jitter requirements, since trying to meet the jitter requirements 2387 in every intermediate node is likely to be too costly. However, 2388 every measure to reduce jitter and delay on the path makes it easier 2389 to meet the end-to-end requirements. 2391 In order to meet the timing requirements both senders and receivers 2392 must remain time synchronized, demanding very accurate clock 2393 distribution, for example support for IEEE 1588 transparent clocks or 2394 boundary clocks in every intermediate node. 2396 In cellular networks from the LTE radio era onward, phase 2397 synchronization is needed in addition to frequency synchronization 2398 ([TS36300], [TS23401]). Time constraints are also important due to 2399 their impact on packet loss. If a packet is delivered too late, then 2400 the packet may be dropped by the host. 2402 6.1.4. Transport Loss Constraints 2404 Fronthaul and Midhaul networks assume almost error-free transport. 2405 Errors can result in a reset of the radio interfaces, which can cause 2406 reduced throughput or broken radio connectivity for mobile customers. 2408 For packetized Fronthaul and Midhaul connections packet loss may be 2409 caused by BER, congestion, or network failure scenarios. Different 2410 fronthaul functional splits are being considered by 3GPP, requiring 2411 strict frame loss ratio (FLR) guarantees. As one example (referring 2412 to the legacy CPRI split which is option 8 in 3GPP) lower layers 2413 splits may imply an FLR of less than 10E-7 for data traffic and less 2414 than 10E-6 for control and management traffic. Current tools for 2415 eliminating packet loss for Fronthaul and Midhaul networks have 2416 serious challenges, for example retransmitting lost packets and/or 2417 using forward error correction (FEC) to circumvent bit errors is 2418 practically impossible due to the additional delay incurred. Using 2419 redundant streams for better guarantees for delivery is also 2420 practically impossible in many cases due to high bandwidth 2421 requirements of Fronthaul and Midhaul networks. Protection switching 2422 is also a candidate but current technologies for the path switch are 2423 too slow to avoid reset of mobile interfaces. 2425 Fronthaul links are assumed to be symmetric, and all Fronthaul 2426 streams (i.e. those carrying radio data) have equal priority and 2427 cannot delay or pre-empt each other. This implies that the network 2428 must guarantee that each time-sensitive flow meets their schedule. 2430 6.1.5. Security Considerations 2432 Establishing time-sensitive streams in the network entails reserving 2433 networking resources for long periods of time. It is important that 2434 these reservation requests be authenticated to prevent malicious 2435 reservation attempts from hostile nodes (or accidental 2436 misconfiguration). This is particularly important in the case where 2437 the reservation requests span administrative domains. Furthermore, 2438 the reservation information itself should be digitally signed to 2439 reduce the risk of a legitimate node pushing a stale or hostile 2440 configuration into another networking node. 2442 Note: This is considered important for the security policy of the 2443 network, but does not affect the core DetNet architecture and design. 2445 6.2. Cellular Radio Networks Today 2447 6.2.1. Fronthaul 2449 Today's Fronthaul networks typically consist of: 2451 o Dedicated point-to-point fiber connection is common 2453 o Proprietary protocols and framings 2455 o Custom equipment and no real networking 2457 Current solutions for Fronthaul are direct optical cables or 2458 Wavelength-Division Multiplexing (WDM) connections. 2460 6.2.2. Midhaul and Backhaul 2462 Today's Midhaul and Backhaul networks typically consist of: 2464 o Mostly normal IP networks, MPLS-TP, etc. 2466 o Clock distribution and sync using 1588 and SyncE 2468 Telecommunication networks in the Mid- and Backhaul are already 2469 heading towards transport networks where precise time synchronization 2470 support is one of the basic building blocks. While the transport 2471 networks themselves have practically transitioned to all-IP packet- 2472 based networks to meet the bandwidth and cost requirements, highly 2473 accurate clock distribution has become a challenge. 2475 In the past, Mid- and Backhaul connections were typically based on 2476 Time Division Multiplexing (TDM-based) and provided frequency 2477 synchronization capabilities as a part of the transport media. 2478 Alternatively other technologies such as Global Positioning System 2479 (GPS) or Synchronous Ethernet (SyncE) are used [SyncE]. 2481 Both Ethernet and IP/MPLS [RFC3031] (and PseudoWires (PWE) [RFC3985] 2482 for legacy transport support) have become popular tools to build and 2483 manage new all-IP Radio Access Networks (RANs) 2484 [I-D.kh-spring-ip-ran-use-case]. Although various timing and 2485 synchronization optimizations have already been proposed and 2486 implemented including 1588 PTP enhancements 2487 [I-D.ietf-tictoc-1588overmpls] and [I-D.ietf-mpls-residence-time], 2488 these solution are not necessarily sufficient for the forthcoming RAN 2489 architectures nor do they guarantee the more stringent time- 2490 synchronization requirements such as [CPRI]. 2492 There are also existing solutions for TDM over IP such as [RFC4553], 2493 [RFC5086], and [RFC5087], as well as TDM over Ethernet transports 2494 such as [MEF8]. 2496 6.3. Cellular Radio Networks Future 2498 Future Cellular Radio Networks will be based on a mix of different 2499 xHaul networks (xHaul = front-, mid- and backhaul), and future 2500 transport networks should be able to support all of them 2501 simultaneously. It is already envisioned today that: 2503 o Not all "cellular radio network" traffic will be IP, for example 2504 some will remain at Layer 2 (e.g. Ethernet based). DetNet 2505 solutions must address all traffic types (Layer 2, Layer 3) with 2506 the same tools and allow their transport simultaneously. 2508 o All forms of xHaul networks will need some form of DetNet 2509 solutions. For example with the advent of 5G some Backhaul 2510 traffic will also have DetNet requirements, for example traffic 2511 belonging to time-critical 5G applications. 2513 o Different splits of the functionality run on the base stations and 2514 the on-site units could co-exist on the same Fronthaul and 2515 Backhaul network. 2517 We would like to see the following in future Cellular Radio networks: 2519 o Unified standards-based transport protocols and standard 2520 networking equipment that can make use of underlying deterministic 2521 link-layer services 2523 o Unified and standards-based network management systems and 2524 protocols in all parts of the network (including Fronthaul) 2526 New radio access network deployment models and architectures may 2527 require time- sensitive networking services with strict requirements 2528 on other parts of the network that previously were not considered to 2529 be packetized at all. Time and synchronization support are already 2530 topical for Backhaul and Midhaul packet networks [MEF22.1.1] and are 2531 becoming a real issue for Fronthaul networks also. Specifically in 2532 Fronthaul networks the timing and synchronization requirements can be 2533 extreme for packet based technologies, for example, on the order of 2534 sub +-20 ns packet delay variation (PDV) and frequency accuracy of 2535 +0.002 PPM [Fronthaul]. 2537 The actual transport protocols and/or solutions to establish required 2538 transport "circuits" (pinned-down paths) for Fronthaul traffic are 2539 still undefined. Those are likely to include (but are not limited 2540 to) solutions directly over Ethernet, over IP, and using MPLS/ 2541 PseudoWire transport. 2543 Even the current time-sensitive networking features may not be 2544 sufficient for Fronthaul traffic. Therefore, having specific 2545 profiles that take the requirements of Fronthaul into account is 2546 desirable [IEEE8021CM]. 2548 Interesting and important work for time-sensitive networking has been 2549 done for Ethernet [TSNTG], which specifies the use of IEEE 1588 time 2550 precision protocol (PTP) [IEEE1588] in the context of IEEE 802.1D and 2551 IEEE 802.1Q. [IEEE8021AS] specifies a Layer 2 time synchronizing 2552 service, and other specifications such as IEEE 1722 [IEEE1722] 2553 specify Ethernet-based Layer-2 transport for time-sensitive streams. 2555 New promising work seeks to enable the transport of time-sensitive 2556 fronthaul streams in Ethernet bridged networks [IEEE8021CM]. 2557 Analogous to IEEE 1722 there is an ongoing standardization effort to 2558 define the Layer-2 transport encapsulation format for transporting 2559 radio over Ethernet (RoE) in the IEEE 1904.3 Task Force [IEEE19143]. 2561 As mentioned in Section 6.1.2, 5G communications will provide one of 2562 the most challenging cases for delay sensitive networking. In order 2563 to meet the challenges of ultra-low latency and ultra-high 2564 throughput, 3GPP has studied various "functional splits" for 5G, 2565 i.e., physical decomposition of the gNodeB base station and 2566 deployment of its functional blocks in different locations [TR38801]. 2568 These splits are numbered from split option 1 (Dual Connectivity, a 2569 split in which the radio resource control is centralized and other 2570 radio stack layers are in distributed units) to split option 8 (a 2571 PHY-RF split in which RF functionality is in a distributed unit and 2572 the rest of the radio stack is in the centralized unit), with each 2573 intermediate split having its own data rate and delay requirements. 2574 Packetized versions of different splits have recently been proposed 2575 including eCPRI [eCPRI] and RoE (as previously noted). Both provide 2576 Ethernet encapsulations, and eCPRI is also capable of IP 2577 encapsulation. 2579 All-IP RANs and xHaul networks would benefit from time 2580 synchronization and time-sensitive transport services. Although 2581 Ethernet appears to be the unifying technology for the transport, 2582 there is still a disconnect providing Layer 3 services. The protocol 2583 stack typically has a number of layers below the Ethernet Layer 2 2584 that shows up to the Layer 3 IP transport. It is not uncommon that 2585 on top of the lowest layer (optical) transport there is the first 2586 layer of Ethernet followed one or more layers of MPLS, PseudoWires 2587 and/or other tunneling protocols finally carrying the Ethernet layer 2588 visible to the user plane IP traffic. 2590 While there are existing technologies to establish circuits through 2591 the routed and switched networks (especially in MPLS/PWE space), 2592 there is still no way to signal the time synchronization and time- 2593 sensitive stream requirements/reservations for Layer-3 flows in a way 2594 that addresses the entire transport stack, including the Ethernet 2595 layers that need to be configured. 2597 Furthermore, not all "user plane" traffic will be IP. Therefore, the 2598 same solution also must address the use cases where the user plane 2599 traffic is a different layer, for example Ethernet frames. 2601 There is existing work describing the problem statement 2602 [I-D.ietf-detnet-problem-statement] and the architecture 2603 [I-D.ietf-detnet-architecture] for deterministic networking (DetNet) 2604 that targets solutions for time-sensitive (IP/transport) streams with 2605 deterministic properties over Ethernet-based switched networks. 2607 6.4. Cellular Radio Networks Asks 2609 A standard for data plane transport specification which is: 2611 o Unified among all xHauls (meaning that different flows with 2612 diverse DetNet requirements can coexist in the same network and 2613 traverse the same nodes without interfering with each other) 2615 o Deployed in a highly deterministic network environment 2617 o Capable of supporting multiple functional splits simultaneously, 2618 including existing Backhaul and CPRI Fronthaul and potentially new 2619 modes as defined for example in 3GPP; these goals can be supported 2620 by the existing DetNet Use Case Common Themes, notably "Mix of 2621 Deterministic and Best-Effort Traffic", "Bounded Latency", "Low 2622 Latency", "Symmetrical Path Delays", and "Deterministic Flows". 2624 o Capable of supporting Network Slicing and Multi-tenancy; these 2625 goals can be supported by the same DetNet themes noted above. 2627 o Capable of transporting both in-band and out-band control traffic 2628 (OAM info, ...). 2630 o Deployable over multiple data link technologies (e.g., IEEE 802.3, 2631 mmWave, etc.). 2633 A standard for data flow information models that are: 2635 o Aware of the time sensitivity and constraints of the target 2636 networking environment 2638 o Aware of underlying deterministic networking services (e.g., on 2639 the Ethernet layer) 2641 7. Industrial M2M 2643 7.1. Use Case Description 2645 Industrial Automation in general refers to automation of 2646 manufacturing, quality control and material processing. In this 2647 "machine to machine" (M2M) use case we consider machine units in a 2648 plant floor which periodically exchange data with upstream or 2649 downstream machine modules and/or a supervisory controller within a 2650 local area network. 2652 The actors of M2M communication are Programmable Logic Controllers 2653 (PLCs). Communication between PLCs and between PLCs and the 2654 supervisory PLC (S-PLC) is achieved via critical control/data streams 2655 Figure 11. 2657 S (Sensor) 2658 \ +-----+ 2659 PLC__ \.--. .--. ---| MES | 2660 \_( `. _( `./ +-----+ 2661 A------( Local )-------------( L2 ) 2662 ( Net ) ( Net ) +-------+ 2663 /`--(___.-' `--(___.-' ----| S-PLC | 2664 S_/ / PLC .--. / +-------+ 2665 A_/ \_( `. 2666 (Actuator) ( Local ) 2667 ( Net ) 2668 /`--(___.-'\ 2669 / \ A 2670 S A 2672 Figure 11: Current Generic Industrial M2M Network Architecture 2674 This use case focuses on PLC-related communications; communication to 2675 Manufacturing-Execution-Systems (MESs) are not addressed. 2677 This use case covers only critical control/data streams; non-critical 2678 traffic between industrial automation applications (such as 2679 communication of state, configuration, set-up, and database 2680 communication) are adequately served by currently available 2681 prioritizing techniques. Such traffic can use up to 80% of the total 2682 bandwidth required. There is also a subset of non-time-critical 2683 traffic that must be reliable even though it is not time sensitive. 2685 In this use case the primary need for deterministic networking is to 2686 provide end-to-end delivery of M2M messages within specific timing 2687 constraints, for example in closed loop automation control. Today 2688 this level of determinism is provided by proprietary networking 2689 technologies. In addition, standard networking technologies are used 2690 to connect the local network to remote industrial automation sites, 2691 e.g. over an enterprise or metro network which also carries other 2692 types of traffic. Therefore, flows that should be forwarded with 2693 deterministic guarantees need to be sustained regardless of the 2694 amount of other flows in those networks. 2696 7.2. Industrial M2M Communication Today 2698 Today, proprietary networks fulfill the needed timing and 2699 availability for M2M networks. 2701 The network topologies used today by industrial automation are 2702 similar to those used by telecom networks: Daisy Chain, Ring, Hub and 2703 Spoke, and Comb (a subset of Daisy Chain). 2705 PLC-related control/data streams are transmitted periodically and 2706 carry either a pre-configured payload or a payload configured during 2707 runtime. 2709 Some industrial applications require time synchronization at the end 2710 nodes. For such time-coordinated PLCs, accuracy of 1 microsecond is 2711 required. Even in the case of "non-time-coordinated" PLCs time sync 2712 may be needed e.g. for timestamping of sensor data. 2714 Industrial network scenarios require advanced security solutions. 2715 Many of the current industrial production networks are physically 2716 separated. Preventing critical flows from be leaked outside a domain 2717 is handled today by filtering policies that are typically enforced in 2718 firewalls. 2720 7.2.1. Transport Parameters 2722 The Cycle Time defines the frequency of message(s) between industrial 2723 actors. The Cycle Time is application dependent, in the range of 1ms 2724 - 100ms for critical control/data streams. 2726 Because industrial applications assume deterministic transport for 2727 critical Control-Data-Stream parameters (instead of defining latency 2728 and delay variation parameters) it is sufficient to fulfill the upper 2729 bound of latency (maximum latency). The underlying networking 2730 infrastructure must ensure a maximum end-to-end delivery time of 2731 messages in the range of 100 microseconds to 50 milliseconds 2732 depending on the control loop application. 2734 The bandwidth requirements of control/data streams are usually 2735 calculated directly from the bytes-per-cycle parameter of the control 2736 loop. For PLC-to-PLC communication one can expect 2 - 32 streams 2737 with packet size in the range of 100 - 700 bytes. For S-PLC to PLCs 2738 the number of streams is higher - up to 256 streams. Usually no more 2739 than 20% of available bandwidth is used for critical control/data 2740 streams. In today's networks 1Gbps links are commonly used. 2742 Most PLC control loops are rather tolerant of packet loss, however 2743 critical control/data streams accept no more than 1 packet loss per 2744 consecutive communication cycle (i.e. if a packet gets lost in cycle 2745 "n", then the next cycle ("n+1") must be lossless). After two or 2746 more consecutive packet losses the network may be considered to be 2747 "down" by the Application. 2749 As network downtime may impact the whole production system the 2750 required network availability is rather high (99,999%). 2752 Based on the above parameters we expect that some form of redundancy 2753 will be required for M2M communications, however any individual 2754 solution depends on several parameters including cycle time, delivery 2755 time, etc. 2757 7.2.2. Stream Creation and Destruction 2759 In an industrial environment, critical control/data streams are 2760 created rather infrequently, on the order of ~10 times per day / week 2761 / month. Most of these critical control/data streams get created at 2762 machine startup, however flexibility is also needed during runtime, 2763 for example when adding or removing a machine. Going forward as 2764 production systems become more flexible, we expect a significant 2765 increase in the rate at which streams are created, changed and 2766 destroyed. 2768 7.3. Industrial M2M Future 2770 We would like to see a converged IP-standards-based network with 2771 deterministic properties that can satisfy the timing, security and 2772 reliability constraints described above. Today's proprietary 2773 networks could then be interfaced to such a network via gateways or, 2774 in the case of new installations, devices could be connected directly 2775 to the converged network. 2777 For this use case we expect time synchronization accuracy on the 2778 order of 1us. 2780 7.4. Industrial M2M Asks 2782 o Converged IP-based network 2784 o Deterministic behavior (bounded latency and jitter ) 2786 o High availability (presumably through redundancy) (99.999 %) 2788 o Low message delivery time (100us - 50ms) 2790 o Low packet loss (burstless, 0.1-1 %) 2792 o Security (e.g. prevent critical flows from being leaked between 2793 physically separated networks) 2795 8. Mining Industry 2797 8.1. Use Case Description 2799 The mining industry is highly dependent on networks to monitor and 2800 control their systems both in open-pit and underground extraction, 2801 transport and refining processes. In order to reduce risks and 2802 increase operational efficiency in mining operations, a number of 2803 processes have migrated the operators from the extraction site to 2804 remote control and monitoring. 2806 In the case of open pit mining, autonomous trucks are used to 2807 transport the raw materials from the open pit to the refining factory 2808 where the final product (e.g. Copper) is obtained. Although the 2809 operation is autonomous, the tracks are remotely monitored from a 2810 central facility. 2812 In pit mines, the monitoring of the tailings or mine dumps is 2813 critical in order to avoid any environmental pollution. In the past, 2814 monitoring has been conducted through manual inspection of pre- 2815 installed dataloggers. Cabling is not usually exploited in such 2816 scenarios due to the cost and complex deployment requirements. 2817 Currently, wireless technologies are being employed to monitor these 2818 cases permanently. Slopes are also monitored in order to anticipate 2819 possible mine collapse. Due to the unstable terrain, cable 2820 maintenance is costly and complex and hence wireless technologies are 2821 employed. 2823 In the underground monitoring case, autonomous vehicles with 2824 extraction tools travel autonomously through the tunnels, but their 2825 operational tasks (such as excavation, stone breaking and transport) 2826 are controlled remotely from a central facility. This generates 2827 video and feedback upstream traffic plus downstream actuator control 2828 traffic. 2830 8.2. Mining Industry Today 2832 Currently the mining industry uses a packet switched architecture 2833 supported by high speed ethernet. However in order to achieve the 2834 delay and packet loss requirements the network bandwidth is 2835 overestimated, thus providing very low efficiency in terms of 2836 resource usage. 2838 QoS is implemented at the Routers to separate video, management, 2839 monitoring and process control traffic for each stream. 2841 Since mobility is involved in this process, the connection between 2842 the backbone and the mobile devices (e.g. trucks, trains and 2843 excavators) is solved using a wireless link. These links are based 2844 on 802.11 for open-pit mining and leaky feeder for underground 2845 mining. 2847 Lately in pit mines the use of LPWAN technologies has been extended: 2848 Tailings, slopes and mine dumps are monitored by battery-powered 2849 dataloggers that make use of robust long range radio technologies. 2850 Reliability is usually ensured through retransmissions at L2. 2851 Gateways or concentrators act as bridges forwarding the data to the 2852 backbone ethernet network. Deterministic requirements are biased 2853 towards reliability rather than latency as events are slowly 2854 triggered or can be anticipated in advance. 2856 At the mineral processing stage, conveyor belts and refining 2857 processes are controlled by a SCADA system, which provides the in- 2858 factory delay-constrained networking requirements. 2860 Voice communications are currently served by a redundant trunking 2861 infrastructure, independent from current data networks. 2863 8.3. Mining Industry Future 2865 Mining operations and management are currently converging towards a 2866 combination of autonomous operation and teleoperation of transport 2867 and extraction machines. This means that video, audio, monitoring 2868 and process control traffic will increase dramatically. Ideally, all 2869 activities on the mine will rely on network infrastructure. 2871 Wireless for open-pit mining is already a reality with LPWAN 2872 technologies and it is expected to evolve to more advanced LPWAN 2873 technologies such as those based on LTE to increase last hop 2874 reliability or novel LPWAN flavours with deterministic access. 2876 One area in which DetNet can improve this use case is in the wired 2877 networks that make up the "backbone network" of the system, which 2878 connect together many wireless access points (APs). The mobile 2879 machines (which are connected to the network via wireless) transition 2880 from one AP to the next as they move about. A deterministic, 2881 reliable, low latency backbone can enable these transitions to be 2882 more reliable. 2884 Connections which extend all the way from the base stations to the 2885 machinery via a mix of wired and wireless hops would also be 2886 beneficial, for example to improve remote control responsiveness of 2887 digging machines. However to guarantee deterministic performance of 2888 a DetNet, the end-to-end underlying network must be deterministic. 2889 Thus for this use case if a deterministic wireless transport is 2890 integrated with a wire-based DetNet network, it could create the 2891 desired wired plus wireless end-to-end deterministic network. 2893 8.4. Mining Industry Asks 2895 o Improved bandwidth efficiency 2897 o Very low delay to enable machine teleoperation 2899 o Dedicated bandwidth usage for high resolution video streams 2901 o Predictable delay to enable realtime monitoring 2903 o Potential to construct a unified DetNet network over a combination 2904 of wired and deterministic wireless links 2906 9. Private Blockchain 2908 9.1. Use Case Description 2910 Blockchain was created with bitcoin, as a 'public' blockchain on the 2911 open Internet, however blockchain has also spread far beyond its 2912 original host into various industries such as smart manufacturing, 2913 logistics, security, legal rights and others. In these industries 2914 blockchain runs in designated and carefully managed network in which 2915 deterministic networking requirements could be addressed by Detnet. 2916 Such implementations are referred to as 'private' blockchain. 2918 The sole distinction between public and private blockchain is related 2919 to who is allowed to participate in the network, execute the 2920 consensus protocol and maintain the shared ledger. 2922 Today's networks treat the traffic from blockchain on a best-effort 2923 basis, but blockchain operation could be made much more efficient if 2924 deterministic networking service were available to minimize latency 2925 and packet loss in the network. 2927 9.1.1. Blockchain Operation 2929 A 'block' runs as a container of a batch of primary items such as 2930 transactions, property records etc. The blocks are chained in such a 2931 way that the hash of the previous block works as the pointer header 2932 of the new block, where confirmation of each block requires a 2933 consensus mechanism. When an item arrives at a blockchain node, the 2934 latter broadcasts this item to the rest of nodes which receive and 2935 verify it and put it in the ongoing block. Block confirmation 2936 process begins as the amount of items reaches the predefined block 2937 capacity, and the node broadcasts its proved block to the rest of 2938 nodes to be verified and chained. 2940 9.1.2. Blockchain Network Architecture 2942 Blockchain node communication and coordination is achieved mainly 2943 through frequent point to multi-point communication, however 2944 persistent point-to-point connections are used to transport both the 2945 items and the blocks to the other nodes. 2947 When a node initiates, it first requests the other nodes' address 2948 from a specific entity such as DNS, then it creates persistent 2949 connections each of with other nodes. If node A confirms an item, it 2950 sends the item to the other nodes via the persistent connections. 2952 As a new block in a node completes and gets proved among the nodes, 2953 it starts propagating this block towards its neighbor nodes. Assume 2954 node A receives a block, it sends invite message after verification 2955 to its neighbor B, B checks if the designated block is available, it 2956 responds get message to A if it is unavailable, and A send the 2957 complete block to B. B repeats the process as A to start the next 2958 round of block propagation. 2960 The challenge of blockchain network operation is not overall data 2961 rates, since the volume from both block and item stays between 2962 hundreds of bytes to a couple of mega bytes per second, but is in 2963 transporting the blocks with minimum latency to maximize efficiency 2964 of the blockchain consensus process. 2966 9.1.3. Security Considerations 2968 Security is crucial to blockchain applications, and todayt blockchain 2969 addresses its security issues mainly at the application level, where 2970 cryptography as well as hash-based consensus play a leading role 2971 preventing both double-spending and malicious service attack. 2972 However, there is concern that in the proposed use case of a private 2973 blockchain network which is dependent on deterministic properties, 2974 the network could be vulnerable to delays and other specific attacks 2975 against determinism which could interrupt service. 2977 9.2. Private Blockchain Today 2979 Today private blockchain runs in L2 or L3 VPN, in general without 2980 guaranteed determinism. The industry players are starting to realize 2981 that improving determinism in their blockchain networks could improve 2982 the performance of their service, but as of today these goals are not 2983 being met. 2985 9.3. Private Blockchain Future 2987 Blockchain system performance can be greatly improved through 2988 deterministic networking service primarily because it would 2989 accelerate the consensus process. It would be valuable to be able to 2990 design a private blockchain network with the following properties: 2992 o Transport of point to multi-point traffic in a coordinated network 2993 architecture rather than at the application layer (which typically 2994 uses point-to-point connections) 2996 o Guaranteed transport latency 2998 o Reduced packet loss (to the point where packet retransmission- 2999 incurred delay would be negligible.) 3001 9.4. Private Blockchain Asks 3003 o Layer 2 and Layer 3 multicast of blockchain traffic 3005 o Item and block delivery with bounded, low latency and negligible 3006 packet loss 3008 o Coexistence in a single network of blockchain and IT traffic. 3010 o Ability to scale the network by distributing the centralized 3011 control of the network across multiple control entities. 3013 10. Network Slicing 3015 10.1. Use Case Description 3017 Network Slicing divides one physical network infrastructure into 3018 multiple logical networks. Each slice, corresponding to a logical 3019 network, uses resources and network functions independently from each 3020 other. Network Slicing provides flexibility of resource allocation 3021 and service quality customization. 3023 Future services will demand network performance with a wide variety 3024 of characteristics such as high data rate, low latency, low loss 3025 rate, security and many other parameters. Ideally every service 3026 would have its own physical network satisfying its particular 3027 performance requirements, however that would be prohibitively 3028 expensive. Network Slicing can provide a customized slice for a 3029 single service, and multiple slices can share the same physical 3030 network. This method can optimize the performance for the service at 3031 lower cost, and the flexibility of setting up and release the slices 3032 also allows the user to allocate the network resources dynamically. 3034 Unlike the other use cases presented here, Network Slicing is not a 3035 specific application that depends on specific deterministic 3036 properties; rather it is introduced as an area of networking to which 3037 DetNet might be applicable. 3039 10.2. DetNet Applied to Network Slicing 3041 10.2.1. Resource Isolation Across Slices 3043 One of the requirements discussed for Network Slicing is the "hard" 3044 separation of various users' deterministic performance. That is, it 3045 should be impossible for activity, lack of activity, or changes in 3046 activity of one or more users to have any appreciable effect on the 3047 deterministic performance parameters of any other slices. Typical 3048 techniques used today, which share a physical network among users, do 3049 not offer this level of isolation. DetNet can supply point-to-point 3050 or point-to-multipoint paths that offer bandwidth and latency 3051 guarantees to a user that cannot be affected by other users' data 3052 traffic. Thus DetNet is a powerful tool when latency and reliability 3053 are required in Network Slicing. 3055 10.2.2. Deterministic Services Within Slices 3057 Slices may need to provide services with DetNet-type performance 3058 guarantees, however we note that a system can be implemented to 3059 provide such services in more than one way. For example the slice 3060 itself might be implemented using DetNet, and thus the slice can 3061 provide service guarantees and isolation to its users without any 3062 particular DetNet awareness on the part of the users' applications. 3063 Alternatively, a "non-DetNet-aware" slice may host an application 3064 that itself implements DetNet services and thus can enjoy similar 3065 service guarantees. 3067 10.3. A Network Slicing Use Case Example - 5G Bearer Network 3069 Network Slicing is a core feature of 5G defined in 3GPP, which is 3070 currently under development. A network slice in a mobile network is 3071 a complete logical network including Radio Access Network (RAN) and 3072 Core Network (CN). It provides telecommunication services and 3073 network capabilities, which may vary from slice to slice. A 5G 3074 bearer network is a typical use case of Network Slicing; for example 3075 consider three 5G service scenarios: eMMB, URLLC, and mMTC. 3077 o eMBB (Enhanced Mobile Broadband) focuses on services characterized 3078 by high data rates, such as high definition videos, virtual 3079 reality, augmented reality, and fixed mobile convergence. 3081 o URLLC (Ultra-Reliable and Low Latency Communications) focuses on 3082 latency-sensitive services, such as self-driving vehicles, remote 3083 surgery, or drone control. 3085 o mMTC (massive Machine Type Communications) focuses on services 3086 that have high requirements for connection density, such as those 3087 typical for smart city and smart agriculture use cases. 3089 A 5G bearer network could use DetNet to provide hard resource 3090 isolation across slices and within the slice. For example consider 3091 Slice-A and Slice-B, with DetNet used to transit services URLLC-A and 3092 URLLC-B over them. Without DetNet, URLLC-A and URLLC-B would compete 3093 for bandwidth resource, and latency and reliability would not be 3094 guaranteed. With DetNet, URLLC-A and URLLC-B have separate bandwidth 3095 reservation and there is no resource conflict between them, as though 3096 they were in different logical networks. 3098 10.4. Non-5G Applications of Network Slicing 3100 Although operation of services not related to 5G is not part of the 3101 5G Network Slicing definition and scope, Network Slicing is likely to 3102 become a preferred approach to providing various services across a 3103 shared physical infrastructure. Examples include providing 3104 electrical utilities services and pro audio services via slices. Use 3105 cases like these could become more common once the work for the 5G 3106 core network evolves to include wired as well as wireless access. 3108 10.5. Limitations of DetNet in Network Slicing 3110 DetNet cannot cover every Network Slicing use case. One issue is 3111 that DetNet is a point-to-point or point-to-multipoint technology, 3112 however Network Slicing ultimately needs multi-point to multi-point 3113 guarantees. Another issue is that the number of flows that can be 3114 carried by DetNet is limited by DetNet scalability; flow aggregation 3115 and queuing management modification may help address this. 3116 Additional work and discussion are needed to address these topics. 3118 10.6. Network Slicing Today and Future 3120 Network Slicing has the promise to satisfy many requirements of 3121 future network deployment scenarios, but it is still a collection of 3122 ideas and analysis, without a specific technical solution. DetNet is 3123 one of various technologies that have potential to be used in Network 3124 Slicing, along with for example Flex-E and Segment Routing. For more 3125 information please see the IETF99 Network Slicing BOF session agenda 3126 and materials. 3128 10.7. Network Slicing Asks 3130 o Isolation from other flows through Queuing Management 3132 o Service Quality Customization and Guarantee 3134 o Security 3136 11. Use Case Common Themes 3138 This section summarizes the expected properties of a DetNet network, 3139 based on the use cases as described in this draft. 3141 11.1. Unified, standards-based network 3143 11.1.1. Extensions to Ethernet 3145 A DetNet network is not "a new kind of network" - it based on 3146 extensions to existing Ethernet standards, including elements of IEEE 3147 802.1 AVB/TSN and related standards. Presumably it will be possible 3148 to run DetNet over other underlying transports besides Ethernet, but 3149 Ethernet is explicitly supported. 3151 11.1.2. Centrally Administered 3153 In general a DetNet network is not expected to be "plug and play" - 3154 it is expected that there is some centralized network configuration 3155 and control system. Such a system may be in a single central 3156 location, or it maybe distributed across multiple control entities 3157 that function together as a unified control system for the network. 3158 However, the ability to "hot swap" components (e.g. due to 3159 malfunction) is similar enough to "plug and play" that this kind of 3160 behavior may be expected in DetNet networks, depending on the 3161 implementation. 3163 11.1.3. Standardized Data Flow Information Models 3165 Data Flow Information Models to be used with DetNet networks are to 3166 be specified by DetNet. 3168 11.1.4. L2 and L3 Integration 3170 A DetNet network is intended to integrate between Layer 2 (bridged) 3171 network(s) (e.g. AVB/TSN LAN) and Layer 3 (routed) network(s) (e.g. 3172 using IP-based protocols). One example of this is "making AVB/TSN- 3173 type deterministic performance available from Layer 3 applications, 3174 e.g. using RTP". Another example is "connecting two AVB/TSN LANs 3175 ("islands") together through a standard router". 3177 11.1.5. Consideration for IPv4 3179 This Use Cases draft explicitly does not specify any particular 3180 implementation or protocol, however it has been observed that various 3181 of the use cases described (and their associated industries) are 3182 explicitly based on IPv4 (as opposed to IPv6) and it is not 3183 considered practical to expect them to migrate to IPv6 in order to 3184 use DetNet. Thus the expectation is that even if not every feature 3185 of DetNet is available in an IPv4 context, at least some of the 3186 significant benefits (such as guaranteed end-to-end delivery and low 3187 latency) are expected to be available. 3189 11.1.6. Guaranteed End-to-End Delivery 3191 Packets sent over DetNet are guaranteed not to be dropped by the 3192 network due to congestion. However, the network may drop packets for 3193 intended reasons, e.g. per security measures. Also note that this 3194 guarantee applies to the actions of DetNet protocol software, and 3195 does not provide any guarantee against lower level errors such as 3196 media errors or checksum errors. 3198 11.1.7. Replacement for Multiple Proprietary Deterministic Networks 3200 There are many proprietary non-interoperable deterministic Ethernet- 3201 based networks currently available; DetNet is intended to provide an 3202 open-standards-based alternative to such networks. 3204 11.1.8. Mix of Deterministic and Best-Effort Traffic 3206 DetNet is intended to support coexistance of time-sensitive 3207 operational (OT) traffic and information (IT) traffic on the same 3208 ("unified") network. 3210 11.1.9. Unused Reserved BW to be Available to Best Effort Traffic 3212 If bandwidth reservations are made for a stream but the associated 3213 bandwidth is not used at any point in time, that bandwidth is made 3214 available on the network for best-effort traffic. If the owner of 3215 the reserved stream then starts transmitting again, the bandwidth is 3216 no longer available for best-effort traffic, on a moment-to-moment 3217 basis. Note that such "temporarily available" bandwidth is not 3218 available for time-sensitive traffic, which must have its own 3219 reservation. 3221 11.1.10. Lower Cost, Multi-Vendor Solutions 3223 The DetNet network specifications are intended to enable an ecosystem 3224 in which multiple vendors can create interoperable products, thus 3225 promoting device diversity and potentially higher numbers of each 3226 device manufactured, promoting cost reduction and cost competition 3227 among vendors. The intent is that DetNet networks should be able to 3228 be created at lower cost and with greater diversity of available 3229 devices than existing proprietary networks. 3231 11.2. Scalable Size 3233 DetNet networks range in size from very small, e.g. inside a single 3234 industrial machine, to very large, for example a Utility Grid network 3235 spanning a whole country, and involving many "hops" over various 3236 kinds of links for example radio repeaters, microwave linkes, fiber 3237 optic links, etc.. However recall that the scope of DetNet is 3238 confined to networks that are centrally administered, and explicitly 3239 excludes unbounded decentralized networks such as the Internet. 3241 11.3. Scalable Timing Parameters and Accuracy 3243 11.3.1. Bounded Latency 3245 The DetNet Data Flow Information Model is expected to provide means 3246 to configure the network that include parameters for querying network 3247 path latency, requesting bounded latency for a given stream, 3248 requesting worst case maximum and/or minimum latency for a given path 3249 or stream, and so on. It is an expected case that the network may 3250 not be able to provide a given requested service level, and if so the 3251 network control system should reply that the requested services is 3252 not available (as opposed to accepting the parameter but then not 3253 delivering the desired behavior). 3255 11.3.2. Low Latency 3257 Applications may require "extremely low latency" however depending on 3258 the application these may mean very different latency values; for 3259 example "low latency" across a Utility grid network is on a different 3260 time scale than "low latency" in a motor control loop in a small 3261 machine. The intent is that the mechanisms for specifying desired 3262 latency include wide ranges, and that architecturally there is 3263 nothing to prevent arbirtrarily low latencies from being implemented 3264 in a given network. 3266 11.3.3. Symmetrical Path Delays 3268 Some applications would like to specify that the transit delay time 3269 values be equal for both the transmit and return paths. 3271 11.4. High Reliability and Availability 3273 Reliablity is of critical importance to many DetNet applications, in 3274 which consequences of failure can be extraordinarily high in terms of 3275 cost and even human life. DetNet based systems are expected to be 3276 implemented with essentially arbitrarily high availability (for 3277 example 99.9999% up time, or even 12 nines). The intent is that the 3278 DetNet designs should not make any assumptions about the level of 3279 reliability and availability that may be required of a given system, 3280 and should define parameters for communicating these kinds of metrics 3281 within the network. 3283 A strategy used by DetNet for providing such extraordinarily high 3284 levels of reliability is to provide redundant paths that can be 3285 seamlessly switched between, while maintaining the required 3286 performance of that system. 3288 11.5. Security 3290 Security is of critical importance to many DetNet applications. A 3291 DetNet network must be able to be made secure against devices 3292 failures, attackers, misbehaving devices, and so on. In a DetNet 3293 network the data traffic is expected to be be time-sensitive, thus in 3294 addition to arriving with the data content as intended, the data must 3295 also arrive at the expected time. This may present "new" security 3296 challenges to implementers, and must be addressed accordingly. There 3297 are other security implications, including (but not limited to) the 3298 change in attack surface presented by packet replication and 3299 elimination. 3301 11.6. Deterministic Flows 3303 Reserved bandwidth data flows must be isolated from each other and 3304 from best-effort traffic, so that even if the network is saturated 3305 with best-effort (and/or reserved bandwidth) traffic, the configured 3306 flows are not adversely affected. 3308 12. Use Cases Explicitly Out of Scope for DetNet 3310 This section contains use case text that has been determined to be 3311 outside of the scope of the present DetNet work. 3313 12.1. DetNet Scope Limitations 3315 The scope of DetNet is deliberately limited to specific use cases 3316 that are consistent with the WG charter, subject to the 3317 interpretation of the WG. At the time the DetNet Use Cases were 3318 solicited and provided by the authors the scope of DetNet was not 3319 clearly defined, and as that clarity has emerged, certain of the use 3320 cases have been determined to be outside the scope of the present 3321 DetNet work. Such text has been moved into this section to clarify 3322 that these use cases will not be supported by the DetNet work. 3324 The text in this section was moved here based on the following 3325 "exclusion" principles. Or, as an alternative to moving all such 3326 text to this section, some draft text has been modified in situ to 3327 reflect these same principles. 3329 The following principles have been established to clarify the scope 3330 of the present DetNet work. 3332 o The scope of network addressed by DetNet is limited to networks 3333 that can be centrally controlled, i.e. an "enterprise" aka 3334 "corporate" network. This explicitly excludes "the open 3335 Internet". 3337 o Maintaining synchronized time across a DetNet network is crucial 3338 to its operation, however DetNet assumes that time is to be 3339 maintained using other means, for example (but not limited to) 3340 Precision Time Protocol ([IEEE1588]). A use case may state the 3341 accuracy and reliability that it expects from the DetNet network 3342 as part of a whole system, however it is understood that such 3343 timing properties are not guaranteed by DetNet itself. It is 3344 currently an open question as to whether DetNet protocols will 3345 include a way for an application to communicate such timing 3346 expectations to the network, and if so whether they would be 3347 expected to materially affect the performance they would receive 3348 from the network as a result. 3350 12.2. Internet-based Applications 3352 There are many applications that communicate over the open Internet 3353 that could benefit from guaranteed delivery and bounded latency. 3354 However as noted above, all such applications when run over the open 3355 Internet are out of scope for DetNet. These same applications may be 3356 in-scope when run in constrained environments, i.e. within a 3357 centrally controlled DetNet network. The following are some examples 3358 of such applications. 3360 12.2.1. Use Case Description 3362 12.2.1.1. Media Content Delivery 3364 Media content delivery continues to be an important use of the 3365 Internet, yet users often experience poor quality audio and video due 3366 to the delay and jitter inherent in today's Internet. 3368 12.2.1.2. Online Gaming 3370 Online gaming is a significant part of the gaming market, however 3371 latency can degrade the end user experience. For example "First 3372 Person Shooter" games are highly delay-sensitive. 3374 12.2.1.3. Virtual Reality 3376 Virtual reality has many commercial applications including real 3377 estate presentations, remote medical procedures, and so on. Low 3378 latency is critical to interacting with the virtual world because 3379 perceptual delays can cause motion sickness. 3381 12.2.2. Internet-Based Applications Today 3383 Internet service today is by definition "best effort", with no 3384 guarantees on delivery or bandwidth. 3386 12.2.3. Internet-Based Applications Future 3388 We imagine an Internet from which we will be able to play a video 3389 without glitches and play games without lag. 3391 For online gaming, the maximum round-trip delay can be 100ms and 3392 stricter for FPS gaming which can be 10-50ms. Transport delay is the 3393 dominate part with a 5-20ms budget. 3395 For VR, 1-10ms maximum delay is needed and total network budget is 3396 1-5ms if doing remote VR. 3398 Flow identification can be used for gaming and VR, i.e. it can 3399 recognize a critical flow and provide appropriate latency bounds. 3401 12.2.4. Internet-Based Applications Asks 3403 o Unified control and management protocols to handle time-critical 3404 data flow 3406 o Application-aware flow filtering mechanism to recognize the timing 3407 critical flow without doing 5-tuple matching 3409 o Unified control plane to provide low latency service on Layer-3 3410 without changing the data plane 3412 o OAM system and protocols which can help to provide E2E-delay 3413 sensitive service provisioning 3415 12.3. Pro Audio and Video - Digital Rights Management (DRM) 3417 This section was moved here because this is considered a Link layer 3418 topic, not direct responsibility of DetNet. 3420 Digital Rights Management (DRM) is very important to the audio and 3421 video industries. Any time protected content is introduced into a 3422 network there are DRM concerns that must be maintained (see 3423 [CONTENT_PROTECTION]). Many aspects of DRM are outside the scope of 3424 network technology, however there are cases when a secure link 3425 supporting authentication and encryption is required by content 3426 owners to carry their audio or video content when it is outside their 3427 own secure environment (for example see [DCI]). 3429 As an example, two techniques are Digital Transmission Content 3430 Protection (DTCP) and High-Bandwidth Digital Content Protection 3431 (HDCP). HDCP content is not approved for retransmission within any 3432 other type of DRM, while DTCP may be retransmitted under HDCP. 3433 Therefore if the source of a stream is outside of the network and it 3434 uses HDCP protection it is only allowed to be placed on the network 3435 with that same HDCP protection. 3437 12.4. Pro Audio and Video - Link Aggregation 3439 Note: The term "Link Aggregation" is used here as defined by the text 3440 in the following paragraph, i.e. not following a more common Network 3441 Industry definition. Current WG consensus is that this item won't be 3442 directly supported by the DetNet architecture, for example because it 3443 implies guarantee of in-order delivery of packets which conflicts 3444 with the core goal of achieving the lowest possible latency. 3446 For transmitting streams that require more bandwidth than a single 3447 link in the target network can support, link aggregation is a 3448 technique for combining (aggregating) the bandwidth available on 3449 multiple physical links to create a single logical link of the 3450 required bandwidth. However, if aggregation is to be used, the 3451 network controller (or equivalent) must be able to determine the 3452 maximum latency of any path through the aggregate link. 3454 13. Contributors 3456 RFC7322 limits the number of authors listed on the front page of a 3457 draft to a maximum of 5, far fewer than the 20 individuals below who 3458 made important contributions to this draft. The editor wishes to 3459 thank and acknowledge each of the following authors for contributing 3460 text to this draft. See also Section 14. 3462 Craig Gunther (Harman International) 3463 10653 South River Front Parkway, South Jordan,UT 84095 3464 phone +1 801 568-7675, email craig.gunther@harman.com 3466 Pascal Thubert (Cisco Systems, Inc) 3467 Building D, 45 Allee des Ormes - BP1200, MOUGINS 3468 Sophia Antipolis 06254 FRANCE 3469 phone +33 497 23 26 34, email pthubert@cisco.com 3471 Patrick Wetterwald (Cisco Systems) 3472 45 Allees des Ormes, Mougins, 06250 FRANCE 3473 phone +33 4 97 23 26 36, email pwetterw@cisco.com 3475 Jean Raymond (Hydro-Quebec) 3476 1500 University, Montreal, H3A3S7, Canada 3477 phone +1 514 840 3000, email raymond.jean@hydro.qc.ca 3479 Jouni Korhonen (Broadcom Corporation) 3480 3151 Zanker Road, San Jose, 95134, CA, USA 3481 email jouni.nospam@gmail.com 3483 Yu Kaneko (Toshiba) 3484 1 Komukai-Toshiba-cho, Saiwai-ku, Kasasaki-shi, Kanagawa, Japan 3485 email yu1.kaneko@toshiba.co.jp 3487 Subir Das (Vencore Labs) 3488 150 Mount Airy Road, Basking Ridge, New Jersey, 07920, USA 3489 email sdas@appcomsci.com 3491 Balazs Varga (Ericsson) 3492 Konyves Kalman krt. 11/B, Budapest, Hungary, 1097 3493 email balazs.a.varga@ericsson.com 3494 Janos Farkas (Ericsson) 3495 Konyves Kalman krt. 11/B, Budapest, Hungary, 1097 3496 email janos.farkas@ericsson.com 3498 Franz-Josef Goetz (Siemens) 3499 Gleiwitzerstr. 555, Nurnberg, Germany, 90475 3500 email franz-josef.goetz@siemens.com 3502 Juergen Schmitt (Siemens) 3503 Gleiwitzerstr. 555, Nurnberg, Germany, 90475 3504 email juergen.jues.schmitt@siemens.com 3506 Xavier Vilajosana (Worldsensing) 3507 483 Arago, Barcelona, Catalonia, 08013, Spain 3508 email xvilajosana@worldsensing.com 3510 Toktam Mahmoodi (King's College London) 3511 Strand, London WC2R 2LS, United Kingdom 3512 email toktam.mahmoodi@kcl.ac.uk 3514 Spiros Spirou (Intracom Telecom) 3515 19.7 km Markopoulou Ave., Peania, Attiki, 19002, Greece 3516 email spiros.spirou@gmail.com 3518 Petra Vizarreta (Technical University of Munich) 3519 Maxvorstadt, ArcisstraBe 21, Munich, 80333, Germany 3520 email petra.stojsavljevic@tum.de 3522 Daniel Huang (ZTE Corporation, Inc.) 3523 No. 50 Software Avenue, Nanjing, Jiangsu, 210012, P.R. China 3524 email huang.guangping@zte.com.cn 3526 Xuesong Geng (Huawei Technologies) 3527 email gengxuesong@huawei.com 3529 Diego Dujovne (Universidad Diego Portales) 3530 email diego.dujovne@mail.udp.cl 3532 Maik Seewald (Cisco Systems) 3533 email maseewal@cisco.com 3535 14. Acknowledgments 3537 14.1. Pro Audio 3539 This section was derived from draft-gunther-detnet-proaudio-req-01. 3541 The editors would like to acknowledge the help of the following 3542 individuals and the companies they represent: 3544 Jeff Koftinoff, Meyer Sound 3546 Jouni Korhonen, Associate Technical Director, Broadcom 3548 Pascal Thubert, CTAO, Cisco 3550 Kieran Tyrrell, Sienda New Media Technologies GmbH 3552 14.2. Utility Telecom 3554 This section was derived from draft-wetterwald-detnet-utilities-reqs- 3555 02. 3557 Faramarz Maghsoodlou, Ph. D. IoT Connected Industries and Energy 3558 Practice Cisco 3560 Pascal Thubert, CTAO Cisco 3562 14.3. Building Automation Systems 3564 This section was derived from draft-bas-usecase-detnet-00. 3566 14.4. Wireless for Industrial 3568 This section was derived from draft-thubert-6tisch-4detnet-01. 3570 This specification derives from the 6TiSCH architecture, which is the 3571 result of multiple interactions, in particular during the 6TiSCH 3572 (bi)Weekly Interim call, relayed through the 6TiSCH mailing list at 3573 the IETF. 3575 The authors wish to thank: Kris Pister, Thomas Watteyne, Xavier 3576 Vilajosana, Qin Wang, Tom Phinney, Robert Assimiti, Michael 3577 Richardson, Zhuo Chen, Malisa Vucinic, Alfredo Grieco, Martin Turon, 3578 Dominique Barthel, Elvis Vogli, Guillaume Gaillard, Herman Storey, 3579 Maria Rita Palattella, Nicola Accettura, Patrick Wetterwald, Pouria 3580 Zand, Raghuram Sudhaakar, and Shitanshu Shah for their participation 3581 and various contributions. 3583 14.5. Cellular Radio 3585 This section was derived from draft-korhonen-detnet-telreq-00. 3587 14.6. Industrial M2M 3589 The authors would like to thank Feng Chen and Marcel Kiessling for 3590 their comments and suggestions. 3592 14.7. Internet Applications and CoMP 3594 This section was derived from draft-zha-detnet-use-case-00 by Yiyong 3595 Zha. 3597 This document has benefited from reviews, suggestions, comments and 3598 proposed text provided by the following members, listed in 3599 alphabetical order: Jing Huang, Junru Lin, Lehong Niu and Oilver 3600 Huang. 3602 14.8. Electrical Utilities 3604 The wind power generation use case has been extracted from the study 3605 of Wind Farms conducted within the 5GPPP Virtuwind Project. The 3606 project is funded by the European Union's Horizon 2020 research and 3607 innovation programme under grant agreement No 671648 (VirtuWind). 3609 14.9. Network Slicing 3611 This section was written by Xuesong Geng, who would like to 3612 acknowledge Norm Finn and Mach Chen for their useful comments. 3614 14.10. Mining 3616 This section was written by Diego Dujovne in conjunction with Xavier 3617 Vilasojana. 3619 14.11. Private Blockchain 3621 This section was written by Daniel Huang. 3623 15. Informative References 3625 [ACE] IETF, "Authentication and Authorization for Constrained 3626 Environments", 3627 . 3629 [Ahm14] Ahmed, M. and R. Kim, "Communication network architectures 3630 for smart-wind power farms.", Energies, p. 3900-3921. , 3631 June 2014. 3633 [bacnetip] 3634 ASHRAE, "Annex J to ANSI/ASHRAE 135-1995 - BACnet/IP", 3635 January 1999. 3637 [CCAMP] IETF, "Common Control and Measurement Plane", 3638 . 3640 [CoMP] NGMN Alliance, "RAN EVOLUTION PROJECT COMP EVALUATION AND 3641 ENHANCEMENT", NGMN Alliance NGMN_RANEV_D3_CoMP_Evaluation_ 3642 and_Enhancement_v2.0, March 2015, 3643 . 3646 [CONTENT_PROTECTION] 3647 Olsen, D., "1722a Content Protection", 2012, 3648 . 3651 [CPRI] CPRI Cooperation, "Common Public Radio Interface (CPRI); 3652 Interface Specification", CPRI Specification V6.1, July 3653 2014, . 3656 [CPRI-transp] 3657 CPRI TWG, "CPRI requirements for Ethernet Fronthaul", 3658 November 2015, 3659 . 3662 [DCI] Digital Cinema Initiatives, LLC, "DCI Specification, 3663 Version 1.2", 2012, . 3665 [DICE] IETF, "DTLS In Constrained Environments", 3666 . 3668 [EA12] Evans, P. and M. Annunziata, "Industrial Internet: Pushing 3669 the Boundaries of Minds and Machines", November 2012. 3671 [eCPRI] IEEE Standards Association, "Common Public Radio 3672 Interface, "Common Public Radio Interface: eCPRI Interface 3673 Specification V1.0", 2017, . 3675 [ESPN_DC2] 3676 Daley, D., "ESPN's DC2 Scales AVB Large", 2014, 3677 . 3680 [flnet] Japan Electrical Manufacturers Association, "JEMA 1479 - 3681 English Edition", September 2012. 3683 [Fronthaul] 3684 Chen, D. and T. Mustala, "Ethernet Fronthaul 3685 Considerations", IEEE 1904.3, February 2015, 3686 . 3689 [HART] www.hartcomm.org, "Highway Addressable remote Transducer, 3690 a group of specifications for industrial process and 3691 control devices administered by the HART Foundation". 3693 [I-D.ietf-6tisch-6top-interface] 3694 Wang, Q. and X. Vilajosana, "6TiSCH Operation Sublayer 3695 (6top) Interface", draft-ietf-6tisch-6top-interface-04 3696 (work in progress), July 2015. 3698 [I-D.ietf-6tisch-architecture] 3699 Thubert, P., "An Architecture for IPv6 over the TSCH mode 3700 of IEEE 802.15.4", draft-ietf-6tisch-architecture-14 (work 3701 in progress), April 2018. 3703 [I-D.ietf-6tisch-coap] 3704 Sudhaakar, R. and P. Zand, "6TiSCH Resource Management and 3705 Interaction using CoAP", draft-ietf-6tisch-coap-03 (work 3706 in progress), March 2015. 3708 [I-D.ietf-6tisch-terminology] 3709 Palattella, M., Thubert, P., Watteyne, T., and Q. Wang, 3710 "Terms Used in IPv6 over the TSCH mode of IEEE 802.15.4e", 3711 draft-ietf-6tisch-terminology-10 (work in progress), March 3712 2018. 3714 [I-D.ietf-detnet-architecture] 3715 Finn, N., Thubert, P., Varga, B., and J. Farkas, 3716 "Deterministic Networking Architecture", draft-ietf- 3717 detnet-architecture-05 (work in progress), May 2018. 3719 [I-D.ietf-detnet-problem-statement] 3720 Finn, N. and P. Thubert, "Deterministic Networking Problem 3721 Statement", draft-ietf-detnet-problem-statement-05 (work 3722 in progress), June 2018. 3724 [I-D.ietf-ipv6-multilink-subnets] 3725 Thaler, D. and C. Huitema, "Multi-link Subnet Support in 3726 IPv6", draft-ietf-ipv6-multilink-subnets-00 (work in 3727 progress), July 2002. 3729 [I-D.ietf-mpls-residence-time] 3730 Mirsky, G., Ruffini, S., Gray, E., Drake, J., Bryant, S., 3731 and S. Vainshtein, "Residence Time Measurement in MPLS 3732 network", draft-ietf-mpls-residence-time-15 (work in 3733 progress), March 2017. 3735 [I-D.ietf-roll-rpl-industrial-applicability] 3736 Phinney, T., Thubert, P., and R. Assimiti, "RPL 3737 applicability in industrial networks", draft-ietf-roll- 3738 rpl-industrial-applicability-02 (work in progress), 3739 October 2013. 3741 [I-D.ietf-tictoc-1588overmpls] 3742 Davari, S., Oren, A., Bhatia, M., Roberts, P., and L. 3743 Montini, "Transporting Timing messages over MPLS 3744 Networks", draft-ietf-tictoc-1588overmpls-07 (work in 3745 progress), October 2015. 3747 [I-D.kh-spring-ip-ran-use-case] 3748 Khasnabish, B., hu, f., and L. Contreras, "Segment Routing 3749 in IP RAN use case", draft-kh-spring-ip-ran-use-case-02 3750 (work in progress), November 2014. 3752 [I-D.svshah-tsvwg-deterministic-forwarding] 3753 Shah, S. and P. Thubert, "Deterministic Forwarding PHB", 3754 draft-svshah-tsvwg-deterministic-forwarding-04 (work in 3755 progress), August 2015. 3757 [I-D.thubert-6lowpan-backbone-router] 3758 Thubert, P., "6LoWPAN Backbone Router", draft-thubert- 3759 6lowpan-backbone-router-03 (work in progress), February 3760 2013. 3762 [I-D.wang-6tisch-6top-sublayer] 3763 Wang, Q. and X. Vilajosana, "6TiSCH Operation Sublayer 3764 (6top)", draft-wang-6tisch-6top-sublayer-04 (work in 3765 progress), November 2015. 3767 [IEC-60870-5-104] 3768 International Electrotechnical Commission, "International 3769 Standard IEC 60870-5-104: Network access for IEC 3770 60870-5-101 using standard transport profiles", June 2006. 3772 [IEC61400] 3773 "International standard 61400-25: Communications for 3774 monitoring and control of wind power plants", June 2013. 3776 [IEC61850-90-12] 3777 TC57 WG10, IEC., "IEC 61850-90-12 TR: Communication 3778 networks and systems for power utility automation - Part 3779 90-12: Wide area network engineering guidelines", 2015. 3781 [IEC62439-3:2012] 3782 TC65, IEC., "IEC 62439-3: Industrial communication 3783 networks - High availability automation networks - Part 3: 3784 Parallel Redundancy Protocol (PRP) and High-availability 3785 Seamless Redundancy (HSR)", 2012. 3787 [IEEE1588] 3788 IEEE, "IEEE Standard for a Precision Clock Synchronization 3789 Protocol for Networked Measurement and Control Systems", 3790 IEEE Std 1588-2008, 2008, 3791 . 3794 [IEEE1646] 3795 "Communication Delivery Time Performance Requirements for 3796 Electric Power Substation Automation", IEEE Standard 3797 1646-2004 , Apr 2004. 3799 [IEEE1722] 3800 IEEE, "1722-2011 - IEEE Standard for Layer 2 Transport 3801 Protocol for Time Sensitive Applications in a Bridged 3802 Local Area Network", IEEE Std 1722-2011, 2011, 3803 . 3806 [IEEE19143] 3807 IEEE Standards Association, "P1914.3/D3.1 Draft Standard 3808 for Radio over Ethernet Encapsulations and Mappings", 3809 IEEE 1914.3, 2018, 3810 . 3812 [IEEE802.1TSNTG] 3813 IEEE Standards Association, "IEEE 802.1 Time-Sensitive 3814 Networks Task Group", March 2013, 3815 . 3817 [IEEE802154] 3818 IEEE standard for Information Technology, "IEEE std. 3819 802.15.4, Part. 15.4: Wireless Medium Access Control (MAC) 3820 and Physical Layer (PHY) Specifications for Low-Rate 3821 Wireless Personal Area Networks". 3823 [IEEE802154e] 3824 IEEE standard for Information Technology, "IEEE standard 3825 for Information Technology, IEEE std. 802.15.4, Part. 3826 15.4: Wireless Medium Access Control (MAC) and Physical 3827 Layer (PHY) Specifications for Low-Rate Wireless Personal 3828 Area Networks, June 2011 as amended by IEEE std. 3829 802.15.4e, Part. 15.4: Low-Rate Wireless Personal Area 3830 Networks (LR-WPANs) Amendment 1: MAC sublayer", April 3831 2012. 3833 [IEEE8021AS] 3834 IEEE, "Timing and Synchronizations (IEEE 802.1AS-2011)", 3835 IEEE 802.1AS-2001, 2011, 3836 . 3839 [IEEE8021CM] 3840 Farkas, J., "Time-Sensitive Networking for Fronthaul", 3841 Unapproved PAR, PAR for a New IEEE Standard; 3842 IEEE P802.1CM, April 2015, 3843 . 3846 [IEEE8021TSN] 3847 IEEE 802.1, "The charter of the TG is to provide the 3848 specifications that will allow time-synchronized low 3849 latency streaming services through 802 networks.", 2016, 3850 . 3852 [IETFDetNet] 3853 IETF, "Charter for IETF DetNet Working Group", 2015, 3854 . 3856 [ISA100] ISA/ANSI, "ISA100, Wireless Systems for Automation", 3857 . 3859 [ISA100.11a] 3860 ISA/ANSI, "Wireless Systems for Industrial Automation: 3861 Process Control and Related Applications - ISA100.11a-2011 3862 - IEC 62734", 2011, . 3865 [ISO7240-16] 3866 ISO, "ISO 7240-16:2007 Fire detection and alarm systems -- 3867 Part 16: Sound system control and indicating equipment", 3868 2007, . 3871 [knx] KNX Association, "ISO/IEC 14543-3 - KNX", November 2006. 3873 [lontalk] ECHELON, "LonTalk(R) Protocol Specification Version 3.0", 3874 1994. 3876 [LTE-Latency] 3877 Johnston, S., "LTE Latency: How does it compare to other 3878 technologies", March 2014, 3879 . 3882 [MEF22.1.1] 3883 MEF, "Mobile Backhaul Phase 2 Amendment 1 -- Small Cells", 3884 MEF 22.1.1, July 2014, 3885 . 3888 [MEF8] MEF, "Implementation Agreement for the Emulation of PDH 3889 Circuits over Metro Ethernet Networks", MEF 8, October 3890 2004, 3891 . 3894 [METIS] METIS, "Scenarios, requirements and KPIs for 5G mobile and 3895 wireless system", ICT-317669-METIS/D1.1 ICT- 3896 317669-METIS/D1.1, April 2013, . 3899 [modbus] Modbus Organization, "MODBUS APPLICATION PROTOCOL 3900 SPECIFICATION V1.1b", December 2006. 3902 [MODBUS] Modbus Organization, Inc., "MODBUS Application Protocol 3903 Specification", Apr 2012. 3905 [net5G] Ericsson, "5G Radio Access, Challenges for 2020 and 3906 Beyond", Ericsson white paper wp-5g, June 2013, 3907 . 3909 [NGMN] NGMN Alliance, "5G White Paper", NGMN 5G White Paper v1.0, 3910 February 2015, . 3913 [NGMN-fronth] 3914 NGMN Alliance, "Fronthaul Requirements for C-RAN", March 3915 2015, . 3918 [OPCXML] OPC Foundation, "OPC XML-Data Access Specification", Dec 3919 2004. 3921 [PCE] IETF, "Path Computation Element", 3922 . 3924 [profibus] 3925 IEC, "IEC 61158 Type 3 - Profibus DP", January 2001. 3927 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 3928 Requirement Levels", BCP 14, RFC 2119, 3929 DOI 10.17487/RFC2119, March 1997, 3930 . 3932 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 3933 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, 3934 December 1998, . 3936 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 3937 "Definition of the Differentiated Services Field (DS 3938 Field) in the IPv4 and IPv6 Headers", RFC 2474, 3939 DOI 10.17487/RFC2474, December 1998, 3940 . 3942 [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol 3943 Label Switching Architecture", RFC 3031, 3944 DOI 10.17487/RFC3031, January 2001, 3945 . 3947 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 3948 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 3949 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 3950 . 3952 [RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation 3953 Metric for IP Performance Metrics (IPPM)", RFC 3393, 3954 DOI 10.17487/RFC3393, November 2002, 3955 . 3957 [RFC3411] Harrington, D., Presuhn, R., and B. Wijnen, "An 3958 Architecture for Describing Simple Network Management 3959 Protocol (SNMP) Management Frameworks", STD 62, RFC 3411, 3960 DOI 10.17487/RFC3411, December 2002, 3961 . 3963 [RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between 3964 Information Models and Data Models", RFC 3444, 3965 DOI 10.17487/RFC3444, January 2003, 3966 . 3968 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 3969 RFC 3972, DOI 10.17487/RFC3972, March 2005, 3970 . 3972 [RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation 3973 Edge-to-Edge (PWE3) Architecture", RFC 3985, 3974 DOI 10.17487/RFC3985, March 2005, 3975 . 3977 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 3978 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 3979 2006, . 3981 [RFC4553] Vainshtein, A., Ed. and YJ. Stein, Ed., "Structure- 3982 Agnostic Time Division Multiplexing (TDM) over Packet 3983 (SAToP)", RFC 4553, DOI 10.17487/RFC4553, June 2006, 3984 . 3986 [RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903, 3987 DOI 10.17487/RFC4903, June 2007, 3988 . 3990 [RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6 3991 over Low-Power Wireless Personal Area Networks (6LoWPANs): 3992 Overview, Assumptions, Problem Statement, and Goals", 3993 RFC 4919, DOI 10.17487/RFC4919, August 2007, 3994 . 3996 [RFC5086] Vainshtein, A., Ed., Sasson, I., Metz, E., Frost, T., and 3997 P. Pate, "Structure-Aware Time Division Multiplexed (TDM) 3998 Circuit Emulation Service over Packet Switched Network 3999 (CESoPSN)", RFC 5086, DOI 10.17487/RFC5086, December 2007, 4000 . 4002 [RFC5087] Stein, Y(J)., Shashoua, R., Insler, R., and M. Anavi, 4003 "Time Division Multiplexing over IP (TDMoIP)", RFC 5087, 4004 DOI 10.17487/RFC5087, December 2007, 4005 . 4007 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 4008 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 4009 DOI 10.17487/RFC6282, September 2011, 4010 . 4012 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 4013 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 4014 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 4015 Low-Power and Lossy Networks", RFC 6550, 4016 DOI 10.17487/RFC6550, March 2012, 4017 . 4019 [RFC6551] Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N., 4020 and D. Barthel, "Routing Metrics Used for Path Calculation 4021 in Low-Power and Lossy Networks", RFC 6551, 4022 DOI 10.17487/RFC6551, March 2012, 4023 . 4025 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 4026 Bormann, "Neighbor Discovery Optimization for IPv6 over 4027 Low-Power Wireless Personal Area Networks (6LoWPANs)", 4028 RFC 6775, DOI 10.17487/RFC6775, November 2012, 4029 . 4031 [RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using 4032 IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the 4033 Internet of Things (IoT): Problem Statement", RFC 7554, 4034 DOI 10.17487/RFC7554, May 2015, 4035 . 4037 [Spe09] Sperotto, A., Sadre, R., Vliet, F., and A. Pras, "A First 4038 Look into SCADA Network Traffic", IP Operations and 4039 Management, p. 518-521. , June 2009. 4041 [SRP_LATENCY] 4042 Gunther, C., "Specifying SRP Latency", 2014, 4043 . 4046 [STUDIO_IP] 4047 Mace, G., "IP Networked Studio Infrastructure for 4048 Synchronized & Real-Time Multimedia Transmissions", 2007, 4049 . 4052 [SyncE] ITU-T, "G.8261 : Timing and synchronization aspects in 4053 packet networks", Recommendation G.8261, August 2013, 4054 . 4056 [TEAS] IETF, "Traffic Engineering Architecture and Signaling", 4057 . 4059 [TR38801] IEEE Standards Association, "3GPP TR 38.801, Technical 4060 Specification Group Radio Access Network; Study on new 4061 radio access technology: Radio access architecture and 4062 interfaces (Release 14)", 2017, 4063 . 4066 [TS23401] 3GPP, "General Packet Radio Service (GPRS) enhancements 4067 for Evolved Universal Terrestrial Radio Access Network 4068 (E-UTRAN) access", 3GPP TS 23.401 10.10.0, March 2013. 4070 [TS25104] 3GPP, "Base Station (BS) radio transmission and reception 4071 (FDD)", 3GPP TS 25.104 3.14.0, March 2007. 4073 [TS36104] 3GPP, "Evolved Universal Terrestrial Radio Access 4074 (E-UTRA); Base Station (BS) radio transmission and 4075 reception", 3GPP TS 36.104 10.11.0, July 2013. 4077 [TS36133] 3GPP, "Evolved Universal Terrestrial Radio Access 4078 (E-UTRA); Requirements for support of radio resource 4079 management", 3GPP TS 36.133 12.7.0, April 2015. 4081 [TS36211] 3GPP, "Evolved Universal Terrestrial Radio Access 4082 (E-UTRA); Physical channels and modulation", 3GPP 4083 TS 36.211 10.7.0, March 2013. 4085 [TS36300] 3GPP, "Evolved Universal Terrestrial Radio Access (E-UTRA) 4086 and Evolved Universal Terrestrial Radio Access Network 4087 (E-UTRAN); Overall description; Stage 2", 3GPP TS 36.300 4088 10.11.0, September 2013. 4090 [TSNTG] IEEE Standards Association, "IEEE 802.1 Time-Sensitive 4091 Networks Task Group", 2013, 4092 . 4094 [UHD-video] 4095 Holub, P., "Ultra-High Definition Videos and Their 4096 Applications over the Network", The 7th International 4097 Symposium on VICTORIES Project PetrHolub_presentation, 4098 October 2014, . 4101 [WirelessHART] 4102 www.hartcomm.org, "Industrial Communication Networks - 4103 Wireless Communication Network and Communication Profiles 4104 - WirelessHART - IEC 62591", 2010. 4106 Author's Address 4108 Ethan Grossman (editor) 4109 Dolby Laboratories, Inc. 4110 1275 Market Street 4111 San Francisco, CA 94103 4112 USA 4114 Phone: +1 415 645 4726 4115 Email: ethan.grossman@dolby.com 4116 URI: http://www.dolby.com