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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 C. Gunther 5 Expires: August 25, 2016 HARMAN 6 P. Thubert 7 P. Wetterwald 8 CISCO 9 J. Raymond 10 HYDRO-QUEBEC 11 J. Korhonen 12 BROADCOM 13 Y. Kaneko 14 Toshiba 15 S. Das 16 Applied Communication Sciences 17 Y. Zha 18 HUAWEI 19 B. Varga 20 J. Farkas 21 Ericsson 22 F. Goetz 23 J. Schmitt 24 Siemens 25 February 22, 2016 27 Deterministic Networking Use Cases 28 draft-ietf-detnet-use-cases-04 30 Abstract 32 This draft documents requirements in several diverse industries to 33 establish multi-hop paths for characterized flows with deterministic 34 properties. In this context deterministic implies that streams can 35 be established which provide guaranteed bandwidth and latency which 36 can be established from either a Layer 2 or Layer 3 (IP) interface, 37 and which can co-exist on an IP network with best-effort traffic. 39 Additional requirements include optional redundant paths, very high 40 reliability paths, time synchronization, and clock distribution. 41 Industries considered include wireless for industrial applications, 42 professional audio, electrical utilities, building automation 43 systems, radio/mobile access networks, automotive, and gaming. 45 For each case, this document will identify the application, identify 46 representative solutions used today, and what new uses an IETF DetNet 47 solution may enable. 49 Status of This Memo 51 This Internet-Draft is submitted in full conformance with the 52 provisions of BCP 78 and BCP 79. 54 Internet-Drafts are working documents of the Internet Engineering 55 Task Force (IETF). Note that other groups may also distribute 56 working documents as Internet-Drafts. The list of current Internet- 57 Drafts is at http://datatracker.ietf.org/drafts/current/. 59 Internet-Drafts are draft documents valid for a maximum of six months 60 and may be updated, replaced, or obsoleted by other documents at any 61 time. It is inappropriate to use Internet-Drafts as reference 62 material or to cite them other than as "work in progress." 64 This Internet-Draft will expire on August 25, 2016. 66 Copyright Notice 68 Copyright (c) 2016 IETF Trust and the persons identified as the 69 document authors. All rights reserved. 71 This document is subject to BCP 78 and the IETF Trust's Legal 72 Provisions Relating to IETF Documents 73 (http://trustee.ietf.org/license-info) in effect on the date of 74 publication of this document. Please review these documents 75 carefully, as they describe your rights and restrictions with respect 76 to this document. Code Components extracted from this document must 77 include Simplified BSD License text as described in Section 4.e of 78 the Trust Legal Provisions and are provided without warranty as 79 described in the Simplified BSD License. 81 Table of Contents 83 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5 84 2. Pro Audio Use Cases . . . . . . . . . . . . . . . . . . . . . 5 85 2.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 5 86 2.2. Fundamental Stream Requirements . . . . . . . . . . . . . 6 87 2.2.1. Guaranteed Bandwidth . . . . . . . . . . . . . . . . 7 88 2.2.2. Bounded and Consistent Latency . . . . . . . . . . . 7 89 2.2.2.1. Optimizations . . . . . . . . . . . . . . . . . . 8 90 2.3. Additional Stream Requirements . . . . . . . . . . . . . 9 91 2.3.1. Deterministic Time to Establish Streaming . . . . . . 9 92 2.3.2. Use of Unused Reservations by Best-Effort Traffic . . 9 93 2.3.3. Layer 3 Interconnecting Layer 2 Islands . . . . . . . 10 94 2.3.4. Secure Transmission . . . . . . . . . . . . . . . . . 10 95 2.3.5. Redundant Paths . . . . . . . . . . . . . . . . . . . 10 96 2.3.6. Link Aggregation . . . . . . . . . . . . . . . . . . 11 97 2.3.7. Traffic Segregation . . . . . . . . . . . . . . . . . 11 98 2.3.7.1. Packet Forwarding Rules, VLANs and Subnets . . . 11 99 2.3.7.2. Multicast Addressing (IPv4 and IPv6) . . . . . . 11 100 2.4. Integration of Reserved Streams into IT Networks . . . . 12 101 2.5. Security Considerations . . . . . . . . . . . . . . . . . 12 102 2.5.1. Denial of Service . . . . . . . . . . . . . . . . . . 12 103 2.5.2. Control Protocols . . . . . . . . . . . . . . . . . . 12 104 2.6. A State-of-the-Art Broadcast Installation Hits Technology 105 Limits . . . . . . . . . . . . . . . . . . . . . . . . . 13 106 3. Utility Telecom Use Cases . . . . . . . . . . . . . . . . . . 13 107 3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 13 108 3.2. Telecommunications Trends and General telecommunications 109 Requirements . . . . . . . . . . . . . . . . . . . . . . 14 110 3.2.1. General Telecommunications Requirements . . . . . . . 14 111 3.2.1.1. Migration to Packet-Switched Network . . . . . . 15 112 3.2.2. Applications, Use cases and traffic patterns . . . . 16 113 3.2.2.1. Transmission use cases . . . . . . . . . . . . . 16 114 3.2.2.2. Distribution use case . . . . . . . . . . . . . . 26 115 3.2.2.3. Generation use case . . . . . . . . . . . . . . . 29 116 3.2.3. Specific Network topologies of Smart Grid 117 Applications . . . . . . . . . . . . . . . . . . . . 30 118 3.2.4. Precision Time Protocol . . . . . . . . . . . . . . . 31 119 3.3. IANA Considerations . . . . . . . . . . . . . . . . . . . 32 120 3.4. Security Considerations . . . . . . . . . . . . . . . . . 32 121 3.4.1. Current Practices and Their Limitations . . . . . . . 32 122 3.4.2. Security Trends in Utility Networks . . . . . . . . . 34 123 4. Building Automation Systems . . . . . . . . . . . . . . . . . 35 124 4.1. Use Case Description . . . . . . . . . . . . . . . . . . 35 125 4.2. Building Automation Systems Today . . . . . . . . . . . . 36 126 4.2.1. BAS Architecture . . . . . . . . . . . . . . . . . . 36 127 4.2.2. BAS Deployment Model . . . . . . . . . . . . . . . . 37 128 4.2.3. Use Cases for Field Networks . . . . . . . . . . . . 39 129 4.2.3.1. Environmental Monitoring . . . . . . . . . . . . 39 130 4.2.3.2. Fire Detection . . . . . . . . . . . . . . . . . 39 131 4.2.3.3. Feedback Control . . . . . . . . . . . . . . . . 40 132 4.2.4. Security Considerations . . . . . . . . . . . . . . . 40 133 4.3. BAS Future . . . . . . . . . . . . . . . . . . . . . . . 40 134 4.4. BAS Asks . . . . . . . . . . . . . . . . . . . . . . . . 41 135 5. Wireless for Industrial Use Cases . . . . . . . . . . . . . . 41 136 5.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 41 137 5.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 42 138 5.3. 6TiSCH Overview . . . . . . . . . . . . . . . . . . . . . 43 139 5.3.1. TSCH and 6top . . . . . . . . . . . . . . . . . . . . 46 140 5.3.2. SlotFrames and Priorities . . . . . . . . . . . . . . 46 141 5.3.3. Schedule Management by a PCE . . . . . . . . . . . . 46 142 5.3.4. Track Forwarding . . . . . . . . . . . . . . . . . . 47 143 5.3.4.1. Transport Mode . . . . . . . . . . . . . . . . . 49 144 5.3.4.2. Tunnel Mode . . . . . . . . . . . . . . . . . . . 50 145 5.3.4.3. Tunnel Metadata . . . . . . . . . . . . . . . . . 51 146 5.4. Operations of Interest for DetNet and PCE . . . . . . . . 51 147 5.4.1. Packet Marking and Handling . . . . . . . . . . . . . 52 148 5.4.1.1. Tagging Packets for Flow Identification . . . . . 52 149 5.4.1.2. Replication, Retries and Elimination . . . . . . 52 150 5.4.1.3. Differentiated Services Per-Hop-Behavior . . . . 53 151 5.4.2. Topology and capabilities . . . . . . . . . . . . . . 53 152 5.5. Security Considerations . . . . . . . . . . . . . . . . . 54 153 6. Cellular Radio Use Cases . . . . . . . . . . . . . . . . . . 54 154 6.1. Use Case Description . . . . . . . . . . . . . . . . . . 54 155 6.1.1. Network Architecture . . . . . . . . . . . . . . . . 54 156 6.1.2. Time Synchronization Requirements . . . . . . . . . . 55 157 6.1.3. Time-Sensitive Stream Requirements . . . . . . . . . 57 158 6.1.4. Security Considerations . . . . . . . . . . . . . . . 57 159 6.2. Cellular Radio Networks Today . . . . . . . . . . . . . . 58 160 6.3. Cellular Radio Networks Future . . . . . . . . . . . . . 58 161 6.4. Cellular Radio Networks Asks . . . . . . . . . . . . . . 60 162 7. Cellular Coordinated Multipoint Processing (CoMP) . . . . . . 60 163 7.1. Use Case Description . . . . . . . . . . . . . . . . . . 60 164 7.1.1. CoMP Architecture . . . . . . . . . . . . . . . . . . 61 165 7.1.2. Delay Sensitivity in CoMP . . . . . . . . . . . . . . 62 166 7.2. CoMP Today . . . . . . . . . . . . . . . . . . . . . . . 62 167 7.3. CoMP Future . . . . . . . . . . . . . . . . . . . . . . . 62 168 7.3.1. Mobile Industry Overall Goals . . . . . . . . . . . . 62 169 7.3.2. CoMP Infrastructure Goals . . . . . . . . . . . . . . 63 170 7.4. CoMP Asks . . . . . . . . . . . . . . . . . . . . . . . . 63 171 8. Industrial M2M . . . . . . . . . . . . . . . . . . . . . . . 64 172 8.1. Use Case Description . . . . . . . . . . . . . . . . . . 64 173 8.2. Industrial M2M Communication Today . . . . . . . . . . . 65 174 8.2.1. Transport Parameters . . . . . . . . . . . . . . . . 65 175 8.2.2. Stream Creation and Destruction . . . . . . . . . . . 66 176 8.3. Industrial M2M Future . . . . . . . . . . . . . . . . . . 66 177 8.4. Industrial M2M Asks . . . . . . . . . . . . . . . . . . . 67 178 9. Internet-based Applications . . . . . . . . . . . . . . . . . 67 179 9.1. Use Case Description . . . . . . . . . . . . . . . . . . 67 180 9.1.1. Media Content Delivery . . . . . . . . . . . . . . . 67 181 9.1.2. Online Gaming . . . . . . . . . . . . . . . . . . . . 67 182 9.1.3. Virtual Reality . . . . . . . . . . . . . . . . . . . 67 183 9.2. Internet-Based Applications Today . . . . . . . . . . . . 68 184 9.3. Internet-Based Applications Future . . . . . . . . . . . 68 185 9.4. Internet-Based Applications Asks . . . . . . . . . . . . 68 186 10. Use Case Common Elements . . . . . . . . . . . . . . . . . . 68 187 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 69 188 11.1. Pro Audio . . . . . . . . . . . . . . . . . . . . . . . 69 189 11.2. Utility Telecom . . . . . . . . . . . . . . . . . . . . 70 190 11.3. Building Automation Systems . . . . . . . . . . . . . . 70 191 11.4. Wireless for Industrial . . . . . . . . . . . . . . . . 70 192 11.5. Cellular Radio . . . . . . . . . . . . . . . . . . . . . 70 193 11.6. Industrial M2M . . . . . . . . . . . . . . . . . . . . . 70 194 11.7. Other . . . . . . . . . . . . . . . . . . . . . . . . . 70 195 12. Informative References . . . . . . . . . . . . . . . . . . . 71 196 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 79 198 1. Introduction 200 This draft presents use cases from diverse industries which have in 201 common a need for deterministic streams, but which also differ 202 notably in their network topologies and specific desired behavior. 203 Together, they provide broad industry context for DetNet and a 204 yardstick against which proposed DetNet designs can be measured (to 205 what extent does a proposed design satisfy these various use cases?) 207 For DetNet, use cases explicitly do not define requirements; The 208 DetNet WG will consider the use cases, decide which elements are in 209 scope for DetNet, and the results will be incorporated into future 210 drafts. Similarly, the DetNet use case draft explicitly does not 211 suggest any specific design, architecture or protocols, which will be 212 topics of future drafts. 214 We present for each use case the answers to the following questions: 216 o What is the use case? 218 o How is it addressed today? 220 o How would you like it to be addressed in the future? 222 o What do you want the IETF to deliver? 224 The level of detail in each use case should be sufficient to express 225 the relevant elements of the use case, but not more. 227 At the end we consider the use cases collectively, and examine the 228 most significant goals they have in common. 230 2. Pro Audio Use Cases 232 2.1. Introduction 234 The professional audio and video industry includes music and film 235 content creation, broadcast, cinema, and live exposition as well as 236 public address, media and emergency systems at large venues 237 (airports, stadiums, churches, theme parks). These industries have 238 already gone through the transition of audio and video signals from 239 analog to digital, however the interconnect systems remain primarily 240 point-to-point with a single (or small number of) signals per link, 241 interconnected with purpose-built hardware. 243 These industries are now attempting to transition to packet based 244 infrastructure for distributing audio and video in order to reduce 245 cost, increase routing flexibility, and integrate with existing IT 246 infrastructure. 248 However, there are several requirements for making a network the 249 primary infrastructure for audio and video which are not met by 250 todays networks and these are our concern in this draft. 252 The principal requirement is that pro audio and video applications 253 become able to establish streams that provide guaranteed (bounded) 254 bandwidth and latency from the Layer 3 (IP) interface. Such streams 255 can be created today within standards-based layer 2 islands however 256 these are not sufficient to enable effective distribution over wider 257 areas (for example broadcast events that span wide geographical 258 areas). 260 Some proprietary systems have been created which enable deterministic 261 streams at layer 3 however they are engineered networks in that they 262 require careful configuration to operate, often require that the 263 system be over designed, and it is implied that all devices on the 264 network voluntarily play by the rules of that network. To enable 265 these industries to successfully transition to an interoperable 266 multi-vendor packet-based infrastructure requires effective open 267 standards, and we believe that establishing relevant IETF standards 268 is a crucial factor. 270 It would be highly desirable if such streams could be routed over the 271 open Internet, however even intermediate solutions with more limited 272 scope (such as enterprise networks) can provide a substantial 273 improvement over todays networks, and a solution that only provides 274 for the enterprise network scenario is an acceptable first step. 276 We also present more fine grained requirements of the audio and video 277 industries such as safety and security, redundant paths, devices with 278 limited computing resources on the network, and that reserved stream 279 bandwidth is available for use by other best-effort traffic when that 280 stream is not currently in use. 282 2.2. Fundamental Stream Requirements 284 The fundamental stream properties are guaranteed bandwidth and 285 deterministic latency as described in this section. Additional 286 stream requirements are described in a subsequent section. 288 2.2.1. Guaranteed Bandwidth 290 Transmitting audio and video streams is unlike common file transfer 291 activities because guaranteed delivery cannot be achieved by re- 292 trying the transmission; by the time the missing or corrupt packet 293 has been identified it is too late to execute a re-try operation and 294 stream playback is interrupted, which is unacceptable in for example 295 a live concert. In some contexts large amounts of buffering can be 296 used to provide enough delay to allow time for one or more retries, 297 however this is not an effective solution when live interaction is 298 involved, and is not considered an acceptable general solution for 299 pro audio and video. (Have you ever tried speaking into a microphone 300 through a sound system that has an echo coming back at you? It makes 301 it almost impossible to speak clearly). 303 Providing a way to reserve a specific amount of bandwidth for a given 304 stream is a key requirement. 306 2.2.2. Bounded and Consistent Latency 308 Latency in this context means the amount of time that passes between 309 when a signal is sent over a stream and when it is received, for 310 example the amount of time delay between when you speak into a 311 microphone and when your voice emerges from the speaker. Any delay 312 longer than about 10-15 milliseconds is noticeable by most live 313 performers, and greater latency makes the system unusable because it 314 prevents them from playing in time with the other players (see slide 315 6 of [SRP_LATENCY]). 317 The 15ms latency bound is made even more challenging because it is 318 often the case in network based music production with live electric 319 instruments that multiple stages of signal processing are used, 320 connected in series (i.e. from one to the other for example from 321 guitar through a series of digital effects processors) in which case 322 the latencies add, so the latencies of each individual stage must all 323 together remain less than 15ms. 325 In some situations it is acceptable at the local location for content 326 from the live remote site to be delayed to allow for a statistically 327 acceptable amount of latency in order to reduce jitter. However, 328 once the content begins playing in the local location any audio 329 artifacts caused by the local network are unacceptable, especially in 330 those situations where a live local performer is mixed into the feed 331 from the remote location. 333 In addition to being bounded to within some predictable and 334 acceptable amount of time (which may be 15 milliseconds or more or 335 less depending on the application) the latency also has to be 336 consistent. For example when playing a film consisting of a video 337 stream and audio stream over a network, those two streams must be 338 synchronized so that the voice and the picture match up. A common 339 tolerance for audio/video sync is one NTSC video frame (about 33ms) 340 and to maintain the audience perception of correct lip sync the 341 latency needs to be consistent within some reasonable tolerance, for 342 example 10%. 344 A common architecture for synchronizing multiple streams that have 345 different paths through the network (and thus potentially different 346 latencies) is to enable measurement of the latency of each path, and 347 have the data sinks (for example speakers) buffer (delay) all packets 348 on all but the slowest path. Each packet of each stream is assigned 349 a presentation time which is based on the longest required delay. 350 This implies that all sinks must maintain a common time reference of 351 sufficient accuracy, which can be achieved by any of various 352 techniques. 354 This type of architecture is commonly implemented using a central 355 controller that determines path delays and arbitrates buffering 356 delays. 358 2.2.2.1. Optimizations 360 The controller might also perform optimizations based on the 361 individual path delays, for example sinks that are closer to the 362 source can inform the controller that they can accept greater latency 363 since they will be buffering packets to match presentation times of 364 farther away sinks. The controller might then move a stream 365 reservation on a short path to a longer path in order to free up 366 bandwidth for other critical streams on that short path. See slides 367 3-5 of [SRP_LATENCY]. 369 Additional optimization can be achieved in cases where sinks have 370 differing latency requirements, for example in a live outdoor concert 371 the speaker sinks have stricter latency requirements than the 372 recording hardware sinks. See slide 7 of [SRP_LATENCY]. 374 Device cost can be reduced in a system with guaranteed reservations 375 with a small bounded latency due to the reduced requirements for 376 buffering (i.e. memory) on sink devices. For example, a theme park 377 might broadcast a live event across the globe via a layer 3 protocol; 378 in such cases the size of the buffers required is proportional to the 379 latency bounds and jitter caused by delivery, which depends on the 380 worst case segment of the end-to-end network path. For example on 381 todays open internet the latency is typically unacceptable for audio 382 and video streaming without many seconds of buffering. In such 383 scenarios a single gateway device at the local network that receives 384 the feed from the remote site would provide the expensive buffering 385 required to mask the latency and jitter issues associated with long 386 distance delivery. Sink devices in the local location would have no 387 additional buffering requirements, and thus no additional costs, 388 beyond those required for delivery of local content. The sink device 389 would be receiving the identical packets as those sent by the source 390 and would be unaware that there were any latency or jitter issues 391 along the path. 393 2.3. Additional Stream Requirements 395 The requirements in this section are more specific yet are common to 396 multiple audio and video industry applications. 398 2.3.1. Deterministic Time to Establish Streaming 400 Some audio systems installed in public environments (airports, 401 hospitals) have unique requirements with regards to health, safety 402 and fire concerns. One such requirement is a maximum of 3 seconds 403 for a system to respond to an emergency detection and begin sending 404 appropriate warning signals and alarms without human intervention. 405 For this requirement to be met, the system must support a bounded and 406 acceptable time from a notification signal to specific stream 407 establishment. For further details see [ISO7240-16]. 409 Similar requirements apply when the system is restarted after a power 410 cycle, cable re-connection, or system reconfiguration. 412 In many cases such re-establishment of streaming state must be 413 achieved by the peer devices themselves, i.e. without a central 414 controller (since such a controller may only be present during 415 initial network configuration). 417 Video systems introduce related requirements, for example when 418 transitioning from one camera feed to another. Such systems 419 currently use purpose-built hardware to switch feeds smoothly, 420 however there is a current initiative in the broadcast industry to 421 switch to a packet-based infrastructure (see [STUDIO_IP] and the ESPN 422 DC2 use case described below). 424 2.3.2. Use of Unused Reservations by Best-Effort Traffic 426 In cases where stream bandwidth is reserved but not currently used 427 (or is under-utilized) that bandwidth must be available to best- 428 effort (i.e. non-time-sensitive) traffic. For example a single 429 stream may be nailed up (reserved) for specific media content that 430 needs to be presented at different times of the day, ensuring timely 431 delivery of that content, yet in between those times the full 432 bandwidth of the network can be utilized for best-effort tasks such 433 as file transfers. 435 This also addresses a concern of IT network administrators that are 436 considering adding reserved bandwidth traffic to their networks that 437 users will just reserve a ton of bandwidth and then never un-reserve 438 it even though they are not using it, and soon they will have no 439 bandwidth left. 441 2.3.3. Layer 3 Interconnecting Layer 2 Islands 443 As an intermediate step (short of providing guaranteed bandwidth 444 across the open internet) it would be valuable to provide a way to 445 connect multiple Layer 2 networks. For example layer 2 techniques 446 could be used to create a LAN for a single broadcast studio, and 447 several such studios could be interconnected via layer 3 links. 449 2.3.4. Secure Transmission 451 Digital Rights Management (DRM) is very important to the audio and 452 video industries. Any time protected content is introduced into a 453 network there are DRM concerns that must be maintained (see 454 [CONTENT_PROTECTION]). Many aspects of DRM are outside the scope of 455 network technology, however there are cases when a secure link 456 supporting authentication and encryption is required by content 457 owners to carry their audio or video content when it is outside their 458 own secure environment (for example see [DCI]). 460 As an example, two techniques are Digital Transmission Content 461 Protection (DTCP) and High-Bandwidth Digital Content Protection 462 (HDCP). HDCP content is not approved for retransmission within any 463 other type of DRM, while DTCP may be retransmitted under HDCP. 464 Therefore if the source of a stream is outside of the network and it 465 uses HDCP protection it is only allowed to be placed on the network 466 with that same HDCP protection. 468 2.3.5. Redundant Paths 470 On-air and other live media streams must be backed up with redundant 471 links that seamlessly act to deliver the content when the primary 472 link fails for any reason. In point-to-point systems this is 473 provided by an additional point-to-point link; the analogous 474 requirement in a packet-based system is to provide an alternate path 475 through the network such that no individual link can bring down the 476 system. 478 2.3.6. Link Aggregation 480 For transmitting streams that require more bandwidth than a single 481 link in the target network can support, link aggregation is a 482 technique for combining (aggregating) the bandwidth available on 483 multiple physical links to create a single logical link of the 484 required bandwidth. However, if aggregation is to be used, the 485 network controller (or equivalent) must be able to determine the 486 maximum latency of any path through the aggregate link (see Bounded 487 and Consistent Latency section above). 489 2.3.7. Traffic Segregation 491 Sink devices may be low cost devices with limited processing power. 492 In order to not overwhelm the CPUs in these devices it is important 493 to limit the amount of traffic that these devices must process. 495 As an example, consider the use of individual seat speakers in a 496 cinema. These speakers are typically required to be cost reduced 497 since the quantities in a single theater can reach hundreds of seats. 498 Discovery protocols alone in a one thousand seat theater can generate 499 enough broadcast traffic to overwhelm a low powered CPU. Thus an 500 installation like this will benefit greatly from some type of traffic 501 segregation that can define groups of seats to reduce traffic within 502 each group. All seats in the theater must still be able to 503 communicate with a central controller. 505 There are many techniques that can be used to support this 506 requirement including (but not limited to) the following examples. 508 2.3.7.1. Packet Forwarding Rules, VLANs and Subnets 510 Packet forwarding rules can be used to eliminate some extraneous 511 streaming traffic from reaching potentially low powered sink devices, 512 however there may be other types of broadcast traffic that should be 513 eliminated using other means for example VLANs or IP subnets. 515 2.3.7.2. Multicast Addressing (IPv4 and IPv6) 517 Multicast addressing is commonly used to keep bandwidth utilization 518 of shared links to a minimum. 520 Because of the MAC Address forwarding nature of Layer 2 bridges it is 521 important that a multicast MAC address is only associated with one 522 stream. This will prevent reservations from forwarding packets from 523 one stream down a path that has no interested sinks simply because 524 there is another stream on that same path that shares the same 525 multicast MAC address. 527 Since each multicast MAC Address can represent 32 different IPv4 528 multicast addresses there must be a process put in place to make sure 529 this does not occur. Requiring use of IPv6 address can achieve this, 530 however due to their continued prevalence, solutions that are 531 effective for IPv4 installations are also required. 533 2.4. Integration of Reserved Streams into IT Networks 535 A commonly cited goal of moving to a packet based media 536 infrastructure is that costs can be reduced by using off the shelf, 537 commodity network hardware. In addition, economy of scale can be 538 realized by combining media infrastructure with IT infrastructure. 539 In keeping with these goals, stream reservation technology should be 540 compatible with existing protocols, and not compromise use of the 541 network for best effort (non-time-sensitive) traffic. 543 2.5. Security Considerations 545 Many industries that are moving from the point-to-point world to the 546 digital network world have little understanding of the pitfalls that 547 they can create for themselves with improperly implemented network 548 infrastructure. DetNet should consider ways to provide security 549 against DoS attacks in solutions directed at these markets. Some 550 considerations are given here as examples of ways that we can help 551 new users avoid common pitfalls. 553 2.5.1. Denial of Service 555 One security pitfall that this author is aware of involves the use of 556 technology that allows a presenter to throw the content from their 557 tablet or smart phone onto the A/V system that is then viewed by all 558 those in attendance. The facility introducing this technology was 559 quite excited to allow such modern flexibility to those who came to 560 speak. One thing they hadn't realized was that since no security was 561 put in place around this technology it left a hole in the system that 562 allowed other attendees to "throw" their own content onto the A/V 563 system. 565 2.5.2. Control Protocols 567 Professional audio systems can include amplifiers that are capable of 568 generating hundreds or thousands of watts of audio power which if 569 used incorrectly can cause hearing damage to those in the vicinity. 570 Apart from the usual care required by the systems operators to 571 prevent such incidents, the network traffic that controls these 572 devices must be secured (as with any sensitive application traffic). 573 In addition, it would be desirable if the configuration protocols 574 that are used to create the network paths used by the professional 575 audio traffic could be designed to protect devices that are not meant 576 to receive high-amplitude content from having such potentially 577 damaging signals routed to them. 579 2.6. A State-of-the-Art Broadcast Installation Hits Technology Limits 581 ESPN recently constructed a state-of-the-art 194,000 sq ft, $125 582 million broadcast studio called DC2. The DC2 network is capable of 583 handling 46 Tbps of throughput with 60,000 simultaneous signals. 584 Inside the facility are 1,100 miles of fiber feeding four audio 585 control rooms. (See details at [ESPN_DC2] ). 587 In designing DC2 they replaced as much point-to-point technology as 588 they possibly could with packet-based technology. They constructed 589 seven individual studios using layer 2 LANS (using IEEE 802.1 AVB) 590 that were entirely effective at routing audio within the LANs, and 591 they were very happy with the results, however to interconnect these 592 layer 2 LAN islands together they ended up using dedicated links 593 because there is no standards-based routing solution available. 595 This is the kind of motivation we have to develop these standards 596 because customers are ready and able to use them. 598 3. Utility Telecom Use Cases 600 3.1. Overview 602 [I-D.finn-detnet-problem-statement] defines the characteristics of a 603 deterministic flow as a data communication flow with a bounded 604 latency, extraordinarily low frame loss, and a very narrow jitter. 605 This document intends to define the utility requirements for 606 deterministic networking. 608 Utility Telecom Networks 610 The business and technology trends that are sweeping the utility 611 industry will drastically transform the utility business from the way 612 it has been for many decades. At the core of many of these changes 613 is a drive to modernize the electrical grid with an integrated 614 telecommunications infrastructure. However, interoperability, 615 concerns, legacy networks, disparate tools, and stringent security 616 requirements all add complexity to the grid transformation. Given 617 the range and diversity of the requirements that should be addressed 618 by the next generation telecommunications infrastructure, utilities 619 need to adopt a holistic architectural approach to integrate the 620 electrical grid with digital telecommunications across the entire 621 power delivery chain. 623 Many utilities still rely on complex environments formed of multiple 624 application-specific, proprietary networks. Information is siloed 625 between operational areas. This prevents utility operations from 626 realizing the operational efficiency benefits, visibility, and 627 functional integration of operational information across grid 628 applications and data networks. The key to modernizing grid 629 telecommunications is to provide a common, adaptable, multi-service 630 network infrastructure for the entire utility organization. Such a 631 network serves as the platform for current capabilities while 632 enabling future expansion of the network to accommodate new 633 applications and services. 635 To meet this diverse set of requirements, both today and in the 636 future, the next generation utility telecommunnications network will 637 be based on open-standards-based IP architecture. An end-to-end IP 638 architecture takes advantage of nearly three decades of IP technology 639 development, facilitating interoperability across disparate networks 640 and devices, as it has been already demonstrated in many mission- 641 critical and highly secure networks. 643 IEC (International Electrotechnical Commission) and different 644 National Committees have mandated a specific adhoc group (AHG8) to 645 define the migration strategy to IPv6 for all the IEC TC57 power 646 automation standards. IPv6 is seen as the obvious future 647 telecommunications technology for the Smart Grid. The Adhoc Group 648 has disclosed, to the IEC coordination group, their conclusions at 649 the end of 2014. 651 It is imperative that utilities participate in standards development 652 bodies to influence the development of future solutions and to 653 benefit from shared experiences of other utilities and vendors. 655 3.2. Telecommunications Trends and General telecommunications 656 Requirements 658 These general telecommunications requirements are over and above the 659 specific requirements of the use cases that have been addressed so 660 far. These include both current and future telecommunications 661 related requirements that should be factored into the network 662 architecture and design. 664 3.2.1. General Telecommunications Requirements 666 o IP Connectivity everywhere 668 o Monitoring services everywhere and from different remote centers 670 o Move services to a virtual data center 671 o Unify access to applications / information from the corporate 672 network 674 o Unify services 676 o Unified Communications Solutions 678 o Mix of fiber and microwave technologies - obsolescence of SONET/ 679 SDH or TDM 681 o Standardize grid telecommunications protocol to opened standard to 682 ensure interoperability 684 o Reliable Telecommunications for Transmission and Distribution 685 Substations 687 o IEEE 1588 time synchronization Client / Server Capabilities 689 o Integration of Multicast Design 691 o QoS Requirements Mapping 693 o Enable Future Network Expansion 695 o Substation Network Resilience 697 o Fast Convergence Design 699 o Scalable Headend Design 701 o Define Service Level Agreements (SLA) and Enable SLA Monitoring 703 o Integration of 3G/4G Technologies and future technologies 705 o Ethernet Connectivity for Station Bus Architecture 707 o Ethernet Connectivity for Process Bus Architecture 709 o Protection, teleprotection and PMU (Phaser Measurement Unit) on IP 711 3.2.1.1. Migration to Packet-Switched Network 713 Throughout the world, utilities are increasingly planning for a 714 future based on smart grid applications requiring advanced 715 telecommunications systems. Many of these applications utilize 716 packet connectivity for communicating information and control signals 717 across the utility's Wide Area Network (WAN), made possible by 718 technologies such as multiprotocol label switching (MPLS). The data 719 that traverses the utility WAN includes: 721 o Grid monitoring, control, and protection data 723 o Non-control grid data (e.g. asset data for condition-based 724 monitoring) 726 o Physical safety and security data (e.g. voice and video) 728 o Remote worker access to corporate applications (voice, maps, 729 schematics, etc.) 731 o Field area network backhaul for smart metering, and distribution 732 grid management 734 o Enterprise traffic (email, collaboration tools, business 735 applications) 737 WANs support this wide variety of traffic to and from substations, 738 the transmission and distribution grid, generation sites, between 739 control centers, and between work locations and data centers. To 740 maintain this rapidly expanding set of applications, many utilities 741 are taking steps to evolve present time-division multiplexing (TDM) 742 based and frame relay infrastructures to packet systems. Packet- 743 based networks are designed to provide greater functionalities and 744 higher levels of service for applications, while continuing to 745 deliver reliability and deterministic (real-time) traffic support. 747 3.2.2. Applications, Use cases and traffic patterns 749 Among the numerous applications and use cases that a utility deploys 750 today, many rely on high availability and deterministic behaviour of 751 the telecommunications networks. Protection use cases and generation 752 control are the most demanding and can't rely on a best effort 753 approach. 755 3.2.2.1. Transmission use cases 757 Protection means not only the protection of the human operator but 758 also the protection of the electric equipments and the preservation 759 of the stability and frequency of the grid. If a default occurs on 760 the transmission or the distribution of the electricity, important 761 damages could occured to the human operator but also to very costly 762 electrical equipments and perturb the grid leading to blackouts. The 763 time and reliability requirements are very strong to avoid dramatic 764 impacts to the electrical infrastructure. 766 3.2.2.1.1. Tele Protection 768 The key criteria for measuring Teleprotection performance are command 769 transmission time, dependability and security. These criteria are 770 defined by the IEC standard 60834 as follows: 772 o Transmission time (Speed): The time between the moment where state 773 changes at the transmitter input and the moment of the 774 corresponding change at the receiver output, including propagation 775 delay. Overall operating time for a Teleprotection system 776 includes the time for initiating the command at the transmitting 777 end, the propagation delay over the network (including equipments) 778 and the selection and decision time at the receiving end, 779 including any additional delay due to a noisy environment. 781 o Dependability: The ability to issue and receive valid commands in 782 the presence of interference and/or noise, by minimizing the 783 probability of missing command (PMC). Dependability targets are 784 typically set for a specific bit error rate (BER) level. 786 o Security: The ability to prevent false tripping due to a noisy 787 environment, by minimizing the probability of unwanted commands 788 (PUC). Security targets are also set for a specific bit error 789 rate (BER) level. 791 Additional key elements that may impact Teleprotection performance 792 include bandwidth rate of the Teleprotection system and its 793 resiliency or failure recovery capacity. Transmission time, 794 bandwidth utilization and resiliency are directly linked to the 795 telecommunications equipments and the connections that are used to 796 transfer the commands between relays. 798 3.2.2.1.1.1. Latency Budget Consideration 800 Delay requirements for utility networks may vary depending upon a 801 number of parameters, such as the specific protection equipments 802 used. Most power line equipment can tolerate short circuits or 803 faults for up to approximately five power cycles before sustaining 804 irreversible damage or affecting other segments in the network. This 805 translates to total fault clearance time of 100ms. As a safety 806 precaution, however, actual operation time of protection systems is 807 limited to 70- 80 percent of this period, including fault recognition 808 time, command transmission time and line breaker switching time. 809 Some system components, such as large electromechanical switches, 810 require particularly long time to operate and take up the majority of 811 the total clearance time, leaving only a 10ms window for the 812 telecommunications part of the protection scheme, independent of the 813 distance to travel. Given the sensitivity of the issue, new networks 814 impose requirements that are even more stringent: IEC standard 61850 815 limits the transfer time for protection messages to 1/4 - 1/2 cycle 816 or 4 - 8ms (for 60Hz lines) for the most critical messages. 818 3.2.2.1.1.2. Asymetric delay 820 In addition to minimal transmission delay, a differential protection 821 telecommunications channel must be synchronous, i.e., experiencing 822 symmetrical channel delay in transmit and receive paths. This 823 requires special attention in jitter-prone packet networks. While 824 optimally Teleprotection systems should support zero asymmetric 825 delay, typical legacy relays can tolerate discrepancies of up to 826 750us. 828 The main tools available for lowering delay variation below this 829 threshold are: 831 o A jitter buffer at the multiplexers on each end of the line can be 832 used to offset delay variation by queuing sent and received 833 packets. The length of the queues must balance the need to 834 regulate the rate of transmission with the need to limit overall 835 delay, as larger buffers result in increased latency. This is the 836 old TDM traditional way to fulfill this requirement. 838 o Traffic management tools ensure that the Teleprotection signals 839 receive the highest transmission priority and minimize the number 840 of jitter addition during the path. This is one way to meet the 841 requirement in IP networks. 843 o Standard Packet-Based synchronization technologies, such as 844 1588-2008 Precision Time Protocol (PTP) and Synchronous Ethernet 845 (Sync-E), can help maintain stable networks by keeping a highly 846 accurate clock source on the different network devices involved. 848 3.2.2.1.1.2.1. Other traffic characteristics 850 o Redundancy: The existence in a system of more than one means of 851 accomplishing a given function. 853 o Recovery time : The duration of time within which a business 854 process must be restored after any type of disruption in order to 855 avoid unacceptable consequences associated with a break in 856 business continuity. 858 o performance management : In networking, a management function 859 defined for controlling and analyzing different parameters/metrics 860 such as the throughput, error rate. 862 o packet loss : One or more packets of data travelling across 863 network fail to reach their destination. 865 3.2.2.1.1.2.2. Teleprotection network requirements 867 The following table captures the main network requirements (this is 868 based on IEC 61850 standard) 870 +-----------------------------+-------------------------------------+ 871 | Teleprotection Requirement | Attribute | 872 +-----------------------------+-------------------------------------+ 873 | One way maximum delay | 4-10 ms | 874 | Asymetric delay required | Yes | 875 | Maximum jitter | less than 250 us (750 us for legacy | 876 | | IED) | 877 | Topology | Point to point, point to Multi- | 878 | | point | 879 | Availability | 99.9999 | 880 | precise timing required | Yes | 881 | Recovery time on node | less than 50ms - hitless | 882 | failure | | 883 | performance management | Yes, Mandatory | 884 | Redundancy | Yes | 885 | Packet loss | 0.1% to 1% | 886 +-----------------------------+-------------------------------------+ 888 Table 1: Teleprotection network requirements 890 3.2.2.1.2. Inter-Trip Protection scheme 892 Inter-tripping is the controlled tripping of a circuit breaker to 893 complete the isolation of a circuit or piece of apparatus in concert 894 with the tripping of other circuit breakers. The main use of such 895 schemes is to ensure that protection at both ends of a faulted 896 circuit will operate to isolate the equipment concerned. Inter- 897 tripping schemes use signaling to convey a trip command to remote 898 circuit breakers to isolate circuits. 900 +--------------------------------+----------------------------------+ 901 | Inter-Trip protection | Attribute | 902 | Requirement | | 903 +--------------------------------+----------------------------------+ 904 | One way maximum delay | 5 ms | 905 | Asymetric delay required | No | 906 | Maximum jitter | Not critical | 907 | Topology | Point to point, point to Multi- | 908 | | point | 909 | Bandwidth | 64 Kbps | 910 | Availability | 99.9999 | 911 | precise timing required | Yes | 912 | Recovery time on node failure | less than 50ms - hitless | 913 | performance management | Yes, Mandatory | 914 | Redundancy | Yes | 915 | Packet loss | 0.1% | 916 +--------------------------------+----------------------------------+ 918 Table 2: Inter-Trip protection network requirements 920 3.2.2.1.3. Current Differential Protection Scheme 922 Current differential protection is commonly used for line protection, 923 and is typical for protecting parallel circuits. A main advantage 924 for differential protection is that, compared to overcurrent 925 protection, it allows only the faulted circuit to be de-energized in 926 case of a fault. At both end of the lines, the current is measured 927 by the differential relays, and based on Kirchhoff's law, both relays 928 will trip the circuit breaker if the current going into the line does 929 not equal the current going out of the line. This type of protection 930 scheme assumes some form of communications being present between the 931 relays at both end of the line, to allow both relays to compare 932 measured current values. A fault in line 1 will cause overcurrent to 933 be flowing in both lines, but because the current in line 2 is a 934 through following current, this current is measured equal at both 935 ends of the line, therefore the differential relays on line 2 will 936 not trip line 2. Line 1 will be tripped, as the relays will not 937 measure the same currents at both ends of the line. Line 938 differential protection schemes assume a very low telecommunications 939 delay between both relays, often as low as 5ms. Moreover, as those 940 systems are often not time-synchronized, they also assume symmetric 941 telecommunications paths with constant delay, which allows comparing 942 current measurement values taken at the exact same time. 944 +----------------------------------+--------------------------------+ 945 | Current Differential protection | Attribute | 946 | Requirement | | 947 +----------------------------------+--------------------------------+ 948 | One way maximum delay | 5 ms | 949 | Asymetric delay Required | Yes | 950 | Maximum jitter | less than 250 us (750us for | 951 | | legacy IED) | 952 | Topology | Point to point, point to | 953 | | Multi-point | 954 | Bandwidth | 64 Kbps | 955 | Availability | 99.9999 | 956 | precise timing required | Yes | 957 | Recovery time on node failure | less than 50ms - hitless | 958 | performance management | Yes, Mandatory | 959 | Redundancy | Yes | 960 | Packet loss | 0.1% | 961 +----------------------------------+--------------------------------+ 963 Table 3: Current Differential Protection requirements 965 3.2.2.1.4. Distance Protection Scheme 967 Distance (Impedance Relay) protection scheme is based on voltage and 968 current measurements. A fault on a circuit will generally create a 969 sag in the voltage level. If the ratio of voltage to current 970 measured at the protection relay terminals, which equates to an 971 impedance element, falls within a set threshold the circuit breaker 972 will operate. The operating characteristics of this protection are 973 based on the line characteristics. This means that when a fault 974 appears on the line, the impedance setting in the relay is compared 975 to the apparent impedance of the line from the relay terminals to the 976 fault. If the relay setting is determined to be below the apparent 977 impedance it is determined that the fault is within the zone of 978 protection. When the transmission line length is under a minimum 979 length, distance protection becomes more difficult to coordinate. In 980 these instances the best choice of protection is current differential 981 protection. 983 +-------------------------------+-----------------------------------+ 984 | Distance protection | Attribute | 985 | Requirement | | 986 +-------------------------------+-----------------------------------+ 987 | One way maximum delay | 5 ms | 988 | Asymetric delay Required | No | 989 | Maximum jitter | Not critical | 990 | Topology | Point to point, point to Multi- | 991 | | point | 992 | Bandwidth | 64 Kbps | 993 | Availability | 99.9999 | 994 | precise timing required | Yes | 995 | Recovery time on node failure | less than 50ms - hitless | 996 | performance management | Yes, Mandatory | 997 | Redundancy | Yes | 998 | Packet loss | 0.1% | 999 +-------------------------------+-----------------------------------+ 1001 Table 4: Distance Protection requirements 1003 3.2.2.1.5. Inter-Substation Protection Signaling 1005 This use case describes the exchange of Sampled Value and/or GOOSE 1006 (Generic Object Oriented Substation Events) message between 1007 Intelligent Electronic Devices (IED) in two substations for 1008 protection and tripping coordination. The two IEDs are in a master- 1009 slave mode. 1011 The Current Transformer or Voltage Transformer (CT/VT) in one 1012 substation sends the sampled analog voltage or current value to the 1013 Merging Unit (MU) over hard wire. The merging unit sends the time- 1014 synchronized 61850-9-2 sampled values to the slave IED. The slave 1015 IED forwards the information to the Master IED in the other 1016 substation. The master IED makes the determination (for example 1017 based on sampled value differentials) to send a trip command to the 1018 originating IED. Once the slave IED/Relay receives the GOOSE trip 1019 for breaker tripping, it opens the breaker. It then sends a 1020 confirmation message back to the master. All data exchanges between 1021 IEDs are either through Sampled Value and/or GOOSE messages. 1023 +----------------------------------+--------------------------------+ 1024 | Inter-Substation protection | Attribute | 1025 | Requirement | | 1026 +----------------------------------+--------------------------------+ 1027 | One way maximum delay | 5 ms | 1028 | Asymetric delay Required | No | 1029 | Maximum jitter | Not critical | 1030 | Topology | Point to point, point to | 1031 | | Multi-point | 1032 | Bandwidth | 64 Kbps | 1033 | Availability | 99.9999 | 1034 | precise timing required | Yes | 1035 | Recovery time on node failure | less than 50ms - hitless | 1036 | performance management | Yes, Mandatory | 1037 | Redundancy | Yes | 1038 | Packet loss | 1% | 1039 +----------------------------------+--------------------------------+ 1041 Table 5: Inter-Substation Protection requirements 1043 3.2.2.1.6. Intra-Substation Process Bus Communications 1045 This use case describes the data flow from the CT/VT to the IEDs in 1046 the substation via the merging unit (MU). The CT/VT in the 1047 substation send the sampled value (analog voltage or current) to the 1048 Merging Unit (MU) over hard wire. The merging unit sends the time- 1049 synchronized 61850-9-2 sampled values to the IEDs in the substation 1050 in GOOSE message format. The GPS Master Clock can send 1PPS or 1051 IRIG-B format to MU through serial port, or IEEE 1588 protocol via 1052 network. Process bus communication using 61850 simplifies 1053 connectivity within the substation and removes the requirement for 1054 multiple serial connections and removes the slow serial bus 1055 architectures that are typically used. This also ensures increased 1056 flexibility and increased speed with the use of multicast messaging 1057 between multiple devices. 1059 +----------------------------------+--------------------------------+ 1060 | Intra-Substation protection | Attribute | 1061 | Requirement | | 1062 +----------------------------------+--------------------------------+ 1063 | One way maximum delay | 5 ms | 1064 | Asymetric delay Required | No | 1065 | Maximum jitter | Not critical | 1066 | Topology | Point to point, point to | 1067 | | Multi-point | 1068 | Bandwidth | 64 Kbps | 1069 | Availability | 99.9999 | 1070 | precise timing required | Yes | 1071 | Recovery time on Node failure | less than 50ms - hitless | 1072 | performance management | Yes, Mandatory | 1073 | Redundancy | Yes - No | 1074 | Packet loss | 0.1% | 1075 +----------------------------------+--------------------------------+ 1077 Table 6: Intra-Substation Protection requirements 1079 3.2.2.1.7. Wide Area Monitoring and Control Systems 1081 The application of synchrophasor measurement data from Phasor 1082 Measurement Units (PMU) to Wide Area Monitoring and Control Systems 1083 promises to provide important new capabilities for improving system 1084 stability. Access to PMU data enables more timely situational 1085 awareness over larger portions of the grid than what has been 1086 possible historically with normal SCADA (Supervisory Control and Data 1087 Acquisition) data. Handling the volume and real-time nature of 1088 synchrophasor data presents unique challenges for existing 1089 application architectures. Wide Area management System (WAMS) makes 1090 it possible for the condition of the bulk power system to be observed 1091 and understood in real-time so that protective, preventative, or 1092 corrective action can be taken. Because of the very high sampling 1093 rate of measurements and the strict requirement for time 1094 synchronization of the samples, WAMS has stringent telecommunications 1095 requirements in an IP network that are captured in the following 1096 table: 1098 +----------------------+--------------------------------------------+ 1099 | WAMS Requirement | Attribute | 1100 +----------------------+--------------------------------------------+ 1101 | One way maximum | 50 ms | 1102 | delay | | 1103 | Asymetric delay | No | 1104 | Required | | 1105 | Maximum jitter | Not critical | 1106 | Topology | Point to point, point to Multi-point, | 1107 | | Multi-point to Multi-point | 1108 | Bandwidth | 100 Kbps | 1109 | Availability | 99.9999 | 1110 | precise timing | Yes | 1111 | required | | 1112 | Recovery time on | less than 50ms - hitless | 1113 | Node failure | | 1114 | performance | Yes, Mandatory | 1115 | management | | 1116 | Redundancy | Yes | 1117 | Packet loss | 1% | 1118 +----------------------+--------------------------------------------+ 1120 Table 7: WAMS Special Communication Requirements 1122 3.2.2.1.8. IEC 61850 WAN engineering guidelines requirement 1123 classification 1125 The IEC (International Electrotechnical Commission) has recently 1126 published a Technical Report which offers guidelines on how to define 1127 and deploy Wide Area Networks for the interconnections of electric 1128 substations, generation plants and SCADA operation centers. The IEC 1129 61850-90-12 is providing a classification of WAN communication 1130 requirements into 4 classes. You will find herafter the table 1131 summarizing these requirements: 1133 +----------------+------------+------------+------------+-----------+ 1134 | WAN | Class WA | Class WB | Class WC | Class WD | 1135 | Requirement | | | | | 1136 +----------------+------------+------------+------------+-----------+ 1137 | Application | EHV (Extra | HV (High | MV (Medium | General | 1138 | field | High | Voltage) | Voltage) | purpose | 1139 | | Voltage) | | | | 1140 | Latency | 5 ms | 10 ms | 100 ms | > 100 ms | 1141 | Jitter | 10 us | 100 us | 1 ms | 10 ms | 1142 | Latency | 100 us | 1 ms | 10 ms | 100 ms | 1143 | Asymetry | | | | | 1144 | Time Accuracy | 1 us | 10 us | 100 us | 10 to 100 | 1145 | | | | | ms | 1146 | Bit Error rate | 10-7 to | 10-5 to | 10-3 | | 1147 | | 10-6 | 10-4 | | | 1148 | Unavailability | 10-7 to | 10-5 to | 10-3 | | 1149 | | 10-6 | 10-4 | | | 1150 | Recovery delay | Zero | 50 ms | 5 s | 50 s | 1151 | Cyber security | extremely | High | Medium | Medium | 1152 | | high | | | | 1153 +----------------+------------+------------+------------+-----------+ 1155 Table 8: 61850-90-12 Communication Requirements; Courtesy of IEC 1157 3.2.2.2. Distribution use case 1159 3.2.2.2.1. Fault Location Isolation and Service Restoration (FLISR) 1161 As the name implies, Fault Location, Isolation, and Service 1162 Restoration (FLISR) refers to the ability to automatically locate the 1163 fault, isolate the fault, and restore service in the distribution 1164 network. It is a self-healing feature whose purpose is to minimize 1165 the impact of faults by serving portions of the loads on the affected 1166 circuit by switching to other circuits. It reduces the number of 1167 customers that experience a sustained power outage by reconfiguring 1168 distribution circuits. This will likely be the first wide spread 1169 application of distributed intelligence in the grid. Secondary 1170 substations can be connected to multiple primary substations. 1171 Normally, static power switch statuses (open/closed) in the network 1172 dictate the power flow to secondary substations. Reconfiguring the 1173 network in the event of a fault is typically done manually on site to 1174 operate switchgear to energize/de-energize alternate paths. 1175 Automating the operation of substation switchgear allows the utility 1176 to have a more dynamic network where the flow of power can be altered 1177 under fault conditions but also during times of peak load. It allows 1178 the utility to shift peak loads around the network. Or, to be more 1179 precise, alters the configuration of the network to move loads 1180 between different primary substations. The FLISR capability can be 1181 enabled in two modes: 1183 o Managed centrally from DMS (Distribution Management System), or 1185 o Executed locally through distributed control via intelligent 1186 switches and fault sensors. 1188 There are 3 distinct sub-functions that are performed: 1190 1. Fault Location Identification 1192 This sub-function is initiated by SCADA inputs, such as lockouts, 1193 fault indications/location, and, also, by input from the Outage 1194 Management System (OMS), and in the future by inputs from fault- 1195 predicting devices. It determines the specific protective device, 1196 which has cleared the sustained fault, identifies the de-energized 1197 sections, and estimates the probable location of the actual or the 1198 expected fault. It distinguishes faults cleared by controllable 1199 protective devices from those cleared by fuses, and identifies 1200 momentary outages and inrush/cold load pick-up currents. This step 1201 is also referred to as Fault Detection Classification and Location 1202 (FDCL). This step helps to expedite the restoration of faulted 1203 sections through fast fault location identification and improved 1204 diagnostic information available for crew dispatch. Also provides 1205 visualization of fault information to design and implement a 1206 switching plan to isolate the fault. 1208 2. Fault Type Determination 1210 I. Indicates faults cleared by controllable protective devices by 1211 distinguishing between: 1213 a. Faults cleared by fuses 1215 b. Momentary outages 1217 c. Inrush/cold load current 1219 II. Determines the faulted sections based on SCADA fault indications 1220 and protection lockout signals 1222 III. Increases the accuracy of the fault location estimation based 1223 on SCADA fault current measurements and real-time fault analysis 1225 3. Fault Isolation and Service Restoration 1226 Once the location and type of the fault has been pinpointed, the 1227 systems will attempt to isolate the fault and restore the non-faulted 1228 section of the network. This can have three modes of operation: 1230 I. Closed-loop mode : This is initiated by the Fault location sub- 1231 function. It generates a switching order (i.e., sequence of 1232 switching) for the remotely controlled switching devices to isolate 1233 the faulted section, and restore service to the non-faulted sections. 1234 The switching order is automatically executed via SCADA. 1236 II. Advisory mode : This is initiated by the Fault location sub- 1237 function. It generates a switching order for remotely and manually 1238 controlled switching devices to isolate the faulted section, and 1239 restore service to the non-faulted sections. The switching order is 1240 presented to operator for approval and execution. 1242 III. Study mode : the operator initiates this function. It analyzes 1243 a saved case modified by the operator, and generates a switching 1244 order under the operating conditions specified by the operator. 1246 With the increasing volume of data that are collected through fault 1247 sensors, utilities will use Big Data query and analysis tools to 1248 study outage information to anticipate and prevent outages by 1249 detecting failure patterns and their correlation with asset age, 1250 type, load profiles, time of day, weather conditions, and other 1251 conditions to discover conditions that lead to faults and take the 1252 necessary preventive and corrective measures. 1254 +----------------------+--------------------------------------------+ 1255 | FLISR Requirement | Attribute | 1256 +----------------------+--------------------------------------------+ 1257 | One way maximum | 80 ms | 1258 | delay | | 1259 | Asymetric delay | No | 1260 | Required | | 1261 | Maximum jitter | 40 ms | 1262 | Topology | Point to point, point to Multi-point, | 1263 | | Multi-point to Multi-point | 1264 | Bandwidth | 64 Kbps | 1265 | Availability | 99.9999 | 1266 | precise timing | Yes | 1267 | required | | 1268 | Recovery time on | Depends on customer impact | 1269 | Node failure | | 1270 | performance | Yes, Mandatory | 1271 | management | | 1272 | Redundancy | Yes | 1273 | Packet loss | 0.1% | 1274 +----------------------+--------------------------------------------+ 1276 Table 9: FLISR Communication Requirements 1278 3.2.2.3. Generation use case 1280 3.2.2.3.1. Frequency Control / Automatic Generation Control (AGC) 1282 The system frequency should be maintained within a very narrow band. 1283 Deviations from the acceptable frequency range are detected and 1284 forwarded to the Load Frequency Control (LFC) system so that required 1285 up or down generation increase / decrease pulses can be sent to the 1286 power plants for frequency regulation. The trend in system frequency 1287 is a measure of mismatch between demand and generation, and is a 1288 necessary parameter for load control in interconnected systems. 1290 Automatic generation control (AGC) is a system for adjusting the 1291 power output of generators at different power plants, in response to 1292 changes in the load. Since a power grid requires that generation and 1293 load closely balance moment by moment, frequent adjustments to the 1294 output of generators are necessary. The balance can be judged by 1295 measuring the system frequency; if it is increasing, more power is 1296 being generated than used, and all machines in the system are 1297 accelerating. If the system frequency is decreasing, more demand is 1298 on the system than the instantaneous generation can provide, and all 1299 generators are slowing down. 1301 Where the grid has tie lines to adjacent control areas, automatic 1302 generation control helps maintain the power interchanges over the tie 1303 lines at the scheduled levels. The AGC takes into account various 1304 parameters including the most economical units to adjust, the 1305 coordination of thermal, hydroelectric, and other generation types, 1306 and even constraints related to the stability of the system and 1307 capacity of interconnections to other power grids. 1309 For the purpose of AGC we use static frequency measurements and 1310 averaging methods are used to get a more precise measure of system 1311 frequency in steady-state conditions. 1313 During disturbances, more real-time dynamic measurements of system 1314 frequency are taken using PMUs, especially when different areas of 1315 the system exhibit different frequencies. But that is outside the 1316 scope of this use case. 1318 +---------------------------------------------------+---------------+ 1319 | FCAG (Frequency Control Automatic Generation) | Attribute | 1320 | Requirement | | 1321 +---------------------------------------------------+---------------+ 1322 | One way maximum delay | 500 ms | 1323 | Asymetric delay Required | No | 1324 | Maximum jitter | Not critical | 1325 | Topology | Point to | 1326 | | point | 1327 | Bandwidth | 20 Kbps | 1328 | Availability | 99.999 | 1329 | precise timing required | Yes | 1330 | Recovery time on Node failure | N/A | 1331 | performance management | Yes, | 1332 | | Mandatory | 1333 | Redundancy | Yes | 1334 | Packet loss | 1% | 1335 +---------------------------------------------------+---------------+ 1337 Table 10: FCAG Communication Requirements 1339 3.2.3. Specific Network topologies of Smart Grid Applications 1341 Utilities often have very large private telecommunications networks. 1342 It covers an entire territory / country. The main purpose of the 1343 network, until now, has been to support transmission network 1344 monitoring, control, and automation, remote control of generation 1345 sites, and providing FCAPS (Fault. Configuration. Accounting. 1346 Performance. Security) services from centralized network operation 1347 centers. 1349 Going forward, one network will support operation and maintenance of 1350 electrical networks (generation, transmission, and distribution), 1351 voice and data services for ten of thousands of employees and for 1352 exchange with neighboring interconnections, and administrative 1353 services. To meet those requirements, utility may deploy several 1354 physical networks leveraging different technologies across the 1355 country: an optical network and a microwave network for instance. 1356 Each protection and automatism system between two points has two 1357 telecommunications circuits, one on each network. Path diversity 1358 between two substations is key. Regardless of the event type 1359 (hurricane, ice storm, etc.), one path shall stay available so the 1360 SPS can still operate. 1362 In the optical network, signals are transmitted over more than tens 1363 of thousands of circuits using fiber optic links, microwave and 1364 telephone cables. This network is the nervous system of the 1365 utility's power transmission operations. The optical network 1366 represents ten of thousands of km of cable deployed along the power 1367 lines. 1369 Due to vast distances between transmission substations (for example 1370 as far as 280km apart), the fiber signal can be amplified to reach a 1371 distance of 280 km without attenuation. 1373 3.2.4. Precision Time Protocol 1375 Some utilities do not use GPS clocks in generation substations. One 1376 of the main reasons is that some of the generation plants are 30 to 1377 50 meters deep under ground and the GPS signal can be weak and 1378 unreliable. Instead, atomic clocks are used. Clocks are 1379 synchronized amongst each other. Rubidium clocks provide clock and 1380 1ms timestamps for IRIG-B. Some companies plan to transition to the 1381 Precision Time Protocol (IEEE 1588), distributing the synchronization 1382 signal over the IP/MPLS network. 1384 The Precision Time Protocol (PTP) is defined in IEEE standard 1588. 1385 PTP is applicable to distributed systems consisting of one or more 1386 nodes, communicating over a network. Nodes are modeled as containing 1387 a real-time clock that may be used by applications within the node 1388 for various purposes such as generating time-stamps for data or 1389 ordering events managed by the node. The protocol provides a 1390 mechanism for synchronizing the clocks of participating nodes to a 1391 high degree of accuracy and precision. 1393 PTP operates based on the following assumptions : 1395 It is assumed that the network eliminates cyclic forwarding of PTP 1396 messages within each communication path (e.g., by using a spanning 1397 tree protocol). PTP eliminates cyclic forwarding of PTP messages 1398 between communication paths. 1400 PTP is tolerant of an occasional missed message, duplicated 1401 message, or message that arrived out of order. However, PTP 1402 assumes that such impairments are relatively rare. 1404 PTP was designed assuming a multicast communication model. PTP 1405 also supports a unicast communication model as long as the 1406 behavior of the protocol is preserved. 1408 Like all message-based time transfer protocols, PTP time accuracy 1409 is degraded by asymmetry in the paths taken by event messages. 1410 Asymmetry is not detectable by PTP, however, if known, PTP 1411 corrects for asymmetry. 1413 A time-stamp event is generated at the time of transmission and 1414 reception of any event message. The time-stamp event occurs when the 1415 message's timestamp point crosses the boundary between the node and 1416 the network. 1418 IEC 61850 will recommend the use of the IEEE PTP 1588 Utility Profile 1419 (as defined in IEC 62439-3 Annex B) which offers the support of 1420 redundant attachment of clocks to Paralell Redundancy Protcol (PRP) 1421 and High-availability Seamless Redundancy (HSR) networks. 1423 3.3. IANA Considerations 1425 This memo includes no request to IANA. 1427 3.4. Security Considerations 1429 3.4.1. Current Practices and Their Limitations 1431 Grid monitoring and control devices are already targets for cyber 1432 attacks and legacy telecommunications protocols have many intrinsic 1433 network related vulnerabilities. DNP3, Modbus, PROFIBUS/PROFINET, 1434 and other protocols are designed around a common paradigm of request 1435 and respond. Each protocol is designed for a master device such as 1436 an HMI (Human Machine Interface) system to send commands to 1437 subordinate slave devices to retrieve data (reading inputs) or 1438 control (writing to outputs). Because many of these protocols lack 1439 authentication, encryption, or other basic security measures, they 1440 are prone to network-based attacks, allowing a malicious actor or 1441 attacker to utilize the request-and-respond system as a mechanism for 1442 command-and-control like functionality. Specific security concerns 1443 common to most industrial control, including utility 1444 telecommunication protocols include the following: 1446 o Network or transport errors (e.g. malformed packets or excessive 1447 latency) can cause protocol failure. 1449 o Protocol commands may be available that are capable of forcing 1450 slave devices into inoperable states, including powering-off 1451 devices, forcing them into a listen-only state, disabling 1452 alarming. 1454 o Protocol commands may be available that are capable of restarting 1455 communications and otherwise interrupting processes. 1457 o Protocol commands may be available that are capable of clearing, 1458 erasing, or resetting diagnostic information such as counters and 1459 diagnostic registers. 1461 o Protocol commands may be available that are capable of requesting 1462 sensitive information about the controllers, their configurations, 1463 or other need-to-know information. 1465 o Most protocols are application layer protocols transported over 1466 TCP; therefore it is easy to transport commands over non-standard 1467 ports or inject commands into authorized traffic flows. 1469 o Protocol commands may be available that are capable of 1470 broadcasting messages to many devices at once (i.e. a potential 1471 DoS). 1473 o Protocol commands may be available to query the device network to 1474 obtain defined points and their values (i.e. a configuration 1475 scan). 1477 o Protocol commands may be available that will list all available 1478 function codes (i.e. a function scan). 1480 o Bump in the wire (BITW) solutions : A hardware device is added to 1481 provide IPSec services between two routers that are not capable of 1482 IPSec functions. This special IPsec device will intercept then 1483 intercept outgoing datagrams, add IPSec protection to them, and 1484 strip it off incoming datagrams. BITW can all IPSec to legacy 1485 hosts and can retrofit non-IPSec routers to provide security 1486 benefits. The disadvantages are complexity and cost. 1488 These inherent vulnerabilities, along with increasing connectivity 1489 between IT an OT networks, make network-based attacks very feasible. 1490 Simple injection of malicious protocol commands provides control over 1491 the target process. Altering legitimate protocol traffic can also 1492 alter information about a process and disrupt the legitimate controls 1493 that are in place over that process. A man- in-the-middle attack 1494 could provide both control over a process and misrepresentation of 1495 data back to operator consoles. 1497 3.4.2. Security Trends in Utility Networks 1499 Although advanced telecommunications networks can assist in 1500 transforming the energy industry, playing a critical role in 1501 maintaining high levels of reliability, performance, and 1502 manageability, they also introduce the need for an integrated 1503 security infrastructure. Many of the technologies being deployed to 1504 support smart grid projects such as smart meters and sensors can 1505 increase the vulnerability of the grid to attack. Top security 1506 concerns for utilities migrating to an intelligent smart grid 1507 telecommunications platform center on the following trends: 1509 o Integration of distributed energy resources 1511 o Proliferation of digital devices to enable management, automation, 1512 protection, and control 1514 o Regulatory mandates to comply with standards for critical 1515 infrastructure protection 1517 o Migration to new systems for outage management, distribution 1518 automation, condition-based maintenance, load forecasting, and 1519 smart metering 1521 o Demand for new levels of customer service and energy management 1523 This development of a diverse set of networks to support the 1524 integration of microgrids, open-access energy competition, and the 1525 use of network-controlled devices is driving the need for a converged 1526 security infrastructure for all participants in the smart grid, 1527 including utilities, energy service providers, large commercial and 1528 industrial, as well as residential customers. Securing the assets of 1529 electric power delivery systems, from the control center to the 1530 substation, to the feeders and down to customer meters, requires an 1531 end-to-end security infrastructure that protects the myriad of 1532 telecommunications assets used to operate, monitor, and control power 1533 flow and measurement. Cyber security refers to all the security 1534 issues in automation and telecommunications that affect any functions 1535 related to the operation of the electric power systems. 1536 Specifically, it involves the concepts of: 1538 o Integrity : data cannot be altered undetectably 1540 o Authenticity : the telecommunications parties involved must be 1541 validated as genuine 1543 o Authorization : only requests and commands from the authorized 1544 users can be accepted by the system 1546 o Confidentiality : data must not be accessible to any 1547 unauthenticated users 1549 When designing and deploying new smart grid devices and 1550 telecommunications systems, it's imperative to understand the various 1551 impacts of these new components under a variety of attack situations 1552 on the power grid. Consequences of a cyber attack on the grid 1553 telecommunications network can be catastrophic. This is why security 1554 for smart grid is not just an ad hoc feature or product, it's a 1555 complete framework integrating both physical and Cyber security 1556 requirements and covering the entire smart grid networks from 1557 generation to distribution. Security has therefore become one of the 1558 main foundations of the utility telecom network architecture and must 1559 be considered at every layer with a defense-in-depth approach. 1560 Migrating to IP based protocols is key to address these challenges 1561 for two reasons: 1563 1. IP enables a rich set of features and capabilities to enhance the 1564 security posture 1566 2. IP is based on open standards, which allows interoperability 1567 between different vendors and products, driving down the costs 1568 associated with implementing security solutions in OT networks. 1570 Securing OT (Operation technology) telecommunications over packet- 1571 switched IP networks follow the same principles that are foundational 1572 for securing the IT infrastructure, i.e., consideration must be given 1573 to enforcing electronic access control for both person-to-machine and 1574 machine-to-machine communications, and providing the appropriate 1575 levels of data privacy, device and platform integrity, and threat 1576 detection and mitigation. 1578 4. Building Automation Systems 1580 4.1. Use Case Description 1582 A Building Automation System (BAS) manages equipment and sensors in a 1583 building for improving residents' comfort, reducing energy 1584 consumption, and responding to failures and emergencies. For 1585 example, the BAS measures the temperature of a room using sensors and 1586 then controls the HVAC (heating, ventilating, and air conditioning) 1587 to maintain a set temperature and minimize energy consumption. 1589 A BAS primarily performs the following functions: 1591 o Periodically measures states of devices, for example humidity and 1592 illuminance of rooms, open/close state of doors, FAN speed, etc. 1594 o Stores the measured data. 1596 o Provides the measured data to BAS systems and operators. 1598 o Generates alarms for abnormal state of devices. 1600 o Controls devices (e.g. turn off room lights at 10:00 PM). 1602 4.2. Building Automation Systems Today 1604 4.2.1. BAS Architecture 1606 A typical BAS architecture of today is shown in Figure 1. 1608 +----------------------------+ 1609 | | 1610 | BMS HMI | 1611 | | | | 1612 | +----------------------+ | 1613 | | Management Network | | 1614 | +----------------------+ | 1615 | | | | 1616 | LC LC | 1617 | | | | 1618 | +----------------------+ | 1619 | | Field Network | | 1620 | +----------------------+ | 1621 | | | | | | 1622 | Dev Dev Dev Dev | 1623 | | 1624 +----------------------------+ 1626 BMS := Building Management Server 1627 HMI := Human Machine Interface 1628 LC := Local Controller 1630 Figure 1: BAS architecture 1632 There are typically two layers of network in a BAS. The upper one is 1633 called the Management Network and the lower one is called the Field 1634 Network. In management networks an IP-based communication protocol 1635 is used, while in field networks non-IP based communication protocols 1636 ("field protocols") are mainly used. Field networks have specific 1637 timing requirements, whereas management networks can be best-effort. 1639 A Human Machine Interface (HMI) is typically a desktop PC used by 1640 operators to monitor and display device states, send device control 1641 commands to Local Controllers (LCs), and configure building schedules 1642 (for example "turn off all room lights in the building at 10:00 PM"). 1644 A Building Management Server (BMS) performs the following operations. 1646 o Collect and store device states from LCs at regular intervals. 1648 o Send control values to LCs according to a building schedule. 1650 o Send an alarm signal to operators if it detects abnormal devices 1651 states. 1653 The BMS and HMI communicate with LCs via IP-based "management 1654 protocols" (see standards [bacnetip], [knx]). 1656 A LC is typically a Programmable Logic Controller (PLC) which is 1657 connected to several tens or hundreds of devices using "field 1658 protocols". An LC performs the following kinds of operations: 1660 o Measure device states and provide the information to BMS or HMI. 1662 o Send control values to devices, unilaterally or as part of a 1663 feedback control loop. 1665 There are many field protocols used today; some are standards-based 1666 and others are proprietary (see standards [lontalk], [modbus], 1667 [profibus] and [flnet]). The result is that BASs have multiple MAC/ 1668 PHY modules and interfaces. This makes BASs more expensive, slower 1669 to develop, and can result in "vendor lock-in" with multiple types of 1670 management applications. 1672 4.2.2. BAS Deployment Model 1674 An example BAS for medium or large buildings is shown in Figure 2. 1675 The physical layout spans multiple floors, and there is a monitoring 1676 room where the BAS management entities are located. Each floor will 1677 have one or more LCs depending upon the number of devices connected 1678 to the field network. 1680 +--------------------------------------------------+ 1681 | Floor 3 | 1682 | +----LC~~~~+~~~~~+~~~~~+ | 1683 | | | | | | 1684 | | Dev Dev Dev | 1685 | | | 1686 |--- | ------------------------------------------| 1687 | | Floor 2 | 1688 | +----LC~~~~+~~~~~+~~~~~+ Field Network | 1689 | | | | | | 1690 | | Dev Dev Dev | 1691 | | | 1692 |--- | ------------------------------------------| 1693 | | Floor 1 | 1694 | +----LC~~~~+~~~~~+~~~~~+ +-----------------| 1695 | | | | | | Monitoring Room | 1696 | | Dev Dev Dev | | 1697 | | | BMS HMI | 1698 | | Management Network | | | | 1699 | +--------------------------------+-----+ | 1700 | | | 1701 +--------------------------------------------------+ 1703 Figure 2: BAS Deployment model for Medium/Large Buildings 1705 Each LC is connected to the monitoring room via the Management 1706 network, and the management functions are performed within the 1707 building. In most cases, fast Ethernet (e.g. 100BASE-T) is used for 1708 the management network. Since the management network is non- 1709 realtime, use of Ethernet without quality of service is sufficient 1710 for today's deployment. 1712 In the field network a variety of physical interfaces such as RS232C 1713 and RS485 are used, which have specific timing requirements. Thus if 1714 a field network is to be replaced with an Ethernet or wireless 1715 network, such networks must support time-critical deterministic 1716 flows. 1718 In Figure 3, another deployment model is presented in which the 1719 management system is hosted remotely. This is becoming popular for 1720 small office and residential buildings in which a standalone 1721 monitoring system is not cost-effective. 1723 +---------------+ 1724 | Remote Center | 1725 | | 1726 | BMS HMI | 1727 +------------------------------------+ | | | | 1728 | Floor 2 | | +---+---+ | 1729 | +----LC~~~~+~~~~~+ Field Network| | | | 1730 | | | | | | Router | 1731 | | Dev Dev | +-------|-------+ 1732 | | | | 1733 |--- | ------------------------------| | 1734 | | Floor 1 | | 1735 | +----LC~~~~+~~~~~+ | | 1736 | | | | | | 1737 | | Dev Dev | | 1738 | | | | 1739 | | Management Network | WAN | 1740 | +------------------------Router-------------+ 1741 | | 1742 +------------------------------------+ 1744 Figure 3: Deployment model for Small Buildings 1746 Some interoperability is possible today in the Management Network, 1747 but not in today's field networks due to their non-IP-based design. 1749 4.2.3. Use Cases for Field Networks 1751 Below are use cases for Environmental Monitoring, Fire Detection, and 1752 Feedback Control, and their implications for field network 1753 performance. 1755 4.2.3.1. Environmental Monitoring 1757 The BMS polls each LC at a maximum measurement interval of 100ms (for 1758 example to draw a historical chart of 1 second granularity with a 10x 1759 sampling interval) and then performs the operations as specified by 1760 the operator. Each LC needs to measure each of its several hundred 1761 sensors once per measurement interval. Latency is not critical in 1762 this scenario as long as all sensor values are completed in the 1763 measurement interval. Availability is expected to be 99.999 %. 1765 4.2.3.2. Fire Detection 1767 On detection of a fire, the BMS must stop the HVAC, close the fire 1768 shutters, turn on the fire sprinklers, send an alarm, etc. There are 1769 typically ~10s of sensors per LC that BMS needs to manage. In this 1770 scenario the measurement interval is 10-50ms, the communication delay 1771 is 10ms, and the availability must be 99.9999 %. 1773 4.2.3.3. Feedback Control 1775 BAS systems utilize feedback control in various ways; the most time- 1776 critial is control of DC motors, which require a short feedback 1777 interval (1-5ms) with low communication delay (10ms) and jitter 1778 (1ms). The feedback interval depends on the characteristics of the 1779 device and a target quality of control value. There are typically 1780 ~10s of such devices per LC. 1782 Communication delay is expected to be less than 10 ms, jitter less 1783 than 1 sec while the availability must be 99.9999% . 1785 4.2.4. Security Considerations 1787 When BAS field networks were developed it was assumed that the field 1788 networks would always be physically isolated from external networks 1789 and therefore security was not a concern. In today's world many BASs 1790 are managed remotely and are thus connected to shared IP networks and 1791 so security is definitely a concern, yet security features are not 1792 available in the majority of BAS field network deployments . 1794 The management network, being an IP-based network, has the protocols 1795 available to enable network security, but in practice many BAS 1796 systems do not implement even the available security features such as 1797 device authentication or encryption for data in transit. 1799 4.3. BAS Future 1801 In the future we expect more fine-grained environmental monitoring 1802 and lower energy consumption, which will require more sensors and 1803 devices, thus requiring larger and more complex building networks. 1805 We expect building networks to be connected to or converged with 1806 other networks (Enterprise network, Home network, and Internet). 1808 Therefore better facilities for network management, control, 1809 reliability and security are critical in order to improve resident 1810 and operator convenience and comfort. For example the ability to 1811 monitor and control building devices via the internet would enable 1812 (for example) control of room lights or HVAC from a resident's 1813 desktop PC or phone application. 1815 4.4. BAS Asks 1817 The community would like to see an interoperable protocol 1818 specification that can satisfy the timing, security, availability and 1819 QoS constraints described above, such that the resulting converged 1820 network can replace the disparate field networks. Ideally this 1821 connectivity could extend to the open Internet. 1823 This would imply an architecture that can guarantee 1825 o Low communication delays (from <10ms to 100ms in a network of 1826 several hundred devices) 1828 o Low jitter (< 1 ms) 1830 o Tight feedback intervals (1ms - 10ms) 1832 o High network availability (up to 99.9999% ) 1834 o Availability of network data in disaster scenario 1836 o Authentication between management and field devices (both local 1837 and remote) 1839 o Integrity and data origin authentication of communication data 1840 between field and management devices 1842 o Confidentiality of data when communicated to a remote device 1844 5. Wireless for Industrial Use Cases 1846 (This section was derived from draft-thubert-6tisch-4detnet-01) 1848 5.1. Introduction 1850 The emergence of wireless technology has enabled a variety of new 1851 devices to get interconnected, at a very low marginal cost per 1852 device, at any distance ranging from Near Field to interplanetary, 1853 and in circumstances where wiring may not be practical, for instance 1854 on fast-moving or rotating devices. 1856 At the same time, a new breed of Time Sensitive Networks is being 1857 developed to enable traffic that is highly sensitive to jitter, quite 1858 sensitive to latency, and with a high degree of operational 1859 criticality so that loss should be minimized at all times. Such 1860 traffic is not limited to professional Audio/ Video networks, but is 1861 also found in command and control operations such as industrial 1862 automation and vehicular sensors and actuators. 1864 At IEEE802.1, the Audio/Video Task Group [IEEE802.1TSNTG] Time 1865 Sensitive Networking (TSN) to address Deterministic Ethernet. The 1866 Medium access Control (MAC) of IEEE802.15.4 [IEEE802154] has evolved 1867 with the new TimeSlotted Channel Hopping (TSCH) [RFC7554] mode for 1868 deterministic industrial-type applications. TSCH was introduced with 1869 the IEEE802.15.4e [IEEE802154e] amendment and will be wrapped up in 1870 the next revision of the IEEE802.15.4 standard. For all practical 1871 purpose, this document is expected to be insensitive to the future 1872 versions of the IEEE802.15.4 standard, which is thus referenced 1873 undated. 1875 Though at a different time scale, both TSN and TSCH standards provide 1876 Deterministic capabilities to the point that a packet that pertains 1877 to a certain flow crosses the network from node to node following a 1878 very precise schedule, as a train that leaves intermediate stations 1879 at precise times along its path. With TSCH, time is formatted into 1880 timeSlots, and an individual cell is allocated to unicast or 1881 broadcast communication at the MAC level. The time-slotted operation 1882 reduces collisions, saves energy, and enables to more closely 1883 engineer the network for deterministic properties. The channel 1884 hopping aspect is a simple and efficient technique to combat multi- 1885 path fading and co-channel interferences (for example by Wi-Fi 1886 emitters). 1888 The 6TiSCH Architecture [I-D.ietf-6tisch-architecture] defines a 1889 remote monitoring and scheduling management of a TSCH network by a 1890 Path Computation Element (PCE), which cooperates with an abstract 1891 Network Management Entity (NME) to manage timeSlots and device 1892 resources in a manner that minimizes the interaction with and the 1893 load placed on the constrained devices. 1895 This Architecture applies the concepts of Deterministic Networking on 1896 a TSCH network to enable the switching of timeSlots in a G-MPLS 1897 manner. This document details the dependencies that 6TiSCH has on 1898 PCE [PCE] and DetNet [I-D.finn-detnet-architecture] to provide the 1899 necessary capabilities that may be specific to such networks. In 1900 turn, DetNet is expected to integrate and maintain consistency with 1901 the work that has taken place and is continuing at IEEE802.1TSN and 1902 AVnu. 1904 5.2. Terminology 1906 Readers are expected to be familiar with all the terms and concepts 1907 that are discussed in "Multi-link Subnet Support in IPv6" 1908 [I-D.ietf-ipv6-multilink-subnets]. 1910 The draft uses terminology defined or referenced in 1911 [I-D.ietf-6tisch-terminology] and 1912 [I-D.ietf-roll-rpl-industrial-applicability]. 1914 The draft also conforms to the terms and models described in 1915 [RFC3444] and uses the vocabulary and the concepts defined in 1916 [RFC4291] for the IPv6 Architecture. 1918 5.3. 6TiSCH Overview 1920 The scope of the present work is a subnet that, in its basic 1921 configuration, is made of a TSCH [RFC7554] MAC Low Power Lossy 1922 Network (LLN). 1924 ---+-------- ............ ------------ 1925 | External Network | 1926 | +-----+ 1927 +-----+ | NME | 1928 | | LLN Border | | 1929 | | router +-----+ 1930 +-----+ 1931 o o o 1932 o o o o 1933 o o LLN o o o 1934 o o o o 1935 o 1937 Figure 4: Basic Configuration of a 6TiSCH Network 1939 In the extended configuration, a Backbone Router (6BBR) federates 1940 multiple 6TiSCH in a single subnet over a backbone. 6TiSCH 6BBRs 1941 synchronize with one another over the backbone, so as to ensure that 1942 the multiple LLNs that form the IPv6 subnet stay tightly 1943 synchronized. 1945 ---+-------- ............ ------------ 1946 | External Network | 1947 | +-----+ 1948 | +-----+ | NME | 1949 +-----+ | +-----+ | | 1950 | | Router | | PCE | +-----+ 1951 | | +--| | 1952 +-----+ +-----+ 1953 | | 1954 | Subnet Backbone | 1955 +--------------------+------------------+ 1956 | | | 1957 +-----+ +-----+ +-----+ 1958 | | Backbone | | Backbone | | Backbone 1959 o | | router | | router | | router 1960 +-----+ +-----+ +-----+ 1961 o o o o o 1962 o o o o o o o o o o o 1963 o o o LLN o o o o 1964 o o o o o o o o o o o o 1966 Figure 5: Extended Configuration of a 6TiSCH Network 1968 If the Backbone is Deterministic, then the Backbone Router ensures 1969 that the end-to-end deterministic behavior is maintained between the 1970 LLN and the backbone. This SHOULD be done in conformance to the 1971 DetNet Architecture [I-D.finn-detnet-architecture] which studies 1972 Layer-3 aspects of Deterministic Networks, and covers networks that 1973 span multiple Layer-2 domains. One particular requirement is that 1974 the PCE MUST be able to compute a deterministic path and to end 1975 across the TSCH network and an IEEE802.1 TSN Ethernet backbone, and 1976 DetNet MUST enable end-to-end deterministic forwarding. 1978 6TiSCH defines the concept of a Track, which is a complex form of a 1979 uni-directional Circuit ([I-D.ietf-6tisch-terminology]). As opposed 1980 to a simple circuit that is a sequence of nodes and links, a Track is 1981 shaped as a directed acyclic graph towards a destination to support 1982 multi-path forwarding and route around failures. A Track may also 1983 branch off and rejoin, for the purpose of the so-called Packet 1984 Replication and Elimination (PRE), over non congruent branches. PRE 1985 may be used to complement layer-2 Automatic Repeat reQuest (ARQ) to 1986 meet industrial expectations in Packet Delivery Ratio (PDR), in 1987 particular when the Track extends beyond the 6TiSCH network. 1989 +-----+ 1990 | IoT | 1991 | G/W | 1992 +-----+ 1993 ^ <---- Elimination 1994 | | 1995 Track branch | | 1996 +-------+ +--------+ Subnet Backbone 1997 | | 1998 +--|--+ +--|--+ 1999 | | | Backbone | | | Backbone 2000 o | | | router | | | router 2001 +--/--+ +--|--+ 2002 o / o o---o----/ o 2003 o o---o--/ o o o o o 2004 o \ / o o LLN o 2005 o v <---- Replication 2006 o 2008 Figure 6: End-to-End deterministic Track 2010 In the example above, a Track is laid out from a field device in a 2011 6TiSCH network to an IoT gateway that is located on a IEEE802.1 TSN 2012 backbone. 2014 The Replication function in the field device sends a copy of each 2015 packet over two different branches, and the PCE schedules each hop of 2016 both branches so that the two copies arrive in due time at the 2017 gateway. In case of a loss on one branch, hopefully the other copy 2018 of the packet still makes it in due time. If two copies make it to 2019 the IoT gateway, the Elimination function in the gateway ignores the 2020 extra packet and presents only one copy to upper layers. 2022 At each 6TiSCH hop along the Track, the PCE may schedule more than 2023 one timeSlot for a packet, so as to support Layer-2 retries (ARQ). 2024 It is also possible that the field device only uses the second branch 2025 if sending over the first branch fails. 2027 In current deployments, a TSCH Track does not necessarily support PRE 2028 but is systematically multi-path. This means that a Track is 2029 scheduled so as to ensure that each hop has at least two forwarding 2030 solutions, and the forwarding decision is to try the preferred one 2031 and use the other in case of Layer-2 transmission failure as detected 2032 by ARQ. 2034 5.3.1. TSCH and 6top 2036 6top is a logical link control sitting between the IP layer and the 2037 TSCH MAC layer, which provides the link abstraction that is required 2038 for IP operations. The 6top operations are specified in 2039 [I-D.wang-6tisch-6top-sublayer]. 2041 The 6top data model and management interfaces are further discussed 2042 in [I-D.ietf-6tisch-6top-interface] and [I-D.ietf-6tisch-coap]. 2044 The architecture defines "soft" cells and "hard" cells. "Hard" cells 2045 are owned and managed by an separate scheduling entity (e.g. a PCE) 2046 that specifies the slotOffset/channelOffset of the cells to be 2047 added/moved/deleted, in which case 6top can only act as instructed, 2048 and may not move hard cells in the TSCH schedule on its own. 2050 5.3.2. SlotFrames and Priorities 2052 A slotFrame is the base object that the PCE needs to manipulate to 2053 program a schedule into an LLN node. Elaboration on that concept can 2054 be found in section "SlotFrames and Priorities" of the 6TiSCH 2055 architecture [I-D.ietf-6tisch-architecture]. The architecture also 2056 details how the schedule is constructed and how transmission 2057 resources called cells can be allocated to particular transmissions 2058 so as to avoid collisions. 2060 5.3.3. Schedule Management by a PCE 2062 6TiSCH supports a mixed model of centralized routes and distributed 2063 routes. Centralized routes can for example be computed by a entity 2064 such as a PCE. Distributed routes are computed by RPL. 2066 Both methods may inject routes in the Routing Tables of the 6TiSCH 2067 routers. In either case, each route is associated with a 6TiSCH 2068 topology that can be a RPL Instance topology or a track. The 6TiSCH 2069 topology is indexed by a Instance ID, in a format that reuses the 2070 RPLInstanceID as defined in RPL [RFC6550]. 2072 Both RPL and PCE rely on shared sources such as policies to define 2073 Global and Local RPLInstanceIDs that can be used by either method. 2074 It is possible for centralized and distributed routing to share a 2075 same topology. Generally they will operate in different slotFrames, 2076 and centralized routes will be used for scheduled traffic and will 2077 have precedence over distributed routes in case of conflict between 2078 the slotFrames. 2080 Section "Schedule Management Mechanisms" of the 6TiSCH architecture 2081 describes 4 paradigms to manage the TSCH schedule of the LLN nodes: 2083 Static Scheduling, neighbor-to-neighbor Scheduling, remote monitoring 2084 and scheduling management, and Hop-by-hop scheduling. The Track 2085 operation for DetNet corresponds to a remote monitoring and 2086 scheduling management by a PCE. 2088 The 6top interface document [I-D.ietf-6tisch-6top-interface] 2089 specifies the generic data model that can be used to monitor and 2090 manage resources of the 6top sublayer. Abstract methods are 2091 suggested for use by a management entity in the device. The data 2092 model also enables remote control operations on the 6top sublayer. 2094 [I-D.ietf-6tisch-coap] defines an mapping of the 6top set of 2095 commands, which is described in [I-D.ietf-6tisch-6top-interface], to 2096 CoAP resources. This allows an entity to interact with the 6top 2097 layer of a node that is multiple hops away in a RESTful fashion. 2099 [I-D.ietf-6tisch-coap] also defines a basic set CoAP resources and 2100 associated RESTful access methods (GET/PUT/POST/DELETE). The payload 2101 (body) of the CoAP messages is encoded using the CBOR format. The 2102 PCE commands are expected to be issued directly as CoAP requests or 2103 to be mapped back and forth into CoAP by a gateway function at the 2104 edge of the 6TiSCH network. For instance, it is possible that a 2105 mapping entity on the backbone transforms a non-CoAP protocol such as 2106 PCEP into the RESTful interfaces that the 6TiSCH devices support. 2107 This architecture will be refined to comply with DetNet 2108 [I-D.finn-detnet-architecture] when the work is formalized. 2110 5.3.4. Track Forwarding 2112 By forwarding, this specification means the per-packet operation that 2113 allows to deliver a packet to a next hop or an upper layer in this 2114 node. Forwarding is based on pre-existing state that was installed 2115 as a result of the routing computation of a Track by a PCE. The 2116 6TiSCH architecture supports three different forwarding model, G-MPLS 2117 Track Forwarding (TF), 6LoWPAN Fragment Forwarding (FF) and IPv6 2118 Forwarding (6F) which is the classical IP operation. The DetNet case 2119 relates to the Track Forwarding operation under the control of a PCE. 2121 A Track is a unidirectional path between a source and a destination. 2122 In a Track cell, the normal operation of IEEE802.15.4 Automatic 2123 Repeat-reQuest (ARQ) usually happens, though the acknowledgment may 2124 be omitted in some cases, for instance if there is no scheduled cell 2125 for a retry. 2127 Track Forwarding is the simplest and fastest. A bundle of cells set 2128 to receive (RX-cells) is uniquely paired to a bundle of cells that 2129 are set to transmit (TX-cells), representing a layer-2 forwarding 2130 state that can be used regardless of the network layer protocol. 2132 This model can effectively be seen as a Generalized Multi-protocol 2133 Label Switching (G-MPLS) operation in that the information used to 2134 switch a frame is not an explicit label, but rather related to other 2135 properties of the way the packet was received, a particular cell in 2136 the case of 6TiSCH. As a result, as long as the TSCH MAC (and 2137 Layer-2 security) accepts a frame, that frame can be switched 2138 regardless of the protocol, whether this is an IPv6 packet, a 6LoWPAN 2139 fragment, or a frame from an alternate protocol such as WirelessHART 2140 or ISA100.11a. 2142 A data frame that is forwarded along a Track normally has a 2143 destination MAC address that is set to broadcast - or a multicast 2144 address depending on MAC support. This way, the MAC layer in the 2145 intermediate nodes accepts the incoming frame and 6top switches it 2146 without incurring a change in the MAC header. In the case of 2147 IEEE802.15.4, this means effectively broadcast, so that along the 2148 Track the short address for the destination of the frame is set to 2149 0xFFFF. 2151 A Track is thus formed end-to-end as a succession of paired bundles, 2152 a receive bundle from the previous hop and a transmit bundle to the 2153 next hop along the Track, and a cell in such a bundle belongs to at 2154 most one Track. For a given iteration of the device schedule, the 2155 effective channel of the cell is obtained by adding a pseudo-random 2156 number to the channelOffset of the cell, which results in a rotation 2157 of the frequency that used for transmission. The bundles may be 2158 computed so as to accommodate both variable rates and 2159 retransmissions, so they might not be fully used at a given iteration 2160 of the schedule. The 6TiSCH architecture provides additional means 2161 to avoid waste of cells as well as overflows in the transmit bundle, 2162 as follows: 2164 In one hand, a TX-cell that is not needed for the current iteration 2165 may be reused opportunistically on a per-hop basis for routed 2166 packets. When all of the frame that were received for a given Track 2167 are effectively transmitted, any available TX-cell for that Track can 2168 be reused for upper layer traffic for which the next-hop router 2169 matches the next hop along the Track. In that case, the cell that is 2170 being used is effectively a TX-cell from the Track, but the short 2171 address for the destination is that of the next-hop router. It 2172 results that a frame that is received in a RX-cell of a Track with a 2173 destination MAC address set to this node as opposed to broadcast must 2174 be extracted from the Track and delivered to the upper layer (a frame 2175 with an unrecognized MAC address is dropped at the lower MAC layer 2176 and thus is not received at the 6top sublayer). 2178 On the other hand, it might happen that there are not enough TX-cells 2179 in the transmit bundle to accommodate the Track traffic, for instance 2180 if more retransmissions are needed than provisioned. In that case, 2181 the frame can be placed for transmission in the bundle that is used 2182 for layer-3 traffic towards the next hop along the track as long as 2183 it can be routed by the upper layer, that is, typically, if the frame 2184 transports an IPv6 packet. The MAC address should be set to the 2185 next-hop MAC address to avoid confusion. It results that a frame 2186 that is received over a layer-3 bundle may be in fact associated to a 2187 Track. In a classical IP link such as an Ethernet, off-track traffic 2188 is typically in excess over reservation to be routed along the non- 2189 reserved path based on its QoS setting. But with 6TiSCH, since the 2190 use of the layer-3 bundle may be due to transmission failures, it 2191 makes sense for the receiver to recognize a frame that should be re- 2192 tracked, and to place it back on the appropriate bundle if possible. 2193 A frame should be re-tracked if the Per-Hop-Behavior group indicated 2194 in the Differentiated Services Field in the IPv6 header is set to 2195 Deterministic Forwarding, as discussed in Section 5.4.1. A frame is 2196 re-tracked by scheduling it for transmission over the transmit bundle 2197 associated to the Track, with the destination MAC address set to 2198 broadcast. 2200 There are 2 modes for a Track, transport mode and tunnel mode. 2202 5.3.4.1. Transport Mode 2204 In transport mode, the Protocol Data Unit (PDU) is associated with 2205 flow-dependant meta-data that refers uniquely to the Track, so the 2206 6top sublayer can place the frame in the appropriate cell without 2207 ambiguity. In the case of IPv6 traffic, this flow identification is 2208 transported in the Flow Label of the IPv6 header. Associated with 2209 the source IPv6 address, the Flow Label forms a globally unique 2210 identifier for that particular Track that is validated at egress 2211 before restoring the destination MAC address (DMAC) and punting to 2212 the upper layer. 2214 | ^ 2215 +--------------+ | | 2216 | IPv6 | | | 2217 +--------------+ | | 2218 | 6LoWPAN HC | | | 2219 +--------------+ ingress egress 2220 | 6top | sets +----+ +----+ restores 2221 +--------------+ dmac to | | | | dmac to 2222 | TSCH MAC | brdcst | | | | self 2223 +--------------+ | | | | | | 2224 | LLN PHY | +-------+ +--...-----+ +-------+ 2225 +--------------+ 2227 Track Forwarding, Transport Mode 2229 5.3.4.2. Tunnel Mode 2231 In tunnel mode, the frames originate from an arbitrary protocol over 2232 a compatible MAC that may or may not be synchronized with the 6TiSCH 2233 network. An example of this would be a router with a dual radio that 2234 is capable of receiving and sending WirelessHART or ISA100.11a frames 2235 with the second radio, by presenting itself as an access Point or a 2236 Backbone Router, respectively. 2238 In that mode, some entity (e.g. PCE) can coordinate with a 2239 WirelessHART Network Manager or an ISA100.11a System Manager to 2240 specify the flows that are to be transported transparently over the 2241 Track. 2243 +--------------+ 2244 | IPv6 | 2245 +--------------+ 2246 | 6LoWPAN HC | 2247 +--------------+ set restore 2248 | 6top | +dmac+ +dmac+ 2249 +--------------+ to|brdcst to|nexthop 2250 | TSCH MAC | | | | | 2251 +--------------+ | | | | 2252 | LLN PHY | +-------+ +--...-----+ +-------+ 2253 +--------------+ | ingress egress | 2254 | | 2255 +--------------+ | | 2256 | LLN PHY | | | 2257 +--------------+ | | 2258 | TSCH MAC | | | 2259 +--------------+ | dmac = | dmac = 2260 |ISA100/WiHART | | nexthop v nexthop 2261 +--------------+ 2263 Figure 7: Track Forwarding, Tunnel Mode 2265 In that case, the flow information that identifies the Track at the 2266 ingress 6TiSCH router is derived from the RX-cell. The dmac is set 2267 to this node but the flow information indicates that the frame must 2268 be tunneled over a particular Track so the frame is not passed to the 2269 upper layer. Instead, the dmac is forced to broadcast and the frame 2270 is passed to the 6top sublayer for switching. 2272 At the egress 6TiSCH router, the reverse operation occurs. Based on 2273 metadata associated to the Track, the frame is passed to the 2274 appropriate link layer with the destination MAC restored. 2276 5.3.4.3. Tunnel Metadata 2278 Metadata coming with the Track configuration is expected to provide 2279 the destination MAC address of the egress endpoint as well as the 2280 tunnel mode and specific data depending on the mode, for instance a 2281 service access point for frame delivery at egress. If the tunnel 2282 egress point does not have a MAC address that matches the 2283 configuration, the Track installation fails. 2285 In transport mode, if the final layer-3 destination is the tunnel 2286 termination, then it is possible that the IPv6 address of the 2287 destination is compressed at the 6LoWPAN sublayer based on the MAC 2288 address. It is thus mandatory at the ingress point to validate that 2289 the MAC address that was used at the 6LoWPAN sublayer for compression 2290 matches that of the tunnel egress point. For that reason, the node 2291 that injects a packet on a Track checks that the destination is 2292 effectively that of the tunnel egress point before it overwrites it 2293 to broadcast. The 6top sublayer at the tunnel egress point reverts 2294 that operation to the MAC address obtained from the tunnel metadata. 2296 5.4. Operations of Interest for DetNet and PCE 2298 In a classical system, the 6TiSCH device does not place the request 2299 for bandwidth between self and another device in the network. 2300 Rather, an Operation Control System invoked through an Human/Machine 2301 Interface (HMI) indicates the Traffic Specification, in particular in 2302 terms of latency and reliability, and the end nodes. With this, the 2303 PCE must compute a Track between the end nodes and provision the 2304 network with per-flow state that describes the per-hop operation for 2305 a given packet, the corresponding timeSlots, and the flow 2306 identification that enables to recognize when a certain packet 2307 belongs to a certain Track, sort out duplicates, etc... 2309 For a static configuration that serves a certain purpose for a long 2310 period of time, it is expected that a node will be provisioned in one 2311 shot with a full schedule, which incorporates the aggregation of its 2312 behavior for multiple Tracks. 6TiSCH expects that the programing of 2313 the schedule will be done over COAP as discussed in 6TiSCH Resource 2314 Management and Interaction using CoAP [I-D.ietf-6tisch-coap]. 2316 But an Hybrid mode may be required as well whereby a single Track is 2317 added, modified, or removed, for instance if it appears that a Track 2318 does not perform as expected for, say, PDR. For that case, the 2319 expectation is that a protocol that flows along a Track (to be), in a 2320 fashion similar to classical Traffic Engineering (TE) [CCAMP], may be 2321 used to update the state in the devices. 6TiSCH provides means for a 2322 device to negotiate a timeSlot with a neighbor, but in general that 2323 flow was not designed and no protocol was selected and it is expected 2324 that DetNet will determine the appropriate end-to-end protocols to be 2325 used in that case. 2327 Operational System and HMI 2329 -+-+-+-+-+-+-+ Northbound -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2331 PCE PCE PCE PCE 2333 -+-+-+-+-+-+-+ Southbound -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2335 --- 6TiSCH------6TiSCH------6TiSCH------6TiSCH-- 2336 6TiSCH / Device Device Device Device \ 2337 Device- - 6TiSCH 2338 \ 6TiSCH 6TiSCH 6TiSCH 6TiSCH / Device 2339 ----Device------Device------Device------Device-- 2341 Figure 8: Stream Management Entity 2343 5.4.1. Packet Marking and Handling 2345 Section "Packet Marking and Handling" of 2346 [I-D.ietf-6tisch-architecture] describes the packet tagging and 2347 marking that is expected in 6TiSCH networks. 2349 5.4.1.1. Tagging Packets for Flow Identification 2351 For packets that are routed by a PCE along a Track, the tuple formed 2352 by the IPv6 source address and a local RPLInstanceID is tagged in the 2353 packets to identify uniquely the Track and associated transmit bundle 2354 of timeSlots. 2356 It results that the tagging that is used for a DetNet flow outside 2357 the 6TiSCH LLN MUST be swapped into 6TiSCH formats and back as the 2358 packet enters and then leaves the 6TiSCH network. 2360 Note: The method and format used for encoding the RPLInstanceID at 2361 6lo is generalized to all 6TiSCH topological Instances, which 2362 includes Tracks. 2364 5.4.1.2. Replication, Retries and Elimination 2366 6TiSCH expects elimination and replication of packets along a complex 2367 Track, but has no position about how the sequence numbers would be 2368 tagged in the packet. 2370 As it goes, 6TiSCH expects that timeSlots corresponding to copies of 2371 a same packet along a Track are correlated by configuration, and does 2372 not need to process the sequence numbers. 2374 The semantics of the configuration MUST enable correlated timeSlots 2375 to be grouped for transmit (and respectively receive) with a 'OR' 2376 relations, and then a 'AND' relation MUST be configurable between 2377 groups. The semantics is that if the transmit (and respectively 2378 receive) operation succeeded in one timeSlot in a 'OR' group, then 2379 all the other timeSLots in the group are ignored. Now, if there are 2380 at least two groups, the 'AND' relation between the groups indicates 2381 that one operation must succeed in each of the groups. 2383 On the transmit side, timeSlots provisioned for retries along a same 2384 branch of a Track are placed a same 'OR' group. The 'OR' relation 2385 indicates that if a transmission is acknowledged, then further 2386 transmissions SHOULD NOT be attempted for timeSlots in that group. 2387 There are as many 'OR' groups as there are branches of the Track 2388 departing from this node. Different 'OR' groups are programmed for 2389 the purpose of replication, each group corresponding to one branch of 2390 the Track. The 'AND' relation between the groups indicates that 2391 transmission over any of branches MUST be attempted regardless of 2392 whether a transmission succeeded in another branch. It is also 2393 possible to place cells to different next-hop routers in a same 'OR' 2394 group. This allows to route along multi-path tracks, trying one 2395 next-hop and then another only if sending to the first fails. 2397 On the receive side, all timeSlots are programmed in a same 'OR' 2398 group. Retries of a same copy as well as converging branches for 2399 elimination are converged, meaning that the first successful 2400 reception is enough and that all the other timeSlots can be ignored. 2402 5.4.1.3. Differentiated Services Per-Hop-Behavior 2404 Additionally, an IP packet that is sent along a Track uses the 2405 Differentiated Services Per-Hop-Behavior Group called Deterministic 2406 Forwarding, as described in 2407 [I-D.svshah-tsvwg-deterministic-forwarding]. 2409 5.4.2. Topology and capabilities 2411 6TiSCH nodes are usually IoT devices, characterized by very limited 2412 amount of memory, just enough buffers to store one or a few IPv6 2413 packets, and limited bandwidth between peers. It results that a node 2414 will maintain only a small number of peering information, and will 2415 not be able to store many packets waiting to be forwarded. Peers can 2416 be identified through MAC or IPv6 addresses, but a Cryptographically 2417 Generated Address [RFC3972] (CGA) may also be used. 2419 Neighbors can be discovered over the radio using mechanism such as 2420 beacons, but, though the neighbor information is available in the 2421 6TiSCH interface data model, 6TiSCH does not describe a protocol to 2422 pro-actively push the neighborhood information to a PCE. This 2423 protocol should be described and should operate over CoAP. The 2424 protocol should be able to carry multiple metrics, in particular the 2425 same metrics as used for RPL operations [RFC6551] 2427 The energy that the device consumes in sleep, transmit and receive 2428 modes can be evaluated and reported. So can the amount of energy 2429 that is stored in the device and the power that it can be scavenged 2430 from the environment. The PCE SHOULD be able to compute Tracks that 2431 will implement policies on how the energy is consumed, for instance 2432 balance between nodes, ensure that the spent energy does not exceeded 2433 the scavenged energy over a period of time, etc... 2435 5.5. Security Considerations 2437 On top of the classical protection of control signaling that can be 2438 expected to support DetNet, it must be noted that 6TiSCH networks 2439 operate on limited resources that can be depleted rapidly if an 2440 attacker manages to operate a DoS attack on the system, for instance 2441 by placing a rogue device in the network, or by obtaining management 2442 control and to setup extra paths. 2444 6. Cellular Radio Use Cases 2446 6.1. Use Case Description 2448 This use case describes the application of deterministic networking 2449 in the context of cellular telecom transport networks. Important 2450 elements include time synchronization, clock distribution, and ways 2451 of establishing time-sensitive streams for both Layer-2 and Layer-3 2452 user plane traffic. 2454 6.1.1. Network Architecture 2456 Figure 9 illustrates a typical 3GPP-defined cellular network 2457 architecture, which includes "Fronthaul" and "Midhaul" network 2458 segments. The "Fronthaul" is the network connecting base stations 2459 (baseband processing units) to the remote radio heads (antennas). 2460 The "Midhaul" is the network inter-connecting base stations (or small 2461 cell sites). 2463 In Figure 9 "eNB" ("E-UTRAN Node B") is the hardware that is 2464 connected to the mobile phone network which communicates directly 2465 with mobile handsets ([TS36300]). 2467 Y (remote radio heads (antennas)) 2468 \ 2469 Y__ \.--. .--. +------+ 2470 \_( `. +---+ _(Back`. | 3GPP | 2471 Y------( Front )----|eNB|----( Haul )----| core | 2472 ( ` .Haul ) +---+ ( ` . ) ) | netw | 2473 /`--(___.-' \ `--(___.-' +------+ 2474 Y_/ / \.--. \ 2475 Y_/ _( Mid`. \ 2476 ( Haul ) \ 2477 ( ` . ) ) \ 2478 `--(___.-'\_____+---+ (small cell sites) 2479 \ |SCe|__Y 2480 +---+ +---+ 2481 Y__|eNB|__Y 2482 +---+ 2483 Y_/ \_Y ("local" radios) 2485 Figure 9: Generic 3GPP-based Cellular Network Architecture 2487 The available processing time for Fronthaul networking overhead is 2488 limited to the available time after the baseband processing of the 2489 radio frame has completed. For example in Long Term Evolution (LTE) 2490 radio, processing of a radio frame is allocated 3ms, but typically 2491 the processing completes much earlier (<400us) allowing the remaining 2492 time to be used by the Fronthaul network. This ultimately determines 2493 the distance the remote radio heads can be located from the base 2494 stations (200us equals roughly 40 km of optical fiber-based 2495 transport, thus round trip time is 2*200us = 400us). 2497 The remainder of the "maximum delay budget" is consumed by all nodes 2498 and buffering between the remote radio head and the baseband 2499 processing, plus the distance-incurred delay. 2501 The baseband processing time and the available "delay budget" for the 2502 fronthaul is likely to change in the forthcoming "5G" due to reduced 2503 radio round trip times and other architectural and service 2504 requirements [NGMN]. 2506 6.1.2. Time Synchronization Requirements 2508 Fronthaul time synchronization requirements are given by [TS25104], 2509 [TS36104], [TS36211], and [TS36133]. These can be summarized for the 2510 current 3GPP LTE-based networks as: 2512 Delay Accuracy: 2513 +-8ns (i.e. +-1/32 Tc, where Tc is the UMTS Chip time of 1/3.84 2514 MHz) resulting in a round trip accuracy of +-16ns. The value is 2515 this low to meet the 3GPP Timing Alignment Error (TAE) measurement 2516 requirements. 2518 Packet Delay Variation: 2519 Packet Delay Variation (PDV aka Jitter aka Timing Alignment Error) 2520 is problematic to Fronthaul networks and must be minimized. If 2521 the transport network cannot guarantee low enough PDV then 2522 additional buffering has to be introduced at the edges of the 2523 network to buffer out the jitter. Buffering is not desirable as 2524 it reduces the total available delay budget. 2526 * For multiple input multiple output (MIMO) or TX diversity 2527 transmissions, at each carrier frequency, TAE shall not exceed 2528 65 ns (i.e. 1/4 Tc). 2530 * For intra-band contiguous carrier aggregation, with or without 2531 MIMO or TX diversity, TAE shall not exceed 130 ns (i.e. 1/2 2532 Tc). 2534 * For intra-band non-contiguous carrier aggregation, with or 2535 without MIMO or TX diversity, TAE shall not exceed 260 ns (i.e. 2536 one Tc). 2538 * For inter-band carrier aggregation, with or without MIMO or TX 2539 diversity, TAE shall not exceed 260 ns. 2541 Transport link contribution to radio frequency error: 2542 +-2 PPB. This value is considered to be "available" for the 2543 Fronthaul link out of the total 50 PPB budget reserved for the 2544 radio interface. Note: the reason that the transport link 2545 contributes to radio frequency error is as follows. The current 2546 way of doing Fronthaul is from the radio unit to remote radio head 2547 directly. The remote radio head is essentially a passive device 2548 (without buffering etc.) The transport drives the antenna 2549 directly by feeding it with samples and everything the transport 2550 adds will be introduced to radio as-is. So if the transport 2551 causes additional frequence error that shows immediately on the 2552 radio as well. 2554 The above listed time synchronization requirements are difficult to 2555 meet with point-to-point connected networks, and more difficult when 2556 the network includes multiple hops. It is expected that networks 2557 must include buffering at the ends of the connections as imposed by 2558 the jitter requirements, since trying to meet the jitter requirements 2559 in every intermediate node is likely to be too costly. However, 2560 every measure to reduce jitter and delay on the path makes it easier 2561 to meet the end-to-end requirements. 2563 In order to meet the timing requirements both senders and receivers 2564 must remain time synchronized, demanding very accurate clock 2565 distribution, for example support for IEEE 1588 transparent clocks in 2566 every intermediate node. 2568 In cellular networks from the LTE radio era onward, phase 2569 synchronization is needed in addition to frequency synchronization 2570 ([TS36300], [TS23401]). 2572 6.1.3. Time-Sensitive Stream Requirements 2574 In addition to the time synchronization requirements listed in 2575 Section Section 6.1.2 the Fronthaul networks assume practically 2576 error-free transport. The maximum bit error rate (BER) has been 2577 defined to be 10^-12. When packetized that would imply a packet 2578 error rate (PER) of 2.4*10^-9 (assuming ~300 bytes packets). 2579 Retransmitting lost packets and/or using forward error correction 2580 (FEC) to circumvent bit errors is practically impossible due to the 2581 additional delay incurred. Using redundant streams for better 2582 guarantees for delivery is also practically impossible in many cases 2583 due to high bandwidth requirements of Fronthaul networks. For 2584 instance, current uncompressed CPRI bandwidth expansion ratio is 2585 roughly 20:1 compared to the IP layer user payload it carries. 2586 Protection switching is also a candidate but current technologies for 2587 the path switch are too slow. We do not currently know of a better 2588 solution for this issue. 2590 Fronthaul links are assumed to be symmetric, and all Fronthaul 2591 streams (i.e. those carrying radio data) have equal priority and 2592 cannot delay or pre-empt each other. This implies that the network 2593 must guarantee that each time-sensitive flow meets their schedule. 2595 6.1.4. Security Considerations 2597 Establishing time-sensitive streams in the network entails reserving 2598 networking resources for long periods of time. It is important that 2599 these reservation requests be authenticated to prevent malicious 2600 reservation attempts from hostile nodes (or accidental 2601 misconfiguration). This is particularly important in the case where 2602 the reservation requests span administrative domains. Furthermore, 2603 the reservation information itself should be digitally signed to 2604 reduce the risk of a legitimate node pushing a stale or hostile 2605 configuration into another networking node. 2607 6.2. Cellular Radio Networks Today 2609 Today's Fronthaul networks typically consist of: 2611 o Dedicated point-to-point fiber connection is common 2613 o Proprietary protocols and framings 2615 o Custom equipment and no real networking 2617 Today's Midhaul and Backhaul networks typically consist of: 2619 o Mostly normal IP networks, MPLS-TP, etc. 2621 o Clock distribution and sync using 1588 and SyncE 2623 Telecommunication networks in the cellular domain are already heading 2624 towards transport networks where precise time synchronization support 2625 is one of the basic building blocks. While the transport networks 2626 themselves have practically transitioned to all-IP packet based 2627 networks to meet the bandwidth and cost requirements, highly accurate 2628 clock distribution has become a challenge. 2630 Transport networks in the cellular domain are typically based on Time 2631 Division Multiplexing (TDM-based) and provide frequency 2632 synchronization capabilities as a part of the transport media. 2633 Alternatively other technologies such as Global Positioning System 2634 (GPS) or Synchronous Ethernet (SyncE) are used [SyncE]. 2636 Both Ethernet and IP/MPLS [RFC3031] (and PseudoWires (PWE) [RFC3985] 2637 for legacy transport support) have become popular tools to build and 2638 manage new all-IP Radio Access Networks (RAN) 2639 [I-D.kh-spring-ip-ran-use-case]. Although various timing and 2640 synchronization optimizations have already been proposed and 2641 implemented including 1588 PTP enhancements 2642 [I-D.ietf-tictoc-1588overmpls][I-D.mirsky-mpls-residence-time], these 2643 solution are not necessarily sufficient for the forthcoming RAN 2644 architectures or guarantee the higher time-synchronization 2645 requirements [CPRI]. There are also existing solutions for the TDM 2646 over IP [RFC5087] [RFC4553] or Ethernet transports [RFC5086]. 2648 6.3. Cellular Radio Networks Future 2650 We would like to see the following in future Cellular Radio networks: 2652 o Unified standards-based transport protocols and standard 2653 networking equipment that can make use of underlying deterministic 2654 link-layer services 2656 o Unified and standards-based network management systems and 2657 protocols in all parts of the network (including Fronthaul) 2659 New radio access network deployment models and architectures may 2660 require time sensitive networking services with strict requirements 2661 on other parts of the network that previously were not considered to 2662 be packetized at all. The time and synchronization support are 2663 already topical for Backhaul and Midhaul packet networks [MEF], and 2664 becoming a real issue for Fronthaul networks. Specifically in the 2665 Fronthaul networks the timing and synchronization requirements can be 2666 extreme for packet based technologies, for example, on the order of 2667 sub +-20 ns packet delay variation (PDV) and frequency accuracy of 2668 +0.002 PPM [Fronthaul]. 2670 The actual transport protocols and/or solutions to establish required 2671 transport "circuits" (pinned-down paths) for Fronthaul traffic are 2672 still undefined. Those are likely to include (but are not limited 2673 to) solutions directly over Ethernet, over IP, and MPLS/PseudoWire 2674 transport. 2676 Even the current time-sensitive networking features may not be 2677 sufficient for Fronthaul traffic. Therefore, having specific 2678 profiles that take the requirements of Fronthaul into account is 2679 desirable [IEEE8021CM]. 2681 The really interesting and important existing work for time sensitive 2682 networking has been done for Ethernet [TSNTG], which specifies the 2683 use of IEEE 1588 time precision protocol (PTP) [IEEE1588] in the 2684 context of IEEE 802.1D and IEEE 802.1Q. While IEEE 802.1AS 2685 [IEEE8021AS] specifies a Layer-2 time synchronizing service other 2686 specification, such as IEEE 1722 [IEEE1722] specify Ethernet-based 2687 Layer-2 transport for time-sensitive streams. New promising work 2688 seeks to enable the transport of time-sensitive fronthaul streams in 2689 Ethernet bridged networks [IEEE8021CM]. Similarly to IEEE 1722 there 2690 is an ongoing standardization effort to define Layer-2 transport 2691 encapsulation format for transporting radio over Ethernet (RoE) in 2692 IEEE 1904.3 Task Force [IEEE19043]. 2694 All-IP RANs and various "haul" networks would benefit from time 2695 synchronization and time-sensitive transport services. Although 2696 Ethernet appears to be the unifying technology for the transport 2697 there is still a disconnect providing Layer-3 services. The protocol 2698 stack typically has a number of layers below the Ethernet Layer-2 2699 that shows up to the Layer-3 IP transport. It is not uncommon that 2700 on top of the lowest layer (optical) transport there is the first 2701 layer of Ethernet followed one or more layers of MPLS, PseudoWires 2702 and/or other tunneling protocols finally carrying the Ethernet layer 2703 visible to the user plane IP traffic. While there are existing 2704 technologies, especially in MPLS/PWE space, to establish circuits 2705 through the routed and switched networks, there is a lack of 2706 signaling the time synchronization and time-sensitive stream 2707 requirements/reservations for Layer-3 flows in a way that the entire 2708 transport stack is addressed and the Ethernet layers that needs to be 2709 configured are addressed. 2711 Furthermore, not all "user plane" traffic will be IP. Therefore, the 2712 same solution also must address the use cases where the user plane 2713 traffic is again another layer or Ethernet frames. There is existing 2714 work describing the problem statement 2715 [I-D.finn-detnet-problem-statement] and the architecture 2716 [I-D.finn-detnet-architecture] for deterministic networking (DetNet) 2717 that targets solutions for time-sensitive (IP/transport) streams with 2718 deterministic properties over Ethernet-based switched networks. 2720 6.4. Cellular Radio Networks Asks 2722 A standard for data plane transport specification which is: 2724 o Unified among all *hauls 2726 o Deployed in a highly deterministic network environment 2728 A standard for data flow information models that are: 2730 o Aware of the time sensitivity and constraints of the target 2731 networking environment 2733 o Aware of underlying deterministic networking services (e.g. on the 2734 Ethernet layer) 2736 Mapping the Fronthaul requirements to IETF DetNet 2737 [I-D.finn-detnet-architecture] Section 3 "Providing the DetNet 2738 Quality of Service", the relevant features are: 2740 o Zero congestion loss. 2742 o Pinned-down paths. 2744 7. Cellular Coordinated Multipoint Processing (CoMP) 2746 7.1. Use Case Description 2748 In cellular wireless communication systems, Inter-Site Coordinated 2749 Multipoint Processing (CoMP, see [CoMP]) is a technique implemented 2750 within a cell site which improves system efficiency and user quality 2751 experience by significantly improving throughput in the cell-edge 2752 region (i.e. at the edges of that cell site's radio coverage area). 2753 CoMP techniques depend on deterministic high-reliability 2754 communication between cell sites, however such connections today are 2755 IP-based which in current mobile networks can not meet the QoS 2756 requirements, so CoMP is an emerging technology which can benefit 2757 from DetNet. 2759 Here we consider the JT (Joint Transmit) application for CoMP, which 2760 provides the highest performance gain (compared to other 2761 applications). 2763 7.1.1. CoMP Architecture 2765 +--------------------------+ 2766 | CoMP | 2767 +--+--------------------+--+ 2768 | | 2769 +----------+ +------------+ 2770 | Uplink | | Downlink | 2771 +-----+----+ +--------+---+ 2772 | | 2773 ------------------- ----------------------- 2774 | | | | | | 2775 +---------+ +----+ +-----+ +------------+ +-----+ +-----+ 2776 | Joint | | CS | | DPS | | Joint | | CS/ | | DPS | 2777 |Reception| | | | | |Transmission| | CB | | | 2778 +---------+ +----+ +-----+ +------------+ +-----+ +-----+ 2779 | | 2780 |----------- |------------- 2781 | | | | 2782 +------------+ +---------+ +----------+ +------------+ 2783 | Joint | | Soft | | Coherent | | Non- | 2784 |Equalization| |Combining| | JT | | Coherent JT| 2785 +------------+ +---------+ +----------+ +------------+ 2787 Figure 10: Framework of CoMP Technology 2789 As shown in Figure 10, CoMP reception and transmission is a framework 2790 in which multiple geographically distributed antenna nodes cooperate 2791 to improve the performance of the users served in the common 2792 cooperation area. The design principal of CoMP is to extend the 2793 current single-cell to multi-UE (User Equipment) transmission to a 2794 multi-cell- to-multi-UEs transmission by base station cooperation. 2796 7.1.2. Delay Sensitivity in CoMP 2798 In contrast to the single-cell scenario, CoMP has delay-sensitive 2799 performance parameters, which are "backhaul latency" and "CSI 2800 (Channel State Information) reporting and accuracy". The essential 2801 feature of CoMP is signaling between eNBs, so the backhaul latency is 2802 the dominating limitation of the CoMP performance. Generally, JT can 2803 benefit from coordinated scheduling (either distributed or 2804 centralized) of different cells if the signaling delay between eNBs 2805 is within 4-10ms. This delay requirement is both rigid and absolute 2806 because any uncertainty in delay will degrade the performance 2807 significantly. 2809 7.2. CoMP Today 2811 Due to the strict sensitivity to latency and synchronization, CoMP 2812 between eNB has not been deployed yet. This is because the current 2813 interface path between eNBs cannot meet the delay bound because it is 2814 usually IP-based and passing through multiple network hops (this 2815 interface is called "X2" or "eX2" for "enhanced X2"). Today lack of 2816 absolute delay guarantee on X2/eX2 traffic is the main obstacle to JT 2817 and multi-eNB coordination. 2819 There is still lack of Layer-3 (IP) transport protocol and signaling 2820 that is capable of low latency services; current techniques such as 2821 MPLS and PWE focus on establishing circuits using pre-routed paths 2822 but there is no such signaling for reservation of time-sensitive 2823 stream. 2825 7.3. CoMP Future 2827 7.3.1. Mobile Industry Overall Goals 2829 [METIS] documents the fundamental challenges as well as overall 2830 technical goals of the 5G mobile and wireless system as the starting 2831 point. These future systems should support (at similar cost and 2832 energy consumption levels as today's system): 2834 o 1000 times higher mobile data volume per area 2836 o 10 times to 100 times higher typical user data rate 2838 o 10 times to 100 times higher number of connected devices 2840 o 10 times longer battery life for low power devices 2842 o 5 times reduced End-to-End (E2E) latency 2843 The current LTE networking system has E2E latency less than 20ms 2844 [LTE-Latency] which leads to around 5ms E2E latency for 5G networks. 2845 To fulfill these latency demands at similar cost will be challenging 2846 because as the system also requires 100x bandwidth and 100x connected 2847 devices, simply adding redundant bandwidth provisioning can no longer 2848 be an efficient solution. 2850 In addition to bandwidth provisioning, reserved critical flows should 2851 not be affected by other flows no matter the pressure of the network. 2852 Deterministic networking techniques in both layer-2 and layer-3 using 2853 IETF protocol solutions can be promising to serve these scenarios. 2855 7.3.2. CoMP Infrastructure Goals 2857 Inter-site CoMP is one of the key requirements for 5G and is also a 2858 near-term goal for the current 4.5G network architecture. Assuming 2859 network architecture remains unchanged (i.e. no Fronthaul network and 2860 data flow between eNB is via X2/eX2) we would like to see the 2861 following in the near future: 2863 o Unified protocols and delay-guaranteed forwarding network 2864 equipment that is capable of delivering deterministic latency 2865 services. 2867 o Unified management and protocols which take delay and timing into 2868 account. 2870 o Unified deterministic latency data model and signaling for 2871 resource reservation. 2873 7.4. CoMP Asks 2875 To fully utilize the power of CoMP, it requires: 2877 o Very tight absolute delay bound (100-500us) within 7-10 hops. 2879 o Standardized data plane with highly deterministic networking 2880 capability. 2882 o Standardized control plane to unify backhaul network elements with 2883 time-sensitive stream reservation signaling. 2885 In addition, a standardized deterministic latency data flow model 2886 that includes: 2888 o Network-aware constraints on the networking environment 2889 o Time-aware description of flow characteristics and network 2890 resources, which may not need to be bandwidth based 2892 o Application-aware description of deterministic latency services. 2894 8. Industrial M2M 2896 8.1. Use Case Description 2898 Industrial Automation in general refers to automation of 2899 manufacturing, quality control and material processing. In this 2900 "machine to machine" (M2M) use case we consider machine units in a 2901 plant floor which periodically exchange data with upstream or 2902 downstream machine modules and/or a supervisory controller within a 2903 local area network. 2905 The actors of M2M communication are Programmable Logic Controllers 2906 (PLCs). Communication between PLCs and between PLCs and the 2907 supervisory PLC (S-PLC) is achieved via critical control/data streams 2908 Figure 11. 2910 S (Sensor) 2911 \ +-----+ 2912 PLC__ \.--. .--. ---| MES | 2913 \_( `. _( `./ +-----+ 2914 A------( Local )-------------( L2 ) 2915 ( Net ) ( Net ) +-------+ 2916 /`--(___.-' `--(___.-' ----| S-PLC | 2917 S_/ / PLC .--. / +-------+ 2918 A_/ \_( `. 2919 (Actuator) ( Local ) 2920 ( Net ) 2921 /`--(___.-'\ 2922 / \ A 2923 S A 2925 Figure 11: Current Generic Industrial M2M Network Architecture 2927 This use case focuses on PLC-related communications; communication to 2928 Manufacturing-Execution-Systems (MESs) are not addressed. 2930 This use case covers only critical control/data streams; non-critical 2931 traffic between industrial automation applications (such as 2932 communication of state, configuration, set-up, and database 2933 communication) are adequately served by currently available 2934 prioritizing techniques. Such traffic can use up to 80% of the total 2935 bandwidth required. There is also a subset of non-time-critical 2936 traffic that must be reliable even though it is not time sensitive. 2938 In this use case the primary need for deterministic networking is to 2939 provide end-to-end delivery of M2M messages within specific timing 2940 constraints, for example in closed loop automation control. Today 2941 this level of determinism is provided by proprietary networking 2942 technologies. In addition, standard networking technologies are used 2943 to connect the local network to remote industrial automation sites, 2944 e.g. over an enterprise or metro network which also carries other 2945 types of traffic. Therefore, flows that should be forwarded with 2946 deterministic guarantees need to be sustained regardless of the 2947 amount of other flows in those networks. 2949 8.2. Industrial M2M Communication Today 2951 Today, proprietary networks fulfill the needed timing and 2952 availability for M2M networks. 2954 The network topologies used today by industrial automation are 2955 similar to those used by telecom networks: Daisy Chain, Ring, Hub and 2956 Spoke, and Comb (a subset of Daisy Chain). 2958 PLC-related control/data streams are transmitted periodically and 2959 carry either a pre-configured payload or a payload configured during 2960 runtime. 2962 Some industrial applications require time synchronization at the end 2963 nodes. For such time-coordinated PLCs, accuracy of 1 microsecond is 2964 required. Even in the case of "non-time-coordinated" PLCs time sync 2965 may be needed e.g. for timestamping of sensor data. 2967 Industrial network scenarios require advanced security solutions. 2968 Many of the current industrial production networks are physically 2969 separated. Preventing critical flows from be leaked outside a domain 2970 is handled today by filtering policies that are typically enforced in 2971 firewalls. 2973 8.2.1. Transport Parameters 2975 The Cycle Time defines the frequency of message(s) between industrial 2976 actors. The Cycle Time is application dependent, in the range of 1ms 2977 - 100ms for critical control/data streams. 2979 Because industrial applications assume deterministic transport for 2980 critical Control-Data-Stream parameters (instead of defining latency 2981 and delay variation parameters) it is sufficient to fulfill the upper 2982 bound of latency (maximum latency). The underlying networking 2983 infrastructure must ensure a maximum end-to-end delivery time of 2984 messages in the range of 100 microseconds to 50 milliseconds 2985 depending on the control loop application. 2987 The bandwidth requirements of control/data streams are usually 2988 calculated directly from the bytes-per-cycle parameter of the control 2989 loop. For PLC-to-PLC communication one can expect 2 - 32 streams 2990 with packet size in the range of 100 - 700 bytes. For S-PLC to PLCs 2991 the number of streams is higher - up to 256 streams. Usually no more 2992 than 20% of available bandwidth is used for critical control/data 2993 streams. In today's networks 1Gbps links are commonly used. 2995 Most PLC control loops are rather tolerant of packet loss, however 2996 critical control/data streams accept no more than 1 packet loss per 2997 consecutive communication cycle (i.e. if a packet gets lost in cycle 2998 "n", then the next cycle ("n+1") must be lossless). After two or 2999 more consecutive packet losses the network may be considered to be 3000 "down" by the Application. 3002 As network downtime may impact the whole production system the 3003 required network availability is rather high (99,999%). 3005 Based on the above parameters we expect that some form of redundancy 3006 will be required for M2M communications, however any individual 3007 solution depends on several parameters including cycle time, delivery 3008 time, etc. 3010 8.2.2. Stream Creation and Destruction 3012 In an industrial environment, critical control/data streams are 3013 created rather infrequently, on the order of ~10 times per day / week 3014 / month. Most of these critical control/data streams get created at 3015 machine startup, however flexibility is also needed during runtime, 3016 for example when adding or removing a machine. Going forward as 3017 production systems become more flexible, we expect a significant 3018 increase in the rate at which streams are created, changed and 3019 destroyed. 3021 8.3. Industrial M2M Future 3023 We would like to see the various proprietary networks replaced with a 3024 converged IP-standards-based network with deterministic properties 3025 that can satisfy the timing, security and reliability constraints 3026 described above. 3028 8.4. Industrial M2M Asks 3030 o Converged IP-based network 3032 o Deterministic behavior (bounded latency and jitter ) 3034 o High availability (presumably through redundancy) (99.999 %) 3036 o Low message delivery time (100us - 50ms) 3038 o Low packet loss (burstless, 0.1-1 %) 3040 o Precise time synchronization accuracy (1us) 3042 o Security (e.g. prevent critical flows from being leaked between 3043 physically separated networks) 3045 9. Internet-based Applications 3047 9.1. Use Case Description 3049 There are many applications that communicate across the open Internet 3050 that could benefit from guaranteed delivery and bounded latency. The 3051 following are some representative examples. 3053 9.1.1. Media Content Delivery 3055 Media content delivery continues to be an important use of the 3056 Internet, yet users often experience poor quality audio and video due 3057 to the delay and jitter inherent in today's Internet. 3059 9.1.2. Online Gaming 3061 Online gaming is a significant part of the gaming market, however 3062 latency can degrade the end user experience. For example "First 3063 Person Shooter" (FPS) games are highly delay-sensitive. 3065 9.1.3. Virtual Reality 3067 Virtual reality (VR) has many commercial applications including real 3068 estate presentations, remote medical procedures, and so on. Low 3069 latency is critical to interacting with the virtual world because 3070 perceptual delays can cause motion sickness. 3072 9.2. Internet-Based Applications Today 3074 Internet service today is by definition "best effort", with no 3075 guarantees on delivery or bandwidth. 3077 9.3. Internet-Based Applications Future 3079 We imagine an Internet from which we will be able to play a video 3080 without glitches and play games without lag. 3082 For online gaming, the maximum round-trip delay can be 100ms and 3083 stricter for FPS gaming which can be 10-50ms. Transport delay is the 3084 dominate part with a 5-20ms budget. 3086 For VR, 1-10ms maximum delay is needed and total network budget is 3087 1-5ms if doing remote VR. 3089 Flow identification can be used for gaming and VR, i.e. it can 3090 recognize a critical flow and provide appropriate latency bounds. 3092 9.4. Internet-Based Applications Asks 3094 o Unified control and management protocols to handle time-critical 3095 data flow 3097 o Application-aware flow filtering mechanism to recognize the timing 3098 critical flow without doing 5-tuple matching 3100 o Unified control plane to provide low latency service on Layer-3 3101 without changing the data plane 3103 o OAM system and protocols which can help to provide E2E-delay 3104 sensitive service provisioning 3106 10. Use Case Common Elements 3108 Looking at the use cases collectively, the following common desires 3109 for the DetNet-based networks of the future emerge: 3111 o Open standards-based network (replace various proprietary 3112 networks, reduce cost, create multi-vendor market) 3114 o Centrally administered (though such administration may be 3115 distributed for scale and resiliency) 3117 o Integrates L2 (bridged) and L3 (routed) environments (independent 3118 of the Link layer, e.g. can be used with Ethernet, 6TiSCH, etc.) 3120 o Carries both deterministic and best-effort traffic (guaranteed 3121 end-to-end delivery of deterministic flows, deterministic flows 3122 isolated from each other and from best-effort traffic congestion, 3123 unused deterministic BW available to best-effort traffic) 3125 o Ability to add or remove systems from the network with minimal, 3126 bounded service interruption (applications include replacement of 3127 failed devices as well as plug and play) 3129 o Uses standardized data flow information models capable of 3130 expressing deterministic properties (models express device 3131 capabilities, flow properties. Protocols for pushing models from 3132 controller to devices, devices to controller) 3134 o Scalable size (long distances (many km) and short distances 3135 (within a single machine), many hops (radio repeaters, microwave 3136 links, fiber links...) and short hops (single machine)) 3138 o Scalable timing parameters and accuracy (bounded latency, 3139 guaranteed worst case maximum, minimum. Low latency, e.g. control 3140 loops may be less than 1ms, but larger for wide area networks) 3142 o High availability (99.9999 percent up time requested, but may be 3143 up to twelve 9s) 3145 o Reliability, redundancy (lives at stake) 3147 o Security (from failures, attackers, misbehaving devices - 3148 sensitive to both packet content and arrival time) 3150 11. Acknowledgments 3152 11.1. Pro Audio 3154 This section was derived from draft-gunther-detnet-proaudio-req-01. 3156 The editors would like to acknowledge the help of the following 3157 individuals and the companies they represent: 3159 Jeff Koftinoff, Meyer Sound 3161 Jouni Korhonen, Associate Technical Director, Broadcom 3163 Pascal Thubert, CTAO, Cisco 3165 Kieran Tyrrell, Sienda New Media Technologies GmbH 3167 11.2. Utility Telecom 3169 This section was derived from draft-wetterwald-detnet-utilities-reqs- 3170 02. 3172 Faramarz Maghsoodlou, Ph. D. IoT Connected Industries and Energy 3173 Practice Cisco 3175 Pascal Thubert, CTAO Cisco 3177 11.3. Building Automation Systems 3179 This section was derived from draft-bas-usecase-detnet-00. 3181 11.4. Wireless for Industrial 3183 This section was derived from draft-thubert-6tisch-4detnet-01. 3185 This specification derives from the 6TiSCH architecture, which is the 3186 result of multiple interactions, in particular during the 6TiSCH 3187 (bi)Weekly Interim call, relayed through the 6TiSCH mailing list at 3188 the IETF. 3190 The authors wish to thank: Kris Pister, Thomas Watteyne, Xavier 3191 Vilajosana, Qin Wang, Tom Phinney, Robert Assimiti, Michael 3192 Richardson, Zhuo Chen, Malisa Vucinic, Alfredo Grieco, Martin Turon, 3193 Dominique Barthel, Elvis Vogli, Guillaume Gaillard, Herman Storey, 3194 Maria Rita Palattella, Nicola Accettura, Patrick Wetterwald, Pouria 3195 Zand, Raghuram Sudhaakar, and Shitanshu Shah for their participation 3196 and various contributions. 3198 11.5. Cellular Radio 3200 This section was derived from draft-korhonen-detnet-telreq-00. 3202 11.6. Industrial M2M 3204 The authors would like to thank Feng Chen and Marcel Kiessling for 3205 their comments and suggestions. 3207 11.7. Other 3209 This section was derived from draft-zha-detnet-use-case-00. 3211 This document has benefited from reviews, suggestions, comments and 3212 proposed text provided by the following members, listed in 3213 alphabetical order: Jing Huang, Junru Lin, Lehong Niu and Oilver 3214 Huang. 3216 12. Informative References 3218 [ACE] IETF, "Authentication and Authorization for Constrained 3219 Environments", . 3222 [bacnetip] 3223 ASHRAE, "Annex J to ANSI/ASHRAE 135-1995 - BACnet/IP", 3224 January 1999. 3226 [CCAMP] IETF, "Common Control and Measurement Plane", 3227 . 3229 [CoMP] NGMN Alliance, "RAN EVOLUTION PROJECT COMP EVALUATION AND 3230 ENHANCEMENT", NGMN Alliance NGMN_RANEV_D3_CoMP_Evaluation_ 3231 and_Enhancement_v2.0, March 2015, 3232 . 3235 [CONTENT_PROTECTION] 3236 Olsen, D., "1722a Content Protection", 2012, 3237 . 3240 [CPRI] CPRI Cooperation, "Common Public Radio Interface (CPRI); 3241 Interface Specification", CPRI Specification V6.1, July 3242 2014, . 3245 [DCI] Digital Cinema Initiatives, LLC, "DCI Specification, 3246 Version 1.2", 2012, . 3248 [DICE] IETF, "DTLS In Constrained Environments", 3249 . 3251 [EA12] Evans, P. and M. 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Wang, 3299 "Terminology in IPv6 over the TSCH mode of IEEE 3300 802.15.4e", draft-ietf-6tisch-terminology-06 (work in 3301 progress), November 2015. 3303 [I-D.ietf-ipv6-multilink-subnets] 3304 Thaler, D. and C. Huitema, "Multi-link Subnet Support in 3305 IPv6", draft-ietf-ipv6-multilink-subnets-00 (work in 3306 progress), July 2002. 3308 [I-D.ietf-roll-rpl-industrial-applicability] 3309 Phinney, T., Thubert, P., and R. Assimiti, "RPL 3310 applicability in industrial networks", draft-ietf-roll- 3311 rpl-industrial-applicability-02 (work in progress), 3312 October 2013. 3314 [I-D.ietf-tictoc-1588overmpls] 3315 Davari, S., Oren, A., Bhatia, M., Roberts, P., and L. 3316 Montini, "Transporting Timing messages over MPLS 3317 Networks", draft-ietf-tictoc-1588overmpls-07 (work in 3318 progress), October 2015. 3320 [I-D.kh-spring-ip-ran-use-case] 3321 Khasnabish, B., hu, f., and L. Contreras, "Segment Routing 3322 in IP RAN use case", draft-kh-spring-ip-ran-use-case-02 3323 (work in progress), November 2014. 3325 [I-D.mirsky-mpls-residence-time] 3326 Mirsky, G., Ruffini, S., Gray, E., Drake, J., Bryant, S., 3327 and S. Vainshtein, "Residence Time Measurement in MPLS 3328 network", draft-mirsky-mpls-residence-time-07 (work in 3329 progress), July 2015. 3331 [I-D.svshah-tsvwg-deterministic-forwarding] 3332 Shah, S. and P. Thubert, "Deterministic Forwarding PHB", 3333 draft-svshah-tsvwg-deterministic-forwarding-04 (work in 3334 progress), August 2015. 3336 [I-D.thubert-6lowpan-backbone-router] 3337 Thubert, P., "6LoWPAN Backbone Router", draft-thubert- 3338 6lowpan-backbone-router-03 (work in progress), February 3339 2013. 3341 [I-D.wang-6tisch-6top-sublayer] 3342 Wang, Q. and X. Vilajosana, "6TiSCH Operation Sublayer 3343 (6top)", draft-wang-6tisch-6top-sublayer-04 (work in 3344 progress), November 2015. 3346 [IEC61850-90-12] 3347 TC57 WG10, IEC., "IEC 61850-90-12 TR: Communication 3348 networks and systems for power utility automation - Part 3349 90-12: Wide area network engineering guidelines", 2015. 3351 [IEC62439-3:2012] 3352 TC65, IEC., "IEC 62439-3: Industrial communication 3353 networks - High availability automation networks - Part 3: 3354 Parallel Redundancy Protocol (PRP) and High-availability 3355 Seamless Redundancy (HSR)", 2012. 3357 [IEEE1588] 3358 IEEE, "IEEE Standard for a Precision Clock Synchronization 3359 Protocol for Networked Measurement and Control Systems", 3360 IEEE Std 1588-2008, 2008, 3361 . 3364 [IEEE1722] 3365 IEEE, "1722-2011 - IEEE Standard for Layer 2 Transport 3366 Protocol for Time Sensitive Applications in a Bridged 3367 Local Area Network", IEEE Std 1722-2011, 2011, 3368 . 3371 [IEEE19043] 3372 IEEE Standards Association, "IEEE 1904.3 TF", IEEE 1904.3, 3373 2015, . 3375 [IEEE802.1TSNTG] 3376 IEEE Standards Association, "IEEE 802.1 Time-Sensitive 3377 Networks Task Group", March 2013, 3378 . 3380 [IEEE802154] 3381 IEEE standard for Information Technology, "IEEE std. 3382 802.15.4, Part. 15.4: Wireless Medium Access Control (MAC) 3383 and Physical Layer (PHY) Specifications for Low-Rate 3384 Wireless Personal Area Networks". 3386 [IEEE802154e] 3387 IEEE standard for Information Technology, "IEEE standard 3388 for Information Technology, IEEE std. 802.15.4, Part. 3389 15.4: Wireless Medium Access Control (MAC) and Physical 3390 Layer (PHY) Specifications for Low-Rate Wireless Personal 3391 Area Networks, June 2011 as amended by IEEE std. 3392 802.15.4e, Part. 15.4: Low-Rate Wireless Personal Area 3393 Networks (LR-WPANs) Amendment 1: MAC sublayer", April 3394 2012. 3396 [IEEE8021AS] 3397 IEEE, "Timing and Synchronizations (IEEE 802.1AS-2011)", 3398 IEEE 802.1AS-2001, 2011, 3399 . 3402 [IEEE8021CM] 3403 Farkas, J., "Time-Sensitive Networking for Fronthaul", 3404 Unapproved PAR, PAR for a New IEEE Standard; 3405 IEEE P802.1CM, April 2015, 3406 . 3409 [IEEE8021TSN] 3410 IEEE 802.1, "The charter of the TG is to provide the 3411 specifications that will allow time-synchronized low 3412 latency streaming services through 802 networks.", 2016, 3413 . 3415 [IETFDetNet] 3416 IETF, "Charter for IETF DetNet Working Group", 2015, 3417 . 3419 [ISA100] ISA/ANSI, "ISA100, Wireless Systems for Automation", 3420 . 3422 [ISA100.11a] 3423 ISA/ANSI, "Wireless Systems for Industrial Automation: 3424 Process Control and Related Applications - ISA100.11a-2011 3425 - IEC 62734", 2011, . 3428 [ISO7240-16] 3429 ISO, "ISO 7240-16:2007 Fire detection and alarm systems -- 3430 Part 16: Sound system control and indicating equipment", 3431 2007, . 3434 [knx] KNX Association, "ISO/IEC 14543-3 - KNX", November 2006. 3436 [lontalk] ECHELON, "LonTalk(R) Protocol Specification Version 3.0", 3437 1994. 3439 [LTE-Latency] 3440 Johnston, S., "LTE Latency: How does it compare to other 3441 technologies", March 2014, 3442 . 3445 [MEF] MEF, "Mobile Backhaul Phase 2 Amendment 1 -- Small Cells", 3446 MEF 22.1.1, July 2014, 3447 . 3450 [METIS] METIS, "Scenarios, requirements and KPIs for 5G mobile and 3451 wireless system", ICT-317669-METIS/D1.1 ICT- 3452 317669-METIS/D1.1, April 2013, . 3455 [modbus] Modbus Organization, "MODBUS APPLICATION PROTOCOL 3456 SPECIFICATION V1.1b", December 2006. 3458 [net5G] Ericsson, "5G Radio Access, Challenges for 2020 and 3459 Beyond", Ericsson white paper wp-5g, June 2013, 3460 . 3462 [NGMN] NGMN Alliance, "5G White Paper", NGMN 5G White Paper v1.0, 3463 February 2015, . 3466 [PCE] IETF, "Path Computation Element", 3467 . 3469 [profibus] 3470 IEC, "IEC 61158 Type 3 - Profibus DP", January 2001. 3472 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 3473 Requirement Levels", BCP 14, RFC 2119, 3474 DOI 10.17487/RFC2119, March 1997, 3475 . 3477 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 3478 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, 3479 December 1998, . 3481 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 3482 "Definition of the Differentiated Services Field (DS 3483 Field) in the IPv4 and IPv6 Headers", RFC 2474, 3484 DOI 10.17487/RFC2474, December 1998, 3485 . 3487 [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol 3488 Label Switching Architecture", RFC 3031, 3489 DOI 10.17487/RFC3031, January 2001, 3490 . 3492 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 3493 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 3494 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 3495 . 3497 [RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation 3498 Metric for IP Performance Metrics (IPPM)", RFC 3393, 3499 DOI 10.17487/RFC3393, November 2002, 3500 . 3502 [RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between 3503 Information Models and Data Models", RFC 3444, 3504 DOI 10.17487/RFC3444, January 2003, 3505 . 3507 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 3508 RFC 3972, DOI 10.17487/RFC3972, March 2005, 3509 . 3511 [RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation 3512 Edge-to-Edge (PWE3) Architecture", RFC 3985, 3513 DOI 10.17487/RFC3985, March 2005, 3514 . 3516 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 3517 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 3518 2006, . 3520 [RFC4553] Vainshtein, A., Ed. and YJ. Stein, Ed., "Structure- 3521 Agnostic Time Division Multiplexing (TDM) over Packet 3522 (SAToP)", RFC 4553, DOI 10.17487/RFC4553, June 2006, 3523 . 3525 [RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903, 3526 DOI 10.17487/RFC4903, June 2007, 3527 . 3529 [RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6 3530 over Low-Power Wireless Personal Area Networks (6LoWPANs): 3531 Overview, Assumptions, Problem Statement, and Goals", 3532 RFC 4919, DOI 10.17487/RFC4919, August 2007, 3533 . 3535 [RFC5086] Vainshtein, A., Ed., Sasson, I., Metz, E., Frost, T., and 3536 P. Pate, "Structure-Aware Time Division Multiplexed (TDM) 3537 Circuit Emulation Service over Packet Switched Network 3538 (CESoPSN)", RFC 5086, DOI 10.17487/RFC5086, December 2007, 3539 . 3541 [RFC5087] Stein, Y(J)., Shashoua, R., Insler, R., and M. Anavi, 3542 "Time Division Multiplexing over IP (TDMoIP)", RFC 5087, 3543 DOI 10.17487/RFC5087, December 2007, 3544 . 3546 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 3547 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 3548 DOI 10.17487/RFC6282, September 2011, 3549 . 3551 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 3552 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 3553 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 3554 Low-Power and Lossy Networks", RFC 6550, 3555 DOI 10.17487/RFC6550, March 2012, 3556 . 3558 [RFC6551] Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N., 3559 and D. Barthel, "Routing Metrics Used for Path Calculation 3560 in Low-Power and Lossy Networks", RFC 6551, 3561 DOI 10.17487/RFC6551, March 2012, 3562 . 3564 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 3565 Bormann, "Neighbor Discovery Optimization for IPv6 over 3566 Low-Power Wireless Personal Area Networks (6LoWPANs)", 3567 RFC 6775, DOI 10.17487/RFC6775, November 2012, 3568 . 3570 [RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using 3571 IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the 3572 Internet of Things (IoT): Problem Statement", RFC 7554, 3573 DOI 10.17487/RFC7554, May 2015, 3574 . 3576 [SRP_LATENCY] 3577 Gunther, C., "Specifying SRP Latency", 2014, 3578 . 3581 [STUDIO_IP] 3582 Mace, G., "IP Networked Studio Infrastructure for 3583 Synchronized & Real-Time Multimedia Transmissions", 2007, 3584 . 3587 [SyncE] ITU-T, "G.8261 : Timing and synchronization aspects in 3588 packet networks", Recommendation G.8261, August 2013, 3589 . 3591 [TEAS] IETF, "Traffic Engineering Architecture and Signaling", 3592 . 3594 [TS23401] 3GPP, "General Packet Radio Service (GPRS) enhancements 3595 for Evolved Universal Terrestrial Radio Access Network 3596 (E-UTRAN) access", 3GPP TS 23.401 10.10.0, March 2013. 3598 [TS25104] 3GPP, "Base Station (BS) radio transmission and reception 3599 (FDD)", 3GPP TS 25.104 3.14.0, March 2007. 3601 [TS36104] 3GPP, "Evolved Universal Terrestrial Radio Access 3602 (E-UTRA); Base Station (BS) radio transmission and 3603 reception", 3GPP TS 36.104 10.11.0, July 2013. 3605 [TS36133] 3GPP, "Evolved Universal Terrestrial Radio Access 3606 (E-UTRA); Requirements for support of radio resource 3607 management", 3GPP TS 36.133 12.7.0, April 2015. 3609 [TS36211] 3GPP, "Evolved Universal Terrestrial Radio Access 3610 (E-UTRA); Physical channels and modulation", 3GPP 3611 TS 36.211 10.7.0, March 2013. 3613 [TS36300] 3GPP, "Evolved Universal Terrestrial Radio Access (E-UTRA) 3614 and Evolved Universal Terrestrial Radio Access Network 3615 (E-UTRAN); Overall description; Stage 2", 3GPP TS 36.300 3616 10.11.0, September 2013. 3618 [TSNTG] IEEE Standards Association, "IEEE 802.1 Time-Sensitive 3619 Networks Task Group", 2013, 3620 . 3622 [UHD-video] 3623 Holub, P., "Ultra-High Definition Videos and Their 3624 Applications over the Network", The 7th International 3625 Symposium on VICTORIES Project PetrHolub_presentation, 3626 October 2014, . 3629 [WirelessHART] 3630 www.hartcomm.org, "Industrial Communication Networks - 3631 Wireless Communication Network and Communication Profiles 3632 - WirelessHART - IEC 62591", 2010. 3634 Authors' Addresses 3635 Ethan Grossman (editor) 3636 Dolby Laboratories, Inc. 3637 1275 Market Street 3638 San Francisco, CA 94103 3639 USA 3641 Phone: +1 415 645 4726 3642 Email: ethan.grossman@dolby.com 3643 URI: http://www.dolby.com 3645 Craig Gunther 3646 Harman International 3647 10653 South River Front Parkway 3648 South Jordan, UT 84095 3649 USA 3651 Phone: +1 801 568-7675 3652 Email: craig.gunther@harman.com 3653 URI: http://www.harman.com 3655 Pascal Thubert 3656 Cisco Systems, Inc 3657 Building D 3658 45 Allee des Ormes - BP1200 3659 MOUGINS - Sophia Antipolis 06254 3660 FRANCE 3662 Phone: +33 497 23 26 34 3663 Email: pthubert@cisco.com 3665 Patrick Wetterwald 3666 Cisco Systems 3667 45 Allees des Ormes 3668 Mougins 06250 3669 FRANCE 3671 Phone: +33 4 97 23 26 36 3672 Email: pwetterw@cisco.com 3673 Jean Raymond 3674 Hydro-Quebec 3675 1500 University 3676 Montreal H3A3S7 3677 Canada 3679 Phone: +1 514 840 3000 3680 Email: raymond.jean@hydro.qc.ca 3682 Jouni Korhonen 3683 Broadcom Corporation 3684 3151 Zanker Road 3685 San Jose, CA 95134 3686 USA 3688 Email: jouni.nospam@gmail.com 3690 Yu Kaneko 3691 Toshiba 3692 1 Komukai-Toshiba-cho, Saiwai-ku, Kasasaki-shi 3693 Kanagawa, Japan 3695 Email: yu1.kaneko@toshiba.co.jp 3697 Subir Das 3698 Applied Communication Sciences 3699 150 Mount Airy Road, Basking Ridge 3700 New Jersey, 07920, USA 3702 Email: sdas@appcomsci.com 3704 Yiyong Zha 3705 Huawei Technologies 3707 Email: zhayiyong@huawei.com 3709 Balazs Varga 3710 Ericsson 3711 Konyves Kalman krt. 11/B 3712 Budapest 1097 3713 Hungary 3715 Email: balazs.a.varga@ericsson.com 3716 Janos Farkas 3717 Ericsson 3718 Konyves Kalman krt. 11/B 3719 Budapest 1097 3720 Hungary 3722 Email: janos.farkas@ericsson.com 3724 Franz-Josef Goetz 3725 Siemens 3726 Gleiwitzerstr. 555 3727 Nurnberg 90475 3728 Germany 3730 Email: franz-josef.goetz@siemens.com 3732 Juergen Schmitt 3733 Siemens 3734 Gleiwitzerstr. 555 3735 Nurnberg 90475 3736 Germany 3738 Email: juergen.jues.schmitt@siemens.com