idnits 2.17.1 draft-ietf-detnet-use-cases-06.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- ** The document seems to lack an IANA Considerations section. (See Section 2.2 of https://www.ietf.org/id-info/checklist for how to handle the case when there are no actions for IANA.) Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (March 4, 2016) is 2974 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- == Unused Reference: 'ACE' is defined on line 2768, but no explicit reference was found in the text == Unused Reference: 'CCAMP' is defined on line 2776, but no explicit reference was found in the text == Unused Reference: 'DICE' is defined on line 2798, but no explicit reference was found in the text == Unused Reference: 'EA12' is defined on line 2801, but no explicit reference was found in the text == Unused Reference: 'HART' is defined on line 2818, but no explicit reference was found in the text == Unused Reference: 'I-D.ietf-6tisch-terminology' is defined on line 2847, but no explicit reference was found in the text == Unused Reference: 'I-D.ietf-ipv6-multilink-subnets' is defined on line 2853, but no explicit reference was found in the text == Unused Reference: 'I-D.ietf-roll-rpl-industrial-applicability' is defined on line 2858, but no explicit reference was found in the text == Unused Reference: 'I-D.thubert-6lowpan-backbone-router' is defined on line 2886, but no explicit reference was found in the text == Unused Reference: 'IEC61850-90-12' is defined on line 2896, but no explicit reference was found in the text == Unused Reference: 'IEEE8021TSN' is defined on line 2959, but no explicit reference was found in the text == Unused Reference: 'IETFDetNet' is defined on line 2965, but no explicit reference was found in the text == Unused Reference: 'RFC2119' is defined on line 3022, but no explicit reference was found in the text == Unused Reference: 'RFC2460' is defined on line 3027, but no explicit reference was found in the text == Unused Reference: 'RFC2474' is defined on line 3031, but no explicit reference was found in the text == Unused Reference: 'RFC3209' is defined on line 3042, but no explicit reference was found in the text == Unused Reference: 'RFC3393' is defined on line 3047, but no explicit reference was found in the text == Unused Reference: 'RFC3444' is defined on line 3052, but no explicit reference was found in the text == Unused Reference: 'RFC3972' is defined on line 3057, but no explicit reference was found in the text == Unused Reference: 'RFC4291' is defined on line 3066, but no explicit reference was found in the text == Unused Reference: 'RFC4903' is defined on line 3075, but no explicit reference was found in the text == Unused Reference: 'RFC4919' is defined on line 3079, but no explicit reference was found in the text == Unused Reference: 'RFC6282' is defined on line 3096, but no explicit reference was found in the text == Unused Reference: 'RFC6775' is defined on line 3114, but no explicit reference was found in the text == Unused Reference: 'TEAS' is defined on line 3141, but no explicit reference was found in the text == Unused Reference: 'UHD-video' is defined on line 3172, but no explicit reference was found in the text == Outdated reference: A later version (-08) exists of draft-finn-detnet-architecture-03 == Outdated reference: A later version (-05) exists of draft-finn-detnet-problem-statement-04 == Outdated reference: A later version (-30) exists of draft-ietf-6tisch-architecture-09 == Outdated reference: A later version (-10) exists of draft-ietf-6tisch-terminology-06 -- Obsolete informational reference (is this intentional?): RFC 2460 (Obsoleted by RFC 8200) Summary: 1 error (**), 0 flaws (~~), 31 warnings (==), 2 comments (--). 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: September 5, 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 March 4, 2016 27 Deterministic Networking Use Cases 28 draft-ietf-detnet-use-cases-06 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 September 5, 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. Electrical Utilities . . . . . . . . . . . . . . . . . . . . 13 107 3.1. Use Case Description . . . . . . . . . . . . . . . . . . 13 108 3.1.1. Transmission Use Cases . . . . . . . . . . . . . . . 13 109 3.1.1.1. Protection . . . . . . . . . . . . . . . . . . . 13 110 3.1.1.2. Intra-Substation Process Bus Communications . . . 19 111 3.1.1.3. Wide Area Monitoring and Control Systems . . . . 20 112 3.1.1.4. IEC 61850 WAN engineering guidelines requirement 113 classification . . . . . . . . . . . . . . . . . 21 114 3.1.2. Generation Use Case . . . . . . . . . . . . . . . . . 22 115 3.1.3. Distribution use case . . . . . . . . . . . . . . . . 23 116 3.1.3.1. Fault Location Isolation and Service Restoration 117 (FLISR) . . . . . . . . . . . . . . . . . . . . . 23 118 3.2. Electrical Utilities Today . . . . . . . . . . . . . . . 24 119 3.2.1. Security Current Practices and Limitations . . . . . 24 120 3.3. Electrical Utilities Future . . . . . . . . . . . . . . . 26 121 3.3.1. Migration to Packet-Switched Network . . . . . . . . 26 122 3.3.2. Telecommunications Trends . . . . . . . . . . . . . . 27 123 3.3.2.1. General Telecommunications Requirements . . . . . 27 124 3.3.2.2. Specific Network topologies of Smart Grid 125 Applications . . . . . . . . . . . . . . . . . . 28 126 3.3.2.3. Precision Time Protocol . . . . . . . . . . . . . 29 127 3.3.3. Security Trends in Utility Networks . . . . . . . . . 30 128 3.4. Electrical Utilities Asks . . . . . . . . . . . . . . . . 32 129 4. Building Automation Systems . . . . . . . . . . . . . . . . . 32 130 4.1. Use Case Description . . . . . . . . . . . . . . . . . . 32 131 4.2. Building Automation Systems Today . . . . . . . . . . . . 32 132 4.2.1. BAS Architecture . . . . . . . . . . . . . . . . . . 33 133 4.2.2. BAS Deployment Model . . . . . . . . . . . . . . . . 34 134 4.2.3. Use Cases for Field Networks . . . . . . . . . . . . 36 135 4.2.3.1. Environmental Monitoring . . . . . . . . . . . . 36 136 4.2.3.2. Fire Detection . . . . . . . . . . . . . . . . . 36 137 4.2.3.3. Feedback Control . . . . . . . . . . . . . . . . 37 138 4.2.4. Security Considerations . . . . . . . . . . . . . . . 37 139 4.3. BAS Future . . . . . . . . . . . . . . . . . . . . . . . 37 140 4.4. BAS Asks . . . . . . . . . . . . . . . . . . . . . . . . 38 141 5. Wireless for Industrial . . . . . . . . . . . . . . . . . . . 38 142 5.1. Use Case Description . . . . . . . . . . . . . . . . . . 38 143 5.1.1. Network Convergence using 6TiSCH . . . . . . . . . . 39 144 5.1.2. Common Protocol Development for 6TiSCH . . . . . . . 39 146 5.2. Wireless Industrial Today . . . . . . . . . . . . . . . . 40 147 5.3. Wireless Industrial Future . . . . . . . . . . . . . . . 40 148 5.3.1. Unified Wireless Network and Management . . . . . . . 40 149 5.3.1.1. PCE and 6TiSCH ARQ Retries . . . . . . . . . . . 42 150 5.3.2. Schedule Management by a PCE . . . . . . . . . . . . 43 151 5.3.2.1. PCE Commands and 6TiSCH CoAP Requests . . . . . . 43 152 5.3.2.2. 6TiSCH IP Interface . . . . . . . . . . . . . . . 44 153 5.3.3. 6TiSCH Security Considerations . . . . . . . . . . . 44 154 5.4. Wireless Industrial Asks . . . . . . . . . . . . . . . . 45 155 6. Cellular Radio Use Cases . . . . . . . . . . . . . . . . . . 45 156 6.1. Use Case Description . . . . . . . . . . . . . . . . . . 45 157 6.1.1. Network Architecture . . . . . . . . . . . . . . . . 45 158 6.1.2. Time Synchronization Requirements . . . . . . . . . . 46 159 6.1.3. Time-Sensitive Stream Requirements . . . . . . . . . 48 160 6.1.4. Security Considerations . . . . . . . . . . . . . . . 48 161 6.2. Cellular Radio Networks Today . . . . . . . . . . . . . . 49 162 6.3. Cellular Radio Networks Future . . . . . . . . . . . . . 49 163 6.4. Cellular Radio Networks Asks . . . . . . . . . . . . . . 51 164 7. Cellular Coordinated Multipoint Processing (CoMP) . . . . . . 51 165 7.1. Use Case Description . . . . . . . . . . . . . . . . . . 51 166 7.1.1. CoMP Architecture . . . . . . . . . . . . . . . . . . 52 167 7.1.2. Delay Sensitivity in CoMP . . . . . . . . . . . . . . 53 168 7.2. CoMP Today . . . . . . . . . . . . . . . . . . . . . . . 53 169 7.3. CoMP Future . . . . . . . . . . . . . . . . . . . . . . . 53 170 7.3.1. Mobile Industry Overall Goals . . . . . . . . . . . . 53 171 7.3.2. CoMP Infrastructure Goals . . . . . . . . . . . . . . 54 172 7.4. CoMP Asks . . . . . . . . . . . . . . . . . . . . . . . . 54 173 8. Industrial M2M . . . . . . . . . . . . . . . . . . . . . . . 55 174 8.1. Use Case Description . . . . . . . . . . . . . . . . . . 55 175 8.2. Industrial M2M Communication Today . . . . . . . . . . . 56 176 8.2.1. Transport Parameters . . . . . . . . . . . . . . . . 56 177 8.2.2. Stream Creation and Destruction . . . . . . . . . . . 57 178 8.3. Industrial M2M Future . . . . . . . . . . . . . . . . . . 57 179 8.4. Industrial M2M Asks . . . . . . . . . . . . . . . . . . . 58 180 9. Internet-based Applications . . . . . . . . . . . . . . . . . 58 181 9.1. Use Case Description . . . . . . . . . . . . . . . . . . 58 182 9.1.1. Media Content Delivery . . . . . . . . . . . . . . . 58 183 9.1.2. Online Gaming . . . . . . . . . . . . . . . . . . . . 58 184 9.1.3. Virtual Reality . . . . . . . . . . . . . . . . . . . 58 185 9.2. Internet-Based Applications Today . . . . . . . . . . . . 59 186 9.3. Internet-Based Applications Future . . . . . . . . . . . 59 187 9.4. Internet-Based Applications Asks . . . . . . . . . . . . 59 188 10. Use Case Common Elements . . . . . . . . . . . . . . . . . . 59 189 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 60 190 11.1. Pro Audio . . . . . . . . . . . . . . . . . . . . . . . 60 191 11.2. Utility Telecom . . . . . . . . . . . . . . . . . . . . 61 192 11.3. Building Automation Systems . . . . . . . . . . . . . . 61 193 11.4. Wireless for Industrial . . . . . . . . . . . . . . . . 61 194 11.5. Cellular Radio . . . . . . . . . . . . . . . . . . . . . 61 195 11.6. Industrial M2M . . . . . . . . . . . . . . . . . . . . . 61 196 11.7. Internet Applications and CoMP . . . . . . . . . . . . . 61 197 12. Informative References . . . . . . . . . . . . . . . . . . . 62 198 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 70 200 1. Introduction 202 This draft presents use cases from diverse industries which have in 203 common a need for deterministic streams, but which also differ 204 notably in their network topologies and specific desired behavior. 205 Together, they provide broad industry context for DetNet and a 206 yardstick against which proposed DetNet designs can be measured (to 207 what extent does a proposed design satisfy these various use cases?) 209 For DetNet, use cases explicitly do not define requirements; The 210 DetNet WG will consider the use cases, decide which elements are in 211 scope for DetNet, and the results will be incorporated into future 212 drafts. Similarly, the DetNet use case draft explicitly does not 213 suggest any specific design, architecture or protocols, which will be 214 topics of future drafts. 216 We present for each use case the answers to the following questions: 218 o What is the use case? 220 o How is it addressed today? 222 o How would you like it to be addressed in the future? 224 o What do you want the IETF to deliver? 226 The level of detail in each use case should be sufficient to express 227 the relevant elements of the use case, but not more. 229 At the end we consider the use cases collectively, and examine the 230 most significant goals they have in common. 232 2. Pro Audio Use Cases 234 2.1. Introduction 236 The professional audio and video industry includes music and film 237 content creation, broadcast, cinema, and live exposition as well as 238 public address, media and emergency systems at large venues 239 (airports, stadiums, churches, theme parks). These industries have 240 already gone through the transition of audio and video signals from 241 analog to digital, however the interconnect systems remain primarily 242 point-to-point with a single (or small number of) signals per link, 243 interconnected with purpose-built hardware. 245 These industries are now attempting to transition to packet based 246 infrastructure for distributing audio and video in order to reduce 247 cost, increase routing flexibility, and integrate with existing IT 248 infrastructure. 250 However, there are several requirements for making a network the 251 primary infrastructure for audio and video which are not met by 252 todays networks and these are our concern in this draft. 254 The principal requirement is that pro audio and video applications 255 become able to establish streams that provide guaranteed (bounded) 256 bandwidth and latency from the Layer 3 (IP) interface. Such streams 257 can be created today within standards-based layer 2 islands however 258 these are not sufficient to enable effective distribution over wider 259 areas (for example broadcast events that span wide geographical 260 areas). 262 Some proprietary systems have been created which enable deterministic 263 streams at layer 3 however they are engineered networks in that they 264 require careful configuration to operate, often require that the 265 system be over designed, and it is implied that all devices on the 266 network voluntarily play by the rules of that network. To enable 267 these industries to successfully transition to an interoperable 268 multi-vendor packet-based infrastructure requires effective open 269 standards, and we believe that establishing relevant IETF standards 270 is a crucial factor. 272 It would be highly desirable if such streams could be routed over the 273 open Internet, however even intermediate solutions with more limited 274 scope (such as enterprise networks) can provide a substantial 275 improvement over todays networks, and a solution that only provides 276 for the enterprise network scenario is an acceptable first step. 278 We also present more fine grained requirements of the audio and video 279 industries such as safety and security, redundant paths, devices with 280 limited computing resources on the network, and that reserved stream 281 bandwidth is available for use by other best-effort traffic when that 282 stream is not currently in use. 284 2.2. Fundamental Stream Requirements 286 The fundamental stream properties are guaranteed bandwidth and 287 deterministic latency as described in this section. Additional 288 stream requirements are described in a subsequent section. 290 2.2.1. Guaranteed Bandwidth 292 Transmitting audio and video streams is unlike common file transfer 293 activities because guaranteed delivery cannot be achieved by re- 294 trying the transmission; by the time the missing or corrupt packet 295 has been identified it is too late to execute a re-try operation and 296 stream playback is interrupted, which is unacceptable in for example 297 a live concert. In some contexts large amounts of buffering can be 298 used to provide enough delay to allow time for one or more retries, 299 however this is not an effective solution when live interaction is 300 involved, and is not considered an acceptable general solution for 301 pro audio and video. (Have you ever tried speaking into a microphone 302 through a sound system that has an echo coming back at you? It makes 303 it almost impossible to speak clearly). 305 Providing a way to reserve a specific amount of bandwidth for a given 306 stream is a key requirement. 308 2.2.2. Bounded and Consistent Latency 310 Latency in this context means the amount of time that passes between 311 when a signal is sent over a stream and when it is received, for 312 example the amount of time delay between when you speak into a 313 microphone and when your voice emerges from the speaker. Any delay 314 longer than about 10-15 milliseconds is noticeable by most live 315 performers, and greater latency makes the system unusable because it 316 prevents them from playing in time with the other players (see slide 317 6 of [SRP_LATENCY]). 319 The 15ms latency bound is made even more challenging because it is 320 often the case in network based music production with live electric 321 instruments that multiple stages of signal processing are used, 322 connected in series (i.e. from one to the other for example from 323 guitar through a series of digital effects processors) in which case 324 the latencies add, so the latencies of each individual stage must all 325 together remain less than 15ms. 327 In some situations it is acceptable at the local location for content 328 from the live remote site to be delayed to allow for a statistically 329 acceptable amount of latency in order to reduce jitter. However, 330 once the content begins playing in the local location any audio 331 artifacts caused by the local network are unacceptable, especially in 332 those situations where a live local performer is mixed into the feed 333 from the remote location. 335 In addition to being bounded to within some predictable and 336 acceptable amount of time (which may be 15 milliseconds or more or 337 less depending on the application) the latency also has to be 338 consistent. For example when playing a film consisting of a video 339 stream and audio stream over a network, those two streams must be 340 synchronized so that the voice and the picture match up. A common 341 tolerance for audio/video sync is one NTSC video frame (about 33ms) 342 and to maintain the audience perception of correct lip sync the 343 latency needs to be consistent within some reasonable tolerance, for 344 example 10%. 346 A common architecture for synchronizing multiple streams that have 347 different paths through the network (and thus potentially different 348 latencies) is to enable measurement of the latency of each path, and 349 have the data sinks (for example speakers) buffer (delay) all packets 350 on all but the slowest path. Each packet of each stream is assigned 351 a presentation time which is based on the longest required delay. 352 This implies that all sinks must maintain a common time reference of 353 sufficient accuracy, which can be achieved by any of various 354 techniques. 356 This type of architecture is commonly implemented using a central 357 controller that determines path delays and arbitrates buffering 358 delays. 360 2.2.2.1. Optimizations 362 The controller might also perform optimizations based on the 363 individual path delays, for example sinks that are closer to the 364 source can inform the controller that they can accept greater latency 365 since they will be buffering packets to match presentation times of 366 farther away sinks. The controller might then move a stream 367 reservation on a short path to a longer path in order to free up 368 bandwidth for other critical streams on that short path. See slides 369 3-5 of [SRP_LATENCY]. 371 Additional optimization can be achieved in cases where sinks have 372 differing latency requirements, for example in a live outdoor concert 373 the speaker sinks have stricter latency requirements than the 374 recording hardware sinks. See slide 7 of [SRP_LATENCY]. 376 Device cost can be reduced in a system with guaranteed reservations 377 with a small bounded latency due to the reduced requirements for 378 buffering (i.e. memory) on sink devices. For example, a theme park 379 might broadcast a live event across the globe via a layer 3 protocol; 380 in such cases the size of the buffers required is proportional to the 381 latency bounds and jitter caused by delivery, which depends on the 382 worst case segment of the end-to-end network path. For example on 383 todays open internet the latency is typically unacceptable for audio 384 and video streaming without many seconds of buffering. In such 385 scenarios a single gateway device at the local network that receives 386 the feed from the remote site would provide the expensive buffering 387 required to mask the latency and jitter issues associated with long 388 distance delivery. Sink devices in the local location would have no 389 additional buffering requirements, and thus no additional costs, 390 beyond those required for delivery of local content. The sink device 391 would be receiving the identical packets as those sent by the source 392 and would be unaware that there were any latency or jitter issues 393 along the path. 395 2.3. Additional Stream Requirements 397 The requirements in this section are more specific yet are common to 398 multiple audio and video industry applications. 400 2.3.1. Deterministic Time to Establish Streaming 402 Some audio systems installed in public environments (airports, 403 hospitals) have unique requirements with regards to health, safety 404 and fire concerns. One such requirement is a maximum of 3 seconds 405 for a system to respond to an emergency detection and begin sending 406 appropriate warning signals and alarms without human intervention. 407 For this requirement to be met, the system must support a bounded and 408 acceptable time from a notification signal to specific stream 409 establishment. For further details see [ISO7240-16]. 411 Similar requirements apply when the system is restarted after a power 412 cycle, cable re-connection, or system reconfiguration. 414 In many cases such re-establishment of streaming state must be 415 achieved by the peer devices themselves, i.e. without a central 416 controller (since such a controller may only be present during 417 initial network configuration). 419 Video systems introduce related requirements, for example when 420 transitioning from one camera feed to another. Such systems 421 currently use purpose-built hardware to switch feeds smoothly, 422 however there is a current initiative in the broadcast industry to 423 switch to a packet-based infrastructure (see [STUDIO_IP] and the ESPN 424 DC2 use case described below). 426 2.3.2. Use of Unused Reservations by Best-Effort Traffic 428 In cases where stream bandwidth is reserved but not currently used 429 (or is under-utilized) that bandwidth must be available to best- 430 effort (i.e. non-time-sensitive) traffic. For example a single 431 stream may be nailed up (reserved) for specific media content that 432 needs to be presented at different times of the day, ensuring timely 433 delivery of that content, yet in between those times the full 434 bandwidth of the network can be utilized for best-effort tasks such 435 as file transfers. 437 This also addresses a concern of IT network administrators that are 438 considering adding reserved bandwidth traffic to their networks that 439 users will just reserve a ton of bandwidth and then never un-reserve 440 it even though they are not using it, and soon they will have no 441 bandwidth left. 443 2.3.3. Layer 3 Interconnecting Layer 2 Islands 445 As an intermediate step (short of providing guaranteed bandwidth 446 across the open internet) it would be valuable to provide a way to 447 connect multiple Layer 2 networks. For example layer 2 techniques 448 could be used to create a LAN for a single broadcast studio, and 449 several such studios could be interconnected via layer 3 links. 451 2.3.4. Secure Transmission 453 Digital Rights Management (DRM) is very important to the audio and 454 video industries. Any time protected content is introduced into a 455 network there are DRM concerns that must be maintained (see 456 [CONTENT_PROTECTION]). Many aspects of DRM are outside the scope of 457 network technology, however there are cases when a secure link 458 supporting authentication and encryption is required by content 459 owners to carry their audio or video content when it is outside their 460 own secure environment (for example see [DCI]). 462 As an example, two techniques are Digital Transmission Content 463 Protection (DTCP) and High-Bandwidth Digital Content Protection 464 (HDCP). HDCP content is not approved for retransmission within any 465 other type of DRM, while DTCP may be retransmitted under HDCP. 466 Therefore if the source of a stream is outside of the network and it 467 uses HDCP protection it is only allowed to be placed on the network 468 with that same HDCP protection. 470 2.3.5. Redundant Paths 472 On-air and other live media streams must be backed up with redundant 473 links that seamlessly act to deliver the content when the primary 474 link fails for any reason. In point-to-point systems this is 475 provided by an additional point-to-point link; the analogous 476 requirement in a packet-based system is to provide an alternate path 477 through the network such that no individual link can bring down the 478 system. 480 2.3.6. Link Aggregation 482 For transmitting streams that require more bandwidth than a single 483 link in the target network can support, link aggregation is a 484 technique for combining (aggregating) the bandwidth available on 485 multiple physical links to create a single logical link of the 486 required bandwidth. However, if aggregation is to be used, the 487 network controller (or equivalent) must be able to determine the 488 maximum latency of any path through the aggregate link (see Bounded 489 and Consistent Latency section above). 491 2.3.7. Traffic Segregation 493 Sink devices may be low cost devices with limited processing power. 494 In order to not overwhelm the CPUs in these devices it is important 495 to limit the amount of traffic that these devices must process. 497 As an example, consider the use of individual seat speakers in a 498 cinema. These speakers are typically required to be cost reduced 499 since the quantities in a single theater can reach hundreds of seats. 500 Discovery protocols alone in a one thousand seat theater can generate 501 enough broadcast traffic to overwhelm a low powered CPU. Thus an 502 installation like this will benefit greatly from some type of traffic 503 segregation that can define groups of seats to reduce traffic within 504 each group. All seats in the theater must still be able to 505 communicate with a central controller. 507 There are many techniques that can be used to support this 508 requirement including (but not limited to) the following examples. 510 2.3.7.1. Packet Forwarding Rules, VLANs and Subnets 512 Packet forwarding rules can be used to eliminate some extraneous 513 streaming traffic from reaching potentially low powered sink devices, 514 however there may be other types of broadcast traffic that should be 515 eliminated using other means for example VLANs or IP subnets. 517 2.3.7.2. Multicast Addressing (IPv4 and IPv6) 519 Multicast addressing is commonly used to keep bandwidth utilization 520 of shared links to a minimum. 522 Because of the MAC Address forwarding nature of Layer 2 bridges it is 523 important that a multicast MAC address is only associated with one 524 stream. This will prevent reservations from forwarding packets from 525 one stream down a path that has no interested sinks simply because 526 there is another stream on that same path that shares the same 527 multicast MAC address. 529 Since each multicast MAC Address can represent 32 different IPv4 530 multicast addresses there must be a process put in place to make sure 531 this does not occur. Requiring use of IPv6 address can achieve this, 532 however due to their continued prevalence, solutions that are 533 effective for IPv4 installations are also required. 535 2.4. Integration of Reserved Streams into IT Networks 537 A commonly cited goal of moving to a packet based media 538 infrastructure is that costs can be reduced by using off the shelf, 539 commodity network hardware. In addition, economy of scale can be 540 realized by combining media infrastructure with IT infrastructure. 541 In keeping with these goals, stream reservation technology should be 542 compatible with existing protocols, and not compromise use of the 543 network for best effort (non-time-sensitive) traffic. 545 2.5. Security Considerations 547 Many industries that are moving from the point-to-point world to the 548 digital network world have little understanding of the pitfalls that 549 they can create for themselves with improperly implemented network 550 infrastructure. DetNet should consider ways to provide security 551 against DoS attacks in solutions directed at these markets. Some 552 considerations are given here as examples of ways that we can help 553 new users avoid common pitfalls. 555 2.5.1. Denial of Service 557 One security pitfall that this author is aware of involves the use of 558 technology that allows a presenter to throw the content from their 559 tablet or smart phone onto the A/V system that is then viewed by all 560 those in attendance. The facility introducing this technology was 561 quite excited to allow such modern flexibility to those who came to 562 speak. One thing they hadn't realized was that since no security was 563 put in place around this technology it left a hole in the system that 564 allowed other attendees to "throw" their own content onto the A/V 565 system. 567 2.5.2. Control Protocols 569 Professional audio systems can include amplifiers that are capable of 570 generating hundreds or thousands of watts of audio power which if 571 used incorrectly can cause hearing damage to those in the vicinity. 572 Apart from the usual care required by the systems operators to 573 prevent such incidents, the network traffic that controls these 574 devices must be secured (as with any sensitive application traffic). 575 In addition, it would be desirable if the configuration protocols 576 that are used to create the network paths used by the professional 577 audio traffic could be designed to protect devices that are not meant 578 to receive high-amplitude content from having such potentially 579 damaging signals routed to them. 581 2.6. A State-of-the-Art Broadcast Installation Hits Technology Limits 583 ESPN recently constructed a state-of-the-art 194,000 sq ft, $125 584 million broadcast studio called DC2. The DC2 network is capable of 585 handling 46 Tbps of throughput with 60,000 simultaneous signals. 586 Inside the facility are 1,100 miles of fiber feeding four audio 587 control rooms. (See details at [ESPN_DC2] ). 589 In designing DC2 they replaced as much point-to-point technology as 590 they possibly could with packet-based technology. They constructed 591 seven individual studios using layer 2 LANS (using IEEE 802.1 AVB) 592 that were entirely effective at routing audio within the LANs, and 593 they were very happy with the results, however to interconnect these 594 layer 2 LAN islands together they ended up using dedicated links 595 because there is no standards-based routing solution available. 597 This is the kind of motivation we have to develop these standards 598 because customers are ready and able to use them. 600 3. Electrical Utilities 602 3.1. Use Case Description 604 Many systems that an electrical utility deploys today rely on high 605 availability and deterministic behavior of the underlying networks. 606 Here we present use cases in Transmission, Generation and 607 Distribution, including key timing and reliability metrics. We also 608 discuss security issues and industry trends which affect the 609 architecture of next generation utility networks 611 3.1.1. Transmission Use Cases 613 3.1.1.1. Protection 615 Protection means not only the protection of human operators but also 616 the protection of the electrical equipment and the preservation of 617 the stability and frequency of the grid. If a fault occurs in the 618 transmission or distribution of electricity then severe damage can 619 occur to human operators, electrical equipment and the grid itself, 620 leading to blackouts. 622 Communication links in conjunction with protection relays are used to 623 selectively isolate faults on high voltage lines, transformers, 624 reactors and other important electrical equipment. The role of the 625 teleprotection system is to selectively disconnect a faulty part by 626 transferring command signals within the shortest possible time. 628 3.1.1.1.1. Key Criteria 630 The key criteria for measuring teleprotection performance are command 631 transmission time, dependability and security. These criteria are 632 defined by the IEC standard 60834 as follows: 634 o Transmission time (Speed): The time between the moment where state 635 changes at the transmitter input and the moment of the 636 corresponding change at the receiver output, including propagation 637 delay. Overall operating time for a teleprotection system 638 includes the time for initiating the command at the transmitting 639 end, the propagation delay over the network (including equipments) 640 and the selection and decision time at the receiving end, 641 including any additional delay due to a noisy environment. 643 o Dependability: The ability to issue and receive valid commands in 644 the presence of interference and/or noise, by minimizing the 645 probability of missing command (PMC). Dependability targets are 646 typically set for a specific bit error rate (BER) level. 648 o Security: The ability to prevent false tripping due to a noisy 649 environment, by minimizing the probability of unwanted commands 650 (PUC). Security targets are also set for a specific bit error 651 rate (BER) level. 653 Additional elements of the the teleprotection system that impact its 654 performance include: 656 o Network bandwidth 658 o Failure recovery capacity (aka resiliency) 660 3.1.1.1.2. Fault Detection and Clearance Timing 662 Most power line equipment can tolerate short circuits or faults for 663 up to approximately five power cycles before sustaining irreversible 664 damage or affecting other segments in the network. This translates 665 to total fault clearance time of 100ms. As a safety precaution, 666 however, actual operation time of protection systems is limited to 667 70- 80 percent of this period, including fault recognition time, 668 command transmission time and line breaker switching time. 670 Some system components, such as large electromechanical switches, 671 require particularly long time to operate and take up the majority of 672 the total clearance time, leaving only a 10ms window for the 673 telecommunications part of the protection scheme, independent of the 674 distance to travel. Given the sensitivity of the issue, new networks 675 impose requirements that are even more stringent: IEC standard 61850 676 limits the transfer time for protection messages to 1/4 - 1/2 cycle 677 or 4 - 8ms (for 60Hz lines) for the most critical messages. 679 3.1.1.1.3. Symmetric Channel Delay 681 Teleprotection channels which are differential must be synchronous, 682 which means that any delays on the transmit and receive paths must 683 match each other. Teleprotection systems ideally support zero 684 asymmetric delay; typical legacy relays can tolerate delay 685 discrepancies of up to 750us. 687 Some tools available for lowering delay variation below this 688 threshold are: 690 o For legacy systems using Time Division Multiplexing (TDM), jitter 691 buffers at the multiplexers on each end of the line can be used to 692 offset delay variation by queuing sent and received packets. The 693 length of the queues must balance the need to regulate the rate of 694 transmission with the need to limit overall delay, as larger 695 buffers result in increased latency. 697 o For jitter-prone IP packet networks, traffic management tools can 698 ensure that the teleprotection signals receive the highest 699 transmission priority to minimize jitter. 701 o Standard packet-based synchronization technologies, such as 702 1588-2008 Precision Time Protocol (PTP) and Synchronous Ethernet 703 (Sync-E), can help keep networks stable by maintaining a highly 704 accurate clock source on the various network devices. 706 3.1.1.1.4. Teleprotection Network Requirements (IEC 61850) 708 The following table captures the main network metrics as based on the 709 IEC 61850 standard. 711 +-----------------------------+-------------------------------------+ 712 | Teleprotection Requirement | Attribute | 713 +-----------------------------+-------------------------------------+ 714 | One way maximum delay | 4-10 ms | 715 | Asymetric delay required | Yes | 716 | Maximum jitter | less than 250 us (750 us for legacy | 717 | | IED) | 718 | Topology | Point to point, point to Multi- | 719 | | point | 720 | Availability | 99.9999 | 721 | precise timing required | Yes | 722 | Recovery time on node | less than 50ms - hitless | 723 | failure | | 724 | performance management | Yes, Mandatory | 725 | Redundancy | Yes | 726 | Packet loss | 0.1% to 1% | 727 +-----------------------------+-------------------------------------+ 729 Table 1: Teleprotection network requirements 731 3.1.1.1.5. Inter-Trip Protection scheme 733 "Inter-tripping" is the signal-controlled tripping of a circuit 734 breaker to complete the isolation of a circuit or piece of apparatus 735 in concert with the tripping of other circuit breakers. 737 +--------------------------------+----------------------------------+ 738 | Inter-Trip protection | Attribute | 739 | Requirement | | 740 +--------------------------------+----------------------------------+ 741 | One way maximum delay | 5 ms | 742 | Asymetric delay required | No | 743 | Maximum jitter | Not critical | 744 | Topology | Point to point, point to Multi- | 745 | | point | 746 | Bandwidth | 64 Kbps | 747 | Availability | 99.9999 | 748 | precise timing required | Yes | 749 | Recovery time on node failure | less than 50ms - hitless | 750 | performance management | Yes, Mandatory | 751 | Redundancy | Yes | 752 | Packet loss | 0.1% | 753 +--------------------------------+----------------------------------+ 755 Table 2: Inter-Trip protection network requirements 757 3.1.1.1.6. Current Differential Protection Scheme 759 Current differential protection is commonly used for line protection, 760 and is typical for protecting parallel circuits. At both end of the 761 lines the current is measured by the differential relays, and both 762 relays will trip the circuit breaker if the current going into the 763 line does not equal the current going out of the line. This type of 764 protection scheme assumes some form of communications being present 765 between the relays at both end of the line, to allow both relays to 766 compare measured current values. Line differential protection 767 schemes assume a very low telecommunications delay between both 768 relays, often as low as 5ms. Moreover, as those systems are often 769 not time-synchronized, they also assume symmetric telecommunications 770 paths with constant delay, which allows comparing current measurement 771 values taken at the exact same time. 773 +----------------------------------+--------------------------------+ 774 | Current Differential protection | Attribute | 775 | Requirement | | 776 +----------------------------------+--------------------------------+ 777 | One way maximum delay | 5 ms | 778 | Asymetric delay Required | Yes | 779 | Maximum jitter | less than 250 us (750us for | 780 | | legacy IED) | 781 | Topology | Point to point, point to | 782 | | Multi-point | 783 | Bandwidth | 64 Kbps | 784 | Availability | 99.9999 | 785 | precise timing required | Yes | 786 | Recovery time on node failure | less than 50ms - hitless | 787 | performance management | Yes, Mandatory | 788 | Redundancy | Yes | 789 | Packet loss | 0.1% | 790 +----------------------------------+--------------------------------+ 792 Table 3: Current Differential Protection metrics 794 3.1.1.1.7. Distance Protection Scheme 796 Distance (Impedance Relay) protection scheme is based on voltage and 797 current measurements. The network metrics are similar (but not 798 identical to) Current Differential protection. 800 +-------------------------------+-----------------------------------+ 801 | Distance protection | Attribute | 802 | Requirement | | 803 +-------------------------------+-----------------------------------+ 804 | One way maximum delay | 5 ms | 805 | Asymetric delay Required | No | 806 | Maximum jitter | Not critical | 807 | Topology | Point to point, point to Multi- | 808 | | point | 809 | Bandwidth | 64 Kbps | 810 | Availability | 99.9999 | 811 | precise timing required | Yes | 812 | Recovery time on node failure | less than 50ms - hitless | 813 | performance management | Yes, Mandatory | 814 | Redundancy | Yes | 815 | Packet loss | 0.1% | 816 +-------------------------------+-----------------------------------+ 818 Table 4: Distance Protection requirements 820 3.1.1.1.8. Inter-Substation Protection Signaling 822 This use case describes the exchange of Sampled Value and/or GOOSE 823 (Generic Object Oriented Substation Events) message between 824 Intelligent Electronic Devices (IED) in two substations for 825 protection and tripping coordination. The two IEDs are in a master- 826 slave mode. 828 The Current Transformer or Voltage Transformer (CT/VT) in one 829 substation sends the sampled analog voltage or current value to the 830 Merging Unit (MU) over hard wire. The MU sends the time-synchronized 831 61850-9-2 sampled values to the slave IED. The slave IED forwards 832 the information to the Master IED in the other substation. The 833 master IED makes the determination (for example based on sampled 834 value differentials) to send a trip command to the originating IED. 835 Once the slave IED/Relay receives the GOOSE trip for breaker 836 tripping, it opens the breaker. It then sends a confirmation message 837 back to the master. All data exchanges between IEDs are either 838 through Sampled Value and/or GOOSE messages. 840 +----------------------------------+--------------------------------+ 841 | Inter-Substation protection | Attribute | 842 | Requirement | | 843 +----------------------------------+--------------------------------+ 844 | One way maximum delay | 5 ms | 845 | Asymetric delay Required | No | 846 | Maximum jitter | Not critical | 847 | Topology | Point to point, point to | 848 | | Multi-point | 849 | Bandwidth | 64 Kbps | 850 | Availability | 99.9999 | 851 | precise timing required | Yes | 852 | Recovery time on node failure | less than 50ms - hitless | 853 | performance management | Yes, Mandatory | 854 | Redundancy | Yes | 855 | Packet loss | 1% | 856 +----------------------------------+--------------------------------+ 858 Table 5: Inter-Substation Protection requirements 860 3.1.1.2. Intra-Substation Process Bus Communications 862 This use case describes the data flow from the CT/VT to the IEDs in 863 the substation via the MU. The CT/VT in the substation send the 864 sampled value (analog voltage or current) to the MU over hard wire. 865 The MU sends the time-synchronized 61850-9-2 sampled values to the 866 IEDs in the substation in GOOSE message format. The GPS Master Clock 867 can send 1PPS or IRIG-B format to the MU through a serial port or 868 IEEE 1588 protocol via a network. Process bus communication using 869 61850 simplifies connectivity within the substation and removes the 870 requirement for multiple serial connections and removes the slow 871 serial bus architectures that are typically used. This also ensures 872 increased flexibility and increased speed with the use of multicast 873 messaging between multiple devices. 875 +----------------------------------+--------------------------------+ 876 | Intra-Substation protection | Attribute | 877 | Requirement | | 878 +----------------------------------+--------------------------------+ 879 | One way maximum delay | 5 ms | 880 | Asymetric delay Required | No | 881 | Maximum jitter | Not critical | 882 | Topology | Point to point, point to | 883 | | Multi-point | 884 | Bandwidth | 64 Kbps | 885 | Availability | 99.9999 | 886 | precise timing required | Yes | 887 | Recovery time on Node failure | less than 50ms - hitless | 888 | performance management | Yes, Mandatory | 889 | Redundancy | Yes - No | 890 | Packet loss | 0.1% | 891 +----------------------------------+--------------------------------+ 893 Table 6: Intra-Substation Protection requirements 895 3.1.1.3. Wide Area Monitoring and Control Systems 897 The application of synchrophasor measurement data from Phasor 898 Measurement Units (PMU) to Wide Area Monitoring and Control Systems 899 promises to provide important new capabilities for improving system 900 stability. Access to PMU data enables more timely situational 901 awareness over larger portions of the grid than what has been 902 possible historically with normal SCADA (Supervisory Control and Data 903 Acquisition) data. Handling the volume and real-time nature of 904 synchrophasor data presents unique challenges for existing 905 application architectures. Wide Area management System (WAMS) makes 906 it possible for the condition of the bulk power system to be observed 907 and understood in real-time so that protective, preventative, or 908 corrective action can be taken. Because of the very high sampling 909 rate of measurements and the strict requirement for time 910 synchronization of the samples, WAMS has stringent telecommunications 911 requirements in an IP network that are captured in the following 912 table: 914 +----------------------+--------------------------------------------+ 915 | WAMS Requirement | Attribute | 916 +----------------------+--------------------------------------------+ 917 | One way maximum | 50 ms | 918 | delay | | 919 | Asymetric delay | No | 920 | Required | | 921 | Maximum jitter | Not critical | 922 | Topology | Point to point, point to Multi-point, | 923 | | Multi-point to Multi-point | 924 | Bandwidth | 100 Kbps | 925 | Availability | 99.9999 | 926 | precise timing | Yes | 927 | required | | 928 | Recovery time on | less than 50ms - hitless | 929 | Node failure | | 930 | performance | Yes, Mandatory | 931 | management | | 932 | Redundancy | Yes | 933 | Packet loss | 1% | 934 +----------------------+--------------------------------------------+ 936 Table 7: WAMS Special Communication Requirements 938 3.1.1.4. IEC 61850 WAN engineering guidelines requirement 939 classification 941 The IEC (International Electrotechnical Commission) has recently 942 published a Technical Report which offers guidelines on how to define 943 and deploy Wide Area Networks for the interconnections of electric 944 substations, generation plants and SCADA operation centers. The IEC 945 61850-90-12 is providing a classification of WAN communication 946 requirements into 4 classes. Table 8 summarizes these requirements: 948 +----------------+------------+------------+------------+-----------+ 949 | WAN | Class WA | Class WB | Class WC | Class WD | 950 | Requirement | | | | | 951 +----------------+------------+------------+------------+-----------+ 952 | Application | EHV (Extra | HV (High | MV (Medium | General | 953 | field | High | Voltage) | Voltage) | purpose | 954 | | Voltage) | | | | 955 | Latency | 5 ms | 10 ms | 100 ms | > 100 ms | 956 | Jitter | 10 us | 100 us | 1 ms | 10 ms | 957 | Latency | 100 us | 1 ms | 10 ms | 100 ms | 958 | Asymetry | | | | | 959 | Time Accuracy | 1 us | 10 us | 100 us | 10 to 100 | 960 | | | | | ms | 961 | Bit Error rate | 10-7 to | 10-5 to | 10-3 | | 962 | | 10-6 | 10-4 | | | 963 | Unavailability | 10-7 to | 10-5 to | 10-3 | | 964 | | 10-6 | 10-4 | | | 965 | Recovery delay | Zero | 50 ms | 5 s | 50 s | 966 | Cyber security | extremely | High | Medium | Medium | 967 | | high | | | | 968 +----------------+------------+------------+------------+-----------+ 970 Table 8: 61850-90-12 Communication Requirements; Courtesy of IEC 972 3.1.2. Generation Use Case 974 The electrical power generation frequency should be maintained within 975 a very narrow band. Deviations from the acceptable frequency range 976 are detected and the required signals are sent to the power plants 977 for frequency regulation. 979 Automatic generation control (AGC) is a system for adjusting the 980 power output of generators at different power plants, in response to 981 changes in the load. 983 +---------------------------------------------------+---------------+ 984 | FCAG (Frequency Control Automatic Generation) | Attribute | 985 | Requirement | | 986 +---------------------------------------------------+---------------+ 987 | One way maximum delay | 500 ms | 988 | Asymetric delay Required | No | 989 | Maximum jitter | Not critical | 990 | Topology | Point to | 991 | | point | 992 | Bandwidth | 20 Kbps | 993 | Availability | 99.999 | 994 | precise timing required | Yes | 995 | Recovery time on Node failure | N/A | 996 | performance management | Yes, | 997 | | Mandatory | 998 | Redundancy | Yes | 999 | Packet loss | 1% | 1000 +---------------------------------------------------+---------------+ 1002 Table 9: FCAG Communication Requirements 1004 3.1.3. Distribution use case 1006 3.1.3.1. Fault Location Isolation and Service Restoration (FLISR) 1008 Fault Location, Isolation, and Service Restoration (FLISR) refers to 1009 the ability to automatically locate the fault, isolate the fault, and 1010 restore service in the distribution network. This will likely be the 1011 first widespread application of distributed intelligence in the grid. 1013 Static power switch status (open/closed) in the network dictates the 1014 power flow to secondary substations. Reconfiguring the network in 1015 the event of a fault is typically done manually on site to energize/ 1016 de-energize alternate paths. Automating the operation of substation 1017 switchgear allows the flow of power to be altered automatically under 1018 fault conditions. 1020 FLISR can be managed centrally from a Distribution Management System 1021 (DMS) or executed locally through distributed control via intelligent 1022 switches and fault sensors. 1024 +----------------------+--------------------------------------------+ 1025 | FLISR Requirement | Attribute | 1026 +----------------------+--------------------------------------------+ 1027 | One way maximum | 80 ms | 1028 | delay | | 1029 | Asymetric delay | No | 1030 | Required | | 1031 | Maximum jitter | 40 ms | 1032 | Topology | Point to point, point to Multi-point, | 1033 | | Multi-point to Multi-point | 1034 | Bandwidth | 64 Kbps | 1035 | Availability | 99.9999 | 1036 | precise timing | Yes | 1037 | required | | 1038 | Recovery time on | Depends on customer impact | 1039 | Node failure | | 1040 | performance | Yes, Mandatory | 1041 | management | | 1042 | Redundancy | Yes | 1043 | Packet loss | 0.1% | 1044 +----------------------+--------------------------------------------+ 1046 Table 10: FLISR Communication Requirements 1048 3.2. Electrical Utilities Today 1050 Many utilities still rely on complex environments formed of multiple 1051 application-specific proprietary networks, including TDM networks. 1053 In this kind of environment there is no mixing of OT and IT 1054 applications on the same network, and information is siloed between 1055 operational areas. 1057 Specific calibration of the full chain is required, which is costly. 1059 This kind of environment prevents utility operations from realizing 1060 the operational efficiency benefits, visibility, and functional 1061 integration of operational information across grid applications and 1062 data networks. 1064 In addition, there are many security-related issues as discussed in 1065 the following section. 1067 3.2.1. Security Current Practices and Limitations 1069 Grid monitoring and control devices are already targets for cyber 1070 attacks, and legacy telecommunications protocols have many intrinsic 1071 network-related vulnerabilities. For example, DNP3, Modbus, 1072 PROFIBUS/PROFINET, and other protocols are designed around a common 1073 paradigm of request and respond. Each protocol is designed for a 1074 master device such as an HMI (Human Machine Interface) system to send 1075 commands to subordinate slave devices to retrieve data (reading 1076 inputs) or control (writing to outputs). Because many of these 1077 protocols lack authentication, encryption, or other basic security 1078 measures, they are prone to network-based attacks, allowing a 1079 malicious actor or attacker to utilize the request-and-respond system 1080 as a mechanism for command-and-control like functionality. Specific 1081 security concerns common to most industrial control, including 1082 utility telecommunication protocols include the following: 1084 o Network or transport errors (e.g. malformed packets or excessive 1085 latency) can cause protocol failure. 1087 o Protocol commands may be available that are capable of forcing 1088 slave devices into inoperable states, including powering-off 1089 devices, forcing them into a listen-only state, disabling 1090 alarming. 1092 o Protocol commands may be available that are capable of restarting 1093 communications and otherwise interrupting processes. 1095 o Protocol commands may be available that are capable of clearing, 1096 erasing, or resetting diagnostic information such as counters and 1097 diagnostic registers. 1099 o Protocol commands may be available that are capable of requesting 1100 sensitive information about the controllers, their configurations, 1101 or other need-to-know information. 1103 o Most protocols are application layer protocols transported over 1104 TCP; therefore it is easy to transport commands over non-standard 1105 ports or inject commands into authorized traffic flows. 1107 o Protocol commands may be available that are capable of 1108 broadcasting messages to many devices at once (i.e. a potential 1109 DoS). 1111 o Protocol commands may be available to query the device network to 1112 obtain defined points and their values (i.e. a configuration 1113 scan). 1115 o Protocol commands may be available that will list all available 1116 function codes (i.e. a function scan). 1118 These inherent vulnerabilities, along with increasing connectivity 1119 between IT an OT networks, make network-based attacks very feasible. 1121 Simple injection of malicious protocol commands provides control over 1122 the target process. Altering legitimate protocol traffic can also 1123 alter information about a process and disrupt the legitimate controls 1124 that are in place over that process. A man-in-the-middle attack 1125 could provide both control over a process and misrepresentation of 1126 data back to operator consoles. 1128 3.3. Electrical Utilities Future 1130 The business and technology trends that are sweeping the utility 1131 industry will drastically transform the utility business from the way 1132 it has been for many decades. At the core of many of these changes 1133 is a drive to modernize the electrical grid with an integrated 1134 telecommunications infrastructure. However, interoperability 1135 concerns, legacy networks, disparate tools, and stringent security 1136 requirements all add complexity to the grid transformation. Given 1137 the range and diversity of the requirements that should be addressed 1138 by the next generation telecommunications infrastructure, utilities 1139 need to adopt a holistic architectural approach to integrate the 1140 electrical grid with digital telecommunications across the entire 1141 power delivery chain. 1143 The key to modernizing grid telecommunications is to provide a 1144 common, adaptable, multi-service network infrastructure for the 1145 entire utility organization. Such a network serves as the platform 1146 for current capabilities while enabling future expansion of the 1147 network to accommodate new applications and services. 1149 To meet this diverse set of requirements, both today and in the 1150 future, the next generation utility telecommunnications network will 1151 be based on open-standards-based IP architecture. An end-to-end IP 1152 architecture takes advantage of nearly three decades of IP technology 1153 development, facilitating interoperability across disparate networks 1154 and devices, as it has been already demonstrated in many mission- 1155 critical and highly secure networks. 1157 IPv6 is seen as a future telecommunications technology for the Smart 1158 Grid; the IEC (International Electrotechnical Commission) and 1159 different National Committees have mandated a specific adhoc group 1160 (AHG8) to define the migration strategy to IPv6 for all the IEC TC57 1161 power automation standards. 1163 3.3.1. Migration to Packet-Switched Network 1165 Throughout the world, utilities are increasingly planning for a 1166 future based on smart grid applications requiring advanced 1167 telecommunications systems. Many of these applications utilize 1168 packet connectivity for communicating information and control signals 1169 across the utility's Wide Area Network (WAN), made possible by 1170 technologies such as multiprotocol label switching (MPLS). The data 1171 that traverses the utility WAN includes: 1173 o Grid monitoring, control, and protection data 1175 o Non-control grid data (e.g. asset data for condition-based 1176 monitoring) 1178 o Physical safety and security data (e.g. voice and video) 1180 o Remote worker access to corporate applications (voice, maps, 1181 schematics, etc.) 1183 o Field area network backhaul for smart metering, and distribution 1184 grid management 1186 o Enterprise traffic (email, collaboration tools, business 1187 applications) 1189 WANs support this wide variety of traffic to and from substations, 1190 the transmission and distribution grid, generation sites, between 1191 control centers, and between work locations and data centers. To 1192 maintain this rapidly expanding set of applications, many utilities 1193 are taking steps to evolve present time-division multiplexing (TDM) 1194 based and frame relay infrastructures to packet systems. Packet- 1195 based networks are designed to provide greater functionalities and 1196 higher levels of service for applications, while continuing to 1197 deliver reliability and deterministic (real-time) traffic support. 1199 3.3.2. Telecommunications Trends 1201 These general telecommunications topics are in addition to the use 1202 cases that have been addressed so far. These include both current 1203 and future telecommunications related topics that should be factored 1204 into the network architecture and design. 1206 3.3.2.1. General Telecommunications Requirements 1208 o IP Connectivity everywhere 1210 o Monitoring services everywhere and from different remote centers 1212 o Move services to a virtual data center 1214 o Unify access to applications / information from the corporate 1215 network 1217 o Unify services 1219 o Unified Communications Solutions 1221 o Mix of fiber and microwave technologies - obsolescence of SONET/ 1222 SDH or TDM 1224 o Standardize grid telecommunications protocol to opened standard to 1225 ensure interoperability 1227 o Reliable Telecommunications for Transmission and Distribution 1228 Substations 1230 o IEEE 1588 time synchronization Client / Server Capabilities 1232 o Integration of Multicast Design 1234 o QoS Requirements Mapping 1236 o Enable Future Network Expansion 1238 o Substation Network Resilience 1240 o Fast Convergence Design 1242 o Scalable Headend Design 1244 o Define Service Level Agreements (SLA) and Enable SLA Monitoring 1246 o Integration of 3G/4G Technologies and future technologies 1248 o Ethernet Connectivity for Station Bus Architecture 1250 o Ethernet Connectivity for Process Bus Architecture 1252 o Protection, teleprotection and PMU (Phaser Measurement Unit) on IP 1254 3.3.2.2. Specific Network topologies of Smart Grid Applications 1256 Utilities often have very large private telecommunications networks. 1257 It covers an entire territory / country. The main purpose of the 1258 network, until now, has been to support transmission network 1259 monitoring, control, and automation, remote control of generation 1260 sites, and providing FCAPS (Fault, Configuration, Accounting, 1261 Performance, Security) services from centralized network operation 1262 centers. 1264 Going forward, one network will support operation and maintenance of 1265 electrical networks (generation, transmission, and distribution), 1266 voice and data services for ten of thousands of employees and for 1267 exchange with neighboring interconnections, and administrative 1268 services. To meet those requirements, utility may deploy several 1269 physical networks leveraging different technologies across the 1270 country: an optical network and a microwave network for instance. 1271 Each protection and automatism system between two points has two 1272 telecommunications circuits, one on each network. Path diversity 1273 between two substations is key. Regardless of the event type 1274 (hurricane, ice storm, etc.), one path shall stay available so the 1275 system can still operate. 1277 In the optical network, signals are transmitted over more than tens 1278 of thousands of circuits using fiber optic links, microwave and 1279 telephone cables. This network is the nervous system of the 1280 utility's power transmission operations. The optical network 1281 represents ten of thousands of km of cable deployed along the power 1282 lines, with individual runs as long as 280 km. 1284 3.3.2.3. Precision Time Protocol 1286 Some utilities do not use GPS clocks in generation substations. One 1287 of the main reasons is that some of the generation plants are 30 to 1288 50 meters deep under ground and the GPS signal can be weak and 1289 unreliable. Instead, atomic clocks are used. Clocks are 1290 synchronized amongst each other. Rubidium clocks provide clock and 1291 1ms timestamps for IRIG-B. 1293 Some companies plan to transition to the Precision Time Protocol 1294 (PTP, [IEEE1588]), distributing the synchronization signal over the 1295 IP/MPLS network. PTP provides a mechanism for synchronizing the 1296 clocks of participating nodes to a high degree of accuracy and 1297 precision. 1299 PTP operates based on the following assumptions: 1301 It is assumed that the network eliminates cyclic forwarding of PTP 1302 messages within each communication path (e.g. by using a spanning 1303 tree protocol). 1305 PTP is tolerant of an occasional missed message, duplicated 1306 message, or message that arrived out of order. However, PTP 1307 assumes that such impairments are relatively rare. 1309 PTP was designed assuming a multicast communication model, however 1310 PTP also supports a unicast communication model as long as the 1311 behavior of the protocol is preserved. 1313 Like all message-based time transfer protocols, PTP time accuracy 1314 is degraded by delay asymmetry in the paths taken by event 1315 messages. Asymmetry is not detectable by PTP, however, if such 1316 delays are known a priori, PTP can correct for asymmetry. 1318 IEC 61850 will recommend the use of the IEEE PTP 1588 Utility Profile 1319 (as defined in [IEC62439-3:2012] Annex B) which offers the support of 1320 redundant attachment of clocks to Parallel Redundancy Protcol (PRP) 1321 and High-availability Seamless Redundancy (HSR) networks. 1323 3.3.3. Security Trends in Utility Networks 1325 Although advanced telecommunications networks can assist in 1326 transforming the energy industry by playing a critical role in 1327 maintaining high levels of reliability, performance, and 1328 manageability, they also introduce the need for an integrated 1329 security infrastructure. Many of the technologies being deployed to 1330 support smart grid projects such as smart meters and sensors can 1331 increase the vulnerability of the grid to attack. Top security 1332 concerns for utilities migrating to an intelligent smart grid 1333 telecommunications platform center on the following trends: 1335 o Integration of distributed energy resources 1337 o Proliferation of digital devices to enable management, automation, 1338 protection, and control 1340 o Regulatory mandates to comply with standards for critical 1341 infrastructure protection 1343 o Migration to new systems for outage management, distribution 1344 automation, condition-based maintenance, load forecasting, and 1345 smart metering 1347 o Demand for new levels of customer service and energy management 1349 This development of a diverse set of networks to support the 1350 integration of microgrids, open-access energy competition, and the 1351 use of network-controlled devices is driving the need for a converged 1352 security infrastructure for all participants in the smart grid, 1353 including utilities, energy service providers, large commercial and 1354 industrial, as well as residential customers. Securing the assets of 1355 electric power delivery systems (from the control center to the 1356 substation, to the feeders and down to customer meters) requires an 1357 end-to-end security infrastructure that protects the myriad of 1358 telecommunications assets used to operate, monitor, and control power 1359 flow and measurement. 1361 "Cyber security" refers to all the security issues in automation and 1362 telecommunications that affect any functions related to the operation 1363 of the electric power systems. Specifically, it involves the 1364 concepts of: 1366 o Integrity : data cannot be altered undetectably 1368 o Authenticity : the telecommunications parties involved must be 1369 validated as genuine 1371 o Authorization : only requests and commands from the authorized 1372 users can be accepted by the system 1374 o Confidentiality : data must not be accessible to any 1375 unauthenticated users 1377 When designing and deploying new smart grid devices and 1378 telecommunications systems, it is imperative to understand the 1379 various impacts of these new components under a variety of attack 1380 situations on the power grid. Consequences of a cyber attack on the 1381 grid telecommunications network can be catastrophic. This is why 1382 security for smart grid is not just an ad hoc feature or product, 1383 it's a complete framework integrating both physical and Cyber 1384 security requirements and covering the entire smart grid networks 1385 from generation to distribution. Security has therefore become one 1386 of the main foundations of the utility telecom network architecture 1387 and must be considered at every layer with a defense-in-depth 1388 approach. Migrating to IP based protocols is key to address these 1389 challenges for two reasons: 1391 o IP enables a rich set of features and capabilities to enhance the 1392 security posture 1394 o IP is based on open standards, which allows interoperability 1395 between different vendors and products, driving down the costs 1396 associated with implementing security solutions in OT networks. 1398 Securing OT (Operation technology) telecommunications over packet- 1399 switched IP networks follow the same principles that are foundational 1400 for securing the IT infrastructure, i.e., consideration must be given 1401 to enforcing electronic access control for both person-to-machine and 1402 machine-to-machine communications, and providing the appropriate 1403 levels of data privacy, device and platform integrity, and threat 1404 detection and mitigation. 1406 3.4. Electrical Utilities Asks 1408 o Mixed L2 and L3 topologies 1410 o Deterministic behavior 1412 o Bounded latency and jitter 1414 o High availability, low recovery time 1416 o Redundancy, low packet loss 1418 o Precise timing 1420 o Centralized computing of deterministic paths 1422 o Distributed configuration may also be useful 1424 4. Building Automation Systems 1426 4.1. Use Case Description 1428 A Building Automation System (BAS) manages equipment and sensors in a 1429 building for improving residents' comfort, reducing energy 1430 consumption, and responding to failures and emergencies. For 1431 example, the BAS measures the temperature of a room using sensors and 1432 then controls the HVAC (heating, ventilating, and air conditioning) 1433 to maintain a set temperature and minimize energy consumption. 1435 A BAS primarily performs the following functions: 1437 o Periodically measures states of devices, for example humidity and 1438 illuminance of rooms, open/close state of doors, FAN speed, etc. 1440 o Stores the measured data. 1442 o Provides the measured data to BAS systems and operators. 1444 o Generates alarms for abnormal state of devices. 1446 o Controls devices (e.g. turn off room lights at 10:00 PM). 1448 4.2. Building Automation Systems Today 1449 4.2.1. BAS Architecture 1451 A typical BAS architecture of today is shown in Figure 1. 1453 +----------------------------+ 1454 | | 1455 | BMS HMI | 1456 | | | | 1457 | +----------------------+ | 1458 | | Management Network | | 1459 | +----------------------+ | 1460 | | | | 1461 | LC LC | 1462 | | | | 1463 | +----------------------+ | 1464 | | Field Network | | 1465 | +----------------------+ | 1466 | | | | | | 1467 | Dev Dev Dev Dev | 1468 | | 1469 +----------------------------+ 1471 BMS := Building Management Server 1472 HMI := Human Machine Interface 1473 LC := Local Controller 1475 Figure 1: BAS architecture 1477 There are typically two layers of network in a BAS. The upper one is 1478 called the Management Network and the lower one is called the Field 1479 Network. In management networks an IP-based communication protocol 1480 is used, while in field networks non-IP based communication protocols 1481 ("field protocols") are mainly used. Field networks have specific 1482 timing requirements, whereas management networks can be best-effort. 1484 A Human Machine Interface (HMI) is typically a desktop PC used by 1485 operators to monitor and display device states, send device control 1486 commands to Local Controllers (LCs), and configure building schedules 1487 (for example "turn off all room lights in the building at 10:00 PM"). 1489 A Building Management Server (BMS) performs the following operations. 1491 o Collect and store device states from LCs at regular intervals. 1493 o Send control values to LCs according to a building schedule. 1495 o Send an alarm signal to operators if it detects abnormal devices 1496 states. 1498 The BMS and HMI communicate with LCs via IP-based "management 1499 protocols" (see standards [bacnetip], [knx]). 1501 A LC is typically a Programmable Logic Controller (PLC) which is 1502 connected to several tens or hundreds of devices using "field 1503 protocols". An LC performs the following kinds of operations: 1505 o Measure device states and provide the information to BMS or HMI. 1507 o Send control values to devices, unilaterally or as part of a 1508 feedback control loop. 1510 There are many field protocols used today; some are standards-based 1511 and others are proprietary (see standards [lontalk], [modbus], 1512 [profibus] and [flnet]). The result is that BASs have multiple MAC/ 1513 PHY modules and interfaces. This makes BASs more expensive, slower 1514 to develop, and can result in "vendor lock-in" with multiple types of 1515 management applications. 1517 4.2.2. BAS Deployment Model 1519 An example BAS for medium or large buildings is shown in Figure 2. 1520 The physical layout spans multiple floors, and there is a monitoring 1521 room where the BAS management entities are located. Each floor will 1522 have one or more LCs depending upon the number of devices connected 1523 to the field network. 1525 +--------------------------------------------------+ 1526 | Floor 3 | 1527 | +----LC~~~~+~~~~~+~~~~~+ | 1528 | | | | | | 1529 | | Dev Dev Dev | 1530 | | | 1531 |--- | ------------------------------------------| 1532 | | Floor 2 | 1533 | +----LC~~~~+~~~~~+~~~~~+ Field Network | 1534 | | | | | | 1535 | | Dev Dev Dev | 1536 | | | 1537 |--- | ------------------------------------------| 1538 | | Floor 1 | 1539 | +----LC~~~~+~~~~~+~~~~~+ +-----------------| 1540 | | | | | | Monitoring Room | 1541 | | Dev Dev Dev | | 1542 | | | BMS HMI | 1543 | | Management Network | | | | 1544 | +--------------------------------+-----+ | 1545 | | | 1546 +--------------------------------------------------+ 1548 Figure 2: BAS Deployment model for Medium/Large Buildings 1550 Each LC is connected to the monitoring room via the Management 1551 network, and the management functions are performed within the 1552 building. In most cases, fast Ethernet (e.g. 100BASE-T) is used for 1553 the management network. Since the management network is non- 1554 realtime, use of Ethernet without quality of service is sufficient 1555 for today's deployment. 1557 In the field network a variety of physical interfaces such as RS232C 1558 and RS485 are used, which have specific timing requirements. Thus if 1559 a field network is to be replaced with an Ethernet or wireless 1560 network, such networks must support time-critical deterministic 1561 flows. 1563 In Figure 3, another deployment model is presented in which the 1564 management system is hosted remotely. This is becoming popular for 1565 small office and residential buildings in which a standalone 1566 monitoring system is not cost-effective. 1568 +---------------+ 1569 | Remote Center | 1570 | | 1571 | BMS HMI | 1572 +------------------------------------+ | | | | 1573 | Floor 2 | | +---+---+ | 1574 | +----LC~~~~+~~~~~+ Field Network| | | | 1575 | | | | | | Router | 1576 | | Dev Dev | +-------|-------+ 1577 | | | | 1578 |--- | ------------------------------| | 1579 | | Floor 1 | | 1580 | +----LC~~~~+~~~~~+ | | 1581 | | | | | | 1582 | | Dev Dev | | 1583 | | | | 1584 | | Management Network | WAN | 1585 | +------------------------Router-------------+ 1586 | | 1587 +------------------------------------+ 1589 Figure 3: Deployment model for Small Buildings 1591 Some interoperability is possible today in the Management Network, 1592 but not in today's field networks due to their non-IP-based design. 1594 4.2.3. Use Cases for Field Networks 1596 Below are use cases for Environmental Monitoring, Fire Detection, and 1597 Feedback Control, and their implications for field network 1598 performance. 1600 4.2.3.1. Environmental Monitoring 1602 The BMS polls each LC at a maximum measurement interval of 100ms (for 1603 example to draw a historical chart of 1 second granularity with a 10x 1604 sampling interval) and then performs the operations as specified by 1605 the operator. Each LC needs to measure each of its several hundred 1606 sensors once per measurement interval. Latency is not critical in 1607 this scenario as long as all sensor values are completed in the 1608 measurement interval. Availability is expected to be 99.999 %. 1610 4.2.3.2. Fire Detection 1612 On detection of a fire, the BMS must stop the HVAC, close the fire 1613 shutters, turn on the fire sprinklers, send an alarm, etc. There are 1614 typically ~10s of sensors per LC that BMS needs to manage. In this 1615 scenario the measurement interval is 10-50ms, the communication delay 1616 is 10ms, and the availability must be 99.9999 %. 1618 4.2.3.3. Feedback Control 1620 BAS systems utilize feedback control in various ways; the most time- 1621 critial is control of DC motors, which require a short feedback 1622 interval (1-5ms) with low communication delay (10ms) and jitter 1623 (1ms). The feedback interval depends on the characteristics of the 1624 device and a target quality of control value. There are typically 1625 ~10s of such devices per LC. 1627 Communication delay is expected to be less than 10 ms, jitter less 1628 than 1 sec while the availability must be 99.9999% . 1630 4.2.4. Security Considerations 1632 When BAS field networks were developed it was assumed that the field 1633 networks would always be physically isolated from external networks 1634 and therefore security was not a concern. In today's world many BASs 1635 are managed remotely and are thus connected to shared IP networks and 1636 so security is definitely a concern, yet security features are not 1637 available in the majority of BAS field network deployments . 1639 The management network, being an IP-based network, has the protocols 1640 available to enable network security, but in practice many BAS 1641 systems do not implement even the available security features such as 1642 device authentication or encryption for data in transit. 1644 4.3. BAS Future 1646 In the future we expect more fine-grained environmental monitoring 1647 and lower energy consumption, which will require more sensors and 1648 devices, thus requiring larger and more complex building networks. 1650 We expect building networks to be connected to or converged with 1651 other networks (Enterprise network, Home network, and Internet). 1653 Therefore better facilities for network management, control, 1654 reliability and security are critical in order to improve resident 1655 and operator convenience and comfort. For example the ability to 1656 monitor and control building devices via the internet would enable 1657 (for example) control of room lights or HVAC from a resident's 1658 desktop PC or phone application. 1660 4.4. BAS Asks 1662 The community would like to see an interoperable protocol 1663 specification that can satisfy the timing, security, availability and 1664 QoS constraints described above, such that the resulting converged 1665 network can replace the disparate field networks. Ideally this 1666 connectivity could extend to the open Internet. 1668 This would imply an architecture that can guarantee 1670 o Low communication delays (from <10ms to 100ms in a network of 1671 several hundred devices) 1673 o Low jitter (< 1 ms) 1675 o Tight feedback intervals (1ms - 10ms) 1677 o High network availability (up to 99.9999% ) 1679 o Availability of network data in disaster scenario 1681 o Authentication between management and field devices (both local 1682 and remote) 1684 o Integrity and data origin authentication of communication data 1685 between field and management devices 1687 o Confidentiality of data when communicated to a remote device 1689 5. Wireless for Industrial 1691 5.1. Use Case Description 1693 Wireless networks are useful for industrial applications, for example 1694 when portable, fast-moving or rotating objects are involved, and for 1695 the resource-constrained devices found in the Internet of Things 1696 (IoT). 1698 Such network-connected sensors, actuators, control loops (etc.) 1699 typically require that the underlying network support real-time 1700 quality of service (QoS), as well as specific classes of other 1701 network properties such as reliability, redundancy, and security. 1703 These networks may also contain very large numbers of devices, for 1704 example for factories, "big data" acquisition, and the IoT. Given 1705 the large numbers of devices installed, and the potential 1706 pervasiveness of the IoT, this is a huge and very cost-sensitive 1707 market. For example, a 1% cost reduction in some areas could save 1708 $100B 1710 5.1.1. Network Convergence using 6TiSCH 1712 Some wireless network technologies support real-time QoS, and are 1713 thus useful for these kinds of networks, but others do not. For 1714 example WiFi is pervasive but does not provide guaranteed timing or 1715 delivery of packets, and thus is not useful in this context. 1717 In this use case we focus on one specific wireless network technology 1718 which does provide the required deterministic QoS, which is "IPv6 1719 over the TSCH mode of IEEE 802.15.4e" (6TiSCH, where TSCH stands for 1720 "Time-Slotted Channel Hopping", see [I-D.ietf-6tisch-architecture], 1721 [IEEE802154], [IEEE802154e], and [RFC7554]). 1723 There are other deterministic wireless busses and networks available 1724 today, however they are imcompatible with each other, and 1725 incompatible with IP traffic (for example [ISA100], [WirelessHART]). 1727 Thus the primary goal of this use case is to apply 6TiSH as a 1728 converged IP- and standards-based wireless network for industrial 1729 applications, i.e. to replace multiple proprietary and/or 1730 incompatible wireless networking and wireless network management 1731 standards. 1733 5.1.2. Common Protocol Development for 6TiSCH 1735 Today there are a number of protocols required by 6TiSCH which are 1736 still in development, and a second intent of this use case is to 1737 highlight the ways in which these "missing" protocols share goals in 1738 common with DetNet. Thus it is possible that some of the protocol 1739 technology developed for DetNet will also be applicable to 6TiSCH. 1741 These protocol goals are identified here, along with their 1742 relationship to DetNet. It is likely that ultimately the resulting 1743 protocols will not be identical, but will share design principles 1744 which contribute to the eficiency of enabling both DetNet and 6TiSCH. 1746 One such commonality is that although at a different time scale, in 1747 both TSN [IEEE802.1TSNTG] and TSCH a packet crosses the network from 1748 node to node follows a precise schedule, as a train that leaves 1749 intermediate stations at precise times along its path. This kind of 1750 operation reduces collisions, saves energy, and enables engineering 1751 the network for deterministic properties. 1753 Another commonality is remote monitoring and scheduling management of 1754 a TSCH network by a Path Computation Element (PCE) and Network 1755 Management Entity (NME). The PCE/NME manage timeslots and device 1756 resources in a manner that minimizes the interaction with and the 1757 load placed on resource-constrained devices. For example, a tiny IoT 1758 device may have just enough buffers to store one or a few IPv6 1759 packets, and will have limited bandwidth between peers such that it 1760 can maintain only a small amount of peer information, and will not be 1761 able to store many packets waiting to be forwarded. It is 1762 advantageous then for it to only be required to carry out the 1763 specific behavior assigned to it by the PCE/NME (as opposed to 1764 maintaining its own IP stack, for example). 1766 6TiSCH depends on [PCE] and [I-D.finn-detnet-architecture], and we 1767 expect that DetNet will maintain consistency with [IEEE802.1TSNTG]. 1769 5.2. Wireless Industrial Today 1771 Today industrial wireless is accomplished using multiple 1772 deterministic wireless networks which are incompatible with each 1773 other and with IP traffic. 1775 6TiSCH is not yet fully specified, so it cannot be used in today's 1776 applications. 1778 5.3. Wireless Industrial Future 1780 5.3.1. Unified Wireless Network and Management 1782 We expect DetNet and 6TiSCH together to enable converged transport of 1783 deterministic and best-effort traffic flows between real-time 1784 industrial devices and wide area networks via IP routing. A high 1785 level view of a basic such network is shown in Figure 4. 1787 ---+-------- ............ ------------ 1788 | External Network | 1789 | +-----+ 1790 +-----+ | NME | 1791 | | LLN Border | | 1792 | | router +-----+ 1793 +-----+ 1794 o o o 1795 o o o o 1796 o o LLN o o o 1797 o o o o 1798 o 1800 Figure 4: Basic 6TiSCH Network 1802 Figure 5 shows a backbone router federating multiple synchronized 1803 6TiSCH subnets into a single subnet connected to the external 1804 network. 1806 ---+-------- ............ ------------ 1807 | External Network | 1808 | +-----+ 1809 | +-----+ | NME | 1810 +-----+ | +-----+ | | 1811 | | Router | | PCE | +-----+ 1812 | | +--| | 1813 +-----+ +-----+ 1814 | | 1815 | Subnet Backbone | 1816 +--------------------+------------------+ 1817 | | | 1818 +-----+ +-----+ +-----+ 1819 | | Backbone | | Backbone | | Backbone 1820 o | | router | | router | | router 1821 +-----+ +-----+ +-----+ 1822 o o o o o 1823 o o o o o o o o o o o 1824 o o o LLN o o o o 1825 o o o o o o o o o o o o 1827 Figure 5: Extended 6TiSCH Network 1829 The backbone router must ensure end-to-end deterministic behavior 1830 between the LLN and the backbone. We would like to see this 1831 accomplished in conformance with the work done in 1832 [I-D.finn-detnet-architecture] with respect to Layer-3 aspects of 1833 deterministic networks that span multiple Layer-2 domains. 1835 The PCE must compute a deterministic path end-to-end across the TSCH 1836 network and IEEE802.1 TSN Ethernet backbone, and DetNet protocols are 1837 expected to enable end-to-end deterministic forwarding. 1839 +-----+ 1840 | IoT | 1841 | G/W | 1842 +-----+ 1843 ^ <---- Elimination 1844 | | 1845 Track branch | | 1846 +-------+ +--------+ Subnet Backbone 1847 | | 1848 +--|--+ +--|--+ 1849 | | | Backbone | | | Backbone 1850 o | | | router | | | router 1851 +--/--+ +--|--+ 1852 o / o o---o----/ o 1853 o o---o--/ o o o o o 1854 o \ / o o LLN o 1855 o v <---- Replication 1856 o 1858 Figure 6: 6TiSCH Network with PRE 1860 5.3.1.1. PCE and 6TiSCH ARQ Retries 1862 6TiSCH uses the IEEE802.15.4 Automatic Repeat-reQuest (ARQ) mechanism 1863 to provide higher reliability of packet delivery. ARQ is related to 1864 packet replication and elimination because there are two independent 1865 paths for packets to arrive at the destination, and if an expected 1866 packed does not arrive on one path then it checks for the packet on 1867 the second path. 1869 Although to date this mechanism is only used by wireless networks, 1870 this may be a technique that would be appropriate for DetNet and so 1871 aspects of the enabling protocol could be co-developed. 1873 For example, in Figure 6, a Track is laid out from a field device in 1874 a 6TiSCH network to an IoT gateway that is located on a IEEE802.1 TSN 1875 backbone. 1877 The Replication function in the field device sends a copy of each 1878 packet over two different branches, and the PCE schedules each hop of 1879 both branches so that the two copies arrive in due time at the 1880 gateway. In case of a loss on one branch, hopefully the other copy 1881 of the packet still arrives within the allocated time. If two copies 1882 make it to the IoT gateway, the Elimination function in the gateway 1883 ignores the extra packet and presents only one copy to upper layers. 1885 At each 6TiSCH hop along the Track, the PCE may schedule more than 1886 one timeSlot for a packet, so as to support Layer-2 retries (ARQ). 1888 In current deployments, a TSCH Track does not necessarily support PRE 1889 but is systematically multi-path. This means that a Track is 1890 scheduled so as to ensure that each hop has at least two forwarding 1891 solutions, and the forwarding decision is to try the preferred one 1892 and use the other in case of Layer-2 transmission failure as detected 1893 by ARQ. 1895 5.3.2. Schedule Management by a PCE 1897 A common feature of 6TiSCH and DetNet is the action of a PCE to 1898 configure paths through the network. Specifically, what is needed is 1899 a protocol and data model that the PCE will use to get/set the 1900 relevant configuration from/to the devices, as well as perform 1901 operations on the devices. We expect that this protocol will be 1902 developed by DetNet with consideration for its reuse by 6TiSCH. The 1903 remainder of this section provides a bit more context from the 6TiSCH 1904 side. 1906 5.3.2.1. PCE Commands and 6TiSCH CoAP Requests 1908 The 6TiSCH device does not expect to place the request for bandwidth 1909 between itself and another device in the network. Rather, an 1910 operation control system invoked through a human interface specifies 1911 the required traffic specification and the end nodes (in terms of 1912 latency and reliability). Based on this information, the PCE must 1913 compute a path between the end nodes and provision the network with 1914 per-flow state that describes the per-hop operation for a given 1915 packet, the corresponding timeslots, and the flow identification that 1916 enables recognizing that a certain packet belongs to a certain path, 1917 etc. 1919 For a static configuration that serves a certain purpose for a long 1920 period of time, it is expected that a node will be provisioned in one 1921 shot with a full schedule, which incorporates the aggregation of its 1922 behavior for multiple paths. 6TiSCH expects that the programing of 1923 the schedule will be done over COAP as discussed in 1924 [I-D.ietf-6tisch-coap]. 1926 6TiSCH expects that the PCE commands will be issued directly as CoAP 1927 requests or be mapped back and forth into CoAP by a gateway function 1928 at the edge of the 6TiSCH network. For instance, it is possible that 1929 a mapping entity on the backbone transforms a non-CoAP protocol such 1930 as PCEP into the RESTful interfaces that the 6TiSCH devices support. 1931 This architecture will be refined to comply with DetNet 1932 [I-D.finn-detnet-architecture] when the work is formalized. Related 1933 information about 6TiSCH can be found at 1934 [I-D.ietf-6tisch-6top-interface] and RPL [RFC6550]. 1936 If it appears that a path through the network does not perform as 1937 expected, a protocol may be used to update the state in the devices, 1938 but in 6TiSCH that flow was not designed and no protocol was selected 1939 and it is expected that DetNet will determine the appropriate end-to- 1940 end protocols to be used in that case. 1942 A "slotFrame" is the base object that the PCE needs to manipulate to 1943 program a schedule into an LLN node ([I-D.ietf-6tisch-architecture]). 1945 The PCE should be able to read energy data from devices, and compute 1946 paths that will implement policies on how energy in devices is 1947 consumed, for instance to ensure that the spent energy does not 1948 exceeded the available energy over a period of time. 1950 6TiSCH devices can discover their neighbors over the radio using a 1951 mechanism such as beacons, but even though the neighbor information 1952 is available in the 6TiSCH interface data model, 6TiSCH does not 1953 describe a protocol to proactively push the neighborhood information 1954 to a PCE. DetNet should define this protocol, and it and should 1955 operate over CoAP. The protocol should be able to carry multiple 1956 metrics, in particular the same metrics as used for RPL operations 1957 [RFC6551] 1959 5.3.2.2. 6TiSCH IP Interface 1961 "6top" ([I-D.wang-6tisch-6top-sublayer]) is a logical link control 1962 sitting between the IP layer and the TSCH MAC layer which provides 1963 the link abstraction that is required for IP operations. The 6top 1964 data model and management interfaces are further discussed in 1965 [I-D.ietf-6tisch-6top-interface] and [I-D.ietf-6tisch-coap]. 1967 An IP packet that is sent along a 6TiSCH path uses the Differentiated 1968 Services Per-Hop-Behavior Group called Deterministic Forwarding, as 1969 described in [I-D.svshah-tsvwg-deterministic-forwarding]. 1971 5.3.3. 6TiSCH Security Considerations 1973 On top of the classical requirements for protection of control 1974 signaling, it must be noted that 6TiSCH networks operate on limited 1975 resources that can be depleted rapidly in a DoS attack on the system, 1976 for instance by placing a rogue device in the network, or by 1977 obtaining management control and setting up unexpected additional 1978 paths. 1980 5.4. Wireless Industrial Asks 1982 6TiSCH depends on DetNet to define: 1984 o Configuration (state) and operations for deterministic paths 1986 o End-to-end protocols for deterministic forwarding (tagging, IP) 1988 o Protocol for packet replication and elimination 1990 o Protocol for packet automatic retries (ARQ) (specific to wireless) 1992 6. Cellular Radio Use Cases 1994 6.1. Use Case Description 1996 This use case describes the application of deterministic networking 1997 in the context of cellular telecom transport networks. Important 1998 elements include time synchronization, clock distribution, and ways 1999 of establishing time-sensitive streams for both Layer-2 and Layer-3 2000 user plane traffic. 2002 6.1.1. Network Architecture 2004 Figure 7 illustrates a typical 3GPP-defined cellular network 2005 architecture, which includes "Fronthaul" and "Midhaul" network 2006 segments. The "Fronthaul" is the network connecting base stations 2007 (baseband processing units) to the remote radio heads (antennas). 2008 The "Midhaul" is the network inter-connecting base stations (or small 2009 cell sites). 2011 In Figure 7 "eNB" ("E-UTRAN Node B") is the hardware that is 2012 connected to the mobile phone network which communicates directly 2013 with mobile handsets ([TS36300]). 2015 Y (remote radio heads (antennas)) 2016 \ 2017 Y__ \.--. .--. +------+ 2018 \_( `. +---+ _(Back`. | 3GPP | 2019 Y------( Front )----|eNB|----( Haul )----| core | 2020 ( ` .Haul ) +---+ ( ` . ) ) | netw | 2021 /`--(___.-' \ `--(___.-' +------+ 2022 Y_/ / \.--. \ 2023 Y_/ _( Mid`. \ 2024 ( Haul ) \ 2025 ( ` . ) ) \ 2026 `--(___.-'\_____+---+ (small cell sites) 2027 \ |SCe|__Y 2028 +---+ +---+ 2029 Y__|eNB|__Y 2030 +---+ 2031 Y_/ \_Y ("local" radios) 2033 Figure 7: Generic 3GPP-based Cellular Network Architecture 2035 The available processing time for Fronthaul networking overhead is 2036 limited to the available time after the baseband processing of the 2037 radio frame has completed. For example in Long Term Evolution (LTE) 2038 radio, processing of a radio frame is allocated 3ms, but typically 2039 the processing completes much earlier (<400us) allowing the remaining 2040 time to be used by the Fronthaul network. This ultimately determines 2041 the distance the remote radio heads can be located from the base 2042 stations (200us equals roughly 40 km of optical fiber-based 2043 transport, thus round trip time is 2*200us = 400us). 2045 The remainder of the "maximum delay budget" is consumed by all nodes 2046 and buffering between the remote radio head and the baseband 2047 processing, plus the distance-incurred delay. 2049 The baseband processing time and the available "delay budget" for the 2050 fronthaul is likely to change in the forthcoming "5G" due to reduced 2051 radio round trip times and other architectural and service 2052 requirements [NGMN]. 2054 6.1.2. Time Synchronization Requirements 2056 Fronthaul time synchronization requirements are given by [TS25104], 2057 [TS36104], [TS36211], and [TS36133]. These can be summarized for the 2058 current 3GPP LTE-based networks as: 2060 Delay Accuracy: 2061 +-8ns (i.e. +-1/32 Tc, where Tc is the UMTS Chip time of 1/3.84 2062 MHz) resulting in a round trip accuracy of +-16ns. The value is 2063 this low to meet the 3GPP Timing Alignment Error (TAE) measurement 2064 requirements. 2066 Packet Delay Variation: 2067 Packet Delay Variation (PDV aka Jitter aka Timing Alignment Error) 2068 is problematic to Fronthaul networks and must be minimized. If 2069 the transport network cannot guarantee low enough PDV then 2070 additional buffering has to be introduced at the edges of the 2071 network to buffer out the jitter. Buffering is not desirable as 2072 it reduces the total available delay budget. 2074 * For multiple input multiple output (MIMO) or TX diversity 2075 transmissions, at each carrier frequency, TAE shall not exceed 2076 65 ns (i.e. 1/4 Tc). 2078 * For intra-band contiguous carrier aggregation, with or without 2079 MIMO or TX diversity, TAE shall not exceed 130 ns (i.e. 1/2 2080 Tc). 2082 * For intra-band non-contiguous carrier aggregation, with or 2083 without MIMO or TX diversity, TAE shall not exceed 260 ns (i.e. 2084 one Tc). 2086 * For inter-band carrier aggregation, with or without MIMO or TX 2087 diversity, TAE shall not exceed 260 ns. 2089 Transport link contribution to radio frequency error: 2090 +-2 PPB. This value is considered to be "available" for the 2091 Fronthaul link out of the total 50 PPB budget reserved for the 2092 radio interface. Note: the reason that the transport link 2093 contributes to radio frequency error is as follows. The current 2094 way of doing Fronthaul is from the radio unit to remote radio head 2095 directly. The remote radio head is essentially a passive device 2096 (without buffering etc.) The transport drives the antenna 2097 directly by feeding it with samples and everything the transport 2098 adds will be introduced to radio as-is. So if the transport 2099 causes additional frequence error that shows immediately on the 2100 radio as well. 2102 The above listed time synchronization requirements are difficult to 2103 meet with point-to-point connected networks, and more difficult when 2104 the network includes multiple hops. It is expected that networks 2105 must include buffering at the ends of the connections as imposed by 2106 the jitter requirements, since trying to meet the jitter requirements 2107 in every intermediate node is likely to be too costly. However, 2108 every measure to reduce jitter and delay on the path makes it easier 2109 to meet the end-to-end requirements. 2111 In order to meet the timing requirements both senders and receivers 2112 must remain time synchronized, demanding very accurate clock 2113 distribution, for example support for IEEE 1588 transparent clocks in 2114 every intermediate node. 2116 In cellular networks from the LTE radio era onward, phase 2117 synchronization is needed in addition to frequency synchronization 2118 ([TS36300], [TS23401]). 2120 6.1.3. Time-Sensitive Stream Requirements 2122 In addition to the time synchronization requirements listed in 2123 Section Section 6.1.2 the Fronthaul networks assume practically 2124 error-free transport. The maximum bit error rate (BER) has been 2125 defined to be 10^-12. When packetized that would imply a packet 2126 error rate (PER) of 2.4*10^-9 (assuming ~300 bytes packets). 2127 Retransmitting lost packets and/or using forward error correction 2128 (FEC) to circumvent bit errors is practically impossible due to the 2129 additional delay incurred. Using redundant streams for better 2130 guarantees for delivery is also practically impossible in many cases 2131 due to high bandwidth requirements of Fronthaul networks. For 2132 instance, current uncompressed CPRI bandwidth expansion ratio is 2133 roughly 20:1 compared to the IP layer user payload it carries. 2134 Protection switching is also a candidate but current technologies for 2135 the path switch are too slow. We do not currently know of a better 2136 solution for this issue. 2138 Fronthaul links are assumed to be symmetric, and all Fronthaul 2139 streams (i.e. those carrying radio data) have equal priority and 2140 cannot delay or pre-empt each other. This implies that the network 2141 must guarantee that each time-sensitive flow meets their schedule. 2143 6.1.4. Security Considerations 2145 Establishing time-sensitive streams in the network entails reserving 2146 networking resources for long periods of time. It is important that 2147 these reservation requests be authenticated to prevent malicious 2148 reservation attempts from hostile nodes (or accidental 2149 misconfiguration). This is particularly important in the case where 2150 the reservation requests span administrative domains. Furthermore, 2151 the reservation information itself should be digitally signed to 2152 reduce the risk of a legitimate node pushing a stale or hostile 2153 configuration into another networking node. 2155 6.2. Cellular Radio Networks Today 2157 Today's Fronthaul networks typically consist of: 2159 o Dedicated point-to-point fiber connection is common 2161 o Proprietary protocols and framings 2163 o Custom equipment and no real networking 2165 Today's Midhaul and Backhaul networks typically consist of: 2167 o Mostly normal IP networks, MPLS-TP, etc. 2169 o Clock distribution and sync using 1588 and SyncE 2171 Telecommunication networks in the cellular domain are already heading 2172 towards transport networks where precise time synchronization support 2173 is one of the basic building blocks. While the transport networks 2174 themselves have practically transitioned to all-IP packet based 2175 networks to meet the bandwidth and cost requirements, highly accurate 2176 clock distribution has become a challenge. 2178 Transport networks in the cellular domain are typically based on Time 2179 Division Multiplexing (TDM-based) and provide frequency 2180 synchronization capabilities as a part of the transport media. 2181 Alternatively other technologies such as Global Positioning System 2182 (GPS) or Synchronous Ethernet (SyncE) are used [SyncE]. 2184 Both Ethernet and IP/MPLS [RFC3031] (and PseudoWires (PWE) [RFC3985] 2185 for legacy transport support) have become popular tools to build and 2186 manage new all-IP Radio Access Networks (RAN) 2187 [I-D.kh-spring-ip-ran-use-case]. Although various timing and 2188 synchronization optimizations have already been proposed and 2189 implemented including 1588 PTP enhancements 2190 [I-D.ietf-tictoc-1588overmpls][I-D.mirsky-mpls-residence-time], these 2191 solution are not necessarily sufficient for the forthcoming RAN 2192 architectures or guarantee the higher time-synchronization 2193 requirements [CPRI]. There are also existing solutions for the TDM 2194 over IP [RFC5087] [RFC4553] or Ethernet transports [RFC5086]. 2196 6.3. Cellular Radio Networks Future 2198 We would like to see the following in future Cellular Radio networks: 2200 o Unified standards-based transport protocols and standard 2201 networking equipment that can make use of underlying deterministic 2202 link-layer services 2204 o Unified and standards-based network management systems and 2205 protocols in all parts of the network (including Fronthaul) 2207 New radio access network deployment models and architectures may 2208 require time sensitive networking services with strict requirements 2209 on other parts of the network that previously were not considered to 2210 be packetized at all. The time and synchronization support are 2211 already topical for Backhaul and Midhaul packet networks [MEF], and 2212 becoming a real issue for Fronthaul networks. Specifically in the 2213 Fronthaul networks the timing and synchronization requirements can be 2214 extreme for packet based technologies, for example, on the order of 2215 sub +-20 ns packet delay variation (PDV) and frequency accuracy of 2216 +0.002 PPM [Fronthaul]. 2218 The actual transport protocols and/or solutions to establish required 2219 transport "circuits" (pinned-down paths) for Fronthaul traffic are 2220 still undefined. Those are likely to include (but are not limited 2221 to) solutions directly over Ethernet, over IP, and MPLS/PseudoWire 2222 transport. 2224 Even the current time-sensitive networking features may not be 2225 sufficient for Fronthaul traffic. Therefore, having specific 2226 profiles that take the requirements of Fronthaul into account is 2227 desirable [IEEE8021CM]. 2229 The really interesting and important existing work for time sensitive 2230 networking has been done for Ethernet [TSNTG], which specifies the 2231 use of IEEE 1588 time precision protocol (PTP) [IEEE1588] in the 2232 context of IEEE 802.1D and IEEE 802.1Q. While IEEE 802.1AS 2233 [IEEE8021AS] specifies a Layer-2 time synchronizing service other 2234 specification, such as IEEE 1722 [IEEE1722] specify Ethernet-based 2235 Layer-2 transport for time-sensitive streams. New promising work 2236 seeks to enable the transport of time-sensitive fronthaul streams in 2237 Ethernet bridged networks [IEEE8021CM]. Similarly to IEEE 1722 there 2238 is an ongoing standardization effort to define Layer-2 transport 2239 encapsulation format for transporting radio over Ethernet (RoE) in 2240 IEEE 1904.3 Task Force [IEEE19043]. 2242 All-IP RANs and various "haul" networks would benefit from time 2243 synchronization and time-sensitive transport services. Although 2244 Ethernet appears to be the unifying technology for the transport 2245 there is still a disconnect providing Layer-3 services. The protocol 2246 stack typically has a number of layers below the Ethernet Layer-2 2247 that shows up to the Layer-3 IP transport. It is not uncommon that 2248 on top of the lowest layer (optical) transport there is the first 2249 layer of Ethernet followed one or more layers of MPLS, PseudoWires 2250 and/or other tunneling protocols finally carrying the Ethernet layer 2251 visible to the user plane IP traffic. While there are existing 2252 technologies, especially in MPLS/PWE space, to establish circuits 2253 through the routed and switched networks, there is a lack of 2254 signaling the time synchronization and time-sensitive stream 2255 requirements/reservations for Layer-3 flows in a way that the entire 2256 transport stack is addressed and the Ethernet layers that needs to be 2257 configured are addressed. 2259 Furthermore, not all "user plane" traffic will be IP. Therefore, the 2260 same solution also must address the use cases where the user plane 2261 traffic is again another layer or Ethernet frames. There is existing 2262 work describing the problem statement 2263 [I-D.finn-detnet-problem-statement] and the architecture 2264 [I-D.finn-detnet-architecture] for deterministic networking (DetNet) 2265 that targets solutions for time-sensitive (IP/transport) streams with 2266 deterministic properties over Ethernet-based switched networks. 2268 6.4. Cellular Radio Networks Asks 2270 A standard for data plane transport specification which is: 2272 o Unified among all *hauls 2274 o Deployed in a highly deterministic network environment 2276 A standard for data flow information models that are: 2278 o Aware of the time sensitivity and constraints of the target 2279 networking environment 2281 o Aware of underlying deterministic networking services (e.g. on the 2282 Ethernet layer) 2284 Mapping the Fronthaul requirements to IETF DetNet 2285 [I-D.finn-detnet-architecture] Section 3 "Providing the DetNet 2286 Quality of Service", the relevant features are: 2288 o Zero congestion loss. 2290 o Pinned-down paths. 2292 7. Cellular Coordinated Multipoint Processing (CoMP) 2294 7.1. Use Case Description 2296 In cellular wireless communication systems, Inter-Site Coordinated 2297 Multipoint Processing (CoMP, see [CoMP]) is a technique implemented 2298 within a cell site which improves system efficiency and user quality 2299 experience by significantly improving throughput in the cell-edge 2300 region (i.e. at the edges of that cell site's radio coverage area). 2301 CoMP techniques depend on deterministic high-reliability 2302 communication between cell sites, however such connections today are 2303 IP-based which in current mobile networks can not meet the QoS 2304 requirements, so CoMP is an emerging technology which can benefit 2305 from DetNet. 2307 Here we consider the JT (Joint Transmit) application for CoMP, which 2308 provides the highest performance gain (compared to other 2309 applications). 2311 7.1.1. CoMP Architecture 2313 +--------------------------+ 2314 | CoMP | 2315 +--+--------------------+--+ 2316 | | 2317 +----------+ +------------+ 2318 | Uplink | | Downlink | 2319 +-----+----+ +--------+---+ 2320 | | 2321 ------------------- ----------------------- 2322 | | | | | | 2323 +---------+ +----+ +-----+ +------------+ +-----+ +-----+ 2324 | Joint | | CS | | DPS | | Joint | | CS/ | | DPS | 2325 |Reception| | | | | |Transmission| | CB | | | 2326 +---------+ +----+ +-----+ +------------+ +-----+ +-----+ 2327 | | 2328 |----------- |------------- 2329 | | | | 2330 +------------+ +---------+ +----------+ +------------+ 2331 | Joint | | Soft | | Coherent | | Non- | 2332 |Equalization| |Combining| | JT | | Coherent JT| 2333 +------------+ +---------+ +----------+ +------------+ 2335 Figure 8: Framework of CoMP Technology 2337 As shown in Figure 8, CoMP reception and transmission is a framework 2338 in which multiple geographically distributed antenna nodes cooperate 2339 to improve the performance of the users served in the common 2340 cooperation area. The design principal of CoMP is to extend the 2341 current single-cell to multi-UE (User Equipment) transmission to a 2342 multi-cell- to-multi-UEs transmission by base station cooperation. 2344 7.1.2. Delay Sensitivity in CoMP 2346 In contrast to the single-cell scenario, CoMP has delay-sensitive 2347 performance parameters, which are "backhaul latency" and "CSI 2348 (Channel State Information) reporting and accuracy". The essential 2349 feature of CoMP is signaling between eNBs, so the backhaul latency is 2350 the dominating limitation of the CoMP performance. Generally, JT can 2351 benefit from coordinated scheduling (either distributed or 2352 centralized) of different cells if the signaling delay between eNBs 2353 is within 4-10ms. This delay requirement is both rigid and absolute 2354 because any uncertainty in delay will degrade the performance 2355 significantly. 2357 7.2. CoMP Today 2359 Due to the strict sensitivity to latency and synchronization, CoMP 2360 between eNB has not been deployed yet. This is because the current 2361 interface path between eNBs cannot meet the delay bound because it is 2362 usually IP-based and passing through multiple network hops (this 2363 interface is called "X2" or "eX2" for "enhanced X2"). Today lack of 2364 absolute delay guarantee on X2/eX2 traffic is the main obstacle to JT 2365 and multi-eNB coordination. 2367 There is still lack of Layer-3 (IP) transport protocol and signaling 2368 that is capable of low latency services; current techniques such as 2369 MPLS and PWE focus on establishing circuits using pre-routed paths 2370 but there is no such signaling for reservation of time-sensitive 2371 stream. 2373 7.3. CoMP Future 2375 7.3.1. Mobile Industry Overall Goals 2377 [METIS] documents the fundamental challenges as well as overall 2378 technical goals of the 5G mobile and wireless system as the starting 2379 point. These future systems should support (at similar cost and 2380 energy consumption levels as today's system): 2382 o 1000 times higher mobile data volume per area 2384 o 10 times to 100 times higher typical user data rate 2386 o 10 times to 100 times higher number of connected devices 2388 o 10 times longer battery life for low power devices 2390 o 5 times reduced End-to-End (E2E) latency 2391 The current LTE networking system has E2E latency less than 20ms 2392 [LTE-Latency] which leads to around 5ms E2E latency for 5G networks. 2393 To fulfill these latency demands at similar cost will be challenging 2394 because as the system also requires 100x bandwidth and 100x connected 2395 devices, simply adding redundant bandwidth provisioning can no longer 2396 be an efficient solution. 2398 In addition to bandwidth provisioning, reserved critical flows should 2399 not be affected by other flows no matter the pressure of the network. 2400 Deterministic networking techniques in both layer-2 and layer-3 using 2401 IETF protocol solutions can be promising to serve these scenarios. 2403 7.3.2. CoMP Infrastructure Goals 2405 Inter-site CoMP is one of the key requirements for 5G and is also a 2406 near-term goal for the current 4.5G network architecture. Assuming 2407 network architecture remains unchanged (i.e. no Fronthaul network and 2408 data flow between eNB is via X2/eX2) we would like to see the 2409 following in the near future: 2411 o Unified protocols and delay-guaranteed forwarding network 2412 equipment that is capable of delivering deterministic latency 2413 services. 2415 o Unified management and protocols which take delay and timing into 2416 account. 2418 o Unified deterministic latency data model and signaling for 2419 resource reservation. 2421 7.4. CoMP Asks 2423 To fully utilize the power of CoMP, it requires: 2425 o Very tight absolute delay bound (100-500us) within 7-10 hops. 2427 o Standardized data plane with highly deterministic networking 2428 capability. 2430 o Standardized control plane to unify backhaul network elements with 2431 time-sensitive stream reservation signaling. 2433 In addition, a standardized deterministic latency data flow model 2434 that includes: 2436 o Network-aware constraints on the networking environment 2437 o Time-aware description of flow characteristics and network 2438 resources, which may not need to be bandwidth based 2440 o Application-aware description of deterministic latency services. 2442 8. Industrial M2M 2444 8.1. Use Case Description 2446 Industrial Automation in general refers to automation of 2447 manufacturing, quality control and material processing. In this 2448 "machine to machine" (M2M) use case we consider machine units in a 2449 plant floor which periodically exchange data with upstream or 2450 downstream machine modules and/or a supervisory controller within a 2451 local area network. 2453 The actors of M2M communication are Programmable Logic Controllers 2454 (PLCs). Communication between PLCs and between PLCs and the 2455 supervisory PLC (S-PLC) is achieved via critical control/data streams 2456 Figure 9. 2458 S (Sensor) 2459 \ +-----+ 2460 PLC__ \.--. .--. ---| MES | 2461 \_( `. _( `./ +-----+ 2462 A------( Local )-------------( L2 ) 2463 ( Net ) ( Net ) +-------+ 2464 /`--(___.-' `--(___.-' ----| S-PLC | 2465 S_/ / PLC .--. / +-------+ 2466 A_/ \_( `. 2467 (Actuator) ( Local ) 2468 ( Net ) 2469 /`--(___.-'\ 2470 / \ A 2471 S A 2473 Figure 9: Current Generic Industrial M2M Network Architecture 2475 This use case focuses on PLC-related communications; communication to 2476 Manufacturing-Execution-Systems (MESs) are not addressed. 2478 This use case covers only critical control/data streams; non-critical 2479 traffic between industrial automation applications (such as 2480 communication of state, configuration, set-up, and database 2481 communication) are adequately served by currently available 2482 prioritizing techniques. Such traffic can use up to 80% of the total 2483 bandwidth required. There is also a subset of non-time-critical 2484 traffic that must be reliable even though it is not time sensitive. 2486 In this use case the primary need for deterministic networking is to 2487 provide end-to-end delivery of M2M messages within specific timing 2488 constraints, for example in closed loop automation control. Today 2489 this level of determinism is provided by proprietary networking 2490 technologies. In addition, standard networking technologies are used 2491 to connect the local network to remote industrial automation sites, 2492 e.g. over an enterprise or metro network which also carries other 2493 types of traffic. Therefore, flows that should be forwarded with 2494 deterministic guarantees need to be sustained regardless of the 2495 amount of other flows in those networks. 2497 8.2. Industrial M2M Communication Today 2499 Today, proprietary networks fulfill the needed timing and 2500 availability for M2M networks. 2502 The network topologies used today by industrial automation are 2503 similar to those used by telecom networks: Daisy Chain, Ring, Hub and 2504 Spoke, and Comb (a subset of Daisy Chain). 2506 PLC-related control/data streams are transmitted periodically and 2507 carry either a pre-configured payload or a payload configured during 2508 runtime. 2510 Some industrial applications require time synchronization at the end 2511 nodes. For such time-coordinated PLCs, accuracy of 1 microsecond is 2512 required. Even in the case of "non-time-coordinated" PLCs time sync 2513 may be needed e.g. for timestamping of sensor data. 2515 Industrial network scenarios require advanced security solutions. 2516 Many of the current industrial production networks are physically 2517 separated. Preventing critical flows from be leaked outside a domain 2518 is handled today by filtering policies that are typically enforced in 2519 firewalls. 2521 8.2.1. Transport Parameters 2523 The Cycle Time defines the frequency of message(s) between industrial 2524 actors. The Cycle Time is application dependent, in the range of 1ms 2525 - 100ms for critical control/data streams. 2527 Because industrial applications assume deterministic transport for 2528 critical Control-Data-Stream parameters (instead of defining latency 2529 and delay variation parameters) it is sufficient to fulfill the upper 2530 bound of latency (maximum latency). The underlying networking 2531 infrastructure must ensure a maximum end-to-end delivery time of 2532 messages in the range of 100 microseconds to 50 milliseconds 2533 depending on the control loop application. 2535 The bandwidth requirements of control/data streams are usually 2536 calculated directly from the bytes-per-cycle parameter of the control 2537 loop. For PLC-to-PLC communication one can expect 2 - 32 streams 2538 with packet size in the range of 100 - 700 bytes. For S-PLC to PLCs 2539 the number of streams is higher - up to 256 streams. Usually no more 2540 than 20% of available bandwidth is used for critical control/data 2541 streams. In today's networks 1Gbps links are commonly used. 2543 Most PLC control loops are rather tolerant of packet loss, however 2544 critical control/data streams accept no more than 1 packet loss per 2545 consecutive communication cycle (i.e. if a packet gets lost in cycle 2546 "n", then the next cycle ("n+1") must be lossless). After two or 2547 more consecutive packet losses the network may be considered to be 2548 "down" by the Application. 2550 As network downtime may impact the whole production system the 2551 required network availability is rather high (99,999%). 2553 Based on the above parameters we expect that some form of redundancy 2554 will be required for M2M communications, however any individual 2555 solution depends on several parameters including cycle time, delivery 2556 time, etc. 2558 8.2.2. Stream Creation and Destruction 2560 In an industrial environment, critical control/data streams are 2561 created rather infrequently, on the order of ~10 times per day / week 2562 / month. Most of these critical control/data streams get created at 2563 machine startup, however flexibility is also needed during runtime, 2564 for example when adding or removing a machine. Going forward as 2565 production systems become more flexible, we expect a significant 2566 increase in the rate at which streams are created, changed and 2567 destroyed. 2569 8.3. Industrial M2M Future 2571 We would like to see a converged IP-standards-based network with 2572 deterministic properties that can satisfy the timing, security and 2573 reliability constraints described above. Today's proprietary 2574 networks could then be interfaced to such a network via gateways or, 2575 in the case of new installations, devices could be connected directly 2576 to the converged network. 2578 8.4. Industrial M2M Asks 2580 o Converged IP-based network 2582 o Deterministic behavior (bounded latency and jitter ) 2584 o High availability (presumably through redundancy) (99.999 %) 2586 o Low message delivery time (100us - 50ms) 2588 o Low packet loss (burstless, 0.1-1 %) 2590 o Precise time synchronization accuracy (1us) 2592 o Security (e.g. prevent critical flows from being leaked between 2593 physically separated networks) 2595 9. Internet-based Applications 2597 9.1. Use Case Description 2599 There are many applications that communicate across the open Internet 2600 that could benefit from guaranteed delivery and bounded latency. The 2601 following are some representative examples. 2603 9.1.1. Media Content Delivery 2605 Media content delivery continues to be an important use of the 2606 Internet, yet users often experience poor quality audio and video due 2607 to the delay and jitter inherent in today's Internet. 2609 9.1.2. Online Gaming 2611 Online gaming is a significant part of the gaming market, however 2612 latency can degrade the end user experience. For example "First 2613 Person Shooter" (FPS) games are highly delay-sensitive. 2615 9.1.3. Virtual Reality 2617 Virtual reality (VR) has many commercial applications including real 2618 estate presentations, remote medical procedures, and so on. Low 2619 latency is critical to interacting with the virtual world because 2620 perceptual delays can cause motion sickness. 2622 9.2. Internet-Based Applications Today 2624 Internet service today is by definition "best effort", with no 2625 guarantees on delivery or bandwidth. 2627 9.3. Internet-Based Applications Future 2629 We imagine an Internet from which we will be able to play a video 2630 without glitches and play games without lag. 2632 For online gaming, the maximum round-trip delay can be 100ms and 2633 stricter for FPS gaming which can be 10-50ms. Transport delay is the 2634 dominate part with a 5-20ms budget. 2636 For VR, 1-10ms maximum delay is needed and total network budget is 2637 1-5ms if doing remote VR. 2639 Flow identification can be used for gaming and VR, i.e. it can 2640 recognize a critical flow and provide appropriate latency bounds. 2642 9.4. Internet-Based Applications Asks 2644 o Unified control and management protocols to handle time-critical 2645 data flow 2647 o Application-aware flow filtering mechanism to recognize the timing 2648 critical flow without doing 5-tuple matching 2650 o Unified control plane to provide low latency service on Layer-3 2651 without changing the data plane 2653 o OAM system and protocols which can help to provide E2E-delay 2654 sensitive service provisioning 2656 10. Use Case Common Elements 2658 Looking at the use cases collectively, the following common desires 2659 for the DetNet-based networks of the future emerge: 2661 o Open standards-based network (replace various proprietary 2662 networks, reduce cost, create multi-vendor market) 2664 o Centrally administered (though such administration may be 2665 distributed for scale and resiliency) 2667 o Integrates L2 (bridged) and L3 (routed) environments (independent 2668 of the Link layer, e.g. can be used with Ethernet, 6TiSCH, etc.) 2670 o Carries both deterministic and best-effort traffic (guaranteed 2671 end-to-end delivery of deterministic flows, deterministic flows 2672 isolated from each other and from best-effort traffic congestion, 2673 unused deterministic BW available to best-effort traffic) 2675 o Ability to add or remove systems from the network with minimal, 2676 bounded service interruption (applications include replacement of 2677 failed devices as well as plug and play) 2679 o Uses standardized data flow information models capable of 2680 expressing deterministic properties (models express device 2681 capabilities, flow properties. Protocols for pushing models from 2682 controller to devices, devices to controller) 2684 o Scalable size (long distances (many km) and short distances 2685 (within a single machine), many hops (radio repeaters, microwave 2686 links, fiber links...) and short hops (single machine)) 2688 o Scalable timing parameters and accuracy (bounded latency, 2689 guaranteed worst case maximum, minimum. Low latency, e.g. control 2690 loops may be less than 1ms, but larger for wide area networks) 2692 o High availability (99.9999 percent up time requested, but may be 2693 up to twelve 9s) 2695 o Reliability, redundancy (lives at stake) 2697 o Security (from failures, attackers, misbehaving devices - 2698 sensitive to both packet content and arrival time) 2700 11. Acknowledgments 2702 11.1. Pro Audio 2704 This section was derived from draft-gunther-detnet-proaudio-req-01. 2706 The editors would like to acknowledge the help of the following 2707 individuals and the companies they represent: 2709 Jeff Koftinoff, Meyer Sound 2711 Jouni Korhonen, Associate Technical Director, Broadcom 2713 Pascal Thubert, CTAO, Cisco 2715 Kieran Tyrrell, Sienda New Media Technologies GmbH 2717 11.2. Utility Telecom 2719 This section was derived from draft-wetterwald-detnet-utilities-reqs- 2720 02. 2722 Faramarz Maghsoodlou, Ph. D. IoT Connected Industries and Energy 2723 Practice Cisco 2725 Pascal Thubert, CTAO Cisco 2727 11.3. Building Automation Systems 2729 This section was derived from draft-bas-usecase-detnet-00. 2731 11.4. Wireless for Industrial 2733 This section was derived from draft-thubert-6tisch-4detnet-01. 2735 This specification derives from the 6TiSCH architecture, which is the 2736 result of multiple interactions, in particular during the 6TiSCH 2737 (bi)Weekly Interim call, relayed through the 6TiSCH mailing list at 2738 the IETF. 2740 The authors wish to thank: Kris Pister, Thomas Watteyne, Xavier 2741 Vilajosana, Qin Wang, Tom Phinney, Robert Assimiti, Michael 2742 Richardson, Zhuo Chen, Malisa Vucinic, Alfredo Grieco, Martin Turon, 2743 Dominique Barthel, Elvis Vogli, Guillaume Gaillard, Herman Storey, 2744 Maria Rita Palattella, Nicola Accettura, Patrick Wetterwald, Pouria 2745 Zand, Raghuram Sudhaakar, and Shitanshu Shah for their participation 2746 and various contributions. 2748 11.5. Cellular Radio 2750 This section was derived from draft-korhonen-detnet-telreq-00. 2752 11.6. Industrial M2M 2754 The authors would like to thank Feng Chen and Marcel Kiessling for 2755 their comments and suggestions. 2757 11.7. Internet Applications and CoMP 2759 This section was derived from draft-zha-detnet-use-case-00. 2761 This document has benefited from reviews, suggestions, comments and 2762 proposed text provided by the following members, listed in 2763 alphabetical order: Jing Huang, Junru Lin, Lehong Niu and Oilver 2764 Huang. 2766 12. Informative References 2768 [ACE] IETF, "Authentication and Authorization for Constrained 2769 Environments", . 2772 [bacnetip] 2773 ASHRAE, "Annex J to ANSI/ASHRAE 135-1995 - BACnet/IP", 2774 January 1999. 2776 [CCAMP] IETF, "Common Control and Measurement Plane", 2777 . 2779 [CoMP] NGMN Alliance, "RAN EVOLUTION PROJECT COMP EVALUATION AND 2780 ENHANCEMENT", NGMN Alliance NGMN_RANEV_D3_CoMP_Evaluation_ 2781 and_Enhancement_v2.0, March 2015, 2782 . 2785 [CONTENT_PROTECTION] 2786 Olsen, D., "1722a Content Protection", 2012, 2787 . 2790 [CPRI] CPRI Cooperation, "Common Public Radio Interface (CPRI); 2791 Interface Specification", CPRI Specification V6.1, July 2792 2014, . 2795 [DCI] Digital Cinema Initiatives, LLC, "DCI Specification, 2796 Version 1.2", 2012, . 2798 [DICE] IETF, "DTLS In Constrained Environments", 2799 . 2801 [EA12] Evans, P. and M. Annunziata, "Industrial Internet: Pushing 2802 the Boundaries of Minds and Machines", November 2012. 2804 [ESPN_DC2] 2805 Daley, D., "ESPN's DC2 Scales AVB Large", 2014, 2806 . 2809 [flnet] Japan Electrical Manufacturers' Association, "JEMA 1479 - 2810 English Edition", September 2012. 2812 [Fronthaul] 2813 Chen, D. and T. Mustala, "Ethernet Fronthaul 2814 Considerations", IEEE 1904.3, February 2015, 2815 . 2818 [HART] www.hartcomm.org, "Highway Addressable remote Transducer, 2819 a group of specifications for industrial process and 2820 control devices administered by the HART Foundation". 2822 [I-D.finn-detnet-architecture] 2823 Finn, N., Thubert, P., and M. Teener, "Deterministic 2824 Networking Architecture", draft-finn-detnet- 2825 architecture-03 (work in progress), March 2016. 2827 [I-D.finn-detnet-problem-statement] 2828 Finn, N. and P. Thubert, "Deterministic Networking Problem 2829 Statement", draft-finn-detnet-problem-statement-04 (work 2830 in progress), October 2015. 2832 [I-D.ietf-6tisch-6top-interface] 2833 Wang, Q. and X. Vilajosana, "6TiSCH Operation Sublayer 2834 (6top) Interface", draft-ietf-6tisch-6top-interface-04 2835 (work in progress), July 2015. 2837 [I-D.ietf-6tisch-architecture] 2838 Thubert, P., "An Architecture for IPv6 over the TSCH mode 2839 of IEEE 802.15.4", draft-ietf-6tisch-architecture-09 (work 2840 in progress), November 2015. 2842 [I-D.ietf-6tisch-coap] 2843 Sudhaakar, R. and P. Zand, "6TiSCH Resource Management and 2844 Interaction using CoAP", draft-ietf-6tisch-coap-03 (work 2845 in progress), March 2015. 2847 [I-D.ietf-6tisch-terminology] 2848 Palattella, M., Thubert, P., Watteyne, T., and Q. Wang, 2849 "Terminology in IPv6 over the TSCH mode of IEEE 2850 802.15.4e", draft-ietf-6tisch-terminology-06 (work in 2851 progress), November 2015. 2853 [I-D.ietf-ipv6-multilink-subnets] 2854 Thaler, D. and C. Huitema, "Multi-link Subnet Support in 2855 IPv6", draft-ietf-ipv6-multilink-subnets-00 (work in 2856 progress), July 2002. 2858 [I-D.ietf-roll-rpl-industrial-applicability] 2859 Phinney, T., Thubert, P., and R. Assimiti, "RPL 2860 applicability in industrial networks", draft-ietf-roll- 2861 rpl-industrial-applicability-02 (work in progress), 2862 October 2013. 2864 [I-D.ietf-tictoc-1588overmpls] 2865 Davari, S., Oren, A., Bhatia, M., Roberts, P., and L. 2866 Montini, "Transporting Timing messages over MPLS 2867 Networks", draft-ietf-tictoc-1588overmpls-07 (work in 2868 progress), October 2015. 2870 [I-D.kh-spring-ip-ran-use-case] 2871 Khasnabish, B., hu, f., and L. Contreras, "Segment Routing 2872 in IP RAN use case", draft-kh-spring-ip-ran-use-case-02 2873 (work in progress), November 2014. 2875 [I-D.mirsky-mpls-residence-time] 2876 Mirsky, G., Ruffini, S., Gray, E., Drake, J., Bryant, S., 2877 and S. Vainshtein, "Residence Time Measurement in MPLS 2878 network", draft-mirsky-mpls-residence-time-07 (work in 2879 progress), July 2015. 2881 [I-D.svshah-tsvwg-deterministic-forwarding] 2882 Shah, S. and P. Thubert, "Deterministic Forwarding PHB", 2883 draft-svshah-tsvwg-deterministic-forwarding-04 (work in 2884 progress), August 2015. 2886 [I-D.thubert-6lowpan-backbone-router] 2887 Thubert, P., "6LoWPAN Backbone Router", draft-thubert- 2888 6lowpan-backbone-router-03 (work in progress), February 2889 2013. 2891 [I-D.wang-6tisch-6top-sublayer] 2892 Wang, Q. and X. Vilajosana, "6TiSCH Operation Sublayer 2893 (6top)", draft-wang-6tisch-6top-sublayer-04 (work in 2894 progress), November 2015. 2896 [IEC61850-90-12] 2897 TC57 WG10, IEC., "IEC 61850-90-12 TR: Communication 2898 networks and systems for power utility automation - Part 2899 90-12: Wide area network engineering guidelines", 2015. 2901 [IEC62439-3:2012] 2902 TC65, IEC., "IEC 62439-3: Industrial communication 2903 networks - High availability automation networks - Part 3: 2904 Parallel Redundancy Protocol (PRP) and High-availability 2905 Seamless Redundancy (HSR)", 2012. 2907 [IEEE1588] 2908 IEEE, "IEEE Standard for a Precision Clock Synchronization 2909 Protocol for Networked Measurement and Control Systems", 2910 IEEE Std 1588-2008, 2008, 2911 . 2914 [IEEE1722] 2915 IEEE, "1722-2011 - IEEE Standard for Layer 2 Transport 2916 Protocol for Time Sensitive Applications in a Bridged 2917 Local Area Network", IEEE Std 1722-2011, 2011, 2918 . 2921 [IEEE19043] 2922 IEEE Standards Association, "IEEE 1904.3 TF", IEEE 1904.3, 2923 2015, . 2925 [IEEE802.1TSNTG] 2926 IEEE Standards Association, "IEEE 802.1 Time-Sensitive 2927 Networks Task Group", March 2013, 2928 . 2930 [IEEE802154] 2931 IEEE standard for Information Technology, "IEEE std. 2932 802.15.4, Part. 15.4: Wireless Medium Access Control (MAC) 2933 and Physical Layer (PHY) Specifications for Low-Rate 2934 Wireless Personal Area Networks". 2936 [IEEE802154e] 2937 IEEE standard for Information Technology, "IEEE standard 2938 for Information Technology, IEEE std. 802.15.4, Part. 2939 15.4: Wireless Medium Access Control (MAC) and Physical 2940 Layer (PHY) Specifications for Low-Rate Wireless Personal 2941 Area Networks, June 2011 as amended by IEEE std. 2942 802.15.4e, Part. 15.4: Low-Rate Wireless Personal Area 2943 Networks (LR-WPANs) Amendment 1: MAC sublayer", April 2944 2012. 2946 [IEEE8021AS] 2947 IEEE, "Timing and Synchronizations (IEEE 802.1AS-2011)", 2948 IEEE 802.1AS-2001, 2011, 2949 . 2952 [IEEE8021CM] 2953 Farkas, J., "Time-Sensitive Networking for Fronthaul", 2954 Unapproved PAR, PAR for a New IEEE Standard; 2955 IEEE P802.1CM, April 2015, 2956 . 2959 [IEEE8021TSN] 2960 IEEE 802.1, "The charter of the TG is to provide the 2961 specifications that will allow time-synchronized low 2962 latency streaming services through 802 networks.", 2016, 2963 . 2965 [IETFDetNet] 2966 IETF, "Charter for IETF DetNet Working Group", 2015, 2967 . 2969 [ISA100] ISA/ANSI, "ISA100, Wireless Systems for Automation", 2970 . 2972 [ISA100.11a] 2973 ISA/ANSI, "Wireless Systems for Industrial Automation: 2974 Process Control and Related Applications - ISA100.11a-2011 2975 - IEC 62734", 2011, . 2978 [ISO7240-16] 2979 ISO, "ISO 7240-16:2007 Fire detection and alarm systems -- 2980 Part 16: Sound system control and indicating equipment", 2981 2007, . 2984 [knx] KNX Association, "ISO/IEC 14543-3 - KNX", November 2006. 2986 [lontalk] ECHELON, "LonTalk(R) Protocol Specification Version 3.0", 2987 1994. 2989 [LTE-Latency] 2990 Johnston, S., "LTE Latency: How does it compare to other 2991 technologies", March 2014, 2992 . 2995 [MEF] MEF, "Mobile Backhaul Phase 2 Amendment 1 -- Small Cells", 2996 MEF 22.1.1, July 2014, 2997 . 3000 [METIS] METIS, "Scenarios, requirements and KPIs for 5G mobile and 3001 wireless system", ICT-317669-METIS/D1.1 ICT- 3002 317669-METIS/D1.1, April 2013, . 3005 [modbus] Modbus Organization, "MODBUS APPLICATION PROTOCOL 3006 SPECIFICATION V1.1b", December 2006. 3008 [net5G] Ericsson, "5G Radio Access, Challenges for 2020 and 3009 Beyond", Ericsson white paper wp-5g, June 2013, 3010 . 3012 [NGMN] NGMN Alliance, "5G White Paper", NGMN 5G White Paper v1.0, 3013 February 2015, . 3016 [PCE] IETF, "Path Computation Element", 3017 . 3019 [profibus] 3020 IEC, "IEC 61158 Type 3 - Profibus DP", January 2001. 3022 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 3023 Requirement Levels", BCP 14, RFC 2119, 3024 DOI 10.17487/RFC2119, March 1997, 3025 . 3027 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 3028 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, 3029 December 1998, . 3031 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 3032 "Definition of the Differentiated Services Field (DS 3033 Field) in the IPv4 and IPv6 Headers", RFC 2474, 3034 DOI 10.17487/RFC2474, December 1998, 3035 . 3037 [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol 3038 Label Switching Architecture", RFC 3031, 3039 DOI 10.17487/RFC3031, January 2001, 3040 . 3042 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 3043 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 3044 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 3045 . 3047 [RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation 3048 Metric for IP Performance Metrics (IPPM)", RFC 3393, 3049 DOI 10.17487/RFC3393, November 2002, 3050 . 3052 [RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between 3053 Information Models and Data Models", RFC 3444, 3054 DOI 10.17487/RFC3444, January 2003, 3055 . 3057 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 3058 RFC 3972, DOI 10.17487/RFC3972, March 2005, 3059 . 3061 [RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation 3062 Edge-to-Edge (PWE3) Architecture", RFC 3985, 3063 DOI 10.17487/RFC3985, March 2005, 3064 . 3066 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 3067 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 3068 2006, . 3070 [RFC4553] Vainshtein, A., Ed. and YJ. Stein, Ed., "Structure- 3071 Agnostic Time Division Multiplexing (TDM) over Packet 3072 (SAToP)", RFC 4553, DOI 10.17487/RFC4553, June 2006, 3073 . 3075 [RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903, 3076 DOI 10.17487/RFC4903, June 2007, 3077 . 3079 [RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6 3080 over Low-Power Wireless Personal Area Networks (6LoWPANs): 3081 Overview, Assumptions, Problem Statement, and Goals", 3082 RFC 4919, DOI 10.17487/RFC4919, August 2007, 3083 . 3085 [RFC5086] Vainshtein, A., Ed., Sasson, I., Metz, E., Frost, T., and 3086 P. Pate, "Structure-Aware Time Division Multiplexed (TDM) 3087 Circuit Emulation Service over Packet Switched Network 3088 (CESoPSN)", RFC 5086, DOI 10.17487/RFC5086, December 2007, 3089 . 3091 [RFC5087] Stein, Y(J)., Shashoua, R., Insler, R., and M. Anavi, 3092 "Time Division Multiplexing over IP (TDMoIP)", RFC 5087, 3093 DOI 10.17487/RFC5087, December 2007, 3094 . 3096 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 3097 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 3098 DOI 10.17487/RFC6282, September 2011, 3099 . 3101 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 3102 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 3103 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 3104 Low-Power and Lossy Networks", RFC 6550, 3105 DOI 10.17487/RFC6550, March 2012, 3106 . 3108 [RFC6551] Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N., 3109 and D. Barthel, "Routing Metrics Used for Path Calculation 3110 in Low-Power and Lossy Networks", RFC 6551, 3111 DOI 10.17487/RFC6551, March 2012, 3112 . 3114 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 3115 Bormann, "Neighbor Discovery Optimization for IPv6 over 3116 Low-Power Wireless Personal Area Networks (6LoWPANs)", 3117 RFC 6775, DOI 10.17487/RFC6775, November 2012, 3118 . 3120 [RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using 3121 IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the 3122 Internet of Things (IoT): Problem Statement", RFC 7554, 3123 DOI 10.17487/RFC7554, May 2015, 3124 . 3126 [SRP_LATENCY] 3127 Gunther, C., "Specifying SRP Latency", 2014, 3128 . 3131 [STUDIO_IP] 3132 Mace, G., "IP Networked Studio Infrastructure for 3133 Synchronized & Real-Time Multimedia Transmissions", 2007, 3134 . 3137 [SyncE] ITU-T, "G.8261 : Timing and synchronization aspects in 3138 packet networks", Recommendation G.8261, August 2013, 3139 . 3141 [TEAS] IETF, "Traffic Engineering Architecture and Signaling", 3142 . 3144 [TS23401] 3GPP, "General Packet Radio Service (GPRS) enhancements 3145 for Evolved Universal Terrestrial Radio Access Network 3146 (E-UTRAN) access", 3GPP TS 23.401 10.10.0, March 2013. 3148 [TS25104] 3GPP, "Base Station (BS) radio transmission and reception 3149 (FDD)", 3GPP TS 25.104 3.14.0, March 2007. 3151 [TS36104] 3GPP, "Evolved Universal Terrestrial Radio Access 3152 (E-UTRA); Base Station (BS) radio transmission and 3153 reception", 3GPP TS 36.104 10.11.0, July 2013. 3155 [TS36133] 3GPP, "Evolved Universal Terrestrial Radio Access 3156 (E-UTRA); Requirements for support of radio resource 3157 management", 3GPP TS 36.133 12.7.0, April 2015. 3159 [TS36211] 3GPP, "Evolved Universal Terrestrial Radio Access 3160 (E-UTRA); Physical channels and modulation", 3GPP 3161 TS 36.211 10.7.0, March 2013. 3163 [TS36300] 3GPP, "Evolved Universal Terrestrial Radio Access (E-UTRA) 3164 and Evolved Universal Terrestrial Radio Access Network 3165 (E-UTRAN); Overall description; Stage 2", 3GPP TS 36.300 3166 10.11.0, September 2013. 3168 [TSNTG] IEEE Standards Association, "IEEE 802.1 Time-Sensitive 3169 Networks Task Group", 2013, 3170 . 3172 [UHD-video] 3173 Holub, P., "Ultra-High Definition Videos and Their 3174 Applications over the Network", The 7th International 3175 Symposium on VICTORIES Project PetrHolub_presentation, 3176 October 2014, . 3179 [WirelessHART] 3180 www.hartcomm.org, "Industrial Communication Networks - 3181 Wireless Communication Network and Communication Profiles 3182 - WirelessHART - IEC 62591", 2010. 3184 Authors' Addresses 3185 Ethan Grossman (editor) 3186 Dolby Laboratories, Inc. 3187 1275 Market Street 3188 San Francisco, CA 94103 3189 USA 3191 Phone: +1 415 645 4726 3192 Email: ethan.grossman@dolby.com 3193 URI: http://www.dolby.com 3195 Craig Gunther 3196 Harman International 3197 10653 South River Front Parkway 3198 South Jordan, UT 84095 3199 USA 3201 Phone: +1 801 568-7675 3202 Email: craig.gunther@harman.com 3203 URI: http://www.harman.com 3205 Pascal Thubert 3206 Cisco Systems, Inc 3207 Building D 3208 45 Allee des Ormes - BP1200 3209 MOUGINS - Sophia Antipolis 06254 3210 FRANCE 3212 Phone: +33 497 23 26 34 3213 Email: pthubert@cisco.com 3215 Patrick Wetterwald 3216 Cisco Systems 3217 45 Allees des Ormes 3218 Mougins 06250 3219 FRANCE 3221 Phone: +33 4 97 23 26 36 3222 Email: pwetterw@cisco.com 3223 Jean Raymond 3224 Hydro-Quebec 3225 1500 University 3226 Montreal H3A3S7 3227 Canada 3229 Phone: +1 514 840 3000 3230 Email: raymond.jean@hydro.qc.ca 3232 Jouni Korhonen 3233 Broadcom Corporation 3234 3151 Zanker Road 3235 San Jose, CA 95134 3236 USA 3238 Email: jouni.nospam@gmail.com 3240 Yu Kaneko 3241 Toshiba 3242 1 Komukai-Toshiba-cho, Saiwai-ku, Kasasaki-shi 3243 Kanagawa, Japan 3245 Email: yu1.kaneko@toshiba.co.jp 3247 Subir Das 3248 Applied Communication Sciences 3249 150 Mount Airy Road, Basking Ridge 3250 New Jersey, 07920, USA 3252 Email: sdas@appcomsci.com 3254 Yiyong Zha 3255 Huawei Technologies 3257 Email: zhayiyong@huawei.com 3259 Balazs Varga 3260 Ericsson 3261 Konyves Kalman krt. 11/B 3262 Budapest 1097 3263 Hungary 3265 Email: balazs.a.varga@ericsson.com 3266 Janos Farkas 3267 Ericsson 3268 Konyves Kalman krt. 11/B 3269 Budapest 1097 3270 Hungary 3272 Email: janos.farkas@ericsson.com 3274 Franz-Josef Goetz 3275 Siemens 3276 Gleiwitzerstr. 555 3277 Nurnberg 90475 3278 Germany 3280 Email: franz-josef.goetz@siemens.com 3282 Juergen Schmitt 3283 Siemens 3284 Gleiwitzerstr. 555 3285 Nurnberg 90475 3286 Germany 3288 Email: juergen.jues.schmitt@siemens.com