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2 Internet Engineering Task Force E. Grossman, Ed.
3 Internet-Draft DOLBY
4 Intended status: Informational April 2, 2018
5 Expires: October 4, 2018
7 Deterministic Networking Use Cases
8 draft-ietf-detnet-use-cases-15
10 Abstract
12 This draft documents requirements in several diverse industries to
13 establish multi-hop paths for characterized flows with deterministic
14 properties. In this context deterministic implies that streams can
15 be established which provide guaranteed bandwidth and latency which
16 can be established from either a Layer 2 or Layer 3 (IP) interface,
17 and which can co-exist on an IP network with best-effort traffic.
19 Additional requirements include optional redundant paths, very high
20 reliability paths, time synchronization, and clock distribution.
21 Industries considered include professional audio, electrical
22 utilities, building automation systems, wireless for industrial,
23 cellular radio, industrial machine-to-machine, mining, private
24 blockchain, and network slicing.
26 For each case, this document will identify the application, identify
27 representative solutions used today, and the improvements IETF DetNet
28 solutions may enable.
30 Status of This Memo
32 This Internet-Draft is submitted in full conformance with the
33 provisions of BCP 78 and BCP 79.
35 Internet-Drafts are working documents of the Internet Engineering
36 Task Force (IETF). Note that other groups may also distribute
37 working documents as Internet-Drafts. The list of current Internet-
38 Drafts is at https://datatracker.ietf.org/drafts/current/.
40 Internet-Drafts are draft documents valid for a maximum of six months
41 and may be updated, replaced, or obsoleted by other documents at any
42 time. It is inappropriate to use Internet-Drafts as reference
43 material or to cite them other than as "work in progress."
45 This Internet-Draft will expire on October 4, 2018.
47 Copyright Notice
49 Copyright (c) 2018 IETF Trust and the persons identified as the
50 document authors. All rights reserved.
52 This document is subject to BCP 78 and the IETF Trust's Legal
53 Provisions Relating to IETF Documents
54 (https://trustee.ietf.org/license-info) in effect on the date of
55 publication of this document. Please review these documents
56 carefully, as they describe your rights and restrictions with respect
57 to this document. Code Components extracted from this document must
58 include Simplified BSD License text as described in Section 4.e of
59 the Trust Legal Provisions and are provided without warranty as
60 described in the Simplified BSD License.
62 Table of Contents
64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5
65 2. Pro Audio and Video . . . . . . . . . . . . . . . . . . . . . 6
66 2.1. Use Case Description . . . . . . . . . . . . . . . . . . 6
67 2.1.1. Uninterrupted Stream Playback . . . . . . . . . . . . 7
68 2.1.2. Synchronized Stream Playback . . . . . . . . . . . . 7
69 2.1.3. Sound Reinforcement . . . . . . . . . . . . . . . . . 8
70 2.1.4. Deterministic Time to Establish Streaming . . . . . . 8
71 2.1.5. Secure Transmission . . . . . . . . . . . . . . . . . 8
72 2.1.5.1. Safety . . . . . . . . . . . . . . . . . . . . . 8
73 2.2. Pro Audio Today . . . . . . . . . . . . . . . . . . . . . 9
74 2.3. Pro Audio Future . . . . . . . . . . . . . . . . . . . . 9
75 2.3.1. Layer 3 Interconnecting Layer 2 Islands . . . . . . . 9
76 2.3.2. High Reliability Stream Paths . . . . . . . . . . . . 9
77 2.3.3. Integration of Reserved Streams into IT Networks . . 9
78 2.3.4. Use of Unused Reservations by Best-Effort Traffic . . 10
79 2.3.5. Traffic Segregation . . . . . . . . . . . . . . . . . 10
80 2.3.5.1. Packet Forwarding Rules, VLANs and Subnets . . . 10
81 2.3.5.2. Multicast Addressing (IPv4 and IPv6) . . . . . . 11
82 2.3.6. Latency Optimization by a Central Controller . . . . 11
83 2.3.7. Reduced Device Cost Due To Reduced Buffer Memory . . 11
84 2.4. Pro Audio Asks . . . . . . . . . . . . . . . . . . . . . 12
85 3. Electrical Utilities . . . . . . . . . . . . . . . . . . . . 12
86 3.1. Use Case Description . . . . . . . . . . . . . . . . . . 12
87 3.1.1. Transmission Use Cases . . . . . . . . . . . . . . . 12
88 3.1.1.1. Protection . . . . . . . . . . . . . . . . . . . 12
89 3.1.1.2. Intra-Substation Process Bus Communications . . . 18
90 3.1.1.3. Wide Area Monitoring and Control Systems . . . . 19
91 3.1.1.4. IEC 61850 WAN engineering guidelines requirement
92 classification . . . . . . . . . . . . . . . . . 20
93 3.1.2. Generation Use Case . . . . . . . . . . . . . . . . . 21
94 3.1.2.1. Control of the Generated Power . . . . . . . . . 21
95 3.1.2.2. Control of the Generation Infrastructure . . . . 22
96 3.1.3. Distribution use case . . . . . . . . . . . . . . . . 27
97 3.1.3.1. Fault Location Isolation and Service Restoration
98 (FLISR) . . . . . . . . . . . . . . . . . . . . . 27
99 3.2. Electrical Utilities Today . . . . . . . . . . . . . . . 28
100 3.2.1. Security Current Practices and Limitations . . . . . 28
101 3.3. Electrical Utilities Future . . . . . . . . . . . . . . . 30
102 3.3.1. Migration to Packet-Switched Network . . . . . . . . 31
103 3.3.2. Telecommunications Trends . . . . . . . . . . . . . . 31
104 3.3.2.1. General Telecommunications Requirements . . . . . 31
105 3.3.2.2. Specific Network topologies of Smart Grid
106 Applications . . . . . . . . . . . . . . . . . . 32
107 3.3.2.3. Precision Time Protocol . . . . . . . . . . . . . 33
108 3.3.3. Security Trends in Utility Networks . . . . . . . . . 34
109 3.4. Electrical Utilities Asks . . . . . . . . . . . . . . . . 36
110 4. Building Automation Systems . . . . . . . . . . . . . . . . . 36
111 4.1. Use Case Description . . . . . . . . . . . . . . . . . . 36
112 4.2. Building Automation Systems Today . . . . . . . . . . . . 37
113 4.2.1. BAS Architecture . . . . . . . . . . . . . . . . . . 37
114 4.2.2. BAS Deployment Model . . . . . . . . . . . . . . . . 38
115 4.2.3. Use Cases for Field Networks . . . . . . . . . . . . 40
116 4.2.3.1. Environmental Monitoring . . . . . . . . . . . . 40
117 4.2.3.2. Fire Detection . . . . . . . . . . . . . . . . . 40
118 4.2.3.3. Feedback Control . . . . . . . . . . . . . . . . 41
119 4.2.4. Security Considerations . . . . . . . . . . . . . . . 41
120 4.3. BAS Future . . . . . . . . . . . . . . . . . . . . . . . 41
121 4.4. BAS Asks . . . . . . . . . . . . . . . . . . . . . . . . 42
122 5. Wireless for Industrial . . . . . . . . . . . . . . . . . . . 42
123 5.1. Use Case Description . . . . . . . . . . . . . . . . . . 42
124 5.1.1. Network Convergence using 6TiSCH . . . . . . . . . . 43
125 5.1.2. Common Protocol Development for 6TiSCH . . . . . . . 43
126 5.2. Wireless Industrial Today . . . . . . . . . . . . . . . . 44
127 5.3. Wireless Industrial Future . . . . . . . . . . . . . . . 44
128 5.3.1. Unified Wireless Network and Management . . . . . . . 44
129 5.3.1.1. PCE and 6TiSCH ARQ Retries . . . . . . . . . . . 46
130 5.3.2. Schedule Management by a PCE . . . . . . . . . . . . 47
131 5.3.2.1. PCE Commands and 6TiSCH CoAP Requests . . . . . . 47
132 5.3.2.2. 6TiSCH IP Interface . . . . . . . . . . . . . . . 48
133 5.3.3. 6TiSCH Security Considerations . . . . . . . . . . . 49
134 5.4. Wireless Industrial Asks . . . . . . . . . . . . . . . . 49
135 6. Cellular Radio . . . . . . . . . . . . . . . . . . . . . . . 49
136 6.1. Use Case Description . . . . . . . . . . . . . . . . . . 49
137 6.1.1. Network Architecture . . . . . . . . . . . . . . . . 49
138 6.1.2. Delay Constraints . . . . . . . . . . . . . . . . . . 50
139 6.1.3. Time Synchronization Constraints . . . . . . . . . . 52
140 6.1.4. Transport Loss Constraints . . . . . . . . . . . . . 54
141 6.1.5. Security Considerations . . . . . . . . . . . . . . . 54
142 6.2. Cellular Radio Networks Today . . . . . . . . . . . . . . 55
143 6.2.1. Fronthaul . . . . . . . . . . . . . . . . . . . . . . 55
144 6.2.2. Midhaul and Backhaul . . . . . . . . . . . . . . . . 55
145 6.3. Cellular Radio Networks Future . . . . . . . . . . . . . 56
146 6.4. Cellular Radio Networks Asks . . . . . . . . . . . . . . 58
147 7. Industrial M2M . . . . . . . . . . . . . . . . . . . . . . . 59
148 7.1. Use Case Description . . . . . . . . . . . . . . . . . . 59
149 7.2. Industrial M2M Communication Today . . . . . . . . . . . 60
150 7.2.1. Transport Parameters . . . . . . . . . . . . . . . . 60
151 7.2.2. Stream Creation and Destruction . . . . . . . . . . . 61
152 7.3. Industrial M2M Future . . . . . . . . . . . . . . . . . . 61
153 7.4. Industrial M2M Asks . . . . . . . . . . . . . . . . . . . 62
154 8. Mining Industry . . . . . . . . . . . . . . . . . . . . . . . 62
155 8.1. Use Case Description . . . . . . . . . . . . . . . . . . 62
156 8.2. Mining Industry Today . . . . . . . . . . . . . . . . . . 63
157 8.3. Mining Industry Future . . . . . . . . . . . . . . . . . 63
158 8.4. Mining Industry Asks . . . . . . . . . . . . . . . . . . 64
159 9. Private Blockchain . . . . . . . . . . . . . . . . . . . . . 64
160 9.1. Use Case Description . . . . . . . . . . . . . . . . . . 64
161 9.1.1. Blockchain Operation . . . . . . . . . . . . . . . . 65
162 9.1.2. Blockchain Network Architecture . . . . . . . . . . . 65
163 9.1.3. Security Considerations . . . . . . . . . . . . . . . 66
164 9.2. Private Blockchain Today . . . . . . . . . . . . . . . . 66
165 9.3. Private Blockchain Future . . . . . . . . . . . . . . . . 66
166 9.4. Private Blockchain Asks . . . . . . . . . . . . . . . . . 66
167 10. Network Slicing . . . . . . . . . . . . . . . . . . . . . . . 67
168 10.1. Use Case Description . . . . . . . . . . . . . . . . . . 67
169 10.2. DetNet Applied to Network Slicing . . . . . . . . . . . 67
170 10.2.1. Resource Isolation Across Slices . . . . . . . . . . 67
171 10.2.2. Deterministic Services Within Slices . . . . . . . . 67
172 10.3. A Network Slicing Use Case Example - 5G Bearer Network . 68
173 10.4. Non-5G Applications of Network Slicing . . . . . . . . . 68
174 10.5. Limitations of DetNet in Network Slicing . . . . . . . . 69
175 10.6. Network Slicing Today and Future . . . . . . . . . . . . 69
176 10.7. Network Slicing Asks . . . . . . . . . . . . . . . . . . 69
177 11. Use Case Common Themes . . . . . . . . . . . . . . . . . . . 69
178 11.1. Unified, standards-based network . . . . . . . . . . . . 69
179 11.1.1. Extensions to Ethernet . . . . . . . . . . . . . . . 69
180 11.1.2. Centrally Administered . . . . . . . . . . . . . . . 69
181 11.1.3. Standardized Data Flow Information Models . . . . . 70
182 11.1.4. L2 and L3 Integration . . . . . . . . . . . . . . . 70
183 11.1.5. Consideration for IPv4 . . . . . . . . . . . . . . . 70
184 11.1.6. Guaranteed End-to-End Delivery . . . . . . . . . . . 70
185 11.1.7. Replacement for Multiple Proprietary Deterministic
186 Networks . . . . . . . . . . . . . . . . . . . . . . 70
187 11.1.8. Mix of Deterministic and Best-Effort Traffic . . . . 71
188 11.1.9. Unused Reserved BW to be Available to Best Effort
189 Traffic . . . . . . . . . . . . . . . . . . . . . . 71
190 11.1.10. Lower Cost, Multi-Vendor Solutions . . . . . . . . . 71
192 11.2. Scalable Size . . . . . . . . . . . . . . . . . . . . . 71
193 11.3. Scalable Timing Parameters and Accuracy . . . . . . . . 71
194 11.3.1. Bounded Latency . . . . . . . . . . . . . . . . . . 71
195 11.3.2. Low Latency . . . . . . . . . . . . . . . . . . . . 72
196 11.3.3. Symmetrical Path Delays . . . . . . . . . . . . . . 72
197 11.4. High Reliability and Availability . . . . . . . . . . . 72
198 11.5. Security . . . . . . . . . . . . . . . . . . . . . . . . 72
199 11.6. Deterministic Flows . . . . . . . . . . . . . . . . . . 73
200 12. Use Cases Explicitly Out of Scope for DetNet . . . . . . . . 73
201 12.1. DetNet Scope Limitations . . . . . . . . . . . . . . . . 73
202 12.2. Internet-based Applications . . . . . . . . . . . . . . 74
203 12.2.1. Use Case Description . . . . . . . . . . . . . . . . 74
204 12.2.1.1. Media Content Delivery . . . . . . . . . . . . . 74
205 12.2.1.2. Online Gaming . . . . . . . . . . . . . . . . . 74
206 12.2.1.3. Virtual Reality . . . . . . . . . . . . . . . . 74
207 12.2.2. Internet-Based Applications Today . . . . . . . . . 74
208 12.2.3. Internet-Based Applications Future . . . . . . . . . 74
209 12.2.4. Internet-Based Applications Asks . . . . . . . . . . 75
210 12.3. Pro Audio and Video - Digital Rights Management (DRM) . 75
211 12.4. Pro Audio and Video - Link Aggregation . . . . . . . . . 75
212 13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 76
213 14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 77
214 14.1. Pro Audio . . . . . . . . . . . . . . . . . . . . . . . 77
215 14.2. Utility Telecom . . . . . . . . . . . . . . . . . . . . 78
216 14.3. Building Automation Systems . . . . . . . . . . . . . . 78
217 14.4. Wireless for Industrial . . . . . . . . . . . . . . . . 78
218 14.5. Cellular Radio . . . . . . . . . . . . . . . . . . . . . 78
219 14.6. Industrial M2M . . . . . . . . . . . . . . . . . . . . . 79
220 14.7. Internet Applications and CoMP . . . . . . . . . . . . . 79
221 14.8. Electrical Utilities . . . . . . . . . . . . . . . . . . 79
222 14.9. Network Slicing . . . . . . . . . . . . . . . . . . . . 79
223 14.10. Mining . . . . . . . . . . . . . . . . . . . . . . . . . 79
224 14.11. Private Blockchain . . . . . . . . . . . . . . . . . . . 79
225 15. Informative References . . . . . . . . . . . . . . . . . . . 79
226 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 90
228 1. Introduction
230 This draft presents use cases from diverse industries which have in
231 common a need for deterministic streams, but which also differ
232 notably in their network topologies and specific desired behavior.
233 Together, they provide broad industry context for DetNet and a
234 yardstick against which proposed DetNet designs can be measured (to
235 what extent does a proposed design satisfy these various use cases?)
237 For DetNet, use cases explicitly do not define requirements; The
238 DetNet WG will consider the use cases, decide which elements are in
239 scope for DetNet, and the results will be incorporated into future
240 drafts. Similarly, the DetNet use case draft explicitly does not
241 suggest any specific design, architecture or protocols, which will be
242 topics of future drafts.
244 We present for each use case the answers to the following questions:
246 o What is the use case?
248 o How is it addressed today?
250 o How would you like it to be addressed in the future?
252 o What do you want the IETF to deliver?
254 The level of detail in each use case should be sufficient to express
255 the relevant elements of the use case, but not more.
257 At the end we consider the use cases collectively, and examine the
258 most significant goals they have in common.
260 2. Pro Audio and Video
262 2.1. Use Case Description
264 The professional audio and video industry ("ProAV") includes:
266 o Music and film content creation
268 o Broadcast
270 o Cinema
272 o Live sound
274 o Public address, media and emergency systems at large venues
275 (airports, stadiums, churches, theme parks).
277 These industries have already transitioned audio and video signals
278 from analog to digital. However, the digital interconnect systems
279 remain primarily point-to-point with a single (or small number of)
280 signals per link, interconnected with purpose-built hardware.
282 These industries are now transitioning to packet-based infrastructure
283 to reduce cost, increase routing flexibility, and integrate with
284 existing IT infrastructure.
286 Today ProAV applications have no way to establish deterministic
287 streams from a standards-based Layer 3 (IP) interface, which is a
288 fundamental limitation to the use cases described here. Today
289 deterministic streams can be created within standards-based layer 2
290 LANs (e.g. using IEEE 802.1 AVB) however these are not routable via
291 IP and thus are not effective for distribution over wider areas (for
292 example broadcast events that span wide geographical areas).
294 It would be highly desirable if such streams could be routed over the
295 open Internet, however solutions with more limited scope (e.g.
296 enterprise networks) would still provide a substantial improvement.
298 The following sections describe specific ProAV use cases.
300 2.1.1. Uninterrupted Stream Playback
302 Transmitting audio and video streams for live playback is unlike
303 common file transfer because uninterrupted stream playback in the
304 presence of network errors cannot be achieved by re-trying the
305 transmission; by the time the missing or corrupt packet has been
306 identified it is too late to execute a re-try operation. Buffering
307 can be used to provide enough delay to allow time for one or more
308 retries, however this is not an effective solution in applications
309 where large delays (latencies) are not acceptable (as discussed
310 below).
312 Streams with guaranteed bandwidth can eliminate congestion on the
313 network as a cause of transmission errors that would lead to playback
314 interruption. Use of redundant paths can further mitigate
315 transmission errors to provide greater stream reliability.
317 2.1.2. Synchronized Stream Playback
319 Latency in this context is the time between when a signal is
320 initially sent over a stream and when it is received. A common
321 example in ProAV is time-synchronizing audio and video when they take
322 separate paths through the playback system. In this case the latency
323 of both the audio and video streams must be bounded and consistent if
324 the sound is to remain matched to the movement in the video. A
325 common tolerance for audio/video sync is one NTSC video frame (about
326 33ms) and to maintain the audience perception of correct lip sync the
327 latency needs to be consistent within some reasonable tolerance, for
328 example 10%.
330 A common architecture for synchronizing multiple streams that have
331 different paths through the network (and thus potentially different
332 latencies) is to enable measurement of the latency of each path, and
333 have the data sinks (for example speakers) delay (buffer) all packets
334 on all but the slowest path. Each packet of each stream is assigned
335 a presentation time which is based on the longest required delay.
337 This implies that all sinks must maintain a common time reference of
338 sufficient accuracy, which can be achieved by any of various
339 techniques.
341 This type of architecture is commonly implemented using a central
342 controller that determines path delays and arbitrates buffering
343 delays.
345 2.1.3. Sound Reinforcement
347 Consider the latency (delay) from when a person speaks into a
348 microphone to when their voice emerges from the speaker. If this
349 delay is longer than about 10-15 milliseconds it is noticeable and
350 can make a sound reinforcement system unusable (see slide 6 of
351 [SRP_LATENCY]). (If you have ever tried to speak in the presence of
352 a delayed echo of your voice you may know this experience).
354 Note that the 15ms latency bound includes all parts of the signal
355 path, not just the network, so the network latency must be
356 significantly less than 15ms.
358 In some cases local performers must perform in synchrony with a
359 remote broadcast. In such cases the latencies of the broadcast
360 stream and the local performer must be adjusted to match each other,
361 with a worst case of one video frame (33ms for NTSC video).
363 In cases where audio phase is a consideration, for example beam-
364 forming using multiple speakers, latency requirements can be in the
365 10 microsecond range (1 audio sample at 96kHz).
367 2.1.4. Deterministic Time to Establish Streaming
369 Note: The WG has decided that guidelines for deterministic time to
370 establish stream startup is not within scope of DetNet. If bounded
371 timing of establishing or re-establish streams is required in a given
372 use case, it is up to the application/system to achieve this. (The
373 supporting text from this section has been removed as of draft 12).
375 2.1.5. Secure Transmission
377 2.1.5.1. Safety
379 Professional audio systems can include amplifiers that are capable of
380 generating hundreds or thousands of watts of audio power which if
381 used incorrectly can cause hearing damage to those in the vicinity.
382 Apart from the usual care required by the systems operators to
383 prevent such incidents, the network traffic that controls these
384 devices must be secured (as with any sensitive application traffic).
386 2.2. Pro Audio Today
388 Some proprietary systems have been created which enable deterministic
389 streams at Layer 3 however they are "engineered networks" which
390 require careful configuration to operate, often require that the
391 system be over-provisioned, and it is implied that all devices on the
392 network voluntarily play by the rules of that network. To enable
393 these industries to successfully transition to an interoperable
394 multi-vendor packet-based infrastructure requires effective open
395 standards, and we believe that establishing relevant IETF standards
396 is a crucial factor.
398 2.3. Pro Audio Future
400 2.3.1. Layer 3 Interconnecting Layer 2 Islands
402 It would be valuable to enable IP to connect multiple Layer 2 LANs.
404 As an example, ESPN recently constructed a state-of-the-art 194,000
405 sq ft, $125 million broadcast studio called DC2. The DC2 network is
406 capable of handling 46 Tbps of throughput with 60,000 simultaneous
407 signals. Inside the facility are 1,100 miles of fiber feeding four
408 audio control rooms (see [ESPN_DC2] ).
410 In designing DC2 they replaced as much point-to-point technology as
411 they could with packet-based technology. They constructed seven
412 individual studios using layer 2 LANS (using IEEE 802.1 AVB) that
413 were entirely effective at routing audio within the LANs. However to
414 interconnect these layer 2 LAN islands together they ended up using
415 dedicated paths in a custom SDN (Software Defined Networking) router
416 because there is no standards-based routing solution available.
418 2.3.2. High Reliability Stream Paths
420 On-air and other live media streams are often backed up with
421 redundant links that seamlessly act to deliver the content when the
422 primary link fails for any reason. In point-to-point systems this is
423 provided by an additional point-to-point link; the analogous
424 requirement in a packet-based system is to provide an alternate path
425 through the network such that no individual link can bring down the
426 system.
428 2.3.3. Integration of Reserved Streams into IT Networks
430 A commonly cited goal of moving to a packet based media
431 infrastructure is that costs can be reduced by using off the shelf,
432 commodity network hardware. In addition, economy of scale can be
433 realized by combining media infrastructure with IT infrastructure.
435 In keeping with these goals, stream reservation technology should be
436 compatible with existing protocols, and not compromise use of the
437 network for best effort (non-time-sensitive) traffic.
439 2.3.4. Use of Unused Reservations by Best-Effort Traffic
441 In cases where stream bandwidth is reserved but not currently used
442 (or is under-utilized) that bandwidth must be available to best-
443 effort (i.e. non-time-sensitive) traffic. For example a single
444 stream may be nailed up (reserved) for specific media content that
445 needs to be presented at different times of the day, ensuring timely
446 delivery of that content, yet in between those times the full
447 bandwidth of the network can be utilized for best-effort tasks such
448 as file transfers.
450 This also addresses a concern of IT network administrators that are
451 considering adding reserved bandwidth traffic to their networks that
452 ("users will reserve large quantities of bandwidth and then never un-
453 reserve it even though they are not using it, and soon the network
454 will have no bandwidth left").
456 2.3.5. Traffic Segregation
458 Note: It is still under WG discussion whether this topic will be
459 addressed by DetNet.
461 Sink devices may be low cost devices with limited processing power.
462 In order to not overwhelm the CPUs in these devices it is important
463 to limit the amount of traffic that these devices must process.
465 As an example, consider the use of individual seat speakers in a
466 cinema. These speakers are typically required to be cost reduced
467 since the quantities in a single theater can reach hundreds of seats.
468 Discovery protocols alone in a one thousand seat theater can generate
469 enough broadcast traffic to overwhelm a low powered CPU. Thus an
470 installation like this will benefit greatly from some type of traffic
471 segregation that can define groups of seats to reduce traffic within
472 each group. All seats in the theater must still be able to
473 communicate with a central controller.
475 There are many techniques that can be used to support this
476 requirement including (but not limited to) the following examples.
478 2.3.5.1. Packet Forwarding Rules, VLANs and Subnets
480 Packet forwarding rules can be used to eliminate some extraneous
481 streaming traffic from reaching potentially low powered sink devices,
482 however there may be other types of broadcast traffic that should be
483 eliminated using other means for example VLANs or IP subnets.
485 2.3.5.2. Multicast Addressing (IPv4 and IPv6)
487 Multicast addressing is commonly used to keep bandwidth utilization
488 of shared links to a minimum.
490 Because of the MAC Address forwarding nature of Layer 2 bridges it is
491 important that a multicast MAC address is only associated with one
492 stream. This will prevent reservations from forwarding packets from
493 one stream down a path that has no interested sinks simply because
494 there is another stream on that same path that shares the same
495 multicast MAC address.
497 Since each multicast MAC Address can represent 32 different IPv4
498 multicast addresses there must be a process put in place to make sure
499 this does not occur. Requiring use of IPv6 address can achieve this,
500 however due to their continued prevalence, solutions that are
501 effective for IPv4 installations are also required.
503 2.3.6. Latency Optimization by a Central Controller
505 A central network controller might also perform optimizations based
506 on the individual path delays, for example sinks that are closer to
507 the source can inform the controller that they can accept greater
508 latency since they will be buffering packets to match presentation
509 times of farther away sinks. The controller might then move a stream
510 reservation on a short path to a longer path in order to free up
511 bandwidth for other critical streams on that short path. See slides
512 3-5 of [SRP_LATENCY].
514 Additional optimization can be achieved in cases where sinks have
515 differing latency requirements, for example in a live outdoor concert
516 the speaker sinks have stricter latency requirements than the
517 recording hardware sinks. See slide 7 of [SRP_LATENCY].
519 2.3.7. Reduced Device Cost Due To Reduced Buffer Memory
521 Device cost can be reduced in a system with guaranteed reservations
522 with a small bounded latency due to the reduced requirements for
523 buffering (i.e. memory) on sink devices. For example, a theme park
524 might broadcast a live event across the globe via a layer 3 protocol;
525 in such cases the size of the buffers required is proportional to the
526 latency bounds and jitter caused by delivery, which depends on the
527 worst case segment of the end-to-end network path. For example on
528 todays open internet the latency is typically unacceptable for audio
529 and video streaming without many seconds of buffering. In such
530 scenarios a single gateway device at the local network that receives
531 the feed from the remote site would provide the expensive buffering
532 required to mask the latency and jitter issues associated with long
533 distance delivery. Sink devices in the local location would have no
534 additional buffering requirements, and thus no additional costs,
535 beyond those required for delivery of local content. The sink device
536 would be receiving the identical packets as those sent by the source
537 and would be unaware that there were any latency or jitter issues
538 along the path.
540 2.4. Pro Audio Asks
542 o Layer 3 routing on top of AVB (and/or other high QoS networks)
544 o Content delivery with bounded, lowest possible latency
546 o IntServ and DiffServ integration with AVB (where practical)
548 o Single network for A/V and IT traffic
550 o Standards-based, interoperable, multi-vendor
552 o IT department friendly
554 o Enterprise-wide networks (e.g. size of San Francisco but not the
555 whole Internet (yet...))
557 3. Electrical Utilities
559 3.1. Use Case Description
561 Many systems that an electrical utility deploys today rely on high
562 availability and deterministic behavior of the underlying networks.
563 Here we present use cases in Transmission, Generation and
564 Distribution, including key timing and reliability metrics. We also
565 discuss security issues and industry trends which affect the
566 architecture of next generation utility networks
568 3.1.1. Transmission Use Cases
570 3.1.1.1. Protection
572 Protection means not only the protection of human operators but also
573 the protection of the electrical equipment and the preservation of
574 the stability and frequency of the grid. If a fault occurs in the
575 transmission or distribution of electricity then severe damage can
576 occur to human operators, electrical equipment and the grid itself,
577 leading to blackouts.
579 Communication links in conjunction with protection relays are used to
580 selectively isolate faults on high voltage lines, transformers,
581 reactors and other important electrical equipment. The role of the
582 teleprotection system is to selectively disconnect a faulty part by
583 transferring command signals within the shortest possible time.
585 3.1.1.1.1. Key Criteria
587 The key criteria for measuring teleprotection performance are command
588 transmission time, dependability and security. These criteria are
589 defined by the IEC standard 60834 as follows:
591 o Transmission time (Speed): The time between the moment where state
592 changes at the transmitter input and the moment of the
593 corresponding change at the receiver output, including propagation
594 delay. Overall operating time for a teleprotection system
595 includes the time for initiating the command at the transmitting
596 end, the propagation delay over the network (including equipments)
597 and the selection and decision time at the receiving end,
598 including any additional delay due to a noisy environment.
600 o Dependability: The ability to issue and receive valid commands in
601 the presence of interference and/or noise, by minimizing the
602 probability of missing command (PMC). Dependability targets are
603 typically set for a specific bit error rate (BER) level.
605 o Security: The ability to prevent false tripping due to a noisy
606 environment, by minimizing the probability of unwanted commands
607 (PUC). Security targets are also set for a specific bit error
608 rate (BER) level.
610 Additional elements of the the teleprotection system that impact its
611 performance include:
613 o Network bandwidth
615 o Failure recovery capacity (aka resiliency)
617 3.1.1.1.2. Fault Detection and Clearance Timing
619 Most power line equipment can tolerate short circuits or faults for
620 up to approximately five power cycles before sustaining irreversible
621 damage or affecting other segments in the network. This translates
622 to total fault clearance time of 100ms. As a safety precaution,
623 however, actual operation time of protection systems is limited to
624 70- 80 percent of this period, including fault recognition time,
625 command transmission time and line breaker switching time.
627 Some system components, such as large electromechanical switches,
628 require particularly long time to operate and take up the majority of
629 the total clearance time, leaving only a 10ms window for the
630 telecommunications part of the protection scheme, independent of the
631 distance to travel. Given the sensitivity of the issue, new networks
632 impose requirements that are even more stringent: IEC standard 61850
633 limits the transfer time for protection messages to 1/4 - 1/2 cycle
634 or 4 - 8ms (for 60Hz lines) for the most critical messages.
636 3.1.1.1.3. Symmetric Channel Delay
638 Note: It is currently under WG discussion whether symmetric path
639 delays are to be guaranteed by DetNet.
641 Teleprotection channels which are differential must be synchronous,
642 which means that any delays on the transmit and receive paths must
643 match each other. Teleprotection systems ideally support zero
644 asymmetric delay; typical legacy relays can tolerate delay
645 discrepancies of up to 750us.
647 Some tools available for lowering delay variation below this
648 threshold are:
650 o For legacy systems using Time Division Multiplexing (TDM), jitter
651 buffers at the multiplexers on each end of the line can be used to
652 offset delay variation by queuing sent and received packets. The
653 length of the queues must balance the need to regulate the rate of
654 transmission with the need to limit overall delay, as larger
655 buffers result in increased latency.
657 o For jitter-prone IP packet networks, traffic management tools can
658 ensure that the teleprotection signals receive the highest
659 transmission priority to minimize jitter.
661 o Standard packet-based synchronization technologies, such as
662 1588-2008 Precision Time Protocol (PTP) and Synchronous Ethernet
663 (Sync-E), can help keep networks stable by maintaining a highly
664 accurate clock source on the various network devices.
666 3.1.1.1.4. Teleprotection Network Requirements (IEC 61850)
668 The following table captures the main network metrics as based on the
669 IEC 61850 standard.
671 +-----------------------------+-------------------------------------+
672 | Teleprotection Requirement | Attribute |
673 +-----------------------------+-------------------------------------+
674 | One way maximum delay | 4-10 ms |
675 | Asymetric delay required | Yes |
676 | Maximum jitter | less than 250 us (750 us for legacy |
677 | | IED) |
678 | Topology | Point to point, point to Multi- |
679 | | point |
680 | Availability | 99.9999 |
681 | precise timing required | Yes |
682 | Recovery time on node | less than 50ms - hitless |
683 | failure | |
684 | performance management | Yes, Mandatory |
685 | Redundancy | Yes |
686 | Packet loss | 0.1% to 1% |
687 +-----------------------------+-------------------------------------+
689 Table 1: Teleprotection network requirements
691 3.1.1.1.5. Inter-Trip Protection scheme
693 "Inter-tripping" is the signal-controlled tripping of a circuit
694 breaker to complete the isolation of a circuit or piece of apparatus
695 in concert with the tripping of other circuit breakers.
697 +--------------------------------+----------------------------------+
698 | Inter-Trip protection | Attribute |
699 | Requirement | |
700 +--------------------------------+----------------------------------+
701 | One way maximum delay | 5 ms |
702 | Asymetric delay required | No |
703 | Maximum jitter | Not critical |
704 | Topology | Point to point, point to Multi- |
705 | | point |
706 | Bandwidth | 64 Kbps |
707 | Availability | 99.9999 |
708 | precise timing required | Yes |
709 | Recovery time on node failure | less than 50ms - hitless |
710 | performance management | Yes, Mandatory |
711 | Redundancy | Yes |
712 | Packet loss | 0.1% |
713 +--------------------------------+----------------------------------+
715 Table 2: Inter-Trip protection network requirements
717 3.1.1.1.6. Current Differential Protection Scheme
719 Current differential protection is commonly used for line protection,
720 and is typical for protecting parallel circuits. At both end of the
721 lines the current is measured by the differential relays, and both
722 relays will trip the circuit breaker if the current going into the
723 line does not equal the current going out of the line. This type of
724 protection scheme assumes some form of communications being present
725 between the relays at both end of the line, to allow both relays to
726 compare measured current values. Line differential protection
727 schemes assume a very low telecommunications delay between both
728 relays, often as low as 5ms. Moreover, as those systems are often
729 not time-synchronized, they also assume symmetric telecommunications
730 paths with constant delay, which allows comparing current measurement
731 values taken at the exact same time.
733 +----------------------------------+--------------------------------+
734 | Current Differential protection | Attribute |
735 | Requirement | |
736 +----------------------------------+--------------------------------+
737 | One way maximum delay | 5 ms |
738 | Asymetric delay Required | Yes |
739 | Maximum jitter | less than 250 us (750us for |
740 | | legacy IED) |
741 | Topology | Point to point, point to |
742 | | Multi-point |
743 | Bandwidth | 64 Kbps |
744 | Availability | 99.9999 |
745 | precise timing required | Yes |
746 | Recovery time on node failure | less than 50ms - hitless |
747 | performance management | Yes, Mandatory |
748 | Redundancy | Yes |
749 | Packet loss | 0.1% |
750 +----------------------------------+--------------------------------+
752 Table 3: Current Differential Protection metrics
754 3.1.1.1.7. Distance Protection Scheme
756 Distance (Impedance Relay) protection scheme is based on voltage and
757 current measurements. The network metrics are similar (but not
758 identical to) Current Differential protection.
760 +-------------------------------+-----------------------------------+
761 | Distance protection | Attribute |
762 | Requirement | |
763 +-------------------------------+-----------------------------------+
764 | One way maximum delay | 5 ms |
765 | Asymetric delay Required | No |
766 | Maximum jitter | Not critical |
767 | Topology | Point to point, point to Multi- |
768 | | point |
769 | Bandwidth | 64 Kbps |
770 | Availability | 99.9999 |
771 | precise timing required | Yes |
772 | Recovery time on node failure | less than 50ms - hitless |
773 | performance management | Yes, Mandatory |
774 | Redundancy | Yes |
775 | Packet loss | 0.1% |
776 +-------------------------------+-----------------------------------+
778 Table 4: Distance Protection requirements
780 3.1.1.1.8. Inter-Substation Protection Signaling
782 This use case describes the exchange of Sampled Value and/or GOOSE
783 (Generic Object Oriented Substation Events) message between
784 Intelligent Electronic Devices (IED) in two substations for
785 protection and tripping coordination. The two IEDs are in a master-
786 slave mode.
788 The Current Transformer or Voltage Transformer (CT/VT) in one
789 substation sends the sampled analog voltage or current value to the
790 Merging Unit (MU) over hard wire. The MU sends the time-synchronized
791 61850-9-2 sampled values to the slave IED. The slave IED forwards
792 the information to the Master IED in the other substation. The
793 master IED makes the determination (for example based on sampled
794 value differentials) to send a trip command to the originating IED.
795 Once the slave IED/Relay receives the GOOSE trip for breaker
796 tripping, it opens the breaker. It then sends a confirmation message
797 back to the master. All data exchanges between IEDs are either
798 through Sampled Value and/or GOOSE messages.
800 +----------------------------------+--------------------------------+
801 | Inter-Substation 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 |
808 | | Multi-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 | 1% |
816 +----------------------------------+--------------------------------+
818 Table 5: Inter-Substation Protection requirements
820 3.1.1.2. Intra-Substation Process Bus Communications
822 This use case describes the data flow from the CT/VT to the IEDs in
823 the substation via the MU. The CT/VT in the substation send the
824 analog voltage or current values to the MU over hard wire. The MU
825 converts the analog values into digital format (typically time-
826 synchronized Sampled Values as specified by IEC 61850-9-2) and sends
827 them to the IEDs in the substation. The GPS Master Clock can send
828 1PPS or IRIG-B format to the MU through a serial port or IEEE 1588
829 protocol via a network. Process bus communication using 61850
830 simplifies connectivity within the substation and removes the
831 requirement for multiple serial connections and removes the slow
832 serial bus architectures that are typically used. This also ensures
833 increased flexibility and increased speed with the use of multicast
834 messaging between multiple devices.
836 +----------------------------------+--------------------------------+
837 | Intra-Substation protection | Attribute |
838 | Requirement | |
839 +----------------------------------+--------------------------------+
840 | One way maximum delay | 5 ms |
841 | Asymetric delay Required | No |
842 | Maximum jitter | Not critical |
843 | Topology | Point to point, point to |
844 | | Multi-point |
845 | Bandwidth | 64 Kbps |
846 | Availability | 99.9999 |
847 | precise timing required | Yes |
848 | Recovery time on Node failure | less than 50ms - hitless |
849 | performance management | Yes, Mandatory |
850 | Redundancy | Yes - No |
851 | Packet loss | 0.1% |
852 +----------------------------------+--------------------------------+
854 Table 6: Intra-Substation Protection requirements
856 3.1.1.3. Wide Area Monitoring and Control Systems
858 The application of synchrophasor measurement data from Phasor
859 Measurement Units (PMU) to Wide Area Monitoring and Control Systems
860 promises to provide important new capabilities for improving system
861 stability. Access to PMU data enables more timely situational
862 awareness over larger portions of the grid than what has been
863 possible historically with normal SCADA (Supervisory Control and Data
864 Acquisition) data. Handling the volume and real-time nature of
865 synchrophasor data presents unique challenges for existing
866 application architectures. Wide Area management System (WAMS) makes
867 it possible for the condition of the bulk power system to be observed
868 and understood in real-time so that protective, preventative, or
869 corrective action can be taken. Because of the very high sampling
870 rate of measurements and the strict requirement for time
871 synchronization of the samples, WAMS has stringent telecommunications
872 requirements in an IP network that are captured in the following
873 table:
875 +----------------------+--------------------------------------------+
876 | WAMS Requirement | Attribute |
877 +----------------------+--------------------------------------------+
878 | One way maximum | 50 ms |
879 | delay | |
880 | Asymetric delay | No |
881 | Required | |
882 | Maximum jitter | Not critical |
883 | Topology | Point to point, point to Multi-point, |
884 | | Multi-point to Multi-point |
885 | Bandwidth | 100 Kbps |
886 | Availability | 99.9999 |
887 | precise timing | Yes |
888 | required | |
889 | Recovery time on | less than 50ms - hitless |
890 | Node failure | |
891 | performance | Yes, Mandatory |
892 | management | |
893 | Redundancy | Yes |
894 | Packet loss | 1% |
895 | Consecutive Packet | At least 1 packet per application cycle |
896 | Loss | must be received. |
897 +----------------------+--------------------------------------------+
899 Table 7: WAMS Special Communication Requirements
901 3.1.1.4. IEC 61850 WAN engineering guidelines requirement
902 classification
904 The IEC (International Electrotechnical Commission) has recently
905 published a Technical Report which offers guidelines on how to define
906 and deploy Wide Area Networks for the interconnections of electric
907 substations, generation plants and SCADA operation centers. The IEC
908 61850-90-12 is providing a classification of WAN communication
909 requirements into 4 classes. Table 8 summarizes these requirements:
911 +----------------+------------+------------+------------+-----------+
912 | WAN | Class WA | Class WB | Class WC | Class WD |
913 | Requirement | | | | |
914 +----------------+------------+------------+------------+-----------+
915 | Application | EHV (Extra | HV (High | MV (Medium | General |
916 | field | High | Voltage) | Voltage) | purpose |
917 | | Voltage) | | | |
918 | Latency | 5 ms | 10 ms | 100 ms | > 100 ms |
919 | Jitter | 10 us | 100 us | 1 ms | 10 ms |
920 | Latency | 100 us | 1 ms | 10 ms | 100 ms |
921 | Asymetry | | | | |
922 | Time Accuracy | 1 us | 10 us | 100 us | 10 to 100 |
923 | | | | | ms |
924 | Bit Error rate | 10-7 to | 10-5 to | 10-3 | |
925 | | 10-6 | 10-4 | | |
926 | Unavailability | 10-7 to | 10-5 to | 10-3 | |
927 | | 10-6 | 10-4 | | |
928 | Recovery delay | Zero | 50 ms | 5 s | 50 s |
929 | Cyber security | extremely | High | Medium | Medium |
930 | | high | | | |
931 +----------------+------------+------------+------------+-----------+
933 Table 8: 61850-90-12 Communication Requirements; Courtesy of IEC
935 3.1.2. Generation Use Case
937 Energy generation systems are complex infrastructures that require
938 control of both the generated power and the generation
939 infrastructure.
941 3.1.2.1. Control of the Generated Power
943 The electrical power generation frequency must be maintained within a
944 very narrow band. Deviations from the acceptable frequency range are
945 detected and the required signals are sent to the power plants for
946 frequency regulation.
948 Automatic Generation Control (AGC) is a system for adjusting the
949 power output of generators at different power plants, in response to
950 changes in the load.
952 +---------------------------------------------------+---------------+
953 | FCAG (Frequency Control Automatic Generation) | Attribute |
954 | Requirement | |
955 +---------------------------------------------------+---------------+
956 | One way maximum delay | 500 ms |
957 | Asymetric delay Required | No |
958 | Maximum jitter | Not critical |
959 | Topology | Point to |
960 | | point |
961 | Bandwidth | 20 Kbps |
962 | Availability | 99.999 |
963 | precise timing required | Yes |
964 | Recovery time on Node failure | N/A |
965 | performance management | Yes, |
966 | | Mandatory |
967 | Redundancy | Yes |
968 | Packet loss | 1% |
969 +---------------------------------------------------+---------------+
971 Table 9: FCAG Communication Requirements
973 3.1.2.2. Control of the Generation Infrastructure
975 The control of the generation infrastructure combines requirements
976 from industrial automation systems and energy generation systems. In
977 this section we present the use case of the control of the generation
978 infrastructure of a wind turbine.
980 |
981 |
982 | +-----------------+
983 | | +----+ |
984 | | |WTRM| WGEN |
985 WROT x==|===| | |
986 | | +----+ WCNV|
987 | |WNAC |
988 | +---+---WYAW---+--+
989 | | |
990 | | | +----+
991 |WTRF | |WMET|
992 | | | |
993 Wind Turbine | +--+-+
994 Controller | |
995 WTUR | | |
996 WREP | | |
997 WSLG | | |
998 WALG | WTOW | |
1000 Figure 1: Wind Turbine Control Network
1002 Figure 1 presents the subsystems that operate a wind turbine. These
1003 subsystems include
1005 o WROT (Rotor Control)
1007 o WNAC (Nacelle Control) (nacelle: housing containing the generator)
1009 o WTRM (Transmission Control)
1011 o WGEN (Generator)
1013 o WYAW (Yaw Controller) (of the tower head)
1015 o WCNV (In-Turbine Power Converter)
1017 o WMET (External Meteorological Station providing real time
1018 information to the controllers of the tower)
1020 Traffic characteristics relevant for the network planning and
1021 dimensioning process in a wind turbine scenario are listed below.
1022 The values in this section are based mainly on the relevant
1023 references [Ahm14] and [Spe09]. Each logical node (Figure 1) is a
1024 part of the metering network and produces analog measurements and
1025 status information which must comply with their respective data rate
1026 constraints.
1028 +-----------+--------+--------+-------------+---------+-------------+
1029 | Subsystem | Sensor | Analog | Data Rate | Status | Data rate |
1030 | | Count | Sample | (bytes/sec) | Sample | (bytes/sec) |
1031 | | | Count | | Count | |
1032 +-----------+--------+--------+-------------+---------+-------------+
1033 | WROT | 14 | 9 | 642 | 5 | 10 |
1034 | WTRM | 18 | 10 | 2828 | 8 | 16 |
1035 | WGEN | 14 | 12 | 73764 | 2 | 4 |
1036 | WCNV | 14 | 12 | 74060 | 2 | 4 |
1037 | WTRF | 12 | 5 | 73740 | 2 | 4 |
1038 | WNAC | 12 | 9 | 112 | 3 | 6 |
1039 | WYAW | 7 | 8 | 220 | 4 | 8 |
1040 | WTOW | 4 | 1 | 8 | 3 | 6 |
1041 | WMET | 7 | 7 | 228 | - | - |
1042 +-----------+--------+--------+-------------+---------+-------------+
1044 Table 10: Wind Turbine Data Rate Constraints
1046 Quality of Service (QoS) constraints for different services are
1047 presented in Table 11. These constraints are defined by IEEE 1646
1048 standard [IEEE1646] and IEC 61400 standard [IEC61400].
1050 +---------------------+---------+-------------+---------------------+
1051 | Service | Latency | Reliability | Packet Loss Rate |
1052 +---------------------+---------+-------------+---------------------+
1053 | Analogue measure | 16 ms | 99.99% | < 10-6 |
1054 | Status information | 16 ms | 99.99% | < 10-6 |
1055 | Protection traffic | 4 ms | 100.00% | < 10-9 |
1056 | Reporting and | 1 s | 99.99% | < 10-6 |
1057 | logging | | | |
1058 | Video surveillance | 1 s | 99.00% | No specific |
1059 | | | | requirement |
1060 | Internet connection | 60 min | 99.00% | No specific |
1061 | | | | requirement |
1062 | Control traffic | 16 ms | 100.00% | < 10-9 |
1063 | Data polling | 16 ms | 99.99% | < 10-6 |
1064 +---------------------+---------+-------------+---------------------+
1066 Table 11: Wind Turbine Reliability and Latency Constraints
1068 3.1.2.2.1. Intra-Domain Network Considerations
1070 A wind turbine is composed of a large set of subsystems including
1071 sensors and actuators which require time-critical operation. The
1072 reliability and latency constraints of these different subsystems is
1073 shown in Table 11. These subsystems are connected to an intra-domain
1074 network which is used to monitor and control the operation of the
1075 turbine and connect it to the SCADA subsystems. The different
1076 components are interconnected using fiber optics, industrial buses,
1077 industrial Ethernet, EtherCat, or a combination of them. Industrial
1078 signaling and control protocols such as Modbus, Profibus, Profinet
1079 and EtherCat are used directly on top of the Layer 2 transport or
1080 encapsulated over TCP/IP.
1082 The Data collected from the sensors and condition monitoring systems
1083 is multiplexed onto fiber cables for transmission to the base of the
1084 tower, and to remote control centers. The turbine controller
1085 continuously monitors the condition of the wind turbine and collects
1086 statistics on its operation. This controller also manages a large
1087 number of switches, hydraulic pumps, valves, and motors within the
1088 wind turbine.
1090 There is usually a controller both at the bottom of the tower and in
1091 the nacelle. The communication between these two controllers usually
1092 takes place using fiber optics instead of copper links. Sometimes, a
1093 third controller is installed in the hub of the rotor and manages the
1094 pitch of the blades. That unit usually communicates with the nacelle
1095 unit using serial communications.
1097 3.1.2.2.2. Inter-Domain network considerations
1099 A remote control center belonging to a grid operator regulates the
1100 power output, enables remote actuation, and monitors the health of
1101 one or more wind parks in tandem. It connects to the local control
1102 center in a wind park over the Internet (Figure 2) via firewalls at
1103 both ends. The AS path between the local control center and the Wind
1104 Park typically involves several ISPs at different tiers. For
1105 example, a remote control center in Denmark can regulate a wind park
1106 in Greece over the normal public AS path between the two locations.
1108 The remote control center is part of the SCADA system, setting the
1109 desired power output to the wind park and reading back the result
1110 once the new power output level has been set. Traffic between the
1111 remote control center and the wind park typically consists of
1112 protocols like IEC 60870-5-104 [IEC-60870-5-104], OPC XML-DA
1113 [OPCXML], Modbus [MODBUS], and SNMP [RFC3411]. Currently, traffic
1114 flows between the wind farm and the remote control center are best
1115 effort. QoS requirements are not strict, so no SLAs or service
1116 provisioning mechanisms (e.g., VPN) are employed. In case of events
1117 like equipment failure, tolerance for alarm delay is on the order of
1118 minutes, due to redundant systems already in place.
1120 +--------------+
1121 | |
1122 | |
1123 | Wind Park #1 +----+
1124 | | | XXXXXX
1125 | | | X XXXXXXXX +----------------+
1126 +--------------+ | XXXX X XXXXX | |
1127 +---+ XXX | Remote Control |
1128 XXX Internet +----+ Center |
1129 +----+X XXX | |
1130 +--------------+ | XXXXXXX XX | |
1131 | | | XX XXXXXXX +----------------+
1132 | | | XXXXX
1133 | Wind Park #2 +----+
1134 | |
1135 | |
1136 +--------------+
1138 Figure 2: Wind Turbine Control via Internet
1140 We expect future use cases which require bounded latency, bounded
1141 jitter and extraordinary low packet loss for inter-domain traffic
1142 flows due to the softwarization and virtualization of core wind farm
1143 equipment (e.g. switches, firewalls and SCADA server components).
1144 These factors will create opportunities for service providers to
1145 install new services and dynamically manage them from remote
1146 locations. For example, to enable fail-over of a local SCADA server,
1147 a SCADA server in another wind farm site (under the administrative
1148 control of the same operator) could be utilized temporarily
1149 (Figure 3). In that case local traffic would be forwarded to the
1150 remote SCADA server and existing intra-domain QoS and timing
1151 parameters would have to be met for inter-domain traffic flows.
1153 +--------------+
1154 | |
1155 | |
1156 | Wind Park #1 +----+
1157 | | | XXXXXX
1158 | | | X XXXXXXXX +----------------+
1159 +--------------+ | XXXX XXXXX | |
1160 +---+ Operator XXX | Remote Control |
1161 XXX Administered +----+ Center |
1162 +----+X WAN XXX | |
1163 +--------------+ | XXXXXXX XX | |
1164 | | | XX XXXXXXX +----------------+
1165 | | | XXXXX
1166 | Wind Park #2 +----+
1167 | |
1168 | |
1169 +--------------+
1171 Figure 3: Wind Turbine Control via Operator Administered WAN
1173 3.1.3. Distribution use case
1175 3.1.3.1. Fault Location Isolation and Service Restoration (FLISR)
1177 Fault Location, Isolation, and Service Restoration (FLISR) refers to
1178 the ability to automatically locate the fault, isolate the fault, and
1179 restore service in the distribution network. This will likely be the
1180 first widespread application of distributed intelligence in the grid.
1182 Static power switch status (open/closed) in the network dictates the
1183 power flow to secondary substations. Reconfiguring the network in
1184 the event of a fault is typically done manually on site to energize/
1185 de-energize alternate paths. Automating the operation of substation
1186 switchgear allows the flow of power to be altered automatically under
1187 fault conditions.
1189 FLISR can be managed centrally from a Distribution Management System
1190 (DMS) or executed locally through distributed control via intelligent
1191 switches and fault sensors.
1193 +----------------------+--------------------------------------------+
1194 | FLISR Requirement | Attribute |
1195 +----------------------+--------------------------------------------+
1196 | One way maximum | 80 ms |
1197 | delay | |
1198 | Asymetric delay | No |
1199 | Required | |
1200 | Maximum jitter | 40 ms |
1201 | Topology | Point to point, point to Multi-point, |
1202 | | Multi-point to Multi-point |
1203 | Bandwidth | 64 Kbps |
1204 | Availability | 99.9999 |
1205 | precise timing | Yes |
1206 | required | |
1207 | Recovery time on | Depends on customer impact |
1208 | Node failure | |
1209 | performance | Yes, Mandatory |
1210 | management | |
1211 | Redundancy | Yes |
1212 | Packet loss | 0.1% |
1213 +----------------------+--------------------------------------------+
1215 Table 12: FLISR Communication Requirements
1217 3.2. Electrical Utilities Today
1219 Many utilities still rely on complex environments formed of multiple
1220 application-specific proprietary networks, including TDM networks.
1222 In this kind of environment there is no mixing of OT and IT
1223 applications on the same network, and information is siloed between
1224 operational areas.
1226 Specific calibration of the full chain is required, which is costly.
1228 This kind of environment prevents utility operations from realizing
1229 the operational efficiency benefits, visibility, and functional
1230 integration of operational information across grid applications and
1231 data networks.
1233 In addition, there are many security-related issues as discussed in
1234 the following section.
1236 3.2.1. Security Current Practices and Limitations
1238 Grid monitoring and control devices are already targets for cyber
1239 attacks, and legacy telecommunications protocols have many intrinsic
1240 network-related vulnerabilities. For example, DNP3, Modbus,
1241 PROFIBUS/PROFINET, and other protocols are designed around a common
1242 paradigm of request and respond. Each protocol is designed for a
1243 master device such as an HMI (Human Machine Interface) system to send
1244 commands to subordinate slave devices to retrieve data (reading
1245 inputs) or control (writing to outputs). Because many of these
1246 protocols lack authentication, encryption, or other basic security
1247 measures, they are prone to network-based attacks, allowing a
1248 malicious actor or attacker to utilize the request-and-respond system
1249 as a mechanism for command-and-control like functionality. Specific
1250 security concerns common to most industrial control, including
1251 utility telecommunication protocols include the following:
1253 o Network or transport errors (e.g. malformed packets or excessive
1254 latency) can cause protocol failure.
1256 o Protocol commands may be available that are capable of forcing
1257 slave devices into inoperable states, including powering-off
1258 devices, forcing them into a listen-only state, disabling
1259 alarming.
1261 o Protocol commands may be available that are capable of restarting
1262 communications and otherwise interrupting processes.
1264 o Protocol commands may be available that are capable of clearing,
1265 erasing, or resetting diagnostic information such as counters and
1266 diagnostic registers.
1268 o Protocol commands may be available that are capable of requesting
1269 sensitive information about the controllers, their configurations,
1270 or other need-to-know information.
1272 o Most protocols are application layer protocols transported over
1273 TCP; therefore it is easy to transport commands over non-standard
1274 ports or inject commands into authorized traffic flows.
1276 o Protocol commands may be available that are capable of
1277 broadcasting messages to many devices at once (i.e. a potential
1278 DoS).
1280 o Protocol commands may be available to query the device network to
1281 obtain defined points and their values (i.e. a configuration
1282 scan).
1284 o Protocol commands may be available that will list all available
1285 function codes (i.e. a function scan).
1287 These inherent vulnerabilities, along with increasing connectivity
1288 between IT an OT networks, make network-based attacks very feasible.
1290 Simple injection of malicious protocol commands provides control over
1291 the target process. Altering legitimate protocol traffic can also
1292 alter information about a process and disrupt the legitimate controls
1293 that are in place over that process. A man-in-the-middle attack
1294 could provide both control over a process and misrepresentation of
1295 data back to operator consoles.
1297 3.3. Electrical Utilities Future
1299 The business and technology trends that are sweeping the utility
1300 industry will drastically transform the utility business from the way
1301 it has been for many decades. At the core of many of these changes
1302 is a drive to modernize the electrical grid with an integrated
1303 telecommunications infrastructure. However, interoperability
1304 concerns, legacy networks, disparate tools, and stringent security
1305 requirements all add complexity to the grid transformation. Given
1306 the range and diversity of the requirements that should be addressed
1307 by the next generation telecommunications infrastructure, utilities
1308 need to adopt a holistic architectural approach to integrate the
1309 electrical grid with digital telecommunications across the entire
1310 power delivery chain.
1312 The key to modernizing grid telecommunications is to provide a
1313 common, adaptable, multi-service network infrastructure for the
1314 entire utility organization. Such a network serves as the platform
1315 for current capabilities while enabling future expansion of the
1316 network to accommodate new applications and services.
1318 To meet this diverse set of requirements, both today and in the
1319 future, the next generation utility telecommunnications network will
1320 be based on open-standards-based IP architecture. An end-to-end IP
1321 architecture takes advantage of nearly three decades of IP technology
1322 development, facilitating interoperability and device management
1323 across disparate networks and devices, as it has been already
1324 demonstrated in many mission-critical and highly secure networks.
1326 IPv6 is seen as a future telecommunications technology for the Smart
1327 Grid; the IEC (International Electrotechnical Commission) and
1328 different National Committees have mandated a specific adhoc group
1329 (AHG8) to define the migration strategy to IPv6 for all the IEC TC57
1330 power automation standards. The AHG8 has recently finalised the work
1331 on the migration strategy and the following Technical Report has been
1332 issued: IEC TR 62357-200:2015: Guidelines for migration from Internet
1333 Protocol version 4 (IPv4) to Internet Protocol version 6 (IPv6).
1335 We expect cloud-based SCADA systems to control and monitor the
1336 critical and non-critical subsystems of generation systems, for
1337 example wind farms.
1339 3.3.1. Migration to Packet-Switched Network
1341 Throughout the world, utilities are increasingly planning for a
1342 future based on smart grid applications requiring advanced
1343 telecommunications systems. Many of these applications utilize
1344 packet connectivity for communicating information and control signals
1345 across the utility's Wide Area Network (WAN), made possible by
1346 technologies such as multiprotocol label switching (MPLS). The data
1347 that traverses the utility WAN includes:
1349 o Grid monitoring, control, and protection data
1351 o Non-control grid data (e.g. asset data for condition-based
1352 monitoring)
1354 o Physical safety and security data (e.g. voice and video)
1356 o Remote worker access to corporate applications (voice, maps,
1357 schematics, etc.)
1359 o Field area network backhaul for smart metering, and distribution
1360 grid management
1362 o Enterprise traffic (email, collaboration tools, business
1363 applications)
1365 WANs support this wide variety of traffic to and from substations,
1366 the transmission and distribution grid, generation sites, between
1367 control centers, and between work locations and data centers. To
1368 maintain this rapidly expanding set of applications, many utilities
1369 are taking steps to evolve present time-division multiplexing (TDM)
1370 based and frame relay infrastructures to packet systems. Packet-
1371 based networks are designed to provide greater functionalities and
1372 higher levels of service for applications, while continuing to
1373 deliver reliability and deterministic (real-time) traffic support.
1375 3.3.2. Telecommunications Trends
1377 These general telecommunications topics are in addition to the use
1378 cases that have been addressed so far. These include both current
1379 and future telecommunications related topics that should be factored
1380 into the network architecture and design.
1382 3.3.2.1. General Telecommunications Requirements
1384 o IP Connectivity everywhere
1386 o Monitoring services everywhere and from different remote centers
1387 o Move services to a virtual data center
1389 o Unify access to applications / information from the corporate
1390 network
1392 o Unify services
1394 o Unified Communications Solutions
1396 o Mix of fiber and microwave technologies - obsolescence of SONET/
1397 SDH or TDM
1399 o Standardize grid telecommunications protocol to opened standard to
1400 ensure interoperability
1402 o Reliable Telecommunications for Transmission and Distribution
1403 Substations
1405 o IEEE 1588 time synchronization Client / Server Capabilities
1407 o Integration of Multicast Design
1409 o QoS Requirements Mapping
1411 o Enable Future Network Expansion
1413 o Substation Network Resilience
1415 o Fast Convergence Design
1417 o Scalable Headend Design
1419 o Define Service Level Agreements (SLA) and Enable SLA Monitoring
1421 o Integration of 3G/4G Technologies and future technologies
1423 o Ethernet Connectivity for Station Bus Architecture
1425 o Ethernet Connectivity for Process Bus Architecture
1427 o Protection, teleprotection and PMU (Phaser Measurement Unit) on IP
1429 3.3.2.2. Specific Network topologies of Smart Grid Applications
1431 Utilities often have very large private telecommunications networks.
1432 It covers an entire territory / country. The main purpose of the
1433 network, until now, has been to support transmission network
1434 monitoring, control, and automation, remote control of generation
1435 sites, and providing FCAPS (Fault, Configuration, Accounting,
1436 Performance, Security) services from centralized network operation
1437 centers.
1439 Going forward, one network will support operation and maintenance of
1440 electrical networks (generation, transmission, and distribution),
1441 voice and data services for ten of thousands of employees and for
1442 exchange with neighboring interconnections, and administrative
1443 services. To meet those requirements, utility may deploy several
1444 physical networks leveraging different technologies across the
1445 country: an optical network and a microwave network for instance.
1446 Each protection and automatism system between two points has two
1447 telecommunications circuits, one on each network. Path diversity
1448 between two substations is key. Regardless of the event type
1449 (hurricane, ice storm, etc.), one path shall stay available so the
1450 system can still operate.
1452 In the optical network, signals are transmitted over more than tens
1453 of thousands of circuits using fiber optic links, microwave and
1454 telephone cables. This network is the nervous system of the
1455 utility's power transmission operations. The optical network
1456 represents ten of thousands of km of cable deployed along the power
1457 lines, with individual runs as long as 280 km.
1459 3.3.2.3. Precision Time Protocol
1461 Some utilities do not use GPS clocks in generation substations. One
1462 of the main reasons is that some of the generation plants are 30 to
1463 50 meters deep under ground and the GPS signal can be weak and
1464 unreliable. Instead, atomic clocks are used. Clocks are
1465 synchronized amongst each other. Rubidium clocks provide clock and
1466 1ms timestamps for IRIG-B.
1468 Some companies plan to transition to the Precision Time Protocol
1469 (PTP, [IEEE1588]), distributing the synchronization signal over the
1470 IP/MPLS network. PTP provides a mechanism for synchronizing the
1471 clocks of participating nodes to a high degree of accuracy and
1472 precision.
1474 PTP operates based on the following assumptions:
1476 It is assumed that the network eliminates cyclic forwarding of PTP
1477 messages within each communication path (e.g. by using a spanning
1478 tree protocol).
1480 PTP is tolerant of an occasional missed message, duplicated
1481 message, or message that arrived out of order. However, PTP
1482 assumes that such impairments are relatively rare.
1484 PTP was designed assuming a multicast communication model, however
1485 PTP also supports a unicast communication model as long as the
1486 behavior of the protocol is preserved.
1488 Like all message-based time transfer protocols, PTP time accuracy
1489 is degraded by delay asymmetry in the paths taken by event
1490 messages. Asymmetry is not detectable by PTP, however, if such
1491 delays are known a priori, PTP can correct for asymmetry.
1493 IEC 61850 defines the use of IEC/IEEE 61850-9-3:2016. The title is:
1494 Precision time protocol profile for power utility automation. It is
1495 based on Annex B/IEC 62439 which offers the support of redundant
1496 attachment of clocks to Parallel Redundancy Protocol (PRP) and High-
1497 availability Seamless Redundancy (HSR) networks.
1499 3.3.3. Security Trends in Utility Networks
1501 Although advanced telecommunications networks can assist in
1502 transforming the energy industry by playing a critical role in
1503 maintaining high levels of reliability, performance, and
1504 manageability, they also introduce the need for an integrated
1505 security infrastructure. Many of the technologies being deployed to
1506 support smart grid projects such as smart meters and sensors can
1507 increase the vulnerability of the grid to attack. Top security
1508 concerns for utilities migrating to an intelligent smart grid
1509 telecommunications platform center on the following trends:
1511 o Integration of distributed energy resources
1513 o Proliferation of digital devices to enable management, automation,
1514 protection, and control
1516 o Regulatory mandates to comply with standards for critical
1517 infrastructure protection
1519 o Migration to new systems for outage management, distribution
1520 automation, condition-based maintenance, load forecasting, and
1521 smart metering
1523 o Demand for new levels of customer service and energy management
1525 This development of a diverse set of networks to support the
1526 integration of microgrids, open-access energy competition, and the
1527 use of network-controlled devices is driving the need for a converged
1528 security infrastructure for all participants in the smart grid,
1529 including utilities, energy service providers, large commercial and
1530 industrial, as well as residential customers. Securing the assets of
1531 electric power delivery systems (from the control center to the
1532 substation, to the feeders and down to customer meters) requires an
1533 end-to-end security infrastructure that protects the myriad of
1534 telecommunications assets used to operate, monitor, and control power
1535 flow and measurement.
1537 "Cyber security" refers to all the security issues in automation and
1538 telecommunications that affect any functions related to the operation
1539 of the electric power systems. Specifically, it involves the
1540 concepts of:
1542 o Integrity : data cannot be altered undetectably
1544 o Authenticity : the telecommunications parties involved must be
1545 validated as genuine
1547 o Authorization : only requests and commands from the authorized
1548 users can be accepted by the system
1550 o Confidentiality : data must not be accessible to any
1551 unauthenticated users
1553 When designing and deploying new smart grid devices and
1554 telecommunications systems, it is imperative to understand the
1555 various impacts of these new components under a variety of attack
1556 situations on the power grid. Consequences of a cyber attack on the
1557 grid telecommunications network can be catastrophic. This is why
1558 security for smart grid is not just an ad hoc feature or product,
1559 it's a complete framework integrating both physical and Cyber
1560 security requirements and covering the entire smart grid networks
1561 from generation to distribution. Security has therefore become one
1562 of the main foundations of the utility telecom network architecture
1563 and must be considered at every layer with a defense-in-depth
1564 approach. Migrating to IP based protocols is key to address these
1565 challenges for two reasons:
1567 o IP enables a rich set of features and capabilities to enhance the
1568 security posture
1570 o IP is based on open standards, which allows interoperability
1571 between different vendors and products, driving down the costs
1572 associated with implementing security solutions in OT networks.
1574 Securing OT (Operation technology) telecommunications over packet-
1575 switched IP networks follow the same principles that are foundational
1576 for securing the IT infrastructure, i.e., consideration must be given
1577 to enforcing electronic access control for both person-to-machine and
1578 machine-to-machine communications, and providing the appropriate
1579 levels of data privacy, device and platform integrity, and threat
1580 detection and mitigation.
1582 3.4. Electrical Utilities Asks
1584 o Mixed L2 and L3 topologies
1586 o Deterministic behavior
1588 o Bounded latency and jitter
1590 o Tight feedback intervals
1592 o High availability, low recovery time
1594 o Redundancy, low packet loss
1596 o Precise timing
1598 o Centralized computing of deterministic paths
1600 o Distributed configuration may also be useful
1602 4. Building Automation Systems
1604 4.1. Use Case Description
1606 A Building Automation System (BAS) manages equipment and sensors in a
1607 building for improving residents' comfort, reducing energy
1608 consumption, and responding to failures and emergencies. For
1609 example, the BAS measures the temperature of a room using sensors and
1610 then controls the HVAC (heating, ventilating, and air conditioning)
1611 to maintain a set temperature and minimize energy consumption.
1613 A BAS primarily performs the following functions:
1615 o Periodically measures states of devices, for example humidity and
1616 illuminance of rooms, open/close state of doors, FAN speed, etc.
1618 o Stores the measured data.
1620 o Provides the measured data to BAS systems and operators.
1622 o Generates alarms for abnormal state of devices.
1624 o Controls devices (e.g. turn off room lights at 10:00 PM).
1626 4.2. Building Automation Systems Today
1628 4.2.1. BAS Architecture
1630 A typical BAS architecture of today is shown in Figure 4.
1632 +----------------------------+
1633 | |
1634 | BMS HMI |
1635 | | | |
1636 | +----------------------+ |
1637 | | Management Network | |
1638 | +----------------------+ |
1639 | | | |
1640 | LC LC |
1641 | | | |
1642 | +----------------------+ |
1643 | | Field Network | |
1644 | +----------------------+ |
1645 | | | | | |
1646 | Dev Dev Dev Dev |
1647 | |
1648 +----------------------------+
1650 BMS := Building Management Server
1651 HMI := Human Machine Interface
1652 LC := Local Controller
1654 Figure 4: BAS architecture
1656 There are typically two layers of network in a BAS. The upper one is
1657 called the Management Network and the lower one is called the Field
1658 Network. In management networks an IP-based communication protocol
1659 is used, while in field networks non-IP based communication protocols
1660 ("field protocols") are mainly used. Field networks have specific
1661 timing requirements, whereas management networks can be best-effort.
1663 A Human Machine Interface (HMI) is typically a desktop PC used by
1664 operators to monitor and display device states, send device control
1665 commands to Local Controllers (LCs), and configure building schedules
1666 (for example "turn off all room lights in the building at 10:00 PM").
1668 A Building Management Server (BMS) performs the following operations.
1670 o Collect and store device states from LCs at regular intervals.
1672 o Send control values to LCs according to a building schedule.
1674 o Send an alarm signal to operators if it detects abnormal devices
1675 states.
1677 The BMS and HMI communicate with LCs via IP-based "management
1678 protocols" (see standards [bacnetip], [knx]).
1680 A LC is typically a Programmable Logic Controller (PLC) which is
1681 connected to several tens or hundreds of devices using "field
1682 protocols". An LC performs the following kinds of operations:
1684 o Measure device states and provide the information to BMS or HMI.
1686 o Send control values to devices, unilaterally or as part of a
1687 feedback control loop.
1689 There are many field protocols used today; some are standards-based
1690 and others are proprietary (see standards [lontalk], [modbus],
1691 [profibus] and [flnet]). The result is that BASs have multiple MAC/
1692 PHY modules and interfaces. This makes BASs more expensive, slower
1693 to develop, and can result in "vendor lock-in" with multiple types of
1694 management applications.
1696 4.2.2. BAS Deployment Model
1698 An example BAS for medium or large buildings is shown in Figure 5.
1699 The physical layout spans multiple floors, and there is a monitoring
1700 room where the BAS management entities are located. Each floor will
1701 have one or more LCs depending upon the number of devices connected
1702 to the field network.
1704 +--------------------------------------------------+
1705 | Floor 3 |
1706 | +----LC~~~~+~~~~~+~~~~~+ |
1707 | | | | | |
1708 | | Dev Dev Dev |
1709 | | |
1710 |--- | ------------------------------------------|
1711 | | Floor 2 |
1712 | +----LC~~~~+~~~~~+~~~~~+ Field Network |
1713 | | | | | |
1714 | | Dev Dev Dev |
1715 | | |
1716 |--- | ------------------------------------------|
1717 | | Floor 1 |
1718 | +----LC~~~~+~~~~~+~~~~~+ +-----------------|
1719 | | | | | | Monitoring Room |
1720 | | Dev Dev Dev | |
1721 | | | BMS HMI |
1722 | | Management Network | | | |
1723 | +--------------------------------+-----+ |
1724 | | |
1725 +--------------------------------------------------+
1727 Figure 5: BAS Deployment model for Medium/Large Buildings
1729 Each LC is connected to the monitoring room via the Management
1730 network, and the management functions are performed within the
1731 building. In most cases, fast Ethernet (e.g. 100BASE-T) is used for
1732 the management network. Since the management network is non-
1733 realtime, use of Ethernet without quality of service is sufficient
1734 for today's deployment.
1736 In the field network a variety of physical interfaces such as RS232C
1737 and RS485 are used, which have specific timing requirements. Thus if
1738 a field network is to be replaced with an Ethernet or wireless
1739 network, such networks must support time-critical deterministic
1740 flows.
1742 In Figure 6, another deployment model is presented in which the
1743 management system is hosted remotely. This is becoming popular for
1744 small office and residential buildings in which a standalone
1745 monitoring system is not cost-effective.
1747 +---------------+
1748 | Remote Center |
1749 | |
1750 | BMS HMI |
1751 +------------------------------------+ | | | |
1752 | Floor 2 | | +---+---+ |
1753 | +----LC~~~~+~~~~~+ Field Network| | | |
1754 | | | | | | Router |
1755 | | Dev Dev | +-------|-------+
1756 | | | |
1757 |--- | ------------------------------| |
1758 | | Floor 1 | |
1759 | +----LC~~~~+~~~~~+ | |
1760 | | | | | |
1761 | | Dev Dev | |
1762 | | | |
1763 | | Management Network | WAN |
1764 | +------------------------Router-------------+
1765 | |
1766 +------------------------------------+
1768 Figure 6: Deployment model for Small Buildings
1770 Some interoperability is possible today in the Management Network,
1771 but not in today's field networks due to their non-IP-based design.
1773 4.2.3. Use Cases for Field Networks
1775 Below are use cases for Environmental Monitoring, Fire Detection, and
1776 Feedback Control, and their implications for field network
1777 performance.
1779 4.2.3.1. Environmental Monitoring
1781 The BMS polls each LC at a maximum measurement interval of 100ms (for
1782 example to draw a historical chart of 1 second granularity with a 10x
1783 sampling interval) and then performs the operations as specified by
1784 the operator. Each LC needs to measure each of its several hundred
1785 sensors once per measurement interval. Latency is not critical in
1786 this scenario as long as all sensor values are completed in the
1787 measurement interval. Availability is expected to be 99.999 %.
1789 4.2.3.2. Fire Detection
1791 On detection of a fire, the BMS must stop the HVAC, close the fire
1792 shutters, turn on the fire sprinklers, send an alarm, etc. There are
1793 typically ~10s of sensors per LC that BMS needs to manage. In this
1794 scenario the measurement interval is 10-50ms, the communication delay
1795 is 10ms, and the availability must be 99.9999 %.
1797 4.2.3.3. Feedback Control
1799 BAS systems utilize feedback control in various ways; the most time-
1800 critial is control of DC motors, which require a short feedback
1801 interval (1-5ms) with low communication delay (10ms) and jitter
1802 (1ms). The feedback interval depends on the characteristics of the
1803 device and a target quality of control value. There are typically
1804 ~10s of such devices per LC.
1806 Communication delay is expected to be less than 10 ms, jitter less
1807 than 1 sec while the availability must be 99.9999% .
1809 4.2.4. Security Considerations
1811 When BAS field networks were developed it was assumed that the field
1812 networks would always be physically isolated from external networks
1813 and therefore security was not a concern. In today's world many BASs
1814 are managed remotely and are thus connected to shared IP networks and
1815 so security is definitely a concern, yet security features are not
1816 available in the majority of BAS field network deployments .
1818 The management network, being an IP-based network, has the protocols
1819 available to enable network security, but in practice many BAS
1820 systems do not implement even the available security features such as
1821 device authentication or encryption for data in transit.
1823 4.3. BAS Future
1825 In the future we expect more fine-grained environmental monitoring
1826 and lower energy consumption, which will require more sensors and
1827 devices, thus requiring larger and more complex building networks.
1829 We expect building networks to be connected to or converged with
1830 other networks (Enterprise network, Home network, and Internet).
1832 Therefore better facilities for network management, control,
1833 reliability and security are critical in order to improve resident
1834 and operator convenience and comfort. For example the ability to
1835 monitor and control building devices via the internet would enable
1836 (for example) control of room lights or HVAC from a resident's
1837 desktop PC or phone application.
1839 4.4. BAS Asks
1841 The community would like to see an interoperable protocol
1842 specification that can satisfy the timing, security, availability and
1843 QoS constraints described above, such that the resulting converged
1844 network can replace the disparate field networks. Ideally this
1845 connectivity could extend to the open Internet.
1847 This would imply an architecture that can guarantee
1849 o Low communication delays (from <10ms to 100ms in a network of
1850 several hundred devices)
1852 o Low jitter (< 1 ms)
1854 o Tight feedback intervals (1ms - 10ms)
1856 o High network availability (up to 99.9999% )
1858 o Availability of network data in disaster scenario
1860 o Authentication between management and field devices (both local
1861 and remote)
1863 o Integrity and data origin authentication of communication data
1864 between field and management devices
1866 o Confidentiality of data when communicated to a remote device
1868 5. Wireless for Industrial
1870 5.1. Use Case Description
1872 Wireless networks are useful for industrial applications, for example
1873 when portable, fast-moving or rotating objects are involved, and for
1874 the resource-constrained devices found in the Internet of Things
1875 (IoT).
1877 Such network-connected sensors, actuators, control loops (etc.)
1878 typically require that the underlying network support real-time
1879 quality of service (QoS), as well as specific classes of other
1880 network properties such as reliability, redundancy, and security.
1882 These networks may also contain very large numbers of devices, for
1883 example for factories, "big data" acquisition, and the IoT. Given
1884 the large numbers of devices installed, and the potential
1885 pervasiveness of the IoT, this is a huge and very cost-sensitive
1886 market. For example, a 1% cost reduction in some areas could save
1887 $100B
1889 5.1.1. Network Convergence using 6TiSCH
1891 Some wireless network technologies support real-time QoS, and are
1892 thus useful for these kinds of networks, but others do not. For
1893 example WiFi is pervasive but does not provide guaranteed timing or
1894 delivery of packets, and thus is not useful in this context.
1896 In this use case we focus on one specific wireless network technology
1897 which does provide the required deterministic QoS, which is "IPv6
1898 over the TSCH mode of IEEE 802.15.4e" (6TiSCH, where TSCH stands for
1899 "Time-Slotted Channel Hopping", see [I-D.ietf-6tisch-architecture],
1900 [IEEE802154], [IEEE802154e], and [RFC7554]).
1902 There are other deterministic wireless busses and networks available
1903 today, however they are imcompatible with each other, and
1904 incompatible with IP traffic (for example [ISA100], [WirelessHART]).
1906 Thus the primary goal of this use case is to apply 6TiSCH as a
1907 converged IP- and standards-based wireless network for industrial
1908 applications, i.e. to replace multiple proprietary and/or
1909 incompatible wireless networking and wireless network management
1910 standards.
1912 5.1.2. Common Protocol Development for 6TiSCH
1914 Today there are a number of protocols required by 6TiSCH which are
1915 still in development, and a second intent of this use case is to
1916 highlight the ways in which these "missing" protocols share goals in
1917 common with DetNet. Thus it is possible that some of the protocol
1918 technology developed for DetNet will also be applicable to 6TiSCH.
1920 These protocol goals are identified here, along with their
1921 relationship to DetNet. It is likely that ultimately the resulting
1922 protocols will not be identical, but will share design principles
1923 which contribute to the eficiency of enabling both DetNet and 6TiSCH.
1925 One such commonality is that although at a different time scale, in
1926 both TSN [IEEE802.1TSNTG] and TSCH a packet crosses the network from
1927 node to node follows a precise schedule, as a train that leaves
1928 intermediate stations at precise times along its path. This kind of
1929 operation reduces collisions, saves energy, and enables engineering
1930 the network for deterministic properties.
1932 Another commonality is remote monitoring and scheduling management of
1933 a TSCH network by a Path Computation Element (PCE) and Network
1934 Management Entity (NME). The PCE/NME manage timeslots and device
1935 resources in a manner that minimizes the interaction with and the
1936 load placed on resource-constrained devices. For example, a tiny IoT
1937 device may have just enough buffers to store one or a few IPv6
1938 packets, and will have limited bandwidth between peers such that it
1939 can maintain only a small amount of peer information, and will not be
1940 able to store many packets waiting to be forwarded. It is
1941 advantageous then for it to only be required to carry out the
1942 specific behavior assigned to it by the PCE/NME (as opposed to
1943 maintaining its own IP stack, for example).
1945 Note: Current WG discussion indicates that some peer-to-peer
1946 communication must be assumed, i.e. the PCE may communicate only
1947 indirectly with any given device, enabling hierarchical configuration
1948 of the system.
1950 6TiSCH depends on [PCE] and [I-D.finn-detnet-architecture].
1952 6TiSCH also depends on the fact that DetNet will maintain consistency
1953 with [IEEE802.1TSNTG].
1955 5.2. Wireless Industrial Today
1957 Today industrial wireless is accomplished using multiple
1958 deterministic wireless networks which are incompatible with each
1959 other and with IP traffic.
1961 6TiSCH is not yet fully specified, so it cannot be used in today's
1962 applications.
1964 5.3. Wireless Industrial Future
1966 5.3.1. Unified Wireless Network and Management
1968 We expect DetNet and 6TiSCH together to enable converged transport of
1969 deterministic and best-effort traffic flows between real-time
1970 industrial devices and wide area networks via IP routing. A high
1971 level view of a basic such network is shown in Figure 7.
1973 ---+-------- ............ ------------
1974 | External Network |
1975 | +-----+
1976 +-----+ | NME |
1977 | | LLN Border | |
1978 | | router +-----+
1979 +-----+
1980 o o o
1981 o o o o
1982 o o LLN o o o
1983 o o o o
1984 o
1986 Figure 7: Basic 6TiSCH Network
1988 Figure 8 shows a backbone router federating multiple synchronized
1989 6TiSCH subnets into a single subnet connected to the external
1990 network.
1992 ---+-------- ............ ------------
1993 | External Network |
1994 | +-----+
1995 | +-----+ | NME |
1996 +-----+ | +-----+ | |
1997 | | Router | | PCE | +-----+
1998 | | +--| |
1999 +-----+ +-----+
2000 | |
2001 | Subnet Backbone |
2002 +--------------------+------------------+
2003 | | |
2004 +-----+ +-----+ +-----+
2005 | | Backbone | | Backbone | | Backbone
2006 o | | router | | router | | router
2007 +-----+ +-----+ +-----+
2008 o o o o o
2009 o o o o o o o o o o o
2010 o o o LLN o o o o
2011 o o o o o o o o o o o o
2013 Figure 8: Extended 6TiSCH Network
2015 The backbone router must ensure end-to-end deterministic behavior
2016 between the LLN and the backbone. We would like to see this
2017 accomplished in conformance with the work done in
2018 [I-D.finn-detnet-architecture] with respect to Layer-3 aspects of
2019 deterministic networks that span multiple Layer-2 domains.
2021 The PCE must compute a deterministic path end-to-end across the TSCH
2022 network and IEEE802.1 TSN Ethernet backbone, and DetNet protocols are
2023 expected to enable end-to-end deterministic forwarding.
2025 +-----+
2026 | IoT |
2027 | G/W |
2028 +-----+
2029 ^ <---- Elimination
2030 | |
2031 Track branch | |
2032 +-------+ +--------+ Subnet Backbone
2033 | |
2034 +--|--+ +--|--+
2035 | | | Backbone | | | Backbone
2036 o | | | router | | | router
2037 +--/--+ +--|--+
2038 o / o o---o----/ o
2039 o o---o--/ o o o o o
2040 o \ / o o LLN o
2041 o v <---- Replication
2042 o
2044 Figure 9: 6TiSCH Network with PRE
2046 5.3.1.1. PCE and 6TiSCH ARQ Retries
2048 Note: The possible use of ARQ techniques in DetNet is currently
2049 considered a possible design alternative.
2051 6TiSCH uses the IEEE802.15.4 Automatic Repeat-reQuest (ARQ) mechanism
2052 to provide higher reliability of packet delivery. ARQ is related to
2053 packet replication and elimination because there are two independent
2054 paths for packets to arrive at the destination, and if an expected
2055 packed does not arrive on one path then it checks for the packet on
2056 the second path.
2058 Although to date this mechanism is only used by wireless networks,
2059 this may be a technique that would be appropriate for DetNet and so
2060 aspects of the enabling protocol could be co-developed.
2062 For example, in Figure 9, a Track is laid out from a field device in
2063 a 6TiSCH network to an IoT gateway that is located on a IEEE802.1 TSN
2064 backbone.
2066 In ARQ the Replication function in the field device sends a copy of
2067 each packet over two different branches, and the PCE schedules each
2068 hop of both branches so that the two copies arrive in due time at the
2069 gateway. In case of a loss on one branch, hopefully the other copy
2070 of the packet still arrives within the allocated time. If two copies
2071 make it to the IoT gateway, the Elimination function in the gateway
2072 ignores the extra packet and presents only one copy to upper layers.
2074 At each 6TiSCH hop along the Track, the PCE may schedule more than
2075 one timeSlot for a packet, so as to support Layer-2 retries (ARQ).
2077 In current deployments, a TSCH Track does not necessarily support PRE
2078 but is systematically multi-path. This means that a Track is
2079 scheduled so as to ensure that each hop has at least two forwarding
2080 solutions, and the forwarding decision is to try the preferred one
2081 and use the other in case of Layer-2 transmission failure as detected
2082 by ARQ.
2084 5.3.2. Schedule Management by a PCE
2086 A common feature of 6TiSCH and DetNet is the action of a PCE to
2087 configure paths through the network. Specifically, what is needed is
2088 a protocol and data model that the PCE will use to get/set the
2089 relevant configuration from/to the devices, as well as perform
2090 operations on the devices. We expect that this protocol will be
2091 developed by DetNet with consideration for its reuse by 6TiSCH. The
2092 remainder of this section provides a bit more context from the 6TiSCH
2093 side.
2095 5.3.2.1. PCE Commands and 6TiSCH CoAP Requests
2097 The 6TiSCH device does not expect to place the request for bandwidth
2098 between itself and another device in the network. Rather, an
2099 operation control system invoked through a human interface specifies
2100 the required traffic specification and the end nodes (in terms of
2101 latency and reliability). Based on this information, the PCE must
2102 compute a path between the end nodes and provision the network with
2103 per-flow state that describes the per-hop operation for a given
2104 packet, the corresponding timeslots, and the flow identification that
2105 enables recognizing that a certain packet belongs to a certain path,
2106 etc.
2108 For a static configuration that serves a certain purpose for a long
2109 period of time, it is expected that a node will be provisioned in one
2110 shot with a full schedule, which incorporates the aggregation of its
2111 behavior for multiple paths. 6TiSCH expects that the programing of
2112 the schedule will be done over COAP as discussed in
2113 [I-D.ietf-6tisch-coap].
2115 6TiSCH expects that the PCE commands will be mapped back and forth
2116 into CoAP by a gateway function at the edge of the 6TiSCH network.
2117 For instance, it is possible that a mapping entity on the backbone
2118 transforms a non-CoAP protocol such as PCEP into the RESTful
2119 interfaces that the 6TiSCH devices support. This architecture will
2120 be refined to comply with DetNet [I-D.finn-detnet-architecture] when
2121 the work is formalized. Related information about 6TiSCH can be
2122 found at [I-D.ietf-6tisch-6top-interface] and RPL [RFC6550].
2124 A protocol may be used to update the state in the devices during
2125 runtime, for example if it appears that a path through the network
2126 has ceased to perform as expected, but in 6TiSCH that flow was not
2127 designed and no protocol was selected. We would like to see DetNet
2128 define the appropriate end-to-end protocols to be used in that case.
2129 The implication is that these state updates take place once the
2130 system is configured and running, i.e. they are not limited to the
2131 initial communication of the configuration of the system.
2133 A "slotFrame" is the base object that a PCE would manipulate to
2134 program a schedule into an LLN node ([I-D.ietf-6tisch-architecture]).
2136 We would like to see the PCE read energy data from devices, and
2137 compute paths that will implement policies on how energy in devices
2138 is consumed, for instance to ensure that the spent energy does not
2139 exceeded the available energy over a period of time. Note: this
2140 statement implies that an extensible protocol for communicating
2141 device info to the PCE and enabling the PCE to act on it will be part
2142 of the DetNet architecture, however for subnets with specific
2143 protocols (e.g. CoAP) a gateway may be required.
2145 6TiSCH devices can discover their neighbors over the radio using a
2146 mechanism such as beacons, but even though the neighbor information
2147 is available in the 6TiSCH interface data model, 6TiSCH does not
2148 describe a protocol to proactively push the neighborhood information
2149 to a PCE. We would like to see DetNet define such a protocol; one
2150 possible design alternative is that it could operate over CoAP,
2151 alternatively it could be converted to/from CoAP by a gateway. We
2152 would like to see such a protocol carry multiple metrics, for example
2153 similar to those used for RPL operations [RFC6551]
2155 5.3.2.2. 6TiSCH IP Interface
2157 "6top" ([I-D.wang-6tisch-6top-sublayer]) is a logical link control
2158 sitting between the IP layer and the TSCH MAC layer which provides
2159 the link abstraction that is required for IP operations. The 6top
2160 data model and management interfaces are further discussed in
2161 [I-D.ietf-6tisch-6top-interface] and [I-D.ietf-6tisch-coap].
2163 An IP packet that is sent along a 6TiSCH path uses the Differentiated
2164 Services Per-Hop-Behavior Group called Deterministic Forwarding, as
2165 described in [I-D.svshah-tsvwg-deterministic-forwarding].
2167 5.3.3. 6TiSCH Security Considerations
2169 On top of the classical requirements for protection of control
2170 signaling, it must be noted that 6TiSCH networks operate on limited
2171 resources that can be depleted rapidly in a DoS attack on the system,
2172 for instance by placing a rogue device in the network, or by
2173 obtaining management control and setting up unexpected additional
2174 paths.
2176 5.4. Wireless Industrial Asks
2178 6TiSCH depends on DetNet to define:
2180 o Configuration (state) and operations for deterministic paths
2182 o End-to-end protocols for deterministic forwarding (tagging, IP)
2184 o Protocol for packet replication and elimination
2186 6. Cellular Radio
2188 6.1. Use Case Description
2190 This use case describes the application of deterministic networking
2191 in the context of cellular telecom transport networks. Important
2192 elements include time synchronization, clock distribution, and ways
2193 of establishing time-sensitive streams for both Layer-2 and Layer-3
2194 user plane traffic.
2196 6.1.1. Network Architecture
2198 Figure 10 illustrates a typical 3GPP-defined cellular network
2199 architecture, which includes "Fronthaul", "Midhaul" and "Backhaul"
2200 network segments. The "Fronthaul" is the network connecting base
2201 stations (baseband processing units) to the remote radio heads
2202 (antennas). The "Midhaul" is the network inter-connecting base
2203 stations (or small cell sites). The "Backhaul" is the network or
2204 links connecting the radio base station sites to the network
2205 controller/gateway sites (i.e. the core of the 3GPP cellular
2206 network).
2208 In Figure 10 "eNB" ("E-UTRAN Node B") is the hardware that is
2209 connected to the mobile phone network which communicates directly
2210 with mobile handsets ([TS36300]).
2212 Y (remote radio heads (antennas))
2213 \
2214 Y__ \.--. .--. +------+
2215 \_( `. +---+ _(Back`. | 3GPP |
2216 Y------( Front )----|eNB|----( Haul )----| core |
2217 ( ` .Haul ) +---+ ( ` . ) ) | netw |
2218 /`--(___.-' \ `--(___.-' +------+
2219 Y_/ / \.--. \
2220 Y_/ _( Mid`. \
2221 ( Haul ) \
2222 ( ` . ) ) \
2223 `--(___.-'\_____+---+ (small cell sites)
2224 \ |SCe|__Y
2225 +---+ +---+
2226 Y__|eNB|__Y
2227 +---+
2228 Y_/ \_Y ("local" radios)
2230 Figure 10: Generic 3GPP-based Cellular Network Architecture
2232 6.1.2. Delay Constraints
2234 The available processing time for Fronthaul networking overhead is
2235 limited to the available time after the baseband processing of the
2236 radio frame has completed. For example in Long Term Evolution (LTE)
2237 radio, processing of a radio frame is allocated 3ms but typically the
2238 processing uses most of it, allowing only a small fraction to be used
2239 by the Fronthaul network (e.g. up to 250us one-way delay, though the
2240 existing spec ([NGMN-fronth]) supports delay only up to 100us). This
2241 ultimately determines the distance the remote radio heads can be
2242 located from the base stations (e.g., 100us equals roughly 20 km of
2243 optical fiber-based transport). Allocation options of the available
2244 time budget between processing and transport are under heavy
2245 discussions in the mobile industry.
2247 For packet-based transport the allocated transport time (e.g. CPRI
2248 would allow for 100us delay [CPRI]) is consumed by all nodes and
2249 buffering between the remote radio head and the baseband processing
2250 unit, plus the distance-incurred delay.
2252 The baseband processing time and the available "delay budget" for the
2253 fronthaul is likely to change in the forthcoming "5G" due to reduced
2254 radio round trip times and other architectural and service
2255 requirements [NGMN].
2257 The transport time budget, as noted above, places limitations on the
2258 distance that remote radio heads can be located from base stations
2259 (i.e. the link length). In the above analysis, the entire transport
2260 time budget is assumed to be available for link propagation delay.
2261 However the transport time budget can be broken down into three
2262 components: scheduling /queueing delay, transmission delay, and link
2263 propagation delay. Using today's Fronthaul networking technology,
2264 the queuing, scheduling and transmission components might become the
2265 dominant factors in the total transport time rather than the link
2266 propagation delay. This is especially true in cases where the
2267 Fronthaul link is relatively short and it is shared among multiple
2268 Fronthaul flows, for example in indoor and small cell networks,
2269 massive MIMO antenna networks, and split Fronthaul architectures.
2271 DetNet technology can improve this application by controlling and
2272 reducing the time required for the queuing, scheduling and
2273 transmission operations by properly assigning the network resources,
2274 thus leaving more of the transport time budget available for link
2275 propagation, and thus enabling longer link lengths. However, link
2276 length is usually a given parameter and is not a controllable network
2277 parameter, since RRH and BBU sights are usually located in
2278 predetermined locations. However, the number of antennas in an RRH
2279 sight might increase for example by adding more antennas, increasing
2280 the MIMO capability of the network or support of massive MIMO. This
2281 means increasing the number of the fronthaul flows sharing the same
2282 fronthaul link. DetNet can now control the bandwidth assignment of
2283 the fronthaul link and the scheduling of fronthaul packets over this
2284 link and provide adequate buffer provisioning for each flow to reduce
2285 the packet loss rate.
2287 Another way in which DetNet technology can aid Fronthaul networks is
2288 by providing effective isolation from best-effort (and other classes
2289 of) traffic, which can arise as a result of network slicing in 5G
2290 networks where Fronthaul traffic generated in different network
2291 slices might have differing performance requirements. DetNet
2292 technology can also dynamically control the bandwidth assignment,
2293 scheduling and packet forwarding decisions and the buffer
2294 provisioning of the Fronthaul flows to guarantee the end-to-end delay
2295 of the Fronthaul packets and minimize the packet loss rate.
2297 [METIS] documents the fundamental challenges as well as overall
2298 technical goals of the future 5G mobile and wireless system as the
2299 starting point. These future systems should support much higher data
2300 volumes and rates and significantly lower end-to-end latency for 100x
2301 more connected devices (at similar cost and energy consumption levels
2302 as today's system).
2304 For Midhaul connections, delay constraints are driven by Inter-Site
2305 radio functions like Coordinated Multipoint Processing (CoMP, see
2306 [CoMP]). CoMP reception and transmission is a framework in which
2307 multiple geographically distributed antenna nodes cooperate to
2308 improve the performance of the users served in the common cooperation
2309 area. The design principal of CoMP is to extend the current single-
2310 cell to multi-UE (User Equipment) transmission to a multi-cell-to-
2311 multi-UEs transmission by base station cooperation.
2313 CoMP has delay-sensitive performance parameters, which are "midhaul
2314 latency" and "CSI (Channel State Information) reporting and
2315 accuracy". The essential feature of CoMP is signaling between eNBs,
2316 so Midhaul latency is the dominating limitation of CoMP performance.
2317 Generally, CoMP can benefit from coordinated scheduling (either
2318 distributed or centralized) of different cells if the signaling delay
2319 between eNBs is within 1-10ms. This delay requirement is both rigid
2320 and absolute because any uncertainty in delay will degrade the
2321 performance significantly.
2323 Inter-site CoMP is one of the key requirements for 5G and is also a
2324 near-term goal for the current 4.5G network architecture.
2326 6.1.3. Time Synchronization Constraints
2328 Fronthaul time synchronization requirements are given by [TS25104],
2329 [TS36104], [TS36211], and [TS36133]. These can be summarized for the
2330 current 3GPP LTE-based networks as:
2332 Delay Accuracy:
2333 +-8ns (i.e. +-1/32 Tc, where Tc is the UMTS Chip time of 1/3.84
2334 MHz) resulting in a round trip accuracy of +-16ns. The value is
2335 this low to meet the 3GPP Timing Alignment Error (TAE) measurement
2336 requirements. Note: performance guarantees of low nanosecond
2337 values such as these are considered to be below the DetNet layer -
2338 it is assumed that the underlying implementation, e.g. the
2339 hardware, will provide sufficient support (e.g. buffering) to
2340 enable this level of accuracy. These values are maintained in the
2341 use case to give an indication of the overall application.
2343 Timing Alignment Error:
2344 Timing Alignment Error (TAE) is problematic to Fronthaul networks
2345 and must be minimized. If the transport network cannot guarantee
2346 low enough TAE then additional buffering has to be introduced at
2347 the edges of the network to buffer out the jitter. Buffering is
2348 not desirable as it reduces the total available delay budget.
2349 Packet Delay Variation (PDV) requirements can be derived from TAE
2350 for packet based Fronthaul networks.
2352 * For multiple input multiple output (MIMO) or TX diversity
2353 transmissions, at each carrier frequency, TAE shall not exceed
2354 65 ns (i.e. 1/4 Tc).
2356 * For intra-band contiguous carrier aggregation, with or without
2357 MIMO or TX diversity, TAE shall not exceed 130 ns (i.e. 1/2
2358 Tc).
2360 * For intra-band non-contiguous carrier aggregation, with or
2361 without MIMO or TX diversity, TAE shall not exceed 260 ns (i.e.
2362 one Tc).
2364 * For inter-band carrier aggregation, with or without MIMO or TX
2365 diversity, TAE shall not exceed 260 ns.
2367 Transport link contribution to radio frequency error:
2368 +-2 PPB. This value is considered to be "available" for the
2369 Fronthaul link out of the total 50 PPB budget reserved for the
2370 radio interface. Note: the reason that the transport link
2371 contributes to radio frequency error is as follows. The current
2372 way of doing Fronthaul is from the radio unit to remote radio head
2373 directly. The remote radio head is essentially a passive device
2374 (without buffering etc.) The transport drives the antenna
2375 directly by feeding it with samples and everything the transport
2376 adds will be introduced to radio as-is. So if the transport
2377 causes additional frequency error that shows immediately on the
2378 radio as well. Note: performance guarantees of low nanosecond
2379 values such as these are considered to be below the DetNet layer -
2380 it is assumed that the underlying implementation, e.g. the
2381 hardware, will provide sufficient support to enable this level of
2382 performance. These values are maintained in the use case to give
2383 an indication of the overall application.
2385 The above listed time synchronization requirements are difficult to
2386 meet with point-to-point connected networks, and more difficult when
2387 the network includes multiple hops. It is expected that networks
2388 must include buffering at the ends of the connections as imposed by
2389 the jitter requirements, since trying to meet the jitter requirements
2390 in every intermediate node is likely to be too costly. However,
2391 every measure to reduce jitter and delay on the path makes it easier
2392 to meet the end-to-end requirements.
2394 In order to meet the timing requirements both senders and receivers
2395 must remain time synchronized, demanding very accurate clock
2396 distribution, for example support for IEEE 1588 transparent clocks or
2397 boundary clocks in every intermediate node.
2399 In cellular networks from the LTE radio era onward, phase
2400 synchronization is needed in addition to frequency synchronization
2401 ([TS36300], [TS23401]). Time constraints are also important due to
2402 their impact on packet loss. If a packet is delivered too late, then
2403 the packet may be dropped by the host.
2405 6.1.4. Transport Loss Constraints
2407 Fronthaul and Midhaul networks assume almost error-free transport.
2408 Errors can result in a reset of the radio interfaces, which can cause
2409 reduced throughput or broken radio connectivity for mobile customers.
2411 For packetized Fronthaul and Midhaul connections packet loss may be
2412 caused by BER, congestion, or network failure scenarios. Different
2413 fronthaul functional splits are being considered by 3GPP, requiring
2414 strict frame loss ratio (FLR) guarantees. As one example (referring
2415 to the legacy CPRI split which is option 8 in 3GPP) lower layers
2416 splits may imply an FLR of less than 10E-7 for data traffic and less
2417 than 10E-6 for control and management traffic. Current tools for
2418 eliminating packet loss for Fronthaul and Midhaul networks have
2419 serious challenges, for example retransmitting lost packets and/or
2420 using forward error correction (FEC) to circumvent bit errors is
2421 practically impossible due to the additional delay incurred. Using
2422 redundant streams for better guarantees for delivery is also
2423 practically impossible in many cases due to high bandwidth
2424 requirements of Fronthaul and Midhaul networks. Protection switching
2425 is also a candidate but current technologies for the path switch are
2426 too slow to avoid reset of mobile interfaces.
2428 Fronthaul links are assumed to be symmetric, and all Fronthaul
2429 streams (i.e. those carrying radio data) have equal priority and
2430 cannot delay or pre-empt each other. This implies that the network
2431 must guarantee that each time-sensitive flow meets their schedule.
2433 6.1.5. Security Considerations
2435 Establishing time-sensitive streams in the network entails reserving
2436 networking resources for long periods of time. It is important that
2437 these reservation requests be authenticated to prevent malicious
2438 reservation attempts from hostile nodes (or accidental
2439 misconfiguration). This is particularly important in the case where
2440 the reservation requests span administrative domains. Furthermore,
2441 the reservation information itself should be digitally signed to
2442 reduce the risk of a legitimate node pushing a stale or hostile
2443 configuration into another networking node.
2445 Note: This is considered important for the security policy of the
2446 network, but does not affect the core DetNet architecture and design.
2448 6.2. Cellular Radio Networks Today
2450 6.2.1. Fronthaul
2452 Today's Fronthaul networks typically consist of:
2454 o Dedicated point-to-point fiber connection is common
2456 o Proprietary protocols and framings
2458 o Custom equipment and no real networking
2460 Current solutions for Fronthaul are direct optical cables or
2461 Wavelength-Division Multiplexing (WDM) connections.
2463 6.2.2. Midhaul and Backhaul
2465 Today's Midhaul and Backhaul networks typically consist of:
2467 o Mostly normal IP networks, MPLS-TP, etc.
2469 o Clock distribution and sync using 1588 and SyncE
2471 Telecommunication networks in the Mid- and Backhaul are already
2472 heading towards transport networks where precise time synchronization
2473 support is one of the basic building blocks. While the transport
2474 networks themselves have practically transitioned to all-IP packet-
2475 based networks to meet the bandwidth and cost requirements, highly
2476 accurate clock distribution has become a challenge.
2478 In the past, Mid- and Backhaul connections were typically based on
2479 Time Division Multiplexing (TDM-based) and provided frequency
2480 synchronization capabilities as a part of the transport media.
2481 Alternatively other technologies such as Global Positioning System
2482 (GPS) or Synchronous Ethernet (SyncE) are used [SyncE].
2484 Both Ethernet and IP/MPLS [RFC3031] (and PseudoWires (PWE) [RFC3985]
2485 for legacy transport support) have become popular tools to build and
2486 manage new all-IP Radio Access Networks (RANs)
2487 [I-D.kh-spring-ip-ran-use-case]. Although various timing and
2488 synchronization optimizations have already been proposed and
2489 implemented including 1588 PTP enhancements
2490 [I-D.ietf-tictoc-1588overmpls] and [I-D.ietf-mpls-residence-time],
2491 these solution are not necessarily sufficient for the forthcoming RAN
2492 architectures nor do they guarantee the more stringent time-
2493 synchronization requirements such as [CPRI].
2495 There are also existing solutions for TDM over IP such as [RFC4553],
2496 [RFC5086], and [RFC5087], as well as TDM over Ethernet transports
2497 such as [MEF8].
2499 6.3. Cellular Radio Networks Future
2501 Future Cellular Radio Networks will be based on a mix of different
2502 xHaul networks (xHaul = front-, mid- and backhaul), and future
2503 transport networks should be able to support all of them
2504 simultaneously. It is already envisioned today that:
2506 o Not all "cellular radio network" traffic will be IP, for example
2507 some will remain at Layer 2 (e.g. Ethernet based). DetNet
2508 solutions must address all traffic types (Layer 2, Layer 3) with
2509 the same tools and allow their transport simultaneously.
2511 o All forms of xHaul networks will need some form of DetNet
2512 solutions. For example with the advent of 5G some Backhaul
2513 traffic will also have DetNet requirements, for example traffic
2514 belonging to time-critical 5G applications.
2516 o Different splits of the functionality run on the base stations and
2517 the on-site units could co-exist on the same Fronthaul and
2518 Backhaul network.
2520 We would like to see the following in future Cellular Radio networks:
2522 o Unified standards-based transport protocols and standard
2523 networking equipment that can make use of underlying deterministic
2524 link-layer services
2526 o Unified and standards-based network management systems and
2527 protocols in all parts of the network (including Fronthaul)
2529 New radio access network deployment models and architectures may
2530 require time- sensitive networking services with strict requirements
2531 on other parts of the network that previously were not considered to
2532 be packetized at all. Time and synchronization support are already
2533 topical for Backhaul and Midhaul packet networks [MEF22.1.1] and are
2534 becoming a real issue for Fronthaul networks also. Specifically in
2535 Fronthaul networks the timing and synchronization requirements can be
2536 extreme for packet based technologies, for example, on the order of
2537 sub +-20 ns packet delay variation (PDV) and frequency accuracy of
2538 +0.002 PPM [Fronthaul].
2540 The actual transport protocols and/or solutions to establish required
2541 transport "circuits" (pinned-down paths) for Fronthaul traffic are
2542 still undefined. Those are likely to include (but are not limited
2543 to) solutions directly over Ethernet, over IP, and using MPLS/
2544 PseudoWire transport.
2546 Even the current time-sensitive networking features may not be
2547 sufficient for Fronthaul traffic. Therefore, having specific
2548 profiles that take the requirements of Fronthaul into account is
2549 desirable [IEEE8021CM].
2551 Interesting and important work for time-sensitive networking has been
2552 done for Ethernet [TSNTG], which specifies the use of IEEE 1588 time
2553 precision protocol (PTP) [IEEE1588] in the context of IEEE 802.1D and
2554 IEEE 802.1Q. [IEEE8021AS] specifies a Layer 2 time synchronizing
2555 service, and other specifications such as IEEE 1722 [IEEE1722]
2556 specify Ethernet-based Layer-2 transport for time-sensitive streams.
2558 New promising work seeks to enable the transport of time-sensitive
2559 fronthaul streams in Ethernet bridged networks [IEEE8021CM].
2560 Analogous to IEEE 1722 there is an ongoing standardization effort to
2561 define the Layer-2 transport encapsulation format for transporting
2562 radio over Ethernet (RoE) in the IEEE 1904.3 Task Force [IEEE19143].
2564 As mentioned in Section 6.1.2, 5G communications will provide one of
2565 the most challenging cases for delay sensitive networking. In order
2566 to meet the challenges of ultra-low latency and ultra-high
2567 throughput, 3GPP has studied various "functional splits" for 5G,
2568 i.e., physical decomposition of the gNodeB base station and
2569 deployment of its functional blocks in different locations [TR38801].
2571 These splits are numbered from split option 1 (Dual Connectivity, a
2572 split in which the radio resource control is centralized and other
2573 radio stack layers are in distributed units) to split option 8 (a
2574 PHY-RF split in which RF functionality is in a distributed unit and
2575 the rest of the radio stack is in the centralized unit), with each
2576 intermediate split having its own data rate and delay requirements.
2577 Packetized versions of different splits have recently been proposed
2578 including eCPRI [eCPRI] and RoE (as previously noted). Both provide
2579 Ethernet encapsulations, and eCPRI is also capable of IP
2580 encapsulation.
2582 All-IP RANs and xHaul networks would benefit from time
2583 synchronization and time-sensitive transport services. Although
2584 Ethernet appears to be the unifying technology for the transport,
2585 there is still a disconnect providing Layer 3 services. The protocol
2586 stack typically has a number of layers below the Ethernet Layer 2
2587 that shows up to the Layer 3 IP transport. It is not uncommon that
2588 on top of the lowest layer (optical) transport there is the first
2589 layer of Ethernet followed one or more layers of MPLS, PseudoWires
2590 and/or other tunneling protocols finally carrying the Ethernet layer
2591 visible to the user plane IP traffic.
2593 While there are existing technologies to establish circuits through
2594 the routed and switched networks (especially in MPLS/PWE space),
2595 there is still no way to signal the time synchronization and time-
2596 sensitive stream requirements/reservations for Layer-3 flows in a way
2597 that addresses the entire transport stack, including the Ethernet
2598 layers that need to be configured.
2600 Furthermore, not all "user plane" traffic will be IP. Therefore, the
2601 same solution also must address the use cases where the user plane
2602 traffic is a different layer, for example Ethernet frames.
2604 There is existing work describing the problem statement
2605 [I-D.finn-detnet-problem-statement] and the architecture
2606 [I-D.finn-detnet-architecture] for deterministic networking (DetNet)
2607 that targets solutions for time-sensitive (IP/transport) streams with
2608 deterministic properties over Ethernet-based switched networks.
2610 6.4. Cellular Radio Networks Asks
2612 A standard for data plane transport specification which is:
2614 o Unified among all xHauls (meaning that different flows with
2615 diverse DetNet requirements can coexist in the same network and
2616 traverse the same nodes without interfering with each other)
2618 o Deployed in a highly deterministic network environment
2620 o Capable of supporting multiple functional splits simultaneously,
2621 including existing Backhaul and CPRI Fronthaul and potentially new
2622 modes as defined for example in 3GPP; these goals can be supported
2623 by the existing DetNet Use Case Common Themes, notably "Mix of
2624 Deterministic and Best-Effort Traffic", "Bounded Latency", "Low
2625 Latency", "Symmetrical Path Delays", and "Deterministic Flows".
2627 o Capable of supporting Network Slicing and Multi-tenancy; these
2628 goals can be supported by the same DetNet themes noted above.
2630 o Capable of transporting both in-band and out-band control traffic
2631 (OAM info, ...).
2633 o Deployable over multiple data link technologies (e.g., IEEE 802.3,
2634 mmWave, etc.).
2636 A standard for data flow information models that are:
2638 o Aware of the time sensitivity and constraints of the target
2639 networking environment
2641 o Aware of underlying deterministic networking services (e.g., on
2642 the Ethernet layer)
2644 7. Industrial M2M
2646 7.1. Use Case Description
2648 Industrial Automation in general refers to automation of
2649 manufacturing, quality control and material processing. In this
2650 "machine to machine" (M2M) use case we consider machine units in a
2651 plant floor which periodically exchange data with upstream or
2652 downstream machine modules and/or a supervisory controller within a
2653 local area network.
2655 The actors of M2M communication are Programmable Logic Controllers
2656 (PLCs). Communication between PLCs and between PLCs and the
2657 supervisory PLC (S-PLC) is achieved via critical control/data streams
2658 Figure 11.
2660 S (Sensor)
2661 \ +-----+
2662 PLC__ \.--. .--. ---| MES |
2663 \_( `. _( `./ +-----+
2664 A------( Local )-------------( L2 )
2665 ( Net ) ( Net ) +-------+
2666 /`--(___.-' `--(___.-' ----| S-PLC |
2667 S_/ / PLC .--. / +-------+
2668 A_/ \_( `.
2669 (Actuator) ( Local )
2670 ( Net )
2671 /`--(___.-'\
2672 / \ A
2673 S A
2675 Figure 11: Current Generic Industrial M2M Network Architecture
2677 This use case focuses on PLC-related communications; communication to
2678 Manufacturing-Execution-Systems (MESs) are not addressed.
2680 This use case covers only critical control/data streams; non-critical
2681 traffic between industrial automation applications (such as
2682 communication of state, configuration, set-up, and database
2683 communication) are adequately served by currently available
2684 prioritizing techniques. Such traffic can use up to 80% of the total
2685 bandwidth required. There is also a subset of non-time-critical
2686 traffic that must be reliable even though it is not time sensitive.
2688 In this use case the primary need for deterministic networking is to
2689 provide end-to-end delivery of M2M messages within specific timing
2690 constraints, for example in closed loop automation control. Today
2691 this level of determinism is provided by proprietary networking
2692 technologies. In addition, standard networking technologies are used
2693 to connect the local network to remote industrial automation sites,
2694 e.g. over an enterprise or metro network which also carries other
2695 types of traffic. Therefore, flows that should be forwarded with
2696 deterministic guarantees need to be sustained regardless of the
2697 amount of other flows in those networks.
2699 7.2. Industrial M2M Communication Today
2701 Today, proprietary networks fulfill the needed timing and
2702 availability for M2M networks.
2704 The network topologies used today by industrial automation are
2705 similar to those used by telecom networks: Daisy Chain, Ring, Hub and
2706 Spoke, and Comb (a subset of Daisy Chain).
2708 PLC-related control/data streams are transmitted periodically and
2709 carry either a pre-configured payload or a payload configured during
2710 runtime.
2712 Some industrial applications require time synchronization at the end
2713 nodes. For such time-coordinated PLCs, accuracy of 1 microsecond is
2714 required. Even in the case of "non-time-coordinated" PLCs time sync
2715 may be needed e.g. for timestamping of sensor data.
2717 Industrial network scenarios require advanced security solutions.
2718 Many of the current industrial production networks are physically
2719 separated. Preventing critical flows from be leaked outside a domain
2720 is handled today by filtering policies that are typically enforced in
2721 firewalls.
2723 7.2.1. Transport Parameters
2725 The Cycle Time defines the frequency of message(s) between industrial
2726 actors. The Cycle Time is application dependent, in the range of 1ms
2727 - 100ms for critical control/data streams.
2729 Because industrial applications assume deterministic transport for
2730 critical Control-Data-Stream parameters (instead of defining latency
2731 and delay variation parameters) it is sufficient to fulfill the upper
2732 bound of latency (maximum latency). The underlying networking
2733 infrastructure must ensure a maximum end-to-end delivery time of
2734 messages in the range of 100 microseconds to 50 milliseconds
2735 depending on the control loop application.
2737 The bandwidth requirements of control/data streams are usually
2738 calculated directly from the bytes-per-cycle parameter of the control
2739 loop. For PLC-to-PLC communication one can expect 2 - 32 streams
2740 with packet size in the range of 100 - 700 bytes. For S-PLC to PLCs
2741 the number of streams is higher - up to 256 streams. Usually no more
2742 than 20% of available bandwidth is used for critical control/data
2743 streams. In today's networks 1Gbps links are commonly used.
2745 Most PLC control loops are rather tolerant of packet loss, however
2746 critical control/data streams accept no more than 1 packet loss per
2747 consecutive communication cycle (i.e. if a packet gets lost in cycle
2748 "n", then the next cycle ("n+1") must be lossless). After two or
2749 more consecutive packet losses the network may be considered to be
2750 "down" by the Application.
2752 As network downtime may impact the whole production system the
2753 required network availability is rather high (99,999%).
2755 Based on the above parameters we expect that some form of redundancy
2756 will be required for M2M communications, however any individual
2757 solution depends on several parameters including cycle time, delivery
2758 time, etc.
2760 7.2.2. Stream Creation and Destruction
2762 In an industrial environment, critical control/data streams are
2763 created rather infrequently, on the order of ~10 times per day / week
2764 / month. Most of these critical control/data streams get created at
2765 machine startup, however flexibility is also needed during runtime,
2766 for example when adding or removing a machine. Going forward as
2767 production systems become more flexible, we expect a significant
2768 increase in the rate at which streams are created, changed and
2769 destroyed.
2771 7.3. Industrial M2M Future
2773 We would like to see a converged IP-standards-based network with
2774 deterministic properties that can satisfy the timing, security and
2775 reliability constraints described above. Today's proprietary
2776 networks could then be interfaced to such a network via gateways or,
2777 in the case of new installations, devices could be connected directly
2778 to the converged network.
2780 For this use case we expect time synchronization accuracy on the
2781 order of 1us.
2783 7.4. Industrial M2M Asks
2785 o Converged IP-based network
2787 o Deterministic behavior (bounded latency and jitter )
2789 o High availability (presumably through redundancy) (99.999 %)
2791 o Low message delivery time (100us - 50ms)
2793 o Low packet loss (burstless, 0.1-1 %)
2795 o Security (e.g. prevent critical flows from being leaked between
2796 physically separated networks)
2798 8. Mining Industry
2800 8.1. Use Case Description
2802 The mining industry is highly dependent on networks to monitor and
2803 control their systems both in open-pit and underground extraction,
2804 transport and refining processes. In order to reduce risks and
2805 increase operational efficiency in mining operations, a number of
2806 processes have migrated the operators from the extraction site to
2807 remote control and monitoring.
2809 In the case of open pit mining, autonomous trucks are used to
2810 transport the raw materials from the open pit to the refining factory
2811 where the final product (e.g. Copper) is obtained. Although the
2812 operation is autonomous, the tracks are remotely monitored from a
2813 central facility.
2815 In pit mines, the monitoring of the tailings or mine dumps is
2816 critical in order to avoid any environmental pollution. In the past,
2817 monitoring has been conducted through manual inspection of pre-
2818 installed dataloggers. Cabling is not usually exploited in such
2819 scenarios due to the cost and complex deployment requirements.
2820 Currently, wireless technologies are being employed to monitor these
2821 cases permanently. Slopes are also monitored in order to anticipate
2822 possible mine collapse. Due to the unstable terrain, cable
2823 maintenance is costly and complex and hence wireless technologies are
2824 employed.
2826 In the underground monitoring case, autonomous vehicles with
2827 extraction tools travel autonomously through the tunnels, but their
2828 operational tasks (such as excavation, stone breaking and transport)
2829 are controlled remotely from a central facility. This generates
2830 video and feedback upstream traffic plus downstream actuator control
2831 traffic.
2833 8.2. Mining Industry Today
2835 Currently the mining industry uses a packet switched architecture
2836 supported by high speed ethernet. However in order to achieve the
2837 delay and packet loss requirements the network bandwidth is
2838 overestimated, thus providing very low efficiency in terms of
2839 resource usage.
2841 QoS is implemented at the Routers to separate video, management,
2842 monitoring and process control traffic for each stream.
2844 Since mobility is involved in this process, the connection between
2845 the backbone and the mobile devices (e.g. trucks, trains and
2846 excavators) is solved using a wireless link. These links are based
2847 on 802.11 for open-pit mining and leaky feeder for underground
2848 mining.
2850 Lately in pit mines the use of LPWAN technologies has been extended:
2851 Tailings, slopes and mine dumps are monitored by battery-powered
2852 dataloggers that make use of robust long range radio technologies.
2853 Reliability is usually ensured through retransmissions at L2.
2854 Gateways or concentrators act as bridges forwarding the data to the
2855 backbone ethernet network. Deterministic requirements are biased
2856 towards reliability rather than latency as events are slowly
2857 triggered or can be anticipated in advance.
2859 At the mineral processing stage, conveyor belts and refining
2860 processes are controlled by a SCADA system, which provides the in-
2861 factory delay-constrained networking requirements.
2863 Voice communications are currently served by a redundant trunking
2864 infrastructure, independent from current data networks.
2866 8.3. Mining Industry Future
2868 Mining operations and management are currently converging towards a
2869 combination of autonomous operation and teleoperation of transport
2870 and extraction machines. This means that video, audio, monitoring
2871 and process control traffic will increase dramatically. Ideally, all
2872 activities on the mine will rely on network infrastructure.
2874 Wireless for open-pit mining is already a reality with LPWAN
2875 technologies and it is expected to evolve to more advanced LPWAN
2876 technologies such as those based on LTE to increase last hop
2877 reliability or novel LPWAN flavours with deterministic access.
2879 One area in which DetNet can improve this use case is in the wired
2880 networks that make up the "backbone network" of the system, which
2881 connect together many wireless access points (APs). The mobile
2882 machines (which are connected to the network via wireless) transition
2883 from one AP to the next as they move about. A deterministic,
2884 reliable, low latency backbone can enable these transitions to be
2885 more reliable.
2887 Connections which extend all the way from the base stations to the
2888 machinery via a mix of wired and wireless hops would also be
2889 beneficial, for example to improve remote control responsiveness of
2890 digging machines. However to guarantee deterministic performance of
2891 a DetNet, the end-to-end underlying network must be deterministic.
2892 Thus for this use case if a deterministic wireless transport is
2893 integrated with a wire-based DetNet network, it could create the
2894 desired wired plus wireless end-to-end deterministic network.
2896 8.4. Mining Industry Asks
2898 o Improved bandwidth efficiency
2900 o Very low delay to enable machine teleoperation
2902 o Dedicated bandwidth usage for high resolution video streams
2904 o Predictable delay to enable realtime monitoring
2906 o Potential to construct a unified DetNet network over a combination
2907 of wired and deterministic wireless links
2909 9. Private Blockchain
2911 9.1. Use Case Description
2913 Blockchain was created with bitcoin, as a 'public' blockchain on the
2914 open Internet, however blockchain has also spread far beyond its
2915 original host into various industries such as smart manufacturing,
2916 logistics, security, legal rights and others. In these industries
2917 blockchain runs in designated and carefully managed network in which
2918 deterministic networking requirements could be addressed by Detnet.
2919 Such implementations are referred to as 'private' blockchain.
2921 The sole distinction between public and private blockchain is related
2922 to who is allowed to participate in the network, execute the
2923 consensus protocol and maintain the shared ledger.
2925 Today's networks treat the traffic from blockchain on a best-effort
2926 basis, but blockchain operation could be made much more efficient if
2927 deterministic networking service were available to minimize latency
2928 and packet loss in the network.
2930 9.1.1. Blockchain Operation
2932 A 'block' runs as a container of a batch of primary items such as
2933 transactions, property records etc. The blocks are chained in such a
2934 way that the hash of the previous block works as the pointer header
2935 of the new block, where confirmation of each block requires a
2936 consensus mechanism. When an item arrives at a blockchain node, the
2937 latter broadcasts this item to the rest of nodes which receive and
2938 verify it and put it in the ongoing block. Block confirmation
2939 process begins as the amount of items reaches the predefined block
2940 capacity, and the node broadcasts its proved block to the rest of
2941 nodes to be verified and chained.
2943 9.1.2. Blockchain Network Architecture
2945 Blockchain node communication and coordination is achieved mainly
2946 through frequent point to multi-point communication, however
2947 persistent point-to-point connections are used to transport both the
2948 items and the blocks to the other nodes.
2950 When a node initiates, it first requests the other nodes' address
2951 from a specific entity such as DNS, then it creates persistent
2952 connections each of with other nodes. If node A confirms an item, it
2953 sends the item to the other nodes via the persistent connections.
2955 As a new block in a node completes and gets proved among the nodes,
2956 it starts propagating this block towards its neighbor nodes. Assume
2957 node A receives a block, it sends invite message after verification
2958 to its neighbor B, B checks if the designated block is available, it
2959 responds get message to A if it is unavailable, and A send the
2960 complete block to B. B repeats the process as A to start the next
2961 round of block propagation.
2963 The challenge of blockchain network operation is not overall data
2964 rates, since the volume from both block and item stays between
2965 hundreds of bytes to a couple of mega bytes per second, but is in
2966 transporting the blocks with minimum latency to maximize efficiency
2967 of the blockchain consensus process.
2969 9.1.3. Security Considerations
2971 Security is crucial to blockchain applications, and todayt blockchain
2972 addresses its security issues mainly at the application level, where
2973 cryptography as well as hash-based consensus play a leading role
2974 preventing both double-spending and malicious service attack.
2975 However, there is concern that in the proposed use case of a private
2976 blockchain network which is dependent on deterministic properties,
2977 the network could be vulnerable to delays and other specific attacks
2978 against determinism which could interrupt service.
2980 9.2. Private Blockchain Today
2982 Today private blockchain runs in L2 or L3 VPN, in general without
2983 guaranteed determinism. The industry players are starting to realize
2984 that improving determinism in their blockchain networks could improve
2985 the performance of their service, but as of today these goals are not
2986 being met.
2988 9.3. Private Blockchain Future
2990 Blockchain system performance can be greatly improved through
2991 deterministic networking service primarily because it would
2992 accelerate the consensus process. It would be valuable to be able to
2993 design a private blockchain network with the following properties:
2995 o Transport of point to multi-point traffic in a coordinated network
2996 architecture rather than at the application layer (which typically
2997 uses point-to-point connections)
2999 o Guaranteed transport latency
3001 o Reduced packet loss (to the point where packet retransmission-
3002 incurred delay would be negligible.)
3004 9.4. Private Blockchain Asks
3006 o Layer 2 and Layer 3 multicast of blockchain traffic
3008 o Item and block delivery with bounded, low latency and negligible
3009 packet loss
3011 o Coexistence in a single network of blockchain and IT traffic.
3013 o Ability to scale the network by distributing the centralized
3014 control of the network across multiple control entities.
3016 10. Network Slicing
3018 10.1. Use Case Description
3020 Network Slicing divides one physical network infrastructure into
3021 multiple logical networks. Each slice, corresponding to a logical
3022 network, uses resources and network functions independently from each
3023 other. Network Slicing provides flexibility of resource allocation
3024 and service quality customization.
3026 Future services will demand network performance with a wide variety
3027 of characteristics such as high data rate, low latency, low loss
3028 rate, security and many other parameters. Ideally every service
3029 would have its own physical network satisfying its particular
3030 performance requirements, however that would be prohibitively
3031 expensive. Network Slicing can provide a customized slice for a
3032 single service, and multiple slices can share the same physical
3033 network. This method can optimize the performance for the service at
3034 lower cost, and the flexibility of setting up and release the slices
3035 also allows the user to allocate the network resources dynamically.
3037 Unlike the other use cases presented here, Network Slicing is not a
3038 specific application that depends on specific deterministic
3039 properties; rather it is introduced as an area of networking to which
3040 DetNet might be applicable.
3042 10.2. DetNet Applied to Network Slicing
3044 10.2.1. Resource Isolation Across Slices
3046 One of the requirements discussed for Network Slicing is the "hard"
3047 separation of various users' deterministic performance. That is, it
3048 should be impossible for activity, lack of activity, or changes in
3049 activity of one or more users to have any appreciable effect on the
3050 deterministic performance parameters of any other slices. Typical
3051 techniques used today, which share a physical network among users, do
3052 not offer this level of isolation. DetNet can supply point-to-point
3053 or point-to-multipoint paths that offer bandwidth and latency
3054 guarantees to a user that cannot be affected by other users' data
3055 traffic. Thus DetNet is a powerful tool when latency and reliability
3056 are required in Network Slicing.
3058 10.2.2. Deterministic Services Within Slices
3060 Slices may need to provide services with DetNet-type performance
3061 guarantees, however we note that a system can be implemented to
3062 provide such services in more than one way. For example the slice
3063 itself might be implemented using DetNet, and thus the slice can
3064 provide service guarantees and isolation to its users without any
3065 particular DetNet awareness on the part of the users' applications.
3066 Alternatively, a "non-DetNet-aware" slice may host an application
3067 that itself implements DetNet services and thus can enjoy similar
3068 service guarantees.
3070 10.3. A Network Slicing Use Case Example - 5G Bearer Network
3072 Network Slicing is a core feature of 5G defined in 3GPP, which is
3073 currently under development. A network slice in a mobile network is
3074 a complete logical network including Radio Access Network (RAN) and
3075 Core Network (CN). It provides telecommunication services and
3076 network capabilities, which may vary from slice to slice. A 5G
3077 bearer network is a typical use case of Network Slicing; for example
3078 consider three 5G service scenarios: eMMB, URLLC, and mMTC.
3080 o eMBB (Enhanced Mobile Broadband) focuses on services characterized
3081 by high data rates, such as high definition videos, virtual
3082 reality, augmented reality, and fixed mobile convergence.
3084 o URLLC (Ultra-Reliable and Low Latency Communications) focuses on
3085 latency-sensitive services, such as self-driving vehicles, remote
3086 surgery, or drone control.
3088 o mMTC (massive Machine Type Communications) focuses on services
3089 that have high requirements for connection density, such as those
3090 typical for smart city and smart agriculture use cases.
3092 A 5G bearer network could use DetNet to provide hard resource
3093 isolation across slices and within the slice. For example consider
3094 Slice-A and Slice-B, with DetNet used to transit services URLLC-A and
3095 URLLC-B over them. Without DetNet, URLLC-A and URLLC-B would compete
3096 for bandwidth resource, and latency and reliability would not be
3097 guaranteed. With DetNet, URLLC-A and URLLC-B have separate bandwidth
3098 reservation and there is no resource conflict between them, as though
3099 they were in different logical networks.
3101 10.4. Non-5G Applications of Network Slicing
3103 Although operation of services not related to 5G is not part of the
3104 5G Network Slicing definition and scope, Network Slicing is likely to
3105 become a preferred approach to providing various services across a
3106 shared physical infrastructure. Examples include providing
3107 electrical utilities services and pro audio services via slices. Use
3108 cases like these could become more common once the work for the 5G
3109 core network evolves to include wired as well as wireless access.
3111 10.5. Limitations of DetNet in Network Slicing
3113 DetNet cannot cover every Network Slicing use case. One issue is
3114 that DetNet is a point-to-point or point-to-multipoint technology,
3115 however Network Slicing ultimately needs multi-point to multi-point
3116 guarantees. Another issue is that the number of flows that can be
3117 carried by DetNet is limited by DetNet scalability; flow aggregation
3118 and queuing management modification may help address this.
3119 Additional work and discussion are needed to address these topics.
3121 10.6. Network Slicing Today and Future
3123 Network Slicing has the promise to satisfy many requirements of
3124 future network deployment scenarios, but it is still a collection of
3125 ideas and analysis, without a specific technical solution. DetNet is
3126 one of various technologies that have potential to be used in Network
3127 Slicing, along with for example Flex-E and Segment Routing. For more
3128 information please see the IETF99 Network Slicing BOF session agenda
3129 and materials.
3131 10.7. Network Slicing Asks
3133 o Isolation from other flows through Queuing Management
3135 o Service Quality Customization and Guarantee
3137 o Security
3139 11. Use Case Common Themes
3141 This section summarizes the expected properties of a DetNet network,
3142 based on the use cases as described in this draft.
3144 11.1. Unified, standards-based network
3146 11.1.1. Extensions to Ethernet
3148 A DetNet network is not "a new kind of network" - it based on
3149 extensions to existing Ethernet standards, including elements of IEEE
3150 802.1 AVB/TSN and related standards. Presumably it will be possible
3151 to run DetNet over other underlying transports besides Ethernet, but
3152 Ethernet is explicitly supported.
3154 11.1.2. Centrally Administered
3156 In general a DetNet network is not expected to be "plug and play" -
3157 it is expected that there is some centralized network configuration
3158 and control system. Such a system may be in a single central
3159 location, or it maybe distributed across multiple control entities
3160 that function together as a unified control system for the network.
3161 However, the ability to "hot swap" components (e.g. due to
3162 malfunction) is similar enough to "plug and play" that this kind of
3163 behavior may be expected in DetNet networks, depending on the
3164 implementation.
3166 11.1.3. Standardized Data Flow Information Models
3168 Data Flow Information Models to be used with DetNet networks are to
3169 be specified by DetNet.
3171 11.1.4. L2 and L3 Integration
3173 A DetNet network is intended to integrate between Layer 2 (bridged)
3174 network(s) (e.g. AVB/TSN LAN) and Layer 3 (routed) network(s) (e.g.
3175 using IP-based protocols). One example of this is "making AVB/TSN-
3176 type deterministic performance available from Layer 3 applications,
3177 e.g. using RTP". Another example is "connecting two AVB/TSN LANs
3178 ("islands") together through a standard router".
3180 11.1.5. Consideration for IPv4
3182 This Use Cases draft explicitly does not specify any particular
3183 implementation or protocol, however it has been observed that various
3184 of the use cases described (and their associated industries) are
3185 explicitly based on IPv4 (as opposed to IPv6) and it is not
3186 considered practical to expect them to migrate to IPv6 in order to
3187 use DetNet. Thus the expectation is that even if not every feature
3188 of DetNet is available in an IPv4 context, at least some of the
3189 significant benefits (such as guaranteed end-to-end delivery and low
3190 latency) are expected to be available.
3192 11.1.6. Guaranteed End-to-End Delivery
3194 Packets sent over DetNet are guaranteed not to be dropped by the
3195 network due to congestion. (Packets may however be dropped for
3196 intended reasons, e.g. per security measures).
3198 11.1.7. Replacement for Multiple Proprietary Deterministic Networks
3200 There are many proprietary non-interoperable deterministic Ethernet-
3201 based networks currently available; DetNet is intended to provide an
3202 open-standards-based alternative to such networks.
3204 11.1.8. Mix of Deterministic and Best-Effort Traffic
3206 DetNet is intended to support coexistance of time-sensitive
3207 operational (OT) traffic and information (IT) traffic on the same
3208 ("unified") network.
3210 11.1.9. Unused Reserved BW to be Available to Best Effort Traffic
3212 If bandwidth reservations are made for a stream but the associated
3213 bandwidth is not used at any point in time, that bandwidth is made
3214 available on the network for best-effort traffic. If the owner of
3215 the reserved stream then starts transmitting again, the bandwidth is
3216 no longer available for best-effort traffic, on a moment-to-moment
3217 basis. Note that such "temporarily available" bandwidth is not
3218 available for time-sensitive traffic, which must have its own
3219 reservation.
3221 11.1.10. Lower Cost, Multi-Vendor Solutions
3223 The DetNet network specifications are intended to enable an ecosystem
3224 in which multiple vendors can create interoperable products, thus
3225 promoting device diversity and potentially higher numbers of each
3226 device manufactured, promoting cost reduction and cost competition
3227 among vendors. The intent is that DetNet networks should be able to
3228 be created at lower cost and with greater diversity of available
3229 devices than existing proprietary networks.
3231 11.2. Scalable Size
3233 DetNet networks range in size from very small, e.g. inside a single
3234 industrial machine, to very large, for example a Utility Grid network
3235 spanning a whole country, and involving many "hops" over various
3236 kinds of links for example radio repeaters, microwave linkes, fiber
3237 optic links, etc.. However recall that the scope of DetNet is
3238 confined to networks that are centrally administered, and explicitly
3239 excludes unbounded decentralized networks such as the Internet.
3241 11.3. Scalable Timing Parameters and Accuracy
3243 11.3.1. Bounded Latency
3245 The DetNet Data Flow Information Model is expected to provide means
3246 to configure the network that include parameters for querying network
3247 path latency, requesting bounded latency for a given stream,
3248 requesting worst case maximum and/or minimum latency for a given path
3249 or stream, and so on. It is an expected case that the network may
3250 not be able to provide a given requested service level, and if so the
3251 network control system should reply that the requested services is
3252 not available (as opposed to accepting the parameter but then not
3253 delivering the desired behavior).
3255 11.3.2. Low Latency
3257 Applications may require "extremely low latency" however depending on
3258 the application these may mean very different latency values; for
3259 example "low latency" across a Utility grid network is on a different
3260 time scale than "low latency" in a motor control loop in a small
3261 machine. The intent is that the mechanisms for specifying desired
3262 latency include wide ranges, and that architecturally there is
3263 nothing to prevent arbirtrarily low latencies from being implemented
3264 in a given network.
3266 11.3.3. Symmetrical Path Delays
3268 Some applications would like to specify that the transit delay time
3269 values be equal for both the transmit and return paths.
3271 11.4. High Reliability and Availability
3273 Reliablity is of critical importance to many DetNet applications, in
3274 which consequences of failure can be extraordinarily high in terms of
3275 cost and even human life. DetNet based systems are expected to be
3276 implemented with essentially arbitrarily high availability (for
3277 example 99.9999% up time, or even 12 nines). The intent is that the
3278 DetNet designs should not make any assumptions about the level of
3279 reliability and availability that may be required of a given system,
3280 and should define parameters for communicating these kinds of metrics
3281 within the network.
3283 A strategy used by DetNet for providing such extraordinarily high
3284 levels of reliability is to provide redundant paths that can be
3285 seamlessly switched between, while maintaining the required
3286 performance of that system.
3288 11.5. Security
3290 Security is of critical importance to many DetNet applications. A
3291 DetNet network must be able to be made secure against devices
3292 failures, attackers, misbehaving devices, and so on. In a DetNet
3293 network the data traffic is expected to be be time-sensitive, thus in
3294 addition to arriving with the data content as intended, the data must
3295 also arrive at the expected time. This may present "new" security
3296 challenges to implementers, and must be addressed accordingly. There
3297 are other security implications, including (but not limited to) the
3298 change in attack surface presented by packet replication and
3299 elimination.
3301 11.6. Deterministic Flows
3303 Reserved bandwidth data flows must be isolated from each other and
3304 from best-effort traffic, so that even if the network is saturated
3305 with best-effort (and/or reserved bandwidth) traffic, the configured
3306 flows are not adversely affected.
3308 12. Use Cases Explicitly Out of Scope for DetNet
3310 This section contains use case text that has been determined to be
3311 outside of the scope of the present DetNet work.
3313 12.1. DetNet Scope Limitations
3315 The scope of DetNet is deliberately limited to specific use cases
3316 that are consistent with the WG charter, subject to the
3317 interpretation of the WG. At the time the DetNet Use Cases were
3318 solicited and provided by the authors the scope of DetNet was not
3319 clearly defined, and as that clarity has emerged, certain of the use
3320 cases have been determined to be outside the scope of the present
3321 DetNet work. Such text has been moved into this section to clarify
3322 that these use cases will not be supported by the DetNet work.
3324 The text in this section was moved here based on the following
3325 "exclusion" principles. Or, as an alternative to moving all such
3326 text to this section, some draft text has been modified in situ to
3327 reflect these same principles.
3329 The following principles have been established to clarify the scope
3330 of the present DetNet work.
3332 o The scope of network addressed by DetNet is limited to networks
3333 that can be centrally controlled, i.e. an "enterprise" aka
3334 "corporate" network. This explicitly excludes "the open
3335 Internet".
3337 o Maintaining synchronized time across a DetNet network is crucial
3338 to its operation, however DetNet assumes that time is to be
3339 maintained using other means, for example (but not limited to)
3340 Precision Time Protocol ([IEEE1588]). A use case may state the
3341 accuracy and reliability that it expects from the DetNet network
3342 as part of a whole system, however it is understood that such
3343 timing properties are not guaranteed by DetNet itself. It is
3344 currently an open question as to whether DetNet protocols will
3345 include a way for an application to communicate such timing
3346 expectations to the network, and if so whether they would be
3347 expected to materially affect the performance they would receive
3348 from the network as a result.
3350 12.2. Internet-based Applications
3352 12.2.1. Use Case Description
3354 There are many applications that communicate across the open Internet
3355 that could benefit from guaranteed delivery and bounded latency. The
3356 following are some representative examples.
3358 12.2.1.1. Media Content Delivery
3360 Media content delivery continues to be an important use of the
3361 Internet, yet users often experience poor quality audio and video due
3362 to the delay and jitter inherent in today's Internet.
3364 12.2.1.2. Online Gaming
3366 Online gaming is a significant part of the gaming market, however
3367 latency can degrade the end user experience. For example "First
3368 Person Shooter" (FPS) games are highly delay-sensitive.
3370 12.2.1.3. Virtual Reality
3372 Virtual reality (VR) has many commercial applications including real
3373 estate presentations, remote medical procedures, and so on. Low
3374 latency is critical to interacting with the virtual world because
3375 perceptual delays can cause motion sickness.
3377 12.2.2. Internet-Based Applications Today
3379 Internet service today is by definition "best effort", with no
3380 guarantees on delivery or bandwidth.
3382 12.2.3. Internet-Based Applications Future
3384 We imagine an Internet from which we will be able to play a video
3385 without glitches and play games without lag.
3387 For online gaming, the maximum round-trip delay can be 100ms and
3388 stricter for FPS gaming which can be 10-50ms. Transport delay is the
3389 dominate part with a 5-20ms budget.
3391 For VR, 1-10ms maximum delay is needed and total network budget is
3392 1-5ms if doing remote VR.
3394 Flow identification can be used for gaming and VR, i.e. it can
3395 recognize a critical flow and provide appropriate latency bounds.
3397 12.2.4. Internet-Based Applications Asks
3399 o Unified control and management protocols to handle time-critical
3400 data flow
3402 o Application-aware flow filtering mechanism to recognize the timing
3403 critical flow without doing 5-tuple matching
3405 o Unified control plane to provide low latency service on Layer-3
3406 without changing the data plane
3408 o OAM system and protocols which can help to provide E2E-delay
3409 sensitive service provisioning
3411 12.3. Pro Audio and Video - Digital Rights Management (DRM)
3413 This section was moved here because this is considered a Link layer
3414 topic, not direct responsibility of DetNet.
3416 Digital Rights Management (DRM) is very important to the audio and
3417 video industries. Any time protected content is introduced into a
3418 network there are DRM concerns that must be maintained (see
3419 [CONTENT_PROTECTION]). Many aspects of DRM are outside the scope of
3420 network technology, however there are cases when a secure link
3421 supporting authentication and encryption is required by content
3422 owners to carry their audio or video content when it is outside their
3423 own secure environment (for example see [DCI]).
3425 As an example, two techniques are Digital Transmission Content
3426 Protection (DTCP) and High-Bandwidth Digital Content Protection
3427 (HDCP). HDCP content is not approved for retransmission within any
3428 other type of DRM, while DTCP may be retransmitted under HDCP.
3429 Therefore if the source of a stream is outside of the network and it
3430 uses HDCP protection it is only allowed to be placed on the network
3431 with that same HDCP protection.
3433 12.4. Pro Audio and Video - Link Aggregation
3435 Note: The term "Link Aggregation" is used here as defined by the text
3436 in the following paragraph, i.e. not following a more common Network
3437 Industry definition. Current WG consensus is that this item won't be
3438 directly supported by the DetNet architecture, for example because it
3439 implies guarantee of in-order delivery of packets which conflicts
3440 with the core goal of achieving the lowest possible latency.
3442 For transmitting streams that require more bandwidth than a single
3443 link in the target network can support, link aggregation is a
3444 technique for combining (aggregating) the bandwidth available on
3445 multiple physical links to create a single logical link of the
3446 required bandwidth. However, if aggregation is to be used, the
3447 network controller (or equivalent) must be able to determine the
3448 maximum latency of any path through the aggregate link.
3450 13. Contributors
3452 RFC7322 limits the number of authors listed on the front page of a
3453 draft to a maximum of 5, far fewer than the 20 individuals below who
3454 made important contributions to this draft. The editor wishes to
3455 thank and acknowledge each of the following authors for contributing
3456 text to this draft. See also Section 14.
3458 Craig Gunther (Harman International)
3459 10653 South River Front Parkway, South Jordan,UT 84095
3460 phone +1 801 568-7675, email craig.gunther@harman.com
3462 Pascal Thubert (Cisco Systems, Inc)
3463 Building D, 45 Allee des Ormes - BP1200, MOUGINS
3464 Sophia Antipolis 06254 FRANCE
3465 phone +33 497 23 26 34, email pthubert@cisco.com
3467 Patrick Wetterwald (Cisco Systems)
3468 45 Allees des Ormes, Mougins, 06250 FRANCE
3469 phone +33 4 97 23 26 36, email pwetterw@cisco.com
3471 Jean Raymond (Hydro-Quebec)
3472 1500 University, Montreal, H3A3S7, Canada
3473 phone +1 514 840 3000, email raymond.jean@hydro.qc.ca
3475 Jouni Korhonen (Broadcom Corporation)
3476 3151 Zanker Road, San Jose, 95134, CA, USA
3477 email jouni.nospam@gmail.com
3479 Yu Kaneko (Toshiba)
3480 1 Komukai-Toshiba-cho, Saiwai-ku, Kasasaki-shi, Kanagawa, Japan
3481 email yu1.kaneko@toshiba.co.jp
3483 Subir Das (Vencore Labs)
3484 150 Mount Airy Road, Basking Ridge, New Jersey, 07920, USA
3485 email sdas@appcomsci.com
3487 Yiyong Zha (Huawei Technologies)
3488 email
3490 Balazs Varga (Ericsson)
3491 Konyves Kalman krt. 11/B, Budapest, Hungary, 1097
3492 email balazs.a.varga@ericsson.com
3493 Janos Farkas (Ericsson)
3494 Konyves Kalman krt. 11/B, Budapest, Hungary, 1097
3495 email janos.farkas@ericsson.com
3497 Franz-Josef Goetz (Siemens)
3498 Gleiwitzerstr. 555, Nurnberg, Germany, 90475
3499 email franz-josef.goetz@siemens.com
3501 Juergen Schmitt (Siemens)
3502 Gleiwitzerstr. 555, Nurnberg, Germany, 90475
3503 email juergen.jues.schmitt@siemens.com
3505 Xavier Vilajosana (Worldsensing)
3506 483 Arago, Barcelona, Catalonia, 08013, Spain
3507 email xvilajosana@worldsensing.com
3509 Toktam Mahmoodi (King's College London)
3510 Strand, London WC2R 2LS, United Kingdom
3511 email toktam.mahmoodi@kcl.ac.uk
3513 Spiros Spirou (Intracom Telecom)
3514 19.7 km Markopoulou Ave., Peania, Attiki, 19002, Greece
3515 email spiros.spirou@gmail.com
3517 Petra Vizarreta (Technical University of Munich)
3518 Maxvorstadt, ArcisstraBe 21, Munich, 80333, Germany
3519 email petra.stojsavljevic@tum.de
3521 Daniel Huang (ZTE Corporation, Inc.)
3522 No. 50 Software Avenue, Nanjing, Jiangsu, 210012, P.R. China
3523 email huang.guangping@zte.com.cn
3525 Xuesong Geng (Huawei Technologies)
3526 email gengxuesong@huawei.com
3528 Diego Dujovne (Universidad Diego Portales)
3529 email diego.dujovne@mail.udp.cl
3531 Maik Seewald (Cisco Systems)
3532 email maseewal@cisco.com
3534 14. Acknowledgments
3536 14.1. Pro Audio
3538 This section was derived from draft-gunther-detnet-proaudio-req-01.
3540 The editors would like to acknowledge the help of the following
3541 individuals and the companies they represent:
3543 Jeff Koftinoff, Meyer Sound
3545 Jouni Korhonen, Associate Technical Director, Broadcom
3547 Pascal Thubert, CTAO, Cisco
3549 Kieran Tyrrell, Sienda New Media Technologies GmbH
3551 14.2. Utility Telecom
3553 This section was derived from draft-wetterwald-detnet-utilities-reqs-
3554 02.
3556 Faramarz Maghsoodlou, Ph. D. IoT Connected Industries and Energy
3557 Practice Cisco
3559 Pascal Thubert, CTAO Cisco
3561 14.3. Building Automation Systems
3563 This section was derived from draft-bas-usecase-detnet-00.
3565 14.4. Wireless for Industrial
3567 This section was derived from draft-thubert-6tisch-4detnet-01.
3569 This specification derives from the 6TiSCH architecture, which is the
3570 result of multiple interactions, in particular during the 6TiSCH
3571 (bi)Weekly Interim call, relayed through the 6TiSCH mailing list at
3572 the IETF.
3574 The authors wish to thank: Kris Pister, Thomas Watteyne, Xavier
3575 Vilajosana, Qin Wang, Tom Phinney, Robert Assimiti, Michael
3576 Richardson, Zhuo Chen, Malisa Vucinic, Alfredo Grieco, Martin Turon,
3577 Dominique Barthel, Elvis Vogli, Guillaume Gaillard, Herman Storey,
3578 Maria Rita Palattella, Nicola Accettura, Patrick Wetterwald, Pouria
3579 Zand, Raghuram Sudhaakar, and Shitanshu Shah for their participation
3580 and various contributions.
3582 14.5. Cellular Radio
3584 This section was derived from draft-korhonen-detnet-telreq-00.
3586 14.6. Industrial M2M
3588 The authors would like to thank Feng Chen and Marcel Kiessling for
3589 their comments and suggestions.
3591 14.7. Internet Applications and CoMP
3593 This section was derived from draft-zha-detnet-use-case-00.
3595 This document has benefited from reviews, suggestions, comments and
3596 proposed text provided by the following members, listed in
3597 alphabetical order: Jing Huang, Junru Lin, Lehong Niu and Oilver
3598 Huang.
3600 14.8. Electrical Utilities
3602 The wind power generation use case has been extracted from the study
3603 of Wind Farms conducted within the 5GPPP Virtuwind Project. The
3604 project is funded by the European Union's Horizon 2020 research and
3605 innovation programme under grant agreement No 671648 (VirtuWind).
3607 14.9. Network Slicing
3609 This section was written by Xuesong Geng, who would like to
3610 acknowledge Norm Finn and Mach Chen for their useful comments.
3612 14.10. Mining
3614 This section was written by Diego Dujovne in conjunction with Xavier
3615 Vilasojana.
3617 14.11. Private Blockchain
3619 This section was written by Daniel Huang.
3621 15. Informative References
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3624 Environments",
3625 .
3627 [Ahm14] Ahmed, M. and R. Kim, "Communication network architectures
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3632 ASHRAE, "Annex J to ANSI/ASHRAE 135-1995 - BACnet/IP",
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3635 [CCAMP] IETF, "Common Control and Measurement Plane",
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3638 [CoMP] NGMN Alliance, "RAN EVOLUTION PROJECT COMP EVALUATION AND
3639 ENHANCEMENT", NGMN Alliance NGMN_RANEV_D3_CoMP_Evaluation_
3640 and_Enhancement_v2.0, March 2015,
3641 .
3644 [CONTENT_PROTECTION]
3645 Olsen, D., "1722a Content Protection", 2012,
3646 .
3649 [CPRI] CPRI Cooperation, "Common Public Radio Interface (CPRI);
3650 Interface Specification", CPRI Specification V6.1, July
3651 2014, .
3654 [CPRI-transp]
3655 CPRI TWG, "CPRI requirements for Ethernet Fronthaul",
3656 November 2015,
3657 .
3660 [DCI] Digital Cinema Initiatives, LLC, "DCI Specification,
3661 Version 1.2", 2012, .
3663 [DICE] IETF, "DTLS In Constrained Environments",
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3666 [EA12] Evans, P. and M. Annunziata, "Industrial Internet: Pushing
3667 the Boundaries of Minds and Machines", November 2012.
3669 [eCPRI] IEEE Standards Association, "Common Public Radio
3670 Interface, "Common Public Radio Interface: eCPRI Interface
3671 Specification V1.0", 2017, .
3673 [ESPN_DC2]
3674 Daley, D., "ESPN's DC2 Scales AVB Large", 2014,
3675 .
3678 [flnet] Japan Electrical Manufacturers Association, "JEMA 1479 -
3679 English Edition", September 2012.
3681 [Fronthaul]
3682 Chen, D. and T. Mustala, "Ethernet Fronthaul
3683 Considerations", IEEE 1904.3, February 2015,
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3687 [HART] www.hartcomm.org, "Highway Addressable remote Transducer,
3688 a group of specifications for industrial process and
3689 control devices administered by the HART Foundation".
3691 [I-D.finn-detnet-architecture]
3692 Finn, N. and P. Thubert, "Deterministic Networking
3693 Architecture", draft-finn-detnet-architecture-08 (work in
3694 progress), August 2016.
3696 [I-D.finn-detnet-problem-statement]
3697 Finn, N. and P. Thubert, "Deterministic Networking Problem
3698 Statement", draft-finn-detnet-problem-statement-05 (work
3699 in progress), March 2016.
3701 [I-D.ietf-6tisch-6top-interface]
3702 Wang, Q. and X. Vilajosana, "6TiSCH Operation Sublayer
3703 (6top) Interface", draft-ietf-6tisch-6top-interface-04
3704 (work in progress), July 2015.
3706 [I-D.ietf-6tisch-architecture]
3707 Thubert, P., "An Architecture for IPv6 over the TSCH mode
3708 of IEEE 802.15.4", draft-ietf-6tisch-architecture-13 (work
3709 in progress), November 2017.
3711 [I-D.ietf-6tisch-coap]
3712 Sudhaakar, R. and P. Zand, "6TiSCH Resource Management and
3713 Interaction using CoAP", draft-ietf-6tisch-coap-03 (work
3714 in progress), March 2015.
3716 [I-D.ietf-6tisch-terminology]
3717 Palattella, M., Thubert, P., Watteyne, T., and Q. Wang,
3718 "Terms Used in IPv6 over the TSCH mode of IEEE 802.15.4e",
3719 draft-ietf-6tisch-terminology-10 (work in progress), March
3720 2018.
3722 [I-D.ietf-ipv6-multilink-subnets]
3723 Thaler, D. and C. Huitema, "Multi-link Subnet Support in
3724 IPv6", draft-ietf-ipv6-multilink-subnets-00 (work in
3725 progress), July 2002.
3727 [I-D.ietf-mpls-residence-time]
3728 Mirsky, G., Ruffini, S., Gray, E., Drake, J., Bryant, S.,
3729 and S. Vainshtein, "Residence Time Measurement in MPLS
3730 network", draft-ietf-mpls-residence-time-15 (work in
3731 progress), March 2017.
3733 [I-D.ietf-roll-rpl-industrial-applicability]
3734 Phinney, T., Thubert, P., and R. Assimiti, "RPL
3735 applicability in industrial networks", draft-ietf-roll-
3736 rpl-industrial-applicability-02 (work in progress),
3737 October 2013.
3739 [I-D.ietf-tictoc-1588overmpls]
3740 Davari, S., Oren, A., Bhatia, M., Roberts, P., and L.
3741 Montini, "Transporting Timing messages over MPLS
3742 Networks", draft-ietf-tictoc-1588overmpls-07 (work in
3743 progress), October 2015.
3745 [I-D.kh-spring-ip-ran-use-case]
3746 Khasnabish, B., hu, f., and L. Contreras, "Segment Routing
3747 in IP RAN use case", draft-kh-spring-ip-ran-use-case-02
3748 (work in progress), November 2014.
3750 [I-D.svshah-tsvwg-deterministic-forwarding]
3751 Shah, S. and P. Thubert, "Deterministic Forwarding PHB",
3752 draft-svshah-tsvwg-deterministic-forwarding-04 (work in
3753 progress), August 2015.
3755 [I-D.thubert-6lowpan-backbone-router]
3756 Thubert, P., "6LoWPAN Backbone Router", draft-thubert-
3757 6lowpan-backbone-router-03 (work in progress), February
3758 2013.
3760 [I-D.wang-6tisch-6top-sublayer]
3761 Wang, Q. and X. Vilajosana, "6TiSCH Operation Sublayer
3762 (6top)", draft-wang-6tisch-6top-sublayer-04 (work in
3763 progress), November 2015.
3765 [IEC-60870-5-104]
3766 International Electrotechnical Commission, "International
3767 Standard IEC 60870-5-104: Network access for IEC
3768 60870-5-101 using standard transport profiles", June 2006.
3770 [IEC61400]
3771 "International standard 61400-25: Communications for
3772 monitoring and control of wind power plants", June 2013.
3774 [IEC61850-90-12]
3775 TC57 WG10, IEC., "IEC 61850-90-12 TR: Communication
3776 networks and systems for power utility automation - Part
3777 90-12: Wide area network engineering guidelines", 2015.
3779 [IEC62439-3:2012]
3780 TC65, IEC., "IEC 62439-3: Industrial communication
3781 networks - High availability automation networks - Part 3:
3782 Parallel Redundancy Protocol (PRP) and High-availability
3783 Seamless Redundancy (HSR)", 2012.
3785 [IEEE1588]
3786 IEEE, "IEEE Standard for a Precision Clock Synchronization
3787 Protocol for Networked Measurement and Control Systems",
3788 IEEE Std 1588-2008, 2008,
3789 .
3792 [IEEE1646]
3793 "Communication Delivery Time Performance Requirements for
3794 Electric Power Substation Automation", IEEE Standard
3795 1646-2004 , Apr 2004.
3797 [IEEE1722]
3798 IEEE, "1722-2011 - IEEE Standard for Layer 2 Transport
3799 Protocol for Time Sensitive Applications in a Bridged
3800 Local Area Network", IEEE Std 1722-2011, 2011,
3801 .
3804 [IEEE19143]
3805 IEEE Standards Association, "P1914.3/D3.1 Draft Standard
3806 for Radio over Ethernet Encapsulations and Mappings",
3807 IEEE 1914.3, 2018,
3808 .
3810 [IEEE802.1TSNTG]
3811 IEEE Standards Association, "IEEE 802.1 Time-Sensitive
3812 Networks Task Group", March 2013,
3813 .
3815 [IEEE802154]
3816 IEEE standard for Information Technology, "IEEE std.
3817 802.15.4, Part. 15.4: Wireless Medium Access Control (MAC)
3818 and Physical Layer (PHY) Specifications for Low-Rate
3819 Wireless Personal Area Networks".
3821 [IEEE802154e]
3822 IEEE standard for Information Technology, "IEEE standard
3823 for Information Technology, IEEE std. 802.15.4, Part.
3824 15.4: Wireless Medium Access Control (MAC) and Physical
3825 Layer (PHY) Specifications for Low-Rate Wireless Personal
3826 Area Networks, June 2011 as amended by IEEE std.
3827 802.15.4e, Part. 15.4: Low-Rate Wireless Personal Area
3828 Networks (LR-WPANs) Amendment 1: MAC sublayer", April
3829 2012.
3831 [IEEE8021AS]
3832 IEEE, "Timing and Synchronizations (IEEE 802.1AS-2011)",
3833 IEEE 802.1AS-2001, 2011,
3834 .
3837 [IEEE8021CM]
3838 Farkas, J., "Time-Sensitive Networking for Fronthaul",
3839 Unapproved PAR, PAR for a New IEEE Standard;
3840 IEEE P802.1CM, April 2015,
3841 .
3844 [IEEE8021TSN]
3845 IEEE 802.1, "The charter of the TG is to provide the
3846 specifications that will allow time-synchronized low
3847 latency streaming services through 802 networks.", 2016,
3848 .
3850 [IETFDetNet]
3851 IETF, "Charter for IETF DetNet Working Group", 2015,
3852 .
3854 [ISA100] ISA/ANSI, "ISA100, Wireless Systems for Automation",
3855 .
3857 [ISA100.11a]
3858 ISA/ANSI, "Wireless Systems for Industrial Automation:
3859 Process Control and Related Applications - ISA100.11a-2011
3860 - IEC 62734", 2011, .
3863 [ISO7240-16]
3864 ISO, "ISO 7240-16:2007 Fire detection and alarm systems --
3865 Part 16: Sound system control and indicating equipment",
3866 2007, .
3869 [knx] KNX Association, "ISO/IEC 14543-3 - KNX", November 2006.
3871 [lontalk] ECHELON, "LonTalk(R) Protocol Specification Version 3.0",
3872 1994.
3874 [LTE-Latency]
3875 Johnston, S., "LTE Latency: How does it compare to other
3876 technologies", March 2014,
3877 .
3880 [MEF22.1.1]
3881 MEF, "Mobile Backhaul Phase 2 Amendment 1 -- Small Cells",
3882 MEF 22.1.1, July 2014,
3883 .
3886 [MEF8] MEF, "Implementation Agreement for the Emulation of PDH
3887 Circuits over Metro Ethernet Networks", MEF 8, October
3888 2004,
3889 .
3892 [METIS] METIS, "Scenarios, requirements and KPIs for 5G mobile and
3893 wireless system", ICT-317669-METIS/D1.1 ICT-
3894 317669-METIS/D1.1, April 2013, .
3897 [modbus] Modbus Organization, "MODBUS APPLICATION PROTOCOL
3898 SPECIFICATION V1.1b", December 2006.
3900 [MODBUS] Modbus Organization, Inc., "MODBUS Application Protocol
3901 Specification", Apr 2012.
3903 [net5G] Ericsson, "5G Radio Access, Challenges for 2020 and
3904 Beyond", Ericsson white paper wp-5g, June 2013,
3905 .
3907 [NGMN] NGMN Alliance, "5G White Paper", NGMN 5G White Paper v1.0,
3908 February 2015, .
3911 [NGMN-fronth]
3912 NGMN Alliance, "Fronthaul Requirements for C-RAN", March
3913 2015, .
3916 [OPCXML] OPC Foundation, "OPC XML-Data Access Specification", Dec
3917 2004.
3919 [PCE] IETF, "Path Computation Element",
3920 .
3922 [profibus]
3923 IEC, "IEC 61158 Type 3 - Profibus DP", January 2001.
3925 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
3926 Requirement Levels", BCP 14, RFC 2119,
3927 DOI 10.17487/RFC2119, March 1997,
3928 .
3930 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
3931 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
3932 December 1998, .
3934 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
3935 "Definition of the Differentiated Services Field (DS
3936 Field) in the IPv4 and IPv6 Headers", RFC 2474,
3937 DOI 10.17487/RFC2474, December 1998,
3938 .
3940 [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
3941 Label Switching Architecture", RFC 3031,
3942 DOI 10.17487/RFC3031, January 2001,
3943 .
3945 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
3946 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
3947 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
3948 .
3950 [RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation
3951 Metric for IP Performance Metrics (IPPM)", RFC 3393,
3952 DOI 10.17487/RFC3393, November 2002,
3953 .
3955 [RFC3411] Harrington, D., Presuhn, R., and B. Wijnen, "An
3956 Architecture for Describing Simple Network Management
3957 Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
3958 DOI 10.17487/RFC3411, December 2002,
3959 .
3961 [RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between
3962 Information Models and Data Models", RFC 3444,
3963 DOI 10.17487/RFC3444, January 2003,
3964 .
3966 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
3967 RFC 3972, DOI 10.17487/RFC3972, March 2005,
3968 .
3970 [RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
3971 Edge-to-Edge (PWE3) Architecture", RFC 3985,
3972 DOI 10.17487/RFC3985, March 2005,
3973 .
3975 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
3976 Architecture", RFC 4291, DOI 10.17487/RFC4291, February
3977 2006, .
3979 [RFC4553] Vainshtein, A., Ed. and YJ. Stein, Ed., "Structure-
3980 Agnostic Time Division Multiplexing (TDM) over Packet
3981 (SAToP)", RFC 4553, DOI 10.17487/RFC4553, June 2006,
3982 .
3984 [RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903,
3985 DOI 10.17487/RFC4903, June 2007,
3986 .
3988 [RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6
3989 over Low-Power Wireless Personal Area Networks (6LoWPANs):
3990 Overview, Assumptions, Problem Statement, and Goals",
3991 RFC 4919, DOI 10.17487/RFC4919, August 2007,
3992 .
3994 [RFC5086] Vainshtein, A., Ed., Sasson, I., Metz, E., Frost, T., and
3995 P. Pate, "Structure-Aware Time Division Multiplexed (TDM)
3996 Circuit Emulation Service over Packet Switched Network
3997 (CESoPSN)", RFC 5086, DOI 10.17487/RFC5086, December 2007,
3998 .
4000 [RFC5087] Stein, Y(J)., Shashoua, R., Insler, R., and M. Anavi,
4001 "Time Division Multiplexing over IP (TDMoIP)", RFC 5087,
4002 DOI 10.17487/RFC5087, December 2007,
4003 .
4005 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
4006 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
4007 DOI 10.17487/RFC6282, September 2011,
4008 .
4010 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
4011 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
4012 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
4013 Low-Power and Lossy Networks", RFC 6550,
4014 DOI 10.17487/RFC6550, March 2012,
4015 .
4017 [RFC6551] Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N.,
4018 and D. Barthel, "Routing Metrics Used for Path Calculation
4019 in Low-Power and Lossy Networks", RFC 6551,
4020 DOI 10.17487/RFC6551, March 2012,
4021 .
4023 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
4024 Bormann, "Neighbor Discovery Optimization for IPv6 over
4025 Low-Power Wireless Personal Area Networks (6LoWPANs)",
4026 RFC 6775, DOI 10.17487/RFC6775, November 2012,
4027 .
4029 [RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using
4030 IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the
4031 Internet of Things (IoT): Problem Statement", RFC 7554,
4032 DOI 10.17487/RFC7554, May 2015,
4033 .
4035 [Spe09] Sperotto, A., Sadre, R., Vliet, F., and A. Pras, "A First
4036 Look into SCADA Network Traffic", IP Operations and
4037 Management, p. 518-521. , June 2009.
4039 [SRP_LATENCY]
4040 Gunther, C., "Specifying SRP Latency", 2014,
4041 .
4044 [STUDIO_IP]
4045 Mace, G., "IP Networked Studio Infrastructure for
4046 Synchronized & Real-Time Multimedia Transmissions", 2007,
4047 .
4050 [SyncE] ITU-T, "G.8261 : Timing and synchronization aspects in
4051 packet networks", Recommendation G.8261, August 2013,
4052 .
4054 [TEAS] IETF, "Traffic Engineering Architecture and Signaling",
4055 .
4057 [TR38801] IEEE Standards Association, "3GPP TR 38.801, Technical
4058 Specification Group Radio Access Network; Study on new
4059 radio access technology: Radio access architecture and
4060 interfaces (Release 14)", 2017,
4061 .
4064 [TS23401] 3GPP, "General Packet Radio Service (GPRS) enhancements
4065 for Evolved Universal Terrestrial Radio Access Network
4066 (E-UTRAN) access", 3GPP TS 23.401 10.10.0, March 2013.
4068 [TS25104] 3GPP, "Base Station (BS) radio transmission and reception
4069 (FDD)", 3GPP TS 25.104 3.14.0, March 2007.
4071 [TS36104] 3GPP, "Evolved Universal Terrestrial Radio Access
4072 (E-UTRA); Base Station (BS) radio transmission and
4073 reception", 3GPP TS 36.104 10.11.0, July 2013.
4075 [TS36133] 3GPP, "Evolved Universal Terrestrial Radio Access
4076 (E-UTRA); Requirements for support of radio resource
4077 management", 3GPP TS 36.133 12.7.0, April 2015.
4079 [TS36211] 3GPP, "Evolved Universal Terrestrial Radio Access
4080 (E-UTRA); Physical channels and modulation", 3GPP
4081 TS 36.211 10.7.0, March 2013.
4083 [TS36300] 3GPP, "Evolved Universal Terrestrial Radio Access (E-UTRA)
4084 and Evolved Universal Terrestrial Radio Access Network
4085 (E-UTRAN); Overall description; Stage 2", 3GPP TS 36.300
4086 10.11.0, September 2013.
4088 [TSNTG] IEEE Standards Association, "IEEE 802.1 Time-Sensitive
4089 Networks Task Group", 2013,
4090 .
4092 [UHD-video]
4093 Holub, P., "Ultra-High Definition Videos and Their
4094 Applications over the Network", The 7th International
4095 Symposium on VICTORIES Project PetrHolub_presentation,
4096 October 2014, .
4099 [WirelessHART]
4100 www.hartcomm.org, "Industrial Communication Networks -
4101 Wireless Communication Network and Communication Profiles
4102 - WirelessHART - IEC 62591", 2010.
4104 Author's Address
4106 Ethan Grossman (editor)
4107 Dolby Laboratories, Inc.
4108 1275 Market Street
4109 San Francisco, CA 94103
4110 USA
4112 Phone: +1 415 645 4726
4113 Email: ethan.grossman@dolby.com
4114 URI: http://www.dolby.com