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2 Internet Engineering Task Force E. Grossman, Ed.
3 Internet-Draft DOLBY
4 Intended status: Informational C. Gunther
5 Expires: October 5, 2017 HARMAN
6 P. Thubert
7 P. Wetterwald
8 CISCO
9 J. Raymond
10 HYDRO-QUEBEC
11 J. Korhonen
12 BROADCOM
13 Y. Kaneko
14 Toshiba
15 S. Das
16 Applied Communication Sciences
17 Y. Zha
18 HUAWEI
19 B. Varga
20 J. Farkas
21 Ericsson
22 F. Goetz
23 J. Schmitt
24 Siemens
25 X. Vilajosana
26 Worldsensing
27 T. Mahmoodi
28 King's College London
29 S. Spirou
30 Intracom Telecom
31 P. Vizarreta
32 Technical University of Munich, TUM
33 April 3, 2017
35 Deterministic Networking Use Cases
36 draft-ietf-detnet-use-cases-12
38 Abstract
40 This draft documents requirements in several diverse industries to
41 establish multi-hop paths for characterized flows with deterministic
42 properties. In this context deterministic implies that streams can
43 be established which provide guaranteed bandwidth and latency which
44 can be established from either a Layer 2 or Layer 3 (IP) interface,
45 and which can co-exist on an IP network with best-effort traffic.
47 Additional requirements include optional redundant paths, very high
48 reliability paths, time synchronization, and clock distribution.
50 Industries considered include wireless for industrial applications,
51 professional audio, electrical utilities, building automation
52 systems, radio/mobile access networks, automotive, and gaming.
54 For each case, this document will identify the application, identify
55 representative solutions used today, and what new uses an IETF DetNet
56 solution may enable.
58 Status of This Memo
60 This Internet-Draft is submitted in full conformance with the
61 provisions of BCP 78 and BCP 79.
63 Internet-Drafts are working documents of the Internet Engineering
64 Task Force (IETF). Note that other groups may also distribute
65 working documents as Internet-Drafts. The list of current Internet-
66 Drafts is at http://datatracker.ietf.org/drafts/current/.
68 Internet-Drafts are draft documents valid for a maximum of six months
69 and may be updated, replaced, or obsoleted by other documents at any
70 time. It is inappropriate to use Internet-Drafts as reference
71 material or to cite them other than as "work in progress."
73 This Internet-Draft will expire on October 5, 2017.
75 Copyright Notice
77 Copyright (c) 2017 IETF Trust and the persons identified as the
78 document authors. All rights reserved.
80 This document is subject to BCP 78 and the IETF Trust's Legal
81 Provisions Relating to IETF Documents
82 (http://trustee.ietf.org/license-info) in effect on the date of
83 publication of this document. Please review these documents
84 carefully, as they describe your rights and restrictions with respect
85 to this document. Code Components extracted from this document must
86 include Simplified BSD License text as described in Section 4.e of
87 the Trust Legal Provisions and are provided without warranty as
88 described in the Simplified BSD License.
90 Table of Contents
92 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5
93 2. Pro Audio and Video . . . . . . . . . . . . . . . . . . . . . 6
94 2.1. Use Case Description . . . . . . . . . . . . . . . . . . 6
95 2.1.1. Uninterrupted Stream Playback . . . . . . . . . . . . 7
96 2.1.2. Synchronized Stream Playback . . . . . . . . . . . . 7
97 2.1.3. Sound Reinforcement . . . . . . . . . . . . . . . . . 8
98 2.1.4. Deterministic Time to Establish Streaming . . . . . . 8
99 2.1.5. Secure Transmission . . . . . . . . . . . . . . . . . 8
100 2.1.5.1. Safety . . . . . . . . . . . . . . . . . . . . . 8
101 2.2. Pro Audio Today . . . . . . . . . . . . . . . . . . . . . 9
102 2.3. Pro Audio Future . . . . . . . . . . . . . . . . . . . . 9
103 2.3.1. Layer 3 Interconnecting Layer 2 Islands . . . . . . . 9
104 2.3.2. High Reliability Stream Paths . . . . . . . . . . . . 9
105 2.3.3. Integration of Reserved Streams into IT Networks . . 9
106 2.3.4. Use of Unused Reservations by Best-Effort Traffic . . 10
107 2.3.5. Traffic Segregation . . . . . . . . . . . . . . . . . 10
108 2.3.5.1. Packet Forwarding Rules, VLANs and Subnets . . . 10
109 2.3.5.2. Multicast Addressing (IPv4 and IPv6) . . . . . . 11
110 2.3.6. Latency Optimization by a Central Controller . . . . 11
111 2.3.7. Reduced Device Cost Due To Reduced Buffer Memory . . 11
112 2.4. Pro Audio Asks . . . . . . . . . . . . . . . . . . . . . 12
113 3. Electrical Utilities . . . . . . . . . . . . . . . . . . . . 12
114 3.1. Use Case Description . . . . . . . . . . . . . . . . . . 12
115 3.1.1. Transmission Use Cases . . . . . . . . . . . . . . . 12
116 3.1.1.1. Protection . . . . . . . . . . . . . . . . . . . 12
117 3.1.1.2. Intra-Substation Process Bus Communications . . . 18
118 3.1.1.3. Wide Area Monitoring and Control Systems . . . . 19
119 3.1.1.4. IEC 61850 WAN engineering guidelines requirement
120 classification . . . . . . . . . . . . . . . . . 20
121 3.1.2. Generation Use Case . . . . . . . . . . . . . . . . . 21
122 3.1.2.1. Control of the Generated Power . . . . . . . . . 21
123 3.1.2.2. Control of the Generation Infrastructure . . . . 22
124 3.1.3. Distribution use case . . . . . . . . . . . . . . . . 27
125 3.1.3.1. Fault Location Isolation and Service Restoration
126 (FLISR) . . . . . . . . . . . . . . . . . . . . . 27
127 3.2. Electrical Utilities Today . . . . . . . . . . . . . . . 28
128 3.2.1. Security Current Practices and Limitations . . . . . 28
129 3.3. Electrical Utilities Future . . . . . . . . . . . . . . . 30
130 3.3.1. Migration to Packet-Switched Network . . . . . . . . 31
131 3.3.2. Telecommunications Trends . . . . . . . . . . . . . . 31
132 3.3.2.1. General Telecommunications Requirements . . . . . 31
133 3.3.2.2. Specific Network topologies of Smart Grid
134 Applications . . . . . . . . . . . . . . . . . . 32
135 3.3.2.3. Precision Time Protocol . . . . . . . . . . . . . 33
136 3.3.3. Security Trends in Utility Networks . . . . . . . . . 34
137 3.4. Electrical Utilities Asks . . . . . . . . . . . . . . . . 36
138 4. Building Automation Systems . . . . . . . . . . . . . . . . . 36
139 4.1. Use Case Description . . . . . . . . . . . . . . . . . . 36
140 4.2. Building Automation Systems Today . . . . . . . . . . . . 37
141 4.2.1. BAS Architecture . . . . . . . . . . . . . . . . . . 37
142 4.2.2. BAS Deployment Model . . . . . . . . . . . . . . . . 38
143 4.2.3. Use Cases for Field Networks . . . . . . . . . . . . 40
144 4.2.3.1. Environmental Monitoring . . . . . . . . . . . . 40
145 4.2.3.2. Fire Detection . . . . . . . . . . . . . . . . . 40
146 4.2.3.3. Feedback Control . . . . . . . . . . . . . . . . 41
147 4.2.4. Security Considerations . . . . . . . . . . . . . . . 41
148 4.3. BAS Future . . . . . . . . . . . . . . . . . . . . . . . 41
149 4.4. BAS Asks . . . . . . . . . . . . . . . . . . . . . . . . 42
150 5. Wireless for Industrial . . . . . . . . . . . . . . . . . . . 42
151 5.1. Use Case Description . . . . . . . . . . . . . . . . . . 42
152 5.1.1. Network Convergence using 6TiSCH . . . . . . . . . . 43
153 5.1.2. Common Protocol Development for 6TiSCH . . . . . . . 43
154 5.2. Wireless Industrial Today . . . . . . . . . . . . . . . . 44
155 5.3. Wireless Industrial Future . . . . . . . . . . . . . . . 44
156 5.3.1. Unified Wireless Network and Management . . . . . . . 44
157 5.3.1.1. PCE and 6TiSCH ARQ Retries . . . . . . . . . . . 46
158 5.3.2. Schedule Management by a PCE . . . . . . . . . . . . 47
159 5.3.2.1. PCE Commands and 6TiSCH CoAP Requests . . . . . . 47
160 5.3.2.2. 6TiSCH IP Interface . . . . . . . . . . . . . . . 48
161 5.3.3. 6TiSCH Security Considerations . . . . . . . . . . . 49
162 5.4. Wireless Industrial Asks . . . . . . . . . . . . . . . . 49
163 6. Cellular Radio . . . . . . . . . . . . . . . . . . . . . . . 49
164 6.1. Use Case Description . . . . . . . . . . . . . . . . . . 49
165 6.1.1. Network Architecture . . . . . . . . . . . . . . . . 49
166 6.1.2. Delay Constraints . . . . . . . . . . . . . . . . . . 50
167 6.1.3. Time Synchronization Constraints . . . . . . . . . . 51
168 6.1.4. Transport Loss Constraints . . . . . . . . . . . . . 53
169 6.1.5. Security Considerations . . . . . . . . . . . . . . . 53
170 6.2. Cellular Radio Networks Today . . . . . . . . . . . . . . 54
171 6.2.1. Fronthaul . . . . . . . . . . . . . . . . . . . . . . 54
172 6.2.2. Midhaul and Backhaul . . . . . . . . . . . . . . . . 54
173 6.3. Cellular Radio Networks Future . . . . . . . . . . . . . 55
174 6.4. Cellular Radio Networks Asks . . . . . . . . . . . . . . 57
175 7. Industrial M2M . . . . . . . . . . . . . . . . . . . . . . . 57
176 7.1. Use Case Description . . . . . . . . . . . . . . . . . . 57
177 7.2. Industrial M2M Communication Today . . . . . . . . . . . 58
178 7.2.1. Transport Parameters . . . . . . . . . . . . . . . . 59
179 7.2.2. Stream Creation and Destruction . . . . . . . . . . . 60
180 7.3. Industrial M2M Future . . . . . . . . . . . . . . . . . . 60
181 7.4. Industrial M2M Asks . . . . . . . . . . . . . . . . . . . 60
182 8. Use Case Common Themes . . . . . . . . . . . . . . . . . . . 60
183 8.1. Unified, standards-based network . . . . . . . . . . . . 61
184 8.1.1. Extensions to Ethernet . . . . . . . . . . . . . . . 61
185 8.1.2. Centrally Administered . . . . . . . . . . . . . . . 61
186 8.1.3. Standardized Data Flow Information Models . . . . . . 61
187 8.1.4. L2 and L3 Integration . . . . . . . . . . . . . . . . 61
188 8.1.5. Guaranteed End-to-End Delivery . . . . . . . . . . . 61
189 8.1.6. Replacement for Multiple Proprietary Deterministic
190 Networks . . . . . . . . . . . . . . . . . . . . . . 61
191 8.1.7. Mix of Deterministic and Best-Effort Traffic . . . . 62
192 8.1.8. Unused Reserved BW to be Available to Best Effort
193 Traffic . . . . . . . . . . . . . . . . . . . . . . . 62
195 8.1.9. Lower Cost, Multi-Vendor Solutions . . . . . . . . . 62
196 8.2. Scalable Size . . . . . . . . . . . . . . . . . . . . . . 62
197 8.3. Scalable Timing Parameters and Accuracy . . . . . . . . . 62
198 8.3.1. Bounded Latency . . . . . . . . . . . . . . . . . . . 62
199 8.3.2. Low Latency . . . . . . . . . . . . . . . . . . . . . 63
200 8.3.3. Symmetrical Path Delays . . . . . . . . . . . . . . . 63
201 8.4. High Reliability and Availability . . . . . . . . . . . . 63
202 8.5. Security . . . . . . . . . . . . . . . . . . . . . . . . 63
203 8.6. Deterministic Flows . . . . . . . . . . . . . . . . . . . 64
204 9. Use Cases Explicitly Out of Scope for DetNet . . . . . . . . 64
205 9.1. DetNet Scope Limitations . . . . . . . . . . . . . . . . 64
206 9.2. Internet-based Applications . . . . . . . . . . . . . . . 65
207 9.2.1. Use Case Description . . . . . . . . . . . . . . . . 65
208 9.2.1.1. Media Content Delivery . . . . . . . . . . . . . 65
209 9.2.1.2. Online Gaming . . . . . . . . . . . . . . . . . . 65
210 9.2.1.3. Virtual Reality . . . . . . . . . . . . . . . . . 65
211 9.2.2. Internet-Based Applications Today . . . . . . . . . . 65
212 9.2.3. Internet-Based Applications Future . . . . . . . . . 65
213 9.2.4. Internet-Based Applications Asks . . . . . . . . . . 66
214 9.3. Pro Audio and Video - Digital Rights Management (DRM) . . 66
215 9.4. Pro Audio and Video - Link Aggregation . . . . . . . . . 66
216 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 67
217 10.1. Pro Audio . . . . . . . . . . . . . . . . . . . . . . . 67
218 10.2. Utility Telecom . . . . . . . . . . . . . . . . . . . . 67
219 10.3. Building Automation Systems . . . . . . . . . . . . . . 67
220 10.4. Wireless for Industrial . . . . . . . . . . . . . . . . 67
221 10.5. Cellular Radio . . . . . . . . . . . . . . . . . . . . . 68
222 10.6. Industrial M2M . . . . . . . . . . . . . . . . . . . . . 68
223 10.7. Internet Applications and CoMP . . . . . . . . . . . . . 68
224 10.8. Electrical Utilities . . . . . . . . . . . . . . . . . . 68
225 11. Informative References . . . . . . . . . . . . . . . . . . . 68
226 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 78
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.
336 This implies that all sinks must maintain a common time reference of
337 sufficient accuracy, which can be achieved by any of various
338 techniques.
340 This type of architecture is commonly implemented using a central
341 controller that determines path delays and arbitrates buffering
342 delays.
344 2.1.3. Sound Reinforcement
346 Consider the latency (delay) from when a person speaks into a
347 microphone to when their voice emerges from the speaker. If this
348 delay is longer than about 10-15 milliseconds it is noticeable and
349 can make a sound reinforcement system unusable (see slide 6 of
350 [SRP_LATENCY]). (If you have ever tried to speak in the presence of
351 a delayed echo of your voice you may know this experience).
353 Note that the 15ms latency bound includes all parts of the signal
354 path, not just the network, so the network latency must be
355 significantly less than 15ms.
357 In some cases local performers must perform in synchrony with a
358 remote broadcast. In such cases the latencies of the broadcast
359 stream and the local performer must be adjusted to match each other,
360 with a worst case of one video frame (33ms for NTSC video).
362 In cases where audio phase is a consideration, for example beam-
363 forming using multiple speakers, latency requirements can be in the
364 10 microsecond range (1 audio sample at 96kHz).
366 2.1.4. Deterministic Time to Establish Streaming
368 Note: The WG has decided that guidelines for deterministic time to
369 establish stream startup is not within scope of DetNet. If bounded
370 timing of establishing or re-establish streams is required in a given
371 use case, it is up to the application/system to achieve this. (The
372 supporting text from this section has been removed as of draft 12).
374 2.1.5. Secure Transmission
376 2.1.5.1. Safety
378 Professional audio systems can include amplifiers that are capable of
379 generating hundreds or thousands of watts of audio power which if
380 used incorrectly can cause hearing damage to those in the vicinity.
381 Apart from the usual care required by the systems operators to
382 prevent such incidents, the network traffic that controls these
383 devices must be secured (as with any sensitive application traffic).
385 2.2. Pro Audio Today
387 Some proprietary systems have been created which enable deterministic
388 streams at Layer 3 however they are "engineered networks" which
389 require careful configuration to operate, often require that the
390 system be over-provisioned, and it is implied that all devices on the
391 network voluntarily play by the rules of that network. To enable
392 these industries to successfully transition to an interoperable
393 multi-vendor packet-based infrastructure requires effective open
394 standards, and we believe that establishing relevant IETF standards
395 is a crucial factor.
397 2.3. Pro Audio Future
399 2.3.1. Layer 3 Interconnecting Layer 2 Islands
401 It would be valuable to enable IP to connect multiple Layer 2 LANs.
403 As an example, ESPN recently constructed a state-of-the-art 194,000
404 sq ft, $125 million broadcast studio called DC2. The DC2 network is
405 capable of handling 46 Tbps of throughput with 60,000 simultaneous
406 signals. Inside the facility are 1,100 miles of fiber feeding four
407 audio control rooms (see [ESPN_DC2] ).
409 In designing DC2 they replaced as much point-to-point technology as
410 they could with packet-based technology. They constructed seven
411 individual studios using layer 2 LANS (using IEEE 802.1 AVB) that
412 were entirely effective at routing audio within the LANs. However to
413 interconnect these layer 2 LAN islands together they ended up using
414 dedicated paths in a custom SDN (Software Defined Networking) router
415 because there is no standards-based routing solution available.
417 2.3.2. High Reliability Stream Paths
419 On-air and other live media streams are often backed up with
420 redundant links that seamlessly act to deliver the content when the
421 primary link fails for any reason. In point-to-point systems this is
422 provided by an additional point-to-point link; the analogous
423 requirement in a packet-based system is to provide an alternate path
424 through the network such that no individual link can bring down the
425 system.
427 2.3.3. Integration of Reserved Streams into IT Networks
429 A commonly cited goal of moving to a packet based media
430 infrastructure is that costs can be reduced by using off the shelf,
431 commodity network hardware. In addition, economy of scale can be
432 realized by combining media infrastructure with IT infrastructure.
434 In keeping with these goals, stream reservation technology should be
435 compatible with existing protocols, and not compromise use of the
436 network for best effort (non-time-sensitive) traffic.
438 2.3.4. Use of Unused Reservations by Best-Effort Traffic
440 In cases where stream bandwidth is reserved but not currently used
441 (or is under-utilized) that bandwidth must be available to best-
442 effort (i.e. non-time-sensitive) traffic. For example a single
443 stream may be nailed up (reserved) for specific media content that
444 needs to be presented at different times of the day, ensuring timely
445 delivery of that content, yet in between those times the full
446 bandwidth of the network can be utilized for best-effort tasks such
447 as file transfers.
449 This also addresses a concern of IT network administrators that are
450 considering adding reserved bandwidth traffic to their networks that
451 ("users will reserve large quantities of bandwidth and then never un-
452 reserve it even though they are not using it, and soon the network
453 will have no bandwidth left").
455 2.3.5. Traffic Segregation
457 Note: It is still under WG discussion whether this topic will be
458 addressed by DetNet.
460 Sink devices may be low cost devices with limited processing power.
461 In order to not overwhelm the CPUs in these devices it is important
462 to limit the amount of traffic that these devices must process.
464 As an example, consider the use of individual seat speakers in a
465 cinema. These speakers are typically required to be cost reduced
466 since the quantities in a single theater can reach hundreds of seats.
467 Discovery protocols alone in a one thousand seat theater can generate
468 enough broadcast traffic to overwhelm a low powered CPU. Thus an
469 installation like this will benefit greatly from some type of traffic
470 segregation that can define groups of seats to reduce traffic within
471 each group. All seats in the theater must still be able to
472 communicate with a central controller.
474 There are many techniques that can be used to support this
475 requirement including (but not limited to) the following examples.
477 2.3.5.1. Packet Forwarding Rules, VLANs and Subnets
479 Packet forwarding rules can be used to eliminate some extraneous
480 streaming traffic from reaching potentially low powered sink devices,
481 however there may be other types of broadcast traffic that should be
482 eliminated using other means for example VLANs or IP subnets.
484 2.3.5.2. Multicast Addressing (IPv4 and IPv6)
486 Multicast addressing is commonly used to keep bandwidth utilization
487 of shared links to a minimum.
489 Because of the MAC Address forwarding nature of Layer 2 bridges it is
490 important that a multicast MAC address is only associated with one
491 stream. This will prevent reservations from forwarding packets from
492 one stream down a path that has no interested sinks simply because
493 there is another stream on that same path that shares the same
494 multicast MAC address.
496 Since each multicast MAC Address can represent 32 different IPv4
497 multicast addresses there must be a process put in place to make sure
498 this does not occur. Requiring use of IPv6 address can achieve this,
499 however due to their continued prevalence, solutions that are
500 effective for IPv4 installations are also required.
502 2.3.6. Latency Optimization by a Central Controller
504 A central network controller might also perform optimizations based
505 on the individual path delays, for example sinks that are closer to
506 the source can inform the controller that they can accept greater
507 latency since they will be buffering packets to match presentation
508 times of farther away sinks. The controller might then move a stream
509 reservation on a short path to a longer path in order to free up
510 bandwidth for other critical streams on that short path. See slides
511 3-5 of [SRP_LATENCY].
513 Additional optimization can be achieved in cases where sinks have
514 differing latency requirements, for example in a live outdoor concert
515 the speaker sinks have stricter latency requirements than the
516 recording hardware sinks. See slide 7 of [SRP_LATENCY].
518 2.3.7. Reduced Device Cost Due To Reduced Buffer Memory
520 Device cost can be reduced in a system with guaranteed reservations
521 with a small bounded latency due to the reduced requirements for
522 buffering (i.e. memory) on sink devices. For example, a theme park
523 might broadcast a live event across the globe via a layer 3 protocol;
524 in such cases the size of the buffers required is proportional to the
525 latency bounds and jitter caused by delivery, which depends on the
526 worst case segment of the end-to-end network path. For example on
527 todays open internet the latency is typically unacceptable for audio
528 and video streaming without many seconds of buffering. In such
529 scenarios a single gateway device at the local network that receives
530 the feed from the remote site would provide the expensive buffering
531 required to mask the latency and jitter issues associated with long
532 distance delivery. Sink devices in the local location would have no
533 additional buffering requirements, and thus no additional costs,
534 beyond those required for delivery of local content. The sink device
535 would be receiving the identical packets as those sent by the source
536 and would be unaware that there were any latency or jitter issues
537 along the path.
539 2.4. Pro Audio Asks
541 o Layer 3 routing on top of AVB (and/or other high QoS networks)
543 o Content delivery with bounded, lowest possible latency
545 o IntServ and DiffServ integration with AVB (where practical)
547 o Single network for A/V and IT traffic
549 o Standards-based, interoperable, multi-vendor
551 o IT department friendly
553 o Enterprise-wide networks (e.g. size of San Francisco but not the
554 whole Internet (yet...))
556 3. Electrical Utilities
558 3.1. Use Case Description
560 Many systems that an electrical utility deploys today rely on high
561 availability and deterministic behavior of the underlying networks.
562 Here we present use cases in Transmission, Generation and
563 Distribution, including key timing and reliability metrics. We also
564 discuss security issues and industry trends which affect the
565 architecture of next generation utility networks
567 3.1.1. Transmission Use Cases
569 3.1.1.1. Protection
571 Protection means not only the protection of human operators but also
572 the protection of the electrical equipment and the preservation of
573 the stability and frequency of the grid. If a fault occurs in the
574 transmission or distribution of electricity then severe damage can
575 occur to human operators, electrical equipment and the grid itself,
576 leading to blackouts.
578 Communication links in conjunction with protection relays are used to
579 selectively isolate faults on high voltage lines, transformers,
580 reactors and other important electrical equipment. The role of the
581 teleprotection system is to selectively disconnect a faulty part by
582 transferring command signals within the shortest possible time.
584 3.1.1.1.1. Key Criteria
586 The key criteria for measuring teleprotection performance are command
587 transmission time, dependability and security. These criteria are
588 defined by the IEC standard 60834 as follows:
590 o Transmission time (Speed): The time between the moment where state
591 changes at the transmitter input and the moment of the
592 corresponding change at the receiver output, including propagation
593 delay. Overall operating time for a teleprotection system
594 includes the time for initiating the command at the transmitting
595 end, the propagation delay over the network (including equipments)
596 and the selection and decision time at the receiving end,
597 including any additional delay due to a noisy environment.
599 o Dependability: The ability to issue and receive valid commands in
600 the presence of interference and/or noise, by minimizing the
601 probability of missing command (PMC). Dependability targets are
602 typically set for a specific bit error rate (BER) level.
604 o Security: The ability to prevent false tripping due to a noisy
605 environment, by minimizing the probability of unwanted commands
606 (PUC). Security targets are also set for a specific bit error
607 rate (BER) level.
609 Additional elements of the the teleprotection system that impact its
610 performance include:
612 o Network bandwidth
614 o Failure recovery capacity (aka resiliency)
616 3.1.1.1.2. Fault Detection and Clearance Timing
618 Most power line equipment can tolerate short circuits or faults for
619 up to approximately five power cycles before sustaining irreversible
620 damage or affecting other segments in the network. This translates
621 to total fault clearance time of 100ms. As a safety precaution,
622 however, actual operation time of protection systems is limited to
623 70- 80 percent of this period, including fault recognition time,
624 command transmission time and line breaker switching time.
626 Some system components, such as large electromechanical switches,
627 require particularly long time to operate and take up the majority of
628 the total clearance time, leaving only a 10ms window for the
629 telecommunications part of the protection scheme, independent of the
630 distance to travel. Given the sensitivity of the issue, new networks
631 impose requirements that are even more stringent: IEC standard 61850
632 limits the transfer time for protection messages to 1/4 - 1/2 cycle
633 or 4 - 8ms (for 60Hz lines) for the most critical messages.
635 3.1.1.1.3. Symmetric Channel Delay
637 Note: It is currently under WG discussion whether symmetric path
638 delays are to be guaranteed by DetNet.
640 Teleprotection channels which are differential must be synchronous,
641 which means that any delays on the transmit and receive paths must
642 match each other. Teleprotection systems ideally support zero
643 asymmetric delay; typical legacy relays can tolerate delay
644 discrepancies of up to 750us.
646 Some tools available for lowering delay variation below this
647 threshold are:
649 o For legacy systems using Time Division Multiplexing (TDM), jitter
650 buffers at the multiplexers on each end of the line can be used to
651 offset delay variation by queuing sent and received packets. The
652 length of the queues must balance the need to regulate the rate of
653 transmission with the need to limit overall delay, as larger
654 buffers result in increased latency.
656 o For jitter-prone IP packet networks, traffic management tools can
657 ensure that the teleprotection signals receive the highest
658 transmission priority to minimize jitter.
660 o Standard packet-based synchronization technologies, such as
661 1588-2008 Precision Time Protocol (PTP) and Synchronous Ethernet
662 (Sync-E), can help keep networks stable by maintaining a highly
663 accurate clock source on the various network devices.
665 3.1.1.1.4. Teleprotection Network Requirements (IEC 61850)
667 The following table captures the main network metrics as based on the
668 IEC 61850 standard.
670 +-----------------------------+-------------------------------------+
671 | Teleprotection Requirement | Attribute |
672 +-----------------------------+-------------------------------------+
673 | One way maximum delay | 4-10 ms |
674 | Asymetric delay required | Yes |
675 | Maximum jitter | less than 250 us (750 us for legacy |
676 | | IED) |
677 | Topology | Point to point, point to Multi- |
678 | | point |
679 | Availability | 99.9999 |
680 | precise timing required | Yes |
681 | Recovery time on node | less than 50ms - hitless |
682 | failure | |
683 | performance management | Yes, Mandatory |
684 | Redundancy | Yes |
685 | Packet loss | 0.1% to 1% |
686 +-----------------------------+-------------------------------------+
688 Table 1: Teleprotection network requirements
690 3.1.1.1.5. Inter-Trip Protection scheme
692 "Inter-tripping" is the signal-controlled tripping of a circuit
693 breaker to complete the isolation of a circuit or piece of apparatus
694 in concert with the tripping of other circuit breakers.
696 +--------------------------------+----------------------------------+
697 | Inter-Trip protection | Attribute |
698 | Requirement | |
699 +--------------------------------+----------------------------------+
700 | One way maximum delay | 5 ms |
701 | Asymetric delay required | No |
702 | Maximum jitter | Not critical |
703 | Topology | Point to point, point to Multi- |
704 | | point |
705 | Bandwidth | 64 Kbps |
706 | Availability | 99.9999 |
707 | precise timing required | Yes |
708 | Recovery time on node failure | less than 50ms - hitless |
709 | performance management | Yes, Mandatory |
710 | Redundancy | Yes |
711 | Packet loss | 0.1% |
712 +--------------------------------+----------------------------------+
714 Table 2: Inter-Trip protection network requirements
716 3.1.1.1.6. Current Differential Protection Scheme
718 Current differential protection is commonly used for line protection,
719 and is typical for protecting parallel circuits. At both end of the
720 lines the current is measured by the differential relays, and both
721 relays will trip the circuit breaker if the current going into the
722 line does not equal the current going out of the line. This type of
723 protection scheme assumes some form of communications being present
724 between the relays at both end of the line, to allow both relays to
725 compare measured current values. Line differential protection
726 schemes assume a very low telecommunications delay between both
727 relays, often as low as 5ms. Moreover, as those systems are often
728 not time-synchronized, they also assume symmetric telecommunications
729 paths with constant delay, which allows comparing current measurement
730 values taken at the exact same time.
732 +----------------------------------+--------------------------------+
733 | Current Differential protection | Attribute |
734 | Requirement | |
735 +----------------------------------+--------------------------------+
736 | One way maximum delay | 5 ms |
737 | Asymetric delay Required | Yes |
738 | Maximum jitter | less than 250 us (750us for |
739 | | legacy IED) |
740 | Topology | Point to point, point to |
741 | | Multi-point |
742 | Bandwidth | 64 Kbps |
743 | Availability | 99.9999 |
744 | precise timing required | Yes |
745 | Recovery time on node failure | less than 50ms - hitless |
746 | performance management | Yes, Mandatory |
747 | Redundancy | Yes |
748 | Packet loss | 0.1% |
749 +----------------------------------+--------------------------------+
751 Table 3: Current Differential Protection metrics
753 3.1.1.1.7. Distance Protection Scheme
755 Distance (Impedance Relay) protection scheme is based on voltage and
756 current measurements. The network metrics are similar (but not
757 identical to) Current Differential protection.
759 +-------------------------------+-----------------------------------+
760 | Distance protection | Attribute |
761 | Requirement | |
762 +-------------------------------+-----------------------------------+
763 | One way maximum delay | 5 ms |
764 | Asymetric delay Required | No |
765 | Maximum jitter | Not critical |
766 | Topology | Point to point, point to Multi- |
767 | | point |
768 | Bandwidth | 64 Kbps |
769 | Availability | 99.9999 |
770 | precise timing required | Yes |
771 | Recovery time on node failure | less than 50ms - hitless |
772 | performance management | Yes, Mandatory |
773 | Redundancy | Yes |
774 | Packet loss | 0.1% |
775 +-------------------------------+-----------------------------------+
777 Table 4: Distance Protection requirements
779 3.1.1.1.8. Inter-Substation Protection Signaling
781 This use case describes the exchange of Sampled Value and/or GOOSE
782 (Generic Object Oriented Substation Events) message between
783 Intelligent Electronic Devices (IED) in two substations for
784 protection and tripping coordination. The two IEDs are in a master-
785 slave mode.
787 The Current Transformer or Voltage Transformer (CT/VT) in one
788 substation sends the sampled analog voltage or current value to the
789 Merging Unit (MU) over hard wire. The MU sends the time-synchronized
790 61850-9-2 sampled values to the slave IED. The slave IED forwards
791 the information to the Master IED in the other substation. The
792 master IED makes the determination (for example based on sampled
793 value differentials) to send a trip command to the originating IED.
794 Once the slave IED/Relay receives the GOOSE trip for breaker
795 tripping, it opens the breaker. It then sends a confirmation message
796 back to the master. All data exchanges between IEDs are either
797 through Sampled Value and/or GOOSE messages.
799 +----------------------------------+--------------------------------+
800 | Inter-Substation protection | Attribute |
801 | Requirement | |
802 +----------------------------------+--------------------------------+
803 | One way maximum delay | 5 ms |
804 | Asymetric delay Required | No |
805 | Maximum jitter | Not critical |
806 | Topology | Point to point, point to |
807 | | Multi-point |
808 | Bandwidth | 64 Kbps |
809 | Availability | 99.9999 |
810 | precise timing required | Yes |
811 | Recovery time on node failure | less than 50ms - hitless |
812 | performance management | Yes, Mandatory |
813 | Redundancy | Yes |
814 | Packet loss | 1% |
815 +----------------------------------+--------------------------------+
817 Table 5: Inter-Substation Protection requirements
819 3.1.1.2. Intra-Substation Process Bus Communications
821 This use case describes the data flow from the CT/VT to the IEDs in
822 the substation via the MU. The CT/VT in the substation send the
823 sampled value (analog voltage or current) to the MU over hard wire.
824 The MU sends the time-synchronized 61850-9-2 sampled values to the
825 IEDs in the substation in GOOSE message format. The GPS Master Clock
826 can send 1PPS or IRIG-B format to the MU through a serial port or
827 IEEE 1588 protocol via a network. Process bus communication using
828 61850 simplifies connectivity within the substation and removes the
829 requirement for multiple serial connections and removes the slow
830 serial bus architectures that are typically used. This also ensures
831 increased flexibility and increased speed with the use of multicast
832 messaging between multiple devices.
834 +----------------------------------+--------------------------------+
835 | Intra-Substation protection | Attribute |
836 | Requirement | |
837 +----------------------------------+--------------------------------+
838 | One way maximum delay | 5 ms |
839 | Asymetric delay Required | No |
840 | Maximum jitter | Not critical |
841 | Topology | Point to point, point to |
842 | | Multi-point |
843 | Bandwidth | 64 Kbps |
844 | Availability | 99.9999 |
845 | precise timing required | Yes |
846 | Recovery time on Node failure | less than 50ms - hitless |
847 | performance management | Yes, Mandatory |
848 | Redundancy | Yes - No |
849 | Packet loss | 0.1% |
850 +----------------------------------+--------------------------------+
852 Table 6: Intra-Substation Protection requirements
854 3.1.1.3. Wide Area Monitoring and Control Systems
856 The application of synchrophasor measurement data from Phasor
857 Measurement Units (PMU) to Wide Area Monitoring and Control Systems
858 promises to provide important new capabilities for improving system
859 stability. Access to PMU data enables more timely situational
860 awareness over larger portions of the grid than what has been
861 possible historically with normal SCADA (Supervisory Control and Data
862 Acquisition) data. Handling the volume and real-time nature of
863 synchrophasor data presents unique challenges for existing
864 application architectures. Wide Area management System (WAMS) makes
865 it possible for the condition of the bulk power system to be observed
866 and understood in real-time so that protective, preventative, or
867 corrective action can be taken. Because of the very high sampling
868 rate of measurements and the strict requirement for time
869 synchronization of the samples, WAMS has stringent telecommunications
870 requirements in an IP network that are captured in the following
871 table:
873 +----------------------+--------------------------------------------+
874 | WAMS Requirement | Attribute |
875 +----------------------+--------------------------------------------+
876 | One way maximum | 50 ms |
877 | delay | |
878 | Asymetric delay | No |
879 | Required | |
880 | Maximum jitter | Not critical |
881 | Topology | Point to point, point to Multi-point, |
882 | | Multi-point to Multi-point |
883 | Bandwidth | 100 Kbps |
884 | Availability | 99.9999 |
885 | precise timing | Yes |
886 | required | |
887 | Recovery time on | less than 50ms - hitless |
888 | Node failure | |
889 | performance | Yes, Mandatory |
890 | management | |
891 | Redundancy | Yes |
892 | Packet loss | 1% |
893 | Consecutive Packet | At least 1 packet per application cycle |
894 | Loss | must be received. |
895 +----------------------+--------------------------------------------+
897 Table 7: WAMS Special Communication Requirements
899 3.1.1.4. IEC 61850 WAN engineering guidelines requirement
900 classification
902 The IEC (International Electrotechnical Commission) has recently
903 published a Technical Report which offers guidelines on how to define
904 and deploy Wide Area Networks for the interconnections of electric
905 substations, generation plants and SCADA operation centers. The IEC
906 61850-90-12 is providing a classification of WAN communication
907 requirements into 4 classes. Table 8 summarizes these requirements:
909 +----------------+------------+------------+------------+-----------+
910 | WAN | Class WA | Class WB | Class WC | Class WD |
911 | Requirement | | | | |
912 +----------------+------------+------------+------------+-----------+
913 | Application | EHV (Extra | HV (High | MV (Medium | General |
914 | field | High | Voltage) | Voltage) | purpose |
915 | | Voltage) | | | |
916 | Latency | 5 ms | 10 ms | 100 ms | > 100 ms |
917 | Jitter | 10 us | 100 us | 1 ms | 10 ms |
918 | Latency | 100 us | 1 ms | 10 ms | 100 ms |
919 | Asymetry | | | | |
920 | Time Accuracy | 1 us | 10 us | 100 us | 10 to 100 |
921 | | | | | ms |
922 | Bit Error rate | 10-7 to | 10-5 to | 10-3 | |
923 | | 10-6 | 10-4 | | |
924 | Unavailability | 10-7 to | 10-5 to | 10-3 | |
925 | | 10-6 | 10-4 | | |
926 | Recovery delay | Zero | 50 ms | 5 s | 50 s |
927 | Cyber security | extremely | High | Medium | Medium |
928 | | high | | | |
929 +----------------+------------+------------+------------+-----------+
931 Table 8: 61850-90-12 Communication Requirements; Courtesy of IEC
933 3.1.2. Generation Use Case
935 Energy generation systems are complex infrastructures that require
936 control of both the generated power and the generation
937 infrastructure.
939 3.1.2.1. Control of the Generated Power
941 The electrical power generation frequency must be maintained within a
942 very narrow band. Deviations from the acceptable frequency range are
943 detected and the required signals are sent to the power plants for
944 frequency regulation.
946 Automatic Generation Control (AGC) is a system for adjusting the
947 power output of generators at different power plants, in response to
948 changes in the load.
950 +---------------------------------------------------+---------------+
951 | FCAG (Frequency Control Automatic Generation) | Attribute |
952 | Requirement | |
953 +---------------------------------------------------+---------------+
954 | One way maximum delay | 500 ms |
955 | Asymetric delay Required | No |
956 | Maximum jitter | Not critical |
957 | Topology | Point to |
958 | | point |
959 | Bandwidth | 20 Kbps |
960 | Availability | 99.999 |
961 | precise timing required | Yes |
962 | Recovery time on Node failure | N/A |
963 | performance management | Yes, |
964 | | Mandatory |
965 | Redundancy | Yes |
966 | Packet loss | 1% |
967 +---------------------------------------------------+---------------+
969 Table 9: FCAG Communication Requirements
971 3.1.2.2. Control of the Generation Infrastructure
973 The control of the generation infrastructure combines requirements
974 from industrial automation systems and energy generation systems. In
975 this section we present the use case of the control of the generation
976 infrastructure of a wind turbine.
978 |
979 |
980 | +-----------------+
981 | | +----+ |
982 | | |WTRM| WGEN |
983 WROT x==|===| | |
984 | | +----+ WCNV|
985 | |WNAC |
986 | +---+---WYAW---+--+
987 | | |
988 | | | +----+
989 |WTRF | |WMET|
990 | | | |
991 Wind Turbine | +--+-+
992 Controller | |
993 WTUR | | |
994 WREP | | |
995 WSLG | | |
996 WALG | WTOW | |
998 Figure 1: Wind Turbine Control Network
1000 Figure 1 presents the subsystems that operate a wind turbine. These
1001 subsystems include
1003 o WROT (Rotor Control)
1005 o WNAC (Nacelle Control) (nacelle: housing containing the generator)
1007 o WTRM (Transmission Control)
1009 o WGEN (Generator)
1011 o WYAW (Yaw Controller) (of the tower head)
1013 o WCNV (In-Turbine Power Converter)
1015 o WMET (External Meteorological Station providing real time
1016 information to the controllers of the tower)
1018 Traffic characteristics relevant for the network planning and
1019 dimensioning process in a wind turbine scenario are listed below.
1020 The values in this section are based mainly on the relevant
1021 references [Ahm14] and [Spe09]. Each logical node (Figure 1) is a
1022 part of the metering network and produces analog measurements and
1023 status information which must comply with their respective data rate
1024 constraints.
1026 +-----------+--------+--------+-------------+---------+-------------+
1027 | Subsystem | Sensor | Analog | Data Rate | Status | Data rate |
1028 | | Count | Sample | (bytes/sec) | Sample | (bytes/sec) |
1029 | | | Count | | Count | |
1030 +-----------+--------+--------+-------------+---------+-------------+
1031 | WROT | 14 | 9 | 642 | 5 | 10 |
1032 | WTRM | 18 | 10 | 2828 | 8 | 16 |
1033 | WGEN | 14 | 12 | 73764 | 2 | 4 |
1034 | WCNV | 14 | 12 | 74060 | 2 | 4 |
1035 | WTRF | 12 | 5 | 73740 | 2 | 4 |
1036 | WNAC | 12 | 9 | 112 | 3 | 6 |
1037 | WYAW | 7 | 8 | 220 | 4 | 8 |
1038 | WTOW | 4 | 1 | 8 | 3 | 6 |
1039 | WMET | 7 | 7 | 228 | - | - |
1040 +-----------+--------+--------+-------------+---------+-------------+
1042 Table 10: Wind Turbine Data Rate Constraints
1044 Quality of Service (QoS) constraints for different services are
1045 presented in Table 11. These constraints are defined by IEEE 1646
1046 standard [IEEE1646] and IEC 61400 standard [IEC61400].
1048 +---------------------+---------+-------------+---------------------+
1049 | Service | Latency | Reliability | Packet Loss Rate |
1050 +---------------------+---------+-------------+---------------------+
1051 | Analogue measure | 16 ms | 99.99% | < 10-6 |
1052 | Status information | 16 ms | 99.99% | < 10-6 |
1053 | Protection traffic | 4 ms | 100.00% | < 10-9 |
1054 | Reporting and | 1 s | 99.99% | < 10-6 |
1055 | logging | | | |
1056 | Video surveillance | 1 s | 99.00% | No specific |
1057 | | | | requirement |
1058 | Internet connection | 60 min | 99.00% | No specific |
1059 | | | | requirement |
1060 | Control traffic | 16 ms | 100.00% | < 10-9 |
1061 | Data polling | 16 ms | 99.99% | < 10-6 |
1062 +---------------------+---------+-------------+---------------------+
1064 Table 11: Wind Turbine Reliability and Latency Constraints
1066 3.1.2.2.1. Intra-Domain Network Considerations
1068 A wind turbine is composed of a large set of subsystems including
1069 sensors and actuators which require time-critical operation. The
1070 reliability and latency constraints of these different subsystems is
1071 shown in Table 11. These subsystems are connected to an intra-domain
1072 network which is used to monitor and control the operation of the
1073 turbine and connect it to the SCADA subsystems. The different
1074 components are interconnected using fiber optics, industrial buses,
1075 industrial Ethernet, EtherCat, or a combination of them. Industrial
1076 signaling and control protocols such as Modbus, Profibus, Profinet
1077 and EtherCat are used directly on top of the Layer 2 transport or
1078 encapsulated over TCP/IP.
1080 The Data collected from the sensors and condition monitoring systems
1081 is multiplexed onto fiber cables for transmission to the base of the
1082 tower, and to remote control centers. The turbine controller
1083 continuously monitors the condition of the wind turbine and collects
1084 statistics on its operation. This controller also manages a large
1085 number of switches, hydraulic pumps, valves, and motors within the
1086 wind turbine.
1088 There is usually a controller both at the bottom of the tower and in
1089 the nacelle. The communication between these two controllers usually
1090 takes place using fiber optics instead of copper links. Sometimes, a
1091 third controller is installed in the hub of the rotor and manages the
1092 pitch of the blades. That unit usually communicates with the nacelle
1093 unit using serial communications.
1095 3.1.2.2.2. Inter-Domain network considerations
1097 A remote control center belonging to a grid operator regulates the
1098 power output, enables remote actuation, and monitors the health of
1099 one or more wind parks in tandem. It connects to the local control
1100 center in a wind park over the Internet (Figure 2) via firewalls at
1101 both ends. The AS path between the local control center and the Wind
1102 Park typically involves several ISPs at different tiers. For
1103 example, a remote control center in Denmark can regulate a wind park
1104 in Greece over the normal public AS path between the two locations.
1106 The remote control center is part of the SCADA system, setting the
1107 desired power output to the wind park and reading back the result
1108 once the new power output level has been set. Traffic between the
1109 remote control center and the wind park typically consists of
1110 protocols like IEC 60870-5-104 [IEC-60870-5-104], OPC XML-DA
1111 [OPCXML], Modbus [MODBUS], and SNMP [RFC3411]. Currently, traffic
1112 flows between the wind farm and the remote control center are best
1113 effort. QoS requirements are not strict, so no SLAs or service
1114 provisioning mechanisms (e.g., VPN) are employed. In case of events
1115 like equipment failure, tolerance for alarm delay is on the order of
1116 minutes, due to redundant systems already in place.
1118 +--------------+
1119 | |
1120 | |
1121 | Wind Park #1 +----+
1122 | | | XXXXXX
1123 | | | X XXXXXXXX +----------------+
1124 +--------------+ | XXXX X XXXXX | |
1125 +---+ XXX | Remote Control |
1126 XXX Internet +----+ Center |
1127 +----+X XXX | |
1128 +--------------+ | XXXXXXX XX | |
1129 | | | XX XXXXXXX +----------------+
1130 | | | XXXXX
1131 | Wind Park #2 +----+
1132 | |
1133 | |
1134 +--------------+
1136 Figure 2: Wind Turbine Control via Internet
1138 We expect future use cases which require bounded latency, bounded
1139 jitter and extraordinary low packet loss for inter-domain traffic
1140 flows due to the softwarization and virtualization of core wind farm
1141 equipment (e.g. switches, firewalls and SCADA server components).
1142 These factors will create opportunities for service providers to
1143 install new services and dynamically manage them from remote
1144 locations. For example, to enable fail-over of a local SCADA server,
1145 a SCADA server in another wind farm site (under the administrative
1146 control of the same operator) could be utilized temporarily
1147 (Figure 3). In that case local traffic would be forwarded to the
1148 remote SCADA server and existing intra-domain QoS and timing
1149 parameters would have to be met for inter-domain traffic flows.
1151 +--------------+
1152 | |
1153 | |
1154 | Wind Park #1 +----+
1155 | | | XXXXXX
1156 | | | X XXXXXXXX +----------------+
1157 +--------------+ | XXXX XXXXX | |
1158 +---+ Operator XXX | Remote Control |
1159 XXX Administered +----+ Center |
1160 +----+X WAN XXX | |
1161 +--------------+ | XXXXXXX XX | |
1162 | | | XX XXXXXXX +----------------+
1163 | | | XXXXX
1164 | Wind Park #2 +----+
1165 | |
1166 | |
1167 +--------------+
1169 Figure 3: Wind Turbine Control via Operator Administered WAN
1171 3.1.3. Distribution use case
1173 3.1.3.1. Fault Location Isolation and Service Restoration (FLISR)
1175 Fault Location, Isolation, and Service Restoration (FLISR) refers to
1176 the ability to automatically locate the fault, isolate the fault, and
1177 restore service in the distribution network. This will likely be the
1178 first widespread application of distributed intelligence in the grid.
1180 Static power switch status (open/closed) in the network dictates the
1181 power flow to secondary substations. Reconfiguring the network in
1182 the event of a fault is typically done manually on site to energize/
1183 de-energize alternate paths. Automating the operation of substation
1184 switchgear allows the flow of power to be altered automatically under
1185 fault conditions.
1187 FLISR can be managed centrally from a Distribution Management System
1188 (DMS) or executed locally through distributed control via intelligent
1189 switches and fault sensors.
1191 +----------------------+--------------------------------------------+
1192 | FLISR Requirement | Attribute |
1193 +----------------------+--------------------------------------------+
1194 | One way maximum | 80 ms |
1195 | delay | |
1196 | Asymetric delay | No |
1197 | Required | |
1198 | Maximum jitter | 40 ms |
1199 | Topology | Point to point, point to Multi-point, |
1200 | | Multi-point to Multi-point |
1201 | Bandwidth | 64 Kbps |
1202 | Availability | 99.9999 |
1203 | precise timing | Yes |
1204 | required | |
1205 | Recovery time on | Depends on customer impact |
1206 | Node failure | |
1207 | performance | Yes, Mandatory |
1208 | management | |
1209 | Redundancy | Yes |
1210 | Packet loss | 0.1% |
1211 +----------------------+--------------------------------------------+
1213 Table 12: FLISR Communication Requirements
1215 3.2. Electrical Utilities Today
1217 Many utilities still rely on complex environments formed of multiple
1218 application-specific proprietary networks, including TDM networks.
1220 In this kind of environment there is no mixing of OT and IT
1221 applications on the same network, and information is siloed between
1222 operational areas.
1224 Specific calibration of the full chain is required, which is costly.
1226 This kind of environment prevents utility operations from realizing
1227 the operational efficiency benefits, visibility, and functional
1228 integration of operational information across grid applications and
1229 data networks.
1231 In addition, there are many security-related issues as discussed in
1232 the following section.
1234 3.2.1. Security Current Practices and Limitations
1236 Grid monitoring and control devices are already targets for cyber
1237 attacks, and legacy telecommunications protocols have many intrinsic
1238 network-related vulnerabilities. For example, DNP3, Modbus,
1239 PROFIBUS/PROFINET, and other protocols are designed around a common
1240 paradigm of request and respond. Each protocol is designed for a
1241 master device such as an HMI (Human Machine Interface) system to send
1242 commands to subordinate slave devices to retrieve data (reading
1243 inputs) or control (writing to outputs). Because many of these
1244 protocols lack authentication, encryption, or other basic security
1245 measures, they are prone to network-based attacks, allowing a
1246 malicious actor or attacker to utilize the request-and-respond system
1247 as a mechanism for command-and-control like functionality. Specific
1248 security concerns common to most industrial control, including
1249 utility telecommunication protocols include the following:
1251 o Network or transport errors (e.g. malformed packets or excessive
1252 latency) can cause protocol failure.
1254 o Protocol commands may be available that are capable of forcing
1255 slave devices into inoperable states, including powering-off
1256 devices, forcing them into a listen-only state, disabling
1257 alarming.
1259 o Protocol commands may be available that are capable of restarting
1260 communications and otherwise interrupting processes.
1262 o Protocol commands may be available that are capable of clearing,
1263 erasing, or resetting diagnostic information such as counters and
1264 diagnostic registers.
1266 o Protocol commands may be available that are capable of requesting
1267 sensitive information about the controllers, their configurations,
1268 or other need-to-know information.
1270 o Most protocols are application layer protocols transported over
1271 TCP; therefore it is easy to transport commands over non-standard
1272 ports or inject commands into authorized traffic flows.
1274 o Protocol commands may be available that are capable of
1275 broadcasting messages to many devices at once (i.e. a potential
1276 DoS).
1278 o Protocol commands may be available to query the device network to
1279 obtain defined points and their values (i.e. a configuration
1280 scan).
1282 o Protocol commands may be available that will list all available
1283 function codes (i.e. a function scan).
1285 These inherent vulnerabilities, along with increasing connectivity
1286 between IT an OT networks, make network-based attacks very feasible.
1288 Simple injection of malicious protocol commands provides control over
1289 the target process. Altering legitimate protocol traffic can also
1290 alter information about a process and disrupt the legitimate controls
1291 that are in place over that process. A man-in-the-middle attack
1292 could provide both control over a process and misrepresentation of
1293 data back to operator consoles.
1295 3.3. Electrical Utilities Future
1297 The business and technology trends that are sweeping the utility
1298 industry will drastically transform the utility business from the way
1299 it has been for many decades. At the core of many of these changes
1300 is a drive to modernize the electrical grid with an integrated
1301 telecommunications infrastructure. However, interoperability
1302 concerns, legacy networks, disparate tools, and stringent security
1303 requirements all add complexity to the grid transformation. Given
1304 the range and diversity of the requirements that should be addressed
1305 by the next generation telecommunications infrastructure, utilities
1306 need to adopt a holistic architectural approach to integrate the
1307 electrical grid with digital telecommunications across the entire
1308 power delivery chain.
1310 The key to modernizing grid telecommunications is to provide a
1311 common, adaptable, multi-service network infrastructure for the
1312 entire utility organization. Such a network serves as the platform
1313 for current capabilities while enabling future expansion of the
1314 network to accommodate new applications and services.
1316 To meet this diverse set of requirements, both today and in the
1317 future, the next generation utility telecommunnications network will
1318 be based on open-standards-based IP architecture. An end-to-end IP
1319 architecture takes advantage of nearly three decades of IP technology
1320 development, facilitating interoperability and device management
1321 across disparate networks and devices, as it has been already
1322 demonstrated in many mission-critical and highly secure networks.
1324 IPv6 is seen as a future telecommunications technology for the Smart
1325 Grid; the IEC (International Electrotechnical Commission) and
1326 different National Committees have mandated a specific adhoc group
1327 (AHG8) to define the migration strategy to IPv6 for all the IEC TC57
1328 power automation standards.
1330 We expect cloud-based SCADA systems to control and monitor the
1331 critical and non-critical subsystems of generation systems, for
1332 example wind farms.
1334 3.3.1. Migration to Packet-Switched Network
1336 Throughout the world, utilities are increasingly planning for a
1337 future based on smart grid applications requiring advanced
1338 telecommunications systems. Many of these applications utilize
1339 packet connectivity for communicating information and control signals
1340 across the utility's Wide Area Network (WAN), made possible by
1341 technologies such as multiprotocol label switching (MPLS). The data
1342 that traverses the utility WAN includes:
1344 o Grid monitoring, control, and protection data
1346 o Non-control grid data (e.g. asset data for condition-based
1347 monitoring)
1349 o Physical safety and security data (e.g. voice and video)
1351 o Remote worker access to corporate applications (voice, maps,
1352 schematics, etc.)
1354 o Field area network backhaul for smart metering, and distribution
1355 grid management
1357 o Enterprise traffic (email, collaboration tools, business
1358 applications)
1360 WANs support this wide variety of traffic to and from substations,
1361 the transmission and distribution grid, generation sites, between
1362 control centers, and between work locations and data centers. To
1363 maintain this rapidly expanding set of applications, many utilities
1364 are taking steps to evolve present time-division multiplexing (TDM)
1365 based and frame relay infrastructures to packet systems. Packet-
1366 based networks are designed to provide greater functionalities and
1367 higher levels of service for applications, while continuing to
1368 deliver reliability and deterministic (real-time) traffic support.
1370 3.3.2. Telecommunications Trends
1372 These general telecommunications topics are in addition to the use
1373 cases that have been addressed so far. These include both current
1374 and future telecommunications related topics that should be factored
1375 into the network architecture and design.
1377 3.3.2.1. General Telecommunications Requirements
1379 o IP Connectivity everywhere
1381 o Monitoring services everywhere and from different remote centers
1382 o Move services to a virtual data center
1384 o Unify access to applications / information from the corporate
1385 network
1387 o Unify services
1389 o Unified Communications Solutions
1391 o Mix of fiber and microwave technologies - obsolescence of SONET/
1392 SDH or TDM
1394 o Standardize grid telecommunications protocol to opened standard to
1395 ensure interoperability
1397 o Reliable Telecommunications for Transmission and Distribution
1398 Substations
1400 o IEEE 1588 time synchronization Client / Server Capabilities
1402 o Integration of Multicast Design
1404 o QoS Requirements Mapping
1406 o Enable Future Network Expansion
1408 o Substation Network Resilience
1410 o Fast Convergence Design
1412 o Scalable Headend Design
1414 o Define Service Level Agreements (SLA) and Enable SLA Monitoring
1416 o Integration of 3G/4G Technologies and future technologies
1418 o Ethernet Connectivity for Station Bus Architecture
1420 o Ethernet Connectivity for Process Bus Architecture
1422 o Protection, teleprotection and PMU (Phaser Measurement Unit) on IP
1424 3.3.2.2. Specific Network topologies of Smart Grid Applications
1426 Utilities often have very large private telecommunications networks.
1427 It covers an entire territory / country. The main purpose of the
1428 network, until now, has been to support transmission network
1429 monitoring, control, and automation, remote control of generation
1430 sites, and providing FCAPS (Fault, Configuration, Accounting,
1431 Performance, Security) services from centralized network operation
1432 centers.
1434 Going forward, one network will support operation and maintenance of
1435 electrical networks (generation, transmission, and distribution),
1436 voice and data services for ten of thousands of employees and for
1437 exchange with neighboring interconnections, and administrative
1438 services. To meet those requirements, utility may deploy several
1439 physical networks leveraging different technologies across the
1440 country: an optical network and a microwave network for instance.
1441 Each protection and automatism system between two points has two
1442 telecommunications circuits, one on each network. Path diversity
1443 between two substations is key. Regardless of the event type
1444 (hurricane, ice storm, etc.), one path shall stay available so the
1445 system can still operate.
1447 In the optical network, signals are transmitted over more than tens
1448 of thousands of circuits using fiber optic links, microwave and
1449 telephone cables. This network is the nervous system of the
1450 utility's power transmission operations. The optical network
1451 represents ten of thousands of km of cable deployed along the power
1452 lines, with individual runs as long as 280 km.
1454 3.3.2.3. Precision Time Protocol
1456 Some utilities do not use GPS clocks in generation substations. One
1457 of the main reasons is that some of the generation plants are 30 to
1458 50 meters deep under ground and the GPS signal can be weak and
1459 unreliable. Instead, atomic clocks are used. Clocks are
1460 synchronized amongst each other. Rubidium clocks provide clock and
1461 1ms timestamps for IRIG-B.
1463 Some companies plan to transition to the Precision Time Protocol
1464 (PTP, [IEEE1588]), distributing the synchronization signal over the
1465 IP/MPLS network. PTP provides a mechanism for synchronizing the
1466 clocks of participating nodes to a high degree of accuracy and
1467 precision.
1469 PTP operates based on the following assumptions:
1471 It is assumed that the network eliminates cyclic forwarding of PTP
1472 messages within each communication path (e.g. by using a spanning
1473 tree protocol).
1475 PTP is tolerant of an occasional missed message, duplicated
1476 message, or message that arrived out of order. However, PTP
1477 assumes that such impairments are relatively rare.
1479 PTP was designed assuming a multicast communication model, however
1480 PTP also supports a unicast communication model as long as the
1481 behavior of the protocol is preserved.
1483 Like all message-based time transfer protocols, PTP time accuracy
1484 is degraded by delay asymmetry in the paths taken by event
1485 messages. Asymmetry is not detectable by PTP, however, if such
1486 delays are known a priori, PTP can correct for asymmetry.
1488 IEC 61850 will recommend the use of the IEEE PTP 1588 Utility Profile
1489 (as defined in [IEC62439-3:2012] Annex B) which offers the support of
1490 redundant attachment of clocks to Parallel Redundancy Protcol (PRP)
1491 and High-availability Seamless Redundancy (HSR) networks.
1493 3.3.3. Security Trends in Utility Networks
1495 Although advanced telecommunications networks can assist in
1496 transforming the energy industry by playing a critical role in
1497 maintaining high levels of reliability, performance, and
1498 manageability, they also introduce the need for an integrated
1499 security infrastructure. Many of the technologies being deployed to
1500 support smart grid projects such as smart meters and sensors can
1501 increase the vulnerability of the grid to attack. Top security
1502 concerns for utilities migrating to an intelligent smart grid
1503 telecommunications platform center on the following trends:
1505 o Integration of distributed energy resources
1507 o Proliferation of digital devices to enable management, automation,
1508 protection, and control
1510 o Regulatory mandates to comply with standards for critical
1511 infrastructure protection
1513 o Migration to new systems for outage management, distribution
1514 automation, condition-based maintenance, load forecasting, and
1515 smart metering
1517 o Demand for new levels of customer service and energy management
1519 This development of a diverse set of networks to support the
1520 integration of microgrids, open-access energy competition, and the
1521 use of network-controlled devices is driving the need for a converged
1522 security infrastructure for all participants in the smart grid,
1523 including utilities, energy service providers, large commercial and
1524 industrial, as well as residential customers. Securing the assets of
1525 electric power delivery systems (from the control center to the
1526 substation, to the feeders and down to customer meters) requires an
1527 end-to-end security infrastructure that protects the myriad of
1528 telecommunications assets used to operate, monitor, and control power
1529 flow and measurement.
1531 "Cyber security" refers to all the security issues in automation and
1532 telecommunications that affect any functions related to the operation
1533 of the electric power systems. Specifically, it involves the
1534 concepts of:
1536 o Integrity : data cannot be altered undetectably
1538 o Authenticity : the telecommunications parties involved must be
1539 validated as genuine
1541 o Authorization : only requests and commands from the authorized
1542 users can be accepted by the system
1544 o Confidentiality : data must not be accessible to any
1545 unauthenticated users
1547 When designing and deploying new smart grid devices and
1548 telecommunications systems, it is imperative to understand the
1549 various impacts of these new components under a variety of attack
1550 situations on the power grid. Consequences of a cyber attack on the
1551 grid telecommunications network can be catastrophic. This is why
1552 security for smart grid is not just an ad hoc feature or product,
1553 it's a complete framework integrating both physical and Cyber
1554 security requirements and covering the entire smart grid networks
1555 from generation to distribution. Security has therefore become one
1556 of the main foundations of the utility telecom network architecture
1557 and must be considered at every layer with a defense-in-depth
1558 approach. Migrating to IP based protocols is key to address these
1559 challenges for two reasons:
1561 o IP enables a rich set of features and capabilities to enhance the
1562 security posture
1564 o IP is based on open standards, which allows interoperability
1565 between different vendors and products, driving down the costs
1566 associated with implementing security solutions in OT networks.
1568 Securing OT (Operation technology) telecommunications over packet-
1569 switched IP networks follow the same principles that are foundational
1570 for securing the IT infrastructure, i.e., consideration must be given
1571 to enforcing electronic access control for both person-to-machine and
1572 machine-to-machine communications, and providing the appropriate
1573 levels of data privacy, device and platform integrity, and threat
1574 detection and mitigation.
1576 3.4. Electrical Utilities Asks
1578 o Mixed L2 and L3 topologies
1580 o Deterministic behavior
1582 o Bounded latency and jitter
1584 o Tight feedback intervals
1586 o High availability, low recovery time
1588 o Redundancy, low packet loss
1590 o Precise timing
1592 o Centralized computing of deterministic paths
1594 o Distributed configuration may also be useful
1596 4. Building Automation Systems
1598 4.1. Use Case Description
1600 A Building Automation System (BAS) manages equipment and sensors in a
1601 building for improving residents' comfort, reducing energy
1602 consumption, and responding to failures and emergencies. For
1603 example, the BAS measures the temperature of a room using sensors and
1604 then controls the HVAC (heating, ventilating, and air conditioning)
1605 to maintain a set temperature and minimize energy consumption.
1607 A BAS primarily performs the following functions:
1609 o Periodically measures states of devices, for example humidity and
1610 illuminance of rooms, open/close state of doors, FAN speed, etc.
1612 o Stores the measured data.
1614 o Provides the measured data to BAS systems and operators.
1616 o Generates alarms for abnormal state of devices.
1618 o Controls devices (e.g. turn off room lights at 10:00 PM).
1620 4.2. Building Automation Systems Today
1622 4.2.1. BAS Architecture
1624 A typical BAS architecture of today is shown in Figure 4.
1626 +----------------------------+
1627 | |
1628 | BMS HMI |
1629 | | | |
1630 | +----------------------+ |
1631 | | Management Network | |
1632 | +----------------------+ |
1633 | | | |
1634 | LC LC |
1635 | | | |
1636 | +----------------------+ |
1637 | | Field Network | |
1638 | +----------------------+ |
1639 | | | | | |
1640 | Dev Dev Dev Dev |
1641 | |
1642 +----------------------------+
1644 BMS := Building Management Server
1645 HMI := Human Machine Interface
1646 LC := Local Controller
1648 Figure 4: BAS architecture
1650 There are typically two layers of network in a BAS. The upper one is
1651 called the Management Network and the lower one is called the Field
1652 Network. In management networks an IP-based communication protocol
1653 is used, while in field networks non-IP based communication protocols
1654 ("field protocols") are mainly used. Field networks have specific
1655 timing requirements, whereas management networks can be best-effort.
1657 A Human Machine Interface (HMI) is typically a desktop PC used by
1658 operators to monitor and display device states, send device control
1659 commands to Local Controllers (LCs), and configure building schedules
1660 (for example "turn off all room lights in the building at 10:00 PM").
1662 A Building Management Server (BMS) performs the following operations.
1664 o Collect and store device states from LCs at regular intervals.
1666 o Send control values to LCs according to a building schedule.
1668 o Send an alarm signal to operators if it detects abnormal devices
1669 states.
1671 The BMS and HMI communicate with LCs via IP-based "management
1672 protocols" (see standards [bacnetip], [knx]).
1674 A LC is typically a Programmable Logic Controller (PLC) which is
1675 connected to several tens or hundreds of devices using "field
1676 protocols". An LC performs the following kinds of operations:
1678 o Measure device states and provide the information to BMS or HMI.
1680 o Send control values to devices, unilaterally or as part of a
1681 feedback control loop.
1683 There are many field protocols used today; some are standards-based
1684 and others are proprietary (see standards [lontalk], [modbus],
1685 [profibus] and [flnet]). The result is that BASs have multiple MAC/
1686 PHY modules and interfaces. This makes BASs more expensive, slower
1687 to develop, and can result in "vendor lock-in" with multiple types of
1688 management applications.
1690 4.2.2. BAS Deployment Model
1692 An example BAS for medium or large buildings is shown in Figure 5.
1693 The physical layout spans multiple floors, and there is a monitoring
1694 room where the BAS management entities are located. Each floor will
1695 have one or more LCs depending upon the number of devices connected
1696 to the field network.
1698 +--------------------------------------------------+
1699 | Floor 3 |
1700 | +----LC~~~~+~~~~~+~~~~~+ |
1701 | | | | | |
1702 | | Dev Dev Dev |
1703 | | |
1704 |--- | ------------------------------------------|
1705 | | Floor 2 |
1706 | +----LC~~~~+~~~~~+~~~~~+ Field Network |
1707 | | | | | |
1708 | | Dev Dev Dev |
1709 | | |
1710 |--- | ------------------------------------------|
1711 | | Floor 1 |
1712 | +----LC~~~~+~~~~~+~~~~~+ +-----------------|
1713 | | | | | | Monitoring Room |
1714 | | Dev Dev Dev | |
1715 | | | BMS HMI |
1716 | | Management Network | | | |
1717 | +--------------------------------+-----+ |
1718 | | |
1719 +--------------------------------------------------+
1721 Figure 5: BAS Deployment model for Medium/Large Buildings
1723 Each LC is connected to the monitoring room via the Management
1724 network, and the management functions are performed within the
1725 building. In most cases, fast Ethernet (e.g. 100BASE-T) is used for
1726 the management network. Since the management network is non-
1727 realtime, use of Ethernet without quality of service is sufficient
1728 for today's deployment.
1730 In the field network a variety of physical interfaces such as RS232C
1731 and RS485 are used, which have specific timing requirements. Thus if
1732 a field network is to be replaced with an Ethernet or wireless
1733 network, such networks must support time-critical deterministic
1734 flows.
1736 In Figure 6, another deployment model is presented in which the
1737 management system is hosted remotely. This is becoming popular for
1738 small office and residential buildings in which a standalone
1739 monitoring system is not cost-effective.
1741 +---------------+
1742 | Remote Center |
1743 | |
1744 | BMS HMI |
1745 +------------------------------------+ | | | |
1746 | Floor 2 | | +---+---+ |
1747 | +----LC~~~~+~~~~~+ Field Network| | | |
1748 | | | | | | Router |
1749 | | Dev Dev | +-------|-------+
1750 | | | |
1751 |--- | ------------------------------| |
1752 | | Floor 1 | |
1753 | +----LC~~~~+~~~~~+ | |
1754 | | | | | |
1755 | | Dev Dev | |
1756 | | | |
1757 | | Management Network | WAN |
1758 | +------------------------Router-------------+
1759 | |
1760 +------------------------------------+
1762 Figure 6: Deployment model for Small Buildings
1764 Some interoperability is possible today in the Management Network,
1765 but not in today's field networks due to their non-IP-based design.
1767 4.2.3. Use Cases for Field Networks
1769 Below are use cases for Environmental Monitoring, Fire Detection, and
1770 Feedback Control, and their implications for field network
1771 performance.
1773 4.2.3.1. Environmental Monitoring
1775 The BMS polls each LC at a maximum measurement interval of 100ms (for
1776 example to draw a historical chart of 1 second granularity with a 10x
1777 sampling interval) and then performs the operations as specified by
1778 the operator. Each LC needs to measure each of its several hundred
1779 sensors once per measurement interval. Latency is not critical in
1780 this scenario as long as all sensor values are completed in the
1781 measurement interval. Availability is expected to be 99.999 %.
1783 4.2.3.2. Fire Detection
1785 On detection of a fire, the BMS must stop the HVAC, close the fire
1786 shutters, turn on the fire sprinklers, send an alarm, etc. There are
1787 typically ~10s of sensors per LC that BMS needs to manage. In this
1788 scenario the measurement interval is 10-50ms, the communication delay
1789 is 10ms, and the availability must be 99.9999 %.
1791 4.2.3.3. Feedback Control
1793 BAS systems utilize feedback control in various ways; the most time-
1794 critial is control of DC motors, which require a short feedback
1795 interval (1-5ms) with low communication delay (10ms) and jitter
1796 (1ms). The feedback interval depends on the characteristics of the
1797 device and a target quality of control value. There are typically
1798 ~10s of such devices per LC.
1800 Communication delay is expected to be less than 10 ms, jitter less
1801 than 1 sec while the availability must be 99.9999% .
1803 4.2.4. Security Considerations
1805 When BAS field networks were developed it was assumed that the field
1806 networks would always be physically isolated from external networks
1807 and therefore security was not a concern. In today's world many BASs
1808 are managed remotely and are thus connected to shared IP networks and
1809 so security is definitely a concern, yet security features are not
1810 available in the majority of BAS field network deployments .
1812 The management network, being an IP-based network, has the protocols
1813 available to enable network security, but in practice many BAS
1814 systems do not implement even the available security features such as
1815 device authentication or encryption for data in transit.
1817 4.3. BAS Future
1819 In the future we expect more fine-grained environmental monitoring
1820 and lower energy consumption, which will require more sensors and
1821 devices, thus requiring larger and more complex building networks.
1823 We expect building networks to be connected to or converged with
1824 other networks (Enterprise network, Home network, and Internet).
1826 Therefore better facilities for network management, control,
1827 reliability and security are critical in order to improve resident
1828 and operator convenience and comfort. For example the ability to
1829 monitor and control building devices via the internet would enable
1830 (for example) control of room lights or HVAC from a resident's
1831 desktop PC or phone application.
1833 4.4. BAS Asks
1835 The community would like to see an interoperable protocol
1836 specification that can satisfy the timing, security, availability and
1837 QoS constraints described above, such that the resulting converged
1838 network can replace the disparate field networks. Ideally this
1839 connectivity could extend to the open Internet.
1841 This would imply an architecture that can guarantee
1843 o Low communication delays (from <10ms to 100ms in a network of
1844 several hundred devices)
1846 o Low jitter (< 1 ms)
1848 o Tight feedback intervals (1ms - 10ms)
1850 o High network availability (up to 99.9999% )
1852 o Availability of network data in disaster scenario
1854 o Authentication between management and field devices (both local
1855 and remote)
1857 o Integrity and data origin authentication of communication data
1858 between field and management devices
1860 o Confidentiality of data when communicated to a remote device
1862 5. Wireless for Industrial
1864 5.1. Use Case Description
1866 Wireless networks are useful for industrial applications, for example
1867 when portable, fast-moving or rotating objects are involved, and for
1868 the resource-constrained devices found in the Internet of Things
1869 (IoT).
1871 Such network-connected sensors, actuators, control loops (etc.)
1872 typically require that the underlying network support real-time
1873 quality of service (QoS), as well as specific classes of other
1874 network properties such as reliability, redundancy, and security.
1876 These networks may also contain very large numbers of devices, for
1877 example for factories, "big data" acquisition, and the IoT. Given
1878 the large numbers of devices installed, and the potential
1879 pervasiveness of the IoT, this is a huge and very cost-sensitive
1880 market. For example, a 1% cost reduction in some areas could save
1881 $100B
1883 5.1.1. Network Convergence using 6TiSCH
1885 Some wireless network technologies support real-time QoS, and are
1886 thus useful for these kinds of networks, but others do not. For
1887 example WiFi is pervasive but does not provide guaranteed timing or
1888 delivery of packets, and thus is not useful in this context.
1890 In this use case we focus on one specific wireless network technology
1891 which does provide the required deterministic QoS, which is "IPv6
1892 over the TSCH mode of IEEE 802.15.4e" (6TiSCH, where TSCH stands for
1893 "Time-Slotted Channel Hopping", see [I-D.ietf-6tisch-architecture],
1894 [IEEE802154], [IEEE802154e], and [RFC7554]).
1896 There are other deterministic wireless busses and networks available
1897 today, however they are imcompatible with each other, and
1898 incompatible with IP traffic (for example [ISA100], [WirelessHART]).
1900 Thus the primary goal of this use case is to apply 6TiSH as a
1901 converged IP- and standards-based wireless network for industrial
1902 applications, i.e. to replace multiple proprietary and/or
1903 incompatible wireless networking and wireless network management
1904 standards.
1906 5.1.2. Common Protocol Development for 6TiSCH
1908 Today there are a number of protocols required by 6TiSCH which are
1909 still in development, and a second intent of this use case is to
1910 highlight the ways in which these "missing" protocols share goals in
1911 common with DetNet. Thus it is possible that some of the protocol
1912 technology developed for DetNet will also be applicable to 6TiSCH.
1914 These protocol goals are identified here, along with their
1915 relationship to DetNet. It is likely that ultimately the resulting
1916 protocols will not be identical, but will share design principles
1917 which contribute to the eficiency of enabling both DetNet and 6TiSCH.
1919 One such commonality is that although at a different time scale, in
1920 both TSN [IEEE802.1TSNTG] and TSCH a packet crosses the network from
1921 node to node follows a precise schedule, as a train that leaves
1922 intermediate stations at precise times along its path. This kind of
1923 operation reduces collisions, saves energy, and enables engineering
1924 the network for deterministic properties.
1926 Another commonality is remote monitoring and scheduling management of
1927 a TSCH network by a Path Computation Element (PCE) and Network
1928 Management Entity (NME). The PCE/NME manage timeslots and device
1929 resources in a manner that minimizes the interaction with and the
1930 load placed on resource-constrained devices. For example, a tiny IoT
1931 device may have just enough buffers to store one or a few IPv6
1932 packets, and will have limited bandwidth between peers such that it
1933 can maintain only a small amount of peer information, and will not be
1934 able to store many packets waiting to be forwarded. It is
1935 advantageous then for it to only be required to carry out the
1936 specific behavior assigned to it by the PCE/NME (as opposed to
1937 maintaining its own IP stack, for example).
1939 Note: Current WG discussion indicates that some peer-to-peer
1940 communication must be assumed, i.e. the PCE may communicate only
1941 indirectly with any given device, enabling hierarchical configuration
1942 of the system.
1944 6TiSCH depends on [PCE] and [I-D.finn-detnet-architecture].
1946 6TiSCH also depends on the fact that DetNet will maintain consistency
1947 with [IEEE802.1TSNTG].
1949 5.2. Wireless Industrial Today
1951 Today industrial wireless is accomplished using multiple
1952 deterministic wireless networks which are incompatible with each
1953 other and with IP traffic.
1955 6TiSCH is not yet fully specified, so it cannot be used in today's
1956 applications.
1958 5.3. Wireless Industrial Future
1960 5.3.1. Unified Wireless Network and Management
1962 We expect DetNet and 6TiSCH together to enable converged transport of
1963 deterministic and best-effort traffic flows between real-time
1964 industrial devices and wide area networks via IP routing. A high
1965 level view of a basic such network is shown in Figure 7.
1967 ---+-------- ............ ------------
1968 | External Network |
1969 | +-----+
1970 +-----+ | NME |
1971 | | LLN Border | |
1972 | | router +-----+
1973 +-----+
1974 o o o
1975 o o o o
1976 o o LLN o o o
1977 o o o o
1978 o
1980 Figure 7: Basic 6TiSCH Network
1982 Figure 8 shows a backbone router federating multiple synchronized
1983 6TiSCH subnets into a single subnet connected to the external
1984 network.
1986 ---+-------- ............ ------------
1987 | External Network |
1988 | +-----+
1989 | +-----+ | NME |
1990 +-----+ | +-----+ | |
1991 | | Router | | PCE | +-----+
1992 | | +--| |
1993 +-----+ +-----+
1994 | |
1995 | Subnet Backbone |
1996 +--------------------+------------------+
1997 | | |
1998 +-----+ +-----+ +-----+
1999 | | Backbone | | Backbone | | Backbone
2000 o | | router | | router | | router
2001 +-----+ +-----+ +-----+
2002 o o o o o
2003 o o o o o o o o o o o
2004 o o o LLN o o o o
2005 o o o o o o o o o o o o
2007 Figure 8: Extended 6TiSCH Network
2009 The backbone router must ensure end-to-end deterministic behavior
2010 between the LLN and the backbone. We would like to see this
2011 accomplished in conformance with the work done in
2012 [I-D.finn-detnet-architecture] with respect to Layer-3 aspects of
2013 deterministic networks that span multiple Layer-2 domains.
2015 The PCE must compute a deterministic path end-to-end across the TSCH
2016 network and IEEE802.1 TSN Ethernet backbone, and DetNet protocols are
2017 expected to enable end-to-end deterministic forwarding.
2019 +-----+
2020 | IoT |
2021 | G/W |
2022 +-----+
2023 ^ <---- Elimination
2024 | |
2025 Track branch | |
2026 +-------+ +--------+ Subnet Backbone
2027 | |
2028 +--|--+ +--|--+
2029 | | | Backbone | | | Backbone
2030 o | | | router | | | router
2031 +--/--+ +--|--+
2032 o / o o---o----/ o
2033 o o---o--/ o o o o o
2034 o \ / o o LLN o
2035 o v <---- Replication
2036 o
2038 Figure 9: 6TiSCH Network with PRE
2040 5.3.1.1. PCE and 6TiSCH ARQ Retries
2042 Note: The possible use of ARQ techniques in DetNet is currently
2043 considered a possible design alternative.
2045 6TiSCH uses the IEEE802.15.4 Automatic Repeat-reQuest (ARQ) mechanism
2046 to provide higher reliability of packet delivery. ARQ is related to
2047 packet replication and elimination because there are two independent
2048 paths for packets to arrive at the destination, and if an expected
2049 packed does not arrive on one path then it checks for the packet on
2050 the second path.
2052 Although to date this mechanism is only used by wireless networks,
2053 this may be a technique that would be appropriate for DetNet and so
2054 aspects of the enabling protocol could be co-developed.
2056 For example, in Figure 9, a Track is laid out from a field device in
2057 a 6TiSCH network to an IoT gateway that is located on a IEEE802.1 TSN
2058 backbone.
2060 In ARQ the Replication function in the field device sends a copy of
2061 each packet over two different branches, and the PCE schedules each
2062 hop of both branches so that the two copies arrive in due time at the
2063 gateway. In case of a loss on one branch, hopefully the other copy
2064 of the packet still arrives within the allocated time. If two copies
2065 make it to the IoT gateway, the Elimination function in the gateway
2066 ignores the extra packet and presents only one copy to upper layers.
2068 At each 6TiSCH hop along the Track, the PCE may schedule more than
2069 one timeSlot for a packet, so as to support Layer-2 retries (ARQ).
2071 In current deployments, a TSCH Track does not necessarily support PRE
2072 but is systematically multi-path. This means that a Track is
2073 scheduled so as to ensure that each hop has at least two forwarding
2074 solutions, and the forwarding decision is to try the preferred one
2075 and use the other in case of Layer-2 transmission failure as detected
2076 by ARQ.
2078 5.3.2. Schedule Management by a PCE
2080 A common feature of 6TiSCH and DetNet is the action of a PCE to
2081 configure paths through the network. Specifically, what is needed is
2082 a protocol and data model that the PCE will use to get/set the
2083 relevant configuration from/to the devices, as well as perform
2084 operations on the devices. We expect that this protocol will be
2085 developed by DetNet with consideration for its reuse by 6TiSCH. The
2086 remainder of this section provides a bit more context from the 6TiSCH
2087 side.
2089 5.3.2.1. PCE Commands and 6TiSCH CoAP Requests
2091 The 6TiSCH device does not expect to place the request for bandwidth
2092 between itself and another device in the network. Rather, an
2093 operation control system invoked through a human interface specifies
2094 the required traffic specification and the end nodes (in terms of
2095 latency and reliability). Based on this information, the PCE must
2096 compute a path between the end nodes and provision the network with
2097 per-flow state that describes the per-hop operation for a given
2098 packet, the corresponding timeslots, and the flow identification that
2099 enables recognizing that a certain packet belongs to a certain path,
2100 etc.
2102 For a static configuration that serves a certain purpose for a long
2103 period of time, it is expected that a node will be provisioned in one
2104 shot with a full schedule, which incorporates the aggregation of its
2105 behavior for multiple paths. 6TiSCH expects that the programing of
2106 the schedule will be done over COAP as discussed in
2107 [I-D.ietf-6tisch-coap].
2109 6TiSCH expects that the PCE commands will be mapped back and forth
2110 into CoAP by a gateway function at the edge of the 6TiSCH network.
2111 For instance, it is possible that a mapping entity on the backbone
2112 transforms a non-CoAP protocol such as PCEP into the RESTful
2113 interfaces that the 6TiSCH devices support. This architecture will
2114 be refined to comply with DetNet [I-D.finn-detnet-architecture] when
2115 the work is formalized. Related information about 6TiSCH can be
2116 found at [I-D.ietf-6tisch-6top-interface] and RPL [RFC6550].
2118 A protocol may be used to update the state in the devices during
2119 runtime, for example if it appears that a path through the network
2120 has ceased to perform as expected, but in 6TiSCH that flow was not
2121 designed and no protocol was selected. We would like to see DetNet
2122 define the appropriate end-to-end protocols to be used in that case.
2123 The implication is that these state updates take place once the
2124 system is configured and running, i.e. they are not limited to the
2125 initial communication of the configuration of the system.
2127 A "slotFrame" is the base object that a PCE would manipulate to
2128 program a schedule into an LLN node ([I-D.ietf-6tisch-architecture]).
2130 We would like to see the PCE read energy data from devices, and
2131 compute paths that will implement policies on how energy in devices
2132 is consumed, for instance to ensure that the spent energy does not
2133 exceeded the available energy over a period of time. Note: this
2134 statement implies that an extensible protocol for communicating
2135 device info to the PCE and enabling the PCE to act on it will be part
2136 of the DetNet architecture, however for subnets with specific
2137 protocols (e.g. CoAP) a gateway may be required.
2139 6TiSCH devices can discover their neighbors over the radio using a
2140 mechanism such as beacons, but even though the neighbor information
2141 is available in the 6TiSCH interface data model, 6TiSCH does not
2142 describe a protocol to proactively push the neighborhood information
2143 to a PCE. We would like to see DetNet define such a protocol; one
2144 possible design alternative is that it could operate over CoAP,
2145 alternatively it could be converted to/from CoAP by a gateway. We
2146 would like to see such a protocol carry multiple metrics, for example
2147 similar to those used for RPL operations [RFC6551]
2149 5.3.2.2. 6TiSCH IP Interface
2151 "6top" ([I-D.wang-6tisch-6top-sublayer]) is a logical link control
2152 sitting between the IP layer and the TSCH MAC layer which provides
2153 the link abstraction that is required for IP operations. The 6top
2154 data model and management interfaces are further discussed in
2155 [I-D.ietf-6tisch-6top-interface] and [I-D.ietf-6tisch-coap].
2157 An IP packet that is sent along a 6TiSCH path uses the Differentiated
2158 Services Per-Hop-Behavior Group called Deterministic Forwarding, as
2159 described in [I-D.svshah-tsvwg-deterministic-forwarding].
2161 5.3.3. 6TiSCH Security Considerations
2163 On top of the classical requirements for protection of control
2164 signaling, it must be noted that 6TiSCH networks operate on limited
2165 resources that can be depleted rapidly in a DoS attack on the system,
2166 for instance by placing a rogue device in the network, or by
2167 obtaining management control and setting up unexpected additional
2168 paths.
2170 5.4. Wireless Industrial Asks
2172 6TiSCH depends on DetNet to define:
2174 o Configuration (state) and operations for deterministic paths
2176 o End-to-end protocols for deterministic forwarding (tagging, IP)
2178 o Protocol for packet replication and elimination
2180 6. Cellular Radio
2182 6.1. Use Case Description
2184 This use case describes the application of deterministic networking
2185 in the context of cellular telecom transport networks. Important
2186 elements include time synchronization, clock distribution, and ways
2187 of establishing time-sensitive streams for both Layer-2 and Layer-3
2188 user plane traffic.
2190 6.1.1. Network Architecture
2192 Figure 10 illustrates a typical 3GPP-defined cellular network
2193 architecture, which includes "Fronthaul" and "Midhaul" network
2194 segments. The "Fronthaul" is the network connecting base stations
2195 (baseband processing units) to the remote radio heads (antennas).
2196 The "Midhaul" is the network inter-connecting base stations (or small
2197 cell sites).
2199 In Figure 10 "eNB" ("E-UTRAN Node B") is the hardware that is
2200 connected to the mobile phone network which communicates directly
2201 with mobile handsets ([TS36300]).
2203 Y (remote radio heads (antennas))
2204 \
2205 Y__ \.--. .--. +------+
2206 \_( `. +---+ _(Back`. | 3GPP |
2207 Y------( Front )----|eNB|----( Haul )----| core |
2208 ( ` .Haul ) +---+ ( ` . ) ) | netw |
2209 /`--(___.-' \ `--(___.-' +------+
2210 Y_/ / \.--. \
2211 Y_/ _( Mid`. \
2212 ( Haul ) \
2213 ( ` . ) ) \
2214 `--(___.-'\_____+---+ (small cell sites)
2215 \ |SCe|__Y
2216 +---+ +---+
2217 Y__|eNB|__Y
2218 +---+
2219 Y_/ \_Y ("local" radios)
2221 Figure 10: Generic 3GPP-based Cellular Network Architecture
2223 6.1.2. Delay Constraints
2225 The available processing time for Fronthaul networking overhead is
2226 limited to the available time after the baseband processing of the
2227 radio frame has completed. For example in Long Term Evolution (LTE)
2228 radio, processing of a radio frame is allocated 3ms but typically the
2229 processing uses most of it, allowing only a small fraction to be used
2230 by the Fronthaul network (e.g. up to 250us one-way delay, though the
2231 existing spec ([NGMN-fronth]) supports delay only up to 100us). This
2232 ultimately determines the distance the remote radio heads can be
2233 located from the base stations (e.g., 100us equals roughly 20 km of
2234 optical fiber-based transport). Allocation options of the available
2235 time budget between processing and transport are under heavy
2236 discussions in the mobile industry.
2238 For packet-based transport the allocated transport time (e.g. CPRI
2239 would allow for 100us delay [CPRI]) is consumed by all nodes and
2240 buffering between the remote radio head and the baseband processing
2241 unit, plus the distance-incurred delay.
2243 The baseband processing time and the available "delay budget" for the
2244 fronthaul is likely to change in the forthcoming "5G" due to reduced
2245 radio round trip times and other architectural and service
2246 requirements [NGMN].
2248 [METIS] documents the fundamental challenges as well as overall
2249 technical goals of the future 5G mobile and wireless system as the
2250 starting point. These future systems should support much higher data
2251 volumes and rates and significantly lower end-to-end latency for 100x
2252 more connected devices (at similar cost and energy consumption levels
2253 as today's system).
2255 For Midhaul connections, delay constraints are driven by Inter-Site
2256 radio functions like Coordinated Multipoint Processing (CoMP, see
2257 [CoMP]). CoMP reception and transmission is a framework in which
2258 multiple geographically distributed antenna nodes cooperate to
2259 improve the performance of the users served in the common cooperation
2260 area. The design principal of CoMP is to extend the current single-
2261 cell to multi-UE (User Equipment) transmission to a multi-cell-to-
2262 multi-UEs transmission by base station cooperation.
2264 CoMP has delay-sensitive performance parameters, which are "midhaul
2265 latency" and "CSI (Channel State Information) reporting and
2266 accuracy". The essential feature of CoMP is signaling between eNBs,
2267 so Midhaul latency is the dominating limitation of CoMP performance.
2268 Generally, CoMP can benefit from coordinated scheduling (either
2269 distributed or centralized) of different cells if the signaling delay
2270 between eNBs is within 1-10ms. This delay requirement is both rigid
2271 and absolute because any uncertainty in delay will degrade the
2272 performance significantly.
2274 Inter-site CoMP is one of the key requirements for 5G and is also a
2275 near-term goal for the current 4.5G network architecture.
2277 6.1.3. Time Synchronization Constraints
2279 Fronthaul time synchronization requirements are given by [TS25104],
2280 [TS36104], [TS36211], and [TS36133]. These can be summarized for the
2281 current 3GPP LTE-based networks as:
2283 Delay Accuracy:
2284 +-8ns (i.e. +-1/32 Tc, where Tc is the UMTS Chip time of 1/3.84
2285 MHz) resulting in a round trip accuracy of +-16ns. The value is
2286 this low to meet the 3GPP Timing Alignment Error (TAE) measurement
2287 requirements. Note: performance guarantees of low nanosecond
2288 values such as these are considered to be below the DetNet layer -
2289 it is assumed that the underlying implementation, e.g. the
2290 hardware, will provide sufficient support (e.g. buffering) to
2291 enable this level of accuracy. These values are maintained in the
2292 use case to give an indication of the overall application.
2294 Timing Alignment Error:
2295 Timing Alignment Error (TAE) is problematic to Fronthaul networks
2296 and must be minimized. If the transport network cannot guarantee
2297 low enough TAE then additional buffering has to be introduced at
2298 the edges of the network to buffer out the jitter. Buffering is
2299 not desirable as it reduces the total available delay budget.
2300 Packet Delay Variation (PDV) requirements can be derived from TAE
2301 for packet based Fronthaul networks.
2303 * For multiple input multiple output (MIMO) or TX diversity
2304 transmissions, at each carrier frequency, TAE shall not exceed
2305 65 ns (i.e. 1/4 Tc).
2307 * For intra-band contiguous carrier aggregation, with or without
2308 MIMO or TX diversity, TAE shall not exceed 130 ns (i.e. 1/2
2309 Tc).
2311 * For intra-band non-contiguous carrier aggregation, with or
2312 without MIMO or TX diversity, TAE shall not exceed 260 ns (i.e.
2313 one Tc).
2315 * For inter-band carrier aggregation, with or without MIMO or TX
2316 diversity, TAE shall not exceed 260 ns.
2318 Transport link contribution to radio frequency error:
2319 +-2 PPB. This value is considered to be "available" for the
2320 Fronthaul link out of the total 50 PPB budget reserved for the
2321 radio interface. Note: the reason that the transport link
2322 contributes to radio frequency error is as follows. The current
2323 way of doing Fronthaul is from the radio unit to remote radio head
2324 directly. The remote radio head is essentially a passive device
2325 (without buffering etc.) The transport drives the antenna
2326 directly by feeding it with samples and everything the transport
2327 adds will be introduced to radio as-is. So if the transport
2328 causes additional frequency error that shows immediately on the
2329 radio as well. Note: performance guarantees of low nanosecond
2330 values such as these are considered to be below the DetNet layer -
2331 it is assumed that the underlying implementation, e.g. the
2332 hardware, will provide sufficient support to enable this level of
2333 performance. These values are maintained in the use case to give
2334 an indication of the overall application.
2336 The above listed time synchronization requirements are difficult to
2337 meet with point-to-point connected networks, and more difficult when
2338 the network includes multiple hops. It is expected that networks
2339 must include buffering at the ends of the connections as imposed by
2340 the jitter requirements, since trying to meet the jitter requirements
2341 in every intermediate node is likely to be too costly. However,
2342 every measure to reduce jitter and delay on the path makes it easier
2343 to meet the end-to-end requirements.
2345 In order to meet the timing requirements both senders and receivers
2346 must remain time synchronized, demanding very accurate clock
2347 distribution, for example support for IEEE 1588 transparent clocks or
2348 boundary clocks in every intermediate node.
2350 In cellular networks from the LTE radio era onward, phase
2351 synchronization is needed in addition to frequency synchronization
2352 ([TS36300], [TS23401]).
2354 6.1.4. Transport Loss Constraints
2356 Fronthaul and Midhaul networks assume almost error-free transport.
2357 Errors can result in a reset of the radio interfaces, which can cause
2358 reduced throughput or broken radio connectivity for mobile customers.
2360 For packetized Fronthaul and Midhaul connections packet loss may be
2361 caused by BER, congestion, or network failure scenarios. Current
2362 tools for elminating packet loss for Fronthaul and Midhaul networks
2363 have serious challenges, for example retransmitting lost packets and/
2364 or using forward error correction (FEC) to circumvent bit errors is
2365 practically impossible due to the additional delay incurred. Using
2366 redundant streams for better guarantees for delivery is also
2367 practically impossible in many cases due to high bandwidth
2368 requirements of Fronthaul and Midhaul networks. Protection switching
2369 is also a candidate but current technologies for the path switch are
2370 too slow to avoid reset of mobile interfaces.
2372 Fronthaul links are assumed to be symmetric, and all Fronthaul
2373 streams (i.e. those carrying radio data) have equal priority and
2374 cannot delay or pre-empt each other. This implies that the network
2375 must guarantee that each time-sensitive flow meets their schedule.
2377 6.1.5. Security Considerations
2379 Establishing time-sensitive streams in the network entails reserving
2380 networking resources for long periods of time. It is important that
2381 these reservation requests be authenticated to prevent malicious
2382 reservation attempts from hostile nodes (or accidental
2383 misconfiguration). This is particularly important in the case where
2384 the reservation requests span administrative domains. Furthermore,
2385 the reservation information itself should be digitally signed to
2386 reduce the risk of a legitimate node pushing a stale or hostile
2387 configuration into another networking node.
2389 Note: This is considered important for the security policy of the
2390 network, but does not affect the core DetNet architecture and design.
2392 6.2. Cellular Radio Networks Today
2394 6.2.1. Fronthaul
2396 Today's Fronthaul networks typically consist of:
2398 o Dedicated point-to-point fiber connection is common
2400 o Proprietary protocols and framings
2402 o Custom equipment and no real networking
2404 Current solutions for Fronthaul are direct optical cables or
2405 Wavelength-Division Multiplexing (WDM) connections.
2407 6.2.2. Midhaul and Backhaul
2409 Today's Midhaul and Backhaul networks typically consist of:
2411 o Mostly normal IP networks, MPLS-TP, etc.
2413 o Clock distribution and sync using 1588 and SyncE
2415 Telecommunication networks in the Mid- and Backhaul are already
2416 heading towards transport networks where precise time synchronization
2417 support is one of the basic building blocks. While the transport
2418 networks themselves have practically transitioned to all-IP packet-
2419 based networks to meet the bandwidth and cost requirements, highly
2420 accurate clock distribution has become a challenge.
2422 In the past, Mid- and Backhaul connections were typically based on
2423 Time Division Multiplexing (TDM-based) and provided frequency
2424 synchronization capabilities as a part of the transport media.
2425 Alternatively other technologies such as Global Positioning System
2426 (GPS) or Synchronous Ethernet (SyncE) are used [SyncE].
2428 Both Ethernet and IP/MPLS [RFC3031] (and PseudoWires (PWE) [RFC3985]
2429 for legacy transport support) have become popular tools to build and
2430 manage new all-IP Radio Access Networks (RANs)
2431 [I-D.kh-spring-ip-ran-use-case]. Although various timing and
2432 synchronization optimizations have already been proposed and
2433 implemented including 1588 PTP enhancements
2434 [I-D.ietf-tictoc-1588overmpls] and [I-D.ietf-mpls-residence-time],
2435 these solution are not necessarily sufficient for the forthcoming RAN
2436 architectures nor do they guarantee the more stringent time-
2437 synchronization requirements such as [CPRI].
2439 There are also existing solutions for TDM over IP such as [RFC5087]
2440 and [RFC4553], as well as TDM over Ethernet transports such as
2441 [RFC5086].
2443 6.3. Cellular Radio Networks Future
2445 Future Cellular Radio Networks will be based on a mix of different
2446 xHaul networks (xHaul = front-, mid- and backhaul), and future
2447 transport networks should be able to support all of them
2448 simultaneously. It is already envisioned today that:
2450 o Not all "cellular radio network" traffic will be IP, for example
2451 some will remain at Layer 2 (e.g. Ethernet based). DetNet
2452 solutions must address all traffic types (Layer 2, Layer 3) with
2453 the same tools and allow their transport simultaneously.
2455 o All form of xHaul networks will need some form of DetNet
2456 solutions. For example with the advent of 5G some Backhaul
2457 traffic will also have DetNet requirements (e.g. traffic belonging
2458 to time-critical 5G applications).
2460 We would like to see the following in future Cellular Radio networks:
2462 o Unified standards-based transport protocols and standard
2463 networking equipment that can make use of underlying deterministic
2464 link-layer services
2466 o Unified and standards-based network management systems and
2467 protocols in all parts of the network (including Fronthaul)
2469 New radio access network deployment models and architectures may
2470 require time- sensitive networking services with strict requirements
2471 on other parts of the network that previously were not considered to
2472 be packetized at all. Time and synchronization support are already
2473 topical for Backhaul and Midhaul packet networks [MEF] and are
2474 becoming a real issue for Fronthaul networks also. Specifically in
2475 Fronthaul networks the timing and synchronization requirements can be
2476 extreme for packet based technologies, for example, on the order of
2477 sub +-20 ns packet delay variation (PDV) and frequency accuracy of
2478 +0.002 PPM [Fronthaul].
2480 The actual transport protocols and/or solutions to establish required
2481 transport "circuits" (pinned-down paths) for Fronthaul traffic are
2482 still undefined. Those are likely to include (but are not limited
2483 to) solutions directly over Ethernet, over IP, and using MPLS/
2484 PseudoWire transport.
2486 Even the current time-sensitive networking features may not be
2487 sufficient for Fronthaul traffic. Therefore, having specific
2488 profiles that take the requirements of Fronthaul into account is
2489 desirable [IEEE8021CM].
2491 Interesting and important work for time-sensitive networking has been
2492 done for Ethernet [TSNTG], which specifies the use of IEEE 1588 time
2493 precision protocol (PTP) [IEEE1588] in the context of IEEE 802.1D and
2494 IEEE 802.1Q. [IEEE8021AS] specifies a Layer 2 time synchronizing
2495 service, and other specifications such as IEEE 1722 [IEEE1722]
2496 specify Ethernet-based Layer-2 transport for time-sensitive streams.
2498 New promising work seeks to enable the transport of time-sensitive
2499 fronthaul streams in Ethernet bridged networks [IEEE8021CM].
2500 Analogous to IEEE 1722 there is an ongoing standardization effort to
2501 define the Layer-2 transport encapsulation format for transporting
2502 radio over Ethernet (RoE) in the IEEE 1904.3 Task Force [IEEE19043].
2504 All-IP RANs and xHhaul networks would benefit from time
2505 synchronization and time-sensitive transport services. Although
2506 Ethernet appears to be the unifying technology for the transport,
2507 there is still a disconnect providing Layer 3 services. The protocol
2508 stack typically has a number of layers below the Ethernet Layer 2
2509 that shows up to the Layer 3 IP transport. It is not uncommon that
2510 on top of the lowest layer (optical) transport there is the first
2511 layer of Ethernet followed one or more layers of MPLS, PseudoWires
2512 and/or other tunneling protocols finally carrying the Ethernet layer
2513 visible to the user plane IP traffic.
2515 While there are existing technologies to establish circuits through
2516 the routed and switched networks (especially in MPLS/PWE space),
2517 there is still no way to signal the time synchronization and time-
2518 sensitive stream requirements/reservations for Layer-3 flows in a way
2519 that addresses the entire transport stack, including the Ethernet
2520 layers that need to be configured.
2522 Furthermore, not all "user plane" traffic will be IP. Therefore, the
2523 same solution also must address the use cases where the user plane
2524 traffic is a different layer, for example Ethernet frames.
2526 There is existing work describing the problem statement
2527 [I-D.finn-detnet-problem-statement] and the architecture
2528 [I-D.finn-detnet-architecture] for deterministic networking (DetNet)
2529 that targets solutions for time-sensitive (IP/transport) streams with
2530 deterministic properties over Ethernet-based switched networks.
2532 6.4. Cellular Radio Networks Asks
2534 A standard for data plane transport specification which is:
2536 o Unified among all xHauls (meaning that different flows with
2537 diverse DetNet requirements can coexist in the same network and
2538 traverse the same nodes without interfering with each other)
2540 o Deployed in a highly deterministic network environment
2542 A standard for data flow information models that are:
2544 o Aware of the time sensitivity and constraints of the target
2545 networking environment
2547 o Aware of underlying deterministic networking services (e.g., on
2548 the Ethernet layer)
2550 7. Industrial M2M
2552 7.1. Use Case Description
2554 Industrial Automation in general refers to automation of
2555 manufacturing, quality control and material processing. In this
2556 "machine to machine" (M2M) use case we consider machine units in a
2557 plant floor which periodically exchange data with upstream or
2558 downstream machine modules and/or a supervisory controller within a
2559 local area network.
2561 The actors of M2M communication are Programmable Logic Controllers
2562 (PLCs). Communication between PLCs and between PLCs and the
2563 supervisory PLC (S-PLC) is achieved via critical control/data streams
2564 Figure 11.
2566 S (Sensor)
2567 \ +-----+
2568 PLC__ \.--. .--. ---| MES |
2569 \_( `. _( `./ +-----+
2570 A------( Local )-------------( L2 )
2571 ( Net ) ( Net ) +-------+
2572 /`--(___.-' `--(___.-' ----| S-PLC |
2573 S_/ / PLC .--. / +-------+
2574 A_/ \_( `.
2575 (Actuator) ( Local )
2576 ( Net )
2577 /`--(___.-'\
2578 / \ A
2579 S A
2581 Figure 11: Current Generic Industrial M2M Network Architecture
2583 This use case focuses on PLC-related communications; communication to
2584 Manufacturing-Execution-Systems (MESs) are not addressed.
2586 This use case covers only critical control/data streams; non-critical
2587 traffic between industrial automation applications (such as
2588 communication of state, configuration, set-up, and database
2589 communication) are adequately served by currently available
2590 prioritizing techniques. Such traffic can use up to 80% of the total
2591 bandwidth required. There is also a subset of non-time-critical
2592 traffic that must be reliable even though it is not time sensitive.
2594 In this use case the primary need for deterministic networking is to
2595 provide end-to-end delivery of M2M messages within specific timing
2596 constraints, for example in closed loop automation control. Today
2597 this level of determinism is provided by proprietary networking
2598 technologies. In addition, standard networking technologies are used
2599 to connect the local network to remote industrial automation sites,
2600 e.g. over an enterprise or metro network which also carries other
2601 types of traffic. Therefore, flows that should be forwarded with
2602 deterministic guarantees need to be sustained regardless of the
2603 amount of other flows in those networks.
2605 7.2. Industrial M2M Communication Today
2607 Today, proprietary networks fulfill the needed timing and
2608 availability for M2M networks.
2610 The network topologies used today by industrial automation are
2611 similar to those used by telecom networks: Daisy Chain, Ring, Hub and
2612 Spoke, and Comb (a subset of Daisy Chain).
2614 PLC-related control/data streams are transmitted periodically and
2615 carry either a pre-configured payload or a payload configured during
2616 runtime.
2618 Some industrial applications require time synchronization at the end
2619 nodes. For such time-coordinated PLCs, accuracy of 1 microsecond is
2620 required. Even in the case of "non-time-coordinated" PLCs time sync
2621 may be needed e.g. for timestamping of sensor data.
2623 Industrial network scenarios require advanced security solutions.
2624 Many of the current industrial production networks are physically
2625 separated. Preventing critical flows from be leaked outside a domain
2626 is handled today by filtering policies that are typically enforced in
2627 firewalls.
2629 7.2.1. Transport Parameters
2631 The Cycle Time defines the frequency of message(s) between industrial
2632 actors. The Cycle Time is application dependent, in the range of 1ms
2633 - 100ms for critical control/data streams.
2635 Because industrial applications assume deterministic transport for
2636 critical Control-Data-Stream parameters (instead of defining latency
2637 and delay variation parameters) it is sufficient to fulfill the upper
2638 bound of latency (maximum latency). The underlying networking
2639 infrastructure must ensure a maximum end-to-end delivery time of
2640 messages in the range of 100 microseconds to 50 milliseconds
2641 depending on the control loop application.
2643 The bandwidth requirements of control/data streams are usually
2644 calculated directly from the bytes-per-cycle parameter of the control
2645 loop. For PLC-to-PLC communication one can expect 2 - 32 streams
2646 with packet size in the range of 100 - 700 bytes. For S-PLC to PLCs
2647 the number of streams is higher - up to 256 streams. Usually no more
2648 than 20% of available bandwidth is used for critical control/data
2649 streams. In today's networks 1Gbps links are commonly used.
2651 Most PLC control loops are rather tolerant of packet loss, however
2652 critical control/data streams accept no more than 1 packet loss per
2653 consecutive communication cycle (i.e. if a packet gets lost in cycle
2654 "n", then the next cycle ("n+1") must be lossless). After two or
2655 more consecutive packet losses the network may be considered to be
2656 "down" by the Application.
2658 As network downtime may impact the whole production system the
2659 required network availability is rather high (99,999%).
2661 Based on the above parameters we expect that some form of redundancy
2662 will be required for M2M communications, however any individual
2663 solution depends on several parameters including cycle time, delivery
2664 time, etc.
2666 7.2.2. Stream Creation and Destruction
2668 In an industrial environment, critical control/data streams are
2669 created rather infrequently, on the order of ~10 times per day / week
2670 / month. Most of these critical control/data streams get created at
2671 machine startup, however flexibility is also needed during runtime,
2672 for example when adding or removing a machine. Going forward as
2673 production systems become more flexible, we expect a significant
2674 increase in the rate at which streams are created, changed and
2675 destroyed.
2677 7.3. Industrial M2M Future
2679 We would like to see a converged IP-standards-based network with
2680 deterministic properties that can satisfy the timing, security and
2681 reliability constraints described above. Today's proprietary
2682 networks could then be interfaced to such a network via gateways or,
2683 in the case of new installations, devices could be connected directly
2684 to the converged network.
2686 For this use case we expect time synchronization accuracy on the
2687 order of 1us.
2689 7.4. Industrial M2M Asks
2691 o Converged IP-based network
2693 o Deterministic behavior (bounded latency and jitter )
2695 o High availability (presumably through redundancy) (99.999 %)
2697 o Low message delivery time (100us - 50ms)
2699 o Low packet loss (burstless, 0.1-1 %)
2701 o Security (e.g. prevent critical flows from being leaked between
2702 physically separated networks)
2704 8. Use Case Common Themes
2706 This section summarizes the expected properties of a DetNet network,
2707 based on the use cases as described in this draft.
2709 8.1. Unified, standards-based network
2711 8.1.1. Extensions to Ethernet
2713 A DetNet network is not "a new kind of network" - it based on
2714 extensions to existing Ethernet standards, including elements of IEEE
2715 802.1 AVB/TSN and related standards. Presumably it will be possible
2716 to run DetNet over other underlying transports besides Ethernet, but
2717 Ethernet is explicitly supported.
2719 8.1.2. Centrally Administered
2721 In general a DetNet network is not expected to be "plug and play" -
2722 it is expected that there is some centralized network configuration
2723 and control system. Such a system may be in a single central
2724 location, or it maybe distributed across multiple control entities
2725 that function together as a unified control system for the network.
2726 However, the ability to "hot swap" components (e.g. due to
2727 malfunction) is similar enough to "plug and play" that this kind of
2728 behavior may be expected in DetNet networks, depending on the
2729 implementation.
2731 8.1.3. Standardized Data Flow Information Models
2733 Data Flow Information Models to be used with DetNet networks are to
2734 be specified by DetNet.
2736 8.1.4. L2 and L3 Integration
2738 A DetNet network is intended to integrate between Layer 2 (bridged)
2739 network(s) (e.g. AVB/TSN LAN) and Layer 3 (routed) network(s) (e.g.
2740 using IP-based protocols). One example of this is "making AVB/TSN-
2741 type deterministic performance available from Layer 3 applications,
2742 e.g. using RTP". Another example is "connecting two AVB/TSN LANs
2743 ("islands") together through a standard router".
2745 8.1.5. Guaranteed End-to-End Delivery
2747 Packets sent over DetNet are guaranteed not to be dropped by the
2748 network due to congestion. (Packets may however be dropped for
2749 intended reasons, e.g. per security measures).
2751 8.1.6. Replacement for Multiple Proprietary Deterministic Networks
2753 There are many proprietary non-interoperable deterministic Ethernet-
2754 based networks currently available; DetNet is intended to provide an
2755 open-standards-based alternative to such networks.
2757 8.1.7. Mix of Deterministic and Best-Effort Traffic
2759 DetNet is intended to support coexistance of time-sensitive
2760 operational (OT) traffic and information (IT) traffic on the same
2761 ("unified") network.
2763 8.1.8. Unused Reserved BW to be Available to Best Effort Traffic
2765 If bandwidth reservations are made for a stream but the associated
2766 bandwidth is not used at any point in time, that bandwidth is made
2767 available on the network for best-effort traffic. If the owner of
2768 the reserved stream then starts transmitting again, the bandwidth is
2769 no longer available for best-effort traffic, on a moment-to-moment
2770 basis. Note that such "temporarily available" bandwidth is not
2771 available for time-sensitive traffic, which must have its own
2772 reservation.
2774 8.1.9. Lower Cost, Multi-Vendor Solutions
2776 The DetNet network specifications are intended to enable an ecosystem
2777 in which multiple vendors can create interoperable products, thus
2778 promoting device diversity and potentially higher numbers of each
2779 device manufactured, promoting cost reduction and cost competition
2780 among vendors. The intent is that DetNet networks should be able to
2781 be created at lower cost and with greater diversity of available
2782 devices than existing proprietary networks.
2784 8.2. Scalable Size
2786 DetNet networks range in size from very small, e.g. inside a single
2787 industrial machine, to very large, for example a Utility Grid network
2788 spanning a whole country, and involving many "hops" over various
2789 kinds of links for example radio repeaters, microwave linkes, fiber
2790 optic links, etc.. However recall that the scope of DetNet is
2791 confined to networks that are centrally administered, and explicitly
2792 excludes unbounded decentralized networks such as the Internet.
2794 8.3. Scalable Timing Parameters and Accuracy
2796 8.3.1. Bounded Latency
2798 The DetNet Data Flow Information Model is expected to provide means
2799 to configure the network that include parameters for querying network
2800 path latency, requesting bounded latency for a given stream,
2801 requesting worst case maximum and/or minimum latency for a given path
2802 or stream, and so on. It is an expected case that the network may
2803 not be able to provide a given requested service level, and if so the
2804 network control system should reply that the requested services is
2805 not available (as opposed to accepting the parameter but then not
2806 delivering the desired behavior).
2808 8.3.2. Low Latency
2810 Applications may require "extremely low latency" however depending on
2811 the application these may mean very different latency values; for
2812 example "low latency" across a Utility grid network is on a different
2813 time scale than "low latency" in a motor control loop in a small
2814 machine. The intent is that the mechanisms for specifying desired
2815 latency include wide ranges, and that architecturally there is
2816 nothing to prevent arbirtrarily low latencies from being implemented
2817 in a given network.
2819 8.3.3. Symmetrical Path Delays
2821 Some applications would like to specify that the transit delay time
2822 values be equal for both the transmit and return paths.
2824 8.4. High Reliability and Availability
2826 Reliablity is of critical importance to many DetNet applications, in
2827 which consequences of failure can be extraordinarily high in terms of
2828 cost and even human life. DetNet based systems are expected to be
2829 implemented with essentially arbitrarily high availability (for
2830 example 99.9999% up time, or even 12 nines). The intent is that the
2831 DetNet designs should not make any assumptions about the level of
2832 reliability and availability that may be required of a given system,
2833 and should define parameters for communicating these kinds of metrics
2834 within the network.
2836 A strategy used by DetNet for providing such extraordinarily high
2837 levels of reliability is to provide redundant paths that can be
2838 seamlessly switched between, while maintaining the required
2839 performance of that system.
2841 8.5. Security
2843 Security is of critical importance to many DetNet applications. A
2844 DetNet network must be able to be made secure against devices
2845 failures, attackers, misbehaving devices, and so on. In a DetNet
2846 network the data traffic is expected to be be time-sensitive, thus in
2847 addition to arriving with the data content as intended, the data must
2848 also arrive at the expected time. This may present "new" security
2849 challenges to implementers, and must be addressed accordingly. There
2850 are other security implications, including (but not limited to) the
2851 change in attack surface presented by packet replication and
2852 elimination.
2854 8.6. Deterministic Flows
2856 Reserved bandwidth data flows must be isolated from each other and
2857 from best-effort traffic, so that even if the network is saturated
2858 with best-effort (and/or reserved bandwidth) traffic, the configured
2859 flows are not adversely affected.
2861 9. Use Cases Explicitly Out of Scope for DetNet
2863 This section contains use case text that has been determined to be
2864 outside of the scope of the present DetNet work.
2866 9.1. DetNet Scope Limitations
2868 The scope of DetNet is deliberately limited to specific use cases
2869 that are consistent with the WG charter, subject to the
2870 interpretation of the WG. At the time the DetNet Use Cases were
2871 solicited and provided by the authors the scope of DetNet was not
2872 clearly defined, and as that clarity has emerged, certain of the use
2873 cases have been determined to be outside the scope of the present
2874 DetNet work. Such text has been moved into this section to clarify
2875 that these use cases will not be supported by the DetNet work.
2877 The text in this section was moved here based on the following
2878 "exclusion" principles. Or, as an alternative to moving all such
2879 text to this section, some draft text has been modified in situ to
2880 reflect these same principles.
2882 The following principles have been established to clarify the scope
2883 of the present DetNet work.
2885 o The scope of network addressed by DetNet is limited to networks
2886 that can be centrally controlled, i.e. an "enterprise" aka
2887 "corporate" network. This explicitly excludes "the open
2888 Internet".
2890 o Maintaining synchronized time across a DetNet network is crucial
2891 to its operation, however DetNet assumes that time is to be
2892 maintained using other means, for example (but not limited to)
2893 Precision Time Protocol ([IEEE1588]). A use case may state the
2894 accuracy and reliability that it expects from the DetNet network
2895 as part of a whole system, however it is understood that such
2896 timing properties are not guaranteed by DetNet itself. It is
2897 currently an open question as to whether DetNet protocols will
2898 include a way for an application to communicate such timing
2899 expectations to the network, and if so whether they would be
2900 expected to materially affect the performance they would receive
2901 from the network as a result.
2903 9.2. Internet-based Applications
2905 9.2.1. Use Case Description
2907 There are many applications that communicate across the open Internet
2908 that could benefit from guaranteed delivery and bounded latency. The
2909 following are some representative examples.
2911 9.2.1.1. Media Content Delivery
2913 Media content delivery continues to be an important use of the
2914 Internet, yet users often experience poor quality audio and video due
2915 to the delay and jitter inherent in today's Internet.
2917 9.2.1.2. Online Gaming
2919 Online gaming is a significant part of the gaming market, however
2920 latency can degrade the end user experience. For example "First
2921 Person Shooter" (FPS) games are highly delay-sensitive.
2923 9.2.1.3. Virtual Reality
2925 Virtual reality (VR) has many commercial applications including real
2926 estate presentations, remote medical procedures, and so on. Low
2927 latency is critical to interacting with the virtual world because
2928 perceptual delays can cause motion sickness.
2930 9.2.2. Internet-Based Applications Today
2932 Internet service today is by definition "best effort", with no
2933 guarantees on delivery or bandwidth.
2935 9.2.3. Internet-Based Applications Future
2937 We imagine an Internet from which we will be able to play a video
2938 without glitches and play games without lag.
2940 For online gaming, the maximum round-trip delay can be 100ms and
2941 stricter for FPS gaming which can be 10-50ms. Transport delay is the
2942 dominate part with a 5-20ms budget.
2944 For VR, 1-10ms maximum delay is needed and total network budget is
2945 1-5ms if doing remote VR.
2947 Flow identification can be used for gaming and VR, i.e. it can
2948 recognize a critical flow and provide appropriate latency bounds.
2950 9.2.4. Internet-Based Applications Asks
2952 o Unified control and management protocols to handle time-critical
2953 data flow
2955 o Application-aware flow filtering mechanism to recognize the timing
2956 critical flow without doing 5-tuple matching
2958 o Unified control plane to provide low latency service on Layer-3
2959 without changing the data plane
2961 o OAM system and protocols which can help to provide E2E-delay
2962 sensitive service provisioning
2964 9.3. Pro Audio and Video - Digital Rights Management (DRM)
2966 This section was moved here because this is considered a Link layer
2967 topic, not direct responsibility of DetNet.
2969 Digital Rights Management (DRM) is very important to the audio and
2970 video industries. Any time protected content is introduced into a
2971 network there are DRM concerns that must be maintained (see
2972 [CONTENT_PROTECTION]). Many aspects of DRM are outside the scope of
2973 network technology, however there are cases when a secure link
2974 supporting authentication and encryption is required by content
2975 owners to carry their audio or video content when it is outside their
2976 own secure environment (for example see [DCI]).
2978 As an example, two techniques are Digital Transmission Content
2979 Protection (DTCP) and High-Bandwidth Digital Content Protection
2980 (HDCP). HDCP content is not approved for retransmission within any
2981 other type of DRM, while DTCP may be retransmitted under HDCP.
2982 Therefore if the source of a stream is outside of the network and it
2983 uses HDCP protection it is only allowed to be placed on the network
2984 with that same HDCP protection.
2986 9.4. Pro Audio and Video - Link Aggregation
2988 Note: The term "Link Aggregation" is used here as defined by the text
2989 in the following paragraph, i.e. not following a more common Network
2990 Industry definition. Current WG consensus is that this item won't be
2991 directly supported by the DetNet architecture, for example because it
2992 implies guarantee of in-order delivery of packets which conflicts
2993 with the core goal of achieving the lowest possible latency.
2995 For transmitting streams that require more bandwidth than a single
2996 link in the target network can support, link aggregation is a
2997 technique for combining (aggregating) the bandwidth available on
2998 multiple physical links to create a single logical link of the
2999 required bandwidth. However, if aggregation is to be used, the
3000 network controller (or equivalent) must be able to determine the
3001 maximum latency of any path through the aggregate link.
3003 10. Acknowledgments
3005 10.1. Pro Audio
3007 This section was derived from draft-gunther-detnet-proaudio-req-01.
3009 The editors would like to acknowledge the help of the following
3010 individuals and the companies they represent:
3012 Jeff Koftinoff, Meyer Sound
3014 Jouni Korhonen, Associate Technical Director, Broadcom
3016 Pascal Thubert, CTAO, Cisco
3018 Kieran Tyrrell, Sienda New Media Technologies GmbH
3020 10.2. Utility Telecom
3022 This section was derived from draft-wetterwald-detnet-utilities-reqs-
3023 02.
3025 Faramarz Maghsoodlou, Ph. D. IoT Connected Industries and Energy
3026 Practice Cisco
3028 Pascal Thubert, CTAO Cisco
3030 10.3. Building Automation Systems
3032 This section was derived from draft-bas-usecase-detnet-00.
3034 10.4. Wireless for Industrial
3036 This section was derived from draft-thubert-6tisch-4detnet-01.
3038 This specification derives from the 6TiSCH architecture, which is the
3039 result of multiple interactions, in particular during the 6TiSCH
3040 (bi)Weekly Interim call, relayed through the 6TiSCH mailing list at
3041 the IETF.
3043 The authors wish to thank: Kris Pister, Thomas Watteyne, Xavier
3044 Vilajosana, Qin Wang, Tom Phinney, Robert Assimiti, Michael
3045 Richardson, Zhuo Chen, Malisa Vucinic, Alfredo Grieco, Martin Turon,
3046 Dominique Barthel, Elvis Vogli, Guillaume Gaillard, Herman Storey,
3047 Maria Rita Palattella, Nicola Accettura, Patrick Wetterwald, Pouria
3048 Zand, Raghuram Sudhaakar, and Shitanshu Shah for their participation
3049 and various contributions.
3051 10.5. Cellular Radio
3053 This section was derived from draft-korhonen-detnet-telreq-00.
3055 10.6. Industrial M2M
3057 The authors would like to thank Feng Chen and Marcel Kiessling for
3058 their comments and suggestions.
3060 10.7. Internet Applications and CoMP
3062 This section was derived from draft-zha-detnet-use-case-00.
3064 This document has benefited from reviews, suggestions, comments and
3065 proposed text provided by the following members, listed in
3066 alphabetical order: Jing Huang, Junru Lin, Lehong Niu and Oilver
3067 Huang.
3069 10.8. Electrical Utilities
3071 The wind power generation use case has been extracted from the study
3072 of Wind Farms conducted within the 5GPPP Virtuwind Project. The
3073 project is funded by the European Union's Horizon 2020 research and
3074 innovation programme under grant agreement No 671648 (VirtuWind).
3076 11. Informative References
3078 [ACE] IETF, "Authentication and Authorization for Constrained
3079 Environments", .
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3087 ASHRAE, "Annex J to ANSI/ASHRAE 135-1995 - BACnet/IP",
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3093 [CoMP] NGMN Alliance, "RAN EVOLUTION PROJECT COMP EVALUATION AND
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3095 and_Enhancement_v2.0, March 2015,
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3099 [CONTENT_PROTECTION]
3100 Olsen, D., "1722a Content Protection", 2012,
3101 .
3104 [CPRI] CPRI Cooperation, "Common Public Radio Interface (CPRI);
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3106 2014, .
3109 [CPRI-transp]
3110 CPRI TWG, "CPRI requirements for Ethernet Fronthaul",
3111 November 2015,
3112 .
3115 [DCI] Digital Cinema Initiatives, LLC, "DCI Specification,
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3118 [DICE] IETF, "DTLS In Constrained Environments",
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3122 the Boundaries of Minds and Machines", November 2012.
3124 [ESPN_DC2]
3125 Daley, D., "ESPN's DC2 Scales AVB Large", 2014,
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3133 Chen, D. and T. Mustala, "Ethernet Fronthaul
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3138 [HART] www.hartcomm.org, "Highway Addressable remote Transducer,
3139 a group of specifications for industrial process and
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3143 Finn, N. and P. Thubert, "Deterministic Networking
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3145 progress), August 2016.
3147 [I-D.finn-detnet-problem-statement]
3148 Finn, N. and P. Thubert, "Deterministic Networking Problem
3149 Statement", draft-finn-detnet-problem-statement-05 (work
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3153 Wang, Q. and X. Vilajosana, "6TiSCH Operation Sublayer
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3157 [I-D.ietf-6tisch-architecture]
3158 Thubert, P., "An Architecture for IPv6 over the TSCH mode
3159 of IEEE 802.15.4", draft-ietf-6tisch-architecture-11 (work
3160 in progress), January 2017.
3162 [I-D.ietf-6tisch-coap]
3163 Sudhaakar, R. and P. Zand, "6TiSCH Resource Management and
3164 Interaction using CoAP", draft-ietf-6tisch-coap-03 (work
3165 in progress), March 2015.
3167 [I-D.ietf-6tisch-terminology]
3168 Palattella, M., Thubert, P., Watteyne, T., and Q. Wang,
3169 "Terminology in IPv6 over the TSCH mode of IEEE
3170 802.15.4e", draft-ietf-6tisch-terminology-08 (work in
3171 progress), December 2016.
3173 [I-D.ietf-ipv6-multilink-subnets]
3174 Thaler, D. and C. Huitema, "Multi-link Subnet Support in
3175 IPv6", draft-ietf-ipv6-multilink-subnets-00 (work in
3176 progress), July 2002.
3178 [I-D.ietf-mpls-residence-time]
3179 Mirsky, G., Ruffini, S., Gray, E., Drake, J., Bryant, S.,
3180 and S. Vainshtein, "Residence Time Measurement in MPLS
3181 network", draft-ietf-mpls-residence-time-15 (work in
3182 progress), March 2017.
3184 [I-D.ietf-roll-rpl-industrial-applicability]
3185 Phinney, T., Thubert, P., and R. Assimiti, "RPL
3186 applicability in industrial networks", draft-ietf-roll-
3187 rpl-industrial-applicability-02 (work in progress),
3188 October 2013.
3190 [I-D.ietf-tictoc-1588overmpls]
3191 Davari, S., Oren, A., Bhatia, M., Roberts, P., and L.
3192 Montini, "Transporting Timing messages over MPLS
3193 Networks", draft-ietf-tictoc-1588overmpls-07 (work in
3194 progress), October 2015.
3196 [I-D.kh-spring-ip-ran-use-case]
3197 Khasnabish, B., hu, f., and L. Contreras, "Segment Routing
3198 in IP RAN use case", draft-kh-spring-ip-ran-use-case-02
3199 (work in progress), November 2014.
3201 [I-D.svshah-tsvwg-deterministic-forwarding]
3202 Shah, S. and P. Thubert, "Deterministic Forwarding PHB",
3203 draft-svshah-tsvwg-deterministic-forwarding-04 (work in
3204 progress), August 2015.
3206 [I-D.thubert-6lowpan-backbone-router]
3207 Thubert, P., "6LoWPAN Backbone Router", draft-thubert-
3208 6lowpan-backbone-router-03 (work in progress), February
3209 2013.
3211 [I-D.wang-6tisch-6top-sublayer]
3212 Wang, Q. and X. Vilajosana, "6TiSCH Operation Sublayer
3213 (6top)", draft-wang-6tisch-6top-sublayer-04 (work in
3214 progress), November 2015.
3216 [IEC-60870-5-104]
3217 International Electrotechnical Commission, "International
3218 Standard IEC 60870-5-104: Network access for IEC
3219 60870-5-101 using standard transport profiles", June 2006.
3221 [IEC61400]
3222 "International standard 61400-25: Communications for
3223 monitoring and control of wind power plants", June 2013.
3225 [IEC61850-90-12]
3226 TC57 WG10, IEC., "IEC 61850-90-12 TR: Communication
3227 networks and systems for power utility automation - Part
3228 90-12: Wide area network engineering guidelines", 2015.
3230 [IEC62439-3:2012]
3231 TC65, IEC., "IEC 62439-3: Industrial communication
3232 networks - High availability automation networks - Part 3:
3233 Parallel Redundancy Protocol (PRP) and High-availability
3234 Seamless Redundancy (HSR)", 2012.
3236 [IEEE1588]
3237 IEEE, "IEEE Standard for a Precision Clock Synchronization
3238 Protocol for Networked Measurement and Control Systems",
3239 IEEE Std 1588-2008, 2008,
3240 .
3243 [IEEE1646]
3244 "Communication Delivery Time Performance Requirements for
3245 Electric Power Substation Automation", IEEE Standard
3246 1646-2004 , Apr 2004.
3248 [IEEE1722]
3249 IEEE, "1722-2011 - IEEE Standard for Layer 2 Transport
3250 Protocol for Time Sensitive Applications in a Bridged
3251 Local Area Network", IEEE Std 1722-2011, 2011,
3252 .
3255 [IEEE19043]
3256 IEEE Standards Association, "IEEE 1904.3 TF", IEEE 1904.3,
3257 2015, .
3259 [IEEE802.1TSNTG]
3260 IEEE Standards Association, "IEEE 802.1 Time-Sensitive
3261 Networks Task Group", March 2013,
3262 .
3264 [IEEE802154]
3265 IEEE standard for Information Technology, "IEEE std.
3266 802.15.4, Part. 15.4: Wireless Medium Access Control (MAC)
3267 and Physical Layer (PHY) Specifications for Low-Rate
3268 Wireless Personal Area Networks".
3270 [IEEE802154e]
3271 IEEE standard for Information Technology, "IEEE standard
3272 for Information Technology, IEEE std. 802.15.4, Part.
3273 15.4: Wireless Medium Access Control (MAC) and Physical
3274 Layer (PHY) Specifications for Low-Rate Wireless Personal
3275 Area Networks, June 2011 as amended by IEEE std.
3276 802.15.4e, Part. 15.4: Low-Rate Wireless Personal Area
3277 Networks (LR-WPANs) Amendment 1: MAC sublayer", April
3278 2012.
3280 [IEEE8021AS]
3281 IEEE, "Timing and Synchronizations (IEEE 802.1AS-2011)",
3282 IEEE 802.1AS-2001, 2011,
3283 .
3286 [IEEE8021CM]
3287 Farkas, J., "Time-Sensitive Networking for Fronthaul",
3288 Unapproved PAR, PAR for a New IEEE Standard;
3289 IEEE P802.1CM, April 2015,
3290 .
3293 [IEEE8021TSN]
3294 IEEE 802.1, "The charter of the TG is to provide the
3295 specifications that will allow time-synchronized low
3296 latency streaming services through 802 networks.", 2016,
3297 .
3299 [IETFDetNet]
3300 IETF, "Charter for IETF DetNet Working Group", 2015,
3301 .
3303 [ISA100] ISA/ANSI, "ISA100, Wireless Systems for Automation",
3304 .
3306 [ISA100.11a]
3307 ISA/ANSI, "Wireless Systems for Industrial Automation:
3308 Process Control and Related Applications - ISA100.11a-2011
3309 - IEC 62734", 2011, .
3312 [ISO7240-16]
3313 ISO, "ISO 7240-16:2007 Fire detection and alarm systems --
3314 Part 16: Sound system control and indicating equipment",
3315 2007, .
3318 [knx] KNX Association, "ISO/IEC 14543-3 - KNX", November 2006.
3320 [lontalk] ECHELON, "LonTalk(R) Protocol Specification Version 3.0",
3321 1994.
3323 [LTE-Latency]
3324 Johnston, S., "LTE Latency: How does it compare to other
3325 technologies", March 2014,
3326 .
3329 [MEF] MEF, "Mobile Backhaul Phase 2 Amendment 1 -- Small Cells",
3330 MEF 22.1.1, July 2014,
3331 .
3334 [METIS] METIS, "Scenarios, requirements and KPIs for 5G mobile and
3335 wireless system", ICT-317669-METIS/D1.1 ICT-
3336 317669-METIS/D1.1, April 2013, .
3339 [modbus] Modbus Organization, "MODBUS APPLICATION PROTOCOL
3340 SPECIFICATION V1.1b", December 2006.
3342 [MODBUS] Modbus Organization, Inc., "MODBUS Application Protocol
3343 Specification", Apr 2012.
3345 [net5G] Ericsson, "5G Radio Access, Challenges for 2020 and
3346 Beyond", Ericsson white paper wp-5g, June 2013,
3347 .
3349 [NGMN] NGMN Alliance, "5G White Paper", NGMN 5G White Paper v1.0,
3350 February 2015, .
3353 [NGMN-fronth]
3354 NGMN Alliance, "Fronthaul Requirements for C-RAN", March
3355 2015, .
3358 [OPCXML] OPC Foundation, "OPC XML-Data Access Specification", Dec
3359 2004.
3361 [PCE] IETF, "Path Computation Element",
3362 .
3364 [profibus]
3365 IEC, "IEC 61158 Type 3 - Profibus DP", January 2001.
3367 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
3368 Requirement Levels", BCP 14, RFC 2119,
3369 DOI 10.17487/RFC2119, March 1997,
3370 .
3372 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
3373 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
3374 December 1998, .
3376 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
3377 "Definition of the Differentiated Services Field (DS
3378 Field) in the IPv4 and IPv6 Headers", RFC 2474,
3379 DOI 10.17487/RFC2474, December 1998,
3380 .
3382 [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
3383 Label Switching Architecture", RFC 3031,
3384 DOI 10.17487/RFC3031, January 2001,
3385 .
3387 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
3388 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
3389 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
3390 .
3392 [RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation
3393 Metric for IP Performance Metrics (IPPM)", RFC 3393,
3394 DOI 10.17487/RFC3393, November 2002,
3395 .
3397 [RFC3411] Harrington, D., Presuhn, R., and B. Wijnen, "An
3398 Architecture for Describing Simple Network Management
3399 Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
3400 DOI 10.17487/RFC3411, December 2002,
3401 .
3403 [RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between
3404 Information Models and Data Models", RFC 3444,
3405 DOI 10.17487/RFC3444, January 2003,
3406 .
3408 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
3409 RFC 3972, DOI 10.17487/RFC3972, March 2005,
3410 .
3412 [RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
3413 Edge-to-Edge (PWE3) Architecture", RFC 3985,
3414 DOI 10.17487/RFC3985, March 2005,
3415 .
3417 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
3418 Architecture", RFC 4291, DOI 10.17487/RFC4291, February
3419 2006, .
3421 [RFC4553] Vainshtein, A., Ed. and YJ. Stein, Ed., "Structure-
3422 Agnostic Time Division Multiplexing (TDM) over Packet
3423 (SAToP)", RFC 4553, DOI 10.17487/RFC4553, June 2006,
3424 .
3426 [RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903,
3427 DOI 10.17487/RFC4903, June 2007,
3428 .
3430 [RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6
3431 over Low-Power Wireless Personal Area Networks (6LoWPANs):
3432 Overview, Assumptions, Problem Statement, and Goals",
3433 RFC 4919, DOI 10.17487/RFC4919, August 2007,
3434 .
3436 [RFC5086] Vainshtein, A., Ed., Sasson, I., Metz, E., Frost, T., and
3437 P. Pate, "Structure-Aware Time Division Multiplexed (TDM)
3438 Circuit Emulation Service over Packet Switched Network
3439 (CESoPSN)", RFC 5086, DOI 10.17487/RFC5086, December 2007,
3440 .
3442 [RFC5087] Stein, Y(J)., Shashoua, R., Insler, R., and M. Anavi,
3443 "Time Division Multiplexing over IP (TDMoIP)", RFC 5087,
3444 DOI 10.17487/RFC5087, December 2007,
3445 .
3447 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
3448 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
3449 DOI 10.17487/RFC6282, September 2011,
3450 .
3452 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
3453 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
3454 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
3455 Low-Power and Lossy Networks", RFC 6550,
3456 DOI 10.17487/RFC6550, March 2012,
3457 .
3459 [RFC6551] Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N.,
3460 and D. Barthel, "Routing Metrics Used for Path Calculation
3461 in Low-Power and Lossy Networks", RFC 6551,
3462 DOI 10.17487/RFC6551, March 2012,
3463 .
3465 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
3466 Bormann, "Neighbor Discovery Optimization for IPv6 over
3467 Low-Power Wireless Personal Area Networks (6LoWPANs)",
3468 RFC 6775, DOI 10.17487/RFC6775, November 2012,
3469 .
3471 [RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using
3472 IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the
3473 Internet of Things (IoT): Problem Statement", RFC 7554,
3474 DOI 10.17487/RFC7554, May 2015,
3475 .
3477 [Spe09] Sperotto, A., Sadre, R., Vliet, F., and A. Pras, "A First
3478 Look into SCADA Network Traffic", IP Operations and
3479 Management, p. 518-521. , June 2009.
3481 [SRP_LATENCY]
3482 Gunther, C., "Specifying SRP Latency", 2014,
3483 .
3486 [STUDIO_IP]
3487 Mace, G., "IP Networked Studio Infrastructure for
3488 Synchronized & Real-Time Multimedia Transmissions", 2007,
3489 .
3492 [SyncE] ITU-T, "G.8261 : Timing and synchronization aspects in
3493 packet networks", Recommendation G.8261, August 2013,
3494 .
3496 [TEAS] IETF, "Traffic Engineering Architecture and Signaling",
3497 .
3499 [TS23401] 3GPP, "General Packet Radio Service (GPRS) enhancements
3500 for Evolved Universal Terrestrial Radio Access Network
3501 (E-UTRAN) access", 3GPP TS 23.401 10.10.0, March 2013.
3503 [TS25104] 3GPP, "Base Station (BS) radio transmission and reception
3504 (FDD)", 3GPP TS 25.104 3.14.0, March 2007.
3506 [TS36104] 3GPP, "Evolved Universal Terrestrial Radio Access
3507 (E-UTRA); Base Station (BS) radio transmission and
3508 reception", 3GPP TS 36.104 10.11.0, July 2013.
3510 [TS36133] 3GPP, "Evolved Universal Terrestrial Radio Access
3511 (E-UTRA); Requirements for support of radio resource
3512 management", 3GPP TS 36.133 12.7.0, April 2015.
3514 [TS36211] 3GPP, "Evolved Universal Terrestrial Radio Access
3515 (E-UTRA); Physical channels and modulation", 3GPP
3516 TS 36.211 10.7.0, March 2013.
3518 [TS36300] 3GPP, "Evolved Universal Terrestrial Radio Access (E-UTRA)
3519 and Evolved Universal Terrestrial Radio Access Network
3520 (E-UTRAN); Overall description; Stage 2", 3GPP TS 36.300
3521 10.11.0, September 2013.
3523 [TSNTG] IEEE Standards Association, "IEEE 802.1 Time-Sensitive
3524 Networks Task Group", 2013,
3525 .
3527 [UHD-video]
3528 Holub, P., "Ultra-High Definition Videos and Their
3529 Applications over the Network", The 7th International
3530 Symposium on VICTORIES Project PetrHolub_presentation,
3531 October 2014, .
3534 [WirelessHART]
3535 www.hartcomm.org, "Industrial Communication Networks -
3536 Wireless Communication Network and Communication Profiles
3537 - WirelessHART - IEC 62591", 2010.
3539 Authors' Addresses
3541 Ethan Grossman (editor)
3542 Dolby Laboratories, Inc.
3543 1275 Market Street
3544 San Francisco, CA 94103
3545 USA
3547 Phone: +1 415 645 4726
3548 Email: ethan.grossman@dolby.com
3549 URI: http://www.dolby.com
3551 Craig Gunther
3552 Harman International
3553 10653 South River Front Parkway
3554 South Jordan, UT 84095
3555 USA
3557 Phone: +1 801 568-7675
3558 Email: craig.gunther@harman.com
3559 URI: http://www.harman.com
3560 Pascal Thubert
3561 Cisco Systems, Inc
3562 Building D
3563 45 Allee des Ormes - BP1200
3564 MOUGINS - Sophia Antipolis 06254
3565 FRANCE
3567 Phone: +33 497 23 26 34
3568 Email: pthubert@cisco.com
3570 Patrick Wetterwald
3571 Cisco Systems
3572 45 Allees des Ormes
3573 Mougins 06250
3574 FRANCE
3576 Phone: +33 4 97 23 26 36
3577 Email: pwetterw@cisco.com
3579 Jean Raymond
3580 Hydro-Quebec
3581 1500 University
3582 Montreal H3A3S7
3583 Canada
3585 Phone: +1 514 840 3000
3586 Email: raymond.jean@hydro.qc.ca
3588 Jouni Korhonen
3589 Broadcom Corporation
3590 3151 Zanker Road
3591 San Jose, CA 95134
3592 USA
3594 Email: jouni.nospam@gmail.com
3596 Yu Kaneko
3597 Toshiba
3598 1 Komukai-Toshiba-cho, Saiwai-ku, Kasasaki-shi
3599 Kanagawa, Japan
3601 Email: yu1.kaneko@toshiba.co.jp
3602 Subir Das
3603 Applied Communication Sciences
3604 150 Mount Airy Road, Basking Ridge
3605 New Jersey, 07920, USA
3607 Email: sdas@appcomsci.com
3609 Yiyong Zha
3610 Huawei Technologies
3612 Email: zhayiyong@huawei.com
3614 Balazs Varga
3615 Ericsson
3616 Konyves Kalman krt. 11/B
3617 Budapest 1097
3618 Hungary
3620 Email: balazs.a.varga@ericsson.com
3622 Janos Farkas
3623 Ericsson
3624 Konyves Kalman krt. 11/B
3625 Budapest 1097
3626 Hungary
3628 Email: janos.farkas@ericsson.com
3630 Franz-Josef Goetz
3631 Siemens
3632 Gleiwitzerstr. 555
3633 Nurnberg 90475
3634 Germany
3636 Email: franz-josef.goetz@siemens.com
3638 Juergen Schmitt
3639 Siemens
3640 Gleiwitzerstr. 555
3641 Nurnberg 90475
3642 Germany
3644 Email: juergen.jues.schmitt@siemens.com
3645 Xavier Vilajosana
3646 Worldsensing
3647 483 Arago
3648 Barcelona, Catalonia 08013
3649 Spain
3651 Email: xvilajosana@worldsensing.com
3653 Toktam Mahmoodi
3654 King's College London
3655 Strand, London WC2R 2LS
3656 London, London WC2R 2LS
3657 United Kingdom
3659 Email: toktam.mahmoodi@kcl.ac.uk
3661 Spiros Spirou
3662 Intracom Telecom
3663 19.7 km Markopoulou Ave.
3664 Peania, Attiki 19002
3665 Greece
3667 Email: spis@intracom-telecom.com
3669 Petra Vizarreta
3670 Technical University of Munich, TUM
3671 Maxvorstadt, ArcisstraBe 21
3672 Munich, Germany 80333
3673 Germany
3675 Email: petra.vizarreta@lkn.ei.tum.de