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2 Internet Engineering Task Force E. Grossman, Ed.
3 Internet-Draft DOLBY
4 Intended status: Informational C. Gunther
5 Expires: September 6, 2016 HARMAN
6 P. Thubert
7 P. Wetterwald
8 CISCO
9 J. Raymond
10 HYDRO-QUEBEC
11 J. Korhonen
12 BROADCOM
13 Y. Kaneko
14 Toshiba
15 S. Das
16 Applied Communication Sciences
17 Y. Zha
18 HUAWEI
19 B. Varga
20 J. Farkas
21 Ericsson
22 F. Goetz
23 J. Schmitt
24 Siemens
25 March 5, 2016
27 Deterministic Networking Use Cases
28 draft-ietf-detnet-use-cases-07
30 Abstract
32 This draft documents requirements in several diverse industries to
33 establish multi-hop paths for characterized flows with deterministic
34 properties. In this context deterministic implies that streams can
35 be established which provide guaranteed bandwidth and latency which
36 can be established from either a Layer 2 or Layer 3 (IP) interface,
37 and which can co-exist on an IP network with best-effort traffic.
39 Additional requirements include optional redundant paths, very high
40 reliability paths, time synchronization, and clock distribution.
41 Industries considered include wireless for industrial applications,
42 professional audio, electrical utilities, building automation
43 systems, radio/mobile access networks, automotive, and gaming.
45 For each case, this document will identify the application, identify
46 representative solutions used today, and what new uses an IETF DetNet
47 solution may enable.
49 Status of This Memo
51 This Internet-Draft is submitted in full conformance with the
52 provisions of BCP 78 and BCP 79.
54 Internet-Drafts are working documents of the Internet Engineering
55 Task Force (IETF). Note that other groups may also distribute
56 working documents as Internet-Drafts. The list of current Internet-
57 Drafts is at http://datatracker.ietf.org/drafts/current/.
59 Internet-Drafts are draft documents valid for a maximum of six months
60 and may be updated, replaced, or obsoleted by other documents at any
61 time. It is inappropriate to use Internet-Drafts as reference
62 material or to cite them other than as "work in progress."
64 This Internet-Draft will expire on September 6, 2016.
66 Copyright Notice
68 Copyright (c) 2016 IETF Trust and the persons identified as the
69 document authors. All rights reserved.
71 This document is subject to BCP 78 and the IETF Trust's Legal
72 Provisions Relating to IETF Documents
73 (http://trustee.ietf.org/license-info) in effect on the date of
74 publication of this document. Please review these documents
75 carefully, as they describe your rights and restrictions with respect
76 to this document. Code Components extracted from this document must
77 include Simplified BSD License text as described in Section 4.e of
78 the Trust Legal Provisions and are provided without warranty as
79 described in the Simplified BSD License.
81 Table of Contents
83 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5
84 2. Pro Audio and Video . . . . . . . . . . . . . . . . . . . . . 5
85 2.1. Use Case Description . . . . . . . . . . . . . . . . . . 5
86 2.1.1. Uninterrupted Stream Playback . . . . . . . . . . . . 6
87 2.1.2. Synchronized Stream Playback . . . . . . . . . . . . 7
88 2.1.3. Sound Reinforcement . . . . . . . . . . . . . . . . . 7
89 2.1.4. Deterministic Time to Establish Streaming . . . . . . 8
90 2.1.5. Secure Transmission . . . . . . . . . . . . . . . . . 8
91 2.1.5.1. Safety . . . . . . . . . . . . . . . . . . . . . 8
92 2.1.5.2. Digital Rights Management (DRM) . . . . . . . . . 8
93 2.2. Pro Audio Today . . . . . . . . . . . . . . . . . . . . . 9
94 2.3. Pro Audio Future . . . . . . . . . . . . . . . . . . . . 9
95 2.3.1. Layer 3 Interconnecting Layer 2 Islands . . . . . . . 9
96 2.3.2. High Reliability Stream Paths . . . . . . . . . . . . 9
97 2.3.3. Link Aggregation . . . . . . . . . . . . . . . . . . 10
98 2.3.4. Integration of Reserved Streams into IT Networks . . 10
99 2.3.5. Use of Unused Reservations by Best-Effort Traffic . . 10
100 2.3.6. Traffic Segregation . . . . . . . . . . . . . . . . . 10
101 2.3.6.1. Packet Forwarding Rules, VLANs and Subnets . . . 11
102 2.3.6.2. Multicast Addressing (IPv4 and IPv6) . . . . . . 11
103 2.3.7. Latency Optimization by a Central Controller . . . . 11
104 2.3.8. Reduced Device Cost Due To Reduced Buffer Memory . . 12
105 2.4. Pro Audio Asks . . . . . . . . . . . . . . . . . . . . . 12
106 3. Electrical Utilities . . . . . . . . . . . . . . . . . . . . 12
107 3.1. Use Case Description . . . . . . . . . . . . . . . . . . 12
108 3.1.1. Transmission Use Cases . . . . . . . . . . . . . . . 13
109 3.1.1.1. Protection . . . . . . . . . . . . . . . . . . . 13
110 3.1.1.2. Intra-Substation Process Bus Communications . . . 18
111 3.1.1.3. Wide Area Monitoring and Control Systems . . . . 19
112 3.1.1.4. IEC 61850 WAN engineering guidelines requirement
113 classification . . . . . . . . . . . . . . . . . 20
114 3.1.2. Generation Use Case . . . . . . . . . . . . . . . . . 21
115 3.1.3. Distribution use case . . . . . . . . . . . . . . . . 22
116 3.1.3.1. Fault Location Isolation and Service Restoration
117 (FLISR) . . . . . . . . . . . . . . . . . . . . . 22
118 3.2. Electrical Utilities Today . . . . . . . . . . . . . . . 23
119 3.2.1. Security Current Practices and Limitations . . . . . 23
120 3.3. Electrical Utilities Future . . . . . . . . . . . . . . . 25
121 3.3.1. Migration to Packet-Switched Network . . . . . . . . 25
122 3.3.2. Telecommunications Trends . . . . . . . . . . . . . . 26
123 3.3.2.1. General Telecommunications Requirements . . . . . 26
124 3.3.2.2. Specific Network topologies of Smart Grid
125 Applications . . . . . . . . . . . . . . . . . . 27
126 3.3.2.3. Precision Time Protocol . . . . . . . . . . . . . 28
127 3.3.3. Security Trends in Utility Networks . . . . . . . . . 29
128 3.4. Electrical Utilities Asks . . . . . . . . . . . . . . . . 31
129 4. Building Automation Systems . . . . . . . . . . . . . . . . . 31
130 4.1. Use Case Description . . . . . . . . . . . . . . . . . . 31
131 4.2. Building Automation Systems Today . . . . . . . . . . . . 31
132 4.2.1. BAS Architecture . . . . . . . . . . . . . . . . . . 32
133 4.2.2. BAS Deployment Model . . . . . . . . . . . . . . . . 33
134 4.2.3. Use Cases for Field Networks . . . . . . . . . . . . 35
135 4.2.3.1. Environmental Monitoring . . . . . . . . . . . . 35
136 4.2.3.2. Fire Detection . . . . . . . . . . . . . . . . . 35
137 4.2.3.3. Feedback Control . . . . . . . . . . . . . . . . 36
138 4.2.4. Security Considerations . . . . . . . . . . . . . . . 36
139 4.3. BAS Future . . . . . . . . . . . . . . . . . . . . . . . 36
140 4.4. BAS Asks . . . . . . . . . . . . . . . . . . . . . . . . 37
141 5. Wireless for Industrial . . . . . . . . . . . . . . . . . . . 37
142 5.1. Use Case Description . . . . . . . . . . . . . . . . . . 37
143 5.1.1. Network Convergence using 6TiSCH . . . . . . . . . . 38
144 5.1.2. Common Protocol Development for 6TiSCH . . . . . . . 38
146 5.2. Wireless Industrial Today . . . . . . . . . . . . . . . . 39
147 5.3. Wireless Industrial Future . . . . . . . . . . . . . . . 39
148 5.3.1. Unified Wireless Network and Management . . . . . . . 39
149 5.3.1.1. PCE and 6TiSCH ARQ Retries . . . . . . . . . . . 41
150 5.3.2. Schedule Management by a PCE . . . . . . . . . . . . 42
151 5.3.2.1. PCE Commands and 6TiSCH CoAP Requests . . . . . . 42
152 5.3.2.2. 6TiSCH IP Interface . . . . . . . . . . . . . . . 43
153 5.3.3. 6TiSCH Security Considerations . . . . . . . . . . . 43
154 5.4. Wireless Industrial Asks . . . . . . . . . . . . . . . . 44
155 6. Cellular Radio Use Cases . . . . . . . . . . . . . . . . . . 44
156 6.1. Use Case Description . . . . . . . . . . . . . . . . . . 44
157 6.1.1. Network Architecture . . . . . . . . . . . . . . . . 44
158 6.1.2. Time Synchronization Requirements . . . . . . . . . . 45
159 6.1.3. Time-Sensitive Stream Requirements . . . . . . . . . 47
160 6.1.4. Security Considerations . . . . . . . . . . . . . . . 47
161 6.2. Cellular Radio Networks Today . . . . . . . . . . . . . . 48
162 6.3. Cellular Radio Networks Future . . . . . . . . . . . . . 48
163 6.4. Cellular Radio Networks Asks . . . . . . . . . . . . . . 50
164 7. Cellular Coordinated Multipoint Processing (CoMP) . . . . . . 50
165 7.1. Use Case Description . . . . . . . . . . . . . . . . . . 50
166 7.1.1. CoMP Architecture . . . . . . . . . . . . . . . . . . 51
167 7.1.2. Delay Sensitivity in CoMP . . . . . . . . . . . . . . 52
168 7.2. CoMP Today . . . . . . . . . . . . . . . . . . . . . . . 52
169 7.3. CoMP Future . . . . . . . . . . . . . . . . . . . . . . . 52
170 7.3.1. Mobile Industry Overall Goals . . . . . . . . . . . . 52
171 7.3.2. CoMP Infrastructure Goals . . . . . . . . . . . . . . 53
172 7.4. CoMP Asks . . . . . . . . . . . . . . . . . . . . . . . . 53
173 8. Industrial M2M . . . . . . . . . . . . . . . . . . . . . . . 54
174 8.1. Use Case Description . . . . . . . . . . . . . . . . . . 54
175 8.2. Industrial M2M Communication Today . . . . . . . . . . . 55
176 8.2.1. Transport Parameters . . . . . . . . . . . . . . . . 55
177 8.2.2. Stream Creation and Destruction . . . . . . . . . . . 56
178 8.3. Industrial M2M Future . . . . . . . . . . . . . . . . . . 56
179 8.4. Industrial M2M Asks . . . . . . . . . . . . . . . . . . . 57
180 9. Internet-based Applications . . . . . . . . . . . . . . . . . 57
181 9.1. Use Case Description . . . . . . . . . . . . . . . . . . 57
182 9.1.1. Media Content Delivery . . . . . . . . . . . . . . . 57
183 9.1.2. Online Gaming . . . . . . . . . . . . . . . . . . . . 57
184 9.1.3. Virtual Reality . . . . . . . . . . . . . . . . . . . 57
185 9.2. Internet-Based Applications Today . . . . . . . . . . . . 58
186 9.3. Internet-Based Applications Future . . . . . . . . . . . 58
187 9.4. Internet-Based Applications Asks . . . . . . . . . . . . 58
188 10. Use Case Common Elements . . . . . . . . . . . . . . . . . . 58
189 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 59
190 11.1. Pro Audio . . . . . . . . . . . . . . . . . . . . . . . 59
191 11.2. Utility Telecom . . . . . . . . . . . . . . . . . . . . 60
192 11.3. Building Automation Systems . . . . . . . . . . . . . . 60
193 11.4. Wireless for Industrial . . . . . . . . . . . . . . . . 60
194 11.5. Cellular Radio . . . . . . . . . . . . . . . . . . . . . 60
195 11.6. Industrial M2M . . . . . . . . . . . . . . . . . . . . . 60
196 11.7. Internet Applications and CoMP . . . . . . . . . . . . . 60
197 12. Informative References . . . . . . . . . . . . . . . . . . . 61
198 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 69
200 1. Introduction
202 This draft presents use cases from diverse industries which have in
203 common a need for deterministic streams, but which also differ
204 notably in their network topologies and specific desired behavior.
205 Together, they provide broad industry context for DetNet and a
206 yardstick against which proposed DetNet designs can be measured (to
207 what extent does a proposed design satisfy these various use cases?)
209 For DetNet, use cases explicitly do not define requirements; The
210 DetNet WG will consider the use cases, decide which elements are in
211 scope for DetNet, and the results will be incorporated into future
212 drafts. Similarly, the DetNet use case draft explicitly does not
213 suggest any specific design, architecture or protocols, which will be
214 topics of future drafts.
216 We present for each use case the answers to the following questions:
218 o What is the use case?
220 o How is it addressed today?
222 o How would you like it to be addressed in the future?
224 o What do you want the IETF to deliver?
226 The level of detail in each use case should be sufficient to express
227 the relevant elements of the use case, but not more.
229 At the end we consider the use cases collectively, and examine the
230 most significant goals they have in common.
232 2. Pro Audio and Video
234 2.1. Use Case Description
236 The professional audio and video industry ("ProAV") includes:
238 o Music and film content creation
240 o Broadcast
241 o Cinema
243 o Live sound
245 o Public address, media and emergency systems at large venues
246 (airports, stadiums, churches, theme parks).
248 These industries have already transitioned audio and video signals
249 from analog to digital. However, the digital interconnect systems
250 remain primarily point-to-point with a single (or small number of)
251 signals per link, interconnected with purpose-built hardware.
253 These industries are now transitioning to packet-based infrastructure
254 to reduce cost, increase routing flexibility, and integrate with
255 existing IT infrastructure.
257 Today ProAV applications have no way to establish deterministic
258 streams from a standards-based Layer 3 (IP) interface, which is a
259 fundamental limitation to the use cases described here. Today
260 deterministic streams can be created within standards-based layer 2
261 LANs (e.g. using IEEE 802.1 AVB) however these are not routable via
262 IP and thus are not effective for distribution over wider areas (for
263 example broadcast events that span wide geographical areas).
265 It would be highly desirable if such streams could be routed over the
266 open Internet, however solutions with more limited scope (e.g.
267 enterprise networks) would still provide a substantial improvement.
269 The following sections describe specific ProAV use cases.
271 2.1.1. Uninterrupted Stream Playback
273 Transmitting audio and video streams for live playback is unlike
274 common file transfer because uninterrupted stream playback in the
275 presence of network errors cannot be achieved by re-trying the
276 transmission; by the time the missing or corrupt packet has been
277 identified it is too late to execute a re-try operation. Buffering
278 can be used to provide enough delay to allow time for one or more
279 retries, however this is not an effective solution in applications
280 where large delays (latencies) are not acceptable (as discussed
281 below).
283 Streams with guaranteed bandwidth can eliminate congestion on the
284 network as a cause of transmission errors that would lead to playback
285 interruption. Use of redundant paths can further mitigate
286 transmission errors to provide greater stream reliability.
288 2.1.2. Synchronized Stream Playback
290 Latency in this context is the time between when a signal is
291 initially sent over a stream and when it is received. A common
292 example in ProAV is time-synchronizing audio and video when they take
293 separate paths through the playback system. In this case the latency
294 of both the audio and video streams must be bounded and consistent if
295 the sound is to remain matched to the movement in the video. A
296 common tolerance for audio/video sync is one NTSC video frame (about
297 33ms) and to maintain the audience perception of correct lip sync the
298 latency needs to be consistent within some reasonable tolerance, for
299 example 10%.
301 A common architecture for synchronizing multiple streams that have
302 different paths through the network (and thus potentially different
303 latencies) is to enable measurement of the latency of each path, and
304 have the data sinks (for example speakers) delay (buffer) all packets
305 on all but the slowest path. Each packet of each stream is assigned
306 a presentation time which is based on the longest required delay.
307 This implies that all sinks must maintain a common time reference of
308 sufficient accuracy, which can be achieved by any of various
309 techniques.
311 This type of architecture is commonly implemented using a central
312 controller that determines path delays and arbitrates buffering
313 delays.
315 2.1.3. Sound Reinforcement
317 Consider the latency (delay) from when a person speaks into a
318 microphone to when their voice emerges from the speaker. If this
319 delay is longer than about 10-15 milliseconds it is noticeable and
320 can make a sound reinforcement system unusable (see slide 6 of
321 [SRP_LATENCY]). (If you have ever tried to speak in the presence of
322 a delayed echo of your voice you may know this experience).
324 Note that the 15ms latency bound includes all parts of the signal
325 path, not just the network, so the network latency must be
326 significantly less than 15ms.
328 In some cases local performers must perform in synchrony with a
329 remote broadcast. In such cases the latencies of the broadcast
330 stream and the local performer must be adjusted to match each other,
331 with a worst case of one video frame (33ms for NTSC video).
333 In cases where audio phase is a consideration, for example beam-
334 forming using multiple speakers, latency requirements can be in the
335 10 microsecond range (1 audio sample at 96kHz).
337 2.1.4. Deterministic Time to Establish Streaming
339 Some audio systems installed in public environments (airports,
340 hospitals) have unique requirements with regards to health, safety
341 and fire concerns. One such requirement is a maximum of 3 seconds
342 for a system to respond to an emergency detection and begin sending
343 appropriate warning signals and alarms without human intervention.
344 For this requirement to be met, the system must support a bounded and
345 acceptable time from a notification signal to specific stream
346 establishment. For further details see [ISO7240-16].
348 Similar requirements apply when the system is restarted after a power
349 cycle, cable re-connection, or system reconfiguration.
351 In many cases such re-establishment of streaming state must be
352 achieved by the peer devices themselves, i.e. without a central
353 controller (since such a controller may only be present during
354 initial network configuration).
356 Video systems introduce related requirements, for example when
357 transitioning from one camera feed (video stream) to another (see
358 [STUDIO_IP] and [ESPN_DC2]).
360 2.1.5. Secure Transmission
362 2.1.5.1. Safety
364 Professional audio systems can include amplifiers that are capable of
365 generating hundreds or thousands of watts of audio power which if
366 used incorrectly can cause hearing damage to those in the vicinity.
367 Apart from the usual care required by the systems operators to
368 prevent such incidents, the network traffic that controls these
369 devices must be secured (as with any sensitive application traffic).
371 2.1.5.2. Digital Rights Management (DRM)
373 Digital Rights Management (DRM) is very important to the audio and
374 video industries. Any time protected content is introduced into a
375 network there are DRM concerns that must be maintained (see
376 [CONTENT_PROTECTION]). Many aspects of DRM are outside the scope of
377 network technology, however there are cases when a secure link
378 supporting authentication and encryption is required by content
379 owners to carry their audio or video content when it is outside their
380 own secure environment (for example see [DCI]).
382 As an example, two techniques are Digital Transmission Content
383 Protection (DTCP) and High-Bandwidth Digital Content Protection
384 (HDCP). HDCP content is not approved for retransmission within any
385 other type of DRM, while DTCP may be retransmitted under HDCP.
386 Therefore if the source of a stream is outside of the network and it
387 uses HDCP protection it is only allowed to be placed on the network
388 with that same HDCP protection.
390 2.2. Pro Audio Today
392 Some proprietary systems have been created which enable deterministic
393 streams at Layer 3 however they are "engineered networks" which
394 require careful configuration to operate, often require that the
395 system be over-provisioned, and it is implied that all devices on the
396 network voluntarily play by the rules of that network. To enable
397 these industries to successfully transition to an interoperable
398 multi-vendor packet-based infrastructure requires effective open
399 standards, and we believe that establishing relevant IETF standards
400 is a crucial factor.
402 2.3. Pro Audio Future
404 2.3.1. Layer 3 Interconnecting Layer 2 Islands
406 It would be valuable to enable IP to connect multiple Layer 2 LANs.
408 As an example, ESPN recently constructed a state-of-the-art 194,000
409 sq ft, $125 million broadcast studio called DC2. The DC2 network is
410 capable of handling 46 Tbps of throughput with 60,000 simultaneous
411 signals. Inside the facility are 1,100 miles of fiber feeding four
412 audio control rooms (see [ESPN_DC2] ).
414 In designing DC2 they replaced as much point-to-point technology as
415 they could with packet-based technology. They constructed seven
416 individual studios using layer 2 LANS (using IEEE 802.1 AVB) that
417 were entirely effective at routing audio within the LANs. However to
418 interconnect these layer 2 LAN islands together they ended up using
419 dedicated paths in a custom SDN (Software Defined Networking) router
420 because there is no standards-based routing solution available.
422 2.3.2. High Reliability Stream Paths
424 On-air and other live media streams are often backed up with
425 redundant links that seamlessly act to deliver the content when the
426 primary link fails for any reason. In point-to-point systems this is
427 provided by an additional point-to-point link; the analogous
428 requirement in a packet-based system is to provide an alternate path
429 through the network such that no individual link can bring down the
430 system.
432 2.3.3. Link Aggregation
434 For transmitting streams that require more bandwidth than a single
435 link in the target network can support, link aggregation is a
436 technique for combining (aggregating) the bandwidth available on
437 multiple physical links to create a single logical link of the
438 required bandwidth. However, if aggregation is to be used, the
439 network controller (or equivalent) must be able to determine the
440 maximum latency of any path through the aggregate link.
442 2.3.4. Integration of Reserved Streams into IT Networks
444 A commonly cited goal of moving to a packet based media
445 infrastructure is that costs can be reduced by using off the shelf,
446 commodity network hardware. In addition, economy of scale can be
447 realized by combining media infrastructure with IT infrastructure.
448 In keeping with these goals, stream reservation technology should be
449 compatible with existing protocols, and not compromise use of the
450 network for best effort (non-time-sensitive) traffic.
452 2.3.5. Use of Unused Reservations by Best-Effort Traffic
454 In cases where stream bandwidth is reserved but not currently used
455 (or is under-utilized) that bandwidth must be available to best-
456 effort (i.e. non-time-sensitive) traffic. For example a single
457 stream may be nailed up (reserved) for specific media content that
458 needs to be presented at different times of the day, ensuring timely
459 delivery of that content, yet in between those times the full
460 bandwidth of the network can be utilized for best-effort tasks such
461 as file transfers.
463 This also addresses a concern of IT network administrators that are
464 considering adding reserved bandwidth traffic to their networks that
465 ("users will reserve large quantities of bandwidth and then never un-
466 reserve it even though they are not using it, and soon the network
467 will have no bandwidth left").
469 2.3.6. Traffic Segregation
471 Sink devices may be low cost devices with limited processing power.
472 In order to not overwhelm the CPUs in these devices it is important
473 to limit the amount of traffic that these devices must process.
475 As an example, consider the use of individual seat speakers in a
476 cinema. These speakers are typically required to be cost reduced
477 since the quantities in a single theater can reach hundreds of seats.
478 Discovery protocols alone in a one thousand seat theater can generate
479 enough broadcast traffic to overwhelm a low powered CPU. Thus an
480 installation like this will benefit greatly from some type of traffic
481 segregation that can define groups of seats to reduce traffic within
482 each group. All seats in the theater must still be able to
483 communicate with a central controller.
485 There are many techniques that can be used to support this
486 requirement including (but not limited to) the following examples.
488 2.3.6.1. Packet Forwarding Rules, VLANs and Subnets
490 Packet forwarding rules can be used to eliminate some extraneous
491 streaming traffic from reaching potentially low powered sink devices,
492 however there may be other types of broadcast traffic that should be
493 eliminated using other means for example VLANs or IP subnets.
495 2.3.6.2. Multicast Addressing (IPv4 and IPv6)
497 Multicast addressing is commonly used to keep bandwidth utilization
498 of shared links to a minimum.
500 Because of the MAC Address forwarding nature of Layer 2 bridges it is
501 important that a multicast MAC address is only associated with one
502 stream. This will prevent reservations from forwarding packets from
503 one stream down a path that has no interested sinks simply because
504 there is another stream on that same path that shares the same
505 multicast MAC address.
507 Since each multicast MAC Address can represent 32 different IPv4
508 multicast addresses there must be a process put in place to make sure
509 this does not occur. Requiring use of IPv6 address can achieve this,
510 however due to their continued prevalence, solutions that are
511 effective for IPv4 installations are also required.
513 2.3.7. Latency Optimization by a Central Controller
515 A central network controller might also perform optimizations based
516 on the individual path delays, for example sinks that are closer to
517 the source can inform the controller that they can accept greater
518 latency since they will be buffering packets to match presentation
519 times of farther away sinks. The controller might then move a stream
520 reservation on a short path to a longer path in order to free up
521 bandwidth for other critical streams on that short path. See slides
522 3-5 of [SRP_LATENCY].
524 Additional optimization can be achieved in cases where sinks have
525 differing latency requirements, for example in a live outdoor concert
526 the speaker sinks have stricter latency requirements than the
527 recording hardware sinks. See slide 7 of [SRP_LATENCY].
529 2.3.8. Reduced Device Cost Due To Reduced Buffer Memory
531 Device cost can be reduced in a system with guaranteed reservations
532 with a small bounded latency due to the reduced requirements for
533 buffering (i.e. memory) on sink devices. For example, a theme park
534 might broadcast a live event across the globe via a layer 3 protocol;
535 in such cases the size of the buffers required is proportional to the
536 latency bounds and jitter caused by delivery, which depends on the
537 worst case segment of the end-to-end network path. For example on
538 todays open internet the latency is typically unacceptable for audio
539 and video streaming without many seconds of buffering. In such
540 scenarios a single gateway device at the local network that receives
541 the feed from the remote site would provide the expensive buffering
542 required to mask the latency and jitter issues associated with long
543 distance delivery. Sink devices in the local location would have no
544 additional buffering requirements, and thus no additional costs,
545 beyond those required for delivery of local content. The sink device
546 would be receiving the identical packets as those sent by the source
547 and would be unaware that there were any latency or jitter issues
548 along the path.
550 2.4. Pro Audio Asks
552 o Layer 3 routing on top of AVB (and/or other high QoS networks)
554 o Content delivery with bounded, lowest possible latency
556 o IntServ and DiffServ integration with AVB (where practical)
558 o Single network for A/V and IT traffic
560 o Standards-based, interoperable, multi-vendor
562 o IT department friendly
564 o Enterprise-wide networks (e.g. size of San Francisco but not the
565 whole Internet (yet...))
567 3. Electrical Utilities
569 3.1. Use Case Description
571 Many systems that an electrical utility deploys today rely on high
572 availability and deterministic behavior of the underlying networks.
573 Here we present use cases in Transmission, Generation and
574 Distribution, including key timing and reliability metrics. We also
575 discuss security issues and industry trends which affect the
576 architecture of next generation utility networks
578 3.1.1. Transmission Use Cases
580 3.1.1.1. Protection
582 Protection means not only the protection of human operators but also
583 the protection of the electrical equipment and the preservation of
584 the stability and frequency of the grid. If a fault occurs in the
585 transmission or distribution of electricity then severe damage can
586 occur to human operators, electrical equipment and the grid itself,
587 leading to blackouts.
589 Communication links in conjunction with protection relays are used to
590 selectively isolate faults on high voltage lines, transformers,
591 reactors and other important electrical equipment. The role of the
592 teleprotection system is to selectively disconnect a faulty part by
593 transferring command signals within the shortest possible time.
595 3.1.1.1.1. Key Criteria
597 The key criteria for measuring teleprotection performance are command
598 transmission time, dependability and security. These criteria are
599 defined by the IEC standard 60834 as follows:
601 o Transmission time (Speed): The time between the moment where state
602 changes at the transmitter input and the moment of the
603 corresponding change at the receiver output, including propagation
604 delay. Overall operating time for a teleprotection system
605 includes the time for initiating the command at the transmitting
606 end, the propagation delay over the network (including equipments)
607 and the selection and decision time at the receiving end,
608 including any additional delay due to a noisy environment.
610 o Dependability: The ability to issue and receive valid commands in
611 the presence of interference and/or noise, by minimizing the
612 probability of missing command (PMC). Dependability targets are
613 typically set for a specific bit error rate (BER) level.
615 o Security: The ability to prevent false tripping due to a noisy
616 environment, by minimizing the probability of unwanted commands
617 (PUC). Security targets are also set for a specific bit error
618 rate (BER) level.
620 Additional elements of the the teleprotection system that impact its
621 performance include:
623 o Network bandwidth
625 o Failure recovery capacity (aka resiliency)
627 3.1.1.1.2. Fault Detection and Clearance Timing
629 Most power line equipment can tolerate short circuits or faults for
630 up to approximately five power cycles before sustaining irreversible
631 damage or affecting other segments in the network. This translates
632 to total fault clearance time of 100ms. As a safety precaution,
633 however, actual operation time of protection systems is limited to
634 70- 80 percent of this period, including fault recognition time,
635 command transmission time and line breaker switching time.
637 Some system components, such as large electromechanical switches,
638 require particularly long time to operate and take up the majority of
639 the total clearance time, leaving only a 10ms window for the
640 telecommunications part of the protection scheme, independent of the
641 distance to travel. Given the sensitivity of the issue, new networks
642 impose requirements that are even more stringent: IEC standard 61850
643 limits the transfer time for protection messages to 1/4 - 1/2 cycle
644 or 4 - 8ms (for 60Hz lines) for the most critical messages.
646 3.1.1.1.3. Symmetric Channel Delay
648 Teleprotection channels which are differential must be synchronous,
649 which means that any delays on the transmit and receive paths must
650 match each other. Teleprotection systems ideally support zero
651 asymmetric delay; typical legacy relays can tolerate delay
652 discrepancies of up to 750us.
654 Some tools available for lowering delay variation below this
655 threshold are:
657 o For legacy systems using Time Division Multiplexing (TDM), jitter
658 buffers at the multiplexers on each end of the line can be used to
659 offset delay variation by queuing sent and received packets. The
660 length of the queues must balance the need to regulate the rate of
661 transmission with the need to limit overall delay, as larger
662 buffers result in increased latency.
664 o For jitter-prone IP packet networks, traffic management tools can
665 ensure that the teleprotection signals receive the highest
666 transmission priority to minimize jitter.
668 o Standard packet-based synchronization technologies, such as
669 1588-2008 Precision Time Protocol (PTP) and Synchronous Ethernet
670 (Sync-E), can help keep networks stable by maintaining a highly
671 accurate clock source on the various network devices.
673 3.1.1.1.4. Teleprotection Network Requirements (IEC 61850)
675 The following table captures the main network metrics as based on the
676 IEC 61850 standard.
678 +-----------------------------+-------------------------------------+
679 | Teleprotection Requirement | Attribute |
680 +-----------------------------+-------------------------------------+
681 | One way maximum delay | 4-10 ms |
682 | Asymetric delay required | Yes |
683 | Maximum jitter | less than 250 us (750 us for legacy |
684 | | IED) |
685 | Topology | Point to point, point to Multi- |
686 | | point |
687 | Availability | 99.9999 |
688 | precise timing required | Yes |
689 | Recovery time on node | less than 50ms - hitless |
690 | failure | |
691 | performance management | Yes, Mandatory |
692 | Redundancy | Yes |
693 | Packet loss | 0.1% to 1% |
694 +-----------------------------+-------------------------------------+
696 Table 1: Teleprotection network requirements
698 3.1.1.1.5. Inter-Trip Protection scheme
700 "Inter-tripping" is the signal-controlled tripping of a circuit
701 breaker to complete the isolation of a circuit or piece of apparatus
702 in concert with the tripping of other circuit breakers.
704 +--------------------------------+----------------------------------+
705 | Inter-Trip protection | Attribute |
706 | Requirement | |
707 +--------------------------------+----------------------------------+
708 | One way maximum delay | 5 ms |
709 | Asymetric delay required | No |
710 | Maximum jitter | Not critical |
711 | Topology | Point to point, point to Multi- |
712 | | point |
713 | Bandwidth | 64 Kbps |
714 | Availability | 99.9999 |
715 | precise timing required | Yes |
716 | Recovery time on node failure | less than 50ms - hitless |
717 | performance management | Yes, Mandatory |
718 | Redundancy | Yes |
719 | Packet loss | 0.1% |
720 +--------------------------------+----------------------------------+
722 Table 2: Inter-Trip protection network requirements
724 3.1.1.1.6. Current Differential Protection Scheme
726 Current differential protection is commonly used for line protection,
727 and is typical for protecting parallel circuits. At both end of the
728 lines the current is measured by the differential relays, and both
729 relays will trip the circuit breaker if the current going into the
730 line does not equal the current going out of the line. This type of
731 protection scheme assumes some form of communications being present
732 between the relays at both end of the line, to allow both relays to
733 compare measured current values. Line differential protection
734 schemes assume a very low telecommunications delay between both
735 relays, often as low as 5ms. Moreover, as those systems are often
736 not time-synchronized, they also assume symmetric telecommunications
737 paths with constant delay, which allows comparing current measurement
738 values taken at the exact same time.
740 +----------------------------------+--------------------------------+
741 | Current Differential protection | Attribute |
742 | Requirement | |
743 +----------------------------------+--------------------------------+
744 | One way maximum delay | 5 ms |
745 | Asymetric delay Required | Yes |
746 | Maximum jitter | less than 250 us (750us for |
747 | | legacy IED) |
748 | Topology | Point to point, point to |
749 | | Multi-point |
750 | Bandwidth | 64 Kbps |
751 | Availability | 99.9999 |
752 | precise timing required | Yes |
753 | Recovery time on node failure | less than 50ms - hitless |
754 | performance management | Yes, Mandatory |
755 | Redundancy | Yes |
756 | Packet loss | 0.1% |
757 +----------------------------------+--------------------------------+
759 Table 3: Current Differential Protection metrics
761 3.1.1.1.7. Distance Protection Scheme
763 Distance (Impedance Relay) protection scheme is based on voltage and
764 current measurements. The network metrics are similar (but not
765 identical to) Current Differential protection.
767 +-------------------------------+-----------------------------------+
768 | Distance protection | Attribute |
769 | Requirement | |
770 +-------------------------------+-----------------------------------+
771 | One way maximum delay | 5 ms |
772 | Asymetric delay Required | No |
773 | Maximum jitter | Not critical |
774 | Topology | Point to point, point to Multi- |
775 | | point |
776 | Bandwidth | 64 Kbps |
777 | Availability | 99.9999 |
778 | precise timing required | Yes |
779 | Recovery time on node failure | less than 50ms - hitless |
780 | performance management | Yes, Mandatory |
781 | Redundancy | Yes |
782 | Packet loss | 0.1% |
783 +-------------------------------+-----------------------------------+
785 Table 4: Distance Protection requirements
787 3.1.1.1.8. Inter-Substation Protection Signaling
789 This use case describes the exchange of Sampled Value and/or GOOSE
790 (Generic Object Oriented Substation Events) message between
791 Intelligent Electronic Devices (IED) in two substations for
792 protection and tripping coordination. The two IEDs are in a master-
793 slave mode.
795 The Current Transformer or Voltage Transformer (CT/VT) in one
796 substation sends the sampled analog voltage or current value to the
797 Merging Unit (MU) over hard wire. The MU sends the time-synchronized
798 61850-9-2 sampled values to the slave IED. The slave IED forwards
799 the information to the Master IED in the other substation. The
800 master IED makes the determination (for example based on sampled
801 value differentials) to send a trip command to the originating IED.
802 Once the slave IED/Relay receives the GOOSE trip for breaker
803 tripping, it opens the breaker. It then sends a confirmation message
804 back to the master. All data exchanges between IEDs are either
805 through Sampled Value and/or GOOSE messages.
807 +----------------------------------+--------------------------------+
808 | Inter-Substation protection | Attribute |
809 | Requirement | |
810 +----------------------------------+--------------------------------+
811 | One way maximum delay | 5 ms |
812 | Asymetric delay Required | No |
813 | Maximum jitter | Not critical |
814 | Topology | Point to point, point to |
815 | | Multi-point |
816 | Bandwidth | 64 Kbps |
817 | Availability | 99.9999 |
818 | precise timing required | Yes |
819 | Recovery time on node failure | less than 50ms - hitless |
820 | performance management | Yes, Mandatory |
821 | Redundancy | Yes |
822 | Packet loss | 1% |
823 +----------------------------------+--------------------------------+
825 Table 5: Inter-Substation Protection requirements
827 3.1.1.2. Intra-Substation Process Bus Communications
829 This use case describes the data flow from the CT/VT to the IEDs in
830 the substation via the MU. The CT/VT in the substation send the
831 sampled value (analog voltage or current) to the MU over hard wire.
832 The MU sends the time-synchronized 61850-9-2 sampled values to the
833 IEDs in the substation in GOOSE message format. The GPS Master Clock
834 can send 1PPS or IRIG-B format to the MU through a serial port or
835 IEEE 1588 protocol via a network. Process bus communication using
836 61850 simplifies connectivity within the substation and removes the
837 requirement for multiple serial connections and removes the slow
838 serial bus architectures that are typically used. This also ensures
839 increased flexibility and increased speed with the use of multicast
840 messaging between multiple devices.
842 +----------------------------------+--------------------------------+
843 | Intra-Substation protection | Attribute |
844 | Requirement | |
845 +----------------------------------+--------------------------------+
846 | One way maximum delay | 5 ms |
847 | Asymetric delay Required | No |
848 | Maximum jitter | Not critical |
849 | Topology | Point to point, point to |
850 | | Multi-point |
851 | Bandwidth | 64 Kbps |
852 | Availability | 99.9999 |
853 | precise timing required | Yes |
854 | Recovery time on Node failure | less than 50ms - hitless |
855 | performance management | Yes, Mandatory |
856 | Redundancy | Yes - No |
857 | Packet loss | 0.1% |
858 +----------------------------------+--------------------------------+
860 Table 6: Intra-Substation Protection requirements
862 3.1.1.3. Wide Area Monitoring and Control Systems
864 The application of synchrophasor measurement data from Phasor
865 Measurement Units (PMU) to Wide Area Monitoring and Control Systems
866 promises to provide important new capabilities for improving system
867 stability. Access to PMU data enables more timely situational
868 awareness over larger portions of the grid than what has been
869 possible historically with normal SCADA (Supervisory Control and Data
870 Acquisition) data. Handling the volume and real-time nature of
871 synchrophasor data presents unique challenges for existing
872 application architectures. Wide Area management System (WAMS) makes
873 it possible for the condition of the bulk power system to be observed
874 and understood in real-time so that protective, preventative, or
875 corrective action can be taken. Because of the very high sampling
876 rate of measurements and the strict requirement for time
877 synchronization of the samples, WAMS has stringent telecommunications
878 requirements in an IP network that are captured in the following
879 table:
881 +----------------------+--------------------------------------------+
882 | WAMS Requirement | Attribute |
883 +----------------------+--------------------------------------------+
884 | One way maximum | 50 ms |
885 | delay | |
886 | Asymetric delay | No |
887 | Required | |
888 | Maximum jitter | Not critical |
889 | Topology | Point to point, point to Multi-point, |
890 | | Multi-point to Multi-point |
891 | Bandwidth | 100 Kbps |
892 | Availability | 99.9999 |
893 | precise timing | Yes |
894 | required | |
895 | Recovery time on | less than 50ms - hitless |
896 | Node failure | |
897 | performance | Yes, Mandatory |
898 | management | |
899 | Redundancy | Yes |
900 | Packet loss | 1% |
901 +----------------------+--------------------------------------------+
903 Table 7: WAMS Special Communication Requirements
905 3.1.1.4. IEC 61850 WAN engineering guidelines requirement
906 classification
908 The IEC (International Electrotechnical Commission) has recently
909 published a Technical Report which offers guidelines on how to define
910 and deploy Wide Area Networks for the interconnections of electric
911 substations, generation plants and SCADA operation centers. The IEC
912 61850-90-12 is providing a classification of WAN communication
913 requirements into 4 classes. Table 8 summarizes these requirements:
915 +----------------+------------+------------+------------+-----------+
916 | WAN | Class WA | Class WB | Class WC | Class WD |
917 | Requirement | | | | |
918 +----------------+------------+------------+------------+-----------+
919 | Application | EHV (Extra | HV (High | MV (Medium | General |
920 | field | High | Voltage) | Voltage) | purpose |
921 | | Voltage) | | | |
922 | Latency | 5 ms | 10 ms | 100 ms | > 100 ms |
923 | Jitter | 10 us | 100 us | 1 ms | 10 ms |
924 | Latency | 100 us | 1 ms | 10 ms | 100 ms |
925 | Asymetry | | | | |
926 | Time Accuracy | 1 us | 10 us | 100 us | 10 to 100 |
927 | | | | | ms |
928 | Bit Error rate | 10-7 to | 10-5 to | 10-3 | |
929 | | 10-6 | 10-4 | | |
930 | Unavailability | 10-7 to | 10-5 to | 10-3 | |
931 | | 10-6 | 10-4 | | |
932 | Recovery delay | Zero | 50 ms | 5 s | 50 s |
933 | Cyber security | extremely | High | Medium | Medium |
934 | | high | | | |
935 +----------------+------------+------------+------------+-----------+
937 Table 8: 61850-90-12 Communication Requirements; Courtesy of IEC
939 3.1.2. Generation Use Case
941 The electrical power generation frequency should be maintained within
942 a very narrow band. Deviations from the acceptable frequency range
943 are detected and the required signals are sent to the power plants
944 for 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 3.1.3. Distribution use case
973 3.1.3.1. Fault Location Isolation and Service Restoration (FLISR)
975 Fault Location, Isolation, and Service Restoration (FLISR) refers to
976 the ability to automatically locate the fault, isolate the fault, and
977 restore service in the distribution network. This will likely be the
978 first widespread application of distributed intelligence in the grid.
980 Static power switch status (open/closed) in the network dictates the
981 power flow to secondary substations. Reconfiguring the network in
982 the event of a fault is typically done manually on site to energize/
983 de-energize alternate paths. Automating the operation of substation
984 switchgear allows the flow of power to be altered automatically under
985 fault conditions.
987 FLISR can be managed centrally from a Distribution Management System
988 (DMS) or executed locally through distributed control via intelligent
989 switches and fault sensors.
991 +----------------------+--------------------------------------------+
992 | FLISR Requirement | Attribute |
993 +----------------------+--------------------------------------------+
994 | One way maximum | 80 ms |
995 | delay | |
996 | Asymetric delay | No |
997 | Required | |
998 | Maximum jitter | 40 ms |
999 | Topology | Point to point, point to Multi-point, |
1000 | | Multi-point to Multi-point |
1001 | Bandwidth | 64 Kbps |
1002 | Availability | 99.9999 |
1003 | precise timing | Yes |
1004 | required | |
1005 | Recovery time on | Depends on customer impact |
1006 | Node failure | |
1007 | performance | Yes, Mandatory |
1008 | management | |
1009 | Redundancy | Yes |
1010 | Packet loss | 0.1% |
1011 +----------------------+--------------------------------------------+
1013 Table 10: FLISR Communication Requirements
1015 3.2. Electrical Utilities Today
1017 Many utilities still rely on complex environments formed of multiple
1018 application-specific proprietary networks, including TDM networks.
1020 In this kind of environment there is no mixing of OT and IT
1021 applications on the same network, and information is siloed between
1022 operational areas.
1024 Specific calibration of the full chain is required, which is costly.
1026 This kind of environment prevents utility operations from realizing
1027 the operational efficiency benefits, visibility, and functional
1028 integration of operational information across grid applications and
1029 data networks.
1031 In addition, there are many security-related issues as discussed in
1032 the following section.
1034 3.2.1. Security Current Practices and Limitations
1036 Grid monitoring and control devices are already targets for cyber
1037 attacks, and legacy telecommunications protocols have many intrinsic
1038 network-related vulnerabilities. For example, DNP3, Modbus,
1039 PROFIBUS/PROFINET, and other protocols are designed around a common
1040 paradigm of request and respond. Each protocol is designed for a
1041 master device such as an HMI (Human Machine Interface) system to send
1042 commands to subordinate slave devices to retrieve data (reading
1043 inputs) or control (writing to outputs). Because many of these
1044 protocols lack authentication, encryption, or other basic security
1045 measures, they are prone to network-based attacks, allowing a
1046 malicious actor or attacker to utilize the request-and-respond system
1047 as a mechanism for command-and-control like functionality. Specific
1048 security concerns common to most industrial control, including
1049 utility telecommunication protocols include the following:
1051 o Network or transport errors (e.g. malformed packets or excessive
1052 latency) can cause protocol failure.
1054 o Protocol commands may be available that are capable of forcing
1055 slave devices into inoperable states, including powering-off
1056 devices, forcing them into a listen-only state, disabling
1057 alarming.
1059 o Protocol commands may be available that are capable of restarting
1060 communications and otherwise interrupting processes.
1062 o Protocol commands may be available that are capable of clearing,
1063 erasing, or resetting diagnostic information such as counters and
1064 diagnostic registers.
1066 o Protocol commands may be available that are capable of requesting
1067 sensitive information about the controllers, their configurations,
1068 or other need-to-know information.
1070 o Most protocols are application layer protocols transported over
1071 TCP; therefore it is easy to transport commands over non-standard
1072 ports or inject commands into authorized traffic flows.
1074 o Protocol commands may be available that are capable of
1075 broadcasting messages to many devices at once (i.e. a potential
1076 DoS).
1078 o Protocol commands may be available to query the device network to
1079 obtain defined points and their values (i.e. a configuration
1080 scan).
1082 o Protocol commands may be available that will list all available
1083 function codes (i.e. a function scan).
1085 These inherent vulnerabilities, along with increasing connectivity
1086 between IT an OT networks, make network-based attacks very feasible.
1088 Simple injection of malicious protocol commands provides control over
1089 the target process. Altering legitimate protocol traffic can also
1090 alter information about a process and disrupt the legitimate controls
1091 that are in place over that process. A man-in-the-middle attack
1092 could provide both control over a process and misrepresentation of
1093 data back to operator consoles.
1095 3.3. Electrical Utilities Future
1097 The business and technology trends that are sweeping the utility
1098 industry will drastically transform the utility business from the way
1099 it has been for many decades. At the core of many of these changes
1100 is a drive to modernize the electrical grid with an integrated
1101 telecommunications infrastructure. However, interoperability
1102 concerns, legacy networks, disparate tools, and stringent security
1103 requirements all add complexity to the grid transformation. Given
1104 the range and diversity of the requirements that should be addressed
1105 by the next generation telecommunications infrastructure, utilities
1106 need to adopt a holistic architectural approach to integrate the
1107 electrical grid with digital telecommunications across the entire
1108 power delivery chain.
1110 The key to modernizing grid telecommunications is to provide a
1111 common, adaptable, multi-service network infrastructure for the
1112 entire utility organization. Such a network serves as the platform
1113 for current capabilities while enabling future expansion of the
1114 network to accommodate new applications and services.
1116 To meet this diverse set of requirements, both today and in the
1117 future, the next generation utility telecommunnications network will
1118 be based on open-standards-based IP architecture. An end-to-end IP
1119 architecture takes advantage of nearly three decades of IP technology
1120 development, facilitating interoperability across disparate networks
1121 and devices, as it has been already demonstrated in many mission-
1122 critical and highly secure networks.
1124 IPv6 is seen as a future telecommunications technology for the Smart
1125 Grid; the IEC (International Electrotechnical Commission) and
1126 different National Committees have mandated a specific adhoc group
1127 (AHG8) to define the migration strategy to IPv6 for all the IEC TC57
1128 power automation standards.
1130 3.3.1. Migration to Packet-Switched Network
1132 Throughout the world, utilities are increasingly planning for a
1133 future based on smart grid applications requiring advanced
1134 telecommunications systems. Many of these applications utilize
1135 packet connectivity for communicating information and control signals
1136 across the utility's Wide Area Network (WAN), made possible by
1137 technologies such as multiprotocol label switching (MPLS). The data
1138 that traverses the utility WAN includes:
1140 o Grid monitoring, control, and protection data
1142 o Non-control grid data (e.g. asset data for condition-based
1143 monitoring)
1145 o Physical safety and security data (e.g. voice and video)
1147 o Remote worker access to corporate applications (voice, maps,
1148 schematics, etc.)
1150 o Field area network backhaul for smart metering, and distribution
1151 grid management
1153 o Enterprise traffic (email, collaboration tools, business
1154 applications)
1156 WANs support this wide variety of traffic to and from substations,
1157 the transmission and distribution grid, generation sites, between
1158 control centers, and between work locations and data centers. To
1159 maintain this rapidly expanding set of applications, many utilities
1160 are taking steps to evolve present time-division multiplexing (TDM)
1161 based and frame relay infrastructures to packet systems. Packet-
1162 based networks are designed to provide greater functionalities and
1163 higher levels of service for applications, while continuing to
1164 deliver reliability and deterministic (real-time) traffic support.
1166 3.3.2. Telecommunications Trends
1168 These general telecommunications topics are in addition to the use
1169 cases that have been addressed so far. These include both current
1170 and future telecommunications related topics that should be factored
1171 into the network architecture and design.
1173 3.3.2.1. General Telecommunications Requirements
1175 o IP Connectivity everywhere
1177 o Monitoring services everywhere and from different remote centers
1179 o Move services to a virtual data center
1181 o Unify access to applications / information from the corporate
1182 network
1184 o Unify services
1186 o Unified Communications Solutions
1188 o Mix of fiber and microwave technologies - obsolescence of SONET/
1189 SDH or TDM
1191 o Standardize grid telecommunications protocol to opened standard to
1192 ensure interoperability
1194 o Reliable Telecommunications for Transmission and Distribution
1195 Substations
1197 o IEEE 1588 time synchronization Client / Server Capabilities
1199 o Integration of Multicast Design
1201 o QoS Requirements Mapping
1203 o Enable Future Network Expansion
1205 o Substation Network Resilience
1207 o Fast Convergence Design
1209 o Scalable Headend Design
1211 o Define Service Level Agreements (SLA) and Enable SLA Monitoring
1213 o Integration of 3G/4G Technologies and future technologies
1215 o Ethernet Connectivity for Station Bus Architecture
1217 o Ethernet Connectivity for Process Bus Architecture
1219 o Protection, teleprotection and PMU (Phaser Measurement Unit) on IP
1221 3.3.2.2. Specific Network topologies of Smart Grid Applications
1223 Utilities often have very large private telecommunications networks.
1224 It covers an entire territory / country. The main purpose of the
1225 network, until now, has been to support transmission network
1226 monitoring, control, and automation, remote control of generation
1227 sites, and providing FCAPS (Fault, Configuration, Accounting,
1228 Performance, Security) services from centralized network operation
1229 centers.
1231 Going forward, one network will support operation and maintenance of
1232 electrical networks (generation, transmission, and distribution),
1233 voice and data services for ten of thousands of employees and for
1234 exchange with neighboring interconnections, and administrative
1235 services. To meet those requirements, utility may deploy several
1236 physical networks leveraging different technologies across the
1237 country: an optical network and a microwave network for instance.
1238 Each protection and automatism system between two points has two
1239 telecommunications circuits, one on each network. Path diversity
1240 between two substations is key. Regardless of the event type
1241 (hurricane, ice storm, etc.), one path shall stay available so the
1242 system can still operate.
1244 In the optical network, signals are transmitted over more than tens
1245 of thousands of circuits using fiber optic links, microwave and
1246 telephone cables. This network is the nervous system of the
1247 utility's power transmission operations. The optical network
1248 represents ten of thousands of km of cable deployed along the power
1249 lines, with individual runs as long as 280 km.
1251 3.3.2.3. Precision Time Protocol
1253 Some utilities do not use GPS clocks in generation substations. One
1254 of the main reasons is that some of the generation plants are 30 to
1255 50 meters deep under ground and the GPS signal can be weak and
1256 unreliable. Instead, atomic clocks are used. Clocks are
1257 synchronized amongst each other. Rubidium clocks provide clock and
1258 1ms timestamps for IRIG-B.
1260 Some companies plan to transition to the Precision Time Protocol
1261 (PTP, [IEEE1588]), distributing the synchronization signal over the
1262 IP/MPLS network. PTP provides a mechanism for synchronizing the
1263 clocks of participating nodes to a high degree of accuracy and
1264 precision.
1266 PTP operates based on the following assumptions:
1268 It is assumed that the network eliminates cyclic forwarding of PTP
1269 messages within each communication path (e.g. by using a spanning
1270 tree protocol).
1272 PTP is tolerant of an occasional missed message, duplicated
1273 message, or message that arrived out of order. However, PTP
1274 assumes that such impairments are relatively rare.
1276 PTP was designed assuming a multicast communication model, however
1277 PTP also supports a unicast communication model as long as the
1278 behavior of the protocol is preserved.
1280 Like all message-based time transfer protocols, PTP time accuracy
1281 is degraded by delay asymmetry in the paths taken by event
1282 messages. Asymmetry is not detectable by PTP, however, if such
1283 delays are known a priori, PTP can correct for asymmetry.
1285 IEC 61850 will recommend the use of the IEEE PTP 1588 Utility Profile
1286 (as defined in [IEC62439-3:2012] Annex B) which offers the support of
1287 redundant attachment of clocks to Parallel Redundancy Protcol (PRP)
1288 and High-availability Seamless Redundancy (HSR) networks.
1290 3.3.3. Security Trends in Utility Networks
1292 Although advanced telecommunications networks can assist in
1293 transforming the energy industry by playing a critical role in
1294 maintaining high levels of reliability, performance, and
1295 manageability, they also introduce the need for an integrated
1296 security infrastructure. Many of the technologies being deployed to
1297 support smart grid projects such as smart meters and sensors can
1298 increase the vulnerability of the grid to attack. Top security
1299 concerns for utilities migrating to an intelligent smart grid
1300 telecommunications platform center on the following trends:
1302 o Integration of distributed energy resources
1304 o Proliferation of digital devices to enable management, automation,
1305 protection, and control
1307 o Regulatory mandates to comply with standards for critical
1308 infrastructure protection
1310 o Migration to new systems for outage management, distribution
1311 automation, condition-based maintenance, load forecasting, and
1312 smart metering
1314 o Demand for new levels of customer service and energy management
1316 This development of a diverse set of networks to support the
1317 integration of microgrids, open-access energy competition, and the
1318 use of network-controlled devices is driving the need for a converged
1319 security infrastructure for all participants in the smart grid,
1320 including utilities, energy service providers, large commercial and
1321 industrial, as well as residential customers. Securing the assets of
1322 electric power delivery systems (from the control center to the
1323 substation, to the feeders and down to customer meters) requires an
1324 end-to-end security infrastructure that protects the myriad of
1325 telecommunications assets used to operate, monitor, and control power
1326 flow and measurement.
1328 "Cyber security" refers to all the security issues in automation and
1329 telecommunications that affect any functions related to the operation
1330 of the electric power systems. Specifically, it involves the
1331 concepts of:
1333 o Integrity : data cannot be altered undetectably
1335 o Authenticity : the telecommunications parties involved must be
1336 validated as genuine
1338 o Authorization : only requests and commands from the authorized
1339 users can be accepted by the system
1341 o Confidentiality : data must not be accessible to any
1342 unauthenticated users
1344 When designing and deploying new smart grid devices and
1345 telecommunications systems, it is imperative to understand the
1346 various impacts of these new components under a variety of attack
1347 situations on the power grid. Consequences of a cyber attack on the
1348 grid telecommunications network can be catastrophic. This is why
1349 security for smart grid is not just an ad hoc feature or product,
1350 it's a complete framework integrating both physical and Cyber
1351 security requirements and covering the entire smart grid networks
1352 from generation to distribution. Security has therefore become one
1353 of the main foundations of the utility telecom network architecture
1354 and must be considered at every layer with a defense-in-depth
1355 approach. Migrating to IP based protocols is key to address these
1356 challenges for two reasons:
1358 o IP enables a rich set of features and capabilities to enhance the
1359 security posture
1361 o IP is based on open standards, which allows interoperability
1362 between different vendors and products, driving down the costs
1363 associated with implementing security solutions in OT networks.
1365 Securing OT (Operation technology) telecommunications over packet-
1366 switched IP networks follow the same principles that are foundational
1367 for securing the IT infrastructure, i.e., consideration must be given
1368 to enforcing electronic access control for both person-to-machine and
1369 machine-to-machine communications, and providing the appropriate
1370 levels of data privacy, device and platform integrity, and threat
1371 detection and mitigation.
1373 3.4. Electrical Utilities Asks
1375 o Mixed L2 and L3 topologies
1377 o Deterministic behavior
1379 o Bounded latency and jitter
1381 o High availability, low recovery time
1383 o Redundancy, low packet loss
1385 o Precise timing
1387 o Centralized computing of deterministic paths
1389 o Distributed configuration may also be useful
1391 4. Building Automation Systems
1393 4.1. Use Case Description
1395 A Building Automation System (BAS) manages equipment and sensors in a
1396 building for improving residents' comfort, reducing energy
1397 consumption, and responding to failures and emergencies. For
1398 example, the BAS measures the temperature of a room using sensors and
1399 then controls the HVAC (heating, ventilating, and air conditioning)
1400 to maintain a set temperature and minimize energy consumption.
1402 A BAS primarily performs the following functions:
1404 o Periodically measures states of devices, for example humidity and
1405 illuminance of rooms, open/close state of doors, FAN speed, etc.
1407 o Stores the measured data.
1409 o Provides the measured data to BAS systems and operators.
1411 o Generates alarms for abnormal state of devices.
1413 o Controls devices (e.g. turn off room lights at 10:00 PM).
1415 4.2. Building Automation Systems Today
1416 4.2.1. BAS Architecture
1418 A typical BAS architecture of today is shown in Figure 1.
1420 +----------------------------+
1421 | |
1422 | BMS HMI |
1423 | | | |
1424 | +----------------------+ |
1425 | | Management Network | |
1426 | +----------------------+ |
1427 | | | |
1428 | LC LC |
1429 | | | |
1430 | +----------------------+ |
1431 | | Field Network | |
1432 | +----------------------+ |
1433 | | | | | |
1434 | Dev Dev Dev Dev |
1435 | |
1436 +----------------------------+
1438 BMS := Building Management Server
1439 HMI := Human Machine Interface
1440 LC := Local Controller
1442 Figure 1: BAS architecture
1444 There are typically two layers of network in a BAS. The upper one is
1445 called the Management Network and the lower one is called the Field
1446 Network. In management networks an IP-based communication protocol
1447 is used, while in field networks non-IP based communication protocols
1448 ("field protocols") are mainly used. Field networks have specific
1449 timing requirements, whereas management networks can be best-effort.
1451 A Human Machine Interface (HMI) is typically a desktop PC used by
1452 operators to monitor and display device states, send device control
1453 commands to Local Controllers (LCs), and configure building schedules
1454 (for example "turn off all room lights in the building at 10:00 PM").
1456 A Building Management Server (BMS) performs the following operations.
1458 o Collect and store device states from LCs at regular intervals.
1460 o Send control values to LCs according to a building schedule.
1462 o Send an alarm signal to operators if it detects abnormal devices
1463 states.
1465 The BMS and HMI communicate with LCs via IP-based "management
1466 protocols" (see standards [bacnetip], [knx]).
1468 A LC is typically a Programmable Logic Controller (PLC) which is
1469 connected to several tens or hundreds of devices using "field
1470 protocols". An LC performs the following kinds of operations:
1472 o Measure device states and provide the information to BMS or HMI.
1474 o Send control values to devices, unilaterally or as part of a
1475 feedback control loop.
1477 There are many field protocols used today; some are standards-based
1478 and others are proprietary (see standards [lontalk], [modbus],
1479 [profibus] and [flnet]). The result is that BASs have multiple MAC/
1480 PHY modules and interfaces. This makes BASs more expensive, slower
1481 to develop, and can result in "vendor lock-in" with multiple types of
1482 management applications.
1484 4.2.2. BAS Deployment Model
1486 An example BAS for medium or large buildings is shown in Figure 2.
1487 The physical layout spans multiple floors, and there is a monitoring
1488 room where the BAS management entities are located. Each floor will
1489 have one or more LCs depending upon the number of devices connected
1490 to the field network.
1492 +--------------------------------------------------+
1493 | Floor 3 |
1494 | +----LC~~~~+~~~~~+~~~~~+ |
1495 | | | | | |
1496 | | Dev Dev Dev |
1497 | | |
1498 |--- | ------------------------------------------|
1499 | | Floor 2 |
1500 | +----LC~~~~+~~~~~+~~~~~+ Field Network |
1501 | | | | | |
1502 | | Dev Dev Dev |
1503 | | |
1504 |--- | ------------------------------------------|
1505 | | Floor 1 |
1506 | +----LC~~~~+~~~~~+~~~~~+ +-----------------|
1507 | | | | | | Monitoring Room |
1508 | | Dev Dev Dev | |
1509 | | | BMS HMI |
1510 | | Management Network | | | |
1511 | +--------------------------------+-----+ |
1512 | | |
1513 +--------------------------------------------------+
1515 Figure 2: BAS Deployment model for Medium/Large Buildings
1517 Each LC is connected to the monitoring room via the Management
1518 network, and the management functions are performed within the
1519 building. In most cases, fast Ethernet (e.g. 100BASE-T) is used for
1520 the management network. Since the management network is non-
1521 realtime, use of Ethernet without quality of service is sufficient
1522 for today's deployment.
1524 In the field network a variety of physical interfaces such as RS232C
1525 and RS485 are used, which have specific timing requirements. Thus if
1526 a field network is to be replaced with an Ethernet or wireless
1527 network, such networks must support time-critical deterministic
1528 flows.
1530 In Figure 3, another deployment model is presented in which the
1531 management system is hosted remotely. This is becoming popular for
1532 small office and residential buildings in which a standalone
1533 monitoring system is not cost-effective.
1535 +---------------+
1536 | Remote Center |
1537 | |
1538 | BMS HMI |
1539 +------------------------------------+ | | | |
1540 | Floor 2 | | +---+---+ |
1541 | +----LC~~~~+~~~~~+ Field Network| | | |
1542 | | | | | | Router |
1543 | | Dev Dev | +-------|-------+
1544 | | | |
1545 |--- | ------------------------------| |
1546 | | Floor 1 | |
1547 | +----LC~~~~+~~~~~+ | |
1548 | | | | | |
1549 | | Dev Dev | |
1550 | | | |
1551 | | Management Network | WAN |
1552 | +------------------------Router-------------+
1553 | |
1554 +------------------------------------+
1556 Figure 3: Deployment model for Small Buildings
1558 Some interoperability is possible today in the Management Network,
1559 but not in today's field networks due to their non-IP-based design.
1561 4.2.3. Use Cases for Field Networks
1563 Below are use cases for Environmental Monitoring, Fire Detection, and
1564 Feedback Control, and their implications for field network
1565 performance.
1567 4.2.3.1. Environmental Monitoring
1569 The BMS polls each LC at a maximum measurement interval of 100ms (for
1570 example to draw a historical chart of 1 second granularity with a 10x
1571 sampling interval) and then performs the operations as specified by
1572 the operator. Each LC needs to measure each of its several hundred
1573 sensors once per measurement interval. Latency is not critical in
1574 this scenario as long as all sensor values are completed in the
1575 measurement interval. Availability is expected to be 99.999 %.
1577 4.2.3.2. Fire Detection
1579 On detection of a fire, the BMS must stop the HVAC, close the fire
1580 shutters, turn on the fire sprinklers, send an alarm, etc. There are
1581 typically ~10s of sensors per LC that BMS needs to manage. In this
1582 scenario the measurement interval is 10-50ms, the communication delay
1583 is 10ms, and the availability must be 99.9999 %.
1585 4.2.3.3. Feedback Control
1587 BAS systems utilize feedback control in various ways; the most time-
1588 critial is control of DC motors, which require a short feedback
1589 interval (1-5ms) with low communication delay (10ms) and jitter
1590 (1ms). The feedback interval depends on the characteristics of the
1591 device and a target quality of control value. There are typically
1592 ~10s of such devices per LC.
1594 Communication delay is expected to be less than 10 ms, jitter less
1595 than 1 sec while the availability must be 99.9999% .
1597 4.2.4. Security Considerations
1599 When BAS field networks were developed it was assumed that the field
1600 networks would always be physically isolated from external networks
1601 and therefore security was not a concern. In today's world many BASs
1602 are managed remotely and are thus connected to shared IP networks and
1603 so security is definitely a concern, yet security features are not
1604 available in the majority of BAS field network deployments .
1606 The management network, being an IP-based network, has the protocols
1607 available to enable network security, but in practice many BAS
1608 systems do not implement even the available security features such as
1609 device authentication or encryption for data in transit.
1611 4.3. BAS Future
1613 In the future we expect more fine-grained environmental monitoring
1614 and lower energy consumption, which will require more sensors and
1615 devices, thus requiring larger and more complex building networks.
1617 We expect building networks to be connected to or converged with
1618 other networks (Enterprise network, Home network, and Internet).
1620 Therefore better facilities for network management, control,
1621 reliability and security are critical in order to improve resident
1622 and operator convenience and comfort. For example the ability to
1623 monitor and control building devices via the internet would enable
1624 (for example) control of room lights or HVAC from a resident's
1625 desktop PC or phone application.
1627 4.4. BAS Asks
1629 The community would like to see an interoperable protocol
1630 specification that can satisfy the timing, security, availability and
1631 QoS constraints described above, such that the resulting converged
1632 network can replace the disparate field networks. Ideally this
1633 connectivity could extend to the open Internet.
1635 This would imply an architecture that can guarantee
1637 o Low communication delays (from <10ms to 100ms in a network of
1638 several hundred devices)
1640 o Low jitter (< 1 ms)
1642 o Tight feedback intervals (1ms - 10ms)
1644 o High network availability (up to 99.9999% )
1646 o Availability of network data in disaster scenario
1648 o Authentication between management and field devices (both local
1649 and remote)
1651 o Integrity and data origin authentication of communication data
1652 between field and management devices
1654 o Confidentiality of data when communicated to a remote device
1656 5. Wireless for Industrial
1658 5.1. Use Case Description
1660 Wireless networks are useful for industrial applications, for example
1661 when portable, fast-moving or rotating objects are involved, and for
1662 the resource-constrained devices found in the Internet of Things
1663 (IoT).
1665 Such network-connected sensors, actuators, control loops (etc.)
1666 typically require that the underlying network support real-time
1667 quality of service (QoS), as well as specific classes of other
1668 network properties such as reliability, redundancy, and security.
1670 These networks may also contain very large numbers of devices, for
1671 example for factories, "big data" acquisition, and the IoT. Given
1672 the large numbers of devices installed, and the potential
1673 pervasiveness of the IoT, this is a huge and very cost-sensitive
1674 market. For example, a 1% cost reduction in some areas could save
1675 $100B
1677 5.1.1. Network Convergence using 6TiSCH
1679 Some wireless network technologies support real-time QoS, and are
1680 thus useful for these kinds of networks, but others do not. For
1681 example WiFi is pervasive but does not provide guaranteed timing or
1682 delivery of packets, and thus is not useful in this context.
1684 In this use case we focus on one specific wireless network technology
1685 which does provide the required deterministic QoS, which is "IPv6
1686 over the TSCH mode of IEEE 802.15.4e" (6TiSCH, where TSCH stands for
1687 "Time-Slotted Channel Hopping", see [I-D.ietf-6tisch-architecture],
1688 [IEEE802154], [IEEE802154e], and [RFC7554]).
1690 There are other deterministic wireless busses and networks available
1691 today, however they are imcompatible with each other, and
1692 incompatible with IP traffic (for example [ISA100], [WirelessHART]).
1694 Thus the primary goal of this use case is to apply 6TiSH as a
1695 converged IP- and standards-based wireless network for industrial
1696 applications, i.e. to replace multiple proprietary and/or
1697 incompatible wireless networking and wireless network management
1698 standards.
1700 5.1.2. Common Protocol Development for 6TiSCH
1702 Today there are a number of protocols required by 6TiSCH which are
1703 still in development, and a second intent of this use case is to
1704 highlight the ways in which these "missing" protocols share goals in
1705 common with DetNet. Thus it is possible that some of the protocol
1706 technology developed for DetNet will also be applicable to 6TiSCH.
1708 These protocol goals are identified here, along with their
1709 relationship to DetNet. It is likely that ultimately the resulting
1710 protocols will not be identical, but will share design principles
1711 which contribute to the eficiency of enabling both DetNet and 6TiSCH.
1713 One such commonality is that although at a different time scale, in
1714 both TSN [IEEE802.1TSNTG] and TSCH a packet crosses the network from
1715 node to node follows a precise schedule, as a train that leaves
1716 intermediate stations at precise times along its path. This kind of
1717 operation reduces collisions, saves energy, and enables engineering
1718 the network for deterministic properties.
1720 Another commonality is remote monitoring and scheduling management of
1721 a TSCH network by a Path Computation Element (PCE) and Network
1722 Management Entity (NME). The PCE/NME manage timeslots and device
1723 resources in a manner that minimizes the interaction with and the
1724 load placed on resource-constrained devices. For example, a tiny IoT
1725 device may have just enough buffers to store one or a few IPv6
1726 packets, and will have limited bandwidth between peers such that it
1727 can maintain only a small amount of peer information, and will not be
1728 able to store many packets waiting to be forwarded. It is
1729 advantageous then for it to only be required to carry out the
1730 specific behavior assigned to it by the PCE/NME (as opposed to
1731 maintaining its own IP stack, for example).
1733 6TiSCH depends on [PCE] and [I-D.finn-detnet-architecture], and we
1734 expect that DetNet will maintain consistency with [IEEE802.1TSNTG].
1736 5.2. Wireless Industrial Today
1738 Today industrial wireless is accomplished using multiple
1739 deterministic wireless networks which are incompatible with each
1740 other and with IP traffic.
1742 6TiSCH is not yet fully specified, so it cannot be used in today's
1743 applications.
1745 5.3. Wireless Industrial Future
1747 5.3.1. Unified Wireless Network and Management
1749 We expect DetNet and 6TiSCH together to enable converged transport of
1750 deterministic and best-effort traffic flows between real-time
1751 industrial devices and wide area networks via IP routing. A high
1752 level view of a basic such network is shown in Figure 4.
1754 ---+-------- ............ ------------
1755 | External Network |
1756 | +-----+
1757 +-----+ | NME |
1758 | | LLN Border | |
1759 | | router +-----+
1760 +-----+
1761 o o o
1762 o o o o
1763 o o LLN o o o
1764 o o o o
1765 o
1767 Figure 4: Basic 6TiSCH Network
1769 Figure 5 shows a backbone router federating multiple synchronized
1770 6TiSCH subnets into a single subnet connected to the external
1771 network.
1773 ---+-------- ............ ------------
1774 | External Network |
1775 | +-----+
1776 | +-----+ | NME |
1777 +-----+ | +-----+ | |
1778 | | Router | | PCE | +-----+
1779 | | +--| |
1780 +-----+ +-----+
1781 | |
1782 | Subnet Backbone |
1783 +--------------------+------------------+
1784 | | |
1785 +-----+ +-----+ +-----+
1786 | | Backbone | | Backbone | | Backbone
1787 o | | router | | router | | router
1788 +-----+ +-----+ +-----+
1789 o o o o o
1790 o o o o o o o o o o o
1791 o o o LLN o o o o
1792 o o o o o o o o o o o o
1794 Figure 5: Extended 6TiSCH Network
1796 The backbone router must ensure end-to-end deterministic behavior
1797 between the LLN and the backbone. We would like to see this
1798 accomplished in conformance with the work done in
1799 [I-D.finn-detnet-architecture] with respect to Layer-3 aspects of
1800 deterministic networks that span multiple Layer-2 domains.
1802 The PCE must compute a deterministic path end-to-end across the TSCH
1803 network and IEEE802.1 TSN Ethernet backbone, and DetNet protocols are
1804 expected to enable end-to-end deterministic forwarding.
1806 +-----+
1807 | IoT |
1808 | G/W |
1809 +-----+
1810 ^ <---- Elimination
1811 | |
1812 Track branch | |
1813 +-------+ +--------+ Subnet Backbone
1814 | |
1815 +--|--+ +--|--+
1816 | | | Backbone | | | Backbone
1817 o | | | router | | | router
1818 +--/--+ +--|--+
1819 o / o o---o----/ o
1820 o o---o--/ o o o o o
1821 o \ / o o LLN o
1822 o v <---- Replication
1823 o
1825 Figure 6: 6TiSCH Network with PRE
1827 5.3.1.1. PCE and 6TiSCH ARQ Retries
1829 6TiSCH uses the IEEE802.15.4 Automatic Repeat-reQuest (ARQ) mechanism
1830 to provide higher reliability of packet delivery. ARQ is related to
1831 packet replication and elimination because there are two independent
1832 paths for packets to arrive at the destination, and if an expected
1833 packed does not arrive on one path then it checks for the packet on
1834 the second path.
1836 Although to date this mechanism is only used by wireless networks,
1837 this may be a technique that would be appropriate for DetNet and so
1838 aspects of the enabling protocol could be co-developed.
1840 For example, in Figure 6, a Track is laid out from a field device in
1841 a 6TiSCH network to an IoT gateway that is located on a IEEE802.1 TSN
1842 backbone.
1844 The Replication function in the field device sends a copy of each
1845 packet over two different branches, and the PCE schedules each hop of
1846 both branches so that the two copies arrive in due time at the
1847 gateway. In case of a loss on one branch, hopefully the other copy
1848 of the packet still arrives within the allocated time. If two copies
1849 make it to the IoT gateway, the Elimination function in the gateway
1850 ignores the extra packet and presents only one copy to upper layers.
1852 At each 6TiSCH hop along the Track, the PCE may schedule more than
1853 one timeSlot for a packet, so as to support Layer-2 retries (ARQ).
1855 In current deployments, a TSCH Track does not necessarily support PRE
1856 but is systematically multi-path. This means that a Track is
1857 scheduled so as to ensure that each hop has at least two forwarding
1858 solutions, and the forwarding decision is to try the preferred one
1859 and use the other in case of Layer-2 transmission failure as detected
1860 by ARQ.
1862 5.3.2. Schedule Management by a PCE
1864 A common feature of 6TiSCH and DetNet is the action of a PCE to
1865 configure paths through the network. Specifically, what is needed is
1866 a protocol and data model that the PCE will use to get/set the
1867 relevant configuration from/to the devices, as well as perform
1868 operations on the devices. We expect that this protocol will be
1869 developed by DetNet with consideration for its reuse by 6TiSCH. The
1870 remainder of this section provides a bit more context from the 6TiSCH
1871 side.
1873 5.3.2.1. PCE Commands and 6TiSCH CoAP Requests
1875 The 6TiSCH device does not expect to place the request for bandwidth
1876 between itself and another device in the network. Rather, an
1877 operation control system invoked through a human interface specifies
1878 the required traffic specification and the end nodes (in terms of
1879 latency and reliability). Based on this information, the PCE must
1880 compute a path between the end nodes and provision the network with
1881 per-flow state that describes the per-hop operation for a given
1882 packet, the corresponding timeslots, and the flow identification that
1883 enables recognizing that a certain packet belongs to a certain path,
1884 etc.
1886 For a static configuration that serves a certain purpose for a long
1887 period of time, it is expected that a node will be provisioned in one
1888 shot with a full schedule, which incorporates the aggregation of its
1889 behavior for multiple paths. 6TiSCH expects that the programing of
1890 the schedule will be done over COAP as discussed in
1891 [I-D.ietf-6tisch-coap].
1893 6TiSCH expects that the PCE commands will be issued directly as CoAP
1894 requests or be mapped back and forth into CoAP by a gateway function
1895 at the edge of the 6TiSCH network. For instance, it is possible that
1896 a mapping entity on the backbone transforms a non-CoAP protocol such
1897 as PCEP into the RESTful interfaces that the 6TiSCH devices support.
1898 This architecture will be refined to comply with DetNet
1899 [I-D.finn-detnet-architecture] when the work is formalized. Related
1900 information about 6TiSCH can be found at
1901 [I-D.ietf-6tisch-6top-interface] and RPL [RFC6550].
1903 If it appears that a path through the network does not perform as
1904 expected, a protocol may be used to update the state in the devices,
1905 but in 6TiSCH that flow was not designed and no protocol was selected
1906 and it is expected that DetNet will determine the appropriate end-to-
1907 end protocols to be used in that case.
1909 A "slotFrame" is the base object that the PCE needs to manipulate to
1910 program a schedule into an LLN node ([I-D.ietf-6tisch-architecture]).
1912 The PCE should be able to read energy data from devices, and compute
1913 paths that will implement policies on how energy in devices is
1914 consumed, for instance to ensure that the spent energy does not
1915 exceeded the available energy over a period of time.
1917 6TiSCH devices can discover their neighbors over the radio using a
1918 mechanism such as beacons, but even though the neighbor information
1919 is available in the 6TiSCH interface data model, 6TiSCH does not
1920 describe a protocol to proactively push the neighborhood information
1921 to a PCE. DetNet should define this protocol, and it and should
1922 operate over CoAP. The protocol should be able to carry multiple
1923 metrics, in particular the same metrics as used for RPL operations
1924 [RFC6551]
1926 5.3.2.2. 6TiSCH IP Interface
1928 "6top" ([I-D.wang-6tisch-6top-sublayer]) is a logical link control
1929 sitting between the IP layer and the TSCH MAC layer which provides
1930 the link abstraction that is required for IP operations. The 6top
1931 data model and management interfaces are further discussed in
1932 [I-D.ietf-6tisch-6top-interface] and [I-D.ietf-6tisch-coap].
1934 An IP packet that is sent along a 6TiSCH path uses the Differentiated
1935 Services Per-Hop-Behavior Group called Deterministic Forwarding, as
1936 described in [I-D.svshah-tsvwg-deterministic-forwarding].
1938 5.3.3. 6TiSCH Security Considerations
1940 On top of the classical requirements for protection of control
1941 signaling, it must be noted that 6TiSCH networks operate on limited
1942 resources that can be depleted rapidly in a DoS attack on the system,
1943 for instance by placing a rogue device in the network, or by
1944 obtaining management control and setting up unexpected additional
1945 paths.
1947 5.4. Wireless Industrial Asks
1949 6TiSCH depends on DetNet to define:
1951 o Configuration (state) and operations for deterministic paths
1953 o End-to-end protocols for deterministic forwarding (tagging, IP)
1955 o Protocol for packet replication and elimination
1957 o Protocol for packet automatic retries (ARQ) (specific to wireless)
1959 6. Cellular Radio Use Cases
1961 6.1. Use Case Description
1963 This use case describes the application of deterministic networking
1964 in the context of cellular telecom transport networks. Important
1965 elements include time synchronization, clock distribution, and ways
1966 of establishing time-sensitive streams for both Layer-2 and Layer-3
1967 user plane traffic.
1969 6.1.1. Network Architecture
1971 Figure 7 illustrates a typical 3GPP-defined cellular network
1972 architecture, which includes "Fronthaul" and "Midhaul" network
1973 segments. The "Fronthaul" is the network connecting base stations
1974 (baseband processing units) to the remote radio heads (antennas).
1975 The "Midhaul" is the network inter-connecting base stations (or small
1976 cell sites).
1978 In Figure 7 "eNB" ("E-UTRAN Node B") is the hardware that is
1979 connected to the mobile phone network which communicates directly
1980 with mobile handsets ([TS36300]).
1982 Y (remote radio heads (antennas))
1983 \
1984 Y__ \.--. .--. +------+
1985 \_( `. +---+ _(Back`. | 3GPP |
1986 Y------( Front )----|eNB|----( Haul )----| core |
1987 ( ` .Haul ) +---+ ( ` . ) ) | netw |
1988 /`--(___.-' \ `--(___.-' +------+
1989 Y_/ / \.--. \
1990 Y_/ _( Mid`. \
1991 ( Haul ) \
1992 ( ` . ) ) \
1993 `--(___.-'\_____+---+ (small cell sites)
1994 \ |SCe|__Y
1995 +---+ +---+
1996 Y__|eNB|__Y
1997 +---+
1998 Y_/ \_Y ("local" radios)
2000 Figure 7: Generic 3GPP-based Cellular Network Architecture
2002 The available processing time for Fronthaul networking overhead is
2003 limited to the available time after the baseband processing of the
2004 radio frame has completed. For example in Long Term Evolution (LTE)
2005 radio, processing of a radio frame is allocated 3ms, but typically
2006 the processing completes much earlier (<400us) allowing the remaining
2007 time to be used by the Fronthaul network. This ultimately determines
2008 the distance the remote radio heads can be located from the base
2009 stations (200us equals roughly 40 km of optical fiber-based
2010 transport, thus round trip time is 2*200us = 400us).
2012 The remainder of the "maximum delay budget" is consumed by all nodes
2013 and buffering between the remote radio head and the baseband
2014 processing, plus the distance-incurred delay.
2016 The baseband processing time and the available "delay budget" for the
2017 fronthaul is likely to change in the forthcoming "5G" due to reduced
2018 radio round trip times and other architectural and service
2019 requirements [NGMN].
2021 6.1.2. Time Synchronization Requirements
2023 Fronthaul time synchronization requirements are given by [TS25104],
2024 [TS36104], [TS36211], and [TS36133]. These can be summarized for the
2025 current 3GPP LTE-based networks as:
2027 Delay Accuracy:
2028 +-8ns (i.e. +-1/32 Tc, where Tc is the UMTS Chip time of 1/3.84
2029 MHz) resulting in a round trip accuracy of +-16ns. The value is
2030 this low to meet the 3GPP Timing Alignment Error (TAE) measurement
2031 requirements.
2033 Packet Delay Variation:
2034 Packet Delay Variation (PDV aka Jitter aka Timing Alignment Error)
2035 is problematic to Fronthaul networks and must be minimized. If
2036 the transport network cannot guarantee low enough PDV then
2037 additional buffering has to be introduced at the edges of the
2038 network to buffer out the jitter. Buffering is not desirable as
2039 it reduces the total available delay budget.
2041 * For multiple input multiple output (MIMO) or TX diversity
2042 transmissions, at each carrier frequency, TAE shall not exceed
2043 65 ns (i.e. 1/4 Tc).
2045 * For intra-band contiguous carrier aggregation, with or without
2046 MIMO or TX diversity, TAE shall not exceed 130 ns (i.e. 1/2
2047 Tc).
2049 * For intra-band non-contiguous carrier aggregation, with or
2050 without MIMO or TX diversity, TAE shall not exceed 260 ns (i.e.
2051 one Tc).
2053 * For inter-band carrier aggregation, with or without MIMO or TX
2054 diversity, TAE shall not exceed 260 ns.
2056 Transport link contribution to radio frequency error:
2057 +-2 PPB. This value is considered to be "available" for the
2058 Fronthaul link out of the total 50 PPB budget reserved for the
2059 radio interface. Note: the reason that the transport link
2060 contributes to radio frequency error is as follows. The current
2061 way of doing Fronthaul is from the radio unit to remote radio head
2062 directly. The remote radio head is essentially a passive device
2063 (without buffering etc.) The transport drives the antenna
2064 directly by feeding it with samples and everything the transport
2065 adds will be introduced to radio as-is. So if the transport
2066 causes additional frequence error that shows immediately on the
2067 radio as well.
2069 The above listed time synchronization requirements are difficult to
2070 meet with point-to-point connected networks, and more difficult when
2071 the network includes multiple hops. It is expected that networks
2072 must include buffering at the ends of the connections as imposed by
2073 the jitter requirements, since trying to meet the jitter requirements
2074 in every intermediate node is likely to be too costly. However,
2075 every measure to reduce jitter and delay on the path makes it easier
2076 to meet the end-to-end requirements.
2078 In order to meet the timing requirements both senders and receivers
2079 must remain time synchronized, demanding very accurate clock
2080 distribution, for example support for IEEE 1588 transparent clocks in
2081 every intermediate node.
2083 In cellular networks from the LTE radio era onward, phase
2084 synchronization is needed in addition to frequency synchronization
2085 ([TS36300], [TS23401]).
2087 6.1.3. Time-Sensitive Stream Requirements
2089 In addition to the time synchronization requirements listed in
2090 Section Section 6.1.2 the Fronthaul networks assume practically
2091 error-free transport. The maximum bit error rate (BER) has been
2092 defined to be 10^-12. When packetized that would imply a packet
2093 error rate (PER) of 2.4*10^-9 (assuming ~300 bytes packets).
2094 Retransmitting lost packets and/or using forward error correction
2095 (FEC) to circumvent bit errors is practically impossible due to the
2096 additional delay incurred. Using redundant streams for better
2097 guarantees for delivery is also practically impossible in many cases
2098 due to high bandwidth requirements of Fronthaul networks. For
2099 instance, current uncompressed CPRI bandwidth expansion ratio is
2100 roughly 20:1 compared to the IP layer user payload it carries.
2101 Protection switching is also a candidate but current technologies for
2102 the path switch are too slow. We do not currently know of a better
2103 solution for this issue.
2105 Fronthaul links are assumed to be symmetric, and all Fronthaul
2106 streams (i.e. those carrying radio data) have equal priority and
2107 cannot delay or pre-empt each other. This implies that the network
2108 must guarantee that each time-sensitive flow meets their schedule.
2110 6.1.4. Security Considerations
2112 Establishing time-sensitive streams in the network entails reserving
2113 networking resources for long periods of time. It is important that
2114 these reservation requests be authenticated to prevent malicious
2115 reservation attempts from hostile nodes (or accidental
2116 misconfiguration). This is particularly important in the case where
2117 the reservation requests span administrative domains. Furthermore,
2118 the reservation information itself should be digitally signed to
2119 reduce the risk of a legitimate node pushing a stale or hostile
2120 configuration into another networking node.
2122 6.2. Cellular Radio Networks Today
2124 Today's Fronthaul networks typically consist of:
2126 o Dedicated point-to-point fiber connection is common
2128 o Proprietary protocols and framings
2130 o Custom equipment and no real networking
2132 Today's Midhaul and Backhaul networks typically consist of:
2134 o Mostly normal IP networks, MPLS-TP, etc.
2136 o Clock distribution and sync using 1588 and SyncE
2138 Telecommunication networks in the cellular domain are already heading
2139 towards transport networks where precise time synchronization support
2140 is one of the basic building blocks. While the transport networks
2141 themselves have practically transitioned to all-IP packet based
2142 networks to meet the bandwidth and cost requirements, highly accurate
2143 clock distribution has become a challenge.
2145 Transport networks in the cellular domain are typically based on Time
2146 Division Multiplexing (TDM-based) and provide frequency
2147 synchronization capabilities as a part of the transport media.
2148 Alternatively other technologies such as Global Positioning System
2149 (GPS) or Synchronous Ethernet (SyncE) are used [SyncE].
2151 Both Ethernet and IP/MPLS [RFC3031] (and PseudoWires (PWE) [RFC3985]
2152 for legacy transport support) have become popular tools to build and
2153 manage new all-IP Radio Access Networks (RAN)
2154 [I-D.kh-spring-ip-ran-use-case]. Although various timing and
2155 synchronization optimizations have already been proposed and
2156 implemented including 1588 PTP enhancements
2157 [I-D.ietf-tictoc-1588overmpls][I-D.mirsky-mpls-residence-time], these
2158 solution are not necessarily sufficient for the forthcoming RAN
2159 architectures or guarantee the higher time-synchronization
2160 requirements [CPRI]. There are also existing solutions for the TDM
2161 over IP [RFC5087] [RFC4553] or Ethernet transports [RFC5086].
2163 6.3. Cellular Radio Networks Future
2165 We would like to see the following in future Cellular Radio networks:
2167 o Unified standards-based transport protocols and standard
2168 networking equipment that can make use of underlying deterministic
2169 link-layer services
2171 o Unified and standards-based network management systems and
2172 protocols in all parts of the network (including Fronthaul)
2174 New radio access network deployment models and architectures may
2175 require time sensitive networking services with strict requirements
2176 on other parts of the network that previously were not considered to
2177 be packetized at all. The time and synchronization support are
2178 already topical for Backhaul and Midhaul packet networks [MEF], and
2179 becoming a real issue for Fronthaul networks. Specifically in the
2180 Fronthaul networks the timing and synchronization requirements can be
2181 extreme for packet based technologies, for example, on the order of
2182 sub +-20 ns packet delay variation (PDV) and frequency accuracy of
2183 +0.002 PPM [Fronthaul].
2185 The actual transport protocols and/or solutions to establish required
2186 transport "circuits" (pinned-down paths) for Fronthaul traffic are
2187 still undefined. Those are likely to include (but are not limited
2188 to) solutions directly over Ethernet, over IP, and MPLS/PseudoWire
2189 transport.
2191 Even the current time-sensitive networking features may not be
2192 sufficient for Fronthaul traffic. Therefore, having specific
2193 profiles that take the requirements of Fronthaul into account is
2194 desirable [IEEE8021CM].
2196 The really interesting and important existing work for time sensitive
2197 networking has been done for Ethernet [TSNTG], which specifies the
2198 use of IEEE 1588 time precision protocol (PTP) [IEEE1588] in the
2199 context of IEEE 802.1D and IEEE 802.1Q. While IEEE 802.1AS
2200 [IEEE8021AS] specifies a Layer-2 time synchronizing service other
2201 specification, such as IEEE 1722 [IEEE1722] specify Ethernet-based
2202 Layer-2 transport for time-sensitive streams. New promising work
2203 seeks to enable the transport of time-sensitive fronthaul streams in
2204 Ethernet bridged networks [IEEE8021CM]. Similarly to IEEE 1722 there
2205 is an ongoing standardization effort to define Layer-2 transport
2206 encapsulation format for transporting radio over Ethernet (RoE) in
2207 IEEE 1904.3 Task Force [IEEE19043].
2209 All-IP RANs and various "haul" networks would benefit from time
2210 synchronization and time-sensitive transport services. Although
2211 Ethernet appears to be the unifying technology for the transport
2212 there is still a disconnect providing Layer-3 services. The protocol
2213 stack typically has a number of layers below the Ethernet Layer-2
2214 that shows up to the Layer-3 IP transport. It is not uncommon that
2215 on top of the lowest layer (optical) transport there is the first
2216 layer of Ethernet followed one or more layers of MPLS, PseudoWires
2217 and/or other tunneling protocols finally carrying the Ethernet layer
2218 visible to the user plane IP traffic. While there are existing
2219 technologies, especially in MPLS/PWE space, to establish circuits
2220 through the routed and switched networks, there is a lack of
2221 signaling the time synchronization and time-sensitive stream
2222 requirements/reservations for Layer-3 flows in a way that the entire
2223 transport stack is addressed and the Ethernet layers that needs to be
2224 configured are addressed.
2226 Furthermore, not all "user plane" traffic will be IP. Therefore, the
2227 same solution also must address the use cases where the user plane
2228 traffic is again another layer or Ethernet frames. There is existing
2229 work describing the problem statement
2230 [I-D.finn-detnet-problem-statement] and the architecture
2231 [I-D.finn-detnet-architecture] for deterministic networking (DetNet)
2232 that targets solutions for time-sensitive (IP/transport) streams with
2233 deterministic properties over Ethernet-based switched networks.
2235 6.4. Cellular Radio Networks Asks
2237 A standard for data plane transport specification which is:
2239 o Unified among all *hauls
2241 o Deployed in a highly deterministic network environment
2243 A standard for data flow information models that are:
2245 o Aware of the time sensitivity and constraints of the target
2246 networking environment
2248 o Aware of underlying deterministic networking services (e.g. on the
2249 Ethernet layer)
2251 Mapping the Fronthaul requirements to IETF DetNet
2252 [I-D.finn-detnet-architecture] Section 3 "Providing the DetNet
2253 Quality of Service", the relevant features are:
2255 o Zero congestion loss.
2257 o Pinned-down paths.
2259 7. Cellular Coordinated Multipoint Processing (CoMP)
2261 7.1. Use Case Description
2263 In cellular wireless communication systems, Inter-Site Coordinated
2264 Multipoint Processing (CoMP, see [CoMP]) is a technique implemented
2265 within a cell site which improves system efficiency and user quality
2266 experience by significantly improving throughput in the cell-edge
2267 region (i.e. at the edges of that cell site's radio coverage area).
2268 CoMP techniques depend on deterministic high-reliability
2269 communication between cell sites, however such connections today are
2270 IP-based which in current mobile networks can not meet the QoS
2271 requirements, so CoMP is an emerging technology which can benefit
2272 from DetNet.
2274 Here we consider the JT (Joint Transmit) application for CoMP, which
2275 provides the highest performance gain (compared to other
2276 applications).
2278 7.1.1. CoMP Architecture
2280 +--------------------------+
2281 | CoMP |
2282 +--+--------------------+--+
2283 | |
2284 +----------+ +------------+
2285 | Uplink | | Downlink |
2286 +-----+----+ +--------+---+
2287 | |
2288 ------------------- -----------------------
2289 | | | | | |
2290 +---------+ +----+ +-----+ +------------+ +-----+ +-----+
2291 | Joint | | CS | | DPS | | Joint | | CS/ | | DPS |
2292 |Reception| | | | | |Transmission| | CB | | |
2293 +---------+ +----+ +-----+ +------------+ +-----+ +-----+
2294 | |
2295 |----------- |-------------
2296 | | | |
2297 +------------+ +---------+ +----------+ +------------+
2298 | Joint | | Soft | | Coherent | | Non- |
2299 |Equalization| |Combining| | JT | | Coherent JT|
2300 +------------+ +---------+ +----------+ +------------+
2302 Figure 8: Framework of CoMP Technology
2304 As shown in Figure 8, CoMP reception and transmission is a framework
2305 in which multiple geographically distributed antenna nodes cooperate
2306 to improve the performance of the users served in the common
2307 cooperation area. The design principal of CoMP is to extend the
2308 current single-cell to multi-UE (User Equipment) transmission to a
2309 multi-cell- to-multi-UEs transmission by base station cooperation.
2311 7.1.2. Delay Sensitivity in CoMP
2313 In contrast to the single-cell scenario, CoMP has delay-sensitive
2314 performance parameters, which are "backhaul latency" and "CSI
2315 (Channel State Information) reporting and accuracy". The essential
2316 feature of CoMP is signaling between eNBs, so the backhaul latency is
2317 the dominating limitation of the CoMP performance. Generally, JT can
2318 benefit from coordinated scheduling (either distributed or
2319 centralized) of different cells if the signaling delay between eNBs
2320 is within 4-10ms. This delay requirement is both rigid and absolute
2321 because any uncertainty in delay will degrade the performance
2322 significantly.
2324 7.2. CoMP Today
2326 Due to the strict sensitivity to latency and synchronization, CoMP
2327 between eNB has not been deployed yet. This is because the current
2328 interface path between eNBs cannot meet the delay bound because it is
2329 usually IP-based and passing through multiple network hops (this
2330 interface is called "X2" or "eX2" for "enhanced X2"). Today lack of
2331 absolute delay guarantee on X2/eX2 traffic is the main obstacle to JT
2332 and multi-eNB coordination.
2334 There is still lack of Layer-3 (IP) transport protocol and signaling
2335 that is capable of low latency services; current techniques such as
2336 MPLS and PWE focus on establishing circuits using pre-routed paths
2337 but there is no such signaling for reservation of time-sensitive
2338 stream.
2340 7.3. CoMP Future
2342 7.3.1. Mobile Industry Overall Goals
2344 [METIS] documents the fundamental challenges as well as overall
2345 technical goals of the 5G mobile and wireless system as the starting
2346 point. These future systems should support (at similar cost and
2347 energy consumption levels as today's system):
2349 o 1000 times higher mobile data volume per area
2351 o 10 times to 100 times higher typical user data rate
2353 o 10 times to 100 times higher number of connected devices
2355 o 10 times longer battery life for low power devices
2357 o 5 times reduced End-to-End (E2E) latency
2358 The current LTE networking system has E2E latency less than 20ms
2359 [LTE-Latency] which leads to around 5ms E2E latency for 5G networks.
2360 To fulfill these latency demands at similar cost will be challenging
2361 because as the system also requires 100x bandwidth and 100x connected
2362 devices, simply adding redundant bandwidth provisioning can no longer
2363 be an efficient solution.
2365 In addition to bandwidth provisioning, reserved critical flows should
2366 not be affected by other flows no matter the pressure of the network.
2367 Deterministic networking techniques in both layer-2 and layer-3 using
2368 IETF protocol solutions can be promising to serve these scenarios.
2370 7.3.2. CoMP Infrastructure Goals
2372 Inter-site CoMP is one of the key requirements for 5G and is also a
2373 near-term goal for the current 4.5G network architecture. Assuming
2374 network architecture remains unchanged (i.e. no Fronthaul network and
2375 data flow between eNB is via X2/eX2) we would like to see the
2376 following in the near future:
2378 o Unified protocols and delay-guaranteed forwarding network
2379 equipment that is capable of delivering deterministic latency
2380 services.
2382 o Unified management and protocols which take delay and timing into
2383 account.
2385 o Unified deterministic latency data model and signaling for
2386 resource reservation.
2388 7.4. CoMP Asks
2390 To fully utilize the power of CoMP, it requires:
2392 o Very tight absolute delay bound (100-500us) within 7-10 hops.
2394 o Standardized data plane with highly deterministic networking
2395 capability.
2397 o Standardized control plane to unify backhaul network elements with
2398 time-sensitive stream reservation signaling.
2400 In addition, a standardized deterministic latency data flow model
2401 that includes:
2403 o Network-aware constraints on the networking environment
2404 o Time-aware description of flow characteristics and network
2405 resources, which may not need to be bandwidth based
2407 o Application-aware description of deterministic latency services.
2409 8. Industrial M2M
2411 8.1. Use Case Description
2413 Industrial Automation in general refers to automation of
2414 manufacturing, quality control and material processing. In this
2415 "machine to machine" (M2M) use case we consider machine units in a
2416 plant floor which periodically exchange data with upstream or
2417 downstream machine modules and/or a supervisory controller within a
2418 local area network.
2420 The actors of M2M communication are Programmable Logic Controllers
2421 (PLCs). Communication between PLCs and between PLCs and the
2422 supervisory PLC (S-PLC) is achieved via critical control/data streams
2423 Figure 9.
2425 S (Sensor)
2426 \ +-----+
2427 PLC__ \.--. .--. ---| MES |
2428 \_( `. _( `./ +-----+
2429 A------( Local )-------------( L2 )
2430 ( Net ) ( Net ) +-------+
2431 /`--(___.-' `--(___.-' ----| S-PLC |
2432 S_/ / PLC .--. / +-------+
2433 A_/ \_( `.
2434 (Actuator) ( Local )
2435 ( Net )
2436 /`--(___.-'\
2437 / \ A
2438 S A
2440 Figure 9: Current Generic Industrial M2M Network Architecture
2442 This use case focuses on PLC-related communications; communication to
2443 Manufacturing-Execution-Systems (MESs) are not addressed.
2445 This use case covers only critical control/data streams; non-critical
2446 traffic between industrial automation applications (such as
2447 communication of state, configuration, set-up, and database
2448 communication) are adequately served by currently available
2449 prioritizing techniques. Such traffic can use up to 80% of the total
2450 bandwidth required. There is also a subset of non-time-critical
2451 traffic that must be reliable even though it is not time sensitive.
2453 In this use case the primary need for deterministic networking is to
2454 provide end-to-end delivery of M2M messages within specific timing
2455 constraints, for example in closed loop automation control. Today
2456 this level of determinism is provided by proprietary networking
2457 technologies. In addition, standard networking technologies are used
2458 to connect the local network to remote industrial automation sites,
2459 e.g. over an enterprise or metro network which also carries other
2460 types of traffic. Therefore, flows that should be forwarded with
2461 deterministic guarantees need to be sustained regardless of the
2462 amount of other flows in those networks.
2464 8.2. Industrial M2M Communication Today
2466 Today, proprietary networks fulfill the needed timing and
2467 availability for M2M networks.
2469 The network topologies used today by industrial automation are
2470 similar to those used by telecom networks: Daisy Chain, Ring, Hub and
2471 Spoke, and Comb (a subset of Daisy Chain).
2473 PLC-related control/data streams are transmitted periodically and
2474 carry either a pre-configured payload or a payload configured during
2475 runtime.
2477 Some industrial applications require time synchronization at the end
2478 nodes. For such time-coordinated PLCs, accuracy of 1 microsecond is
2479 required. Even in the case of "non-time-coordinated" PLCs time sync
2480 may be needed e.g. for timestamping of sensor data.
2482 Industrial network scenarios require advanced security solutions.
2483 Many of the current industrial production networks are physically
2484 separated. Preventing critical flows from be leaked outside a domain
2485 is handled today by filtering policies that are typically enforced in
2486 firewalls.
2488 8.2.1. Transport Parameters
2490 The Cycle Time defines the frequency of message(s) between industrial
2491 actors. The Cycle Time is application dependent, in the range of 1ms
2492 - 100ms for critical control/data streams.
2494 Because industrial applications assume deterministic transport for
2495 critical Control-Data-Stream parameters (instead of defining latency
2496 and delay variation parameters) it is sufficient to fulfill the upper
2497 bound of latency (maximum latency). The underlying networking
2498 infrastructure must ensure a maximum end-to-end delivery time of
2499 messages in the range of 100 microseconds to 50 milliseconds
2500 depending on the control loop application.
2502 The bandwidth requirements of control/data streams are usually
2503 calculated directly from the bytes-per-cycle parameter of the control
2504 loop. For PLC-to-PLC communication one can expect 2 - 32 streams
2505 with packet size in the range of 100 - 700 bytes. For S-PLC to PLCs
2506 the number of streams is higher - up to 256 streams. Usually no more
2507 than 20% of available bandwidth is used for critical control/data
2508 streams. In today's networks 1Gbps links are commonly used.
2510 Most PLC control loops are rather tolerant of packet loss, however
2511 critical control/data streams accept no more than 1 packet loss per
2512 consecutive communication cycle (i.e. if a packet gets lost in cycle
2513 "n", then the next cycle ("n+1") must be lossless). After two or
2514 more consecutive packet losses the network may be considered to be
2515 "down" by the Application.
2517 As network downtime may impact the whole production system the
2518 required network availability is rather high (99,999%).
2520 Based on the above parameters we expect that some form of redundancy
2521 will be required for M2M communications, however any individual
2522 solution depends on several parameters including cycle time, delivery
2523 time, etc.
2525 8.2.2. Stream Creation and Destruction
2527 In an industrial environment, critical control/data streams are
2528 created rather infrequently, on the order of ~10 times per day / week
2529 / month. Most of these critical control/data streams get created at
2530 machine startup, however flexibility is also needed during runtime,
2531 for example when adding or removing a machine. Going forward as
2532 production systems become more flexible, we expect a significant
2533 increase in the rate at which streams are created, changed and
2534 destroyed.
2536 8.3. Industrial M2M Future
2538 We would like to see a converged IP-standards-based network with
2539 deterministic properties that can satisfy the timing, security and
2540 reliability constraints described above. Today's proprietary
2541 networks could then be interfaced to such a network via gateways or,
2542 in the case of new installations, devices could be connected directly
2543 to the converged network.
2545 8.4. Industrial M2M Asks
2547 o Converged IP-based network
2549 o Deterministic behavior (bounded latency and jitter )
2551 o High availability (presumably through redundancy) (99.999 %)
2553 o Low message delivery time (100us - 50ms)
2555 o Low packet loss (burstless, 0.1-1 %)
2557 o Precise time synchronization accuracy (1us)
2559 o Security (e.g. prevent critical flows from being leaked between
2560 physically separated networks)
2562 9. Internet-based Applications
2564 9.1. Use Case Description
2566 There are many applications that communicate across the open Internet
2567 that could benefit from guaranteed delivery and bounded latency. The
2568 following are some representative examples.
2570 9.1.1. Media Content Delivery
2572 Media content delivery continues to be an important use of the
2573 Internet, yet users often experience poor quality audio and video due
2574 to the delay and jitter inherent in today's Internet.
2576 9.1.2. Online Gaming
2578 Online gaming is a significant part of the gaming market, however
2579 latency can degrade the end user experience. For example "First
2580 Person Shooter" (FPS) games are highly delay-sensitive.
2582 9.1.3. Virtual Reality
2584 Virtual reality (VR) has many commercial applications including real
2585 estate presentations, remote medical procedures, and so on. Low
2586 latency is critical to interacting with the virtual world because
2587 perceptual delays can cause motion sickness.
2589 9.2. Internet-Based Applications Today
2591 Internet service today is by definition "best effort", with no
2592 guarantees on delivery or bandwidth.
2594 9.3. Internet-Based Applications Future
2596 We imagine an Internet from which we will be able to play a video
2597 without glitches and play games without lag.
2599 For online gaming, the maximum round-trip delay can be 100ms and
2600 stricter for FPS gaming which can be 10-50ms. Transport delay is the
2601 dominate part with a 5-20ms budget.
2603 For VR, 1-10ms maximum delay is needed and total network budget is
2604 1-5ms if doing remote VR.
2606 Flow identification can be used for gaming and VR, i.e. it can
2607 recognize a critical flow and provide appropriate latency bounds.
2609 9.4. Internet-Based Applications Asks
2611 o Unified control and management protocols to handle time-critical
2612 data flow
2614 o Application-aware flow filtering mechanism to recognize the timing
2615 critical flow without doing 5-tuple matching
2617 o Unified control plane to provide low latency service on Layer-3
2618 without changing the data plane
2620 o OAM system and protocols which can help to provide E2E-delay
2621 sensitive service provisioning
2623 10. Use Case Common Elements
2625 Looking at the use cases collectively, the following common desires
2626 for the DetNet-based networks of the future emerge:
2628 o Open standards-based network (replace various proprietary
2629 networks, reduce cost, create multi-vendor market)
2631 o Centrally administered (though such administration may be
2632 distributed for scale and resiliency)
2634 o Integrates L2 (bridged) and L3 (routed) environments (independent
2635 of the Link layer, e.g. can be used with Ethernet, 6TiSCH, etc.)
2637 o Carries both deterministic and best-effort traffic (guaranteed
2638 end-to-end delivery of deterministic flows, deterministic flows
2639 isolated from each other and from best-effort traffic congestion,
2640 unused deterministic BW available to best-effort traffic)
2642 o Ability to add or remove systems from the network with minimal,
2643 bounded service interruption (applications include replacement of
2644 failed devices as well as plug and play)
2646 o Uses standardized data flow information models capable of
2647 expressing deterministic properties (models express device
2648 capabilities, flow properties. Protocols for pushing models from
2649 controller to devices, devices to controller)
2651 o Scalable size (long distances (many km) and short distances
2652 (within a single machine), many hops (radio repeaters, microwave
2653 links, fiber links...) and short hops (single machine))
2655 o Scalable timing parameters and accuracy (bounded latency,
2656 guaranteed worst case maximum, minimum. Low latency, e.g. control
2657 loops may be less than 1ms, but larger for wide area networks)
2659 o High availability (99.9999 percent up time requested, but may be
2660 up to twelve 9s)
2662 o Reliability, redundancy (lives at stake)
2664 o Security (from failures, attackers, misbehaving devices -
2665 sensitive to both packet content and arrival time)
2667 11. Acknowledgments
2669 11.1. Pro Audio
2671 This section was derived from draft-gunther-detnet-proaudio-req-01.
2673 The editors would like to acknowledge the help of the following
2674 individuals and the companies they represent:
2676 Jeff Koftinoff, Meyer Sound
2678 Jouni Korhonen, Associate Technical Director, Broadcom
2680 Pascal Thubert, CTAO, Cisco
2682 Kieran Tyrrell, Sienda New Media Technologies GmbH
2684 11.2. Utility Telecom
2686 This section was derived from draft-wetterwald-detnet-utilities-reqs-
2687 02.
2689 Faramarz Maghsoodlou, Ph. D. IoT Connected Industries and Energy
2690 Practice Cisco
2692 Pascal Thubert, CTAO Cisco
2694 11.3. Building Automation Systems
2696 This section was derived from draft-bas-usecase-detnet-00.
2698 11.4. Wireless for Industrial
2700 This section was derived from draft-thubert-6tisch-4detnet-01.
2702 This specification derives from the 6TiSCH architecture, which is the
2703 result of multiple interactions, in particular during the 6TiSCH
2704 (bi)Weekly Interim call, relayed through the 6TiSCH mailing list at
2705 the IETF.
2707 The authors wish to thank: Kris Pister, Thomas Watteyne, Xavier
2708 Vilajosana, Qin Wang, Tom Phinney, Robert Assimiti, Michael
2709 Richardson, Zhuo Chen, Malisa Vucinic, Alfredo Grieco, Martin Turon,
2710 Dominique Barthel, Elvis Vogli, Guillaume Gaillard, Herman Storey,
2711 Maria Rita Palattella, Nicola Accettura, Patrick Wetterwald, Pouria
2712 Zand, Raghuram Sudhaakar, and Shitanshu Shah for their participation
2713 and various contributions.
2715 11.5. Cellular Radio
2717 This section was derived from draft-korhonen-detnet-telreq-00.
2719 11.6. Industrial M2M
2721 The authors would like to thank Feng Chen and Marcel Kiessling for
2722 their comments and suggestions.
2724 11.7. Internet Applications and CoMP
2726 This section was derived from draft-zha-detnet-use-case-00.
2728 This document has benefited from reviews, suggestions, comments and
2729 proposed text provided by the following members, listed in
2730 alphabetical order: Jing Huang, Junru Lin, Lehong Niu and Oilver
2731 Huang.
2733 12. Informative References
2735 [ACE] IETF, "Authentication and Authorization for Constrained
2736 Environments", .
2739 [bacnetip]
2740 ASHRAE, "Annex J to ANSI/ASHRAE 135-1995 - BACnet/IP",
2741 January 1999.
2743 [CCAMP] IETF, "Common Control and Measurement Plane",
2744 .
2746 [CoMP] NGMN Alliance, "RAN EVOLUTION PROJECT COMP EVALUATION AND
2747 ENHANCEMENT", NGMN Alliance NGMN_RANEV_D3_CoMP_Evaluation_
2748 and_Enhancement_v2.0, March 2015,
2749 .
2752 [CONTENT_PROTECTION]
2753 Olsen, D., "1722a Content Protection", 2012,
2754 .
2757 [CPRI] CPRI Cooperation, "Common Public Radio Interface (CPRI);
2758 Interface Specification", CPRI Specification V6.1, July
2759 2014, .
2762 [DCI] Digital Cinema Initiatives, LLC, "DCI Specification,
2763 Version 1.2", 2012, .
2765 [DICE] IETF, "DTLS In Constrained Environments",
2766 .
2768 [EA12] Evans, P. and M. Annunziata, "Industrial Internet: Pushing
2769 the Boundaries of Minds and Machines", November 2012.
2771 [ESPN_DC2]
2772 Daley, D., "ESPN's DC2 Scales AVB Large", 2014,
2773 .
2776 [flnet] Japan Electrical Manufacturers' Association, "JEMA 1479 -
2777 English Edition", September 2012.
2779 [Fronthaul]
2780 Chen, D. and T. Mustala, "Ethernet Fronthaul
2781 Considerations", IEEE 1904.3, February 2015,
2782 .
2785 [HART] www.hartcomm.org, "Highway Addressable remote Transducer,
2786 a group of specifications for industrial process and
2787 control devices administered by the HART Foundation".
2789 [I-D.finn-detnet-architecture]
2790 Finn, N., Thubert, P., and M. Teener, "Deterministic
2791 Networking Architecture", draft-finn-detnet-
2792 architecture-03 (work in progress), March 2016.
2794 [I-D.finn-detnet-problem-statement]
2795 Finn, N. and P. Thubert, "Deterministic Networking Problem
2796 Statement", draft-finn-detnet-problem-statement-04 (work
2797 in progress), October 2015.
2799 [I-D.ietf-6tisch-6top-interface]
2800 Wang, Q. and X. Vilajosana, "6TiSCH Operation Sublayer
2801 (6top) Interface", draft-ietf-6tisch-6top-interface-04
2802 (work in progress), July 2015.
2804 [I-D.ietf-6tisch-architecture]
2805 Thubert, P., "An Architecture for IPv6 over the TSCH mode
2806 of IEEE 802.15.4", draft-ietf-6tisch-architecture-09 (work
2807 in progress), November 2015.
2809 [I-D.ietf-6tisch-coap]
2810 Sudhaakar, R. and P. Zand, "6TiSCH Resource Management and
2811 Interaction using CoAP", draft-ietf-6tisch-coap-03 (work
2812 in progress), March 2015.
2814 [I-D.ietf-6tisch-terminology]
2815 Palattella, M., Thubert, P., Watteyne, T., and Q. Wang,
2816 "Terminology in IPv6 over the TSCH mode of IEEE
2817 802.15.4e", draft-ietf-6tisch-terminology-06 (work in
2818 progress), November 2015.
2820 [I-D.ietf-ipv6-multilink-subnets]
2821 Thaler, D. and C. Huitema, "Multi-link Subnet Support in
2822 IPv6", draft-ietf-ipv6-multilink-subnets-00 (work in
2823 progress), July 2002.
2825 [I-D.ietf-roll-rpl-industrial-applicability]
2826 Phinney, T., Thubert, P., and R. Assimiti, "RPL
2827 applicability in industrial networks", draft-ietf-roll-
2828 rpl-industrial-applicability-02 (work in progress),
2829 October 2013.
2831 [I-D.ietf-tictoc-1588overmpls]
2832 Davari, S., Oren, A., Bhatia, M., Roberts, P., and L.
2833 Montini, "Transporting Timing messages over MPLS
2834 Networks", draft-ietf-tictoc-1588overmpls-07 (work in
2835 progress), October 2015.
2837 [I-D.kh-spring-ip-ran-use-case]
2838 Khasnabish, B., hu, f., and L. Contreras, "Segment Routing
2839 in IP RAN use case", draft-kh-spring-ip-ran-use-case-02
2840 (work in progress), November 2014.
2842 [I-D.mirsky-mpls-residence-time]
2843 Mirsky, G., Ruffini, S., Gray, E., Drake, J., Bryant, S.,
2844 and S. Vainshtein, "Residence Time Measurement in MPLS
2845 network", draft-mirsky-mpls-residence-time-07 (work in
2846 progress), July 2015.
2848 [I-D.svshah-tsvwg-deterministic-forwarding]
2849 Shah, S. and P. Thubert, "Deterministic Forwarding PHB",
2850 draft-svshah-tsvwg-deterministic-forwarding-04 (work in
2851 progress), August 2015.
2853 [I-D.thubert-6lowpan-backbone-router]
2854 Thubert, P., "6LoWPAN Backbone Router", draft-thubert-
2855 6lowpan-backbone-router-03 (work in progress), February
2856 2013.
2858 [I-D.wang-6tisch-6top-sublayer]
2859 Wang, Q. and X. Vilajosana, "6TiSCH Operation Sublayer
2860 (6top)", draft-wang-6tisch-6top-sublayer-04 (work in
2861 progress), November 2015.
2863 [IEC61850-90-12]
2864 TC57 WG10, IEC., "IEC 61850-90-12 TR: Communication
2865 networks and systems for power utility automation - Part
2866 90-12: Wide area network engineering guidelines", 2015.
2868 [IEC62439-3:2012]
2869 TC65, IEC., "IEC 62439-3: Industrial communication
2870 networks - High availability automation networks - Part 3:
2871 Parallel Redundancy Protocol (PRP) and High-availability
2872 Seamless Redundancy (HSR)", 2012.
2874 [IEEE1588]
2875 IEEE, "IEEE Standard for a Precision Clock Synchronization
2876 Protocol for Networked Measurement and Control Systems",
2877 IEEE Std 1588-2008, 2008,
2878 .
2881 [IEEE1722]
2882 IEEE, "1722-2011 - IEEE Standard for Layer 2 Transport
2883 Protocol for Time Sensitive Applications in a Bridged
2884 Local Area Network", IEEE Std 1722-2011, 2011,
2885 .
2888 [IEEE19043]
2889 IEEE Standards Association, "IEEE 1904.3 TF", IEEE 1904.3,
2890 2015, .
2892 [IEEE802.1TSNTG]
2893 IEEE Standards Association, "IEEE 802.1 Time-Sensitive
2894 Networks Task Group", March 2013,
2895 .
2897 [IEEE802154]
2898 IEEE standard for Information Technology, "IEEE std.
2899 802.15.4, Part. 15.4: Wireless Medium Access Control (MAC)
2900 and Physical Layer (PHY) Specifications for Low-Rate
2901 Wireless Personal Area Networks".
2903 [IEEE802154e]
2904 IEEE standard for Information Technology, "IEEE standard
2905 for Information Technology, IEEE std. 802.15.4, Part.
2906 15.4: Wireless Medium Access Control (MAC) and Physical
2907 Layer (PHY) Specifications for Low-Rate Wireless Personal
2908 Area Networks, June 2011 as amended by IEEE std.
2909 802.15.4e, Part. 15.4: Low-Rate Wireless Personal Area
2910 Networks (LR-WPANs) Amendment 1: MAC sublayer", April
2911 2012.
2913 [IEEE8021AS]
2914 IEEE, "Timing and Synchronizations (IEEE 802.1AS-2011)",
2915 IEEE 802.1AS-2001, 2011,
2916 .
2919 [IEEE8021CM]
2920 Farkas, J., "Time-Sensitive Networking for Fronthaul",
2921 Unapproved PAR, PAR for a New IEEE Standard;
2922 IEEE P802.1CM, April 2015,
2923 .
2926 [IEEE8021TSN]
2927 IEEE 802.1, "The charter of the TG is to provide the
2928 specifications that will allow time-synchronized low
2929 latency streaming services through 802 networks.", 2016,
2930 .
2932 [IETFDetNet]
2933 IETF, "Charter for IETF DetNet Working Group", 2015,
2934 .
2936 [ISA100] ISA/ANSI, "ISA100, Wireless Systems for Automation",
2937 .
2939 [ISA100.11a]
2940 ISA/ANSI, "Wireless Systems for Industrial Automation:
2941 Process Control and Related Applications - ISA100.11a-2011
2942 - IEC 62734", 2011, .
2945 [ISO7240-16]
2946 ISO, "ISO 7240-16:2007 Fire detection and alarm systems --
2947 Part 16: Sound system control and indicating equipment",
2948 2007, .
2951 [knx] KNX Association, "ISO/IEC 14543-3 - KNX", November 2006.
2953 [lontalk] ECHELON, "LonTalk(R) Protocol Specification Version 3.0",
2954 1994.
2956 [LTE-Latency]
2957 Johnston, S., "LTE Latency: How does it compare to other
2958 technologies", March 2014,
2959 .
2962 [MEF] MEF, "Mobile Backhaul Phase 2 Amendment 1 -- Small Cells",
2963 MEF 22.1.1, July 2014,
2964 .
2967 [METIS] METIS, "Scenarios, requirements and KPIs for 5G mobile and
2968 wireless system", ICT-317669-METIS/D1.1 ICT-
2969 317669-METIS/D1.1, April 2013, .
2972 [modbus] Modbus Organization, "MODBUS APPLICATION PROTOCOL
2973 SPECIFICATION V1.1b", December 2006.
2975 [net5G] Ericsson, "5G Radio Access, Challenges for 2020 and
2976 Beyond", Ericsson white paper wp-5g, June 2013,
2977 .
2979 [NGMN] NGMN Alliance, "5G White Paper", NGMN 5G White Paper v1.0,
2980 February 2015, .
2983 [PCE] IETF, "Path Computation Element",
2984 .
2986 [profibus]
2987 IEC, "IEC 61158 Type 3 - Profibus DP", January 2001.
2989 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
2990 Requirement Levels", BCP 14, RFC 2119,
2991 DOI 10.17487/RFC2119, March 1997,
2992 .
2994 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
2995 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
2996 December 1998, .
2998 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
2999 "Definition of the Differentiated Services Field (DS
3000 Field) in the IPv4 and IPv6 Headers", RFC 2474,
3001 DOI 10.17487/RFC2474, December 1998,
3002 .
3004 [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
3005 Label Switching Architecture", RFC 3031,
3006 DOI 10.17487/RFC3031, January 2001,
3007 .
3009 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
3010 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
3011 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
3012 .
3014 [RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation
3015 Metric for IP Performance Metrics (IPPM)", RFC 3393,
3016 DOI 10.17487/RFC3393, November 2002,
3017 .
3019 [RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between
3020 Information Models and Data Models", RFC 3444,
3021 DOI 10.17487/RFC3444, January 2003,
3022 .
3024 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
3025 RFC 3972, DOI 10.17487/RFC3972, March 2005,
3026 .
3028 [RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
3029 Edge-to-Edge (PWE3) Architecture", RFC 3985,
3030 DOI 10.17487/RFC3985, March 2005,
3031 .
3033 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
3034 Architecture", RFC 4291, DOI 10.17487/RFC4291, February
3035 2006, .
3037 [RFC4553] Vainshtein, A., Ed. and YJ. Stein, Ed., "Structure-
3038 Agnostic Time Division Multiplexing (TDM) over Packet
3039 (SAToP)", RFC 4553, DOI 10.17487/RFC4553, June 2006,
3040 .
3042 [RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903,
3043 DOI 10.17487/RFC4903, June 2007,
3044 .
3046 [RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6
3047 over Low-Power Wireless Personal Area Networks (6LoWPANs):
3048 Overview, Assumptions, Problem Statement, and Goals",
3049 RFC 4919, DOI 10.17487/RFC4919, August 2007,
3050 .
3052 [RFC5086] Vainshtein, A., Ed., Sasson, I., Metz, E., Frost, T., and
3053 P. Pate, "Structure-Aware Time Division Multiplexed (TDM)
3054 Circuit Emulation Service over Packet Switched Network
3055 (CESoPSN)", RFC 5086, DOI 10.17487/RFC5086, December 2007,
3056 .
3058 [RFC5087] Stein, Y(J)., Shashoua, R., Insler, R., and M. Anavi,
3059 "Time Division Multiplexing over IP (TDMoIP)", RFC 5087,
3060 DOI 10.17487/RFC5087, December 2007,
3061 .
3063 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
3064 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
3065 DOI 10.17487/RFC6282, September 2011,
3066 .
3068 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
3069 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
3070 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
3071 Low-Power and Lossy Networks", RFC 6550,
3072 DOI 10.17487/RFC6550, March 2012,
3073 .
3075 [RFC6551] Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N.,
3076 and D. Barthel, "Routing Metrics Used for Path Calculation
3077 in Low-Power and Lossy Networks", RFC 6551,
3078 DOI 10.17487/RFC6551, March 2012,
3079 .
3081 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
3082 Bormann, "Neighbor Discovery Optimization for IPv6 over
3083 Low-Power Wireless Personal Area Networks (6LoWPANs)",
3084 RFC 6775, DOI 10.17487/RFC6775, November 2012,
3085 .
3087 [RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using
3088 IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the
3089 Internet of Things (IoT): Problem Statement", RFC 7554,
3090 DOI 10.17487/RFC7554, May 2015,
3091 .
3093 [SRP_LATENCY]
3094 Gunther, C., "Specifying SRP Latency", 2014,
3095 .
3098 [STUDIO_IP]
3099 Mace, G., "IP Networked Studio Infrastructure for
3100 Synchronized & Real-Time Multimedia Transmissions", 2007,
3101 .
3104 [SyncE] ITU-T, "G.8261 : Timing and synchronization aspects in
3105 packet networks", Recommendation G.8261, August 2013,
3106 .
3108 [TEAS] IETF, "Traffic Engineering Architecture and Signaling",
3109 .
3111 [TS23401] 3GPP, "General Packet Radio Service (GPRS) enhancements
3112 for Evolved Universal Terrestrial Radio Access Network
3113 (E-UTRAN) access", 3GPP TS 23.401 10.10.0, March 2013.
3115 [TS25104] 3GPP, "Base Station (BS) radio transmission and reception
3116 (FDD)", 3GPP TS 25.104 3.14.0, March 2007.
3118 [TS36104] 3GPP, "Evolved Universal Terrestrial Radio Access
3119 (E-UTRA); Base Station (BS) radio transmission and
3120 reception", 3GPP TS 36.104 10.11.0, July 2013.
3122 [TS36133] 3GPP, "Evolved Universal Terrestrial Radio Access
3123 (E-UTRA); Requirements for support of radio resource
3124 management", 3GPP TS 36.133 12.7.0, April 2015.
3126 [TS36211] 3GPP, "Evolved Universal Terrestrial Radio Access
3127 (E-UTRA); Physical channels and modulation", 3GPP
3128 TS 36.211 10.7.0, March 2013.
3130 [TS36300] 3GPP, "Evolved Universal Terrestrial Radio Access (E-UTRA)
3131 and Evolved Universal Terrestrial Radio Access Network
3132 (E-UTRAN); Overall description; Stage 2", 3GPP TS 36.300
3133 10.11.0, September 2013.
3135 [TSNTG] IEEE Standards Association, "IEEE 802.1 Time-Sensitive
3136 Networks Task Group", 2013,
3137 .
3139 [UHD-video]
3140 Holub, P., "Ultra-High Definition Videos and Their
3141 Applications over the Network", The 7th International
3142 Symposium on VICTORIES Project PetrHolub_presentation,
3143 October 2014, .
3146 [WirelessHART]
3147 www.hartcomm.org, "Industrial Communication Networks -
3148 Wireless Communication Network and Communication Profiles
3149 - WirelessHART - IEC 62591", 2010.
3151 Authors' Addresses
3152 Ethan Grossman (editor)
3153 Dolby Laboratories, Inc.
3154 1275 Market Street
3155 San Francisco, CA 94103
3156 USA
3158 Phone: +1 415 645 4726
3159 Email: ethan.grossman@dolby.com
3160 URI: http://www.dolby.com
3162 Craig Gunther
3163 Harman International
3164 10653 South River Front Parkway
3165 South Jordan, UT 84095
3166 USA
3168 Phone: +1 801 568-7675
3169 Email: craig.gunther@harman.com
3170 URI: http://www.harman.com
3172 Pascal Thubert
3173 Cisco Systems, Inc
3174 Building D
3175 45 Allee des Ormes - BP1200
3176 MOUGINS - Sophia Antipolis 06254
3177 FRANCE
3179 Phone: +33 497 23 26 34
3180 Email: pthubert@cisco.com
3182 Patrick Wetterwald
3183 Cisco Systems
3184 45 Allees des Ormes
3185 Mougins 06250
3186 FRANCE
3188 Phone: +33 4 97 23 26 36
3189 Email: pwetterw@cisco.com
3190 Jean Raymond
3191 Hydro-Quebec
3192 1500 University
3193 Montreal H3A3S7
3194 Canada
3196 Phone: +1 514 840 3000
3197 Email: raymond.jean@hydro.qc.ca
3199 Jouni Korhonen
3200 Broadcom Corporation
3201 3151 Zanker Road
3202 San Jose, CA 95134
3203 USA
3205 Email: jouni.nospam@gmail.com
3207 Yu Kaneko
3208 Toshiba
3209 1 Komukai-Toshiba-cho, Saiwai-ku, Kasasaki-shi
3210 Kanagawa, Japan
3212 Email: yu1.kaneko@toshiba.co.jp
3214 Subir Das
3215 Applied Communication Sciences
3216 150 Mount Airy Road, Basking Ridge
3217 New Jersey, 07920, USA
3219 Email: sdas@appcomsci.com
3221 Yiyong Zha
3222 Huawei Technologies
3224 Email: zhayiyong@huawei.com
3226 Balazs Varga
3227 Ericsson
3228 Konyves Kalman krt. 11/B
3229 Budapest 1097
3230 Hungary
3232 Email: balazs.a.varga@ericsson.com
3233 Janos Farkas
3234 Ericsson
3235 Konyves Kalman krt. 11/B
3236 Budapest 1097
3237 Hungary
3239 Email: janos.farkas@ericsson.com
3241 Franz-Josef Goetz
3242 Siemens
3243 Gleiwitzerstr. 555
3244 Nurnberg 90475
3245 Germany
3247 Email: franz-josef.goetz@siemens.com
3249 Juergen Schmitt
3250 Siemens
3251 Gleiwitzerstr. 555
3252 Nurnberg 90475
3253 Germany
3255 Email: juergen.jues.schmitt@siemens.com