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+Internet Engineering Task Force (IETF) E. Grossman, Ed.
+Request for Comments: 8578 DOLBY
+Category: Informational May 2019
+ISSN: 2070-1721
+
+
+ Deterministic Networking Use Cases
+
+Abstract
+
+ This document presents use cases for diverse industries that have in
+ common a need for "deterministic flows". "Deterministic" in this
+ context means that such flows provide guaranteed bandwidth, bounded
+ latency, and other properties germane to the transport of time-
+ sensitive data. These use cases differ notably in their network
+ topologies and specific desired behavior, providing as a group broad
+ industry context for Deterministic Networking (DetNet). For each use
+ case, this document will identify the use case, identify
+ representative solutions used today, and describe potential
+ improvements that DetNet can enable.
+
+Status of This Memo
+
+ This document is not an Internet Standards Track specification; it is
+ published for informational purposes.
+
+ This document is a product of the Internet Engineering Task Force
+ (IETF). It represents the consensus of the IETF community. It has
+ received public review and has been approved for publication by the
+ Internet Engineering Steering Group (IESG). Not all documents
+ approved by the IESG are candidates for any level of Internet
+ Standard; see Section 2 of RFC 7841.
+
+ Information about the current status of this document, any errata,
+ and how to provide feedback on it may be obtained at
+ https://www.rfc-editor.org/info/rfc8578.
+
+
+
+
+
+
+
+
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+
+
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+
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+Grossman Informational [Page 1]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+Copyright Notice
+
+ Copyright (c) 2019 IETF Trust and the persons identified as the
+ document authors. All rights reserved.
+
+ This document is subject to BCP 78 and the IETF Trust's Legal
+ Provisions Relating to IETF Documents
+ (https://trustee.ietf.org/license-info) in effect on the date of
+ publication of this document. Please review these documents
+ carefully, as they describe your rights and restrictions with respect
+ to this document. Code Components extracted from this document must
+ include Simplified BSD License text as described in Section 4.e of
+ the Trust Legal Provisions and are provided without warranty as
+ described in the Simplified BSD License.
+
+Table of Contents
+
+ 1. Introduction ....................................................6
+ 2. Pro Audio and Video .............................................7
+ 2.1. Use Case Description .......................................7
+ 2.1.1. Uninterrupted Stream Playback .......................8
+ 2.1.2. Synchronized Stream Playback ........................9
+ 2.1.3. Sound Reinforcement .................................9
+ 2.1.4. Secure Transmission ................................10
+ 2.1.4.1. Safety ....................................10
+ 2.2. Pro Audio Today ...........................................10
+ 2.3. Pro Audio in the Future ...................................10
+ 2.3.1. Layer 3 Interconnecting Layer 2 Islands ............10
+ 2.3.2. High-Reliability Stream Paths ......................11
+ 2.3.3. Integration of Reserved Streams into IT Networks ...11
+ 2.3.4. Use of Unused Reservations by Best-Effort Traffic ..11
+ 2.3.5. Traffic Segregation ................................11
+ 2.3.5.1. Packet-Forwarding Rules, VLANs,
+ and Subnets ...............................12
+ 2.3.5.2. Multicast Addressing (IPv4 and IPv6) ......12
+ 2.3.6. Latency Optimization by a Central Controller .......12
+ 2.3.7. Reduced Device Costs due to Reduced Buffer Memory ..13
+ 2.4. Pro Audio Requests to the IETF ............................13
+ 3. Electrical Utilities ...........................................14
+ 3.1. Use Case Description ......................................14
+ 3.1.1. Transmission Use Cases .............................14
+ 3.1.1.1. Protection ................................14
+ 3.1.1.2. Intra-substation Process Bus
+ Communications ............................21
+ 3.1.1.3. Wide-Area Monitoring and Control Systems ..23
+ 3.1.1.4. WAN Engineering Guidelines
+ Requirement Classification ................25
+
+
+
+
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+ 3.1.2. Generation Use Case ................................26
+ 3.1.2.1. Control of the Generated Power ............26
+ 3.1.2.2. Control of the Generation Infrastructure ..27
+ 3.1.3. Distribution Use Case ..............................32
+ 3.1.3.1. Fault Location, Isolation, and
+ Service Restoration (FLISR) ...............32
+ 3.2. Electrical Utilities Today ................................33
+ 3.2.1. Current Security Practices and Their Limitations ...34
+ 3.3. Electrical Utilities in the Future ........................35
+ 3.3.1. Migration to Packet-Switched Networks ..............36
+ 3.3.2. Telecommunications Trends ..........................37
+ 3.3.2.1. General Telecommunications Requirements ...37
+ 3.3.2.2. Specific Network Topologies of
+ Smart-Grid Applications ...................38
+ 3.3.2.3. Precision Time Protocol ...................38
+ 3.3.3. Security Trends in Utility Networks ................39
+ 3.4. Electrical Utilities Requests to the IETF .................41
+ 4. Building Automation Systems (BASs) .............................41
+ 4.1. Use Case Description ......................................41
+ 4.2. BASs Today ................................................42
+ 4.2.1. BAS Architecture ...................................42
+ 4.2.2. BAS Deployment Model ...............................44
+ 4.2.3. Use Cases for Field Networks .......................45
+ 4.2.3.1. Environmental Monitoring ..................45
+ 4.2.3.2. Fire Detection ............................46
+ 4.2.3.3. Feedback Control ..........................46
+ 4.2.4. BAS Security Considerations ........................46
+ 4.3. BASs in the Future ........................................46
+ 4.4. BAS Requests to the IETF ..................................47
+ 5. Wireless for Industrial Applications ...........................47
+ 5.1. Use Case Description ......................................47
+ 5.1.1. Network Convergence Using 6TiSCH ...................48
+ 5.1.2. Common Protocol Development for 6TiSCH .............48
+ 5.2. Wireless Industrial Today .................................49
+ 5.3. Wireless Industrial in the Future .........................49
+ 5.3.1. Unified Wireless Networks and Management ...........49
+ 5.3.1.1. PCE and 6TiSCH ARQ Retries ................51
+ 5.3.2. Schedule Management by a PCE .......................52
+ 5.3.2.1. PCE Commands and 6TiSCH CoAP Requests .....52
+ 5.3.2.2. 6TiSCH IP Interface .......................54
+ 5.3.3. 6TiSCH Security Considerations .....................54
+ 5.4. Wireless Industrial Requests to the IETF ..................54
+
+
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+
+ 6. Cellular Radio .................................................54
+ 6.1. Use Case Description ......................................54
+ 6.1.1. Network Architecture ...............................54
+ 6.1.2. Delay Constraints ..................................55
+ 6.1.3. Time-Synchronization Constraints ...................57
+ 6.1.4. Transport-Loss Constraints .........................59
+ 6.1.5. Cellular Radio Network Security Considerations .....60
+ 6.2. Cellular Radio Networks Today .............................60
+ 6.2.1. Fronthaul ..........................................60
+ 6.2.2. Midhaul and Backhaul ...............................60
+ 6.3. Cellular Radio Networks in the Future .....................61
+ 6.4. Cellular Radio Networks Requests to the IETF ..............64
+ 7. Industrial Machine to Machine (M2M) ............................64
+ 7.1. Use Case Description ......................................64
+ 7.2. Industrial M2M Communications Today .......................66
+ 7.2.1. Transport Parameters ...............................66
+ 7.2.2. Stream Creation and Destruction ....................67
+ 7.3. Industrial M2M in the Future ..............................67
+ 7.4. Industrial M2M Requests to the IETF .......................67
+ 8. Mining Industry ................................................68
+ 8.1. Use Case Description ......................................68
+ 8.2. Mining Industry Today .....................................68
+ 8.3. Mining Industry in the Future .............................69
+ 8.4. Mining Industry Requests to the IETF ......................70
+ 9. Private Blockchain .............................................70
+ 9.1. Use Case Description ......................................70
+ 9.1.1. Blockchain Operation ...............................71
+ 9.1.2. Blockchain Network Architecture ....................71
+ 9.1.3. Blockchain Security Considerations .................72
+ 9.2. Private Blockchain Today ..................................72
+ 9.3. Private Blockchain in the Future ..........................72
+ 9.4. Private Blockchain Requests to the IETF ...................72
+ 10. Network Slicing ...............................................73
+ 10.1. Use Case Description .....................................73
+ 10.2. DetNet Applied to Network Slicing ........................73
+ 10.2.1. Resource Isolation across Slices ..................73
+ 10.2.2. Deterministic Services within Slices ..............74
+ 10.3. A Network Slicing Use Case Example - 5G Bearer Network ...74
+ 10.4. Non-5G Applications of Network Slicing ...................75
+ 10.5. Limitations of DetNet in Network Slicing .................75
+ 10.6. Network Slicing Today and in the Future ..................75
+ 10.7. Network Slicing Requests to the IETF .....................75
+ 11. Use Case Common Themes ........................................76
+ 11.1. Unified, Standards-Based Networks ........................76
+ 11.1.1. Extensions to Ethernet ............................76
+ 11.1.2. Centrally Administered Networks ...................76
+ 11.1.3. Standardized Data-Flow Information Models .........76
+
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+ 11.1.4. Layer 2 and Layer 3 Integration ...................76
+ 11.1.5. IPv4 Considerations ...............................76
+ 11.1.6. Guaranteed End-to-End Delivery ....................77
+ 11.1.7. Replacement for Multiple Proprietary
+ Deterministic Networks ............................77
+ 11.1.8. Mix of Deterministic and Best-Effort Traffic ......77
+ 11.1.9. Unused Reserved Bandwidth to Be Available
+ to Best-Effort Traffic ............................77
+ 11.1.10. Lower-Cost, Multi-Vendor Solutions ...............77
+ 11.2. Scalable Size ............................................78
+ 11.2.1. Scalable Number of Flows ..........................78
+ 11.3. Scalable Timing Parameters and Accuracy ..................78
+ 11.3.1. Bounded Latency ...................................78
+ 11.3.2. Low Latency .......................................78
+ 11.3.3. Bounded Jitter (Latency Variation) ................79
+ 11.3.4. Symmetrical Path Delays ...........................79
+ 11.4. High Reliability and Availability ........................79
+ 11.5. Security .................................................79
+ 11.6. Deterministic Flows ......................................79
+ 12. Security Considerations .......................................80
+ 13. IANA Considerations ...........................................80
+ 14. Informative References ........................................80
+ Appendix A. Use Cases Explicitly Out of Scope for DetNet ..........90
+ A.1. DetNet Scope Limitations ...................................90
+ A.2. Internet-Based Applications ................................90
+ A.2.1. Use Case Description ...................................91
+ A.2.1.1. Media Content Delivery .............................91
+ A.2.1.2. Online Gaming ......................................91
+ A.2.1.3. Virtual Reality ....................................91
+ A.2.2. Internet-Based Applications Today ......................91
+ A.2.3. Internet-Based Applications in the Future ..............91
+ A.2.4. Internet-Based Applications Requests to the IETF .......92
+ A.3. Pro Audio and Video - Digital Rights Management (DRM) ......92
+ A.4. Pro Audio and Video - Link Aggregation .....................92
+ A.5. Pro Audio and Video - Deterministic Time to Establish
+ Streaming ..................................................93
+ Acknowledgments ...................................................93
+ Contributors ......................................................95
+ Author's Address ..................................................97
+
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+Grossman Informational [Page 5]
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+RFC 8578 DetNet Use Cases May 2019
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+
+1. Introduction
+
+ This memo documents use cases for diverse industries that require
+ deterministic flows over multi-hop paths. Deterministic Networking
+ (DetNet) flows can be established from either a Layer 2 or Layer 3
+ (IP) interface, and such flows can coexist on an IP network with
+ best-effort traffic. DetNet also provides for highly reliable flows
+ through provision for redundant paths.
+
+ The DetNet use cases explicitly do not suggest any specific design
+ for DetNet architecture or protocols; these are topics for other
+ DetNet documents.
+
+ The DetNet use cases, as originally submitted, explicitly were not
+ considered by the DetNet Working Group (WG) to be concrete
+ requirements. The DetNet WG and Design Team considered these use
+ cases, identifying which of their elements could be feasibly
+ implemented within the charter of DetNet; as a result, certain
+ originally submitted use cases (or elements thereof) were moved to
+ Appendix A ("Use Cases Explicitly Out of Scope for DetNet") of this
+ document.
+
+ This document provides context regarding DetNet design decisions. It
+ also serves a long-lived purpose of helping those learning (or new
+ to) DetNet understand the types of applications that can be supported
+ by DetNet. It also allows those WG contributors who are users to
+ ensure that their concerns are addressed by the WG; for them, this
+ document (1) covers their contributions and (2) provides a long-term
+ reference regarding the problems that they expect will be served by
+ the technology, in terms of the short-term deliverables and also as
+ the technology evolves in the future.
+
+ This document has served as a "yardstick" against which proposed
+ DetNet designs can be measured, answering the question "To what
+ extent does a proposed design satisfy these various use cases?"
+
+ The industries covered by the use cases in this document are
+
+ o professional audio and video (Section 2)
+
+ o electrical utilities (Section 3)
+
+ o building automation systems (BASs) (Section 4)
+
+ o wireless for industrial applications (Section 5)
+
+ o cellular radio (Section 6)
+
+
+
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+RFC 8578 DetNet Use Cases May 2019
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+ o industrial machine to machine (M2M) (Section 7)
+
+ o mining (Section 8)
+
+ o private blockchain (Section 9)
+
+ o network slicing (Section 10)
+
+ For each use case, the following questions are answered:
+
+ o What is the use case?
+
+ o How is it addressed today?
+
+ o How should it be addressed in the future?
+
+ o What should the IETF deliver to enable this use case?
+
+ The level of detail in each use case is intended to be sufficient to
+ express the relevant elements of the use case but no more than that.
+
+ DetNet does not directly address clock distribution or time
+ synchronization; these are considered to be part of the overall
+ design and implementation of a time-sensitive network, using existing
+ (or future) time-specific protocols (such as [IEEE-8021AS] and/or
+ [RFC5905]).
+
+ Section 11 enumerates the set of common properties implied by these
+ use cases.
+
+2. Pro Audio and Video
+
+2.1. Use Case Description
+
+ The professional audio and video industry ("ProAV") includes:
+
+ o Music and film content creation
+
+ o Broadcast
+
+ o Cinema
+
+ o Live sound
+
+ o Public address, media, and emergency systems at large venues
+ (e.g., airports, stadiums, churches, theme parks)
+
+
+
+
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+ These industries have already transitioned audio and video signals
+ from analog to digital. However, the digital interconnect systems
+ remain primarily point to point, with a single signal or a small
+ number of signals per link, interconnected with purpose-built
+ hardware.
+
+ These industries are now transitioning to packet-based
+ infrastructures to reduce cost, increase routing flexibility, and
+ integrate with existing IT infrastructures.
+
+ Today, ProAV applications have no way to establish deterministic
+ flows from a standards-based Layer 3 (IP) interface; this is a
+ fundamental limitation of the use cases described here. Today,
+ deterministic flows can be created within standards-based Layer 2
+ LANs (e.g., using IEEE 802.1 TSN ("TSN" stands for "Time-Sensitive
+ Networking")); however, these flows are not routable via IP and thus
+ are not effective for distribution over wider areas (for example,
+ broadcast events that span wide geographical areas).
+
+ It would be highly desirable if such flows could be routed over the
+ open Internet; however, solutions of more-limited scope (e.g.,
+ enterprise networks) would still provide substantial improvements.
+
+ The following sections describe specific ProAV use cases.
+
+2.1.1. Uninterrupted Stream Playback
+
+ Transmitting audio and video streams for live playback is unlike
+ common file transfer in that uninterrupted stream playback in the
+ presence of network errors cannot be achieved by retrying the
+ transmission; by the time the missing or corrupt packet has been
+ identified, it is too late to execute a retry operation. Buffering
+ can be used to provide enough delay to allow time for one or more
+ retries; however, this is not an effective solution in applications
+ where large delays (latencies) are not acceptable (as discussed
+ below).
+
+ Streams with guaranteed bandwidth can eliminate congestion on the
+ network as a cause of transmission errors that would lead to playback
+ interruption. The use of redundant paths can further mitigate
+ transmission errors and thereby provide greater stream reliability.
+
+ Additional techniques, such as Forward Error Correction (FEC), can
+ also be used to improve stream reliability.
+
+
+
+
+
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+2.1.2. Synchronized Stream Playback
+
+ Latency in this context is the time between when a signal is
+ initially sent over a stream and when it is received. A common
+ example in ProAV is time-synchronizing audio and video when they take
+ separate paths through the playback system. In this case, the
+ latency of both the audio stream and the video stream must be bounded
+ and consistent if the sound is to remain matched to the movement in
+ the video. A common tolerance for audio/video synchronization is one
+ National Television System Committee (NTSC) video frame (about
+ 33 ms); to maintain the audience's perception of correct lip-sync,
+ the latency needs to be consistent within some reasonable tolerance
+ -- for example, 10%.
+
+ A common architecture for synchronizing multiple streams that have
+ different paths through the network (and thus potentially different
+ latencies) enables measurement of the latency of each path and has
+ the data sinks (for example, speakers) delay (buffer) all packets on
+ all but the slowest path. Each packet of each stream is assigned a
+ presentation time that is based on the longest required delay. This
+ implies that all sinks must maintain a common time reference of
+ sufficient accuracy, which can be achieved by various techniques.
+
+ This type of architecture is commonly implemented using a central
+ controller that determines path delays and arbitrates buffering
+ delays.
+
+2.1.3. Sound Reinforcement
+
+ Consider the latency (delay) between the time when a person speaks
+ into a microphone and when their voice emerges from the speaker. If
+ this delay is longer than about 10-15 ms, it is noticeable and can
+ make a sound-reinforcement system unusable (see slide 6 of
+ [SRP_LATENCY]). (If you have ever tried to speak in the presence of
+ a delayed echo of your voice, you might be familiar with this
+ experience.)
+
+ Note that the 15 ms latency bound includes all parts of the signal
+ path -- not just the network -- so the network latency must be
+ significantly less than 15 ms.
+
+ In some cases, local performers must perform in synchrony with a
+ remote broadcast. In such cases, the latencies of the broadcast
+ stream and the local performer must be adjusted to match each other,
+ with a worst case of one video frame (33 ms for NTSC video).
+
+
+
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+ In cases where audio phase is a consideration -- for example,
+ beam-forming using multiple speakers -- latency can be in the 10 us
+ range (one audio sample at 96 kHz).
+
+2.1.4. Secure Transmission
+
+2.1.4.1. Safety
+
+ Professional audio systems can include amplifiers that are capable of
+ generating hundreds or thousands of watts of audio power. If used
+ incorrectly, such amplifiers can cause hearing damage to those in the
+ vicinity. Apart from the usual care required by the systems
+ operators to prevent such incidents, the network traffic that
+ controls these devices must be secured (as with any sensitive
+ application traffic).
+
+2.2. Pro Audio Today
+
+ Some proprietary systems have been created that enable deterministic
+ streams at Layer 3; however, they are "engineered networks" that
+ require careful configuration to operate and often require that the
+ system be over-provisioned. Also, it is implied that all devices on
+ the network voluntarily play by the rules of that network. To enable
+ these industries to successfully transition to an interoperable
+ multi-vendor packet-based infrastructure requires effective open
+ standards. Establishing relevant IETF standards is a crucial factor.
+
+2.3. Pro Audio in the Future
+
+2.3.1. Layer 3 Interconnecting Layer 2 Islands
+
+ It would be valuable to enable IP to connect multiple Layer 2 LANs.
+
+ As an example, ESPN constructed a state-of-the-art 194,000 sq. ft.,
+ $125-million broadcast studio called "Digital Center 2" (DC2). The
+ DC2 network is capable of handling 46 Tbps of throughput with 60,000
+ simultaneous signals. Inside the facility are 1,100 miles of fiber
+ feeding four audio control rooms (see [ESPN_DC2]).
+
+ In designing DC2, they replaced as much point-to-point technology as
+ they could with packet-based technology. They constructed seven
+ individual studios using Layer 2 LANs (using IEEE 802.1 TSN) that
+ were entirely effective at routing audio within the LANs. However,
+ to interconnect these Layer 2 LAN islands together, they ended up
+ using dedicated paths in a custom SDN (Software-Defined Networking)
+ router because there is no standards-based routing solution
+ available.
+
+
+
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+
+2.3.2. High-Reliability Stream Paths
+
+ On-air and other live media streams are often backed up with
+ redundant links that seamlessly act to deliver the content when the
+ primary link fails for any reason. In point-to-point systems, this
+ redundancy is provided by an additional point-to-point link; the
+ analogous requirement in a packet-based system is to provide an
+ alternate path through the network such that no individual link can
+ bring down the system.
+
+2.3.3. Integration of Reserved Streams into IT Networks
+
+ A commonly cited goal of moving to a packet-based media
+ infrastructure is that costs can be reduced by using off-the-shelf,
+ commodity-network hardware. In addition, economy of scale can be
+ realized by combining media infrastructure with IT infrastructure.
+ In keeping with these goals, stream-reservation technology should be
+ compatible with existing protocols and should not compromise the use
+ of the network for best-effort (non-time-sensitive) traffic.
+
+2.3.4. Use of Unused Reservations by Best-Effort Traffic
+
+ In cases where stream bandwidth is reserved but not currently used
+ (or is underutilized), that bandwidth must be available to
+ best-effort (i.e., non-time-sensitive) traffic. For example, a
+ single stream may be "nailed up" (reserved) for specific media
+ content that needs to be presented at different times of the day,
+ ensuring timely delivery of that content, yet in between those times
+ the full bandwidth of the network can be utilized for best-effort
+ tasks such as file transfers.
+
+ This also addresses a concern of IT network administrators that are
+ considering adding reserved-bandwidth traffic to their networks that
+ "users will reserve large quantities of bandwidth and then never
+ unreserve it even though they are not using it, and soon the network
+ will have no bandwidth left."
+
+2.3.5. Traffic Segregation
+
+ Sink devices may be low-cost devices with limited processing power.
+ In order to not overwhelm the CPUs in these devices, it is important
+ to limit the amount of traffic that these devices must process.
+
+ As an example, consider the use of individual seat speakers in a
+ cinema. These speakers are typically required to be cost reduced,
+ since the quantities in a single theater can reach hundreds of seats.
+ Discovery protocols alone in a 1,000-seat theater can generate enough
+ broadcast traffic to overwhelm a low-powered CPU. Thus, an
+
+
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+
+ installation like this will benefit greatly from some type of traffic
+ segregation that can define groups of seats to reduce traffic within
+ each group. All seats in the theater must still be able to
+ communicate with a central controller.
+
+ There are many techniques that can be used to support this feature,
+ including (but not limited to) the following examples.
+
+2.3.5.1. Packet-Forwarding Rules, VLANs, and Subnets
+
+ Packet-forwarding rules can be used to eliminate some extraneous
+ streaming traffic from reaching potentially low-powered sink devices;
+ however, there may be other types of broadcast traffic that should be
+ eliminated via other means -- for example, VLANs or IP subnets.
+
+2.3.5.2. Multicast Addressing (IPv4 and IPv6)
+
+ Multicast addressing is commonly used to keep bandwidth utilization
+ of shared links to a minimum.
+
+ Because Layer 2 bridges by design forward Media Access Control (MAC)
+ addresses, it is important that a multicast MAC address only be
+ associated with one stream. This will prevent reservations from
+ forwarding packets from one stream down a path that has no interested
+ sinks simply because there is another stream on that same path that
+ shares the same multicast MAC address.
+
+ In other words, since each multicast MAC address can represent 32
+ different IPv4 multicast addresses, there must be a process in place
+ to make sure that any given multicast MAC address is only associated
+ with exactly one IPv4 multicast address. Requiring the use of IPv6
+ addresses could help in this regard, due to the much larger address
+ range of IPv6; however, due to the continued prevalence of IPv4
+ installations, solutions that are effective for IPv4 installations
+ would be practical in many more use cases.
+
+2.3.6. Latency Optimization by a Central Controller
+
+ A central network controller might also perform optimizations based
+ on the individual path delays; for example, sinks that are closer to
+ the source can inform the controller that they can accept greater
+ latency, since they will be buffering packets to match presentation
+ times of sinks that are farther away. The controller might then move
+ a stream reservation on a short path to a longer path in order to
+ free up bandwidth for other critical streams on that short path. See
+ slides 3-5 of [SRP_LATENCY].
+
+
+
+
+
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+
+
+ Additional optimization can be achieved in cases where sinks have
+ differing latency requirements; for example, at a live outdoor
+ concert, the speaker sinks have stricter latency requirements than
+ the recording-hardware sinks. See slide 7 of [SRP_LATENCY].
+
+2.3.7. Reduced Device Costs due to Reduced Buffer Memory
+
+ Device costs can be reduced in a system with guaranteed reservations
+ with a small bounded latency due to the reduced requirements for
+ buffering (i.e., memory) on sink devices. For example, a theme park
+ might broadcast a live event across the globe via a Layer 3 protocol.
+ In such cases, the size of the buffers required is defined by the
+ worst-case latency and jitter values of the worst-case segment of the
+ end-to-end network path. For example, on today's open Internet, the
+ latency is typically unacceptable for audio and video streaming
+ without many seconds of buffering. In such scenarios, a single
+ gateway device at the local network that receives the feed from the
+ remote site would provide the expensive buffering required to mask
+ the latency and jitter issues associated with long-distance delivery.
+ Sink devices in the local location would have no additional buffering
+ requirements, and thus no additional costs, beyond those required for
+ delivery of local content. The sink device would be receiving
+ packets identical to those sent by the source and would be unaware of
+ any latency or jitter issues along the path.
+
+2.4. Pro Audio Requests to the IETF
+
+ o Layer 3 routing on top of Audio Video Bridging (AVB) (and/or other
+ high-QoS (Quality of Service) networks)
+
+ o Content delivery with bounded, lowest possible latency
+
+ o IntServ and DiffServ integration with AVB (where practical)
+
+ o Single network for A/V and IT traffic
+
+ o Standards-based, interoperable, multi-vendor solutions
+
+ o IT-department-friendly networks
+
+ o Enterprise-wide networks (e.g., the size of San Francisco but not
+ the whole Internet (yet...))
+
+
+
+
+
+
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+3. Electrical Utilities
+
+3.1. Use Case Description
+
+ Many systems that an electrical utility deploys today rely on high
+ availability and deterministic behavior of the underlying networks.
+ Presented here are use cases for transmission, generation, and
+ distribution, including key timing and reliability metrics. In
+ addition, security issues and industry trends that affect the
+ architecture of next-generation utility networks are discussed.
+
+3.1.1. Transmission Use Cases
+
+3.1.1.1. Protection
+
+ "Protection" means not only the protection of human operators but
+ also the protection of the electrical equipment and the preservation
+ of the stability and frequency of the grid. If a fault occurs in the
+ transmission or distribution of electricity, then severe damage can
+ occur to human operators, electrical equipment, and the grid itself,
+ leading to blackouts.
+
+ Communication links, in conjunction with protection relays, are used
+ to selectively isolate faults on high-voltage lines, transformers,
+ reactors, and other important electrical equipment. The role of the
+ teleprotection system is to selectively disconnect a faulty part by
+ transferring command signals within the shortest possible time.
+
+3.1.1.1.1. Key Criteria
+
+ The key criteria for measuring teleprotection performance are command
+ transmission time, dependability, and security. These criteria are
+ defined by International Electrotechnical Commission (IEC)
+ Standard 60834 [IEC-60834] as follows:
+
+ o Transmission time (speed): The time between the moment when a
+ state change occurs at the transmitter input and the moment of the
+ corresponding change at the receiver output, including propagation
+ delay. The overall operating time for a teleprotection system is
+ the sum of (1) the time required to initiate the command at the
+ transmitting end, (2) the propagation delay over the network
+ (including equipment), and (3) the time required to make the
+ necessary selections and decisions at the receiving end, including
+ any additional delay due to a noisy environment.
+
+
+
+
+
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+RFC 8578 DetNet Use Cases May 2019
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+
+ o Dependability: The ability to issue and receive valid commands in
+ the presence of interference and/or noise, by minimizing the
+ Probability of Missing Commands (PMC). Dependability targets are
+ typically set for a specific Bit Error Rate (BER) level.
+
+ o Security: The ability to prevent false tripping due to a noisy
+ environment, by minimizing the Probability of Unwanted Commands
+ (PUC). Security targets are also set for a specific BER level.
+
+ Additional elements of the teleprotection system that impact its
+ performance include:
+
+ o Network bandwidth
+
+ o Failure recovery capacity (aka resiliency)
+
+3.1.1.1.2. Fault Detection and Clearance Timing
+
+ Most power-line equipment can tolerate short circuits or faults for
+ up to approximately five power cycles before sustaining irreversible
+ damage or affecting other segments in the network. This translates
+ to a total fault clearance time of 100 ms. As a safety precaution,
+ however, the actual operation time of protection systems is limited
+ to 70-80% of this period, including fault recognition time, command
+ transmission time, and line breaker switching time.
+
+ Some system components, such as large electromechanical switches,
+ require a particularly long time to operate and take up the majority
+ of the total clearance time, leaving only a 10 ms window for the
+ telecommunications part of the protection scheme, independent of the
+ distance of travel. Given the sensitivity of the issue, new
+ networks impose requirements that are even more stringent: IEC
+ Standard 61850-5:2013 [IEC-61850-5:2013] limits the transfer time for
+ protection messages to 1/4-1/2 cycle or 4-8 ms (for 60 Hz lines) for
+ messages considered the most critical.
+
+
+
+
+
+
+
+
+
+
+
+
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+RFC 8578 DetNet Use Cases May 2019
+
+
+3.1.1.1.3. Symmetric Channel Delay
+
+ Teleprotection channels that are differential must be synchronous;
+ this means that any delays on the transmit and receive paths must
+ match each other. Ideally, teleprotection systems support zero
+ asymmetric delay; typical legacy relays can tolerate delay
+ discrepancies of up to 750 us.
+
+ Some tools available for lowering delay variation below this
+ threshold are as follows:
+
+ o For legacy systems using Time-Division Multiplexing (TDM), jitter
+ buffers at the multiplexers on each end of the line can be used to
+ offset delay variation by queuing sent and received packets. The
+ length of the queues must balance the need to regulate the rate of
+ transmission with the need to limit overall delay, as larger
+ buffers result in increased latency.
+
+ o For jitter-prone IP networks, traffic management tools can ensure
+ that the teleprotection signals receive the highest transmission
+ priority to minimize jitter.
+
+ o Standard packet-based synchronization technologies, such as the
+ IEEE 1588-2008 Precision Time Protocol (PTP) [IEEE-1588] and
+ synchronous Ethernet (syncE) [syncE], can help keep networks
+ stable by maintaining a highly accurate clock source on the
+ various network devices.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+RFC 8578 DetNet Use Cases May 2019
+
+
+3.1.1.1.4. Teleprotection Network Requirements
+
+ Table 1 captures the main network metrics. (These metrics are based
+ on IEC Standard 61850-5:2013 [IEC-61850-5:2013].)
+
+ +---------------------------------+---------------------------------+
+ | Teleprotection Requirement | Attribute |
+ +---------------------------------+---------------------------------+
+ | One-way maximum delay | 4-10 ms |
+ | | |
+ | Asymmetric delay required | Yes |
+ | | |
+ | Maximum jitter | Less than 250 us (750 us for |
+ | | legacy IEDs) |
+ | | |
+ | Topology | Point to point, point to |
+ | | multipoint |
+ | | |
+ | Availability | 99.9999% |
+ | | |
+ | Precise timing required | Yes |
+ | | |
+ | Recovery time on node failure | Less than 50 ms - hitless |
+ | | |
+ | Performance management | Yes; mandatory |
+ | | |
+ | Redundancy | Yes |
+ | | |
+ | Packet loss | 0.1% to 1% |
+ +---------------------------------+---------------------------------+
+
+ Table 1: Teleprotection Network Requirements
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
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+RFC 8578 DetNet Use Cases May 2019
+
+
+3.1.1.1.5. Inter-trip Protection Scheme
+
+ "Inter-tripping" is the signal-controlled tripping of a circuit
+ breaker to complete the isolation of a circuit or piece of apparatus
+ in concert with the tripping of other circuit breakers.
+
+ +---------------------------------+---------------------------------+
+ | Inter-trip Protection | Attribute |
+ | Requirement | |
+ +---------------------------------+---------------------------------+
+ | One-way maximum delay | 5 ms |
+ | | |
+ | Asymmetric delay required | No |
+ | | |
+ | Maximum jitter | Not critical |
+ | | |
+ | Topology | Point to point, point to |
+ | | multipoint |
+ | | |
+ | Bandwidth | 64 kbps |
+ | | |
+ | Availability | 99.9999% |
+ | | |
+ | Precise timing required | Yes |
+ | | |
+ | Recovery time on node failure | Less than 50 ms - hitless |
+ | | |
+ | Performance management | Yes; mandatory |
+ | | |
+ | Redundancy | Yes |
+ | | |
+ | Packet loss | 0.1% |
+ +---------------------------------+---------------------------------+
+
+ Table 2: Inter-trip Protection Network Requirements
+
+3.1.1.1.6. Current Differential Protection Scheme
+
+ Current differential protection is commonly used for line protection
+ and is typically used to protect parallel circuits. At both ends of
+ the lines, the current is measured by the differential relays; both
+ relays will trip the circuit breaker if the current going into the
+ line does not equal the current going out of the line. This type of
+ protection scheme assumes that some form of communication is present
+ between the relays at both ends of the line, to allow both relays to
+ compare measured current values. Line differential protection
+ schemes assume that the telecommunications delay between both relays
+ is very low -- often as low as 5 ms. Moreover, as those systems are
+
+
+
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+RFC 8578 DetNet Use Cases May 2019
+
+
+ often not time-synchronized, they also assume that the delay over
+ symmetric telecommunications paths is constant; this allows the
+ comparison of current measurement values taken at exactly the
+ same time.
+
+ +---------------------------------+---------------------------------+
+ | Current Differential Protection | Attribute |
+ | Requirement | |
+ +---------------------------------+---------------------------------+
+ | One-way maximum delay | 5 ms |
+ | | |
+ | Asymmetric delay required | Yes |
+ | | |
+ | Maximum jitter | Less than 250 us (750 us for |
+ | | legacy IEDs) |
+ | | |
+ | Topology | Point to point, point to |
+ | | multipoint |
+ | | |
+ | Bandwidth | 64 kbps |
+ | | |
+ | Availability | 99.9999% |
+ | | |
+ | Precise timing required | Yes |
+ | | |
+ | Recovery time on node failure | Less than 50 ms - hitless |
+ | | |
+ | Performance management | Yes; mandatory |
+ | | |
+ | Redundancy | Yes |
+ | | |
+ | Packet loss | 0.1% |
+ +---------------------------------+---------------------------------+
+
+ Table 3: Current Differential Protection Metrics
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+RFC 8578 DetNet Use Cases May 2019
+
+
+3.1.1.1.7. Distance Protection Scheme
+
+ The distance (impedance relay) protection scheme is based on voltage
+ and current measurements. The network metrics are similar (but not
+ identical) to the metrics for current differential protection.
+
+ +---------------------------------+---------------------------------+
+ | Distance Protection Requirement | Attribute |
+ +---------------------------------+---------------------------------+
+ | One-way maximum delay | 5 ms |
+ | | |
+ | Asymmetric delay required | No |
+ | | |
+ | Maximum jitter | Not critical |
+ | | |
+ | Topology | Point to point, point to |
+ | | multipoint |
+ | | |
+ | Bandwidth | 64 kbps |
+ | | |
+ | Availability | 99.9999% |
+ | | |
+ | Precise timing required | Yes |
+ | | |
+ | Recovery time on node failure | Less than 50 ms - hitless |
+ | | |
+ | Performance management | Yes; mandatory |
+ | | |
+ | Redundancy | Yes |
+ | | |
+ | Packet loss | 0.1% |
+ +---------------------------------+---------------------------------+
+
+ Table 4: Distance Protection Requirements
+
+3.1.1.1.8. Inter-substation Protection Signaling
+
+ This use case describes the exchange of sampled values and/or GOOSE
+ (Generic Object Oriented Substation Events) messages between
+ Intelligent Electronic Devices (IEDs) in two substations for
+ protection and tripping coordination. The two IEDs are in
+ master-slave mode.
+
+ The Current Transformer or Voltage Transformer (CT/VT) in one
+ substation sends the sampled analog voltage or current value to the
+ Merging Unit (MU) over hard wire. The MU sends the time-synchronized
+ sampled values (as specified by IEC 61850-9-2:2011
+ [IEC-61850-9-2:2011]) to the slave IED. The slave IED forwards the
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ information to the master IED in the other substation. The master
+ IED makes the determination (for example, based on sampled value
+ differentials) to send a trip command to the originating IED. Once
+ the slave IED/relay receives the GOOSE message containing the command
+ to trip the breaker, it opens the breaker. It then sends a
+ confirmation message back to the master. All data exchanges between
+ IEDs are through sampled values and/or GOOSE messages.
+
+ +---------------------------------+---------------------------------+
+ | Inter-substation Protection | Attribute |
+ | Requirement | |
+ +---------------------------------+---------------------------------+
+ | One-way maximum delay | 5 ms |
+ | | |
+ | Asymmetric delay required | No |
+ | | |
+ | Maximum jitter | Not critical |
+ | | |
+ | Topology | Point to point, point to |
+ | | multipoint |
+ | | |
+ | Bandwidth | 64 kbps |
+ | | |
+ | Availability | 99.9999% |
+ | | |
+ | Precise timing required | Yes |
+ | | |
+ | Recovery time on node failure | Less than 50 ms - hitless |
+ | | |
+ | Performance management | Yes; mandatory |
+ | | |
+ | Redundancy | Yes |
+ | | |
+ | Packet loss | 1% |
+ +---------------------------------+---------------------------------+
+
+ Table 5: Inter-substation Protection Requirements
+
+3.1.1.2. Intra-substation Process Bus Communications
+
+ This use case describes the data flow from the CT/VT to the IEDs in
+ the substation via the MU. The CT/VT in the substation sends the
+ analog voltage or current values to the MU over hard wire. The MU
+ converts the analog values into digital format (typically
+ time-synchronized sampled values as specified by IEC 61850-9-2:2011
+ [IEC-61850-9-2:2011]) and sends them to the IEDs in the substation.
+ The Global Positioning System (GPS) Master Clock can send 1PPS or
+ IRIG-B format to the MU through a serial port or IEEE 1588 protocol
+
+
+
+Grossman Informational [Page 21]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ via a network. 1PPS (One Pulse Per Second) is an electrical signal
+ that has a width of less than 1 second and a sharply rising or
+ abruptly falling edge that accurately repeats once per second. 1PPS
+ signals are output by radio beacons, frequency standards, other types
+ of precision oscillators, and some GPS receivers. IRIG (Inter-Range
+ Instrumentation Group) time codes are standard formats for
+ transferring timing information. Atomic frequency standards and GPS
+ receivers designed for precision timing are often equipped with an
+ IRIG output. Process bus communication using IEC 61850-9-2:2011
+ [IEC-61850-9-2:2011] simplifies connectivity within the substation,
+ removes the requirement for multiple serial connections, and removes
+ the slow serial-bus architectures that are typically used. This also
+ ensures increased flexibility and increased speed with the use of
+ multicast messaging between multiple devices.
+
+ +---------------------------------+---------------------------------+
+ | Intra-substation Protection | Attribute |
+ | Requirement | |
+ +---------------------------------+---------------------------------+
+ | One-way maximum delay | 5 ms |
+ | | |
+ | Asymmetric delay required | No |
+ | | |
+ | Maximum jitter | Not critical |
+ | | |
+ | Topology | Point to point, point to |
+ | | multipoint |
+ | | |
+ | Bandwidth | 64 kbps |
+ | | |
+ | Availability | 99.9999% |
+ | | |
+ | Precise timing required | Yes |
+ | | |
+ | Recovery time on node failure | Less than 50 ms - hitless |
+ | | |
+ | Performance management | Yes; mandatory |
+ | | |
+ | Redundancy | Yes or No |
+ | | |
+ | Packet loss | 0.1% |
+ +---------------------------------+---------------------------------+
+
+ Table 6: Intra-substation Protection Requirements
+
+
+
+
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+3.1.1.3. Wide-Area Monitoring and Control Systems
+
+ The application of synchrophasor measurement data from Phasor
+ Measurement Units (PMUs) to wide-area monitoring and control systems
+ promises to provide important new capabilities for improving system
+ stability. Access to PMU data enables more-timely situational
+ awareness over larger portions of the grid than what has been
+ possible historically with normal SCADA (Supervisory Control and Data
+ Acquisition) data. Handling the volume and the real-time nature of
+ synchrophasor data presents unique challenges for existing
+ application architectures. The Wide-Area Management System (WAMS)
+ makes it possible for the condition of the bulk power system to be
+ observed and understood in real time so that protective,
+ preventative, or corrective action can be taken. Because of the very
+ high sampling rate of measurements and the strict requirement for
+ time synchronization of the samples, the WAMS has stringent
+ telecommunications requirements in an IP network, as captured in
+ Table 7:
+
+
+
+
+
+
+
+
+
+
+
+
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+RFC 8578 DetNet Use Cases May 2019
+
+
+ +---------------------------------+---------------------------------+
+ | WAMS Requirement | Attribute |
+ +---------------------------------+---------------------------------+
+ | One-way maximum delay | 50 ms |
+ | | |
+ | Asymmetric delay required | No |
+ | | |
+ | Maximum jitter | Not critical |
+ | | |
+ | Topology | Point to point, point to |
+ | | multipoint, multipoint to |
+ | | multipoint |
+ | | |
+ | Bandwidth | 100 kbps |
+ | | |
+ | Availability | 99.9999% |
+ | | |
+ | Precise timing required | Yes |
+ | | |
+ | Recovery time on node failure | Less than 50 ms - hitless |
+ | | |
+ | Performance management | Yes; mandatory |
+ | | |
+ | Redundancy | Yes |
+ | | |
+ | Packet loss | 1% |
+ | | |
+ | Consecutive packet loss | At least one packet per |
+ | | application cycle must be |
+ | | received. |
+ +---------------------------------+---------------------------------+
+
+ Table 7: WAMS Special Communication Requirements
+
+
+
+
+
+
+
+
+
+
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+RFC 8578 DetNet Use Cases May 2019
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+
+3.1.1.4. WAN Engineering Guidelines Requirement Classification
+
+ The IEC has published a technical report (TR) that offers guidelines
+ on how to define and deploy Wide-Area Networks (WANs) for the
+ interconnection of electric substations, generation plants, and SCADA
+ operation centers. IEC TR 61850-90-12:2015 [IEC-61850-90-12:2015]
+ provides four classes of WAN communication requirements, as
+ summarized in Table 8:
+
+ +----------------+-----------+----------+----------+----------------+
+ | WAN | Class WA | Class WB | Class WC | Class WD |
+ | Requirement | | | | |
+ +----------------+-----------+----------+----------+----------------+
+ | Application | EHV | HV (High | MV | General- |
+ | field | (Extra- | Voltage) | (Medium | purpose |
+ | | High | | Voltage) | |
+ | | Voltage) | | | |
+ | | | | | |
+ | Latency | 5 ms | 10 ms | 100 ms | >100 ms |
+ | | | | | |
+ | Jitter | 10 us | 100 us | 1 ms | 10 ms |
+ | | | | | |
+ | Latency | 100 us | 1 ms | 10 ms | 100 ms |
+ | asymmetry | | | | |
+ | | | | | |
+ | Time accuracy | 1 us | 10 us | 100 us | 10 to 100 ms |
+ | | | | | |
+ | BER | 10^-7 to | 10^-5 to | 10^-3 | |
+ | | 10^-6 | 10^-4 | | |
+ | | | | | |
+ | Unavailability | 10^-7 to | 10^-5 to | 10^-3 | |
+ | | 10^-6 | 10^-4 | | |
+ | | | | | |
+ | Recovery delay | Zero | 50 ms | 5 s | 50 s |
+ | | | | | |
+ | Cybersecurity | Extremely | High | Medium | Medium |
+ | | high | | | |
+ +----------------+-----------+----------+----------+----------------+
+
+ Table 8: Communication Requirements (Courtesy of
+ IEC TR 61850-90-12:2015)
+
+
+
+
+
+
+
+
+
+
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+RFC 8578 DetNet Use Cases May 2019
+
+
+3.1.2. Generation Use Case
+
+ Energy generation systems are complex infrastructures that require
+ control of both the generated power and the generation
+ infrastructure.
+
+3.1.2.1. Control of the Generated Power
+
+ The electrical power generation frequency must be maintained within a
+ very narrow band. Deviations from the acceptable frequency range are
+ detected, and the required signals are sent to the power plants for
+ frequency regulation.
+
+ Automatic Generation Control (AGC) is a system for adjusting the
+ power output of generators at different power plants, in response to
+ changes in the load.
+
+ +---------------------------------+---------------------------------+
+ | FCAG (Frequency Control | Attribute |
+ | Automatic Generation) | |
+ | Requirement | |
+ +---------------------------------+---------------------------------+
+ | One-way maximum delay | 500 ms |
+ | | |
+ | Asymmetric delay required | No |
+ | | |
+ | Maximum jitter | Not critical |
+ | | |
+ | Topology | Point to point |
+ | | |
+ | Bandwidth | 20 kbps |
+ | | |
+ | Availability | 99.999% |
+ | | |
+ | Precise timing required | Yes |
+ | | |
+ | Recovery time on node failure | N/A |
+ | | |
+ | Performance management | Yes; mandatory |
+ | | |
+ | Redundancy | Yes |
+ | | |
+ | Packet loss | 1% |
+ +---------------------------------+---------------------------------+
+
+ Table 9: FCAG Communication Requirements
+
+
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+3.1.2.2. Control of the Generation Infrastructure
+
+ The control of the generation infrastructure combines requirements
+ from industrial automation systems and energy generation systems.
+ This section describes the use case for control of the generation
+ infrastructure of a wind turbine.
+
+ Figure 1 presents the subsystems that operate a wind turbine.
+
+ |
+ |
+ | +-----------------+
+ | | +----+ |
+ | | |WTRM| WGEN |
+ WROT x==|===| | |
+ | | +----+ WCNV|
+ | |WNAC |
+ | +---+---WYAW---+--+
+ | | |
+ | | | +----+
+ |WTRF | |WMET|
+ | | | |
+ Wind Turbine | +--+-+
+ Controller | |
+ WTUR | | |
+ WREP | | |
+ WSLG | | |
+ WALG | WTOW | |
+
+ Figure 1: Wind Turbine Control Network
+
+ The subsystems shown in Figure 1 include the following:
+
+ o WROT (rotor control)
+
+ o WNAC (nacelle control) (nacelle: housing containing the generator)
+
+ o WTRM (transmission control)
+
+ o WGEN (generator)
+
+ o WYAW (yaw controller) (of the tower head)
+
+ o WCNV (in-turbine power converter)
+
+ o WTRF (wind turbine transformer information)
+
+
+
+
+
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+RFC 8578 DetNet Use Cases May 2019
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+
+ o WMET (external meteorological station providing real-time
+ information to the tower's controllers)
+
+ o WTUR (wind turbine general information)
+
+ o WREP (wind turbine report information)
+
+ o WSLG (wind turbine state log information)
+
+ o WALG (wind turbine analog log information)
+
+ o WTOW (wind turbine tower information)
+
+ Traffic characteristics relevant to the network planning and
+ dimensioning process in a wind turbine scenario are listed below.
+ The values in this section are based mainly on the relevant
+ references [Ahm14] and [Spe09]. Each logical node (Figure 1) is a
+ part of the metering network and produces analog measurements and
+ status information that must comply with their respective data-rate
+ constraints.
+
+ +-----------+--------+----------+-----------+-----------+-----------+
+ | Subsystem | Sensor | Analog | Data Rate | Status | Data Rate |
+ | | Count | Sample | (bytes/s) | Sample | (bytes/s) |
+ | | | Count | | Count | |
+ +-----------+--------+----------+-----------+-----------+-----------+
+ | WROT | 14 | 9 | 642 | 5 | 10 |
+ | | | | | | |
+ | WTRM | 18 | 10 | 2828 | 8 | 16 |
+ | | | | | | |
+ | WGEN | 14 | 12 | 73764 | 2 | 4 |
+ | | | | | | |
+ | WCNV | 14 | 12 | 74060 | 2 | 4 |
+ | | | | | | |
+ | WTRF | 12 | 5 | 73740 | 2 | 4 |
+ | | | | | | |
+ | WNAC | 12 | 9 | 112 | 3 | 6 |
+ | | | | | | |
+ | WYAW | 7 | 8 | 220 | 4 | 8 |
+ | | | | | | |
+ | WTOW | 4 | 1 | 8 | 3 | 6 |
+ | | | | | | |
+ | WMET | 7 | 7 | 228 | - | - |
+ +-----------+--------+----------+-----------+-----------+-----------+
+
+ Table 10: Wind Turbine Data-Rate Constraints
+
+
+
+
+
+Grossman Informational [Page 28]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ QoS constraints for different services are presented in Table 11.
+ These constraints are defined by IEEE Standard 1646 [IEEE-1646] and
+ IEC Standard 61400 Part 25 [IEC-61400-25].
+
+ +---------------------+---------+-------------+---------------------+
+ | Service | Latency | Reliability | Packet Loss Rate |
+ +---------------------+---------+-------------+---------------------+
+ | Analog measurement | 16 ms | 99.99% | <10^-6 |
+ | | | | |
+ | Status information | 16 ms | 99.99% | <10^-6 |
+ | | | | |
+ | Protection traffic | 4 ms | 100.00% | <10^-9 |
+ | | | | |
+ | Reporting and | 1 s | 99.99% | <10^-6 |
+ | logging | | | |
+ | | | | |
+ | Video surveillance | 1 s | 99.00% | No specific |
+ | | | | requirement |
+ | | | | |
+ | Internet connection | 60 min | 99.00% | No specific |
+ | | | | requirement |
+ | | | | |
+ | Control traffic | 16 ms | 100.00% | <10^-9 |
+ | | | | |
+ | Data polling | 16 ms | 99.99% | <10^-6 |
+ +---------------------+---------+-------------+---------------------+
+
+ Table 11: Wind Turbine Reliability and Latency Constraints
+
+3.1.2.2.1. Intra-domain Network Considerations
+
+ A wind turbine is composed of a large set of subsystems, including
+ sensors and actuators that require time-critical operation. The
+ reliability and latency constraints of these different subsystems are
+ shown in Table 11. These subsystems are connected to an intra-domain
+ network that is used to monitor and control the operation of the
+ turbine and connect it to the SCADA subsystems. The different
+ components are interconnected using fiber optics, industrial buses,
+ industrial Ethernet, EtherCAT [EtherCAT], or a combination thereof.
+ Industrial signaling and control protocols such as Modbus [MODBUS],
+ PROFIBUS [PROFIBUS], PROFINET [PROFINET], and EtherCAT are used
+ directly on top of the Layer 2 transport or encapsulated over TCP/IP.
+
+ The data collected from the sensors and condition-monitoring systems
+ is multiplexed onto fiber cables for transmission to the base of the
+ tower and to remote control centers. The turbine controller
+ continuously monitors the condition of the wind turbine and collects
+
+
+
+
+Grossman Informational [Page 29]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ statistics on its operation. This controller also manages a large
+ number of switches, hydraulic pumps, valves, and motors within the
+ wind turbine.
+
+ There is usually a controller at the bottom of the tower and also in
+ the nacelle. The communication between these two controllers usually
+ takes place using fiber optics instead of copper links. Sometimes, a
+ third controller is installed in the hub of the rotor and manages the
+ pitch of the blades. That unit usually communicates with the nacelle
+ unit using serial communications.
+
+3.1.2.2.2. Inter-domain Network Considerations
+
+ A remote control center belonging to a grid operator regulates the
+ power output, enables remote actuation, and monitors the health of
+ one or more wind parks in tandem. It connects to the local control
+ center in a wind park over the Internet (Figure 2) via firewalls at
+ both ends. The Autonomous System (AS) path between the local control
+ center and the wind park typically involves several ISPs at different
+ tiers. For example, a remote control center in Denmark can regulate
+ a wind park in Greece over the normal public AS path between the two
+ locations.
+
+ +--------------+
+ | |
+ | |
+ | Wind Park #1 +----+
+ | | | XXXXXX
+ | | | X XXXXXXXX +----------------+
+ +--------------+ | XXXX X XXXXX | |
+ +---+ XXX | Remote Control |
+ XXX Internet +----+ Center |
+ +----+X XXX | |
+ +--------------+ | XXXXXXX XX | |
+ | | | XX XXXXXXX +----------------+
+ | | | XXXXX
+ | Wind Park #2 +----+
+ | |
+ | |
+ +--------------+
+
+ Figure 2: Wind Turbine Control via Internet
+
+ The remote control center is part of the SCADA system, setting the
+ desired power output to the wind park and reading back the result
+ once the new power output level has been set. Traffic between the
+ remote control center and the wind park typically consists of
+ protocols like IEC 60870-5-104 [IEC-60870-5-104], OPC XML-Data Access
+
+
+
+Grossman Informational [Page 30]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ (XML-DA) [OPCXML], Modbus [MODBUS], and SNMP [RFC3411]. At the time
+ of this writing, traffic flows between the remote control center and
+ the wind park are best effort. QoS requirements are not strict, so
+ no Service Level Agreements (SLAs) or service-provisioning mechanisms
+ (e.g., VPNs) are employed. In the case of such events as equipment
+ failure, tolerance for alarm delay is on the order of minutes, due to
+ redundant systems already in place.
+
+ Future use cases will require bounded latency, bounded jitter, and
+ extraordinarily low packet loss for inter-domain traffic flows due to
+ the softwarization and virtualization of core wind-park equipment
+ (e.g., switches, firewalls, and SCADA server components). These
+ factors will create opportunities for service providers to install
+ new services and dynamically manage them from remote locations. For
+ example, to enable failover of a local SCADA server, a SCADA server
+ in another wind-park site (under the administrative control of the
+ same operator) could be utilized temporarily (Figure 3). In that
+ case, local traffic would be forwarded to the remote SCADA server,
+ and existing intra-domain QoS and timing parameters would have to be
+ met for inter-domain traffic flows.
+
+ +--------------+
+ | |
+ | |
+ | Wind Park #1 +----+
+ | | | XXXXXX
+ | | | X XXXXXXXX +----------------+
+ +--------------+ | XXXX XXXXX | |
+ +---+ Operator- XXX | Remote Control |
+ XXX Administered +----+ Center |
+ +----+X WAN XXX | |
+ +--------------+ | XXXXXXX XX | |
+ | | | XX XXXXXXX +----------------+
+ | | | XXXXX
+ | Wind Park #2 +----+
+ | |
+ | |
+ +--------------+
+
+ Figure 3: Wind Turbine Control via Operator-Administered WAN
+
+
+
+
+
+
+
+
+
+
+
+Grossman Informational [Page 31]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+3.1.3. Distribution Use Case
+
+3.1.3.1. Fault Location, Isolation, and Service Restoration (FLISR)
+
+ "Fault Location, Isolation, and Service Restoration (FLISR)" refers
+ to the ability to automatically locate the fault, isolate the fault,
+ and restore service in the distribution network. This will likely
+ be the first widespread application of distributed intelligence in
+ the grid.
+
+ The static power-switch status (open/closed) in the network dictates
+ the power flow to secondary substations. Reconfiguring the network
+ in the event of a fault is typically done manually on site to
+ energize/de-energize alternate paths. Automating the operation of
+ substation switchgear allows the flow of power to be altered
+ automatically under fault conditions.
+
+ FLISR can be managed centrally from a Distribution Management System
+ (DMS) or executed locally through distributed control via intelligent
+ switches and fault sensors.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Grossman Informational [Page 32]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ +---------------------------------+---------------------------------+
+ | FLISR Requirement | Attribute |
+ +---------------------------------+---------------------------------+
+ | One-way maximum delay | 80 ms |
+ | | |
+ | Asymmetric delay required | No |
+ | | |
+ | Maximum jitter | 40 ms |
+ | | |
+ | Topology | Point to point, point to |
+ | | multipoint, multipoint to |
+ | | multipoint |
+ | | |
+ | Bandwidth | 64 kbps |
+ | | |
+ | Availability | 99.9999% |
+ | | |
+ | Precise timing required | Yes |
+ | | |
+ | Recovery time on node failure | Depends on customer impact |
+ | | |
+ | Performance management | Yes; mandatory |
+ | | |
+ | Redundancy | Yes |
+ | | |
+ | Packet loss | 0.1% |
+ +---------------------------------+---------------------------------+
+
+ Table 12: FLISR Communication Requirements
+
+3.2. Electrical Utilities Today
+
+ Many utilities still rely on complex environments consisting of
+ multiple application-specific proprietary networks, including TDM
+ networks.
+
+ In this kind of environment, there is no mixing of Operation
+ Technology (OT) and IT applications on the same network, and
+ information is siloed between operational areas.
+
+ Specific calibration of the full chain is required; this is costly.
+
+ This kind of environment prevents utility operations from realizing
+ operational efficiency benefits, visibility, and functional
+ integration of operational information across grid applications and
+ data networks.
+
+
+
+
+
+Grossman Informational [Page 33]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ In addition, there are many security-related issues, as discussed in
+ the following section.
+
+3.2.1. Current Security Practices and Their Limitations
+
+ Grid-monitoring and control devices are already targets for cyber
+ attacks, and legacy telecommunications protocols have many intrinsic
+ network-related vulnerabilities. For example, the Distributed
+ Network Protocol (DNP3) [IEEE-1815], Modbus, PROFIBUS/PROFINET, and
+ other protocols are designed around a common paradigm of "request and
+ respond". Each protocol is designed for a master device such as an
+ HMI (Human-Machine Interface) system to send commands to subordinate
+ slave devices to perform data retrieval (reading inputs) or control
+ functions (writing to outputs). Because many of these protocols lack
+ authentication, encryption, or other basic security measures, they
+ are prone to network-based attacks, allowing a malicious actor or
+ attacker to utilize the request-and-respond system as a mechanism for
+ functionality similar to command and control. Specific security
+ concerns common to most industrial-control protocols (including
+ utility telecommunications protocols) include the following:
+
+ o Network or transport errors (e.g., malformed packets or excessive
+ latency) can cause protocol failure.
+
+ o Protocol commands may be available that are capable of forcing
+ slave devices into inoperable states, including powering devices
+ off, forcing them into a listen-only state, or disabling alarming.
+
+ o Protocol commands may be available that are capable of
+ interrupting processes (e.g., restarting communications).
+
+ o Protocol commands may be available that are capable of clearing,
+ erasing, or resetting diagnostic information such as counters and
+ diagnostic registers.
+
+ o Protocol commands may be available that are capable of requesting
+ sensitive information about the controllers, their configurations,
+ or other need-to-know information.
+
+ o Most protocols are application-layer protocols transported over
+ TCP; it is therefore easy to transport commands over non-standard
+ ports or inject commands into authorized traffic flows.
+
+ o Protocol commands may be available that are capable of
+ broadcasting messages to many devices at once (i.e., a
+ potential DoS).
+
+
+
+
+
+Grossman Informational [Page 34]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ o Protocol commands may be available that will query the device
+ network to obtain defined points and their values (i.e., perform a
+ configuration scan).
+
+ o Protocol commands may be available that will list all available
+ function codes (i.e., perform a function scan).
+
+ These inherent vulnerabilities, along with increasing connectivity
+ between IT and OT networks, make network-based attacks very feasible.
+ By injecting malicious protocol commands, an attacker could take
+ control over the target process. Altering legitimate protocol
+ traffic can also alter information about a process and disrupt the
+ legitimate controls that are in place over that process. A
+ man-in-the-middle attack could result in (1) improper control over a
+ process and (2) misrepresentation of data that is sent back to
+ operator consoles.
+
+3.3. Electrical Utilities in the Future
+
+ The business and technology trends that are sweeping the utility
+ industry will drastically transform the utility business from the way
+ it has been for many decades. At the core of many of these changes
+ is a drive to modernize the electrical grid with an integrated
+ telecommunications infrastructure. However, interoperability
+ concerns, legacy networks, disparate tools, and stringent security
+ requirements all add complexity to the grid's transformation. Given
+ the range and diversity of the requirements that should be addressed
+ by the next-generation telecommunications infrastructure, utilities
+ need to adopt a holistic architectural approach to integrate the
+ electrical grid with digital telecommunications across the entire
+ power delivery chain.
+
+ The key to modernizing grid telecommunications is to provide a
+ common, adaptable, multi-service network infrastructure for the
+ entire utility organization. Such a network serves as the platform
+ for current capabilities while enabling future expansion of the
+ network to accommodate new applications and services.
+
+ To meet this diverse set of requirements both today and in the
+ future, the next-generation utility telecommunications network will
+ be based on an open-standards-based IP architecture. An end-to-end
+ IP architecture takes advantage of nearly three decades of IP
+ technology development, facilitating interoperability and device
+ management across disparate networks and devices, as has already been
+ demonstrated in many mission-critical and highly secure networks.
+
+
+
+
+
+
+Grossman Informational [Page 35]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ IPv6 is seen as a future telecommunications technology for the smart
+ grid; the IEC and different national committees have mandated a
+ specific ad hoc group (AHG8) to define the strategy for migration to
+ IPv6 for all the IEC Technical Committee 57 (TC 57) power automation
+ standards. The AHG8 has finalized its work on the migration
+ strategy, and IEC TR 62357-200:2015 [IEC-62357-200:2015] has been
+ issued.
+
+ Cloud-based SCADA systems will control and monitor the critical and
+ non-critical subsystems of generation systems -- for example, wind
+ parks.
+
+3.3.1. Migration to Packet-Switched Networks
+
+ Throughout the world, utilities are increasingly planning for a
+ future based on smart-grid applications requiring advanced
+ telecommunications systems. Many of these applications utilize
+ packet connectivity for communicating information and control signals
+ across the utility's WAN, made possible by technologies such as
+ Multiprotocol Label Switching (MPLS). The data that traverses the
+ utility WAN includes:
+
+ o Grid monitoring, control, and protection data
+
+ o Non-control grid data (e.g., asset data for condition monitoring)
+
+ o Data (e.g., voice and video) related to physical safety and
+ security
+
+ o Remote worker access to corporate applications (voice, maps,
+ schematics, etc.)
+
+ o Field area network Backhaul for smart metering
+
+ o Distribution-grid management
+
+ o Enterprise traffic (email, collaboration tools, business
+ applications)
+
+ WANs support this wide variety of traffic to and from substations,
+ the transmission and distribution grid, and generation sites; between
+ control centers; and between work locations and data centers. To
+ maintain this rapidly expanding set of applications, many utilities
+ are taking steps to evolve present TDM-based and frame relay
+ infrastructures to packet systems. Packet-based networks are
+ designed to provide greater functionalities and higher levels of
+ service for applications, while continuing to deliver reliability and
+ deterministic (real-time) traffic support.
+
+
+
+Grossman Informational [Page 36]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+3.3.2. Telecommunications Trends
+
+ These general telecommunications topics are provided in addition to
+ the use cases that have been addressed so far. These include both
+ current and future telecommunications-related topics that should be
+ factored into the network architecture and design.
+
+3.3.2.1. General Telecommunications Requirements
+
+ o IP connectivity everywhere
+
+ o Monitoring services everywhere, and from different remote centers
+
+ o Moving services to a virtual data center
+
+ o Unified access to applications/information from the corporate
+ network
+
+ o Unified services
+
+ o Unified communications solutions
+
+ o Mix of fiber and microwave technologies - obsolescence of the
+ Synchronous Optical Network / Synchronous Digital Hierarchy
+ (SONET/SDH) or TDM
+
+ o Standardizing grid telecommunications protocols to open standards,
+ to ensure interoperability
+
+ o Reliable telecommunications for transmission and distribution
+ substations
+
+ o IEEE 1588 time-synchronization client/server capabilities
+
+ o Integration of multicast design
+
+ o Mapping of QoS requirements
+
+ o Enabling future network expansion
+
+ o Substation network resilience
+
+ o Fast convergence design
+
+ o Scalable headend design
+
+ o Defining SLAs and enabling SLA monitoring
+
+
+
+
+Grossman Informational [Page 37]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ o Integration of 3G/4G technologies and future technologies
+
+ o Ethernet connectivity for station bus architecture
+
+ o Ethernet connectivity for process bus architecture
+
+ o Protection, teleprotection, and PMUs on IP
+
+3.3.2.2. Specific Network Topologies of Smart-Grid Applications
+
+ Utilities often have very large private telecommunications networks
+ that can cover an entire territory/country. Until now, the main
+ purposes of these networks have been to (1) support transmission
+ network monitoring, control, and automation, (2) support remote
+ control of generation sites, and (3) provide FCAPS (Fault,
+ Configuration, Accounting, Performance, and Security) services from
+ centralized network operation centers.
+
+ Going forward, one network will support the operation and maintenance
+ of electrical networks (generation, transmission, and distribution),
+ voice and data services for tens of thousands of employees and for
+ exchanges with neighboring interconnections, and administrative
+ services. To meet those requirements, a utility may deploy several
+ physical networks leveraging different technologies across the
+ country -- for instance, an optical network and a microwave network.
+ Each protection and automation system between two points has two
+ telecommunications circuits, one on each network. Path diversity
+ between two substations is key. Regardless of the event type
+ (hurricane, ice storm, etc.), one path needs to stay available so the
+ system can still operate.
+
+ In the optical network, signals are transmitted over more than tens
+ of thousands of circuits using fiber optic links, microwave links,
+ and telephone cables. This network is the nervous system of the
+ utility's power transmission operations. The optical network
+ represents tens of thousands of kilometers of cable deployed along
+ the power lines, with individual runs as long as 280 km.
+
+3.3.2.3. Precision Time Protocol
+
+ Some utilities do not use GPS clocks in generation substations. One
+ of the main reasons is that some of the generation plants are 30 to
+ 50 meters deep underground and the GPS signal can be weak and
+ unreliable. Instead, atomic clocks are used. Clocks are
+ synchronized amongst each other. Rubidium clocks provide clock and
+ 1 ms timestamps for IRIG-B.
+
+
+
+
+
+Grossman Informational [Page 38]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ Some companies plan to transition to PTP [IEEE-1588], distributing
+ the synchronization signal over the IP/MPLS network. PTP provides a
+ mechanism for synchronizing the clocks of participating nodes to a
+ high degree of accuracy and precision.
+
+ PTP operates based on the following assumptions:
+
+ o The network eliminates cyclic forwarding of PTP messages within
+ each communication path (e.g., by using a spanning tree protocol).
+
+ o PTP is tolerant of an occasional missed message, duplicated
+ message, or message that arrived out of order. However, PTP
+ assumes that such impairments are relatively rare.
+
+ o As designed, PTP expects a multicast communication model; however,
+ PTP also supports a unicast communication model as long as the
+ behavior of the protocol is preserved.
+
+ o Like all message-based time transfer protocols, PTP time accuracy
+ is degraded by delay asymmetry in the paths taken by event
+ messages. PTP cannot detect asymmetry, but if such delays are
+ known a priori, time values can be adjusted to correct for
+ asymmetry.
+
+ The use of PTP for power automation is defined in
+ IEC/IEEE 61850-9-3:2016 [IEC-IEEE-61850-9-3:2016]. It is based on
+ Annex B of IEC 62439-3:2016 [IEC-62439-3:2016], which offers the
+ support of redundant attachment of clocks to Parallel Redundancy
+ Protocol (PRP) and High-availability Seamless Redundancy (HSR)
+ networks.
+
+3.3.3. Security Trends in Utility Networks
+
+ Although advanced telecommunications networks can assist in
+ transforming the energy industry by playing a critical role in
+ maintaining high levels of reliability, performance, and
+ manageability, they also introduce the need for an integrated
+ security infrastructure. Many of the technologies being deployed to
+ support smart-grid projects such as smart meters and sensors can
+ increase the vulnerability of the grid to attack. Top security
+ concerns for utilities migrating to an intelligent smart-grid
+ telecommunications platform center on the following trends:
+
+ o Integration of distributed energy resources
+
+ o Proliferation of digital devices to enable management, automation,
+ protection, and control
+
+
+
+
+Grossman Informational [Page 39]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ o Regulatory mandates to comply with standards for critical
+ infrastructure protection
+
+ o Migration to new systems for outage management, distribution
+ automation, condition-based maintenance, load forecasting, and
+ smart metering
+
+ o Demand for new levels of customer service and energy management
+
+ This development of a diverse set of networks to support the
+ integration of microgrids, open-access energy competition, and the
+ use of network-controlled devices is driving the need for a converged
+ security infrastructure for all participants in the smart grid,
+ including utilities, energy service providers, large commercial and
+ industrial customers, and residential customers. Securing the assets
+ of electric power delivery systems (from the control center to the
+ substation, to the feeders and down to customer meters) requires an
+ end-to-end security infrastructure that protects the myriad of
+ telecommunications assets used to operate, monitor, and control power
+ flow and measurement.
+
+ "Cybersecurity" refers to all the security issues in automation and
+ telecommunications that affect any functions related to the operation
+ of the electric power systems. Specifically, it involves the
+ concepts of:
+
+ o Integrity: data cannot be altered undetectably
+
+ o Authenticity (data origin authentication): the telecommunications
+ parties involved must be validated as genuine
+
+ o Authorization: only requests and commands from authorized users
+ can be accepted by the system
+
+ o Confidentiality: data must not be accessible to any
+ unauthenticated users
+
+ When designing and deploying new smart-grid devices and
+ telecommunications systems, it is imperative to understand the
+ various impacts of these new components under a variety of attack
+ situations on the power grid. The consequences of a cyber attack on
+ the grid telecommunications network can be catastrophic. This is why
+ security for the smart grid is not just an ad hoc feature or product;
+ it's a complete framework integrating both physical and cybersecurity
+ requirements and covering the entire smart-grid networks from
+ generation to distribution. Security has therefore become one of the
+ main foundations of the utility telecom network architecture and must
+ be considered at every layer with a defense-in-depth approach.
+
+
+
+Grossman Informational [Page 40]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ Migrating to IP-based protocols is key to addressing these challenges
+ for two reasons:
+
+ o IP enables a rich set of features and capabilities to enhance the
+ security posture.
+
+ o IP is based on open standards; this allows interoperability
+ between different vendors and products, driving down the costs
+ associated with implementing security solutions in OT networks.
+
+ Securing OT telecommunications over packet-switched IP networks
+ follows the same principles that are foundational for securing the IT
+ infrastructure, i.e., consideration must be given to (1) enforcing
+ electronic access control for both person-to-machine and machine-to-
+ machine communications and (2) providing the appropriate levels of
+ data privacy, device and platform integrity, and threat detection and
+ mitigation.
+
+3.4. Electrical Utilities Requests to the IETF
+
+ o Mixed Layer 2 and Layer 3 topologies
+
+ o Deterministic behavior
+
+ o Bounded latency and jitter
+
+ o Tight feedback intervals
+
+ o High availability, low recovery time
+
+ o Redundancy, low packet loss
+
+ o Precise timing
+
+ o Centralized computing of deterministic paths
+
+ o Distributed configuration (may also be useful)
+
+4. Building Automation Systems (BASs)
+
+4.1. Use Case Description
+
+ A BAS manages equipment and sensors in a building for improving
+ residents' comfort, reducing energy consumption, and responding to
+ failures and emergencies. For example, the BAS measures the
+ temperature of a room using sensors and then controls the HVAC
+ (heating, ventilating, and air conditioning) to maintain a set
+ temperature and minimize energy consumption.
+
+
+
+Grossman Informational [Page 41]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ A BAS primarily performs the following functions:
+
+ o Periodically measures states of devices -- for example, humidity
+ and illuminance of rooms, open/close state of doors, fan speed.
+
+ o Stores the measured data.
+
+ o Provides the measured data to BAS operators.
+
+ o Generates alarms for abnormal state of devices.
+
+ o Controls devices (e.g., turns room lights off at 10:00 PM).
+
+4.2. BASs Today
+
+4.2.1. BAS Architecture
+
+ A typical present-day BAS architecture is shown in Figure 4.
+
+ +----------------------------+
+ | |
+ | BMS HMI |
+ | | | |
+ | +----------------------+ |
+ | | Management Network | |
+ | +----------------------+ |
+ | | | |
+ | LC LC |
+ | | | |
+ | +----------------------+ |
+ | | Field Network | |
+ | +----------------------+ |
+ | | | | | |
+ | Dev Dev Dev Dev |
+ | |
+ +----------------------------+
+
+ BMS: Building Management Server
+ HMI: Human-Machine Interface
+ LC: Local Controller
+
+ Figure 4: BAS Architecture
+
+ There are typically two layers of a network in a BAS. The upper
+ layer is called the management network, and the lower layer is called
+ the field network. In management networks, an IP-based communication
+ protocol is used, while in field networks, non-IP-based communication
+
+
+
+
+Grossman Informational [Page 42]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ protocols ("field protocols") are mainly used. Field networks have
+ specific timing requirements, whereas management networks can be best
+ effort.
+
+ An HMI is typically a desktop PC used by operators to monitor and
+ display device states, send device control commands to Local
+ Controllers (LCs), and configure building schedules (for example,
+ "turn off all room lights in the building at 10:00 PM").
+
+ A building management server (BMS) performs the following operations.
+
+ o Collects and stores device states from LCs at regular intervals.
+
+ o Sends control values to LCs according to a building schedule.
+
+ o Sends an alarm signal to operators if it detects abnormal device
+ states.
+
+ The BMS and HMI communicate with LCs via IP-based "management
+ protocols" (see standards [BACnet-IP] and [KNX]).
+
+ An LC is typically a Programmable Logic Controller (PLC) that is
+ connected to several tens or hundreds of devices using "field
+ protocols". An LC performs the following kinds of operations:
+
+ o Measures device states and provides the information to a BMS
+ or HMI.
+
+ o Sends control values to devices, unilaterally or as part of a
+ feedback control loop.
+
+ At the time of this writing, many field protocols are in use; some
+ are standards-based protocols, and others are proprietary (see
+ standards [LonTalk], [MODBUS], [PROFIBUS], and [FL-net]). The result
+ is that BASs have multiple MAC/PHY modules and interfaces. This
+ makes BASs more expensive and slower to develop and can result in
+ "vendor lock-in" with multiple types of management applications.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+4.2.2. BAS Deployment Model
+
+ An example BAS for medium or large buildings is shown in Figure 5.
+ The physical layout spans multiple floors and includes a monitoring
+ room where the BAS management entities are located. Each floor will
+ have one or more LCs, depending on the number of devices connected to
+ the field network.
+
+ +--------------------------------------------------+
+ | Floor 3 |
+ | +----LC~~~~+~~~~~+~~~~~+ |
+ | | | | | |
+ | | Dev Dev Dev |
+ | | |
+ |--- | ------------------------------------------|
+ | | Floor 2 |
+ | +----LC~~~~+~~~~~+~~~~~+ Field Network |
+ | | | | | |
+ | | Dev Dev Dev |
+ | | |
+ |--- | ------------------------------------------|
+ | | Floor 1 |
+ | +----LC~~~~+~~~~~+~~~~~+ +-----------------|
+ | | | | | | Monitoring Room |
+ | | Dev Dev Dev | |
+ | | | BMS HMI |
+ | | Management Network | | | |
+ | +--------------------------------+-----+ |
+ | | |
+ +--------------------------------------------------+
+
+ Figure 5: BAS Deployment Model for Medium/Large Buildings
+
+ Each LC is connected to the monitoring room via the management
+ network, and the management functions are performed within the
+ building. In most cases, Fast Ethernet (e.g., 100BASE-T) is used for
+ the management network. Since the management network is not a
+ real-time network, the use of Ethernet without QoS is sufficient for
+ today's deployments.
+
+ Many physical interfaces used in field networks have specific timing
+ requirements -- for example, RS232C and RS485. Thus, if a field
+ network is to be replaced with an Ethernet or wireless network, such
+ networks must support time-critical deterministic flows.
+
+
+
+
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ Figure 6 shows another deployment model, in which the management
+ system is hosted remotely. This model is becoming popular for small
+ offices and residential buildings, in which a standalone monitoring
+ system is not cost effective.
+
+ +---------------+
+ | Remote Center |
+ | |
+ | BMS HMI |
+ +------------------------------------+ | | | |
+ | Floor 2 | | +---+---+ |
+ | +----LC~~~~+~~~~~+ Field Network| | | |
+ | | | | | | Router |
+ | | Dev Dev | +-------|-------+
+ | | | |
+ |--- | ------------------------------| |
+ | | Floor 1 | |
+ | +----LC~~~~+~~~~~+ | |
+ | | | | | |
+ | | Dev Dev | |
+ | | | |
+ | | Management Network | WAN |
+ | +------------------------Router-------------+
+ | |
+ +------------------------------------+
+
+ Figure 6: Deployment Model for Small Buildings
+
+ Some interoperability is possible in today's management networks but
+ is not possible in today's field networks due to their non-IP-based
+ design.
+
+4.2.3. Use Cases for Field Networks
+
+ Below are use cases for environmental monitoring, fire detection, and
+ feedback control, and their implications for field network
+ performance.
+
+4.2.3.1. Environmental Monitoring
+
+ The BMS polls each LC at a maximum measurement interval of 100 ms
+ (for example, to draw a historical chart of 1-second granularity with
+ a 10x sampling interval) and then performs the operations as
+ specified by the operator. Each LC needs to measure each of its
+ several hundred sensors once per measurement interval. Latency is
+ not critical in this scenario as long as all sensor value
+ measurements are completed within the measurement interval.
+ Availability is expected to be 99.999%.
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+4.2.3.2. Fire Detection
+
+ On detection of a fire, the BMS must stop the HVAC, close the fire
+ shutters, turn on the fire sprinklers, send an alarm, etc. There are
+ typically tens of fire sensors per LC that the BMS needs to manage.
+ In this scenario, the measurement interval is 10-50 ms, the
+ communication delay is 10 ms, and the availability must be 99.9999%.
+
+4.2.3.3. Feedback Control
+
+ BASs utilize feedback control in various ways; the most time-critical
+ is control of DC motors, which require a short feedback interval
+ (1-5 ms) with low communication delay (10 ms) and jitter (1 ms). The
+ feedback interval depends on the characteristics of the device and on
+ the requirements for the control values. There are typically tens of
+ feedback sensors per LC.
+
+ Communication delay is expected to be less than 10 ms and jitter less
+ than 1 ms, while the availability must be 99.9999%.
+
+4.2.4. BAS Security Considerations
+
+ When BAS field networks were developed, it was assumed that the field
+ networks would always be physically isolated from external networks;
+ therefore, security was not a concern. In today's world, many BASs
+ are managed remotely and are thus connected to shared IP networks;
+ therefore, security is a definite concern. Note, however, that
+ security features are not currently available in the majority of BAS
+ field network deployments.
+
+ The management network, being an IP-based network, has the protocols
+ available to enable network security, but in practice many BASs do
+ not implement even such available security features as device
+ authentication or encryption for data in transit.
+
+4.3. BASs in the Future
+
+ In the future, lower energy consumption and environmental monitoring
+ that is more fine-grained will emerge; these will require more
+ sensors and devices, thus requiring larger and more-complex building
+ networks.
+
+ Building networks will be connected to or converged with other
+ networks (enterprise networks, home networks, and the Internet).
+
+ Therefore, better facilities for network management, control,
+ reliability, and security are critical in order to improve resident
+ and operator convenience and comfort. For example, the ability to
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ monitor and control building devices via the Internet would enable
+ (for example) control of room lights or HVAC from a resident's
+ desktop PC or phone application.
+
+4.4. BAS Requests to the IETF
+
+ The community would like to see an interoperable protocol
+ specification that can satisfy the timing, security, availability,
+ and QoS constraints described above, such that the resulting
+ converged network can replace the disparate field networks. Ideally,
+ this connectivity could extend to the open Internet.
+
+ This would imply an architecture that can guarantee
+
+ o Low communication delays (from <10 ms to 100 ms in a network of
+ several hundred devices)
+
+ o Low jitter (<1 ms)
+
+ o Tight feedback intervals (1-10 ms)
+
+ o High network availability (up to 99.9999%)
+
+ o Availability of network data in disaster scenarios
+
+ o Authentication between management devices and field devices (both
+ local and remote)
+
+ o Integrity and data origin authentication of communication data
+ between management devices and field devices
+
+ o Confidentiality of data when communicated to a remote device
+
+5. Wireless for Industrial Applications
+
+5.1. Use Case Description
+
+ Wireless networks are useful for industrial applications -- for
+ example, (1) when portable, fast-moving, or rotating objects are
+ involved and (2) for the resource-constrained devices found in the
+ Internet of Things (IoT).
+
+ Such network-connected sensors, actuators, control loops, etc.
+ typically require that the underlying network support real-time QoS,
+ as well as such specific network properties as reliability,
+ redundancy, and security.
+
+
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ These networks may also contain very large numbers of devices -- for
+ example, for factories, "big data" acquisition, and the IoT. Given
+ the large numbers of devices installed and the potential
+ pervasiveness of the IoT, this is a huge and very cost-sensitive
+ market such that small cost reductions can save large amounts of
+ money.
+
+5.1.1. Network Convergence Using 6TiSCH
+
+ Some wireless network technologies support real-time QoS and are thus
+ useful for these kinds of networks, but others do not.
+
+ This use case focuses on one specific wireless network technology
+ that provides the required deterministic QoS: "IPv6 over the TSCH
+ mode of IEEE 802.15.4e" (6TiSCH, where "TSCH" stands for
+ "Time-Slotted Channel Hopping"; see [Arch-for-6TiSCH], [IEEE-802154],
+ and [RFC7554]).
+
+ There are other deterministic wireless buses and networks available
+ today; however, they are incompatible with each other and with IP
+ traffic (for example, see [ISA100] and [WirelessHART]).
+
+ Thus, the primary goal of this use case is to apply 6TiSCH as a
+ converged IP-based and standards-based wireless network for
+ industrial applications, i.e., to replace multiple proprietary and/or
+ incompatible wireless networking and wireless network management
+ standards.
+
+5.1.2. Common Protocol Development for 6TiSCH
+
+ Today, there are a number of protocols required by 6TiSCH that are
+ still in development. Another goal of this use case is to highlight
+ the ways in which these "missing" protocols share goals in common
+ with DetNet. Thus, it is possible that some of the protocol
+ technology developed for DetNet will also be applicable to 6TiSCH.
+
+ These protocol goals are identified here, along with their
+ relationship to DetNet. It is likely that ultimately the resulting
+ protocols will not be identical but will share design principles that
+ contribute to the efficiency of enabling both DetNet and 6TiSCH.
+
+ One such commonality is that -- although on a different time scale --
+ in both TSN [IEEE-8021TSNTG] and TSCH, a packet that crosses the
+ network from node to node follows a precise schedule, as does a train
+ that leaves intermediate stations at precise times along its path.
+ This kind of operation reduces collisions, saves energy, and enables
+ engineering of the network for deterministic properties.
+
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ Another commonality is remote monitoring and scheduling management of
+ a TSCH network by a Path Computation Element (PCE) and Network
+ Management Entity (NME). The PCE and NME manage timeslots and device
+ resources in a manner that minimizes the interaction with, and the
+ load placed on, resource-constrained devices. For example, a tiny
+ IoT device may have just enough buffers to store one or a few IPv6
+ packets; it will have limited bandwidth between peers such that it
+ can maintain only a small amount of peer information, and it will not
+ be able to store many packets waiting to be forwarded. It is
+ advantageous, then, for the IoT device to only be required to carry
+ out the specific behavior assigned to it by the PCE and NME (as
+ opposed to maintaining its own IP stack, for example).
+
+ It is possible that there will be some peer-to-peer communication;
+ for example, the PCE may communicate only indirectly with some
+ devices in order to enable hierarchical configuration of the system.
+
+ 6TiSCH depends on [PCE] and [DetNet-Arch].
+
+ 6TiSCH also depends on the fact that DetNet will maintain consistency
+ with [IEEE-8021TSNTG].
+
+5.2. Wireless Industrial Today
+
+ Today, industrial wireless technology ("wireless industrial") is
+ accomplished using multiple deterministic wireless networks that are
+ incompatible with each other and with IP traffic.
+
+ 6TiSCH is not yet fully specified, so it cannot be used in today's
+ applications.
+
+5.3. Wireless Industrial in the Future
+
+5.3.1. Unified Wireless Networks and Management
+
+ DetNet and 6TiSCH together can enable converged transport of
+ deterministic and best-effort traffic flows between real-time
+ industrial devices and WANs via IP routing. A high-level view of
+ this type of basic network is shown in Figure 7.
+
+
+
+
+
+
+
+
+
+
+
+
+Grossman Informational [Page 49]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ ---+-------- ............ ------------
+ | External Network |
+ | +-----+
+ +-----+ | NME |
+ | | LLN Border | |
+ | | Router +-----+
+ +-----+
+ o o o
+ o o o o
+ o o LLN o o o
+ o o o o
+ o
+
+ LLN: Low-Power and Lossy Network
+
+ Figure 7: Basic 6TiSCH Network
+
+ Figure 8 shows a backbone router federating multiple synchronized
+ 6TiSCH subnets into a single subnet connected to the external
+ network.
+
+ ---+-------- ............ ------------
+ | External Network |
+ | +-----+
+ | +-----+ | NME |
+ +-----+ | +-----+ | |
+ | | Router | | PCE | +-----+
+ | | +--| |
+ +-----+ +-----+
+ | |
+ | Subnet Backbone |
+ +--------------------+------------------+
+ | | |
+ +-----+ +-----+ +-----+
+ | | Backbone | | Backbone | | Backbone
+ o | | Router | | Router | | Router
+ +-----+ +-----+ +-----+
+ o o o o o
+ o o o o o o o o o o o
+ o o o LLN o o o o
+ o o o o o o o o o o o o
+
+ Figure 8: Extended 6TiSCH Network
+
+
+
+
+
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ The backbone router must ensure end-to-end deterministic behavior
+ between the LLN and the backbone. This should be accomplished in
+ conformance with the work done in [DetNet-Arch] with respect to
+ Layer 3 aspects of deterministic networks that span multiple Layer 2
+ domains.
+
+ The PCE must compute a deterministic path end to end across the TSCH
+ network and IEEE 802.1 TSN Ethernet backbone, and DetNet protocols
+ are expected to enable end-to-end deterministic forwarding.
+
+5.3.1.1. PCE and 6TiSCH ARQ Retries
+
+ 6TiSCH uses the Automatic Repeat reQuest (ARQ) mechanism
+ [IEEE-802154] to provide higher reliability of packet delivery. ARQ
+ is related to Packet Replication and Elimination (PRE) because there
+ are two independent paths for packets to arrive at the destination.
+ If an expected packet does not arrive on one path, then it checks for
+ the packet on the second path.
+
+ Although to date this mechanism is only used by wireless networks,
+ this technique might be appropriate for DetNet, and aspects of the
+ enabling protocol could therefore be co-developed.
+
+ For example, in Figure 9, a track is laid out from a field device in
+ a 6TiSCH network to an IoT gateway that is located on an IEEE 802.1
+ TSN backbone.
+
+ +-----+
+ | IoT |
+ | G/W |
+ +-----+
+ ^ <---- Elimination
+ | |
+ Track Branch | |
+ +-------+ +--------+ Subnet Backbone
+ | |
+ +--|--+ +--|--+
+ | | | Backbone | | | Backbone
+ o | | | Router | | | Router
+ +--/--+ +--|--+
+ o / o o---o----/ o
+ o o---o--/ o o o o o
+ o \ / o o LLN o
+ o v <---- Replication
+ o
+
+ Figure 9: 6TiSCH Network with PRE
+
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ In ARQ, the replication function in the field device sends a copy of
+ each packet over two different branches, and the PCE schedules each
+ hop of both branches so that the two copies arrive in due time at the
+ gateway. In the case of a loss on one branch, one hopes that the
+ other copy of the packet will still arrive within the allocated time.
+ If two copies make it to the IoT gateway, the elimination function in
+ the gateway ignores the extra packet and presents only one copy to
+ upper layers.
+
+ At each 6TiSCH hop along the track, the PCE may schedule more than
+ one timeslot for a packet, so as to support Layer 2 retries (ARQ).
+
+ At the time of this writing, a deployment's TSCH track does not
+ necessarily support PRE but is systematically multipath. This means
+ that a track is scheduled so as to ensure that each hop has at least
+ two forwarding solutions. The forwarding decision will be to try the
+ preferred solution and use the other solution in the case of Layer 2
+ transmission failure as detected by ARQ.
+
+5.3.2. Schedule Management by a PCE
+
+ A common feature of 6TiSCH and DetNet is actions taken by a PCE when
+ configuring paths through the network. Specifically, what is needed
+ is a protocol and data model that the PCE will use to get/set the
+ relevant configuration from/to the devices, as well as perform
+ operations on the devices. Specifically, both DetNet and 6TiSCH need
+ to develop a protocol (and associated data model) that the PCE can
+ use to (1) get/set the relevant configuration from/to the devices and
+ (2) perform operations on the devices. These could be initially
+ developed by DetNet, with consideration for their reuse by 6TiSCH.
+ The remainder of this section provides a bit more context from the
+ 6TiSCH side.
+
+5.3.2.1. PCE Commands and 6TiSCH CoAP Requests
+
+ The 6TiSCH device does not expect to place the request for bandwidth
+ between itself and another device in the network. Rather, an
+ operation control system invoked through a human interface specifies
+ the traffic requirements and the end nodes (in terms of latency and
+ reliability). Based on this information, the PCE must compute a path
+ between the end nodes and provision the network with per-flow state
+ that describes the per-hop operation for a given packet, the
+ corresponding timeslots, the flow identification that enables
+ recognizing that a certain packet belongs to a certain path, etc.
+
+ For a static configuration that serves a certain purpose for a long
+ period of time, it is expected that a node will be provisioned in one
+ shot with a full schedule, i.e., a schedule that defines the behavior
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ of the node with respect to all data flows through that node. 6TiSCH
+ expects that the programming of the schedule will be done over the
+ Constrained Application Protocol (CoAP) as discussed in
+ [CoAP-6TiSCH].
+
+ 6TiSCH expects that the PCE commands will be mapped back and forth
+ into CoAP by a gateway function at the edge of the 6TiSCH network.
+ For instance, it is possible that a mapping entity on the backbone
+ transforms a non-CoAP protocol such as the Path Computation Element
+ Communication Protocol (PCEP) into the RESTful interfaces that the
+ 6TiSCH devices support. This architecture will be refined to comply
+ with DetNet [DetNet-Arch] when the work is formalized. Related
+ information about 6TiSCH can be found in [Interface-6TiSCH-6top] and
+ [RFC6550] ("RPL: IPv6 Routing Protocol for Low-Power and Lossy
+ Networks").
+
+ A protocol may be used to update the state in the devices during
+ runtime -- for example, if it appears that a path through the network
+ has ceased to perform as expected, but in 6TiSCH that flow was not
+ designed and no protocol was selected. DetNet should define the
+ appropriate end-to-end protocols to be used in that case. The
+ implication is that these state updates take place once the system is
+ configured and running, i.e., they are not limited to the initial
+ communication of the configuration of the system.
+
+ A "slotFrame" is the base object that a PCE would manipulate to
+ program a schedule into an LLN node [Arch-for-6TiSCH].
+
+ The PCE should read energy data from devices and compute paths that
+ will implement policies on how energy in devices is consumed -- for
+ instance, to ensure that the spent energy does not exceed the
+ available energy over a period of time. Note that this statement
+ implies that an extensible protocol for communicating device
+ information to the PCE and enabling the PCE to act on it will be part
+ of the DetNet architecture; however, for subnets with specific
+ protocols (e.g., CoAP), a gateway may be required.
+
+ 6TiSCH devices can discover their neighbors over the radio using a
+ mechanism such as beacons, but even though the neighbor information
+ is available in the 6TiSCH interface data model, 6TiSCH does not
+ describe a protocol to proactively push the neighbor information to a
+ PCE. DetNet should define such a protocol; one possible design
+ alternative is that it could operate over CoAP. Alternatively, it
+ could be converted to/from CoAP by a gateway. Such a protocol could
+ carry multiple metrics -- for example, metrics similar to those used
+ for RPL operations [RFC6551].
+
+
+
+
+
+Grossman Informational [Page 53]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+5.3.2.2. 6TiSCH IP Interface
+
+ Protocol translation between the TSCH MAC layer and IP is
+ accomplished via the "6top" sublayer [Sublayer-6TiSCH-6top]. The
+ 6top data model and management interfaces are further discussed in
+ [Interface-6TiSCH-6top] and [CoAP-6TiSCH].
+
+ An IP packet that is sent along a 6TiSCH path uses a differentiated
+ services Per-Hop Behavior Group (PHB) called "deterministic
+ forwarding", as described in [Det-Fwd-PHB].
+
+5.3.3. 6TiSCH Security Considerations
+
+ In addition to the classical requirements for protection of control
+ signaling, it must be noted that 6TiSCH networks operate on limited
+ resources that can be depleted rapidly in a DoS attack on the system
+ -- for instance, by placing a rogue device in the network or by
+ obtaining management control and setting up unexpected additional
+ paths.
+
+5.4. Wireless Industrial Requests to the IETF
+
+ 6TiSCH depends on DetNet to define:
+
+ o Configuration (state) and operations for deterministic paths
+
+ o End-to-end protocols for deterministic forwarding (tagging, IP)
+
+ o A protocol for PRE
+
+6. Cellular Radio
+
+6.1. Use Case Description
+
+ This use case describes the application of deterministic networking
+ in the context of cellular telecom transport networks. Important
+ elements include time synchronization, clock distribution, and ways
+ to establish time-sensitive streams for both Layer 2 and Layer 3
+ user-plane traffic.
+
+6.1.1. Network Architecture
+
+ Figure 10 illustrates a 3GPP-defined cellular network architecture
+ typical at the time of this writing. The architecture includes
+ "Fronthaul", "Midhaul", and "Backhaul" network segments. The
+ "Fronthaul" is the network connecting base stations (Baseband Units
+ (BBUs)) to the Remote Radio Heads (RRHs) (also referred to here as
+ "antennas"). The "Midhaul" is the network that interconnects base
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ stations (or small-cell sites). The "Backhaul" is the network or
+ links connecting the radio base station sites to the network
+ controller/gateway sites (i.e., the core of the 3GPP cellular
+ network).
+
+ Y (RRHs (antennas))
+ \
+ Y__ \.--. .--. +------+
+ \_( `. +---+ _( `. | 3GPP |
+ Y------( Front- )----|eNB|----( Back- )------| core |
+ ( ` .haul ) +---+ ( ` .haul) ) | netw |
+ /`--(___.-' \ `--(___.-' +------+
+ Y_/ / \.--. \
+ Y_/ _(Mid-`. \
+ ( haul ) \
+ ( ` . ) ) \
+ `--(___.-'\_____+---+ (small-cell sites)
+ \ |SCe|__Y
+ +---+ +---+
+ Y__|eNB|__Y
+ +---+
+ Y_/ \_Y ("local" radios)
+
+ Figure 10: Generic 3GPP-Based Cellular Network Architecture
+
+ In Figure 10, "eNB" ("E-UTRAN Node B") is the hardware that is
+ connected to the mobile phone network and enables the mobile phone
+ network to communicate with mobile handsets [TS36300]. ("E-UTRAN"
+ stands for "Evolved Universal Terrestrial Radio Access Network".)
+
+6.1.2. Delay Constraints
+
+ The available processing time for Fronthaul networking overhead is
+ limited to the available time after the baseband processing of the
+ radio frame has completed. For example, in Long Term Evolution (LTE)
+ radio, 3 ms is allocated for the processing of a radio frame, but
+ typically the baseband processing uses most of it, allowing only a
+ small fraction to be used by the Fronthaul network. In this example,
+ out of 3 ms, the maximum time allocated to the Fronthaul network for
+ one-way delay is 250 us, and the existing specification [NGMN-Fronth]
+ specifies a maximum delay of only 100 us. This ultimately determines
+ the distance the RRHs can be located from the base stations (e.g.,
+ 100 us equals roughly 20 km of optical fiber-based transport).
+ Allocation options regarding the available time budget between
+ processing and transport are currently undergoing heavy discussion in
+ the mobile industry.
+
+
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ For packet-based transport, the allocated transport time between the
+ RRH and the BBU is consumed by node processing, buffering, and
+ distance-incurred delay. An example of the allocated transport time
+ is 100 us (from the Common Public Radio Interface [CPRI]).
+
+ The baseband processing time and the available "delay budget" for the
+ Fronthaul is likely to change in the forthcoming "5G" due to reduced
+ radio round-trip times and other architectural and service
+ requirements [NGMN].
+
+ The transport time budget, as noted above, places limitations on the
+ distance that RRHs can be located from base stations (i.e., the link
+ length). In the above analysis, it is assumed that the entire
+ transport time budget is available for link propagation delay.
+ However, the transport time budget can be broken down into three
+ components: scheduling/queuing delay, transmission delay, and link
+ propagation delay. Using today's Fronthaul networking technology,
+ the queuing, scheduling, and transmission components might become the
+ dominant factors in the total transport time, rather than the link
+ propagation delay. This is especially true in cases where the
+ Fronthaul link is relatively short and is shared among multiple
+ Fronthaul flows -- for example, in indoor and small-cell networks,
+ massive Multiple Input Multiple Output (MIMO) antenna networks, and
+ split Fronthaul architectures.
+
+ DetNet technology can improve Fronthaul networks by controlling and
+ reducing the time required for the queuing, scheduling, and
+ transmission operations by properly assigning network resources, thus
+ (1) leaving more of the transport time budget available for link
+ propagation and (2) enabling longer link lengths. However, link
+ length is usually a predetermined parameter and is not a controllable
+ network parameter, since RRH and BBU sites are usually located in
+ predetermined locations. However, the number of antennas in an RRH
+ site might increase -- for example, by adding more antennas,
+ increasing the MIMO capability of the network, or adding support for
+ massive MIMO. This means increasing the number of Fronthaul flows
+ sharing the same Fronthaul link. DetNet can now control the
+ bandwidth assignment of the Fronthaul link and the scheduling of
+ Fronthaul packets over this link and can provide adequate buffer
+ provisioning for each flow to reduce the packet loss rate.
+
+ Another way in which DetNet technology can aid Fronthaul networks is
+ by providing effective isolation between flows -- for example,
+ between flows originating in different slices within a network-sliced
+ 5G network. Note, however, that this isolation applies to DetNet
+ flows for which resources have been preallocated, i.e., it does not
+ apply to best-effort flows within a DetNet. DetNet technology can
+ also dynamically control the bandwidth-assignment, scheduling, and
+
+
+
+Grossman Informational [Page 56]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ packet-forwarding decisions, as well as the buffer provisioning of
+ the Fronthaul flows to guarantee the end-to-end delay of the
+ Fronthaul packets and minimize the packet loss rate.
+
+ [METIS] documents the fundamental challenges as well as overall
+ technical goals of the future 5G mobile and wireless systems as the
+ starting point. These future systems should support much higher data
+ volumes and rates and significantly lower end-to-end latency for 100x
+ more connected devices (at cost and energy-consumption levels similar
+ to today's systems).
+
+ For Midhaul connections, delay constraints are driven by inter-site
+ radio functions such as Coordinated Multi-Point (CoMP) processing
+ (see [CoMP]). CoMP reception and transmission constitute a framework
+ in which multiple geographically distributed antenna nodes cooperate
+ to improve performance for the users served in the common cooperation
+ area. The design principle of CoMP is to extend single-cell-to-
+ multi-UE (User Equipment) transmission to a multi-cell-to-multi-UE
+ transmission via cooperation among base stations.
+
+ CoMP has delay-sensitive performance parameters: "Midhaul latency"
+ and "CSI (Channel State Information) reporting and accuracy". The
+ essential feature of CoMP is signaling between eNBs, so Midhaul
+ latency is the dominating limitation of CoMP performance. Generally,
+ CoMP can benefit from coordinated scheduling (either distributed or
+ centralized) of different cells if the signaling delay between eNBs
+ is within 1-10 ms. This delay requirement is both rigid and
+ absolute, because any uncertainty in delay will degrade performance
+ significantly.
+
+ Inter-site CoMP is one of the key requirements for 5G and is also a
+ goal for 4.5G network architectures.
+
+6.1.3. Time-Synchronization Constraints
+
+ Fronthaul time-synchronization requirements are given by [TS25104],
+ [TS36104], [TS36211], and [TS36133]. These can be summarized for the
+ 3GPP LTE-based networks as:
+
+ Delay accuracy:
+ +-8 ns (i.e., +-1/32 Tc, where Tc is the Universal Mobile
+ Telecommunications System (UMTS) Chip time of 1/3.84 MHz),
+ resulting in a round-trip accuracy of +-16 ns. The value is this
+ low in order to meet the 3GPP Timing Alignment Error (TAE)
+ measurement requirements. Note that performance guarantees of
+ low-nanosecond values such as these are considered to be below the
+ DetNet layer -- it is assumed that the underlying implementation
+ (e.g., the hardware) will provide sufficient support (e.g.,
+
+
+
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+
+
+ buffering) to enable this level of accuracy. These values are
+ maintained in the use case to give an indication of the overall
+ application.
+
+ TAE:
+ TAE is problematic for Fronthaul networks and must be minimized.
+ If the transport network cannot guarantee TAE levels that are low
+ enough, then additional buffering has to be introduced at the
+ edges of the network to buffer out the jitter. Buffering is not
+ desirable, as it reduces the total available delay budget.
+
+ Packet Delay Variation (PDV) requirements can be derived from TAE
+ measurements for packet-based Fronthaul networks.
+
+ * For MIMO or TX diversity transmissions, at each carrier
+ frequency, TAE measurements shall not exceed 65 ns (i.e.,
+ 1/4 Tc).
+
+ * For intra-band contiguous carrier aggregation, with or without
+ MIMO or TX diversity, TAE measurements shall not exceed 130 ns
+ (i.e., 1/2 Tc).
+
+ * For intra-band non-contiguous carrier aggregation, with or
+ without MIMO or TX diversity, TAE measurements shall not exceed
+ 260 ns (i.e., 1 Tc).
+
+ * For inter-band carrier aggregation, with or without MIMO or TX
+ diversity, TAE measurements shall not exceed 260 ns.
+
+ Transport link contribution to radio frequency errors:
+ +-2 PPB. This value is considered to be "available" for the
+ Fronthaul link out of the total 50 PPB budget reserved for the
+ radio interface. Note that the transport link contributes to
+ radio frequency errors for the following reason: at the time of
+ this writing, Fronthaul communication is direct communication from
+ the radio unit to the RRH. The RRH is essentially a passive
+ device (e.g., without buffering). The transport drives the
+ antenna directly by feeding it with samples, and everything the
+ transport adds will be introduced to the radio "as is". So, if
+ the transport causes any additional frequency errors, the errors
+ will show up immediately on the radio as well. Note that
+ performance guarantees of low-nanosecond values such as these are
+ considered to be below the DetNet layer -- it is assumed that the
+ underlying implementation (e.g., the hardware) will provide
+ sufficient support to enable this level of performance. These
+ values are maintained in the use case to give an indication of the
+ overall application.
+
+
+
+
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+
+
+ The above-listed time-synchronization requirements are difficult to
+ meet with point-to-point connected networks and are more difficult to
+ meet when the network includes multiple hops. It is expected that
+ networks must include buffering at the ends of the connections as
+ imposed by the jitter requirements, since trying to meet the jitter
+ requirements in every intermediate node is likely to be too costly.
+ However, every measure to reduce jitter and delay on the path makes
+ it easier to meet the end-to-end requirements.
+
+ In order to meet the timing requirements, both senders and receivers
+ must remain time synchronized, demanding very accurate clock
+ distribution -- for example, support for IEEE 1588 transparent clocks
+ or boundary clocks in every intermediate node.
+
+ In cellular networks from the LTE radio era onward, phase
+ synchronization is needed in addition to frequency synchronization
+ [TS36300] [TS23401]. Time constraints are also important due to
+ their impact on packet loss. If a packet is delivered too late, then
+ the packet may be dropped by the host.
+
+6.1.4. Transport-Loss Constraints
+
+ Fronthaul and Midhaul networks assume that transport is almost
+ error free. Errors can cause a reset of the radio interfaces, in
+ turn causing reduced throughput or broken radio connectivity for
+ mobile customers.
+
+ For packetized Fronthaul and Midhaul connections, packet loss may be
+ caused by BER, congestion, or network failure scenarios. Different
+ Fronthaul "functional splits" are being considered by 3GPP, requiring
+ strict Frame Loss Ratio (FLR) guarantees. As one example (referring
+ to the legacy CPRI split, which is option 8 in 3GPP), lower-layer
+ splits may imply an FLR of less than 10^-7 for data traffic and less
+ than 10^-6 for control and management traffic.
+
+ Many of the tools available for eliminating packet loss for Fronthaul
+ and Midhaul networks have serious challenges; for example,
+ retransmitting lost packets or using FEC to circumvent bit errors (or
+ both) is practically impossible, due to the additional delay
+ incurred. Using redundant streams for better guarantees of delivery
+ is also practically impossible in many cases, due to high bandwidth
+ requirements for Fronthaul and Midhaul networks. Protection
+ switching is also a candidate, but at the time of this writing,
+ available technologies for the path switch are too slow to avoid a
+ reset of mobile interfaces.
+
+
+
+
+
+
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+
+
+ It is assumed that Fronthaul links are symmetric. All Fronthaul
+ streams (i.e., those carrying radio data) have equal priority and
+ cannot delay or preempt each other.
+
+ All of this implies that it is up to the network to guarantee that
+ each time-sensitive flow meets its schedule.
+
+6.1.5. Cellular Radio Network Security Considerations
+
+ Establishing time-sensitive streams in the network entails reserving
+ networking resources for long periods of time. It is important that
+ these reservation requests be authenticated to prevent malicious
+ reservation attempts from hostile nodes (or accidental
+ misconfiguration). This is particularly important in the case where
+ the reservation requests span administrative domains. Furthermore,
+ the reservation information itself should be digitally signed to
+ reduce the risk of a legitimate node pushing a stale or hostile
+ configuration into another networking node.
+
+ Note: This is considered important for the security policy of the
+ network but does not affect the core DetNet architecture and design.
+
+6.2. Cellular Radio Networks Today
+
+6.2.1. Fronthaul
+
+ Today's Fronthaul networks typically consist of:
+
+ o Dedicated point-to-point fiber connection (common)
+
+ o Proprietary protocols and framings
+
+ o Custom equipment and no real networking
+
+ At the time of this writing, solutions for Fronthaul are direct
+ optical cables or Wavelength-Division Multiplexing (WDM) connections.
+
+6.2.2. Midhaul and Backhaul
+
+ Today's Midhaul and Backhaul networks typically consist of:
+
+ o Mostly normal IP networks, MPLS-TP, etc.
+
+ o Clock distribution and synchronization using IEEE 1588 and syncE
+
+ Telecommunications networks in the Midhaul and Backhaul are already
+ heading towards transport networks where precise time-synchronization
+ support is one of the basic building blocks. In order to meet
+
+
+
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+
+
+ bandwidth and cost requirements, most transport networks have already
+ transitioned to all-IP packet-based networks; however, highly
+ accurate clock distribution has become a challenge.
+
+ In the past, Midhaul and Backhaul connections were typically based on
+ TDM and provided frequency-synchronization capabilities as a part of
+ the transport media. More recently, other technologies such as GPS
+ or syncE [syncE] have been used.
+
+ Ethernet, IP/MPLS [RFC3031], and pseudowires (as described in
+ [RFC3985] ("Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture")
+ for legacy transport support)) have become popular tools for building
+ and managing new all-IP Radio Access Networks (RANs)
+ [SR-IP-RAN-Use-Case]. Although various timing and synchronization
+ optimizations have already been proposed and implemented, including
+ PTP enhancements [IEEE-1588] (see also [Timing-over-MPLS] and
+ [RFC8169]), these solutions are not necessarily sufficient for the
+ forthcoming RAN architectures, nor do they guarantee the more
+ stringent time-synchronization requirements such as [CPRI].
+
+ Existing solutions for TDM over IP include those discussed in
+ [RFC4553], [RFC5086], and [RFC5087]; [MEF8] addresses TDM over
+ Ethernet transports.
+
+6.3. Cellular Radio Networks in the Future
+
+ Future cellular radio networks will be based on a mix of different
+ xHaul networks (xHaul = Fronthaul, Midhaul, and Backhaul), and future
+ transport networks should be able to support all of them
+ simultaneously. It is already envisioned today that:
+
+ o Not all "cellular radio network" traffic will be IP; for example,
+ some will remain at Layer 2 (e.g., Ethernet based). DetNet
+ solutions must address all traffic types (Layer 2 and Layer 3)
+ with the same tools and allow their transport simultaneously.
+
+ o All types of xHaul networks will need some types of DetNet
+ solutions. For example, with the advent of 5G, some Backhaul
+ traffic will also have DetNet requirements (for example, traffic
+ belonging to time-critical 5G applications).
+
+ o Different functional splits between the base stations and the
+ on-site units could coexist on the same Fronthaul and Backhaul
+ network.
+
+
+
+
+
+
+
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+
+
+ Future cellular radio networks should contain the following:
+
+ o Unified standards-based transport protocols and standard
+ networking equipment that can make use of underlying deterministic
+ link-layer services
+
+ o Unified and standards-based network management systems and
+ protocols in all parts of the network (including Fronthaul)
+
+ New RAN deployment models and architectures may require TSN services
+ with strict requirements on other parts of the network that
+ previously were not considered to be packetized at all. Time and
+ synchronization support are already topical for Backhaul and Midhaul
+ packet networks [MEF22.1.1] and are also becoming a real issue for
+ Fronthaul networks. Specifically, in Fronthaul networks, the timing
+ and synchronization requirements can be extreme for packet-based
+ technologies -- for example, on the order of a PDV of +-20 ns or less
+ and frequency accuracy of +-0.002 PPM [Fronthaul].
+
+ The actual transport protocols and/or solutions for establishing
+ required transport "circuits" (pinned-down paths) for Fronthaul
+ traffic are still undefined. Those protocols are likely to include
+ (but are not limited to) solutions directly over Ethernet, over IP,
+ and using MPLS/pseudowire transport.
+
+ Interesting and important work for TSN has been done for Ethernet
+ [IEEE-8021TSNTG]; this work specifies the use of PTP [IEEE-1588] in
+ the context of IEEE 802.1D and IEEE 802.1Q. [IEEE-8021AS] specifies
+ a Layer 2 time-synchronizing service, and other specifications such
+ as IEEE 1722 [IEEE-1722] specify Ethernet-based Layer 2 transport for
+ time-sensitive streams.
+
+ However, even these Ethernet TSN features may not be sufficient for
+ Fronthaul traffic. Therefore, having specific profiles that take
+ Fronthaul requirements into account is desirable [IEEE-8021CM].
+
+ New promising work seeks to enable the transport of time-sensitive
+ Fronthaul streams in Ethernet bridged networks [IEEE-8021CM].
+ Analogous to IEEE 1722, standardization efforts in the IEEE 1914.3
+ Task Force [IEEE-19143] to define the Layer 2 transport encapsulation
+ format for transporting Radio over Ethernet (RoE) are ongoing.
+
+ As mentioned in Section 6.1.2, 5G communications will provide one of
+ the most challenging cases for delay-sensitive networking. In order
+ to meet the challenges of ultra-low latency and ultra-high
+ throughput, 3GPP has studied various functional splits for 5G, i.e.,
+ physical decomposition of the 5G "gNodeB" base station and deployment
+ of its functional blocks in different locations [TR38801].
+
+
+
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+
+
+ These splits are numbered from split option 1 (dual connectivity, a
+ split in which the radio resource control is centralized and other
+ radio stack layers are in distributed units) to split option 8 (a
+ PHY-RF split in which RF functionality is in a distributed unit and
+ the rest of the radio stack is in the centralized unit), with each
+ intermediate split having its own data-rate and delay requirements.
+ Packetized versions of different splits have been proposed, including
+ enhanced CPRI (eCPRI) [eCPRI] and RoE (as previously noted). Both
+ provide Ethernet encapsulations, and eCPRI is also capable of IP
+ encapsulation.
+
+ All-IP RANs and xHaul networks would benefit from time
+ synchronization and time-sensitive transport services. Although
+ Ethernet appears to be the unifying technology for the transport,
+ there is still a disconnect when it comes to providing Layer 3
+ services. The protocol stack typically has a number of layers below
+ Ethernet Layer 2 that might be "visible" to Layer 3. In a fairly
+ common scenario, on top of the lowest-layer (optical) transport is
+ the first (lowest) Ethernet layer, then one or more layers of MPLS,
+ pseudowires, and/or other tunneling protocols, and finally one or
+ more Ethernet layers that are visible to Layer 3.
+
+ Although there exist technologies for establishing circuits through
+ the routed and switched networks (especially in the MPLS/PWE space),
+ there is still no way to signal the time-synchronization and
+ time-sensitive stream requirements/reservations for Layer 3 flows in
+ a way that addresses the entire transport stack, including the
+ Ethernet layers that need to be configured.
+
+ Furthermore, not all "user-plane" traffic will be IP. Therefore, the
+ solution in question also must address the use cases where the
+ user-plane traffic is on a different layer (for example, Ethernet
+ frames).
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
+
+6.4. Cellular Radio Networks Requests to the IETF
+
+ A standard for data-plane transport specifications that is:
+
+ o Unified among all xHauls (meaning that different flows with
+ diverse DetNet requirements can coexist in the same network and
+ traverse the same nodes without interfering with each other)
+
+ o Deployed in a highly deterministic network environment
+
+ o Capable of supporting multiple functional splits simultaneously,
+ including existing Backhaul and CPRI Fronthaul, and (potentially)
+ new modes as defined, for example, in 3GPP; these goals can be
+ supported by the existing DetNet use case "common themes"
+ (Section 11); of special note are Sections 11.1.8 ("Mix of
+ Deterministic and Best-Effort Traffic"), 11.3.1 ("Bounded
+ Latency"), 11.3.2 ("Low Latency"), 11.3.4 ("Symmetrical Path
+ Delays"), and 11.6 ("Deterministic Flows")
+
+ o Capable of supporting network slicing and multi-tenancy; these
+ goals can be supported by the same DetNet themes noted above
+
+ o Capable of transporting both in-band and out-of-band control
+ traffic (e.g., Operations, Administration, and Maintenance (OAM)
+ information)
+
+ o Deployable over multiple data-link technologies (e.g., IEEE 802.3,
+ mmWave)
+
+ A standard for data-flow information models that is:
+
+ o Aware of the time sensitivity and constraints of the target
+ networking environment
+
+ o Aware of underlying deterministic networking services (e.g., on
+ the Ethernet layer)
+
+7. Industrial Machine to Machine (M2M)
+
+7.1. Use Case Description
+
+ "Industrial automation" in general refers to automation of
+ manufacturing, quality control, and material processing. This M2M
+ use case focuses on machine units on a plant floor that periodically
+ exchange data with upstream or downstream machine modules and/or a
+ supervisory controller within a LAN.
+
+
+
+
+
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+
+
+ PLCs are the "actors" in M2M communications. Communication between
+ PLCs, and between PLCs and the supervisory PLC (S-PLC), is achieved
+ via critical control/data streams (Figure 11).
+
+ S (Sensor)
+ \ +-----+
+ PLC__ \.--. .--. ---| MES |
+ \_( `. _( `./ +-----+
+ A------( Local )-------------( L2 )
+ ( Net ) ( Net ) +-------+
+ /`--(___.-' `--(___.-' ----| S-PLC |
+ S_/ / PLC .--. / +-------+
+ A_/ \_( `.
+ (Actuator) ( Local )
+ ( Net )
+ /`--(___.-'\
+ / \ A
+ S A
+
+ Figure 11: Current Generic Industrial M2M Network Architecture
+
+ This use case focuses on PLC-related communications; communication to
+ Manufacturing Execution Systems (MESs) are not addressed.
+
+ This use case covers only critical control/data streams; non-critical
+ traffic between industrial automation applications (such as
+ communication of state, configuration, setup, and database
+ communication) is adequately served by prioritizing techniques
+ available at the time of this writing. Such traffic can use up to
+ 80% of the total bandwidth required. There is also a subset of
+ non-time-critical traffic that must be reliable even though it is not
+ time sensitive.
+
+ In this use case, deterministic networking is primarily needed to
+ provide end-to-end delivery of M2M messages within specific timing
+ constraints -- for example, in closed-loop automation control.
+ Today, this level of determinism is provided by proprietary
+ networking technologies. In addition, standard networking
+ technologies are used to connect the local network to remote
+ industrial automation sites, e.g., over an enterprise or metro
+ network that also carries other types of traffic. Therefore, flows
+ that should be forwarded with deterministic guarantees need to be
+ sustained, regardless of the amount of other flows in those networks.
+
+
+
+
+
+
+
+
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+
+
+7.2. Industrial M2M Communications Today
+
+ Today, proprietary networks fulfill the needed timing and
+ availability for M2M networks.
+
+ The network topologies used today by industrial automation are
+ similar to those used by telecom networks: daisy chain, ring,
+ hub-and-spoke, and "comb" (a subset of daisy chain).
+
+ PLC-related control/data streams are transmitted periodically and
+ carry either a preconfigured payload or a payload configured during
+ runtime.
+
+ Some industrial applications require time synchronization at the end
+ nodes. For such time-coordinated PLCs, accuracy of 1 us is required.
+ Even in the case of "non-time-coordinated" PLCs, time synchronization
+ may be needed, e.g., for timestamping of sensor data.
+
+ Industrial-network scenarios require advanced security solutions. At
+ the time of this writing, many industrial production networks are
+ physically separated. Filtering policies that are typically enforced
+ in firewalls are used to prevent critical flows from being leaked
+ outside a domain.
+
+7.2.1. Transport Parameters
+
+ The cycle time defines the frequency of message(s) between industrial
+ actors. The cycle time is application dependent, in the range of
+ 1-100 ms for critical control/data streams.
+
+ Because industrial applications assume that deterministic transport
+ will be used for critical control-data-stream parameters (instead of
+ having to define latency and delay-variation parameters), it is
+ sufficient to fulfill requirements regarding the upper bound of
+ latency (maximum latency). The underlying networking infrastructure
+ must ensure a maximum end-to-end message delivery time in the range
+ of 100 us to 50 ms, depending on the control-loop application.
+
+ The bandwidth requirements of control/data streams are usually
+ calculated directly from the bytes-per-cycle parameter of the control
+ loop. For PLC-to-PLC communication, one can expect 2-32 streams with
+ packet sizes in the range of 100-700 bytes. For S-PLC-to-PLC
+ communication, the number of streams is higher -- up to 256 streams.
+ Usually, no more than 20% of available bandwidth is used for
+ critical control/data streams. In today's networks, 1 Gbps links
+ are commonly used.
+
+
+
+
+
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+
+
+ Most PLC control loops are rather tolerant of packet loss; however,
+ critical control/data streams accept a loss of no more than one
+ packet per consecutive communication cycle (i.e., if a packet gets
+ lost in cycle "n", then the next cycle ("n+1") must be lossless).
+ After the loss of two or more consecutive packets, the network may be
+ considered to be "down" by the application.
+
+ As network downtime may impact the whole production system, the
+ required network availability is rather high (99.999%).
+
+ Based on the above parameters, some form of redundancy will be
+ required for M2M communications; however, any individual solution
+ depends on several parameters, including cycle time and
+ delivery time.
+
+7.2.2. Stream Creation and Destruction
+
+ In an industrial environment, critical control/data streams are
+ created rather infrequently, on the order of ~10 times per
+ day/week/month. Most of these critical control/data streams get
+ created at machine startup; however, flexibility is also needed
+ during runtime -- for example, when adding or removing a machine. As
+ production systems become more flexible going forward, there will be
+ a significant increase in the rate at which streams are created,
+ changed, and destroyed.
+
+7.3. Industrial M2M in the Future
+
+ We foresee a converged IP-standards-based network with deterministic
+ properties that can satisfy the timing, security, and reliability
+ constraints described above. Today's proprietary networks could then
+ be interfaced to such a network via gateways; alternatively, in the
+ case of new installations, devices could be connected directly to the
+ converged network.
+
+ For this use case, time-synchronization accuracy on the order of 1 us
+ is expected.
+
+7.4. Industrial M2M Requests to the IETF
+
+ o Converged IP-based network
+
+ o Deterministic behavior (bounded latency and jitter)
+
+ o High availability (presumably through redundancy) (99.999%)
+
+ o Low message delivery time (100 us to 50 ms)
+
+
+
+
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+
+
+ o Low packet loss (with a bounded number of consecutive lost
+ packets)
+
+ o Security (e.g., preventing critical flows from being leaked
+ between physically separated networks)
+
+8. Mining Industry
+
+8.1. Use Case Description
+
+ The mining industry is highly dependent on networks to monitor and
+ control their systems, in both open-pit and underground extraction as
+ well as in transport and refining processes. In order to reduce
+ risks and increase operational efficiency in mining operations, the
+ location of operators has been relocated (as much as possible) from
+ the extraction site to remote control and monitoring sites.
+
+ In the case of open-pit mining, autonomous trucks are used to
+ transport the raw materials from the open pit to the refining factory
+ where the final product (e.g., copper) is obtained. Although the
+ operation is autonomous, the tracks are remotely monitored from a
+ central facility.
+
+ In pit mines, the monitoring of the tailings or mine dumps is
+ critical in order to minimize environmental pollution. In the past,
+ monitoring was conducted through manual inspection of preinstalled
+ dataloggers. Cabling is not typically used in such scenarios, due to
+ its high cost and complex deployment requirements. At the time of
+ this writing, wireless technologies are being employed to monitor
+ these cases permanently. Slopes are also monitored in order to
+ anticipate possible mine collapse. Due to the unstable terrain,
+ cable maintenance is costly and complex; hence, wireless technologies
+ are employed.
+
+ In the case of underground monitoring, autonomous vehicles with
+ extraction tools travel independently through the tunnels, but their
+ operational tasks (such as excavation, stone-breaking, and transport)
+ are controlled remotely from a central facility. This generates
+ upstream video and feedback traffic plus downstream actuator-control
+ traffic.
+
+8.2. Mining Industry Today
+
+ At the time of this writing, the mining industry uses a
+ packet-switched architecture supported by high-speed Ethernet.
+ However, in order to comply with requirements regarding delay and
+ packet loss, the network bandwidth is overestimated. This results in
+ very low efficiency in terms of resource usage.
+
+
+
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+
+
+ QoS is implemented at the routers to separate video, management,
+ monitoring, and process-control traffic for each stream.
+
+ Since mobility is involved in this process, the connections between
+ the backbone and the mobile devices (e.g., trucks, trains, and
+ excavators) are implemented using a wireless link. These links are
+ based on IEEE 802.11 [IEEE-80211] for open-pit mining and "leaky
+ feeder" communications for underground mining. (A "leaky feeder"
+ communication system consists of a coaxial cable, run along tunnels,
+ that emits and receives radio waves, functioning as an extended
+ antenna. The cable is "leaky" in that it has gaps or slots in its
+ outer conductor to allow the radio signal to leak into or out of the
+ cable along its entire length.)
+
+ Lately, in pit mines the use of Low-Power WAN (LPWAN) technologies
+ has been extended: tailings, slopes, and mine dumps are monitored by
+ battery-powered dataloggers that make use of robust long-range radio
+ technologies. Reliability is usually ensured through retransmissions
+ at Layer 2. Gateways or concentrators act as bridges, forwarding the
+ data to the backbone Ethernet network. Deterministic requirements
+ are biased towards reliability rather than latency, as events are
+ triggered slowly or can be anticipated in advance.
+
+ At the mineral-processing stage, conveyor belts and refining
+ processes are controlled by a SCADA system that provides an
+ in-factory delay-constrained networking environment.
+
+ At the time of this writing, voice communications are served by a
+ redundant trunking infrastructure, independent from data networks.
+
+8.3. Mining Industry in the Future
+
+ Mining operations and management are converging towards a combination
+ of autonomous operation and teleoperation of transport and extraction
+ machines. This means that video, audio, monitoring, and process-
+ control traffic will increase dramatically. Ideally, all activities
+ at the mine will rely on network infrastructure.
+
+ Wireless for open-pit mining is already a reality with LPWAN
+ technologies; it is expected to evolve to more-advanced LPWAN
+ technologies, such as those based on LTE, to increase last-hop
+ reliability or novel LPWAN flavors with deterministic access.
+
+ One area in which DetNet can improve this use case is in the wired
+ networks that make up the "backbone network" of the system. These
+ networks connect many wireless Access Points (APs) together. The
+ mobile machines (which are connected to the network via wireless)
+
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ transition from one AP to the next as they move about. A
+ deterministic, reliable, low-latency backbone can enable these
+ transitions to be more reliable.
+
+ Connections that extend all the way from the base stations to the
+ machinery via a mix of wired and wireless hops would also be
+ beneficial -- for example, to improve the responsiveness of digging
+ machines to remote control. However, to guarantee deterministic
+ performance of a DetNet, the end-to-end underlying network must be
+ deterministic. Thus, for this use case, if a deterministic wireless
+ transport is integrated with a wire-based DetNet network, it could
+ create the desired wired plus wireless end-to-end deterministic
+ network.
+
+8.4. Mining Industry Requests to the IETF
+
+ o Improved bandwidth efficiency
+
+ o Very low delay, to enable machine teleoperation
+
+ o Dedicated bandwidth usage for high-resolution video streams
+
+ o Predictable delay, to enable real-time monitoring
+
+ o Potential for constructing a unified DetNet network over a
+ combination of wired and deterministic wireless links
+
+9. Private Blockchain
+
+9.1. Use Case Description
+
+ Blockchain was created with Bitcoin as a "public" blockchain on the
+ open Internet; however, blockchain has also spread far beyond its
+ original host into various industries, such as smart manufacturing,
+ logistics, security, legal rights, and others. In these industries,
+ blockchain runs in designated and carefully managed networks in which
+ deterministic networking requirements could be addressed by DetNet.
+ Such implementations are referred to as "private" blockchain.
+
+ The sole distinction between public and private blockchain is defined
+ by who is allowed to participate in the network, execute the
+ consensus protocol, and maintain the shared ledger.
+
+ Today's networks manage the traffic from blockchain on a best-effort
+ basis, but blockchain operation could be made much more efficient if
+ deterministic networking services were available to minimize latency
+ and packet loss in the network.
+
+
+
+
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+
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+
+
+9.1.1. Blockchain Operation
+
+ A "block" runs as a container of a batch of primary items (e.g.,
+ transactions, property records). The blocks are chained in such a
+ way that the hash of the previous block works as the pointer to the
+ header of the new block. Confirmation of each block requires a
+ consensus mechanism. When an item arrives at a blockchain node, the
+ latter broadcasts this item to the rest of the nodes, which receive
+ it, verify it, and put it in the ongoing block. The block
+ confirmation process begins as the number of items reaches the
+ predefined block capacity, at which time the node broadcasts its
+ proved block to the rest of the nodes, to be verified and chained.
+ The result is that block N+1 of each chain transitively vouches for
+ blocks N and previous of that chain.
+
+9.1.2. Blockchain Network Architecture
+
+ Blockchain node communication and coordination are achieved mainly
+ through frequent point-to-multipoint communication; however,
+ persistent point-to-point connections are used to transport both the
+ items and the blocks to the other nodes. For example, consider the
+ following implementation.
+
+ When a node is initiated, it first requests the other nodes'
+ addresses from a specific entity, such as DNS. The node then creates
+ persistent connections with each of the other nodes. If a node
+ confirms an item, it sends the item to the other nodes via these
+ persistent connections.
+
+ As a new block in a node is completed and is proven by the
+ surrounding nodes, it propagates towards its neighbor nodes. When
+ node A receives a block, it verifies it and then sends an invite
+ message to its neighbor B. Neighbor B checks to see if the
+ designated block is available and responds to A if it is unavailable;
+ A then sends the complete block to B. B repeats the process (as was
+ done by A) to start the next round of block propagation.
+
+ The challenge of blockchain network operation is not overall data
+ rates, since the volume from both the block and the item stays
+ between hundreds of bytes and a couple of megabytes per second;
+ rather, the challenge is in transporting the blocks with minimum
+ latency to maximize the efficiency of the blockchain consensus
+ process. The efficiency of differing implementations of the
+ consensus process may be affected to a differing degree by the
+ latency (and variation of latency) of the network.
+
+
+
+
+
+
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+
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+
+
+9.1.3. Blockchain Security Considerations
+
+ Security is crucial to blockchain applications; at the time of this
+ writing, blockchain systems address security issues mainly at the
+ application level, where cryptography as well as hash-based consensus
+ play a leading role in preventing both double-spending and malicious
+ service attacks. However, there is concern that in the proposed use
+ case for a private blockchain network that is dependent on
+ deterministic properties the network could be vulnerable to delays
+ and other specific attacks against determinism, as these delays and
+ attacks could interrupt service.
+
+9.2. Private Blockchain Today
+
+ Today, private blockchain runs in Layer 2 or Layer 3 VPNs, generally
+ without guaranteed determinism. The industry players are starting to
+ realize that improving determinism in their blockchain networks could
+ improve the performance of their service, but at present these goals
+ are not being met.
+
+9.3. Private Blockchain in the Future
+
+ Blockchain system performance can be greatly improved through
+ deterministic networking services, primarily because low latency
+ would accelerate the consensus process. It would be valuable to be
+ able to design a private blockchain network with the following
+ properties:
+
+ o Transport of point-to-multipoint traffic in a coordinated network
+ architecture rather than at the application layer (which typically
+ uses point-to-point connections)
+
+ o Guaranteed transport latency
+
+ o Reduced packet loss (to the point where delay incurred by packet
+ retransmissions would be negligible)
+
+9.4. Private Blockchain Requests to the IETF
+
+ o Layer 2 and Layer 3 multicast of blockchain traffic
+
+ o Item and block delivery with bounded, low latency and negligible
+ packet loss
+
+ o Coexistence of blockchain and IT traffic in a single network
+
+ o Ability to scale the network by distributing the centralized
+ control of the network across multiple control entities
+
+
+
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+
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+
+
+10. Network Slicing
+
+10.1. Use Case Description
+
+ Network slicing divides one physical network infrastructure into
+ multiple logical networks. Each slice, which corresponds to a
+ logical network, uses resources and network functions independently
+ from each other. Network slicing provides flexibility of resource
+ allocation and service quality customization.
+
+ Future services will demand network performance with a wide variety
+ of characteristics such as high data rate, low latency, low loss
+ rate, security, and many other parameters. Ideally, every service
+ would have its own physical network satisfying its particular
+ performance requirements; however, that would be prohibitively
+ expensive. Network slicing can provide a customized slice for a
+ single service, and multiple slices can share the same physical
+ network. This method can optimize performance for the service at
+ lower cost, and the flexibility of setting up and releasing the
+ slices also allows the user to allocate network resources
+ dynamically.
+
+ Unlike the other use cases presented here, network slicing is not a
+ specific application that depends on specific deterministic
+ properties; rather, it is introduced as an area of networking to
+ which DetNet might be applicable.
+
+10.2. DetNet Applied to Network Slicing
+
+10.2.1. Resource Isolation across Slices
+
+ One of the requirements discussed for network slicing is the "hard"
+ separation of various users' deterministic performance. That is, it
+ should be impossible for activity, lack of activity, or changes in
+ activity of one or more users to have any appreciable effect on the
+ deterministic performance parameters of any other slices. Typical
+ techniques used today, which share a physical network among users, do
+ not offer this level of isolation. DetNet can supply point-to-point
+ or point-to-multipoint paths that offer a user bandwidth and latency
+ guarantees that cannot be affected by other users' data traffic.
+ Thus, DetNet is a powerful tool when reliability and low latency are
+ required in network slicing.
+
+
+
+
+
+
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+10.2.2. Deterministic Services within Slices
+
+ Slices may need to provide services with DetNet-type performance
+ guarantees; note, however, that a system can be implemented to
+ provide such services in more than one way. For example, the slice
+ itself might be implemented using DetNet, and thus the slice can
+ provide service guarantees and isolation to its users without any
+ particular DetNet awareness on the part of the users' applications.
+ Alternatively, a "non-DetNet-aware" slice may host an application
+ that itself implements DetNet services and thus can enjoy similar
+ service guarantees.
+
+10.3. A Network Slicing Use Case Example - 5G Bearer Network
+
+ Network slicing is a core feature of 5G as defined in 3GPP. The
+ system architecture for 5G is under development at the time of this
+ writing [TS23501]. A network slice in a mobile network is a complete
+ logical network, including RANs and Core Networks (CNs). It provides
+ telecommunications services and network capabilities, which may vary
+ from slice to slice. A 5G bearer network is a typical use case for
+ network slicing; for example, consider three 5G service scenarios:
+ eMBB, URLLC, and mMTC.
+
+ o eMBB (Enhanced Mobile Broadband) focuses on services characterized
+ by high data rates, such as high-definition video, Virtual Reality
+ (VR), augmented reality, and fixed mobile convergence.
+
+ o URLLC (Ultra-Reliable and Low Latency Communications) focuses on
+ latency-sensitive services, such as self-driving vehicles, remote
+ surgery, or drone control.
+
+ o mMTC (massive Machine Type Communications) focuses on services
+ that have high connection-density requirements, such as those
+ typically used in smart-city and smart-agriculture scenarios.
+
+ A 5G bearer network could use DetNet to provide hard resource
+ isolation across slices and within a given slice. For example,
+ consider Slice-A and Slice-B, with DetNet used to transit services
+ URLLC-A and URLLC-B over them. Without DetNet, URLLC-A and URLLC-B
+ would compete for bandwidth resources, and latency and reliability
+ requirements would not be guaranteed. With DetNet, URLLC-A and
+ URLLC-B have separate bandwidth reservations; there is no resource
+ conflict between them, as though they were in different physical
+ networks.
+
+
+
+
+
+
+
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+
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+
+
+10.4. Non-5G Applications of Network Slicing
+
+ Although the operation of services not related to 5G is not part of
+ the 5G network slicing definition and scope, network slicing is
+ likely to become a preferred approach for providing various services
+ across a shared physical infrastructure. Examples include providing
+ services for electrical utilities and pro audio via slices. Use
+ cases like these could become more common once the work for the 5G CN
+ evolves to include wired as well as wireless access.
+
+10.5. Limitations of DetNet in Network Slicing
+
+ DetNet cannot cover every network slicing use case. One issue is
+ that DetNet is a point-to-point or point-to-multipoint technology;
+ however, network slicing ultimately needs multipoint-to-multipoint
+ guarantees. Another issue is that the number of flows that can be
+ carried by DetNet is limited by DetNet scalability; flow aggregation
+ and queuing management modification may help address this issue.
+ Additional work and discussion are needed to address these topics.
+
+10.6. Network Slicing Today and in the Future
+
+ Network slicing has promise in terms of satisfying many requirements
+ of future network deployment scenarios, but it is still a collection
+ of ideas and analyses without a specific technical solution. DetNet
+ is one of various technologies that could potentially be used in
+ network slicing, along with, for example, Flex-E and segment routing.
+ For more information, please see the IETF 99 Network Slicing BoF
+ session agenda and materials as provided in [IETF99-netslicing-BoF].
+
+10.7. Network Slicing Requests to the IETF
+
+ o Isolation from other flows through queuing management
+
+ o Service quality customization and guarantees
+
+ o Security
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+11. Use Case Common Themes
+
+ This section summarizes the expected properties of a DetNet network,
+ based on the use cases as described in this document.
+
+11.1. Unified, Standards-Based Networks
+
+11.1.1. Extensions to Ethernet
+
+ A DetNet network is not "a new kind of network" -- it is based on
+ extensions to existing Ethernet standards, including elements of
+ IEEE 802.1 TSN and related standards. Presumably, it will be
+ possible to run DetNet over other underlying transports besides
+ Ethernet, but Ethernet is explicitly supported.
+
+11.1.2. Centrally Administered Networks
+
+ In general, a DetNet network is not expected to be "plug and play";
+ rather, some type of centralized network configuration and control
+ system is expected. Such a system may be in a single central
+ location, or it may be distributed across multiple control entities
+ that function together as a unified control system for the network.
+ However, the ability to "hot swap" components (e.g., due to
+ malfunction) is similar enough to "plug and play" that this kind of
+ behavior may be expected in DetNet networks, depending on the
+ implementation.
+
+11.1.3. Standardized Data-Flow Information Models
+
+ Data-flow information models to be used with DetNet networks are to
+ be specified by DetNet.
+
+11.1.4. Layer 2 and Layer 3 Integration
+
+ A DetNet network is intended to integrate between Layer 2 (bridged)
+ network(s) (e.g., an AVB/TSN LAN) and Layer 3 (routed) network(s)
+ (e.g., using IP-based protocols). One example of this is making
+ AVB/TSN-type deterministic performance available from Layer 3
+ applications, e.g., using RTP. Another example is connecting two
+ AVB/TSN LANs ("islands") together through a standard router.
+
+11.1.5. IPv4 Considerations
+
+ This document explicitly does not specify any particular
+ implementation or protocol; however, it has been observed that
+ various use cases (and their associated industries) described herein
+ are explicitly based on IPv4 (as opposed to IPv6), and it is not
+ considered practical to expect such implementations to migrate to
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ IPv6 in order to use DetNet. Thus, the expectation is that even if
+ not every feature of DetNet is available in an IPv4 context, at least
+ some of the significant benefits (such as guaranteed end-to-end
+ delivery and low latency) will be available.
+
+11.1.6. Guaranteed End-to-End Delivery
+
+ Packets in a DetNet flow are guaranteed not to be dropped by the
+ network due to congestion. However, the network may drop packets for
+ intended reasons, e.g., per security measures. Similarly,
+ best-effort traffic on a DetNet is subject to being dropped (as on a
+ non-DetNet IP network). Also note that this guarantee applies to
+ actions taken by DetNet protocol software and does not provide any
+ guarantee against lower-level errors such as media errors or checksum
+ errors.
+
+11.1.7. Replacement for Multiple Proprietary Deterministic Networks
+
+ There are many proprietary non-interoperable deterministic Ethernet-
+ based networks available; DetNet is intended to provide an
+ open-standards-based alternative to such networks.
+
+11.1.8. Mix of Deterministic and Best-Effort Traffic
+
+ DetNet is intended to support the coexistence of time-sensitive
+ operational (OT) traffic and informational (IT) traffic on the same
+ ("unified") network.
+
+11.1.9. Unused Reserved Bandwidth to Be Available to Best-Effort
+ Traffic
+
+ If bandwidth reservations are made for a stream but the associated
+ bandwidth is not used at any point in time, that bandwidth is made
+ available on the network for best-effort traffic. If the owner of
+ the reserved stream then starts transmitting again, the bandwidth is
+ no longer available for best-effort traffic; this occurs on a
+ moment-to-moment basis. Note that such "temporarily available"
+ bandwidth is not available for time-sensitive traffic, which must
+ have its own reservation.
+
+11.1.10. Lower-Cost, Multi-Vendor Solutions
+
+ The DetNet network specifications are intended to enable an ecosystem
+ in which multiple vendors can create interoperable products, thus
+ promoting device diversity and potentially higher numbers of each
+ device manufactured, promoting cost reduction and cost competition
+
+
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ among vendors. In other words, vendors should be able to create
+ DetNet networks at lower cost and with greater diversity of available
+ devices than existing proprietary networks.
+
+11.2. Scalable Size
+
+ DetNet networks range in size from very small (e.g., inside a single
+ industrial machine) to very large (e.g., a utility-grid network
+ spanning a whole country and involving many "hops" over various kinds
+ of links -- for example, radio repeaters, microwave links, or fiber
+ optic links). However, recall that the scope of DetNet is confined
+ to networks that are centrally administered and thereby explicitly
+ excludes unbounded decentralized networks such as the Internet.
+
+11.2.1. Scalable Number of Flows
+
+ The number of flows in a given network application can potentially be
+ large and can potentially grow faster than the number of nodes and
+ hops, so the network should provide a sufficient (perhaps
+ configurable) maximum number of flows for any given application.
+
+11.3. Scalable Timing Parameters and Accuracy
+
+11.3.1. Bounded Latency
+
+ DetNet data-flow information models are expected to provide means to
+ configure the network that include parameters for querying network
+ path latency, requesting bounded latency for a given stream,
+ requesting worst-case maximum and/or minimum latency for a given path
+ or stream, and so on. It is expected that the network may not be
+ able to provide a given requested service level; if this is indeed
+ the case, the network control system should reply that the requested
+ services are not available (as opposed to accepting the parameter but
+ then not delivering the desired behavior).
+
+11.3.2. Low Latency
+
+ Various applications may state that they require "extremely low
+ latency"; however, depending on the application, "extremely low" may
+ imply very different latency bounds. For example, "low latency"
+ across a utility-grid network is a different order of magnitude of
+ latency values compared to "low latency" in a motor control loop in a
+ small machine. It is intended that the mechanisms for specifying
+ desired latency include wide ranges and that architecturally there is
+ nothing to prevent arbitrarily low latencies from being implemented
+ in a given network.
+
+
+
+
+
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+
+RFC 8578 DetNet Use Cases May 2019
+
+
+11.3.3. Bounded Jitter (Latency Variation)
+
+ As with the other latency-related elements noted above, parameters
+ that can determine or request permitted variations in latency should
+ be available.
+
+11.3.4. Symmetrical Path Delays
+
+ Some applications would like to specify that the transit delay time
+ values be equal for both the transmit path and the return path.
+
+11.4. High Reliability and Availability
+
+ Reliability is of critical importance to many DetNet applications,
+ because the consequences of failure can be extraordinarily high in
+ terms of cost and even human life. DetNet-based systems are expected
+ to be implemented with essentially arbitrarily high availability --
+ for example, 99.9999% uptime (where 99.9999 means "six nines") or
+ even 12 nines. DetNet designs should not make any assumptions about
+ the level of reliability and availability that may be required of a
+ given system and should define parameters for communicating these
+ kinds of metrics within the network.
+
+ A strategy used by DetNet for providing such extraordinarily high
+ levels of reliability is to provide redundant paths so that a system
+ can seamlessly switch between the paths while maintaining its
+ required level of performance.
+
+11.5. Security
+
+ Security is of critical importance to many DetNet applications. A
+ DetNet network must have the ability to be made secure against device
+ failures, attackers, misbehaving devices, and so on. In a DetNet
+ network, the data traffic is expected to be time sensitive; thus, in
+ addition to arriving with the data content as intended, the data must
+ also arrive at the expected time. This may present "new" security
+ challenges to implementers and must be addressed accordingly. There
+ are other security implications, including (but not limited to) the
+ change in attack surface presented by PRE.
+
+11.6. Deterministic Flows
+
+ Reserved-bandwidth data flows must be isolated from each other and
+ from best-effort traffic, so that even if the network is saturated
+ with best-effort (and/or reserved-bandwidth) traffic, the configured
+ flows are not adversely affected.
+
+
+
+
+
+Grossman Informational [Page 79]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+12. Security Considerations
+
+ This document covers a number of representative applications and
+ network scenarios that are expected to make use of DetNet
+ technologies. Each of the potential DetNet use cases will have
+ security considerations from both the use-specific perspective and
+ the DetNet technology perspective. While some use-specific security
+ considerations are discussed above, a more comprehensive discussion
+ of such considerations is captured in [DetNet-Security]
+ ("Deterministic Networking (DetNet) Security Considerations").
+ Readers are encouraged to review [DetNet-Security] to gain a more
+ complete understanding of DetNet-related security considerations.
+
+13. IANA Considerations
+
+ This document has no IANA actions.
+
+14. Informative References
+
+ [Ahm14] Ahmed, M. and R. Kim, "Communication Network Architectures
+ for Smart-Wind Power Farms", Energies 2014, pp. 3900-3921,
+ DOI 10.3390/en7063900, June 2014.
+
+ [Arch-for-6TiSCH]
+ Thubert, P., Ed., "An Architecture for IPv6 over the TSCH
+ mode of IEEE 802.15.4", Work in Progress,
+ draft-ietf-6tisch-architecture-20, March 2019.
+
+ [BACnet-IP]
+ ASHRAE, "Annex J to ANSI/ASHRAE 135-1995 - BACnet/IP",
+ January 1999, <http://www.bacnet.org/Addenda/
+ Add-1995-135a.pdf>.
+
+ [BAS-DetNet]
+ Kaneko, Y. and S. Das, "Building Automation Use Cases and
+ Requirements for Deterministic Networking", Work in
+ Progress, draft-bas-usecase-detnet-00, October 2015.
+
+ [CoAP-6TiSCH]
+ Sudhaakar, R., Ed. and P. Zand, "6TiSCH Resource
+ Management and Interaction using CoAP", Work in Progress,
+ draft-ietf-6tisch-coap-03, March 2015.
+
+ [CoMP] NGMN Alliance, "RAN EVOLUTION PROJECT COMP EVALUATION AND
+ ENHANCEMENT", VERSION 2.0, NGMN Alliance, March 2015,
+ <https://www.ngmn.org/fileadmin/user_upload/
+ NGMN_RANEV_D3_CoMP_Evaluation_and_Enhancement_v2.0.pdf>.
+
+
+
+
+Grossman Informational [Page 80]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ [Content_Protection]
+ Olsen, D., "1722a Content Protection", April 2012,
+ <http://grouper.ieee.org/groups/1722/contributions/2012/
+ avtp_dolsen_1722a_content_protection.pdf>.
+
+ [CPRI] CPRI Cooperation, "Common Public Radio Interface (CPRI);
+ Interface Specification", CPRI Specification V6.1,
+ July 2014, <http://www.cpri.info/downloads/
+ CPRI_v_6_1_2014-07-01.pdf>.
+
+ [DCI] Digital Cinema Initiatives, LLC, "DCI Specification,
+ Version 1.3", June 2018, <https://www.dcimovies.com/>.
+
+ [Det-Fwd-PHB]
+ Shah, S. and P. Thubert, "Deterministic Forwarding PHB",
+ Work in Progress,
+ draft-svshah-tsvwg-deterministic-forwarding-04,
+ August 2015.
+
+ [DetNet-6TiSCH]
+ Thubert, P., Ed., "6TiSCH requirements for DetNet", Work
+ in Progress, draft-thubert-6tisch-4detnet-01, June 2015.
+
+ [DetNet-Arch]
+ Finn, N., Thubert, P., Varga, B., and J. Farkas,
+ "Deterministic Networking Architecture", Work in Progress,
+ draft-ietf-detnet-architecture-13, May 2019.
+
+ [DetNet-Audio-Reqs]
+ Gunther, C., Ed. and E. Grossman, Ed., "Deterministic
+ Networking Professional Audio Requirements", Work in
+ Progress, draft-gunther-detnet-proaudio-req-01,
+ March 2015.
+
+ [DetNet-Mobile]
+ Zha, Y., "Deterministic Networking Use Case in Mobile
+ Network", Work in Progress, draft-zha-detnet-use-case-00,
+ July 2015.
+
+ [DetNet-RAN]
+ Korhonen, J., "Deterministic networking for radio
+ access networks", Work in Progress,
+ draft-korhonen-detnet-telreq-00, May 2015.
+
+
+
+
+
+
+
+
+Grossman Informational [Page 81]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ [DetNet-Security]
+ Mizrahi, T., Grossman, E., Ed., Hacker, A., Das, S.,
+ Dowdell, J., Austad, H., Stanton, K., and N. Finn,
+ "Deterministic Networking (DetNet) Security
+ Considerations", Work in Progress,
+ draft-ietf-detnet-security-04, March 2019.
+
+ [DetNet-Util-Reqs]
+ Wetterwald, P. and J. Raymond, "Deterministic Networking
+ Uitilities requirements", Work in Progress,
+ draft-wetterwald-detnet-utilities-reqs-02, June 2015.
+
+ [eCPRI] IEEE Standards Association, "Common Public Radio
+ Interface: eCPRI Interface Specification V1.2", June 2018,
+ <http://www.cpri.info/>.
+
+ [ESPN_DC2] Daley, D., "ESPN's DC2 Scales AVB Large", SVG News,
+ June 2014, <https://sportsvideo.org/main/blog/2014/06/
+ espns-dc2-scales-avb-large>.
+
+ [EtherCAT] "EtherCAT Technology Group",
+ <https://www.ethercat.org/default.htm>.
+
+ [FL-net] Japan Electrical Manufacturers Association, "JEMA 1479 -
+ English Edition", September 2012,
+ <https://www.jema-net.or.jp/Japanese/standard/opcn/pdf/
+ JEM_1479e(20120927).pdf>.
+
+ [Fronthaul]
+ Chen, D. and T. Mustala, "Ethernet Fronthaul
+ Considerations", IEEE 1904.3, February 2015,
+ <http://www.ieee1904.org/3/meeting_archive/2015/02/
+ tf3_1502_chen_1.pdf>.
+
+ [IEC-60834]
+ International Electrotechnical Commission, "Teleprotection
+ equipment of power systems - Performance and testing",
+ IEC 60834, October 1999.
+
+ [IEC-60870-5-104]
+ International Electrotechnical Commission, "Telecontrol
+ equipment and systems - Part 5-104: Transmission protocols
+ - Network access for IEC 60870-5-101 using standard
+ transport profiles", IEC 60870-5-104, June 2006.
+
+
+
+
+
+
+
+Grossman Informational [Page 82]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ [IEC-61400-25]
+ International Electrotechnical Commission, "Communications
+ for monitoring and control of wind power plants",
+ IEC 61400-25, June 2013.
+
+ [IEC-61850-5:2013]
+ International Electrotechnical Commission, "Communication
+ networks and systems for power utility automation -
+ Part 5: Communication requirements for functions and
+ device models", IEC 61850-5, January 2013.
+
+ [IEC-61850-9-2:2011]
+ International Electrotechnical Commission, "Communication
+ networks and systems for power utility automation -
+ Part 9-2: Specific communication service mapping (SCSM) -
+ Sampled values over ISO/IEC 8802-3", IEC 61850-9-2,
+ September 2011.
+
+ [IEC-61850-90-12:2015]
+ International Electrotechnical Commission, "Communication
+ networks and systems for power utility automation -
+ Part 90-12: Wide area network engineering guidelines",
+ IEC TR 61850-90-12, July 2015.
+
+ [IEC-62357-200:2015]
+ International Electrotechnical Commission, "Power systems
+ management and associated information exchange - Part 200:
+ Guidelines for migration from Internet Protocol version 4
+ (IPv4) to Internet Protocol version 6 (IPv6)",
+ IEC 62357-200:2015, July 2015.
+
+ [IEC-62439-3:2016]
+ International Electrotechnical Commission, "Industrial
+ communication networks - High availability automation
+ networks - Part 3: Parallel Redundancy Protocol (PRP) and
+ High-availability Seamless Redundancy (HSR)", March 2016.
+
+ [IEC-IEEE-61850-9-3:2016]
+ International Electrotechnical Commission, "Communication
+ networks and systems for power utility automation -
+ Part 9-3: Precision time protocol profile for power
+ utility automation", IEC 61850-9-3, May 2016.
+
+ [IEEE-1588]
+ IEEE, "IEEE Standard for a Precision Clock Synchronization
+ Protocol for Networked Measurement and Control Systems",
+ IEEE Standard 1588, <https://standards.ieee.org/findstds/
+ standard/1588-2008.html>.
+
+
+
+Grossman Informational [Page 83]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ [IEEE-1646]
+ IEEE, "IEEE Standard Communication Delivery Time
+ Performance Requirements for Electric Power Substation
+ Automation", IEEE Standard 1646,
+ <https://standards.ieee.org/standard/1646-2004.html>.
+
+ [IEEE-1722]
+ IEEE, "IEEE Standard for a Transport Protocol for
+ Time-Sensitive Applications in Bridged Local Area
+ Networks", IEEE Standard 1722,
+ <https://standards.ieee.org/findstds/
+ standard/1722-2016.html>.
+
+ [IEEE-1815]
+ IEEE Standards Association, "IEEE Standard for Electric
+ Power Systems Communications-Distributed Network Protocol
+ (DNP3)", IEEE Standard 1815, <https://ieeexplore.ieee.org/
+ servlet/opac?punumber=6327576>.
+
+ [IEEE-19143]
+ IEEE Standards Association, "IEEE Standard for Radio over
+ Ethernet Encapsulations and Mappings", IEEE 1914.3,
+ <https://standards.ieee.org/develop/project/1914.3.html>.
+
+ [IEEE-80211]
+ IEEE Standard for Information technology, "IEEE Std.
+ 802.11, Telecommunications and information exchange
+ between systems--Local and metropolitan area networks--
+ Specific requirements - Part 11: Wireless LAN Medium
+ Access Control (MAC) and Physical Layer (PHY)
+ Specifications",
+ <https://standards.ieee.org/standard/802_11-2016.html>.
+
+ [IEEE-802154]
+ IEEE Standard for Information technology, "IEEE Std.
+ 802.15.4, Part 15.4: Wireless Medium Access Control (MAC)
+ and Physical Layer (PHY) Specifications for Low Rate
+ Wireless Personal Area Networks (WPANs)",
+ <https://standards.ieee.org/standard/802_15_4-2015.html>.
+
+ [IEEE-8021AS]
+ IEEE, "IEEE Standard for Local and Metropolitan Area
+ Networks - Timing and Synchronization for Time-Sensitive
+ Applications in Bridged Local Area Networks",
+ IEEE 802.1AS,
+ <http://www.ieee802.org/1/pages/802.1as.html>.
+
+
+
+
+
+Grossman Informational [Page 84]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ [IEEE-8021CM]
+ "IEEE Standard for Local and metropolitan area networks -
+ Time-Sensitive Networking for Fronthaul", IEEE
+ Standard 802.1CM,
+ <https://standards.ieee.org/standard/802_1CM-2018.html>.
+
+ [IEEE-8021TSNTG]
+ IEEE Standards Association, "IEEE 802.1 Time-Sensitive
+ Networking Task Group",
+ <http://www.ieee802.org/1/pages/avbridges.html>.
+
+ [IETF99-netslicing-BoF]
+ "Network Slicing (netslicing) BoF", IETF 99, Prague,
+ July 2017, <https://datatracker.ietf.org/meeting/99/
+ materials/slides-99-netslicing-chairs-netslicing-bof-04>.
+
+ [Interface-6TiSCH-6top]
+ Wang, Q., Ed. and X. Vilajosana, "6TiSCH Operation
+ Sublayer (6top) Interface", Work in Progress,
+ draft-ietf-6tisch-6top-interface-04, July 2015.
+
+ [ISA100] ISA/ANSI, "ISA100, Wireless Systems for Automation",
+ <https://www.isa.org/isa100/>.
+
+ [KNX] KNX Association, "ISO/IEC 14543-3 - KNX", November 2006.
+
+ [LonTalk] Echelon Corp., "LonTalk(R) Protocol Specification
+ Version 3.0", 1994, <http://www.enerlon.com/JobAids/
+ Lontalk%20Protocol%20Spec.pdf>.
+
+ [MailingList-6TiSCH]
+ IETF, "6TiSCH Mailing List",
+ <https://mailarchive.ietf.org/arch/browse/6tisch/>.
+
+ [MEF22.1.1]
+ Metro Ethernet Forum, "Mobile Backhaul Phase 2 Amendment 1
+ -- Small Cells", MEF 22.1.1, July 2014,
+ <http://www.mef.net/Assets/Technical_Specifications/PDF/
+ MEF_22.1.1.pdf>.
+
+ [MEF8] Metro Ethernet Forum, "Implementation Agreement for the
+ Emulation of PDH Circuits over Metro Ethernet Networks",
+ MEF 8, October 2004, <https://www.mef.net/
+ Assets/Technical_Specifications/PDF/MEF_8.pdf>.
+
+
+
+
+
+
+
+Grossman Informational [Page 85]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ [METIS] METIS, "Scenarios, requirements and KPIs for 5G mobile and
+ wireless system", Document Number ICT-317669-METIS/D1.1,
+ April 2013, <https://metis2020.com/wp-content/
+ uploads/deliverables/METIS_D1.1_v1.pdf>.
+
+ [MODBUS] Modbus Organization, Inc., "MODBUS Application Protocol
+ Specification", April 2012,
+ <http://www.modbus.org/specs.php>.
+
+ [NGMN] NGMN Alliance, "5G White Paper", NGMN 5G White Paper v1.0,
+ February 2015, <https://www.ngmn.org/fileadmin/ngmn/
+ content/downloads/Technical/2015/
+ NGMN_5G_White_Paper_V1_0.pdf>.
+
+ [NGMN-Fronth]
+ NGMN Alliance, "Fronthaul Requirements for C-RAN",
+ March 2015, <https://www.ngmn.org/fileadmin/user_upload/
+ NGMN_RANEV_D1_C-RAN_Fronthaul_Requirements_v1.0.pdf>.
+
+ [OPCXML] OPC Foundation, "OPC Data Access (OPC DA) Specification",
+ <http://www.opcti.com/opc-da-specification.aspx>.
+
+ [PCE] IETF, "Path Computation Element",
+ <https://datatracker.ietf.org/doc/charter-ietf-pce/>.
+
+ [PROFIBUS] IEC, "PROFIBUS Standard - DP Specification (IEC 61158
+ Type 3)", <https://www.profibus.com/>.
+
+ [PROFINET] "PROFINET Technology",
+ <https://us.profinet.com/technology/profinet/>.
+
+ [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
+ Label Switching Architecture", RFC 3031,
+ DOI 10.17487/RFC3031, January 2001,
+ <https://www.rfc-editor.org/info/rfc3031>.
+
+ [RFC3411] Harrington, D., Presuhn, R., and B. Wijnen, "An
+ Architecture for Describing Simple Network Management
+ Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
+ DOI 10.17487/RFC3411, December 2002,
+ <https://www.rfc-editor.org/info/rfc3411>.
+
+ [RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
+ Edge-to-Edge (PWE3) Architecture", RFC 3985,
+ DOI 10.17487/RFC3985, March 2005,
+ <https://www.rfc-editor.org/info/rfc3985>.
+
+
+
+
+
+Grossman Informational [Page 86]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ [RFC4553] Vainshtein, A., Ed. and YJ. Stein, Ed., "Structure-
+ Agnostic Time Division Multiplexing (TDM) over Packet
+ (SAToP)", RFC 4553, DOI 10.17487/RFC4553, June 2006,
+ <https://www.rfc-editor.org/info/rfc4553>.
+
+ [RFC5086] Vainshtein, A., Ed., Sasson, I., Metz, E., Frost, T., and
+ P. Pate, "Structure-Aware Time Division Multiplexed (TDM)
+ Circuit Emulation Service over Packet Switched Network
+ (CESoPSN)", RFC 5086, DOI 10.17487/RFC5086, December 2007,
+ <https://www.rfc-editor.org/info/rfc5086>.
+
+ [RFC5087] Stein, Y(J)., Shashoua, R., Insler, R., and M. Anavi,
+ "Time Division Multiplexing over IP (TDMoIP)", RFC 5087,
+ DOI 10.17487/RFC5087, December 2007,
+ <https://www.rfc-editor.org/info/rfc5087>.
+
+ [RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
+ "Network Time Protocol Version 4: Protocol and Algorithms
+ Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
+ <https://www.rfc-editor.org/info/rfc5905>.
+
+ [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
+ Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
+ JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
+ Low-Power and Lossy Networks", RFC 6550,
+ DOI 10.17487/RFC6550, March 2012,
+ <https://www.rfc-editor.org/info/rfc6550>.
+
+ [RFC6551] Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N.,
+ and D. Barthel, "Routing Metrics Used for Path Calculation
+ in Low-Power and Lossy Networks", RFC 6551,
+ DOI 10.17487/RFC6551, March 2012,
+ <https://www.rfc-editor.org/info/rfc6551>.
+
+ [RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using
+ IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the
+ Internet of Things (IoT): Problem Statement", RFC 7554,
+ DOI 10.17487/RFC7554, May 2015,
+ <https://www.rfc-editor.org/info/rfc7554>.
+
+ [RFC8169] Mirsky, G., Ruffini, S., Gray, E., Drake, J., Bryant, S.,
+ and A. Vainshtein, "Residence Time Measurement in MPLS
+ Networks", RFC 8169, DOI 10.17487/RFC8169, May 2017,
+ <https://www.rfc-editor.org/info/rfc8169>.
+
+
+
+
+
+
+
+Grossman Informational [Page 87]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ [Spe09] Barbosa, R., Sadre, R., and A. Pras, "A First Look into
+ SCADA Network Traffic", IP Network Operations and
+ Management Symposium, DOI 10.1109/NOMS.2012.6211945,
+ June 2012, <https://ieeexplore.ieee.org/document/6211945>.
+
+ [SR-IP-RAN-Use-Case]
+ Khasnabish, B., Hu, F., and L. Contreras, "Segment
+ Routing in IP RAN use case", Work in Progress,
+ draft-kh-spring-ip-ran-use-case-02, November 2014.
+
+ [SRP_LATENCY]
+ Gunther, C., "Specifying SRP Acceptable Latency",
+ March 2014, <http://www.ieee802.org/1/files/public/
+ docs2014/cc-cgunther-acceptable-latency-0314-v01.pdf>.
+
+ [Sublayer-6TiSCH-6top]
+ Wang, Q., Ed. and X. Vilajosana, "6TiSCH Operation
+ Sublayer (6top)", Work in Progress,
+ draft-wang-6tisch-6top-sublayer-04, November 2015.
+
+ [syncE] International Telecommunication Union, "Timing and
+ synchronization aspects in packet networks", ITU-T
+ Recommendation G.8261, August 2013,
+ <https://www.itu.int/rec/T-REC-G.8261>.
+
+ [Timing-over-MPLS]
+ Davari, S., Oren, A., Bhatia, M., Roberts, P., and L.
+ Montini, "Transporting Timing messages over MPLS
+ Networks", Work in Progress,
+ draft-ietf-tictoc-1588overmpls-07, October 2015.
+
+ [TR38801] 3GPP, "Study on new radio access technology: Radio access
+ architecture and interfaces (Release 14)", 3GPP TR 38.801,
+ April 2017,
+ <https://portal.3gpp.org/desktopmodules/Specifications/
+ SpecificationDetails.aspx?specificationId=3056>.
+
+ [TS23401] 3GPP, "General Packet Radio Service (GPRS) enhancements
+ for Evolved Universal Terrestrial Radio Access Network
+ (E-UTRAN) access (Release 16)", 3GPP TS 23.401,
+ March 2019, <https://portal.3gpp.org/
+ desktopmodules/ Specifications/
+ SpecificationDetails.aspx?specificationId=849>.
+
+ [TS23501] 3GPP, "System architecture for the 5G System (5GS)
+ (Release 15)", 3GPP TS 23.501, March 2019,
+ <https://portal.3gpp.org/desktopmodules/Specifications/
+ SpecificationDetails.aspx?specificationId=3144>.
+
+
+
+Grossman Informational [Page 88]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ [TS25104] 3GPP, "Base Station (BS) radio transmission and reception
+ (FDD) (Release 16)", 3GPP TS 25.104, January 2019,
+ <https://portal.3gpp.org/desktopmodules/Specifications/
+ SpecificationDetails.aspx?specificationId=1154>.
+
+ [TS36104] 3GPP, "Evolved Universal Terrestrial Radio Access
+ (E-UTRA); Base Station (BS) radio transmission and
+ reception (Release 16)", 3GPP TS 36.104, January 2019,
+ <https://portal.3gpp.org/desktopmodules/Specifications/
+ SpecificationDetails.aspx?specificationId=2412>.
+
+ [TS36133] 3GPP, "Evolved Universal Terrestrial Radio Access
+ (E-UTRA); Requirements for support of radio resource
+ management (Release 16)", 3GPP TS 36.133, January 2019,
+ <https://portal.3gpp.org/desktopmodules/Specifications/
+ SpecificationDetails.aspx?specificationId=2420>.
+
+ [TS36211] 3GPP, "Evolved Universal Terrestrial Radio Access
+ (E-UTRA); Physical channels and modulation (Release 15)",
+ 3GPP TS 36.211, January 2019,
+ <https://portal.3gpp.org/desktopmodules/Specifications/
+ SpecificationDetails.aspx?specificationId=2425>.
+
+ [TS36300] 3GPP, "Evolved Universal Terrestrial Radio Access (E-UTRA)
+ and Evolved Universal Terrestrial Radio Access Network
+ (E-UTRAN); Overall description; Stage 2 (Release 15)",
+ 3GPP TS 36.300, January 2019,
+ <https://portal.3gpp.org/desktopmodules/Specifications/
+ SpecificationDetails.aspx?specificationId=2430>.
+
+ [WirelessHART]
+ International Electrotechnical Commission, "Industrial
+ networks - Wireless communication network and
+ communication profiles - WirelessHART(TM)",
+ IEC 62591:2016, March 2016.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Grossman Informational [Page 89]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+Appendix A. Use Cases Explicitly Out of Scope for DetNet
+
+ This appendix contains text regarding use cases that have been
+ determined to be outside the scope of the present DetNet work.
+
+A.1. DetNet Scope Limitations
+
+ The scope of DetNet is deliberately limited to specific use cases
+ that are consistent with the WG charter, subject to the
+ interpretation of the WG. At the time that the DetNet use cases were
+ solicited and provided by the authors, the scope of DetNet was not
+ clearly defined. As the scope has been clarified, certain use cases
+ have been determined to be outside the scope of the present DetNet
+ work. Text regarding these use cases was moved to this appendix to
+ clarify that they will not be supported by the DetNet work.
+
+ The text was moved to this appendix based on the following
+ "exclusion" principles. Please note that as an alternative to moving
+ all such text to this appendix some text has been modified in situ to
+ reflect these same principles.
+
+ The following principles have been established to clarify the scope
+ of the present DetNet work.
+
+ o The scope of networks addressed by DetNet is limited to networks
+ that can be centrally controlled, i.e., an "enterprise" (aka
+ "corporate") network. This explicitly excludes "the open
+ Internet".
+
+ o Maintaining time synchronization across a DetNet network is
+ crucial to its operation; however, DetNet assumes that time is to
+ be maintained using other means. One example would be PTP
+ [IEEE-1588]. A use case may state the accuracy and reliability
+ that it expects from the DetNet network as part of a whole system;
+ however, it is understood that such timing properties are not
+ guaranteed by DetNet itself. At the time of this writing, two
+ open questions remain: (1) whether DetNet protocols will include a
+ way for an application to communicate expectations regarding such
+ timing properties to the network and (2) if so, whether those
+ properties would likely have a material effect on network
+ performance as a result.
+
+A.2. Internet-Based Applications
+
+ There are many applications that communicate over the open Internet
+ that could benefit from guaranteed delivery and bounded latency.
+ However, as noted above, all such applications, when run over the
+ open Internet, are out of scope for DetNet. These same applications
+
+
+
+Grossman Informational [Page 90]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ may be in scope when run in constrained environments, i.e., within a
+ centrally controlled DetNet network. The following are some examples
+ of such applications.
+
+A.2.1. Use Case Description
+
+A.2.1.1. Media Content Delivery
+
+ Media content delivery continues to be an important use of the
+ Internet, yet users often experience poor-quality audio and video due
+ to the delay and jitter inherent in today's Internet.
+
+A.2.1.2. Online Gaming
+
+ Online gaming is a significant part of the gaming market; however,
+ latency can degrade the end user's experience. For example, "First
+ Person Shooter" (FPS) games are highly delay sensitive.
+
+A.2.1.3. Virtual Reality
+
+ VR has many commercial applications, including real estate
+ presentations, remote medical procedures, and so on. Low latency is
+ critical to interacting with the virtual world, because perceptual
+ delays can cause motion sickness.
+
+A.2.2. Internet-Based Applications Today
+
+ Internet service today is by definition "best effort", with no
+ guarantees regarding delivery or bandwidth.
+
+A.2.3. Internet-Based Applications in the Future
+
+ One should be able to play Internet videos without glitches and play
+ Internet games without lag.
+
+ For online gaming, the desired maximum allowance for round-trip delay
+ is typically 100 ms. However, it may be less for specific types of
+ games; for example, for FPS games, the maximum delay should be 50 ms.
+ Transport delay is the dominant part, with a budget of 5-20 ms.
+
+ For VR, a maximum delay of 1-10 ms is needed; if doing remote VR, the
+ total network delay budget is 1-5 ms.
+
+ Flow identification can be used for gaming and VR, i.e., it can
+ recognize a critical flow and provide appropriate latency bounds.
+
+
+
+
+
+
+Grossman Informational [Page 91]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+A.2.4. Internet-Based Applications Requests to the IETF
+
+ o Unified control and management protocols that handle time-critical
+ data flows
+
+ o An application-aware flow-filtering mechanism that recognizes
+ time-critical flows without doing 5-tuple matching
+
+ o A unified control plane that provides low-latency service on
+ Layer 3 without changing the data plane
+
+ o An OAM system and protocols that can help provide service
+ provisioning that is sensitive to end-to-end delays
+
+A.3. Pro Audio and Video - Digital Rights Management (DRM)
+
+ The following text was moved to this appendix because this
+ information is considered a link-layer topic for which DetNet is not
+ directly responsible.
+
+ Digital Rights Management (DRM) is very important to the audio and
+ video industries. Whenever protected content is introduced into a
+ network, there are DRM concerns that must be taken into account (see
+ [Content_Protection]). Many aspects of DRM are outside the scope of
+ network technology; however, there are cases when a secure link
+ supporting authentication and encryption is required by content
+ owners to carry their audio or video content when it is outside their
+ own secure environment (for example, see [DCI]).
+
+ As an example, two such techniques are Digital Transmission Content
+ Protection (DTCP) and High-bandwidth Digital Content Protection
+ (HDCP). HDCP content is not approved for retransmission within any
+ other type of DRM, while DTCP content may be retransmitted under
+ HDCP. Therefore, if the source of a stream is outside of the network
+ and it uses HDCP, it is only allowed to be placed on the network with
+ that same type of protection (i.e., HDCP).
+
+A.4. Pro Audio and Video - Link Aggregation
+
+ Note: The term "link aggregation" is used here as defined by the text
+ in the following paragraph, i.e., not following a more common
+ network-industry definition.
+
+ For transmitting streams that require more bandwidth than a single
+ link in the target network can support, link aggregation is a
+ technique for combining (aggregating) the bandwidth available on
+ multiple physical links to create a single logical link that provides
+
+
+
+
+Grossman Informational [Page 92]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ the required bandwidth. However, if aggregation is to be used, the
+ network controller (or equivalent) must be able to determine the
+ maximum latency of any path through the aggregate link.
+
+A.5. Pro Audio and Video - Deterministic Time to Establish Streaming
+
+ The DetNet WG decided that guidelines for establishing a
+ deterministic time to establish stream startup are not within the
+ scope of DetNet. If the bounded timing for establishing or
+ re-establishing streams is required in a given use case, it is up to
+ the application/system to achieve it.
+
+Acknowledgments
+
+ Pro audio (Section 2)
+
+ As also acknowledged in [DetNet-Audio-Reqs], the editor would like
+ to acknowledge the help of the following individuals and the
+ companies they represent.
+
+ Jeff Koftinoff, Meyer Sound
+ Jouni Korhonen, Associate Technical Director, Broadcom
+ Pascal Thubert, CTAO, Cisco
+ Kieran Tyrrell, Sienda New Media Technologies GmbH
+
+ Utility telecom (Section 3)
+
+ Information regarding utility telecom was derived from
+ [DetNet-Util-Reqs]. As in that document, the following
+ individuals are acknowledged here.
+
+ Faramarz Maghsoodlou, Ph.D., IoT Connected Industries
+ and Energy Practice, Cisco
+ Pascal Thubert, CTAO, Cisco
+
+ The wind power generation use case has been extracted from the
+ study of wind parks conducted within the 5GPPP VirtuWind Project.
+ The project is funded by the European Union's Horizon 2020
+ research and innovation programme under grant agreement No. 671648
+ (VirtuWind).
+
+ Building automation systems (Section 4)
+
+ Please see [BAS-DetNet].
+
+
+
+
+
+
+
+Grossman Informational [Page 93]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ Wireless for industrial applications (Section 5)
+
+ See [DetNet-6TiSCH].
+
+ [DetNet-6TiSCH] derives from the 6TiSCH architecture, which is the
+ result of multiple interactions -- in particular, during the
+ 6TiSCH (bi)weekly interim call, relayed through the 6TiSCH mailing
+ list at the IETF [MailingList-6TiSCH].
+
+ As also acknowledged in [DetNet-6TiSCH], the editor wishes to
+ thank Kris Pister, Thomas Watteyne, Xavier Vilajosana, Qin Wang,
+ Tom Phinney, Robert Assimiti, Michael Richardson, Zhuo Chen,
+ Malisa Vucinic, Alfredo Grieco, Martin Turon, Dominique Barthel,
+ Elvis Vogli, Guillaume Gaillard, Herman Storey, Maria Rita
+ Palattella, Nicola Accettura, Patrick Wetterwald, Pouria Zand,
+ Raghuram Sudhaakar, and Shitanshu Shah for their participation and
+ various contributions.
+
+ Cellular radio (Section 6)
+
+ See [DetNet-RAN].
+
+ Internet applications and CoMP (Section 6)
+
+ As also acknowledged in [DetNet-Mobile], authored by Yiyong Zha,
+ the editor would like to thank the following people for their
+ reviews, suggestions, comments, and proposed text: Jing Huang,
+ Junru Lin, Lehong Niu, and Oliver Huang.
+
+ Industrial Machine to Machine (M2M) (Section 7)
+
+ The editor would like to thank Feng Chen and Marcel Kiessling for
+ their comments and suggestions.
+
+ Mining industry (Section 8)
+
+ This text was written by Diego Dujovne, who worked in conjunction
+ with Xavier Vilajosana.
+
+ Private blockchain (Section 9)
+
+ This text was written by Daniel Huang.
+
+ Network slicing (Section 10)
+
+ This text was written by Xuesong Geng, who would like to
+ acknowledge Norm Finn and Mach Chen for their useful comments.
+
+
+
+
+Grossman Informational [Page 94]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+Contributors
+
+ RFC 7322 ("RFC Style Guide") generally limits the number of authors
+ listed on the front page of a document to five individuals -- far
+ fewer than the 19 individuals listed below, who also made important
+ contributions to this document. The editor wishes to thank and
+ acknowledge each of the following authors for contributing text to
+ this document. See also the Acknowledgments section.
+
+ Craig Gunther (Harman International)
+ 10653 South River Front Parkway
+ South Jordan, UT 84095
+ United States of America
+ Phone: +1 801 568 7675
+ Email: craig.gunther@harman.com
+
+ Pascal Thubert (Cisco Systems, Inc.)
+ Building D, 45 Allee des Ormes - BP1200
+ Mougins - Sophia Antipolis 06254
+ France
+ Phone: +33 4 97 23 26 34
+ Email: pthubert@cisco.com
+
+ Patrick Wetterwald (Cisco Systems)
+ 45 Allee des Ormes
+ Mougins 06250
+ France
+ Phone: +33 4 97 23 26 36
+ Email: pwetterw@cisco.com
+
+ Jean Raymond (Hydro-Quebec)
+ 1500 University
+ Montreal, Quebec H3A 3S7
+ Canada
+ Phone: +1 514 840 3000
+ Email: raymond.jean@hydro.qc.ca
+
+ Jouni Korhonen (Broadcom Corporation)
+ 3151 Zanker Road
+ San Jose, CA 95134
+ United States of America
+ Email: jouni.nospam@gmail.com
+
+ Yu Kaneko (Toshiba)
+ 1 Komukai-Toshiba-cho
+ Saiwai-ku, Kasasaki-shi, Kanagawa
+ Japan
+ Email: yu1.kaneko@toshiba.co.jp
+
+
+
+Grossman Informational [Page 95]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ Subir Das (Vencore Labs)
+ 150 Mount Airy Road
+ Basking Ridge, NJ 07920
+ United States of America
+ Email: sdas@appcomsci.com
+
+ Balazs Varga (Ericsson)
+ Konyves Kalman krt. 11/B
+ Budapest 1097
+ Hungary
+ Email: balazs.a.varga@ericsson.com
+
+ Janos Farkas (Ericsson)
+ Konyves Kalman krt. 11/B
+ Budapest 1097
+ Hungary
+ Email: janos.farkas@ericsson.com
+
+ Franz-Josef Goetz (Siemens)
+ Gleiwitzerstr. 555
+ Nurnberg 90475
+ Germany
+ Email: franz-josef.goetz@siemens.com
+
+ Juergen Schmitt (Siemens)
+ Gleiwitzerstr. 555
+ Nurnberg 90475
+ Germany
+ Email: juergen.jues.schmitt@siemens.com
+
+ Xavier Vilajosana (Worldsensing)
+ 483 Arago
+ Barcelona, Catalonia 08013
+ Spain
+ Email: xvilajosana@worldsensing.com
+
+ Toktam Mahmoodi (King's College London)
+ Strand, London WC2R 2LS
+ United Kingdom
+ Email: toktam.mahmoodi@kcl.ac.uk
+
+ Spiros Spirou (Intracom Telecom)
+ 19.7 km Markopoulou Ave.
+ Peania, Attiki 19002
+ Greece
+ Email: spiros.spirou@gmail.com
+
+
+
+
+
+Grossman Informational [Page 96]
+
+RFC 8578 DetNet Use Cases May 2019
+
+
+ Petra Vizarreta (Technical University of Munich)
+ Maxvorstadt, Arcisstrasse 21
+ Munich 80333
+ Germany
+ Email: petra.stojsavljevic@tum.de
+
+ Daniel Huang (ZTE Corporation, Inc.)
+ No. 50 Software Avenue
+ Nanjing, Jiangsu 210012
+ China
+ Email: huang.guangping@zte.com.cn
+
+ Xuesong Geng (Huawei Technologies)
+ Email: gengxuesong@huawei.com
+
+ Diego Dujovne (Universidad Diego Portales)
+ Email: diego.dujovne@mail.udp.cl
+
+ Maik Seewald (Cisco Systems)
+ Email: maseewal@cisco.com
+
+Author's Address
+
+ Ethan Grossman (editor)
+ Dolby Laboratories, Inc.
+ 1275 Market Street
+ San Francisco, CA 94103
+ United States of America
+
+ Phone: +1 415 645 4726
+ Email: ethan.grossman@dolby.com
+ URI: http://www.dolby.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Grossman Informational [Page 97]
+