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rfc:rfc8578

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.

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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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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 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.

Grossman Informational [Page 8] RFC 8578 DetNet Use Cases May 2019

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

Grossman Informational [Page 11] RFC 8578 DetNet Use Cases May 2019

 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...))

Grossman Informational [Page 13] 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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 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.

Grossman Informational [Page 15] 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.

Grossman Informational [Page 16] 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

Grossman Informational [Page 17] 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

Grossman Informational [Page 18] 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

Grossman Informational [Page 19] 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

Grossman Informational [Page 20] 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

Grossman Informational [Page 22] 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:

Grossman Informational [Page 23] 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

Grossman Informational [Page 24] RFC 8578 DetNet Use Cases May 2019

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)

Grossman Informational [Page 25] 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

Grossman Informational [Page 26] 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)

Grossman Informational [Page 27] RFC 8578 DetNet Use Cases May 2019

 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.

Grossman Informational [Page 43] 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.

Grossman Informational [Page 44] 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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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

Grossman Informational [Page 46] 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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 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.

Grossman Informational [Page 48] 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

  1. –+——– ………… ————

| 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.
  1. –+——– ………… ————

| 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

Grossman Informational [Page 50] 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

Grossman Informational [Page 51] 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

Grossman Informational [Page 52] 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

Grossman Informational [Page 54] 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.

Grossman Informational [Page 55] 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.,

Grossman Informational [Page 57] RFC 8578 DetNet Use Cases May 2019

    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.

Grossman Informational [Page 58] RFC 8578 DetNet Use Cases May 2019

 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.

Grossman Informational [Page 59] RFC 8578 DetNet Use Cases May 2019

 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

Grossman Informational [Page 60] RFC 8578 DetNet Use Cases May 2019

 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.

Grossman Informational [Page 61] RFC 8578 DetNet Use Cases May 2019

 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].

Grossman Informational [Page 62] RFC 8578 DetNet Use Cases May 2019

 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)

Grossman Informational [Page 67] RFC 8578 DetNet Use Cases May 2019

 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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 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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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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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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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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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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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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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

Grossman Informational [Page 76] 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

Grossman Informational [Page 77] 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.

Grossman Informational [Page 78] 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

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            for Smart-Wind Power Farms", Energies 2014, pp. 3900-3921,
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            Thubert, P., Ed., "An Architecture for IPv6 over the TSCH
            mode of IEEE 802.15.4", Work in Progress,
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            ASHRAE, "Annex J to ANSI/ASHRAE 135-1995 - BACnet/IP",
            January 1999, <http://www.bacnet.org/Addenda/
            Add-1995-135a.pdf>.
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            Kaneko, Y. and S. Das, "Building Automation Use Cases and
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            Progress, draft-bas-usecase-detnet-00, October 2015.
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            Sudhaakar, R., Ed. and P. Zand, "6TiSCH Resource
            Management and Interaction using CoAP", Work in Progress,
            draft-ietf-6tisch-coap-03, March 2015.
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            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.
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            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.
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            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]

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