Internet Engineering Task Force                         E. Grossman, Ed.
Internet-Draft                                                     DOLBY
Intended status: Informational                                C. Gunther
Expires: September 22, 2016                                       HARMAN
                                                              P. Thubert
                                                           P. Wetterwald
                                                              J. Raymond
                                                             J. Korhonen
                                                               Y. Kaneko
                                                                  S. Das
                                          Applied Communication Sciences
                                                                  Y. Zha
                                                                B. Varga
                                                               J. Farkas
                                                                F. Goetz
                                                              J. Schmitt
                                                          March 21, 2016

                   Deterministic Networking Use Cases


   This draft documents requirements in several diverse industries to
   establish multi-hop paths for characterized flows with deterministic
   properties.  In this context deterministic implies that streams can
   be established which provide guaranteed bandwidth and latency which
   can be established from either a Layer 2 or Layer 3 (IP) interface,
   and which can co-exist on an IP network with best-effort traffic.

   Additional requirements include optional redundant paths, very high
   reliability paths, time synchronization, and clock distribution.
   Industries considered include wireless for industrial applications,
   professional audio, electrical utilities, building automation
   systems, radio/mobile access networks, automotive, and gaming.

   For each case, this document will identify the application, identify
   representative solutions used today, and what new uses an IETF DetNet
   solution may enable.

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Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   This Internet-Draft will expire on September 22, 2016.

Copyright Notice

   Copyright (c) 2016 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
   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   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  . . . . . . . . . . . . . . . . . . . . . . . .   5
   2.  Pro Audio and Video . . . . . . . . . . . . . . . . . . . . .   5
     2.1.  Use Case Description  . . . . . . . . . . . . . . . . . .   5
       2.1.1.  Uninterrupted Stream Playback . . . . . . . . . . . .   6
       2.1.2.  Synchronized Stream Playback  . . . . . . . . . . . .   6
       2.1.3.  Sound Reinforcement . . . . . . . . . . . . . . . . .   7
       2.1.4.  Deterministic Time to Establish Streaming . . . . . .   7
       2.1.5.  Secure Transmission . . . . . . . . . . . . . . . . .   8  Safety  . . . . . . . . . . . . . . . . . . . . .   8  Digital Rights Management (DRM) . . . . . . . . .   8
     2.2.  Pro Audio Today . . . . . . . . . . . . . . . . . . . . .   9
     2.3.  Pro Audio Future  . . . . . . . . . . . . . . . . . . . .   9
       2.3.1.  Layer 3 Interconnecting Layer 2 Islands . . . . . . .   9
       2.3.2.  High Reliability Stream Paths . . . . . . . . . . . .   9

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       2.3.3.  Link Aggregation  . . . . . . . . . . . . . . . . . .   9
       2.3.4.  Integration of Reserved Streams into IT Networks  . .  10
       2.3.5.  Use of Unused Reservations by Best-Effort Traffic . .  10
       2.3.6.  Traffic Segregation . . . . . . . . . . . . . . . . .  10  Packet Forwarding Rules, VLANs and Subnets  . . .  11  Multicast Addressing (IPv4 and IPv6)  . . . . . .  11
       2.3.7.  Latency Optimization by a Central Controller  . . . .  11
       2.3.8.  Reduced Device Cost Due To Reduced Buffer Memory  . .  12
     2.4.  Pro Audio Asks  . . . . . . . . . . . . . . . . . . . . .  12
   3.  Electrical Utilities  . . . . . . . . . . . . . . . . . . . .  12
     3.1.  Use Case Description  . . . . . . . . . . . . . . . . . .  12
       3.1.1.  Transmission Use Cases  . . . . . . . . . . . . . . .  13  Protection  . . . . . . . . . . . . . . . . . . .  13  Intra-Substation Process Bus Communications . . .  18  Wide Area Monitoring and Control Systems  . . . .  19  IEC 61850 WAN engineering guidelines requirement
                   classification  . . . . . . . . . . . . . . . . .  20
       3.1.2.  Generation Use Case . . . . . . . . . . . . . . . . .  21
       3.1.3.  Distribution use case . . . . . . . . . . . . . . . .  22  Fault Location Isolation and Service Restoration
                   (FLISR) . . . . . . . . . . . . . . . . . . . . .  22
     3.2.  Electrical Utilities Today  . . . . . . . . . . . . . . .  23
       3.2.1.  Security Current Practices and Limitations  . . . . .  23
     3.3.  Electrical Utilities Future . . . . . . . . . . . . . . .  25
       3.3.1.  Migration to Packet-Switched Network  . . . . . . . .  25
       3.3.2.  Telecommunications Trends . . . . . . . . . . . . . .  26  General Telecommunications Requirements . . . . .  26  Specific Network topologies of Smart Grid
                   Applications  . . . . . . . . . . . . . . . . . .  27  Precision Time Protocol . . . . . . . . . . . . .  28
       3.3.3.  Security Trends in Utility Networks . . . . . . . . .  29
     3.4.  Electrical Utilities Asks . . . . . . . . . . . . . . . .  31
   4.  Building Automation Systems . . . . . . . . . . . . . . . . .  31
     4.1.  Use Case Description  . . . . . . . . . . . . . . . . . .  31
     4.2.  Building Automation Systems Today . . . . . . . . . . . .  31
       4.2.1.  BAS Architecture  . . . . . . . . . . . . . . . . . .  32
       4.2.2.  BAS Deployment Model  . . . . . . . . . . . . . . . .  33
       4.2.3.  Use Cases for Field Networks  . . . . . . . . . . . .  35  Environmental Monitoring  . . . . . . . . . . . .  35  Fire Detection  . . . . . . . . . . . . . . . . .  35  Feedback Control  . . . . . . . . . . . . . . . .  36
       4.2.4.  Security Considerations . . . . . . . . . . . . . . .  36
     4.3.  BAS Future  . . . . . . . . . . . . . . . . . . . . . . .  36
     4.4.  BAS Asks  . . . . . . . . . . . . . . . . . . . . . . . .  37
   5.  Wireless for Industrial . . . . . . . . . . . . . . . . . . .  37
     5.1.  Use Case Description  . . . . . . . . . . . . . . . . . .  37
       5.1.1.  Network Convergence using 6TiSCH  . . . . . . . . . .  38
       5.1.2.  Common Protocol Development for 6TiSCH  . . . . . . .  38

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     5.2.  Wireless Industrial Today . . . . . . . . . . . . . . . .  39
     5.3.  Wireless Industrial Future  . . . . . . . . . . . . . . .  39
       5.3.1.  Unified Wireless Network and Management . . . . . . .  39  PCE and 6TiSCH ARQ Retries  . . . . . . . . . . .  41
       5.3.2.  Schedule Management by a PCE  . . . . . . . . . . . .  42  PCE Commands and 6TiSCH CoAP Requests . . . . . .  42  6TiSCH IP Interface . . . . . . . . . . . . . . .  43
       5.3.3.  6TiSCH Security Considerations  . . . . . . . . . . .  43
     5.4.  Wireless Industrial Asks  . . . . . . . . . . . . . . . .  44
   6.  Cellular Radio  . . . . . . . . . . . . . . . . . . . . . . .  44
     6.1.  Use Case Description  . . . . . . . . . . . . . . . . . .  44
       6.1.1.  Network Architecture  . . . . . . . . . . . . . . . .  44
       6.1.2.  Delay Constraints . . . . . . . . . . . . . . . . . .  45
       6.1.3.  Time Synchronization Constraints  . . . . . . . . . .  46
       6.1.4.  Transport Loss Constraints  . . . . . . . . . . . . .  48
       6.1.5.  Security Considerations . . . . . . . . . . . . . . .  48
     6.2.  Cellular Radio Networks Today . . . . . . . . . . . . . .  48
       6.2.1.  Fronthaul . . . . . . . . . . . . . . . . . . . . . .  48
       6.2.2.  Midhaul and Backhaul  . . . . . . . . . . . . . . . .  49
     6.3.  Cellular Radio Networks Future  . . . . . . . . . . . . .  49
     6.4.  Cellular Radio Networks Asks  . . . . . . . . . . . . . .  51
   7.  Industrial M2M  . . . . . . . . . . . . . . . . . . . . . . .  52
     7.1.  Use Case Description  . . . . . . . . . . . . . . . . . .  52
     7.2.  Industrial M2M Communication Today  . . . . . . . . . . .  53
       7.2.1.  Transport Parameters  . . . . . . . . . . . . . . . .  53
       7.2.2.  Stream Creation and Destruction . . . . . . . . . . .  54
     7.3.  Industrial M2M Future . . . . . . . . . . . . . . . . . .  54
     7.4.  Industrial M2M Asks . . . . . . . . . . . . . . . . . . .  54
   8.  Internet-based Applications . . . . . . . . . . . . . . . . .  55
     8.1.  Use Case Description  . . . . . . . . . . . . . . . . . .  55
       8.1.1.  Media Content Delivery  . . . . . . . . . . . . . . .  55
       8.1.2.  Online Gaming . . . . . . . . . . . . . . . . . . . .  55
       8.1.3.  Virtual Reality . . . . . . . . . . . . . . . . . . .  55
     8.2.  Internet-Based Applications Today . . . . . . . . . . . .  55
     8.3.  Internet-Based Applications Future  . . . . . . . . . . .  55
     8.4.  Internet-Based Applications Asks  . . . . . . . . . . . .  56
   9.  Use Case Common Elements  . . . . . . . . . . . . . . . . . .  56
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  57
     10.1.  Pro Audio  . . . . . . . . . . . . . . . . . . . . . . .  57
     10.2.  Utility Telecom  . . . . . . . . . . . . . . . . . . . .  57
     10.3.  Building Automation Systems  . . . . . . . . . . . . . .  58
     10.4.  Wireless for Industrial  . . . . . . . . . . . . . . . .  58
     10.5.  Cellular Radio . . . . . . . . . . . . . . . . . . . . .  58
     10.6.  Industrial M2M . . . . . . . . . . . . . . . . . . . . .  58
     10.7.  Internet Applications and CoMP . . . . . . . . . . . . .  58
   11. Informative References  . . . . . . . . . . . . . . . . . . .  58
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  68

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1.  Introduction

   This draft presents use cases from diverse industries which have in
   common a need for deterministic streams, but which also differ
   notably in their network topologies and specific desired behavior.
   Together, they provide broad industry context for DetNet and a
   yardstick against which proposed DetNet designs can be measured (to
   what extent does a proposed design satisfy these various use cases?)

   For DetNet, use cases explicitly do not define requirements; The
   DetNet WG will consider the use cases, decide which elements are in
   scope for DetNet, and the results will be incorporated into future
   drafts.  Similarly, the DetNet use case draft explicitly does not
   suggest any specific design, architecture or protocols, which will be
   topics of future drafts.

   We present for each use case the answers to the following questions:

   o  What is the use case?

   o  How is it addressed today?

   o  How would you like it to be addressed in the future?

   o  What do you want the IETF to deliver?

   The level of detail in each use case should be sufficient to express
   the relevant elements of the use case, but not more.

   At the end we consider the use cases collectively, and examine the
   most significant goals they have in common.

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
      (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 (or small number of)
   signals per link, interconnected with purpose-built hardware.

   These industries are now transitioning to packet-based infrastructure
   to reduce cost, increase routing flexibility, and integrate with
   existing IT infrastructure.

   Today ProAV applications have no way to establish deterministic
   streams from a standards-based Layer 3 (IP) interface, which is a
   fundamental limitation to the use cases described here.  Today
   deterministic streams can be created within standards-based layer 2
   LANs (e.g. using IEEE 802.1 AVB) however these 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 streams could be routed over the
   open Internet, however solutions with more limited scope (e.g.
   enterprise networks) would still provide a substantial improvement.

   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 because uninterrupted stream playback in the
   presence of network errors cannot be achieved by re-trying the
   transmission; by the time the missing or corrupt packet has been
   identified it is too late to execute a re-try 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

   Streams with guaranteed bandwidth can eliminate congestion on the
   network as a cause of transmission errors that would lead to playback
   interruption.  Use of redundant paths can further mitigate
   transmission errors to provide greater stream reliability.

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 and video streams must be bounded and consistent if
   the sound is to remain matched to the movement in the video.  A

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   common tolerance for audio/video sync is one NTSC video frame (about
   33ms) and to maintain the audience 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) is to enable measurement of the latency of each path, and
   have 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 which 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 any of various

   This type of architecture is commonly implemented using a central
   controller that determines path delays and arbitrates buffering

2.1.3.  Sound Reinforcement

   Consider the latency (delay) from when a person speaks into a
   microphone to when their voice emerges from the speaker.  If this
   delay is longer than about 10-15 milliseconds 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 may know this experience).

   Note that the 15ms latency bound includes all parts of the signal
   path, not just the network, so the network latency must be
   significantly less than 15ms.

   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 (33ms for NTSC video).

   In cases where audio phase is a consideration, for example beam-
   forming using multiple speakers, latency requirements can be in the
   10 microsecond range (1 audio sample at 96kHz).

2.1.4.  Deterministic Time to Establish Streaming

   Some audio systems installed in public environments (airports,
   hospitals) have unique requirements with regards to health, safety
   and fire concerns.  One such requirement is a maximum of 3 seconds
   for a system to respond to an emergency detection and begin sending
   appropriate warning signals and alarms without human intervention.

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   For this requirement to be met, the system must support a bounded and
   acceptable time from a notification signal to specific stream
   establishment.  For further details see [ISO7240-16].

   Similar requirements apply when the system is restarted after a power
   cycle, cable re-connection, or system reconfiguration.

   In many cases such re-establishment of streaming state must be
   achieved by the peer devices themselves, i.e. without a central
   controller (since such a controller may only be present during
   initial network configuration).

   Video systems introduce related requirements, for example when
   transitioning from one camera feed (video stream) to another (see
   [STUDIO_IP] and [ESPN_DC2]).

2.1.5.  Secure Transmission  Safety

   Professional audio systems can include amplifiers that are capable of
   generating hundreds or thousands of watts of audio power which if
   used incorrectly 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).  Digital Rights Management (DRM)

   Digital Rights Management (DRM) is very important to the audio and
   video industries.  Any time protected content is introduced into a
   network there are DRM concerns that must be maintained (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 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 may be retransmitted under HDCP.
   Therefore if the source of a stream is outside of the network and it
   uses HDCP protection it is only allowed to be placed on the network
   with that same HDCP protection.

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2.2.  Pro Audio Today

   Some proprietary systems have been created which enable deterministic
   streams at Layer 3 however they are "engineered networks" which
   require careful configuration to operate, often require that the
   system be over-provisioned, and 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, and we believe that establishing relevant IETF standards
   is a crucial factor.

2.3.  Pro Audio 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 recently constructed a state-of-the-art 194,000
   sq ft, $125 million broadcast studio called 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 AVB) 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.

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 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

2.3.3.  Link Aggregation

   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 of the

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   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.

2.3.4.  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 not compromise use of the
   network for best effort (non-time-sensitive) traffic.

2.3.5.  Use of Unused Reservations by Best-Effort Traffic

   In cases where stream bandwidth is reserved but not currently used
   (or is under-utilized) 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 un-
   reserve it even though they are not using it, and soon the network
   will have no bandwidth left").

2.3.6.  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 one thousand seat theater can generate
   enough broadcast traffic to overwhelm a low powered CPU.  Thus an
   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.

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   There are many techniques that can be used to support this
   requirement including (but not limited to) the following examples.  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 using other means for example VLANs or IP subnets.  Multicast Addressing (IPv4 and IPv6)

   Multicast addressing is commonly used to keep bandwidth utilization
   of shared links to a minimum.

   Because of the MAC Address forwarding nature of Layer 2 bridges it is
   important that a multicast MAC address is only 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.

   Since each multicast MAC Address can represent 32 different IPv4
   multicast addresses there must be a process put in place to make sure
   this does not occur.  Requiring use of IPv6 address can achieve this,
   however due to their continued prevalence, solutions that are
   effective for IPv4 installations are also required.

2.3.7.  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 farther away sinks.  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].

   Additional optimization can be achieved in cases where sinks have
   differing latency requirements, for example in a live outdoor concert
   the speaker sinks have stricter latency requirements than the
   recording hardware sinks.  See slide 7 of [SRP_LATENCY].

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2.3.8.  Reduced Device Cost Due To Reduced Buffer Memory

   Device cost 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 proportional to the
   latency bounds and jitter caused by delivery, which depends on the
   worst case segment of the end-to-end network path.  For example on
   todays 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 the identical packets as those sent by the source
   and would be unaware that there were any latency or jitter issues
   along the path.

2.4.  Pro Audio Asks

   o  Layer 3 routing on top of AVB (and/or other high QoS 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

   o  IT department friendly

   o  Enterprise-wide networks (e.g. size of San Francisco but not the
      whole Internet (yet...))

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.
   Here we present use cases in Transmission, Generation and
   Distribution, including key timing and reliability metrics.  We also
   discuss security issues and industry trends which affect the
   architecture of next generation utility networks

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3.1.1.  Transmission Use Cases  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.  Key Criteria

   The key criteria for measuring teleprotection performance are command
   transmission time, dependability and security.  These criteria are
   defined by the IEC standard 60834 as follows:

   o  Transmission time (Speed): The time between the moment where state
      changes at the transmitter input and the moment of the
      corresponding change at the receiver output, including propagation
      delay.  Overall operating time for a teleprotection system
      includes the time for initiating the command at the transmitting
      end, the propagation delay over the network (including equipments)
      and the selection and decision time at the receiving end,
      including any additional delay due to a noisy environment.

   o  Dependability: The ability to issue and receive valid commands in
      the presence of interference and/or noise, by minimizing the
      probability of missing command (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 bit error
      rate (BER) level.

   Additional elements of the the teleprotection system that impact its
   performance include:

   o  Network bandwidth

   o  Failure recovery capacity (aka resiliency)

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Internet-Draft              DetNet Use Cases                  March 2016  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 total fault clearance time of 100ms.  As a safety precaution,
   however, actual operation time of protection systems is limited to
   70- 80 percent of this period, including fault recognition time,
   command transmission time and line breaker switching time.

   Some system components, such as large electromechanical switches,
   require particularly long time to operate and take up the majority of
   the total clearance time, leaving only a 10ms window for the
   telecommunications part of the protection scheme, independent of the
   distance to travel.  Given the sensitivity of the issue, new networks
   impose requirements that are even more stringent: IEC standard 61850
   limits the transfer time for protection messages to 1/4 - 1/2 cycle
   or 4 - 8ms (for 60Hz lines) for the most critical messages.  Symmetric Channel Delay

   Teleprotection channels which are differential must be synchronous,
   which means that any delays on the transmit and receive paths must
   match each other.  Teleprotection systems ideally support zero
   asymmetric delay; typical legacy relays can tolerate delay
   discrepancies of up to 750us.

   Some tools available for lowering delay variation below this
   threshold are:

   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 packet 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
      1588-2008 Precision Time Protocol (PTP) and Synchronous Ethernet
      (Sync-E), can help keep networks stable by maintaining a highly
      accurate clock source on the various network devices.

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Internet-Draft              DetNet Use Cases                  March 2016  Teleprotection Network Requirements (IEC 61850)

   The following table captures the main network metrics as based on the
   IEC 61850 standard.

   |  Teleprotection Requirement |              Attribute              |
   |    One way maximum delay    |               4-10 ms               |
   |   Asymetric delay required  |                 Yes                 |
   |        Maximum jitter       | less than 250 us (750 us for legacy |
   |                             |                 IED)                |
   |           Topology          |   Point to point, point to Multi-   |
   |                             |                point                |
   |         Availability        |               99.9999               |
   |   precise timing required   |                 Yes                 |
   |    Recovery time on node    |       less than 50ms - hitless      |
   |           failure           |                                     |
   |    performance management   |            Yes, Mandatory           |
   |          Redundancy         |                 Yes                 |
   |         Packet loss         |              0.1% to 1%             |

               Table 1: Teleprotection network requirements  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.

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   |     Inter-Trip protection      |            Attribute             |
   |          Requirement           |                                  |
   |     One way maximum delay      |               5 ms               |
   |    Asymetric delay required    |                No                |
   |         Maximum jitter         |           Not critical           |
   |            Topology            | Point to point, point to Multi-  |
   |                                |              point               |
   |           Bandwidth            |             64 Kbps              |
   |          Availability          |             99.9999              |
   |    precise timing required     |               Yes                |
   | Recovery time on node failure  |     less than 50ms - hitless     |
   |     performance management     |          Yes, Mandatory          |
   |           Redundancy           |               Yes                |
   |          Packet loss           |               0.1%               |

            Table 2: Inter-Trip protection network requirements  Current Differential Protection Scheme

   Current differential protection is commonly used for line protection,
   and is typical for protecting parallel circuits.  At both end of the
   lines the current is measured by the differential relays, and 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 some form of communications being present
   between the relays at both end of the line, to allow both relays to
   compare measured current values.  Line differential protection
   schemes assume a very low telecommunications delay between both
   relays, often as low as 5ms.  Moreover, as those systems are often
   not time-synchronized, they also assume symmetric telecommunications
   paths with constant delay, which allows comparing current measurement
   values taken at the exact same time.

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   | Current Differential protection  |           Attribute            |
   |           Requirement            |                                |
   |      One way maximum delay       |              5 ms              |
   |     Asymetric delay Required     |              Yes               |
   |          Maximum jitter          |  less than 250 us (750us for   |
   |                                  |          legacy IED)           |
   |             Topology             |    Point to point, point to    |
   |                                  |          Multi-point           |
   |            Bandwidth             |            64 Kbps             |
   |           Availability           |            99.9999             |
   |     precise timing required      |              Yes               |
   |  Recovery time on node failure   |    less than 50ms - hitless    |
   |      performance management      |         Yes, Mandatory         |
   |            Redundancy            |              Yes               |
   |           Packet loss            |              0.1%              |

             Table 3: Current Differential Protection metrics  Distance Protection Scheme

   Distance (Impedance Relay) protection scheme is based on voltage and
   current measurements.  The network metrics are similar (but not
   identical to) Current Differential protection.

   |      Distance protection      |             Attribute             |
   |          Requirement          |                                   |
   |     One way maximum delay     |                5 ms               |
   |    Asymetric delay Required   |                 No                |
   |         Maximum jitter        |            Not critical           |
   |            Topology           |  Point to point, point to Multi-  |
   |                               |               point               |
   |           Bandwidth           |              64 Kbps              |
   |          Availability         |              99.9999              |
   |    precise timing required    |                Yes                |
   | Recovery time on node failure |      less than 50ms - hitless     |
   |     performance management    |           Yes, Mandatory          |
   |           Redundancy          |                Yes                |
   |          Packet loss          |                0.1%               |

                 Table 4: Distance Protection requirements

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Internet-Draft              DetNet Use Cases                  March 2016  Inter-Substation Protection Signaling

   This use case describes the exchange of Sampled Value and/or GOOSE
   (Generic Object Oriented Substation Events) message between
   Intelligent Electronic Devices (IED) in two substations for
   protection and tripping coordination.  The two IEDs are in a 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
   61850-9-2 sampled values to the slave IED.  The slave IED forwards
   the 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 trip for breaker
   tripping, it opens the breaker.  It then sends a confirmation message
   back to the master.  All data exchanges between IEDs are either
   through Sampled Value and/or GOOSE messages.

   |   Inter-Substation protection    |           Attribute            |
   |           Requirement            |                                |
   |      One way maximum delay       |              5 ms              |
   |     Asymetric delay Required     |               No               |
   |          Maximum jitter          |          Not critical          |
   |             Topology             |    Point to point, point to    |
   |                                  |          Multi-point           |
   |            Bandwidth             |            64 Kbps             |
   |           Availability           |            99.9999             |
   |     precise timing required      |              Yes               |
   |  Recovery time on node failure   |    less than 50ms - hitless    |
   |      performance management      |         Yes, Mandatory         |
   |            Redundancy            |              Yes               |
   |           Packet loss            |               1%               |

             Table 5: Inter-Substation Protection requirements  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 send the
   sampled value (analog voltage or current) to the MU over hard wire.
   The MU sends the time-synchronized 61850-9-2 sampled values to the
   IEDs in the substation in GOOSE message format.  The GPS Master Clock
   can send 1PPS or IRIG-B format to the MU through a serial port or

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   IEEE 1588 protocol via a network.  Process bus communication using
   61850 simplifies connectivity within the substation and 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              |
   |     Asymetric delay Required     |               No               |
   |          Maximum jitter          |          Not critical          |
   |             Topology             |    Point to point, point to    |
   |                                  |          Multi-point           |
   |            Bandwidth             |            64 Kbps             |
   |           Availability           |            99.9999             |
   |     precise timing required      |              Yes               |
   |  Recovery time on Node failure   |    less than 50ms - hitless    |
   |      performance management      |         Yes, Mandatory         |
   |            Redundancy            |            Yes - No            |
   |           Packet loss            |              0.1%              |

             Table 6: Intra-Substation Protection requirements  Wide Area Monitoring and Control Systems

   The application of synchrophasor measurement data from Phasor
   Measurement Units (PMU) 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 real-time nature of
   synchrophasor data presents unique challenges for existing
   application architectures.  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, WAMS has stringent telecommunications
   requirements in an IP network that are captured in the following

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   |   WAMS Requirement   |                 Attribute                  |
   |   One way maximum    |                   50 ms                    |
   |        delay         |                                            |
   |   Asymetric delay    |                     No                     |
   |       Required       |                                            |
   |    Maximum jitter    |                Not critical                |
   |       Topology       |   Point to point, point to Multi-point,    |
   |                      |         Multi-point to Multi-point         |
   |      Bandwidth       |                  100 Kbps                  |
   |     Availability     |                  99.9999                   |
   |    precise timing    |                    Yes                     |
   |       required       |                                            |
   |   Recovery time on   |          less than 50ms - hitless          |
   |     Node failure     |                                            |
   |     performance      |               Yes, Mandatory               |
   |      management      |                                            |
   |      Redundancy      |                    Yes                     |
   |     Packet loss      |                     1%                     |

             Table 7: WAMS Special Communication Requirements  IEC 61850 WAN engineering guidelines requirement

   The IEC (International Electrotechnical Commission) has recently
   published a Technical Report which offers guidelines on how to define
   and deploy Wide Area Networks for the interconnections of electric
   substations, generation plants and SCADA operation centers.  The IEC
   61850-90-12 is providing a classification of WAN communication
   requirements into 4 classes.  Table 8 summarizes these requirements:

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   |      WAN       |  Class WA  |  Class WB  |  Class WC  |  Class WD |
   |  Requirement   |            |            |            |           |
   |  Application   | EHV (Extra |  HV (High  | MV (Medium |  General  |
   |     field      |    High    |  Voltage)  |  Voltage)  |  purpose  |
   |                |  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  |
   |    Asymetry    |            |            |            |           |
   | Time Accuracy  |    1 us    |   10 us    |   100 us   | 10 to 100 |
   |                |            |            |            |     ms    |
   | Bit Error rate |  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   |
   | Cyber security | extremely  |    High    |   Medium   |   Medium  |
   |                |    high    |            |            |           |

     Table 8: 61850-90-12 Communication Requirements; Courtesy of IEC

3.1.2.  Generation Use Case

   The electrical power generation frequency should 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.

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   |   FCAG (Frequency Control Automatic Generation)   |   Attribute   |
   |                    Requirement                    |               |
   |               One way maximum delay               |     500 ms    |
   |              Asymetric 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

3.1.3.  Distribution use case  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.

   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.

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   |  FLISR Requirement   |                 Attribute                  |
   |   One way maximum    |                   80 ms                    |
   |        delay         |                                            |
   |   Asymetric delay    |                     No                     |
   |       Required       |                                            |
   |    Maximum jitter    |                   40 ms                    |
   |       Topology       |   Point to point, point to Multi-point,    |
   |                      |         Multi-point to Multi-point         |
   |      Bandwidth       |                  64 Kbps                   |
   |     Availability     |                  99.9999                   |
   |    precise timing    |                    Yes                     |
   |       required       |                                            |
   |   Recovery time on   |         Depends on customer impact         |
   |     Node failure     |                                            |
   |     performance      |               Yes, Mandatory               |
   |      management      |                                            |
   |      Redundancy      |                    Yes                     |
   |     Packet loss      |                    0.1%                    |

                Table 10: FLISR Communication Requirements

3.2.  Electrical Utilities Today

   Many utilities still rely on complex environments formed of multiple
   application-specific proprietary networks, including TDM networks.

   In this kind of environment there is no mixing of OT and IT
   applications on the same network, and information is siloed between
   operational areas.

   Specific calibration of the full chain is required, which is costly.

   This kind of environment prevents utility operations from realizing
   the operational efficiency benefits, visibility, and functional
   integration of operational information across grid applications and
   data networks.

   In addition, there are many security-related issues as discussed in
   the following section.

3.2.1.  Security Current Practices and Limitations

   Grid monitoring and control devices are already targets for cyber
   attacks, and legacy telecommunications protocols have many intrinsic
   network-related vulnerabilities.  For example, DNP3, Modbus,

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   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 retrieve data (reading
   inputs) or control (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 command-and-control like functionality.  Specific
   security concerns common to most industrial control, including
   utility telecommunication 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-off
      devices, forcing them into a listen-only state, disabling

   o  Protocol commands may be available that are capable of restarting
      communications and otherwise interrupting processes.

   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; therefore it is 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

   o  Protocol commands may be available to query the device network to
      obtain defined points and their values (i.e. a configuration

   o  Protocol commands may be available that will list all available
      function codes (i.e. a function scan).

   These inherent vulnerabilities, along with increasing connectivity
   between IT an OT networks, make network-based attacks very feasible.

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   Simple injection of malicious protocol commands provides 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 provide both control over a process and misrepresentation of
   data back to operator consoles.

3.3.  Electrical Utilities 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 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 telecommunnications network will
   be based on open-standards-based IP architecture.  An end-to-end IP
   architecture takes advantage of nearly three decades of IP technology
   development, facilitating interoperability across disparate networks
   and devices, as it has been already demonstrated in many mission-
   critical and highly secure networks.

   IPv6 is seen as a future telecommunications technology for the Smart
   Grid; the IEC (International Electrotechnical Commission) and
   different National Committees have mandated a specific adhoc group
   (AHG8) to define the migration strategy to IPv6 for all the IEC TC57
   power automation standards.

3.3.1.  Migration to Packet-Switched Network

   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

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   across the utility's Wide Area Network (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-based

   o  Physical safety and security data (e.g. voice and video)

   o  Remote worker access to corporate applications (voice, maps,
      schematics, etc.)

   o  Field area network backhaul for smart metering, and distribution
      grid management

   o  Enterprise traffic (email, collaboration tools, business

   WANs support this wide variety of traffic to and from substations,
   the transmission and distribution grid, 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 time-division multiplexing (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.

3.3.2.  Telecommunications Trends

   These general telecommunications topics are 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.  General Telecommunications Requirements

   o  IP Connectivity everywhere

   o  Monitoring services everywhere and from different remote centers

   o  Move services to a virtual data center

   o  Unify access to applications / information from the corporate

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   o  Unify services

   o  Unified Communications Solutions

   o  Mix of fiber and microwave technologies - obsolescence of SONET/
      SDH or TDM

   o  Standardize grid telecommunications protocol to opened standard to
      ensure interoperability

   o  Reliable Telecommunications for Transmission and Distribution

   o  IEEE 1588 time synchronization Client / Server Capabilities

   o  Integration of Multicast Design

   o  QoS Requirements Mapping

   o  Enable Future Network Expansion

   o  Substation Network Resilience

   o  Fast Convergence Design

   o  Scalable Headend Design

   o  Define Service Level Agreements (SLA) and Enable SLA Monitoring

   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 PMU (Phaser Measurement Unit) on IP  Specific Network topologies of Smart Grid Applications

   Utilities often have very large private telecommunications networks.
   It covers an entire territory / country.  The main purpose of the
   network, until now, has been to support transmission network
   monitoring, control, and automation, remote control of generation
   sites, and providing FCAPS (Fault, Configuration, Accounting,
   Performance, Security) services from centralized network operation

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   Going forward, one network will support operation and maintenance of
   electrical networks (generation, transmission, and distribution),
   voice and data services for ten of thousands of employees and for
   exchange with neighboring interconnections, and administrative
   services.  To meet those requirements, utility may deploy several
   physical networks leveraging different technologies across the
   country: an optical network and a microwave network for instance.
   Each protection and automatism 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 shall 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 and
   telephone cables.  This network is the nervous system of the
   utility's power transmission operations.  The optical network
   represents ten of thousands of km of cable deployed along the power
   lines, with individual runs as long as 280 km.  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 under ground 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
   1ms timestamps for IRIG-B.

   Some companies plan to transition to the Precision Time Protocol
   (PTP, [IEEE1588]), 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

   PTP operates based on the following assumptions:

      It is assumed that the network eliminates cyclic forwarding of PTP
      messages within each communication path (e.g. by using a spanning
      tree protocol).

      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.

      PTP was designed assuming a multicast communication model, however
      PTP also supports a unicast communication model as long as the
      behavior of the protocol is preserved.

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      Like all message-based time transfer protocols, PTP time accuracy
      is degraded by delay asymmetry in the paths taken by event
      messages.  Asymmetry is not detectable by PTP, however, if such
      delays are known a priori, PTP can correct for asymmetry.

   IEC 61850 will recommend the use of the IEEE PTP 1588 Utility Profile
   (as defined in [IEC62439-3:2012] Annex B) which offers the support of
   redundant attachment of clocks to Parallel Redundancy Protcol (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

   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, as well as 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.

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   "Cyber security" 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 : the telecommunications parties involved must be
      validated as genuine

   o  Authorization : only requests and commands from the 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.  Consequences of a cyber attack on the
   grid telecommunications network can be catastrophic.  This is why
   security for smart grid is not just an ad hoc feature or product,
   it's a complete framework integrating both physical and Cyber
   security 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.  Migrating to IP based protocols is key to address 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, which allows interoperability
      between different vendors and products, driving down the costs
      associated with implementing security solutions in OT networks.

   Securing OT (Operation technology) telecommunications over packet-
   switched IP networks follow the same principles that are foundational
   for securing the IT infrastructure, i.e., consideration must be given
   to enforcing electronic access control for both person-to-machine and
   machine-to-machine communications, and providing the appropriate
   levels of data privacy, device and platform integrity, and threat
   detection and mitigation.

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3.4.  Electrical Utilities Asks

   o  Mixed L2 and L3 topologies

   o  Deterministic behavior

   o  Bounded latency and jitter

   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

4.1.  Use Case Description

   A Building Automation System (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.

   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, etc.

   o  Stores the measured data.

   o  Provides the measured data to BAS systems and operators.

   o  Generates alarms for abnormal state of devices.

   o  Controls devices (e.g. turn off room lights at 10:00 PM).

4.2.  Building Automation Systems Today

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4.2.1.  BAS Architecture

   A typical BAS architecture of today is shown in Figure 1.

                         |                            |
                         |       BMS        HMI       |
                         |        |          |        |
                         |  +----------------------+  |
                         |  |  Management Network  |  |
                         |  +----------------------+  |
                         |        |          |        |
                         |        LC         LC       |
                         |        |          |        |
                         |  +----------------------+  |
                         |  |     Field Network    |  |
                         |  +----------------------+  |
                         |     |     |     |     |    |
                         |    Dev   Dev   Dev   Dev   |
                         |                            |

                         BMS := Building Management Server
                         HMI := Human Machine Interface
                         LC  := Local Controller

                        Figure 1: BAS architecture

   There are typically two layers of network in a BAS.  The upper one is
   called the Management Network and the lower one is called the Field
   Network.  In management networks an IP-based communication protocol
   is used, while in field networks non-IP based communication protocols
   ("field protocols") are mainly used.  Field networks have specific
   timing requirements, whereas management networks can be best-effort.

   A Human Machine Interface (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  Collect and store device states from LCs at regular intervals.

   o  Send control values to LCs according to a building schedule.

   o  Send an alarm signal to operators if it detects abnormal devices

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   The BMS and HMI communicate with LCs via IP-based "management
   protocols" (see standards [bacnetip], [knx]).

   A LC is typically a Programmable Logic Controller (PLC) which is
   connected to several tens or hundreds of devices using "field
   protocols".  An LC performs the following kinds of operations:

   o  Measure device states and provide the information to BMS or HMI.

   o  Send control values to devices, unilaterally or as part of a
      feedback control loop.

   There are many field protocols used today; some are standards-based
   and others are proprietary (see standards [lontalk], [modbus],
   [profibus] and [flnet]).  The result is that BASs have multiple MAC/
   PHY modules and interfaces.  This makes BASs more expensive, slower
   to develop, and can result in "vendor lock-in" with multiple types of
   management applications.

4.2.2.  BAS Deployment Model

   An example BAS for medium or large buildings is shown in Figure 2.
   The physical layout spans multiple floors, and there is a monitoring
   room where the BAS management entities are located.  Each floor will
   have one or more LCs depending upon the number of devices connected
   to the field network.

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               |                                          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 2: 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 non-
   realtime, use of Ethernet without quality of service is sufficient
   for today's deployment.

   In the field network a variety of physical interfaces such as RS232C
   and RS485 are used, which have specific timing requirements.  Thus if
   a field network is to be replaced with an Ethernet or wireless
   network, such networks must support time-critical deterministic

   In Figure 3, another deployment model is presented in which the
   management system is hosted remotely.  This is becoming popular for
   small office and residential buildings in which a standalone
   monitoring system is not cost-effective.

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                                                     | Remote Center |
                                                     |               |
                                                     |  BMS     HMI  |
            +------------------------------------+   |   |       |   |
            |                            Floor 2 |   |   +---+---+   |
            |    +----LC~~~~+~~~~~+ Field Network|   |       |       |
            |    |          |     |              |   |     Router    |
            |    |         Dev   Dev             |   +-------|-------+
            |    |                               |           |
            |--- | ------------------------------|           |
            |    |                       Floor 1 |           |
            |    +----LC~~~~+~~~~~+              |           |
            |    |          |     |              |           |
            |    |         Dev   Dev             |           |
            |    |                               |           |
            |    |   Management Network          |     WAN   |
            |    +------------------------Router-------------+
            |                                    |

              Figure 3: Deployment model for Small Buildings

   Some interoperability is possible today in the Management Network,
   but not 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.  Environmental Monitoring

   The BMS polls each LC at a maximum measurement interval of 100ms (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 values are completed in the
   measurement interval.  Availability is expected to be 99.999 %.  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 ~10s of sensors per LC that BMS needs to manage.  In this

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   scenario the measurement interval is 10-50ms, the communication delay
   is 10ms, and the availability must be 99.9999 %.  Feedback Control

   BAS systems utilize feedback control in various ways; the most time-
   critial is control of DC motors, which require a short feedback
   interval (1-5ms) with low communication delay (10ms) and jitter
   (1ms).  The feedback interval depends on the characteristics of the
   device and a target quality of control value.  There are typically
   ~10s of such devices per LC.

   Communication delay is expected to be less than 10 ms, jitter less
   than 1 sec while the availability must be 99.9999% .

4.2.4.  Security Considerations

   When BAS field networks were developed it was assumed that the field
   networks would always be physically isolated from external networks
   and therefore security was not a concern.  In today's world many BASs
   are managed remotely and are thus connected to shared IP networks and
   so security is definitely a concern, yet security features are not
   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 BAS
   systems do not implement even the available security features such as
   device authentication or encryption for data in transit.

4.3.  BAS Future

   In the future we expect more fine-grained environmental monitoring
   and lower energy consumption, which will require more sensors and
   devices, thus requiring larger and more complex building networks.

   We expect building networks to be connected to or converged with
   other networks (Enterprise network, Home network, and 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
   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.

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4.4.  BAS Asks

   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 <10ms to 100ms in a network of
      several hundred devices)

   o  Low jitter (< 1 ms)

   o  Tight feedback intervals (1ms - 10ms)

   o  High network availability (up to 99.9999% )

   o  Availability of network data in disaster scenario

   o  Authentication between management and field devices (both local
      and remote)

   o  Integrity and data origin authentication of communication data
      between field and management devices

   o  Confidentiality of data when communicated to a remote device

5.  Wireless for Industrial

5.1.  Use Case Description

   Wireless networks are useful for industrial applications, for example
   when portable, fast-moving or rotating objects are involved, and for
   the resource-constrained devices found in the Internet of Things

   Such network-connected sensors, actuators, control loops (etc.)
   typically require that the underlying network support real-time
   quality of service (QoS), as well as specific classes of other
   network properties such as reliability, redundancy, and security.

   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

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   market.  For example, a 1% cost reduction in some areas could save

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.  For
   example WiFi is pervasive but does not provide guaranteed timing or
   delivery of packets, and thus is not useful in this context.

   In this use case we focus on one specific wireless network technology
   which does provide the required deterministic QoS, which is "IPv6
   over the TSCH mode of IEEE 802.15.4e" (6TiSCH, where TSCH stands for
   "Time-Slotted Channel Hopping", see [I-D.ietf-6tisch-architecture],
   [IEEE802154], [IEEE802154e], and [RFC7554]).

   There are other deterministic wireless busses and networks available
   today, however they are imcompatible with each other, and
   incompatible with IP traffic (for example [ISA100], [WirelessHART]).

   Thus the primary goal of this use case is to apply 6TiSH as a
   converged IP- and standards-based wireless network for industrial
   applications, i.e. to replace multiple proprietary and/or
   incompatible wireless networking and wireless network management

5.1.2.  Common Protocol Development for 6TiSCH

   Today there are a number of protocols required by 6TiSCH which are
   still in development, and a second intent 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
   which contribute to the eficiency of enabling both DetNet and 6TiSCH.

   One such commonality is that although at a different time scale, in
   both TSN [IEEE802.1TSNTG] and TSCH a packet crosses the network from
   node to node follows a precise schedule, as a train that leaves
   intermediate stations at precise times along its path.  This kind of
   operation reduces collisions, saves energy, and enables engineering
   the network for deterministic properties.

   Another commonality is remote monitoring and scheduling management of
   a TSCH network by a Path Computation Element (PCE) and Network

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   Management Entity (NME).  The PCE/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, and will have limited bandwidth between peers such that it
   can maintain only a small amount of peer information, and will not be
   able to store many packets waiting to be forwarded.  It is
   advantageous then for it to only be required to carry out the
   specific behavior assigned to it by the PCE/NME (as opposed to
   maintaining its own IP stack, for example).

   6TiSCH depends on [PCE] and [I-D.finn-detnet-architecture], and we
   expect that DetNet will maintain consistency with [IEEE802.1TSNTG].

5.2.  Wireless Industrial Today

   Today industrial wireless is accomplished using multiple
   deterministic wireless networks which are incompatible with each
   other and with IP traffic.

   6TiSCH is not yet fully specified, so it cannot be used in today's

5.3.  Wireless Industrial Future

5.3.1.  Unified Wireless Network and Management

   We expect DetNet and 6TiSCH together to enable converged transport of
   deterministic and best-effort traffic flows between real-time
   industrial devices and wide area networks via IP routing.  A high
   level view of a basic such network is shown in Figure 4.

               ---+-------- ............ ------------
                  |      External Network       |
                  |                          +-----+
               +-----+                       | NME |
               |     | LLN Border            |     |
               |     | router                +-----+
             o    o   o
      o     o   o     o
         o   o LLN   o    o     o
            o   o   o       o

                      Figure 4: Basic 6TiSCH Network

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   Figure 5 shows a backbone router federating multiple synchronized
   6TiSCH subnets into a single subnet connected to the external

                  ---+-------- ............ ------------
                     |      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 5: Extended 6TiSCH Network

   The backbone router must ensure end-to-end deterministic behavior
   between the LLN and the backbone.  We would like to see this
   accomplished in conformance with the work done in
   [I-D.finn-detnet-architecture] 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 IEEE802.1 TSN Ethernet backbone, and DetNet protocols are
   expected to enable end-to-end deterministic forwarding.

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                     | 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

                     Figure 6: 6TiSCH Network with PRE  PCE and 6TiSCH ARQ Retries

   6TiSCH uses the IEEE802.15.4 Automatic Repeat-reQuest (ARQ) mechanism
   to provide higher reliability of packet delivery.  ARQ is related to
   packet replication and elimination because there are two independent
   paths for packets to arrive at the destination, and if an expected
   packed 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 may be a technique that would be appropriate for DetNet and so
   aspects of the enabling protocol could be co-developed.

   For example, in Figure 6, a Track is laid out from a field device in
   a 6TiSCH network to an IoT gateway that is located on a IEEE802.1 TSN

   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 case of a loss on one branch, hopefully the other copy
   of the packet still arrives 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.

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   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).

   In current deployments, a TSCH Track does not necessarily support PRE
   but is systematically multi-path.  This means that a Track is
   scheduled so as to ensure that each hop has at least two forwarding
   solutions, and the forwarding decision is to try the preferred one
   and use the other in 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 the action of a PCE to
   configure 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.  We expect that this protocol will be
   developed by DetNet with consideration for its reuse by 6TiSCH.  The
   remainder of this section provides a bit more context from the 6TiSCH
   side.  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 required traffic specification 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, and the flow identification that
   enables recognizing that a certain packet belongs to a certain path,

   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, which incorporates the aggregation of its
   behavior for multiple paths. 6TiSCH expects that the programing of
   the schedule will be done over COAP as discussed in

   6TiSCH expects that the PCE commands will be issued directly as CoAP
   requests or 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 PCEP into the RESTful interfaces that the 6TiSCH devices support.
   This architecture will be refined to comply with DetNet
   [I-D.finn-detnet-architecture] when the work is formalized.  Related

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   information about 6TiSCH can be found at
   [I-D.ietf-6tisch-6top-interface] and RPL [RFC6550].

   If it appears that a path through the network does not perform as
   expected, a protocol may be used to update the state in the devices,
   but in 6TiSCH that flow was not designed and no protocol was selected
   and it is expected that DetNet will determine the appropriate end-to-
   end protocols to be used in that case.

   A "slotFrame" is the base object that the PCE needs to manipulate to
   program a schedule into an LLN node ([I-D.ietf-6tisch-architecture]).

   The PCE should be able to 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
   exceeded the available energy over a period of time.

   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 neighborhood information
   to a PCE.  DetNet should define this protocol, and it and should
   operate over CoAP.  The protocol should be able to carry multiple
   metrics, in particular the same metrics as used for RPL operations
   [RFC6551]  6TiSCH IP Interface

   "6top" ([]) is a logical link control
   sitting between the IP layer and the TSCH MAC layer which provides
   the link abstraction that is required for IP operations.  The 6top
   data model and management interfaces are further discussed in
   [I-D.ietf-6tisch-6top-interface] and [I-D.ietf-6tisch-coap].

   An IP packet that is sent along a 6TiSCH path uses the Differentiated
   Services Per-Hop-Behavior Group called Deterministic Forwarding, as
   described in [I-D.svshah-tsvwg-deterministic-forwarding].

5.3.3.  6TiSCH Security Considerations

   On top of 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

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5.4.  Wireless Industrial Asks

   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  Protocol for packet replication and elimination

   o  Protocol for packet automatic retries (ARQ) (specific to wireless)

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
   of establishing time-sensitive streams for both Layer-2 and Layer-3
   user plane traffic.

6.1.1.  Network Architecture

   Figure 7 illustrates a typical 3GPP-defined cellular network
   architecture, which includes "Fronthaul" and "Midhaul" network
   segments.  The "Fronthaul" is the network connecting base stations
   (baseband processing units) to the remote radio heads (antennas).
   The "Midhaul" is the network inter-connecting base stations (or small
   cell sites).

   In Figure 7 "eNB" ("E-UTRAN Node B") is the hardware that is
   connected to the mobile phone network which communicates directly
   with mobile handsets ([TS36300]).

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              Y (remote radio heads (antennas))
           Y__  \.--.                   .--.       +------+
              \_(    `.     +---+     _(Back`.     | 3GPP |
       Y------( Front  )----|eNB|----(  Haul  )----| core |
             ( `  .Haul )   +---+   ( `  .  )  )   | netw |
             /`--(___.-'      \      `--(___.-'    +------+
          Y_/     /            \.--.       \
               Y_/            _( Mid`.      \
                             (   Haul )      \
                            ( `  .  )  )      \
                             `--(___.-'\_____+---+    (small cell sites)
                                   \         |SCe|__Y
                                  +---+      +---+
                                Y_/   \_Y ("local" radios)

        Figure 7: Generic 3GPP-based Cellular Network Architecture

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, processing of a radio frame is allocated 3ms but typically the
   processing uses most of it, allowing only a small fraction to be used
   by the Fronthaul network (e.g. up to 250us one-way delay, though the
   existing spec ([NGMN-fronth]) supports delay only up to 100us).  This
   ultimately determines the distance the remote radio heads can be
   located from the base stations (e.g., 100us equals roughly 20 km of
   optical fiber-based transport).  Allocation options of the available
   time budget between processing and transport are under heavy
   discussions in the mobile industry.

   For packet-based transport the allocated transport time (e.g.  CPRI
   would allow for 100us delay [CPRI]) is consumed by all nodes and
   buffering between the remote radio head and the baseband processing
   unit, plus the distance-incurred delay.

   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].

   [METIS] documents the fundamental challenges as well as overall
   technical goals of the future 5G mobile and wireless system as the
   starting point.  These future systems should support much higher data

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   volumes and rates and significantly lower end-to-end latency for 100x
   more connected devices (at similar cost and energy consumption levels
   as today's system).

   For Midhaul connections, delay constraints are driven by Inter-Site
   radio functions like Coordinated Multipoint Processing (CoMP, see
   [CoMP]).  CoMP reception and transmission is a framework in which
   multiple geographically distributed antenna nodes cooperate to
   improve the performance of the users served in the common cooperation
   area.  The design principal of CoMP is to extend the current single-
   cell to multi-UE (User Equipment) transmission to a multi-cell-to-
   multi-UEs transmission by base station cooperation.

   CoMP has delay-sensitive performance parameters, which are "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 1-10ms.  This delay requirement is both rigid
   and absolute because any uncertainty in delay will degrade the
   performance significantly.

   Inter-site CoMP is one of the key requirements for 5G and is also a
   near-term goal for the current 4.5G network architecture.

6.1.3.  Time Synchronization Constraints

   Fronthaul time synchronization requirements are given by [TS25104],
   [TS36104], [TS36211], and [TS36133].  These can be summarized for the
   current 3GPP LTE-based networks as:

   Delay Accuracy:
      +-8ns (i.e. +-1/32 Tc, where Tc is the UMTS Chip time of 1/3.84
      MHz) resulting in a round trip accuracy of +-16ns.  The value is
      this low to meet the 3GPP Timing Alignment Error (TAE) measurement

   Timing Alignment Error:
      Timing Alignment Error (TAE) is problematic to Fronthaul networks
      and must be minimized.  If the transport network cannot guarantee
      low enough TAE 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
      for packet based Fronthaul networks.

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      *  For multiple input multiple output (MIMO) or TX diversity
         transmissions, at each carrier frequency, TAE shall not exceed
         65 ns (i.e. 1/4 Tc).

      *  For intra-band contiguous carrier aggregation, with or without
         MIMO or TX diversity, TAE shall not exceed 130 ns (i.e. 1/2

      *  For intra-band non-contiguous carrier aggregation, with or
         without MIMO or TX diversity, TAE shall not exceed 260 ns (i.e.
         one Tc).

      *  For inter-band carrier aggregation, with or without MIMO or TX
         diversity, TAE shall not exceed 260 ns.

   Transport link contribution to radio frequency error:
      +-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: the reason that the transport link
      contributes to radio frequency error is as follows.  The current
      way of doing Fronthaul is from the radio unit to remote radio head
      directly.  The remote radio head is essentially a passive device
      (without buffering etc.)  The transport drives the antenna
      directly by feeding it with samples and everything the transport
      adds will be introduced to radio as-is.  So if the transport
      causes additional frequency error that shows immediately on the
      radio as well.

   The above listed time synchronization requirements are difficult to
   meet with point-to-point connected networks, and more difficult 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 in
   every intermediate node.

   In cellular networks from the LTE radio era onward, phase
   synchronization is needed in addition to frequency synchronization
   ([TS36300], [TS23401]).

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6.1.4.  Transport Loss Constraints

   Fronthaul and Midhaul networks assume almost error-free transport.
   Errors can result in a reset of the radio interfaces, which can cause
   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.  Current
   tools for elminating packet loss for Fronthaul and Midhaul networks
   have serious challenges, for example retransmitting lost packets and/
   or using forward error correction (FEC) to circumvent bit errors is
   practically impossible due to the additional delay incurred.  Using
   redundant streams for better guarantees for delivery is also
   practically impossible in many cases due to high bandwidth
   requirements of Fronthaul and Midhaul networks.  Protection switching
   is also a candidate but current technologies for the path switch are
   too slow to avoid reset of mobile interfaces.

   Fronthaul links are assumed to be symmetric, and all Fronthaul
   streams (i.e.  those carrying radio data) have equal priority and
   cannot delay or pre-empt each other.  This implies that the network
   must guarantee that each time-sensitive flow meets their schedule.

6.1.5.  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.

6.2.  Cellular Radio Networks Today

6.2.1.  Fronthaul

   Today's Fronthaul networks typically consist of:

   o  Dedicated point-to-point fiber connection is common

   o  Proprietary protocols and framings

   o  Custom equipment and no real networking

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   Current 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 sync using 1588 and SyncE

   Telecommunication networks in the Mid- and Backhaul are already
   heading towards transport networks where precise time synchronization
   support is one of the basic building blocks.  While the transport
   networks themselves have practically transitioned to all-IP packet-
   based networks to meet the bandwidth and cost requirements, highly
   accurate clock distribution has become a challenge.

   In the past, Mid- and Backhaul connections were typically based on
   Time Division Multiplexing (TDM-based) and provided frequency
   synchronization capabilities as a part of the transport media.
   Alternatively other technologies such as Global Positioning System
   (GPS) or Synchronous Ethernet (SyncE) are used [SyncE].

   Both Ethernet and IP/MPLS [RFC3031] (and PseudoWires (PWE) [RFC3985]
   for legacy transport support) have become popular tools to build and
   manage new all-IP Radio Access Networks (RANs)
   [].  Although various timing and
   synchronization optimizations have already been proposed and
   implemented including 1588 PTP enhancements
   [I-D.ietf-tictoc-1588overmpls] and [I-D.ietf-mpls-residence-time],
   these solution are not necessarily sufficient for the forthcoming RAN
   architectures nor do they guarantee the more stringent time-
   synchronization requirements such as [CPRI].

   There are also existing solutions for TDM over IP such as [RFC5087]
   and [RFC4553], as well as TDM over Ethernet transports such as

6.3.  Cellular Radio Networks Future

   Future Cellular Radio Networks will be based on a mix of different
   xHaul networks (xHaul = front-, mid- 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

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      solutions must address all traffic types (Layer 2, Layer 3) with
      the same tools and allow their transport simultaneously.

   o  All form of xHaul networks will need some form of DetNet
      solutions.  For example with the advent of 5G some Backhaul
      traffic will also have DetNet requirements (e.g. traffic belonging
      to time-critical 5G applications).

   We would like to see the following in future Cellular Radio networks:

   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 radio access network deployment models and architectures may
   require time- sensitive networking 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 [MEF] and are
   becoming a real issue for Fronthaul networks also.  Specifically in
   Fronthaul networks the timing and synchronization requirements can be
   extreme for packet based technologies, for example, on the order of
   sub +-20 ns packet delay variation (PDV) and frequency accuracy of
   +0.002 PPM [Fronthaul].

   The actual transport protocols and/or solutions to establish required
   transport "circuits" (pinned-down paths) for Fronthaul traffic are
   still undefined.  Those are likely to include (but are not limited
   to) solutions directly over Ethernet, over IP, and using MPLS/
   PseudoWire transport.

   Even the current time-sensitive networking features may not be
   sufficient for Fronthaul traffic.  Therefore, having specific
   profiles that take the requirements of Fronthaul into account is
   desirable [IEEE8021CM].

   Interesting and important work for time-sensitive networking has been
   done for Ethernet [TSNTG], which specifies the use of IEEE 1588 time
   precision protocol (PTP) [IEEE1588] in the context of IEEE 802.1D and
   IEEE 802.1Q.  [IEEE8021AS] specifies a Layer 2 time synchronizing
   service, and other specifications such as IEEE 1722 [IEEE1722]
   specify Ethernet-based Layer-2 transport for time-sensitive streams.

   New promising work seeks to enable the transport of time-sensitive
   fronthaul streams in Ethernet bridged networks [IEEE8021CM].

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   Analogous to IEEE 1722 there is an ongoing standardization effort to
   define the Layer-2 transport encapsulation format for transporting
   radio over Ethernet (RoE) in the IEEE 1904.3 Task Force [IEEE19043].

   All-IP RANs and xHhaul 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 providing Layer 3 services.  The protocol
   stack typically has a number of layers below the Ethernet Layer 2
   that shows up to the Layer 3 IP transport.  It is not uncommon that
   on top of the lowest layer (optical) transport there is the first
   layer of Ethernet followed one or more layers of MPLS, PseudoWires
   and/or other tunneling protocols finally carrying the Ethernet layer
   visible to the user plane IP traffic.

   While there are existing technologies to establish circuits through
   the routed and switched networks (especially in 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
   same solution also must address the use cases where the user plane
   traffic is a different layer, for example Ethernet frames.

   There is existing work describing the problem statement
   [I-D.finn-detnet-problem-statement] and the architecture
   [I-D.finn-detnet-architecture] for deterministic networking (DetNet)
   that targets solutions for time-sensitive (IP/transport) streams with
   deterministic properties over Ethernet-based switched networks.

6.4.  Cellular Radio Networks Asks

   A standard for data plane transport specification which is:

   o  Unified among all xHauls

   o  Deployed in a highly deterministic network environment

   A standard for data flow information models that are:

   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)

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7.  Industrial M2M

7.1.  Use Case Description

   Industrial Automation in general refers to automation of
   manufacturing, quality control and material processing.  In this
   "machine to machine" (M2M) use case we consider machine units in a
   plant floor which periodically exchange data with upstream or
   downstream machine modules and/or a supervisory controller within a
   local area network.

   The actors of M2M communication are Programmable Logic Controllers
   (PLCs).  Communication between PLCs and between PLCs and the
   supervisory PLC (S-PLC) is achieved via critical control/data streams
   Figure 8.

              S (Sensor)
               \                                  +-----+
         PLC__  \.--.                   .--.   ---| MES |
              \_(    `.               _(    `./   +-----+
       A------( Local  )-------------(  L2    )
             (      Net )           (      Net )    +-------+
             /`--(___.-'             `--(___.-' ----| S-PLC |
          S_/     /       PLC   .--. /              +-------+
               A_/           \_(    `.
            (Actuator)       (  Local )
                            (       Net )
                            /       \    A
                           S         A

       Figure 8: 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, set-up, and database
   communication) are adequately served by currently available
   prioritizing techniques.  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 the primary need for deterministic networking is to
   provide end-to-end delivery of M2M messages within specific timing
   constraints, for example in closed loop automation control.  Today

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   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 which 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.

7.2.  Industrial M2M Communication 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 pre-configured payload or a payload configured during

   Some industrial applications require time synchronization at the end
   nodes.  For such time-coordinated PLCs, accuracy of 1 microsecond is
   required.  Even in the case of "non-time-coordinated" PLCs time sync
   may be needed e.g. for timestamping of sensor data.

   Industrial network scenarios require advanced security solutions.
   Many of the current industrial production networks are physically
   separated.  Preventing critical flows from be leaked outside a domain
   is handled today by filtering policies that are typically enforced in

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 1ms
   - 100ms for critical control/data streams.

   Because industrial applications assume deterministic transport for
   critical Control-Data-Stream parameters (instead of defining latency
   and delay variation parameters) it is sufficient to fulfill the upper
   bound of latency (maximum latency).  The underlying networking
   infrastructure must ensure a maximum end-to-end delivery time of
   messages in the range of 100 microseconds to 50 milliseconds
   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

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   loop.  For PLC-to-PLC communication one can expect 2 - 32 streams
   with packet size in the range of 100 - 700 bytes.  For S-PLC to PLCs
   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 1Gbps links are commonly used.

   Most PLC control loops are rather tolerant of packet loss, however
   critical control/data streams accept no more than 1 packet loss per
   consecutive communication cycle (i.e. if a packet gets lost in cycle
   "n", then the next cycle ("n+1") must be lossless).  After two or
   more consecutive packet losses 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 we expect that some form of redundancy
   will be required for M2M communications, however any individual
   solution depends on several parameters including cycle time, delivery
   time, etc.

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.  Going forward as
   production systems become more flexible, we expect a significant
   increase in the rate at which streams are created, changed and

7.3.  Industrial M2M Future

   We would like to see 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 or,
   in the case of new installations, devices could be connected directly
   to the converged network.

7.4.  Industrial M2M Asks

   o  Converged IP-based network

   o  Deterministic behavior (bounded latency and jitter )

   o  High availability (presumably through redundancy) (99.999 %)

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   o  Low message delivery time (100us - 50ms)

   o  Low packet loss (burstless, 0.1-1 %)

   o  Precise time synchronization accuracy (1us)

   o  Security (e.g. prevent critical flows from being leaked between
      physically separated networks)

8.  Internet-based Applications

8.1.  Use Case Description

   There are many applications that communicate across the open Internet
   that could benefit from guaranteed delivery and bounded latency.  The
   following are some representative examples.

8.1.1.  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.

8.1.2.  Online Gaming

   Online gaming is a significant part of the gaming market, however
   latency can degrade the end user experience.  For example "First
   Person Shooter" (FPS) games are highly delay-sensitive.

8.1.3.  Virtual Reality

   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.

8.2.  Internet-Based Applications Today

   Internet service today is by definition "best effort", with no
   guarantees on delivery or bandwidth.

8.3.  Internet-Based Applications Future

   We imagine an Internet from which we will be able to play a video
   without glitches and play games without lag.

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   For online gaming, the maximum round-trip delay can be 100ms and
   stricter for FPS gaming which can be 10-50ms.  Transport delay is the
   dominate part with a 5-20ms budget.

   For VR, 1-10ms maximum delay is needed and total network budget is
   1-5ms if doing remote VR.

   Flow identification can be used for gaming and VR, i.e. it can
   recognize a critical flow and provide appropriate latency bounds.

8.4.  Internet-Based Applications Asks

   o  Unified control and management protocols to handle time-critical
      data flow

   o  Application-aware flow filtering mechanism to recognize the timing
      critical flow without doing 5-tuple matching

   o  Unified control plane to provide low latency service on Layer-3
      without changing the data plane

   o  OAM system and protocols which can help to provide E2E-delay
      sensitive service provisioning

9.  Use Case Common Elements

   Looking at the use cases collectively, the following common desires
   for the DetNet-based networks of the future emerge:

   o  Open standards-based network (replace various proprietary
      networks, reduce cost, create multi-vendor market)

   o  Centrally administered (though such administration may be
      distributed for scale and resiliency)

   o  Integrates L2 (bridged) and L3 (routed) environments (independent
      of the Link layer, e.g. can be used with Ethernet, 6TiSCH, etc.)

   o  Carries both deterministic and best-effort traffic (guaranteed
      end-to-end delivery of deterministic flows, deterministic flows
      isolated from each other and from best-effort traffic congestion,
      unused deterministic BW available to best-effort traffic)

   o  Ability to add or remove systems from the network with minimal,
      bounded service interruption (applications include replacement of
      failed devices as well as plug and play)

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   o  Uses standardized data flow information models capable of
      expressing deterministic properties (models express device
      capabilities, flow properties.  Protocols for pushing models from
      controller to devices, devices to controller)

   o  Scalable size (long distances (many km) and short distances
      (within a single machine), many hops (radio repeaters, microwave
      links, fiber links...) and short hops (single machine))

   o  Scalable timing parameters and accuracy (bounded latency,
      guaranteed worst case maximum, minimum.  Low latency, e.g. control
      loops may be less than 1ms, but larger for wide area networks)

   o  High availability (99.9999 percent up time requested, but may be
      up to twelve 9s)

   o  Reliability, redundancy (lives at stake)

   o  Security (from failures, attackers, misbehaving devices -
      sensitive to both packet content and arrival time)

10.  Acknowledgments

10.1.  Pro Audio

   This section was derived from draft-gunther-detnet-proaudio-req-01.

   The editors 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

10.2.  Utility Telecom

   This section was derived from draft-wetterwald-detnet-utilities-reqs-

   Faramarz Maghsoodlou, Ph.  D.  IoT Connected Industries and Energy
   Practice Cisco

   Pascal Thubert, CTAO Cisco

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10.3.  Building Automation Systems

   This section was derived from draft-bas-usecase-detnet-00.

10.4.  Wireless for Industrial

   This section was derived from draft-thubert-6tisch-4detnet-01.

   This specification 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.

   The authors wish 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.

10.5.  Cellular Radio

   This section was derived from draft-korhonen-detnet-telreq-00.

10.6.  Industrial M2M

   The authors would like to thank Feng Chen and Marcel Kiessling for
   their comments and suggestions.

10.7.  Internet Applications and CoMP

   This section was derived from draft-zha-detnet-use-case-00.

   This document has benefited from reviews, suggestions, comments and
   proposed text provided by the following members, listed in
   alphabetical order: Jing Huang, Junru Lin, Lehong Niu and Oilver

11.  Informative References

   [ACE]      IETF, "Authentication and Authorization for Constrained
              Environments", <

              ASHRAE, "Annex J to ANSI/ASHRAE 135-1995 - BACnet/IP",
              January 1999.

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   [CCAMP]    IETF, "Common Control and Measurement Plane",

              ENHANCEMENT", NGMN Alliance NGMN_RANEV_D3_CoMP_Evaluation_
              and_Enhancement_v2.0, March 2015,

              Olsen, D., "1722a Content Protection", 2012,

   [CPRI]     CPRI Cooperation, "Common Public Radio Interface (CPRI);
              Interface Specification", CPRI Specification V6.1, July
              2014, <

              CPRI TWG, "CPRI requirements for Ethernet Fronthaul",
              November 2015,

   [DCI]      Digital Cinema Initiatives, LLC, "DCI Specification,
              Version 1.2", 2012, <>.

   [DICE]     IETF, "DTLS In Constrained Environments",

   [EA12]     Evans, P. and M. Annunziata, "Industrial Internet: Pushing
              the Boundaries of Minds and Machines", November 2012.

              Daley, D., "ESPN's DC2 Scales AVB Large", 2014,

   [flnet]    Japan Electrical Manufacturers' Association, "JEMA 1479 -
              English Edition", September 2012.

              Chen, D. and T. Mustala, "Ethernet Fronthaul
              Considerations", IEEE 1904.3, February 2015,
              tf3_1502_che n_1a.pdf>.

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   [HART], "Highway Addressable remote Transducer,
              a group of specifications for industrial process and
              control devices administered by the HART Foundation".

              Finn, N., Thubert, P., and M. Teener, "Deterministic
              Networking Architecture", draft-finn-detnet-
              architecture-03 (work in progress), March 2016.

              Finn, N. and P. Thubert, "Deterministic Networking Problem
              Statement", draft-finn-detnet-problem-statement-04 (work
              in progress), October 2015.

              Wang, Q. and X. Vilajosana, "6TiSCH Operation Sublayer
              (6top) Interface", draft-ietf-6tisch-6top-interface-04
              (work in progress), July 2015.

              Thubert, P., "An Architecture for IPv6 over the TSCH mode
              of IEEE 802.15.4", draft-ietf-6tisch-architecture-09 (work
              in progress), November 2015.

              Sudhaakar, R. and P. Zand, "6TiSCH Resource Management and
              Interaction using CoAP", draft-ietf-6tisch-coap-03 (work
              in progress), March 2015.

              Palattella, M., Thubert, P., Watteyne, T., and Q. Wang,
              "Terminology in IPv6 over the TSCH mode of IEEE
              802.15.4e", draft-ietf-6tisch-terminology-06 (work in
              progress), November 2015.

              Thaler, D. and C. Huitema, "Multi-link Subnet Support in
              IPv6", draft-ietf-ipv6-multilink-subnets-00 (work in
              progress), July 2002.

              Mirsky, G., Ruffini, S., Gray, E., Drake, J., Bryant, S.,
              and S. Sasha, "Residence Time Measurement in MPLS
              network", draft-ietf-mpls-residence-time-06 (work in
              progress), March 2016.

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              Phinney, T., Thubert, P., and R. Assimiti, "RPL
              applicability in industrial networks", draft-ietf-roll-
              rpl-industrial-applicability-02 (work in progress),
              October 2013.

              Davari, S., Oren, A., Bhatia, M., Roberts, P., and L.
              Montini, "Transporting Timing messages over MPLS
              Networks", draft-ietf-tictoc-1588overmpls-07 (work in
              progress), October 2015.

              Khasnabish, B., hu, f., and L. Contreras, "Segment Routing
              in IP RAN use case", draft-kh-spring-ip-ran-use-case-02
              (work in progress), November 2014.

              Shah, S. and P. Thubert, "Deterministic Forwarding PHB",
              draft-svshah-tsvwg-deterministic-forwarding-04 (work in
              progress), August 2015.

              Thubert, P., "6LoWPAN Backbone Router", draft-thubert-
              6lowpan-backbone-router-03 (work in progress), February

              Wang, Q. and X. Vilajosana, "6TiSCH Operation Sublayer
              (6top)", draft-wang-6tisch-6top-sublayer-04 (work in
              progress), November 2015.

              TC57 WG10, IEC., "IEC 61850-90-12 TR: Communication
              networks and systems for power utility automation - Part
              90-12: Wide area network engineering guidelines", 2015.

              TC65, IEC., "IEC 62439-3: Industrial communication
              networks - High availability automation networks - Part 3:
              Parallel Redundancy Protocol (PRP) and High-availability
              Seamless Redundancy (HSR)", 2012.

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              IEEE, "IEEE Standard for a Precision Clock Synchronization
              Protocol for Networked Measurement and Control Systems",
              IEEE Std 1588-2008, 2008,

              IEEE, "1722-2011 - IEEE Standard for Layer 2 Transport
              Protocol for Time Sensitive Applications in a Bridged
              Local Area Network", IEEE Std 1722-2011, 2011,

              IEEE Standards Association, "IEEE 1904.3 TF", IEEE 1904.3,
              2015, <>.

              IEEE Standards Association, "IEEE 802.1 Time-Sensitive
              Networks Task Group", March 2013,

              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".

              IEEE standard for Information Technology, "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, June 2011 as amended by IEEE std.
              802.15.4e, Part. 15.4: Low-Rate Wireless Personal Area
              Networks (LR-WPANs) Amendment 1: MAC sublayer", April

              IEEE, "Timing and Synchronizations (IEEE 802.1AS-2011)",
              IEEE 802.1AS-2001, 2011,

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              Farkas, J., "Time-Sensitive Networking for Fronthaul",
              Unapproved PAR, PAR for a New IEEE Standard;
              IEEE P802.1CM, April 2015,
              new-P802-1CM-dr aft-PAR-0515-v02.pdf>.

              IEEE 802.1, "The charter of the TG is to provide the
              specifications that will allow time-synchronized low
              latency streaming services through 802 networks.", 2016,

              IETF, "Charter for IETF DetNet Working Group", 2015,

   [ISA100]   ISA/ANSI, "ISA100, Wireless Systems for Automation",

              ISA/ANSI, "Wireless Systems for Industrial Automation:
              Process Control and Related Applications - ISA100.11a-2011
              - IEC 62734", 2011, <

              ISO, "ISO 7240-16:2007 Fire detection and alarm systems --
              Part 16: Sound system control and indicating equipment",
              2007, <

   [knx]      KNX Association, "ISO/IEC 14543-3 - KNX", November 2006.

   [lontalk]  ECHELON, "LonTalk(R) Protocol Specification Version 3.0",

              Johnston, S., "LTE Latency: How does it compare to other
              technologies", March 2014,

   [MEF]      MEF, "Mobile Backhaul Phase 2 Amendment 1 -- Small Cells",
              MEF 22.1.1, July 2014,

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   [METIS]    METIS, "Scenarios, requirements and KPIs for 5G mobile and
              wireless system", ICT-317669-METIS/D1.1 ICT-
              317669-METIS/D1.1, April 2013, <

   [modbus]   Modbus Organization, "MODBUS APPLICATION PROTOCOL
              SPECIFICATION V1.1b", December 2006.

   [net5G]    Ericsson, "5G Radio Access, Challenges for 2020 and
              Beyond", Ericsson white paper wp-5g, June 2013,

   [NGMN]     NGMN Alliance, "5G White Paper", NGMN 5G White Paper v1.0,
              February 2015, <

              NGMN Alliance, "Fronthaul Requirements for C-RAN", March
              2015, <

   [PCE]      IETF, "Path Computation Element",

              IEC, "IEC 61158 Type 3 - Profibus DP", January 2001.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
              December 1998, <>.

   [RFC2474]  Nichols, K., Blake, S., Baker, F., and D. Black,
              "Definition of the Differentiated Services Field (DS
              Field) in the IPv4 and IPv6 Headers", RFC 2474,
              DOI 10.17487/RFC2474, December 1998,

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031,
              DOI 10.17487/RFC3031, January 2001,

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   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,

   [RFC3393]  Demichelis, C. and P. Chimento, "IP Packet Delay Variation
              Metric for IP Performance Metrics (IPPM)", RFC 3393,
              DOI 10.17487/RFC3393, November 2002,

   [RFC3444]  Pras, A. and J. Schoenwaelder, "On the Difference between
              Information Models and Data Models", RFC 3444,
              DOI 10.17487/RFC3444, January 2003,

   [RFC3972]  Aura, T., "Cryptographically Generated Addresses (CGA)",
              RFC 3972, DOI 10.17487/RFC3972, March 2005,

   [RFC3985]  Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
              Edge-to-Edge (PWE3) Architecture", RFC 3985,
              DOI 10.17487/RFC3985, March 2005,

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, DOI 10.17487/RFC4291, February
              2006, <>.

   [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,

   [RFC4903]  Thaler, D., "Multi-Link Subnet Issues", RFC 4903,
              DOI 10.17487/RFC4903, June 2007,

   [RFC4919]  Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6
              over Low-Power Wireless Personal Area Networks (6LoWPANs):
              Overview, Assumptions, Problem Statement, and Goals",
              RFC 4919, DOI 10.17487/RFC4919, August 2007,

   [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,

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   [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,

   [RFC6282]  Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
              Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
              DOI 10.17487/RFC6282, September 2011,

   [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,

   [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,

   [RFC6775]  Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
              Bormann, "Neighbor Discovery Optimization for IPv6 over
              Low-Power Wireless Personal Area Networks (6LoWPANs)",
              RFC 6775, DOI 10.17487/RFC6775, November 2012,

   [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,

              Gunther, C., "Specifying SRP Latency", 2014,

              Mace, G., "IP Networked Studio Infrastructure for
              Synchronized & Real-Time Multimedia Transmissions", 2007,

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   [SyncE]    ITU-T, "G.8261 : Timing and synchronization aspects in
              packet networks", Recommendation G.8261, August 2013,

   [TEAS]     IETF, "Traffic Engineering Architecture and Signaling",

   [TS23401]  3GPP, "General Packet Radio Service (GPRS) enhancements
              for Evolved Universal Terrestrial Radio Access Network
              (E-UTRAN) access", 3GPP TS 23.401 10.10.0, March 2013.

   [TS25104]  3GPP, "Base Station (BS) radio transmission and reception
              (FDD)", 3GPP TS 25.104 3.14.0, March 2007.

   [TS36104]  3GPP, "Evolved Universal Terrestrial Radio Access
              (E-UTRA); Base Station (BS) radio transmission and
              reception", 3GPP TS 36.104 10.11.0, July 2013.

   [TS36133]  3GPP, "Evolved Universal Terrestrial Radio Access
              (E-UTRA); Requirements for support of radio resource
              management", 3GPP TS 36.133 12.7.0, April 2015.

   [TS36211]  3GPP, "Evolved Universal Terrestrial Radio Access
              (E-UTRA); Physical channels and modulation", 3GPP
              TS 36.211 10.7.0, March 2013.

   [TS36300]  3GPP, "Evolved Universal Terrestrial Radio Access (E-UTRA)
              and Evolved Universal Terrestrial Radio Access Network
              (E-UTRAN); Overall description; Stage 2", 3GPP TS 36.300
              10.11.0, September 2013.

   [TSNTG]    IEEE Standards Association, "IEEE 802.1 Time-Sensitive
              Networks Task Group", 2013,

              Holub, P., "Ultra-High Definition Videos and Their
              Applications over the Network", The 7th International
              Symposium on VICTORIES Project PetrHolub_presentation,
              October 2014, <http://www.aist-

    , "Industrial Communication Networks -
              Wireless Communication Network and Communication Profiles
              - WirelessHART - IEC 62591", 2010.

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Authors' Addresses

   Ethan Grossman (editor)
   Dolby Laboratories, Inc.
   1275 Market Street
   San Francisco, CA  94103

   Phone: +1 415 645 4726

   Craig Gunther
   Harman International
   10653 South River Front Parkway
   South Jordan, UT  84095

   Phone: +1 801 568-7675

   Pascal Thubert
   Cisco Systems, Inc
   Building D
   45 Allee des Ormes - BP1200
   MOUGINS - Sophia Antipolis  06254

   Phone: +33 497 23 26 34

   Patrick Wetterwald
   Cisco Systems
   45 Allees des Ormes
   Mougins  06250

   Phone: +33 4 97 23 26 36

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   Jean Raymond
   1500 University
   Montreal  H3A3S7

   Phone: +1 514 840 3000

   Jouni Korhonen
   Broadcom Corporation
   3151 Zanker Road
   San Jose, CA  95134


   Yu Kaneko
   1 Komukai-Toshiba-cho, Saiwai-ku, Kasasaki-shi
   Kanagawa, Japan


   Subir Das
   Applied Communication Sciences
   150 Mount Airy Road, Basking Ridge
   New Jersey, 07920, USA


   Yiyong Zha
   Huawei Technologies


   Balazs Varga
   Konyves Kalman krt. 11/B
   Budapest  1097


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   Janos Farkas
   Konyves Kalman krt. 11/B
   Budapest  1097


   Franz-Josef Goetz
   Gleiwitzerstr. 555
   Nurnberg  90475


   Juergen Schmitt
   Gleiwitzerstr. 555
   Nurnberg  90475


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