Internet Engineering Task Force                         E. Grossman, Ed.
Internet-Draft                                                     DOLBY
Intended status: Informational                                C. Gunther
Expires: August 12, 13, 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
                                                       February 9, 10, 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.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on August 12, 13, 2016.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Pro Audio Use Cases . . . . . . . . . . . . . . . . . . . . .   5
     2.1.  Introduction  . . . . . . . . . . . . . . . . . . . . . .   5
     2.2.  Fundamental Stream Requirements . . . . . . . . . . . . .   6
       2.2.1.  Guaranteed Bandwidth  . . . . . . . . . . . . . . . .   6
       2.2.2.  Bounded and Consistent Latency  . . . . . . . . . . .   7  Optimizations . . . . . . . . . . . . . . . . . .   8
     2.3.  Additional Stream Requirements  . . . . . . . . . . . . .   9   8
       2.3.1.  Deterministic Time to Establish Streaming . . . . . .   9
       2.3.2.  Use of Unused Reservations by Best-Effort Traffic . .   9
       2.3.3.  Layer 3 Interconnecting Layer 2 Islands . . . . . . .  10   9
       2.3.4.  Secure Transmission . . . . . . . . . . . . . . . . .  10
       2.3.5.  Redundant Paths . . . . . . . . . . . . . . . . . . .  10
       2.3.6.  Link Aggregation  . . . . . . . . . . . . . . . . . .  10
       2.3.7.  Traffic Segregation . . . . . . . . . . . . . . . . .  11  10  Packet Forwarding Rules, VLANs and Subnets  . . .  11  Multicast Addressing (IPv4 and IPv6)  . . . . . .  11
     2.4.  Integration of Reserved Streams into IT Networks  . . . .  12  11
     2.5.  Security Considerations . . . . . . . . . . . . . . . . .  12
       2.5.1.  Denial of Service . . . . . . . . . . . . . . . . . .  12
       2.5.2.  Control Protocols . . . . . . . . . . . . . . . . . .  12
     2.6.  A State-of-the-Art Broadcast Installation Hits Technology
           Limits  . . . . . . . . . . . . . . . . . . . . . . . . .  13  12
     2.7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . .  13
   3.  Utility Telecom Use Cases . . . . . . . . . . . . . . . . . .  13
     3.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .  13
     3.2.  Telecommunications Trends and General telecommunications
           Requirements  . . . . . . . . . . . . . . . . . . . . . .  15  14
       3.2.1.  General Telecommunications Requirements . . . . . . .  15  14  Migration to Packet-Switched Network  . . . . . .  16  15
       3.2.2.  Applications, Use cases and traffic patterns  . . . .  17  16  Transmission use cases  . . . . . . . . . . . . .  17  16  Distribution use case . . . . . . . . . . . . . .  26  Generation use case . . . . . . . . . . . . . . .  29
       3.2.3.  Specific Network topologies of Smart Grid
               Applications  . . . . . . . . . . . . . . . . . . . .  30
       3.2.4.  Precision Time Protocol . . . . . . . . . . . . . . .  31
     3.3.  IANA Considerations . . . . . . . . . . . . . . . . . . .  32
     3.4.  Security Considerations . . . . . . . . . . . . . . . . .  32
       3.4.1.  Current Practices and Their Limitations . . . . . . .  32
       3.4.2.  Security Trends in Utility Networks . . . . . . . . .  34
     3.5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . .  35
   4.  Building Automation Systems Use Cases . . . . . . . . . . . .  35
     4.1.  Introduction  . . . . . . . . . . . . . . . . . . . . . .  36
     4.2.  BAS Functionality . . . . . . . . . . . . . . . . . . . .  36
     4.3.  BAS Architecture  . . . . . . . . . . . . . . . . . . . .  37
     4.4.  Deployment Model  . . . . . . . . . . . . . . . . . . . .  39  38
     4.5.  Use cases and Field Network Requirements  . . . . . . . .  40
       4.5.1.  Environmental Monitoring  . . . . . . . . . . . . . .  41  40
       4.5.2.  Fire Detection  . . . . . . . . . . . . . . . . . . .  41  40
       4.5.3.  Feedback Control  . . . . . . . . . . . . . . . . . .  42  41
     4.6.  Security Considerations . . . . . . . . . . . . . . . . .  43  42
   5.  Wireless for Industrial Use Cases . . . . . . . . . . . . . .  44  43
     5.1.  Introduction  . . . . . . . . . . . . . . . . . . . . . .  44  43
     5.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .  45  44
     5.3.  6TiSCH Overview . . . . . . . . . . . . . . . . . . . . .  45  44
       5.3.1.  TSCH and 6top . . . . . . . . . . . . . . . . . . . .  48  47
       5.3.2.  SlotFrames and Priorities . . . . . . . . . . . . . .  48  47
       5.3.3.  Schedule Management by a PCE  . . . . . . . . . . . .  48  47
       5.3.4.  Track Forwarding  . . . . . . . . . . . . . . . . . .  49  48  Transport Mode  . . . . . . . . . . . . . . . . .  51  50  Tunnel Mode . . . . . . . . . . . . . . . . . . .  52  51  Tunnel Metadata . . . . . . . . . . . . . . . . .  53  52
     5.4.  Operations of Interest for DetNet and PCE . . . . . . . .  54  53
       5.4.1.  Packet Marking and Handling . . . . . . . . . . . . .  55  54  Tagging Packets for Flow Identification . . . . .  55  54  Replication, Retries and Elimination  . . . . . .  55  54  Differentiated Services Per-Hop-Behavior  . . . .  56  55
       5.4.2.  Topology and capabilities . . . . . . . . . . . . . .  56  55
     5.5.  Security Considerations . . . . . . . . . . . . . . . . .  57  56
     5.6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . .  57  56
   6.  Cellular Radio Use Cases  . . . . . . . . . . . . . . . . . .  57  56
     6.1.  Introduction and background . . . . . . . . . . . . . . .  57  56
     6.2.  Network architecture  . . . . . . . . . . . . . . . . . .  61  60
     6.3.  Time synchronization requirements . . . . . . . . . . . .  62  61
     6.4.  Time-sensitive stream requirements  . . . . . . . . . . .  63  62
     6.5.  Security considerations . . . . . . . . . . . . . . . . .  64  63
   7.  Industrial M2M  . . . . . . . . . . . . . . . . . . . . . . .  64  63
     7.1.  Introduction  . . . .  Use Case Description  . . . . . . . . . . . . . . . . . .  65  64
     7.2.  Terminology and Definitions . . . . . . . .  Industrial M2M Communication Today  . . . . . . .  65
     7.3.  Machine to Machine communication over IP networks . . . .  65
     7.4.  Machine to Machine communication requirements . . . . . .  66
       7.2.1.  Transport parameters  . Parameters  . . . . . . . . . . . . . . .  67
       7.4.2.  Flow maintenance  . . . . . . . . . . . .  65
       7.2.2.  Stream Creation and Destruction . . . . . .  67
     7.5.  Summary . . . . .  66
     7.3.  Industrial M2M Future . . . . . . . . . . . . . . . . . .  66
     7.4.  Industrial M2M Asks . .  67
     7.6.  Security Considerations . . . . . . . . . . . . . . . . .  68
     7.7.  66
     7.5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . .  68  67
   8.  Other Use Cases . . . . . . . . . . . . . . . . . . . . . . .  68  67
     8.1.  Introduction  . . . . . . . . . . . . . . . . . . . . . .  68  67
     8.2.  Critical Delay Requirements . . . . . . . . . . . . . . .  69  68
     8.3.  Coordinated multipoint processing (CoMP)  . . . . . . . .  70  69
       8.3.1.  CoMP Architecture . . . . . . . . . . . . . . . . . .  70  69
       8.3.2.  Delay Sensitivity in CoMP . . . . . . . . . . . . . .  71  70
     8.4.  Industrial Automation . . . . . . . . . . . . . . . . . .  71  70
     8.5.  Vehicle to Vehicle  . . . . . . . . . . . . . . . . . . .  71  70
     8.6.  Gaming, Media and Virtual Reality . . . . . . . . . . . .  72  71
   9.  Use Case Common Elements  . . . . . . . . . . . . . . . . . .  72  71
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  73  72
   11. Informative References  . . . . . . . . . . . . . . . . . . .  73
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  82  81

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 Use Cases

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

2.1.  Introduction

   The professional audio and video industry includes music and film
   content creation, broadcast, cinema, and live exposition as well as
   public address, media and emergency systems at large venues
   (airports, stadiums, churches, theme parks).  These industries have
   already gone through the transition of audio and video signals from
   analog to digital, however the 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 attempting to transition to packet based
   infrastructure for distributing audio and video in order to reduce
   cost, increase routing flexibility, and integrate with existing IT

   However, there are several requirements for making a network the
   primary infrastructure for audio and video which are not met by
   todays networks and these are our concern in this draft.

   The principal requirement is that pro audio and video applications
   become able to establish streams that provide guaranteed (bounded)
   bandwidth and latency from the Layer 3 (IP) interface.  Such streams
   can be created today within standards-based layer 2 islands however
   these are not sufficient to enable effective distribution over wider
   areas (for example broadcast events that span wide geographical

   Some proprietary systems have been created which enable deterministic
   streams at layer 3 however they are engineered networks in that they
   require careful configuration to operate, often require that the
   system be over designed, 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.

   It would be highly desirable if such streams could be routed over the
   open Internet, however even intermediate solutions with more limited
   scope (such as enterprise networks) can provide a substantial
   improvement over todays networks, and a solution that only provides
   for the enterprise network scenario is an acceptable first step.

   We also present more fine grained requirements of the audio and video
   industries such as safety and security, redundant paths, devices with
   limited computing resources on the network, and that reserved stream
   bandwidth is available for use by other best-effort traffic when that
   stream is not currently in use.

2.2.  Fundamental Stream Requirements

   The fundamental stream properties are guaranteed bandwidth and
   deterministic latency as described in this section.  Additional
   stream requirements are described in a subsequent section.

2.2.1.  Guaranteed Bandwidth

   Transmitting audio and video streams is unlike common file transfer
   activities because guaranteed delivery 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 and
   stream playback is interrupted, which is unacceptable in for example
   a live concert.  In some contexts large amounts of buffering can be
   used to provide enough delay to allow time for one or more retries,
   however this is not an effective solution when live interaction is
   involved, and is not considered an acceptable general solution for
   pro audio and video.  (Have you ever tried speaking into a microphone
   through a sound system that has an echo coming back at you?  It makes
   it almost impossible to speak clearly).

   Providing a way to reserve a specific amount of bandwidth for a given
   stream is a key requirement.

2.2.2.  Bounded and Consistent Latency

   Latency in this context means the amount of time that passes between
   when a signal is sent over a stream and when it is received, for
   example the amount of time delay between when you speak into a
   microphone and when your voice emerges from the speaker.  Any delay
   longer than about 10-15 milliseconds is noticeable by most live
   performers, and greater latency makes the system unusable because it
   prevents them from playing in time with the other players (see slide
   6 of [SRP_LATENCY]).

   The 15ms latency bound is made even more challenging because it is
   often the case in network based music production with live electric
   instruments that multiple stages of signal processing are used,
   connected in series (i.e.  from one to the other for example from
   guitar through a series of digital effects processors) in which case
   the latencies add, so the latencies of each individual stage must all
   together remain less than 15ms.

   In some situations it is acceptable at the local location for content
   from the live remote site to be delayed to allow for a statistically
   acceptable amount of latency in order to reduce jitter.  However,
   once the content begins playing in the local location any audio
   artifacts caused by the local network are unacceptable, especially in
   those situations where a live local performer is mixed into the feed
   from the remote location.

   In addition to being bounded to within some predictable and
   acceptable amount of time (which may be 15 milliseconds or more or
   less depending on the application) the latency also has to be
   consistent.  For example when playing a film consisting of a video
   stream and audio stream over a network, those two streams must be
   synchronized so that the voice and the picture match up.  A 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) buffer (delay) 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
   delays.  Optimizations

   The 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].

   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.

2.3.  Additional Stream Requirements

   The requirements in this section are more specific yet are common to
   multiple audio and video industry applications.

2.3.1.  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.
   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 to another.  Such systems
   currently use purpose-built hardware to switch feeds smoothly,
   however there is a current initiative in the broadcast industry to
   switch to a packet-based infrastructure (see [STUDIO_IP] and the ESPN
   DC2 use case described below).

2.3.2.  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 just reserve a ton of bandwidth and then never un-reserve
   it even though they are not using it, and soon they will have no
   bandwidth left.

2.3.3.  Layer 3 Interconnecting Layer 2 Islands

   As an intermediate step (short of providing guaranteed bandwidth
   across the open internet) it would be valuable to provide a way to
   connect multiple Layer 2 networks.  For example layer 2 techniques
   could be used to create a LAN for a single broadcast studio, and
   several such studios could be interconnected via layer 3 links.

2.3.4.  Secure Transmission

   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.

2.3.5.  Redundant Paths

   On-air and other live media streams must be 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

2.3.6.  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
   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 (see Bounded
   and Consistent Latency section above).

2.3.7.  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.

   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.

2.4.  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.

2.5.  Security Considerations

   Many industries that are moving from the point-to-point world to the
   digital network world have little understanding of the pitfalls that
   they can create for themselves with improperly implemented network
   infrastructure.  DetNet should consider ways to provide security
   against DoS attacks in solutions directed at these markets.  Some
   considerations are given here as examples of ways that we can help
   new users avoid common pitfalls.

2.5.1.  Denial of Service

   One security pitfall that this author is aware of involves the use of
   technology that allows a presenter to throw the content from their
   tablet or smart phone onto the A/V system that is then viewed by all
   those in attendance.  The facility introducing this technology was
   quite excited to allow such modern flexibility to those who came to
   speak.  One thing they hadn't realized was that since no security was
   put in place around this technology it left a hole in the system that
   allowed other attendees to "throw" their own content onto the A/V

2.5.2.  Control Protocols

   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).
   In addition, it would be desirable if the configuration protocols
   that are used to create the network paths used by the professional
   audio traffic could be designed to protect devices that are not meant
   to receive high-amplitude content from having such potentially
   damaging signals routed to them.

2.6.  A State-of-the-Art Broadcast Installation Hits Technology Limits

   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 details at [ESPN_DC2] ).

   In designing DC2 they replaced as much point-to-point technology as
   they possibly 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, and
   they were very happy with the results, however to interconnect these
   layer 2 LAN islands together they ended up using dedicated links
   because there is no standards-based routing solution available.

   This is the kind of motivation we have to develop these standards
   because customers are ready and able to use them.

2.7.  Acknowledgements

   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

3.  Utility Telecom Use Cases

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

3.1.  Overview

   [I-D.finn-detnet-problem-statement] defines the characteristics of a
   deterministic flow as a data communication flow with a bounded
   latency, extraordinarily low frame loss, and a very narrow jitter.
   This document intends to define the utility requirements for
   deterministic networking.

   Utility Telecom Networks

   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.

   Many utilities still rely on complex environments formed of multiple
   application-specific, proprietary networks.  Information is siloed
   between operational areas.  This prevents utility operations from
   realizing the operational efficiency benefits, visibility, and
   functional integration of operational information across grid
   applications and data networks.  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.

   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.  IPv6 is seen as the obvious future
   telecommunications technology for the Smart Grid.  The Adhoc Group
   has disclosed, to the IEC coordination group, their conclusions at
   the end of 2014.

   It is imperative that utilities participate in standards development
   bodies to influence the development of future solutions and to
   benefit from shared experiences of other utilities and vendors.

3.2.  Telecommunications Trends and General telecommunications

   These general telecommunications requirements are over and above the
   specific requirements of the use cases that have been addressed so
   far.  These include both current and future telecommunications
   related requirements that should be factored into the network
   architecture and design.

3.2.1.  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

   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  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
   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.

3.2.2.  Applications, Use cases and traffic patterns

   Among the numerous applications and use cases that a utility deploys
   today, many rely on high availability and deterministic behaviour of
   the telecommunications networks.  Protection use cases and generation
   control are the most demanding and can't rely on a best effort
   approach.  Transmission use cases

   Protection means not only the protection of the human operator but
   also the protection of the electric equipments and the preservation
   of the stability and frequency of the grid.  If a default occurs on
   the transmission or the distribution of the electricity, important
   damages could occured to the human operator but also to very costly
   electrical equipments and perturb the grid leading to blackouts.  The
   time and reliability requirements are very strong to avoid dramatic
   impacts to the electrical infrastructure.  Tele Protection

   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 key elements that may impact Teleprotection performance
   include bandwidth rate of the Teleprotection system and its
   resiliency or failure recovery capacity.  Transmission time,
   bandwidth utilization and resiliency are directly linked to the
   telecommunications equipments and the connections that are used to
   transfer the commands between relays.  Latency Budget Consideration

   Delay requirements for utility networks may vary depending upon a
   number of parameters, such as the specific protection equipments
   used.  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.  Asymetric delay

   In addition to minimal transmission delay, a differential protection
   telecommunications channel must be synchronous, i.e., experiencing
   symmetrical channel delay in transmit and receive paths.  This
   requires special attention in jitter-prone packet networks.  While
   optimally Teleprotection systems should support zero asymmetric
   delay, typical legacy relays can tolerate discrepancies of up to

   The main tools available for lowering delay variation below this
   threshold are:

   o  A jitter buffer 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.  This is the
      old TDM traditional way to fulfill this requirement.

   o  Traffic management tools ensure that the Teleprotection signals
      receive the highest transmission priority and minimize the number
      of jitter addition during the path.  This is one way to meet the
      requirement in IP networks.

   o  Standard Packet-Based synchronization technologies, such as
      1588-2008 Precision Time Protocol (PTP) and Synchronous Ethernet
      (Sync-E), can help maintain stable networks by keeping a highly
      accurate clock source on the different network devices involved.  Other traffic characteristics

   o  Redundancy: The existence in a system of more than one means of
      accomplishing a given function.

   o  Recovery time : The duration of time within which a business
      process must be restored after any type of disruption in order to
      avoid unacceptable consequences associated with a break in
      business continuity.

   o  performance management : In networking, a management function
      defined for controlling and analyzing different parameters/metrics
      such as the throughput, error rate.

   o  packet loss : One or more packets of data travelling across
      network fail to reach their destination.  Teleprotection network requirements

   The following table captures the main network requirements (this is
   based on 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 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.  The main use of such
   schemes is to ensure that protection at both ends of a faulted
   circuit will operate to isolate the equipment concerned.  Inter-
   tripping schemes use signaling to convey a trip command to remote
   circuit breakers to isolate circuits.

   |     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.  A main advantage
   for differential protection is that, compared to overcurrent
   protection, it allows only the faulted circuit to be de-energized in
   case of a fault.  At both end of the lines, the current is measured
   by the differential relays, and based on Kirchhoff's law, 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.  A fault in line 1 will cause overcurrent to
   be flowing in both lines, but because the current in line 2 is a
   through following current, this current is measured equal at both
   ends of the line, therefore the differential relays on line 2 will
   not trip line 2.  Line 1 will be tripped, as the relays will not
   measure the same currents at both ends of the line.  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.

   | 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 requirements  Distance Protection Scheme

   Distance (Impedance Relay) protection scheme is based on voltage and
   current measurements.  A fault on a circuit will generally create a
   sag in the voltage level.  If the ratio of voltage to current
   measured at the protection relay terminals, which equates to an
   impedance element, falls within a set threshold the circuit breaker
   will operate.  The operating characteristics of this protection are
   based on the line characteristics.  This means that when a fault
   appears on the line, the impedance setting in the relay is compared
   to the apparent impedance of the line from the relay terminals to the
   fault.  If the relay setting is determined to be below the apparent
   impedance it is determined that the fault is within the zone of
   protection.  When the transmission line length is under a minimum
   length, distance protection becomes more difficult to coordinate.  In
   these instances the best choice of protection is current differential

   |      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  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 merging unit 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 merging unit (MU).  The CT/VT in the
   substation send the sampled value (analog voltage or current) to the
   Merging Unit (MU) over hard wire.  The merging unit 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 MU through serial port, or IEEE 1588 protocol via
   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

   |   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.  You will find herafter the table
   summarizing these requirements:

   |      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  Distribution use case  Fault Location Isolation and Service Restoration (FLISR)

   As the name implies, 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.  It is a self-healing feature whose purpose is to minimize
   the impact of faults by serving portions of the loads on the affected
   circuit by switching to other circuits.  It reduces the number of
   customers that experience a sustained power outage by reconfiguring
   distribution circuits.  This will likely be the first wide spread
   application of distributed intelligence in the grid.  Secondary
   substations can be connected to multiple primary substations.
   Normally, static power switch statuses (open/closed) in the network
   dictate the power flow to secondary substations.  Reconfiguring the
   network in the event of a fault is typically done manually on site to
   operate switchgear to energize/de-energize alternate paths.
   Automating the operation of substation switchgear allows the utility
   to have a more dynamic network where the flow of power can be altered
   under fault conditions but also during times of peak load.  It allows
   the utility to shift peak loads around the network.  Or, to be more
   precise, alters the configuration of the network to move loads
   between different primary substations.  The FLISR capability can be
   enabled in two modes:

   o  Managed centrally from DMS (Distribution Management System), or

   o  Executed locally through distributed control via intelligent
      switches and fault sensors.

   There are 3 distinct sub-functions that are performed:

   1.  Fault Location Identification

   This sub-function is initiated by SCADA inputs, such as lockouts,
   fault indications/location, and, also, by input from the Outage
   Management System (OMS), and in the future by inputs from fault-
   predicting devices.  It determines the specific protective device,
   which has cleared the sustained fault, identifies the de-energized
   sections, and estimates the probable location of the actual or the
   expected fault.  It distinguishes faults cleared by controllable
   protective devices from those cleared by fuses, and identifies
   momentary outages and inrush/cold load pick-up currents.  This step
   is also referred to as Fault Detection Classification and Location
   (FDCL).  This step helps to expedite the restoration of faulted
   sections through fast fault location identification and improved
   diagnostic information available for crew dispatch.  Also provides
   visualization of fault information to design and implement a
   switching plan to isolate the fault.

   2.  Fault Type Determination

   I.  Indicates faults cleared by controllable protective devices by
   distinguishing between:

   a.  Faults cleared by fuses

   b.  Momentary outages

   c.  Inrush/cold load current

   II.  Determines the faulted sections based on SCADA fault indications
   and protection lockout signals

   III.  Increases the accuracy of the fault location estimation based
   on SCADA fault current measurements and real-time fault analysis

   3.  Fault Isolation and Service Restoration
   Once the location and type of the fault has been pinpointed, the
   systems will attempt to isolate the fault and restore the non-faulted
   section of the network.  This can have three modes of operation:

   I.  Closed-loop mode : This is initiated by the Fault location sub-
   function.  It generates a switching order (i.e., sequence of
   switching) for the remotely controlled switching devices to isolate
   the faulted section, and restore service to the non-faulted sections.
   The switching order is automatically executed via SCADA.

   II.  Advisory mode : This is initiated by the Fault location sub-
   function.  It generates a switching order for remotely and manually
   controlled switching devices to isolate the faulted section, and
   restore service to the non-faulted sections.  The switching order is
   presented to operator for approval and execution.

   III.  Study mode : the operator initiates this function.  It analyzes
   a saved case modified by the operator, and generates a switching
   order under the operating conditions specified by the operator.

   With the increasing volume of data that are collected through fault
   sensors, utilities will use Big Data query and analysis tools to
   study outage information to anticipate and prevent outages by
   detecting failure patterns and their correlation with asset age,
   type, load profiles, time of day, weather conditions, and other
   conditions to discover conditions that lead to faults and take the
   necessary preventive and corrective measures.

   |  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 9: FLISR Communication Requirements  Generation use case  Frequency Control / Automatic Generation Control (AGC)

   The system frequency should be maintained within a very narrow band.
   Deviations from the acceptable frequency range are detected and
   forwarded to the Load Frequency Control (LFC) system so that required
   up or down generation increase / decrease pulses can be sent to the
   power plants for frequency regulation.  The trend in system frequency
   is a measure of mismatch between demand and generation, and is a
   necessary parameter for load control in interconnected systems.

   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.  Since a power grid requires that generation and
   load closely balance moment by moment, frequent adjustments to the
   output of generators are necessary.  The balance can be judged by
   measuring the system frequency; if it is increasing, more power is
   being generated than used, and all machines in the system are
   accelerating.  If the system frequency is decreasing, more demand is
   on the system than the instantaneous generation can provide, and all
   generators are slowing down.

   Where the grid has tie lines to adjacent control areas, automatic
   generation control helps maintain the power interchanges over the tie
   lines at the scheduled levels.  The AGC takes into account various
   parameters including the most economical units to adjust, the
   coordination of thermal, hydroelectric, and other generation types,
   and even constraints related to the stability of the system and
   capacity of interconnections to other power grids.

   For the purpose of AGC we use static frequency measurements and
   averaging methods are used to get a more precise measure of system
   frequency in steady-state conditions.

   During disturbances, more real-time dynamic measurements of system
   frequency are taken using PMUs, especially when different areas of
   the system exhibit different frequencies.  But that is outside the
   scope of this use case.

   |   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 10: FCAG Communication Requirements

3.2.3.  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

   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
   SPS 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

   Due to vast distances between transmission substations (for example
   as far as 280km apart), the fiber signal can be amplified to reach a
   distance of 280 km without attenuation.

3.2.4.  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 (IEEE 1588), distributing the synchronization
   signal over the IP/MPLS network.

   The Precision Time Protocol (PTP) is defined in IEEE standard 1588.
   PTP is applicable to distributed systems consisting of one or more
   nodes, communicating over a network.  Nodes are modeled as containing
   a real-time clock that may be used by applications within the node
   for various purposes such as generating time-stamps for data or
   ordering events managed by the node.  The protocol provides a
   mechanism for synchronizing the clocks of participating nodes to a
   high degree of accuracy and precision.

   PTP operates based on the following assumptions :

      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 eliminates cyclic forwarding of PTP messages
      between communication paths.

      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.  PTP
      also supports a unicast communication model as long as the
      behavior of the protocol is preserved.

      Like all message-based time transfer protocols, PTP time accuracy
      is degraded by asymmetry in the paths taken by event messages.
      Asymmetry is not detectable by PTP, however, if known, PTP
      corrects for asymmetry.

   A time-stamp event is generated at the time of transmission and
   reception of any event message.  The time-stamp event occurs when the
   message's timestamp point crosses the boundary between the node and
   the network.

   IEC 61850 will recommend the use of the IEEE PTP 1588 Utility Profile
   (as defined in IEC 62439-3 Annex B) which offers the support of
   redundant attachment of clocks to Paralell Redundancy Protcol (PRP)
   and High-availability Seamless Redundancy (HSR) networks.

3.3.  IANA Considerations

   This memo includes no request to IANA.

3.4.  Security Considerations

3.4.1.  Current Practices and Their Limitations

   Grid monitoring and control devices are already targets for cyber
   attacks and legacy telecommunications protocols have many intrinsic
   network related vulnerabilities.  DNP3, Modbus, PROFIBUS/PROFINET,
   and other protocols are designed around a common paradigm of request
   and respond.  Each protocol is designed for a master device such as
   an HMI (Human Machine Interface) system to send commands to
   subordinate slave devices to 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).

   o  Bump in the wire (BITW) solutions : A hardware device is added to
      provide IPSec services between two routers that are not capable of
      IPSec functions.  This special IPsec device will intercept then
      intercept outgoing datagrams, add IPSec protection to them, and
      strip it off incoming datagrams.  BITW can all IPSec to legacy
      hosts and can retrofit non-IPSec routers to provide security
      benefits.  The disadvantages are complexity and cost.

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

3.4.2.  Security Trends in Utility Networks

   Although advanced telecommunications networks can assist in
   transforming the energy industry, 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.  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's 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:

   1.  IP enables a rich set of features and capabilities to enhance the
   security posture

   2.  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.

3.5.  Acknowledgements

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

   Pascal Thubert, CTAO Cisco

4.  Building Automation Systems Use Cases
4.1.  Introduction

   Building Automation System (BAS) is a system that manages various
   equipment and sensors in buildings (e.g., heating, cooling and
   ventilating) for improving residents' comfort, reduction of energy
   consumption and automatic responses in case of failure and emergency.
   For example, BAS measures temperature of a room by using various
   sensors and then controls the HVAC (Heating, Ventilating, and air
   Conditioning) system automatically to maintain the temperature level
   and minimize the energy consumption.

   There are typically two layers of network in a BAS.  Upper one is
   called management network and the lower one is called field network.
   In management networks, an IP-based communication protocol is used
   while in field network, non-IP based communication protocols (a.k.a.,
   field protocol) are mainly used.

   There are many field protocols used in today's deployment in which
   some medium access control and physical layers protocols are
   standards-based and others are proprietary based.  Therefore the BAS
   needs to have multiple MAC/PHY modules and interfaces to make use of
   multiple field protocols based devices.  This situation not only
   makes BAS more expensive with large development cycle of multiple
   devices but also creates the issue of vendor lock-in with multiple
   types of management applications.

   The other issue with some of the existing field networks and
   protocols are security.  When these protocols and network were
   developed, it was assumed that the field networks are isolated
   physically from external networks and therefore the network and
   protocol security was not a concern.  However, in today's world many
   BASes are managed remotely and is connected to shared IP networks and
   it is also not uncommon that same IT infrastructure is used be it
   office, home or in enterprise networks.  Adding network and protocol
   security to existing system is a non-trivial task.

   This document first describes the BAS functionalities, its
   architecture and current deployment models.  Then we discuss the use
   cases and field network requirements that need to be satisfied by
   deterministic networking.

4.2.  BAS Functionality

   Building Automation System (BAS) is a system that manages various
   devices in buildings automatically.  BAS primarily performs the
   following functions:

   o  Measures states of devices in a regular interval.  For example,
      temperature or humidity or illuminance of rooms, on/off state of
      room lights, open/close state of doors, FAN speed, valve, running
      mode of HVAC, and its power consumption.

   o  Stores the measured data into a database (Note: The database keeps
      the data for several years).

   o  Provides the measured data for BAS operators for visualization.

   o  Generates alarms for abnormal state of devices (e.g., calling
      operator's cellular phone, sending an e-mail to operators and so

   o  Controls devices on demand.

   o  Controls devices with a pre-defined operation schedule (e.g., turn
      off room lights at 10:00 PM).

4.3.  BAS Architecture

   A typical BAS architecture is described below in Figure 1.  There are
   several elements in a BAS.

 +----------------------------+ | | | BMS HMI | | | | |
                        | +----------------------+ | | | Management Network | | |
                        +----------------------+ | | | | | | LC LC | | | | | |
                        +----------------------+ | | | Field Network | | | +----------------------+
                        | | | | | | | | Dev Dev Dev Dev | | | +----------------------------+ BMS :=
                        Building Management Server HMI := Human Machine Interface LC := Local

                        Figure 1: BAS architecture

   Human Machine Interface (HMI): It is commonly a computing platform
   (e.g., desktop PC) used by operators.  Operators perform the
   following operations through HMI.

   o  Monitoring devices: HMI displays measured device states.  For
      example, latest device states, a history chart of states, a popup
      window with an alert message.  Typically, the measured device
      states are stored in BMS (Building Management Server).

   o  Controlling devices: HMI provides ability to control the devices.
      For example, turn on a room light, set a target temperature to
      HVAC.  Several parameters (a target device, a control value,
      etc.), can be set by the operators which then HMI sends to a LC
      (Local Controller) via the management network.

   o  Configuring an operational schedule: HMI provides scheduling
      capability through which operational schedule is defined.  For
      example, schedule includes 1) a time to control, 2) a target
      device to control, and 3) a control value.  A specific operational
      example could be turn off all room lights in the building at 10:00
      PM.  This schedule is typically stored in BMS.

   Building Management Server (BMS) collects device states from LCs
   (Local Controllers) and stores it into a database.  According to its
   configuration, BMS executes the following operation automatically.

   o  BMS collects device states from LCs in a regular interval and then
      stores the information into a database.

   o  BMS sends control values to LCs according to a pre-configured

   o  BMS sends an alarm signal to operators if it detects abnormal
      devices states.  For example, turning on a red lamp, calling
      operators' cellular phone, sending an e-mail to operators.

   BMS and HMI communicate with Local Controllers (LCs) via IP-based
   communication protocol standardized by BACnet/IP [bacnetip], KNX/IP
   [knx].  These protocols are commonly called as management protocols.
   LCs measure device states and provide the information to BMS or HMI.
   These devices may include HVAC, FAN, doors, valves, lights, sensors
   (e.g., temperature, humidity, and illuminance).  LC can also set
   control values to the devices.  LC sometimes has additional
   functions, for example, sending a device state to BMS or HMI if the
   device state exceeds a certain threshold value, feedback control to a
   device to keep the device state at a certain state.  Typical example
   of LC is a PLC (Programmable Logic Controller).

   Each LC is connected with a different field network and communicates
   with several tens or hundreds of devices via the field network.
   Today there are many field protocols used in the field network.
   Based on the type of field protocol used, LC interfaces and its
   hardware/software could be different.  Field protocols are currently
   non-IP based in which some of them are standards-based (e.g., LonTalk
   [lontalk], Modbus [modbus], Profibus [profibus], FL-net [flnet],) and
   others are proprietary.

4.4.  Deployment Model

   An example BAS system deployment model for medium and large buildings
   is depicted in Figure 2 below.  In this case the physical layout of
   the entire system spans across multiple floors in which there is
   normally 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.

 +--------------------------------------------------+ |
                        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: Deployment model for Medium/Large Buildings

   Each LC is then connected to the monitoring room via the management
   network.  In this scenario, the management functions are performed
   locally and reside within the building.  In most cases, fast Ethernet
   (e.g. 100BASE-TX) is used for the management network.  In the field
   network, variety of physical interfaces such as RS232C, and RS485 are
   used.  Since management network is non-real time, Ethernet without
   quality of service is sufficient for today's deployment.  However,
   the requirements are different for field networks when they are
   replaced by either Ethernet or any wireless technologies supporting
   real time requirements (Section 3.4).

   Figure 3 depicts a deployment model in which the management can be
   hosted remotely.  This deployment is becoming popular for small
   office and residential buildings whereby having a standalone
   monitoring system is not a cost effective solution.  In such
   scenario, multiple buildings are managed by a remote management
   monitoring system.

 +---------------+ | 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

   In either case, interoperability today is only limited to the
   management network and its protocols.  In existing deployment, there
   are limited interoperability opportunity in the field network due to
   its nature of non-IP-based design and requirements.

4.5.  Use cases and Field Network Requirements

   In this section, we describe several use cases and corresponding
   network requirements.

4.5.1.  Environmental Monitoring

   In this use case, LCs measure environmental data (e.g. temperatures,
   humidity, illuminance, CO2, etc.) from several sensor devices at each
   measurement interval.  LCs keep latest value of each sensor.  BMS
   sends data requests to LCs to collect the latest values, then stores
   the collected values into a database.  Operators check the latest
   environmental data that are displayed by the HMI.  BMS also checks
   the collected data automatically to notify the operators if a room
   condition was going to bad (e.g., too hot or cold).  The following
   table lists the field network requirements in which the number of
   devices in a typical building will be ~100s per LC.

                  | Metric               | Requirement |
                  | Measurement interval | 100 msec    |
                  |                      |             |
                  | Availability         | 99.999 %    |

     Table 11: Field Network Requirements for Environmental Monitoring

   There is a case that BMS sends data requests at each 1 second in
   order to draw a historical chart of 1 second granularity.  Therefore
   100 msec measurement interval is sufficient for this use case,
   because typically 10 times granularity (compared with the interval of
   data requests) is considered enough accuracy in this use case.  A LC
   needs to measure values of all sensors connected with itself at each
   measurement interval.  Each communication delay in this scenario is
   not so critical.  The important requirement is completing
   measurements of all sensor values in the specified measurement
   interval.  The availability in this use case is very high (Three 9s).

4.5.2.  Fire Detection

   In the case of fire detection, HMI needs to show a popup window with
   an alert message within a few seconds after an abnormal state is
   detected.  BMS needs to do some operations if it detects fire.  For
   example, stopping a HVAC, closing fire shutters, and turning on fire
   sprinklers.  The following table describes requirements in which the
   number of devices in a typical building will be ~10s per LC.

                 | Metric               | Requirement   |
                 | Measurement interval | 10s of msec   |
                 |                      |               |
                 | Communication delay  | < 10s of msec |
                 |                      |               |
                 | Availability         | 99.9999 %     |

          Table 12: Field Network Requirements for Fire Detection

   In order to perform the above operation within a few seconds (1 or 2
   seconds) after detecting fire, LCs should measure sensor values at a
   regular interval of less than 10s of msec.  If a LC detects an
   abnormal sensor value, it sends an alarm information to BMS and HMI
   immediately.  BMS then controls HVAC or fire shutters or fire
   sprinklers.  HMI then displays a pop up window and generates the
   alert message.  Since the management network does not operate in real
   time, and software run on BMS or HMI requires 100s of ms, the
   communication delay should be less than ~10s of msec.  The
   availability in this use case is very high (Four 9s).

4.5.3.  Feedback Control

   Feedback control is used to keep a device state at a certain value.
   For example, keeping a room temperature at 27 degree Celsius, keeping
   a water flow rate at 100 L/m and so on.  The target device state is
   normally pre-defined in LCs or provided from BMS or from HMI.

   In feedback control procedure, a LC repeats the following actions at
   a regular interval (feedback interval).

   1.  The LC measures device states of the target device.

   2.  The LC calculates a control value by considering the measured
       device state.

   3.  The LC sends the control value to the target device.

   The feedback interval highly depends on the characteristics of the
   device and a target quality of control value.  While several tens of
   milliseconds feedback interval is sufficient to control a valve that
   regulates a water flow, controlling DC motors requires several
   milliseconds interval.  The following table describes the field
   network requirements in which the number of devices in a typical
   building will be ~10s per LC.

                 | Metric               | Requirement   |
                 | Feedback interval    | ~10ms - 100ms |
                 |                      |               |
                 | Communication delay  | < 10s of msec |
                 |                      |               |
                 | Communication jitter | < 1 msec      |
                 |                      |               |
                 | Availability         | 99.9999 %     |

         Table 13: Field Network Requirements for Feedback Control

   Small communication delay and jitter are required in this use case in
   order to provide high quality of feedback control.  This is currently
   offered in production environment with hgh availability (Four 9s).

4.6.  Security Considerations

   Both network and physical security of BAS are important.  While
   physical security is present in today's deployment, adequate network
   security and access control are either not implemented or configured
   properly.  This was sufficient in networks while they are isolated
   and not connected to the IT or other infrastructure networks but when
   IT and OT (Operational Technology) are connected in the same
   infrastructure network, network security is essential.  The
   management network being an IP-based network does have the protocols
   and knobs to enable the network security but in many cases BAS for
   example, does not use device authentication or encryption for data in
   transit.  On the contrary, many of today's field networks do not
   provide any security at all.  Following are the high level security
   requirements that the network should provide:

   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

   o  Availability of network data for normal and disaster scenario

5.  Wireless for Industrial Use Cases

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

5.1.  Introduction

   The emergence of wireless technology has enabled a variety of new
   devices to get interconnected, at a very low marginal cost per
   device, at any distance ranging from Near Field to interplanetary,
   and in circumstances where wiring may not be practical, for instance
   on fast-moving or rotating devices.

   At the same time, a new breed of Time Sensitive Networks is being
   developed to enable traffic that is highly sensitive to jitter, quite
   sensitive to latency, and with a high degree of operational
   criticality so that loss should be minimized at all times.  Such
   traffic is not limited to professional Audio/ Video networks, but is
   also found in command and control operations such as industrial
   automation and vehicular sensors and actuators.

   At IEEE802.1, the Audio/Video Task Group [IEEE802.1TSNTG] Time
   Sensitive Networking (TSN) to address Deterministic Ethernet.  The
   Medium access Control (MAC) of IEEE802.15.4 [IEEE802154] has evolved
   with the new TimeSlotted Channel Hopping (TSCH) [RFC7554] mode for
   deterministic industrial-type applications.  TSCH was introduced with
   the IEEE802.15.4e [IEEE802154e] amendment and will be wrapped up in
   the next revision of the IEEE802.15.4 standard.  For all practical
   purpose, this document is expected to be insensitive to the future
   versions of the IEEE802.15.4 standard, which is thus referenced

   Though at a different time scale, both TSN and TSCH standards provide
   Deterministic capabilities to the point that a packet that pertains
   to a certain flow crosses the network from node to node following a
   very precise schedule, as a train that leaves intermediate stations
   at precise times along its path.  With TSCH, time is formatted into
   timeSlots, and an individual cell is allocated to unicast or
   broadcast communication at the MAC level.  The time-slotted operation
   reduces collisions, saves energy, and enables to more closely
   engineer the network for deterministic properties.  The channel
   hopping aspect is a simple and efficient technique to combat multi-
   path fading and co-channel interferences (for example by Wi-Fi

   The 6TiSCH Architecture [I-D.ietf-6tisch-architecture] defines a
   remote monitoring and scheduling management of a TSCH network by a
   Path Computation Element (PCE), which cooperates with an abstract
   Network Management Entity (NME) to manage timeSlots and device
   resources in a manner that minimizes the interaction with and the
   load placed on the constrained devices.

   This Architecture applies the concepts of Deterministic Networking on
   a TSCH network to enable the switching of timeSlots in a G-MPLS
   manner.  This document details the dependencies that 6TiSCH has on
   PCE [PCE] and DetNet [I-D.finn-detnet-architecture] to provide the
   necessary capabilities that may be specific to such networks.  In
   turn, DetNet is expected to integrate and maintain consistency with
   the work that has taken place and is continuing at IEEE802.1TSN and

5.2.  Terminology

   Readers are expected to be familiar with all the terms and concepts
   that are discussed in "Multi-link Subnet Support in IPv6"

   The draft uses terminology defined or referenced in
   [I-D.ietf-6tisch-terminology] and

   The draft also conforms to the terms and models described in
   [RFC3444] and uses the vocabulary and the concepts defined in
   [RFC4291] for the IPv6 Architecture.

5.3.  6TiSCH Overview

   The scope of the present work is a subnet that, in its basic
   configuration, is made of a TSCH [RFC7554] MAC Low Power Lossy
   Network (LLN).

               ---+-------- ............ ------------
                  |      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 Configuration of a 6TiSCH Network

   In the extended configuration, a Backbone Router (6BBR) federates
   multiple 6TiSCH in a single subnet over a backbone. 6TiSCH 6BBRs
   synchronize with one another over the backbone, so as to ensure that
   the multiple LLNs that form the IPv6 subnet stay tightly

                  ---+-------- ............ ------------
                     |      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 Configuration of a 6TiSCH Network

   If the Backbone is Deterministic, then the Backbone Router ensures
   that the end-to-end deterministic behavior is maintained between the
   LLN and the backbone.  This SHOULD be done in conformance to the
   DetNet Architecture [I-D.finn-detnet-architecture] which studies
   Layer-3 aspects of Deterministic Networks, and covers networks that
   span multiple Layer-2 domains.  One particular requirement is that
   the PCE MUST be able to compute a deterministic path and to end
   across the TSCH network and an IEEE802.1 TSN Ethernet backbone, and
   DetNet MUST enable end-to-end deterministic forwarding.

   6TiSCH defines the concept of a Track, which is a complex form of a
   uni-directional Circuit ([I-D.ietf-6tisch-terminology]).  As opposed
   to a simple circuit that is a sequence of nodes and links, a Track is
   shaped as a directed acyclic graph towards a destination to support
   multi-path forwarding and route around failures.  A Track may also
   branch off and rejoin, for the purpose of the so-called Packet
   Replication and Elimination (PRE), over non congruent branches.  PRE
   may be used to complement layer-2 Automatic Repeat reQuest (ARQ) to
   meet industrial expectations in Packet Delivery Ratio (PDR), in
   particular when the Track extends beyond the 6TiSCH network.

                     | 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: End-to-End deterministic Track

   In the example above, 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 makes it in due time.  If two copies make it to
   the IoT gateway, the Elimination function in the gateway ignores the
   extra packet and presents only one copy to upper layers.

   At each 6TiSCH hop along the Track, the PCE may schedule more than
   one timeSlot for a packet, so as to support Layer-2 retries (ARQ).
   It is also possible that the field device only uses the second branch
   if sending over the first branch fails.

   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.

5.3.1.  TSCH and 6top

   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 operations are specified in

   The 6top data model and management interfaces are further discussed
   in [I-D.ietf-6tisch-6top-interface] and [I-D.ietf-6tisch-coap].

   The architecture defines "soft" cells and "hard" cells.  "Hard" cells
   are owned and managed by an separate scheduling entity (e.g. a PCE)
   that specifies the slotOffset/channelOffset of the cells to be
   added/moved/deleted, in which case 6top can only act as instructed,
   and may not move hard cells in the TSCH schedule on its own.

5.3.2.  SlotFrames and Priorities

   A slotFrame is the base object that the PCE needs to manipulate to
   program a schedule into an LLN node.  Elaboration on that concept can
   be found in section "SlotFrames and Priorities" of the 6TiSCH
   architecture [I-D.ietf-6tisch-architecture].  The architecture also
   details how the schedule is constructed and how transmission
   resources called cells can be allocated to particular transmissions
   so as to avoid collisions.

5.3.3.  Schedule Management by a PCE

   6TiSCH supports a mixed model of centralized routes and distributed
   routes.  Centralized routes can for example be computed by a entity
   such as a PCE.  Distributed routes are computed by RPL.

   Both methods may inject routes in the Routing Tables of the 6TiSCH
   routers.  In either case, each route is associated with a 6TiSCH
   topology that can be a RPL Instance topology or a track.  The 6TiSCH
   topology is indexed by a Instance ID, in a format that reuses the
   RPLInstanceID as defined in RPL [RFC6550].

   Both RPL and PCE rely on shared sources such as policies to define
   Global and Local RPLInstanceIDs that can be used by either method.
   It is possible for centralized and distributed routing to share a
   same topology.  Generally they will operate in different slotFrames,
   and centralized routes will be used for scheduled traffic and will
   have precedence over distributed routes in case of conflict between
   the slotFrames.

   Section "Schedule Management Mechanisms" of the 6TiSCH architecture
   describes 4 paradigms to manage the TSCH schedule of the LLN nodes:
   Static Scheduling, neighbor-to-neighbor Scheduling, remote monitoring
   and scheduling management, and Hop-by-hop scheduling.  The Track
   operation for DetNet corresponds to a remote monitoring and
   scheduling management by a PCE.

   The 6top interface document [I-D.ietf-6tisch-6top-interface]
   specifies the generic data model that can be used to monitor and
   manage resources of the 6top sublayer.  Abstract methods are
   suggested for use by a management entity in the device.  The data
   model also enables remote control operations on the 6top sublayer.

   [I-D.ietf-6tisch-coap] defines an mapping of the 6top set of
   commands, which is described in [I-D.ietf-6tisch-6top-interface], to
   CoAP resources.  This allows an entity to interact with the 6top
   layer of a node that is multiple hops away in a RESTful fashion.

   [I-D.ietf-6tisch-coap] also defines a basic set CoAP resources and
   associated RESTful access methods (GET/PUT/POST/DELETE).  The payload
   (body) of the CoAP messages is encoded using the CBOR format.  The
   PCE commands are expected to be issued directly as CoAP requests or
   to 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.

5.3.4.  Track Forwarding

   By forwarding, this specification means the per-packet operation that
   allows to deliver a packet to a next hop or an upper layer in this
   node.  Forwarding is based on pre-existing state that was installed
   as a result of the routing computation of a Track by a PCE.  The
   6TiSCH architecture supports three different forwarding model, G-MPLS
   Track Forwarding (TF), 6LoWPAN Fragment Forwarding (FF) and IPv6
   Forwarding (6F) which is the classical IP operation.  The DetNet case
   relates to the Track Forwarding operation under the control of a PCE.

   A Track is a unidirectional path between a source and a destination.
   In a Track cell, the normal operation of IEEE802.15.4 Automatic
   Repeat-reQuest (ARQ) usually happens, though the acknowledgment may
   be omitted in some cases, for instance if there is no scheduled cell
   for a retry.

   Track Forwarding is the simplest and fastest.  A bundle of cells set
   to receive (RX-cells) is uniquely paired to a bundle of cells that
   are set to transmit (TX-cells), representing a layer-2 forwarding
   state that can be used regardless of the network layer protocol.
   This model can effectively be seen as a Generalized Multi-protocol
   Label Switching (G-MPLS) operation in that the information used to
   switch a frame is not an explicit label, but rather related to other
   properties of the way the packet was received, a particular cell in
   the case of 6TiSCH.  As a result, as long as the TSCH MAC (and
   Layer-2 security) accepts a frame, that frame can be switched
   regardless of the protocol, whether this is an IPv6 packet, a 6LoWPAN
   fragment, or a frame from an alternate protocol such as WirelessHART
   or ISA100.11a.

   A data frame that is forwarded along a Track normally has a
   destination MAC address that is set to broadcast - or a multicast
   address depending on MAC support.  This way, the MAC layer in the
   intermediate nodes accepts the incoming frame and 6top switches it
   without incurring a change in the MAC header.  In the case of
   IEEE802.15.4, this means effectively broadcast, so that along the
   Track the short address for the destination of the frame is set to

   A Track is thus formed end-to-end as a succession of paired bundles,
   a receive bundle from the previous hop and a transmit bundle to the
   next hop along the Track, and a cell in such a bundle belongs to at
   most one Track.  For a given iteration of the device schedule, the
   effective channel of the cell is obtained by adding a pseudo-random
   number to the channelOffset of the cell, which results in a rotation
   of the frequency that used for transmission.  The bundles may be
   computed so as to accommodate both variable rates and
   retransmissions, so they might not be fully used at a given iteration
   of the schedule.  The 6TiSCH architecture provides additional means
   to avoid waste of cells as well as overflows in the transmit bundle,
   as follows:

   In one hand, a TX-cell that is not needed for the current iteration
   may be reused opportunistically on a per-hop basis for routed
   packets.  When all of the frame that were received for a given Track
   are effectively transmitted, any available TX-cell for that Track can
   be reused for upper layer traffic for which the next-hop router
   matches the next hop along the Track.  In that case, the cell that is
   being used is effectively a TX-cell from the Track, but the short
   address for the destination is that of the next-hop router.  It
   results that a frame that is received in a RX-cell of a Track with a
   destination MAC address set to this node as opposed to broadcast must
   be extracted from the Track and delivered to the upper layer (a frame
   with an unrecognized MAC address is dropped at the lower MAC layer
   and thus is not received at the 6top sublayer).

   On the other hand, it might happen that there are not enough TX-cells
   in the transmit bundle to accommodate the Track traffic, for instance
   if more retransmissions are needed than provisioned.  In that case,
   the frame can be placed for transmission in the bundle that is used
   for layer-3 traffic towards the next hop along the track as long as
   it can be routed by the upper layer, that is, typically, if the frame
   transports an IPv6 packet.  The MAC address should be set to the
   next-hop MAC address to avoid confusion.  It results that a frame
   that is received over a layer-3 bundle may be in fact associated to a
   Track.  In a classical IP link such as an Ethernet, off-track traffic
   is typically in excess over reservation to be routed along the non-
   reserved path based on its QoS setting.  But with 6TiSCH, since the
   use of the layer-3 bundle may be due to transmission failures, it
   makes sense for the receiver to recognize a frame that should be re-
   tracked, and to place it back on the appropriate bundle if possible.
   A frame should be re-tracked if the Per-Hop-Behavior group indicated
   in the Differentiated Services Field in the IPv6 header is set to
   Deterministic Forwarding, as discussed in Section 5.4.1.  A frame is
   re-tracked by scheduling it for transmission over the transmit bundle
   associated to the Track, with the destination MAC address set to

   There are 2 modes for a Track, transport mode and tunnel mode.  Transport Mode

   In transport mode, the Protocol Data Unit (PDU) is associated with
   flow-dependant meta-data that refers uniquely to the Track, so the
   6top sublayer can place the frame in the appropriate cell without
   ambiguity.  In the case of IPv6 traffic, this flow identification is
   transported in the Flow Label of the IPv6 header.  Associated with
   the source IPv6 address, the Flow Label forms a globally unique
   identifier for that particular Track that is validated at egress
   before restoring the destination MAC address (DMAC) and punting to
   the upper layer.

                          |                                    ^
      +--------------+    |                                    |
      |     IPv6     |    |                                    |
      +--------------+    |                                    |
      |  6LoWPAN HC  |    |                                    |
      +--------------+  ingress                              egress
      |     6top     |   sets     +----+          +----+     restores
      +--------------+  dmac to   |    |          |    |     dmac to
      |   TSCH MAC   |   brdcst   |    |          |    |      self
      +--------------+    |       |    |          |    |       |
      |   LLN PHY    |    +-------+    +--...-----+    +-------+

                     Track Forwarding, Transport Mode  Tunnel Mode

   In tunnel mode, the frames originate from an arbitrary protocol over
   a compatible MAC that may or may not be synchronized with the 6TiSCH
   network.  An example of this would be a router with a dual radio that
   is capable of receiving and sending WirelessHART or ISA100.11a frames
   with the second radio, by presenting itself as an access Point or a
   Backbone Router, respectively.

   In that mode, some entity (e.g.  PCE) can coordinate with a
   WirelessHART Network Manager or an ISA100.11a System Manager to
   specify the flows that are to be transported transparently over the

      |     IPv6     |
      |  6LoWPAN HC  |
      +--------------+             set            restore
      |     6top     |            +dmac+          +dmac+
      +--------------+          to|brdcst       to|nexthop
      |   TSCH MAC   |            |    |          |    |
      +--------------+            |    |          |    |
      |   LLN PHY    |    +-------+    +--...-----+    +-------+
      +--------------+    |   ingress                 egress   |
                          |                                    |
      +--------------+    |                                    |
      |   LLN PHY    |    |                                    |
      +--------------+    |                                    |
      |   TSCH MAC   |    |                                    |
      +--------------+    | dmac =                             | dmac =
      |ISA100/WiHART |    | nexthop                            v nexthop

                  Figure 7: Track Forwarding, Tunnel Mode

   In that case, the flow information that identifies the Track at the
   ingress 6TiSCH router is derived from the RX-cell.  The dmac is set
   to this node but the flow information indicates that the frame must
   be tunneled over a particular Track so the frame is not passed to the
   upper layer.  Instead, the dmac is forced to broadcast and the frame
   is passed to the 6top sublayer for switching.

   At the egress 6TiSCH router, the reverse operation occurs.  Based on
   metadata associated to the Track, the frame is passed to the
   appropriate link layer with the destination MAC restored.  Tunnel Metadata

   Metadata coming with the Track configuration is expected to provide
   the destination MAC address of the egress endpoint as well as the
   tunnel mode and specific data depending on the mode, for instance a
   service access point for frame delivery at egress.  If the tunnel
   egress point does not have a MAC address that matches the
   configuration, the Track installation fails.

   In transport mode, if the final layer-3 destination is the tunnel
   termination, then it is possible that the IPv6 address of the
   destination is compressed at the 6LoWPAN sublayer based on the MAC
   address.  It is thus mandatory at the ingress point to validate that
   the MAC address that was used at the 6LoWPAN sublayer for compression
   matches that of the tunnel egress point.  For that reason, the node
   that injects a packet on a Track checks that the destination is
   effectively that of the tunnel egress point before it overwrites it
   to broadcast.  The 6top sublayer at the tunnel egress point reverts
   that operation to the MAC address obtained from the tunnel metadata.

5.4.  Operations of Interest for DetNet and PCE

   In a classical system, the 6TiSCH device does not place the request
   for bandwidth between self and another device in the network.
   Rather, an Operation Control System invoked through an Human/Machine
   Interface (HMI) indicates the Traffic Specification, in particular in
   terms of latency and reliability, and the end nodes.  With this, the
   PCE must compute a Track 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 to recognize when a certain packet
   belongs to a certain Track, sort out duplicates, etc...

   For a static configuration that serves a certain purpose for a long
   period of time, it is expected that a node will be provisioned in one
   shot with a full schedule, which incorporates the aggregation of its
   behavior for multiple Tracks. 6TiSCH expects that the programing of
   the schedule will be done over COAP as discussed in 6TiSCH Resource
   Management and Interaction using CoAP [I-D.ietf-6tisch-coap].

   But an Hybrid mode may be required as well whereby a single Track is
   added, modified, or removed, for instance if it appears that a Track
   does not perform as expected for, say, PDR.  For that case, the
   expectation is that a protocol that flows along a Track (to be), in a
   fashion similar to classical Traffic Engineering (TE) [CCAMP], may be
   used to update the state in the devices. 6TiSCH provides means for a
   device to negotiate a timeSlot with a neighbor, but in general 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.

                         Operational System and HMI

      -+-+-+-+-+-+-+ Northbound -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

                PCE         PCE              PCE              PCE

      -+-+-+-+-+-+-+ Southbound -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

              --- 6TiSCH------6TiSCH------6TiSCH------6TiSCH--
     6TiSCH /     Device      Device      Device      Device   \
     Device-                                                    - 6TiSCH
            \     6TiSCH      6TiSCH      6TiSCH      6TiSCH   /  Device

                    Figure 8: Stream Management Entity

5.4.1.  Packet Marking and Handling

   Section "Packet Marking and Handling" of
   [I-D.ietf-6tisch-architecture] describes the packet tagging and
   marking that is expected in 6TiSCH networks.  Tagging Packets for Flow Identification

   For packets that are routed by a PCE along a Track, the tuple formed
   by the IPv6 source address and a local RPLInstanceID is tagged in the
   packets to identify uniquely the Track and associated transmit bundle
   of timeSlots.

   It results that the tagging that is used for a DetNet flow outside
   the 6TiSCH LLN MUST be swapped into 6TiSCH formats and back as the
   packet enters and then leaves the 6TiSCH network.

   Note: The method and format used for encoding the RPLInstanceID at
   6lo is generalized to all 6TiSCH topological Instances, which
   includes Tracks.  Replication, Retries and Elimination

   6TiSCH expects elimination and replication of packets along a complex
   Track, but has no position about how the sequence numbers would be
   tagged in the packet.

   As it goes, 6TiSCH expects that timeSlots corresponding to copies of
   a same packet along a Track are correlated by configuration, and does
   not need to process the sequence numbers.

   The semantics of the configuration MUST enable correlated timeSlots
   to be grouped for transmit (and respectively receive) with a 'OR'
   relations, and then a 'AND' relation MUST be configurable between
   groups.  The semantics is that if the transmit (and respectively
   receive) operation succeeded in one timeSlot in a 'OR' group, then
   all the other timeSLots in the group are ignored.  Now, if there are
   at least two groups, the 'AND' relation between the groups indicates
   that one operation must succeed in each of the groups.

   On the transmit side, timeSlots provisioned for retries along a same
   branch of a Track are placed a same 'OR' group.  The 'OR' relation
   indicates that if a transmission is acknowledged, then further
   transmissions SHOULD NOT be attempted for timeSlots in that group.
   There are as many 'OR' groups as there are branches of the Track
   departing from this node.  Different 'OR' groups are programmed for
   the purpose of replication, each group corresponding to one branch of
   the Track.  The 'AND' relation between the groups indicates that
   transmission over any of branches MUST be attempted regardless of
   whether a transmission succeeded in another branch.  It is also
   possible to place cells to different next-hop routers in a same 'OR'
   group.  This allows to route along multi-path tracks, trying one
   next-hop and then another only if sending to the first fails.

   On the receive side, all timeSlots are programmed in a same 'OR'
   group.  Retries of a same copy as well as converging branches for
   elimination are converged, meaning that the first successful
   reception is enough and that all the other timeSlots can be ignored.  Differentiated Services Per-Hop-Behavior

   Additionally, an IP packet that is sent along a Track uses the
   Differentiated Services Per-Hop-Behavior Group called Deterministic
   Forwarding, as described in

5.4.2.  Topology and capabilities

   6TiSCH nodes are usually IoT devices, characterized by very limited
   amount of memory, just enough buffers to store one or a few IPv6
   packets, and limited bandwidth between peers.  It results that a node
   will maintain only a small number of peering information, and will
   not be able to store many packets waiting to be forwarded.  Peers can
   be identified through MAC or IPv6 addresses, but a Cryptographically
   Generated Address [RFC3972] (CGA) may also be used.

   Neighbors can be discovered over the radio using mechanism such as
   beacons, but, though the neighbor information is available in the
   6TiSCH interface data model, 6TiSCH does not describe a protocol to
   pro-actively push the neighborhood information to a PCE.  This
   protocol should be described 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]

   The energy that the device consumes in sleep, transmit and receive
   modes can be evaluated and reported.  So can the amount of energy
   that is stored in the device and the power that it can be scavenged
   from the environment.  The PCE SHOULD be able to compute Tracks that
   will implement policies on how the energy is consumed, for instance
   balance between nodes, ensure that the spent energy does not exceeded
   the scavenged energy over a period of time, etc...

5.5.  Security Considerations

   On top of the classical protection of control signaling that can be
   expected to support DetNet, it must be noted that 6TiSCH networks
   operate on limited resources that can be depleted rapidly if an
   attacker manages to operate a DoS attack on the system, for instance
   by placing a rogue device in the network, or by obtaining management
   control and to setup extra paths.

5.6.  Acknowledgments

   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.

6.  Cellular Radio Use Cases

   (This section was derived from draft-korhonen-detnet-telreq-00)

6.1.  Introduction and background

   The recent developments in telecommunication networks, especially in
   the cellular domain, are heading towards transport networks where
   precise time synchronization support has to be one of the basic
   building blocks.  While the transport networks themselves have
   practically transitioned to all-AP packet based networks to meet the
   bandwidth and cost requirements, a highly accurate clock distribution
   has become a challenge.  Earlier the transport networks in the
   cellular domain were typically time division and 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)
   [SyncE] were used.  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.  The time and
   synchronization support are already topical for backhaul and midhaul
   packet networks [MEF], and becoming a real issue for fronthaul
   networks.  Specifically in the fronthaul networks the timing and
   synchronization requirements can be extreme for packet based
   technologies, for example, in order of sub +-20 ns packet delay
   variation (PDV) and frequency accuracy of +0.002 PPM [Fronthaul].

   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 (RAN)
   [].  Although various timing and
   synchronization optimizations have already been proposed and
   implemented including 1588 PTP enhancements
   [I-D.ietf-tictoc-1588overmpls][I-D.mirsky-mpls-residence-time], these
   solution are not necessarily sufficient for the forthcoming RAN
   architectures or guarantee the higher time-synchronization
   requirements [CPRI].  There are also existing solutions for the TDM
   over IP [RFC5087] [RFC4553] or Ethernet transports [RFC5086].  The
   really interesting and important existing 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.  While IEEE 802.1AS
   [IEEE8021AS] specifies a Layer-2 time synchronizing service other
   specification, 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].  Similarly to IEEE 1722 there
   is an ongoing standardization effort to define Layer-2 transport
   encapsulation format for transporting radio over Ethernet (RoE) in
   IEEE 1904.3 Task Force [IEEE19043].

   As already mentioned all-IP RANs and various "haul" 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, especially in MPLS/PWE space, to establish
   circuits through the routed and switched networks, there is a lack of
   signaling the time synchronization and time-sensitive stream
   requirements/reservations for Layer-3 flows in a way that the entire
   transport stack is addressed and the Ethernet layers that needs to be
   configured are addressed.  Furthermore, not all "user plane" traffic
   will be IP.  Therefore, the same solution need also address the use
   cases where the user plane traffic is again another layer or 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 eventually targets to provide solutions for time-sensitive (IP/
   transport) streams with deterministic properties over Ethernet-based
   switched networks.

   This document describes requirements for deterministic networking in
   a cellular telecom transport networks context.  The requirements
   include time synchronization, clock distribution and ways of
   establishing time-sensitive streams for both Layer-2 and Layer-3 user
   plane traffic using IETF protocol solutions.

   The recent developments in telecommunication networks, especially in
   the cellular domain, are heading towards transport networks where
   precise time synchronization support has to be one of the basic
   building blocks.  While the transport networks themselves have
   practically transitioned to all-AP packet based networks to meet the
   bandwidth and cost requirements, a highly accurate clock distribution
   has become a challenge.  Earlier the transport networks in the
   cellular domain were typically time division and 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)
   [SyncE] were used.  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.  The time and
   synchronization support are already topical for backhaul and midhaul
   packet networks [MEF], and becoming a real issue for fronthaul
   networks.  Specifically in the fronthaul networks the timing and
   synchronization requirements can be extreme for packet based
   technologies, for example, in order of sub +-20 ns packet delay
   variation (PDV) and frequency accuracy of +0.002 PPM [Fronthaul].

   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 (RAN)
   [].  Although various timing and
   synchronization optimizations have already been proposed and
   implemented including 1588 PTP enhancements
   [I-D.ietf-tictoc-1588overmpls][I-D.mirsky-mpls-residence-time], these
   solution are not necessarily sufficient for the forthcoming RAN
   architectures or guarantee the higher time-synchronization
   requirements [CPRI].  There are also existing solutions for the TDM
   over IP [RFC5087] [RFC4553] or Ethernet transports [RFC5086].  The
   really interesting and important existing 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.  While IEEE 802.1AS
   [IEEE8021AS] specifies a Layer-2 time synchronizing service other
   specification, 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].  Similarly to IEEE 1722 there
   is an ongoing standardization effort to define Layer-2 transport
   encapsulation format for transporting radio over Ethernet (RoE) in
   IEEE 1904.3 Task Force [IEEE19043].

   As already mentioned all-IP RANs and various "haul" 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, especially in MPLS/PWE space, to establish
   circuits through the routed and switched networks, there is a lack of
   signaling the time synchronization and time-sensitive stream
   requirements/reservations for Layer-3 flows in a way that the entire
   transport stack is addressed and the Ethernet layers that needs to be
   configured are addressed.  Furthermore, not all "user plane" traffic
   will be IP.  Therefore, the same solution need also address the use
   cases where the user plane traffic is again another layer or 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 eventually targets to provide solutions for time-sensitive (IP/
   transport) streams with deterministic properties over Ethernet-based
   switched networks.

   This document describes requirements for deterministic networking in
   a cellular telecom transport networks context.  The requirements
   include time synchronization, clock distribution and ways of
   establishing time-sensitive streams for both Layer-2 and Layer-3 user
   plane traffic using IETF protocol solutions.

6.2.  Network architecture

   Figure Figure 9 illustrates a typical, 3GPP defined, cellular network
   architecture, which also has fronthaul and midhaul network segments.
   The fronthaul refers to the network connecting base stations (base
   band processing units) to the remote radio heads (antennas).  The
   midhaul network typically refers to the network inter-connecting base
   stations (or small/pico cells).

   Fronthaul networks build on the available excess time after the base
   band processing of the radio frame has completed.  Therefore, the
   available time for networking is actually very limited, which in
   practise determines how far the remote radio heads can be from the
   base band processing units (i.e. base stations).  For example, in a
   case of LTE radio the Hybrid ARQ processing of a radio frame is
   allocated 3 ms.  Typically the processing completes way earlier (say
   up to 400 us, could be much less, though) thus allowing the remaining
   time to be used e.g. for fronthaul network. 200 us equals roughly 40
   km of optical fiber based transport (assuming round trip time would
   be total 2*200 us).  The base band processing time and the available
   "delay budget" for the fronthaul is a subject to change, possibly
   dramatically, in the forthcoming "5G" to meet, for example, the
   envisioned reduced radio round trip times, and other architecural and
   service requirements [NGMN].

   The maximum "delay budget" is then consumed by all nodes and required
   buffering between the remote radio head and the base band processing
   in addition to the distance incurred delay.  Packet delay variation
   (PDV) is problematic to fronthaul networks and must be minimized.  If
   the transport network cannot guarantee low enough PDV additional
   buffering has to be introduced at the edges of the network to buffer
   out the jitter.  Any buffering will eat up the total available delay
   budget, though.  Section Section 6.3 will discuss the PDV
   requirements in more detail.

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

      Figure 9: Generic 3GPP-based cellular network architecture with
                        Front/Mid/Backhaul networks

6.3.  Time synchronization requirements

   Cellular networks starting from long term evolution (LTE) [TS36300]
   [TS23401] radio the phase synchronization is also needed in addition
   to the frequency synchronization.  The commonly referenced fronthaul
   network synchronization requirements are typically drawn from the
   common public radio interface (CPRI) [CPRI] specification that
   defines the transport protocol between the base band processing -
   radio equipment controller (REC) and the remote antenna - radio
   equipment (RE).  However, the fundamental requirements still
   originate from the respective cellular system and radio
   specifications such as the 3GPP ones [TS25104][TS36104][TS36211]

   The fronthaul time synchronization requirements for the current 3GPP
   LTE-based networks are listed below:

   Transport link contribution to radio frequency error:

      +-2 PPB.  The given value is considered to be "available" for the
      fronthaul link out of the total 50 PPB budget reserved for the
      radio interface.

   Delay accuracy:

      +-8.138 ns i.e. +-1/32 Tc (UMTS Chip time, Tc, 1/3.84 MHz) to
      downlink direction and excluding the (optical) cable length in one
      direction.  Round trip accuracy is then +-16.276 ns.  The value is
      this low to meet the 3GPP timing alignment error (TAE) measurement

   Packet delay variation (PDV):

      *  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.

   The above listed time synchronization requirements are hard to meet
   even with point to point connected networks, not to mention cases
   where the underlying transport network actually constitutes of
   multiple hops.  It is expected that network deployments have to deal
   with the jitter requirements buffering at the very ends of the
   connections, 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 are valuable to make it easier
   to meet the end to end requirements.

   In order to meet the timing requirements both senders and receivers
   must is perfect sync.  This asks for a very accurate clock
   distribution solution.  Basically all means and hardware support for
   guaranteeing accurate time synchronization in the network is needed.
   As an example support for 1588 transparent clocks (TC) in every
   intermediate node would be helpful.

6.4.  Time-sensitive stream requirements

   In addition to the time synchronization requirements listed in
   Section Section 6.3 the fronthaul networks assume practically error
   free transport.  The maximum bit error rate (BER) has been defined to
   be 10^-12.  When packetized that would equal roughly to packet error
   rate (PER) of 2.4*10^-9 (assuming ~300 bytes packets).
   Retransmitting lost packets and/or using forward error coding (FEC)
   to circumvent bit errors are practically impossible due additional
   incurred delay.  Using redundant streams for better guarantees for
   delivery is also practically impossible due to high bandwidth
   requirements fronthaul networks have.  For instance, current
   uncompressed CPRI bandwidth expansion ratio is roughly 20:1 compared
   to the IP layer user payload it carries in a "radio sample form".

   The other fundamental assumption is that fronthaul links are
   symmetric.  Last, all fronthaul streams (carrying radio data) have
   equal priority and cannot delay or pre-empt each other.  This implies
   the network has always be sufficiently under subscribed to guarantee
   each time-sensitive flow meets their schedule.

   Mapping the fronthaul requirements to [I-D.finn-detnet-architecture]
   Section 3 "Providing the DetNet Quality of Service" what is seemed
   usable are:

      (a) Zero congestion loss.

      (b) Pinned-down paths.

   The current time-sensitive networking features may still not be
   sufficient for fronthaul traffic.  Therefore, having specific
   profiles that take the requirements of fronthaul into account are
   deemed to be useful [IEEE8021CM].

   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 not limited to
   solutions directly over Ethernet, over IP, and MPLS/PseudoWire

6.5.  Security considerations

   Establishing time-sensitive streams in the network entails reserving
   networking resources sometimes for a considerable long time.  It is
   important that these reservation requests must be authenticated to
   prevent malicious reservation attempts from hostile nodes or even
   accidental misconfiguration.  This is specifically important in a
   case where the reservation requests span administrative domains.
   Furthermore, the reservation information itself should be digitally
   signed to reduce the risk where a legitimate node pushed a stale or
   hostile configuration into the networking node.

7.  Industrial M2M

   (This section was derived from draft-varga-industrial-m2m-00)
7.1.  Introduction

   Traditional "industrial automation" and terminology usually  Use Case Description

   Industrial Automation in general refers to automation of
   manufacturing, quality control and material processing.  In practice, it means that this
   "machine to machine" (M2M) use case we consider machine units in a
   plant floor need cyclic
   control data which periodically exchange to data with upstream or
   downstream machine modules or to and/or a supervisory control in controller within a
   local network, which is often based on
   proprietary networking technologies today.

   For such area network.

   The actors of Machine to Machine (M2M) communication are Programmable
   Logic Controls (PLCs).  The communication between industrial entities, it PLCs and between
   PLCs and the supervisory PLC (S-PLC) is critical to
   ensure proper and deterministic end to end delivery time of messages
   with (very) high reliability and robustness, especially in closed
   loop automation control.

   Moreover, the recent trend is to use standard networking technologies
   in the local network and for connecting remote industrial automation
   sites, e.g., over an enterprise or metro network which also carries
   other types of traffic.  Therefore, deterministic flows should be
   guaranteed regardless of the amount of other flows in those networks
   for the deployment of future industrial automation.

   This document covers a selected industrial application, identifies
   representative solutions used today, and points on new use cases an
   IETF DetNet solution may enable.

7.2.  Terminology and Definitions

   DetNet:  Deterministic Networking.  [IETFDetNet]

   M2M:  Machine to Machine.

   MES:  Manufacturing-Execution-System.

   PLC:  Programmable Logic Control.

   S-PLC:  Supervisory Programmable Logic Control.

7.3.  Machine to Machine communication over IP networks

   In case of industrial automation, the actors of Machine to Machine
   (M2M) communication are Programmable Logic Controls (PLC).  The
   communication between PLCs and between PLCs and the supervisory PLC
   (S-PLC) is achieved via achieved via critical
   Control-Data-Streams Figure 10.
   This draft focuses on PLC related communications and communication to
   Manufacturing-Execution-System (MES) are out-of-scope.  The PLC
   related Control-Data-Streams are transmitted periodically and they
   are established either with (i) a pre-configured payload or (ii) a
   payload configuration during runtime.

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

      Figure 10: Current generic Generic Industrial M2M Network Architecture

   This use case addresses PLC-related communications; communication to
   Manufacturing-Execution-Systems (MESs) are not addressed.

   This use case addresses only critical Control-Data-Streams; non-
   critical traffic between industrial automation applications (such as
   communication of state, configuration, set-up, connection to
   Manufacturing-Execution-System (MES) 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 critical.

   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
   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, deterministic flows need to be
   sustained regardless of the amount of other flows in those networks.

7.2.  Industrial M2M network architecture Communication Today

   Today, proprietary networks fulfill the needed timing and
   availability for M2M networks, as described in this section.

   The network topologies used today by applications of industrial automation are (i) daisy chain, (ii) ring
   similar to those used by telecom networks: Daisy Chain, Ring, Hub and (iii) hub
   Spoke, and spoke.
   Such topologies are often used in telecommunication networks too.  In
   industrial networks comb (being a Comb (a subset of daisy-chain) is also
   used. Daisy Chain).

   PLC-related Control-Data-Streams are transmitted periodically and
   they are established either with a pre-configured payload or a
   payload configured during runtime.

   Some industrial applications require Time Synchronization (Sync) to time synchronization ("time
   sync") at the end nodes, which is also similar to some telecommunication networks,
   e.g., mobile Radio Access Networks. nodes.  For such time coordinated time-coordinated PLCs, accuracy of
   1 microseconds microsecond is required.  In  Even in the case of non-time
   coordinated PLCs, a requirement for Time Sync "non-time-
   coordinated" PLCs time sync may still exist, e.g., be needed e.g. for time stamping timestamping of collected measurement (sensor)
   sensor data.

7.4.  Machine to Machine communication requirements

   The requirements listed here refer to critical Control-Data-Streams.
   Non-critical traffic of industrial automation applications can be
   served with currently available prioritizing techniques.

   In an industrial environment, non-time-critical traffic is related to
   (i) communication of state, configuration, set-up, etc., (ii)
   connection to Manufacturing-Execution-System (MES) and (iii) database
   communication.  Such type of traffic can use up to 80%

   Industrial network scenarios require advanced security solutions.
   Many of the
   available bandwidth.  There is a subset of non-time-critical traffic
   that their bandwidth should be guaranteed.

   The rest current industrial production networks are physically
   separated.  Protection of this chapter is dealing only with time-critical traffic.

7.4.1. critical flows are handled today by
   gateways / firewalls.

7.2.1.  Transport parameters Parameters

   The Cycle Time defines the frequency of message(s) between industrial
   actors.  The Cycle Time is application dependent, it is in the range of 1ms
   - 100ms for critical Control-Data-Streams.


   Because industrial applications assume deterministic transport instead for
   critical Control-Data-Stream parameters (instead of defining latency
   and delay variation parameters for critical Control-
   Data-Stream parameters, parameters) it is enough sufficient to fulfill the upper
   bound of latency (maximum latency).  The communication 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

   Bandwidth requirements of Control-Data-Streams are usually calculated
   directly from the bytes per cycle bytes-per-cycle parameter of the control loop.  For
   PLC to PLC
   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 need - up to be supported. 256 streams.  Usually no more than 20%
   of available bandwidth is used for critical Control-
   Data-Streams in Control-Data-Streams.  In
   today's networks, which comprise Gbps links.

   Usual networks 1Gbps links are commonly used.

   Most PLC control loops are rather tolerant for of packet loss.
   Critical loss, however
   critical Control-Data-Streams accept no more than 1 packet loss per
   consecutive communication cycles.  The 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, it hits the 5 nines high (99,999%).

   Based on the above parameters, it can be concluded parameters we expect that some form of redundancy might
   will be required for M2M communication.  The actual communications, however any individual
   solution depends on several parameters, like parameters including cycle time, delivery
   time, etc.

7.4.2.  Flow maintenance

   Most Critical Control-Data-Streams get created at startup, however,
   flexibility is also needed during runtime (e.g. add / remove

7.2.2.  Stream Creation and Destruction

   In an industrial environment, critical Control-Data-
   Streams Control-Data-Streams are
   created rather infrequent: infrequently, on the order of ~10 times per day / week
   / month.  With the future advent  Most of flexible 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, flow
   maintenance parameters are expected to systems become more flexible, we expect a significant
   increase significantly.

7.5.  Summary

   This document specifies an industrial machine-to-machine use-case in the DetNet context.

7.6.  Security Considerations rate at which streams are created, changed and

7.3.  Industrial M2M Future

   We would like to see the various proprietary networks replaced with a
   converged standards-based network scenarios require advanced security solutions.
   Many of with deterministic properties that
   can satisfy the timing and reliability constraints described above.

7.4.  Industrial M2M Asks

   We can summarize the current industrial production networks are physically
   separated.  Protection of critical flows are handled today by
   gateways / firewalls.

7.7. requirements stated above as follows:

                | Metric                  | Requirement  |
                | Sync Accuracy           | 1 usec       |
                |                         |              |
                | Message Delivery Time   | 100us - 50ms |
                |                         |              |
                | Packet loss (burstless) | 0.1-1 %      |
                |                         |              |
                | Availability            | 99.999 %     |

                Table 14: Actor-to-Actor Timing Parameters

7.5.  Acknowledgements

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

8.  Other Use Cases

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

8.1.  Introduction

   The rapid growth of the today's communication system and its access
   into almost all aspects of daily life has led to great dependency on
   services it provides.  The communication network, as it is today, has
   applications such as multimedia and peer-to-peer file sharing
   distribution that require Quality of Service (QoS) guarantees in
   terms of delay and jitter to maintain a certain level of performance.
   Meanwhile, mobile wireless communications has become an important
   part to support modern sociality with increasing importance over the
   last years.  A communication network of hard real-time and high
   reliability is essential for the next concurrent and next generation
   mobile wireless networks as well as its bearer network for E-2-E
   performance requirements.

   Conventional transport network is IP-based because of the bandwidth
   and cost requirements.  However the delay and jitter guarantee
   becomes a challenge in case of contention since the service here is
   not deterministic but best effort.  With more and more rigid demand
   in latency control in the future network [METIS], deterministic
   networking [I-D.finn-detnet-architecture] is a promising solution to
   meet the ultra low delay applications and use cases.  There are
   already typical issues for delay sensitive networking requirements in
   midhaul and backhaul network to support LTE and future 5G network
   [net5G].  And not only in the telecom industry but also other
   vertical industry has increasing demand on delay sensitive
   communications as the automation becomes critical recently.

   More specifically, CoMP techniques, D-2-D, industrial automation and
   gaming/media service all have great dependency on the low delay
   communications as well as high reliability to guarantee the service
   performance.  Note that the deterministic networking is not equal to
   low latency as it is more focused on the worst case delay bound of
   the duration of certain application or service.  It can be argued
   that without high certainty and absolute delay guarantee, low delay
   provisioning is just relative [rfc3393], which is not sufficient to
   some delay critical service since delay violation in an instance
   cannot be tolerated.  Overall, the requirements from vertical
   industries seem to be well aligned with the expected low latency and
   high determinist performance of future networks

   This document describes several use cases and scenarios with
   requirements on deterministic delay guarantee within the scope of the
   deterministic network [I-D.finn-detnet-problem-statement].

8.2.  Critical Delay Requirements

   Delay and jitter requirement has been take into account as a major
   component in QoS provisioning since the birth of Internet.  The delay
   sensitive networking with increasing importance become the root of
   mobile wireless communications as well as the applicable areas which
   are all greatly relied on low delay communications.  Due to the best
   effort feature of the IP networking, mitigate contention and
   buffering is the main solution to serve the delay sensitive service.
   More bandwidth is assigned to keep the link low loaded or in another
   word, reduce the probability of congestion.  However, not only lack
   of determinist but also has limitation to serve the applications in
   the future communication system, keeping low loaded cannot provide
   deterministic delay guarantee.  Take the [METIS] that documents the
   fundamental challenges as well as overall technical goal of the 5G
   mobile and wireless system as the starting point.  It should
   supports: -1000 times higher mobile data volume per area, -10 times
   to 100 times higher typical user data rate, -10 times to 100 times
   higher number of connected devices, -10 times longer battery life for
   low power devices, and -5 times reduced End-to-End (E2E) latency, at
   similar cost and energy consumption levels as today's system.  Taking
   part of these requirements related to latency, current LTE networking
   system has E2E latency less than 20ms [LTE-Latency] which leads to
   around 5ms E2E latency for 5G networks.  It has been argued that
   fulfill such rigid latency demand with similar cost will be most
   challenging as the system also requires 100 times bandwidth as well
   as 100 times of connected devices.  As a result to that, simply
   adding redundant bandwidth provisioning can be no longer an efficient
   solution due to the high bandwidth requirements more than ever
   before.  In addition to the bandwidth provisioning, the critical flow
   within its reserved resource should not be affected by other flows no
   matter the pressure of the network.  Robust defense of critical flow
   is also not depended on redundant bandwidth allocation.
   Deterministic networking techniques in both layer-2 and layer-3 using
   IETF protocol solutions can be promising to serve these scenarios.

8.3.  Coordinated multipoint processing (CoMP)

   In the wireless communication system, Coordinated multipoint
   processing (CoMP) is considered as an effective technique to solve
   the inter-cell interference problem to improve the cell-edge user
   throughput [CoMP].

8.3.1.  CoMP Architecture

                |           CoMP           |
                   |                    |
             +----------+             +------------+
             |  Uplink  |             |  Downlink  |
             +-----+----+             +--------+---+
                   |                           |
        -------------------              -----------------------
        |         |       |              |           |         |
   +---------+ +----+  +-----+       +------------+ +-----+  +-----+
   |  Joint  | | CS |  | DPS |       |    Joint   | | CS/ |  | DPS |
   |Reception| |    |  |     |       |Transmission| | CB  |  |     |
   +---------+ +----+  +-----+       +------------+ +-----+  +-----+
        |                                     |
        |-----------                          |-------------
        |          |                          |            |
   +------------+  +---------+       +----------+   +------------+
   |    Joint   |  |   Soft  |       | Coherent |   |     Non-   |
   |Equalization|  |Combining|       |    JT    |   | Coherent JT|
   +------------+  +---------+       +----------+   +------------+

                  Figure 11: Framework of CoMP Technology

   As shown in Figure 11, CoMP reception and transmission is a framework
   that 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-UEs transmission to a multi-cell- to-multi-UEs
   transmission by base station cooperation.  In contrast to single-cell
   scenario, CoMP has critical issues such as: Backhaul latency, CSI
   (Channel State Information) reporting and accuracy and Network
   complexity.  Clearly the first two requirements are very much delay
   sensitive and will be discussed in next section.

8.3.2.  Delay Sensitivity in CoMP

   As the essential feature of CoMP, signaling is exchanged between
   eNBs, the backhaul latency is the dominating limitation of the CoMP
   performance.  Generally, JT and JP may benefit from coordinating the
   scheduling (distributed or centralized) of different cells in case
   that the signaling exchanging between eNBs is limited to 4-10ms.  For
   C-RAN the backhaul latency requirement is 250us while for D-RAN it is
   4-15ms.  And this delay requirement is not only rigid but also
   absolute since any uncertainty in delay will down the performance
   significantly.  Note that, some operator's transport network is not
   build to support Layer-3 transfer in aggregation layer.  In such
   case, the signaling is exchanged through EPC which means delay is
   supposed to be larger.  CoMP has high requirement on delay and
   reliability which is lack by current mobile network systems and may
   impact the architecture of the mobile network.

8.4.  Industrial Automation

   Traditional "industrial automation" terminology usually refers to
   automation of manufacturing, quality control and material processing.
   "Industrial internet" and "industrial 4.0" [EA12] is becoming a hot
   topic based on the Internet of Things.  This high flexible and
   dynamic engineering and manufacturing will result in a lot of so-
   called smart approaches such as Smart Factory, Smart Products, Smart
   Mobility, and Smart Home/Buildings.  No doubt that ultra high
   reliability and robustness is a must in data transmission, especially
   in the closed loop automation control application where delay
   requirement is below 1ms and packet loss less than 10E-9.  All these
   critical requirements on both latency and loss cannot be fulfilled by
   current 4G communication networks.  Moreover, the collaboration of
   the industrial automation from remote campus with cellular and fixed
   network has to be built on an integrated, cloud-based platform.  In
   this way, the deterministic flows should be guaranteed regardless of
   the amount of other flows in the network.  The lack of this mechanism
   becomes the main obstacle in deployment on of industrial automation.

8.5.  Vehicle to Vehicle

   V2V communication has gained more and more attention in the last few
   years and will be increasingly growth in the future.  Not only
   equipped with direct communication system which is short ranged, V2V
   communication also requires wireless cellular networks to cover wide
   range and more sophisticated services.  V2V application in the area
   autonomous driving has very stringent requirements of latency and
   reliability.  It is critical that the timely arrival of information
   for safety issues.  In addition, due to the limitation of processing
   of individual vehicle, passing information to the cloud can provide
   more functions such as video processing, audio recognition or
   navigation systems.  All of those requirements lead to a highly
   reliable connectivity to the cloud.  On the other hand, it is natural
   that the provisioning of low latency communication is one of the main
   challenges to be overcome as a result of the high mobility, the high
   penetration losses caused by the vehicle itself.  As result of that,
   the data transmission with latency below 5ms and a high reliability
   of PER below 10E-6 are demanded.  It can benefit from the deployment
   of deterministic networking with high reliability.

8.6.  Gaming, Media and Virtual Reality

   Online gaming and cloud gaming is dominating the gaming market since
   it allow multiple players to play together with more challenging and
   competing.  Connected via current internet, the latency can be a big
   issue to degrade the end users' experience.  There different types of
   games and FPS (First Person Shooting) gaming has been considered to
   be the most latency sensitive online gaming due to the high
   requirements of timing precision and computing of moving target.
   Virtual reality is also receiving more interests than ever before as
   a novel gaming experience.  The delay here can be very critical to
   the interacting in the virtual world.  Disagreement between what is
   seeing and what is feeling can cause motion sickness and affect what
   happens in the game.  Supporting fast, real-time and reliable
   communications in both PHY/MAC layer, network layer and application
   layer is main bottleneck for such use case.  The media content
   delivery has been and will become even more important use of
   Internet.  Not only high bandwidth demand but also critical delay and
   jitter requirements have to be taken into account to meet the user
   demand.  To make the smoothness of the video and audio, delay and
   jitter has to be guaranteed to avoid possible interruption which is
   the killer of all online media on demand service.  Now with 4K and 8K
   video in the near future, the delay guarantee become one of the most
   challenging issue than ever before. 4K/8K UHD video service requires
   6Gbps-100Gbps for uncompressed video and compressed video starting
   from 60Mbps.  The delay requirement is 100ms while some specific
   interactive applications may require 10ms delay [UHD-video].

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)

   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

   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

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              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
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              over Low-Power Wireless Personal Area Networks (6LoWPANs):
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              and D. Barthel, "Routing Metrics Used for Path Calculation
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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
   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

   Janos Farkas
   Konyves Kalman krt. 11/B
   Budapest  1097


   Franz-Josef Goetz
   Gleiwitzerstr. 555
   Nurnberg  90475


   Juergen Schmitt
   Gleiwitzerstr. 555
   Nurnberg  90475