Deterministic Networking (DetNet) Security Considerations
draft-ietf-detnet-security-01

Internet Engineering Task Force                               T. Mizrahi
Internet-Draft                                                   MARVELL
Intended status: Informational                          E. Grossman, Ed.
Expires: April 2, 2018                                             DOLBY
                                                               A. Hacker
                                                                  MISTIQ
                                                                  S. Das
                                          Applied Communication Sciences
                                                              J. Dowdell
                                                Airbus Defence and Space
                                                               H. Austad
                                                           Cisco Systems
                                                              K. Stanton
                                                                   INTEL
                                                                 N. Finn
                                                                  HUAWEI
                                                      September 29, 2017


       Deterministic Networking (DetNet) Security Considerations
                     draft-ietf-detnet-security-00

Abstract

   A deterministic network is one that can carry data flows for real-
   time applications with extremely low data loss rates and bounded
   latency.  Deterministic networks have been successfully deployed in
   real-time operational technology (OT) applications for some years
   (for example [ARINC664P7]).  However, such networks are typically
   isolated from external access, and thus the security threat from
   external attackers is low.  IETF Deterministic Networking (DetNet)
   specifies a set of technologies that enable creation of deterministic
   networks on IP-based networks of potentially wide area (on the scale
   of a corporate network) potentially bringing the OT network into
   contact with Information Technology (IT) traffic and security threats
   that lie outside of a tightly controlled and bounded area (such as
   the internals of an aircraft).  These DetNet technologies have not
   previously been deployed together on a wide area IP-based network,
   and thus can present security considerations that may be new to IP-
   based wide area network designers.  This draft, intended for use by
   DetNet network designers, provides insight into these security
   considerations.  In addition, this draft collects all security-
   related statements from the various DetNet drafts (Architecture, Use
   Cases, etc) into a single location Section 7.







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Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on April 2, 2018.

Copyright Notice

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Abbreviations . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Security Threats  . . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  Threat Model  . . . . . . . . . . . . . . . . . . . . . .   6
     3.2.  Threat Analysis . . . . . . . . . . . . . . . . . . . . .   7
       3.2.1.  Delay . . . . . . . . . . . . . . . . . . . . . . . .   7
         3.2.1.1.  Delay Attack  . . . . . . . . . . . . . . . . . .   7
       3.2.2.  DetNet Flow Identification  . . . . . . . . . . . . .   7
         3.2.2.1.  DetNet Flow Modification or Spoofing  . . . . . .   7
       3.2.3.  Resource Segmentation or Slicing  . . . . . . . . . .   7
         3.2.3.1.  Inter-segment Attack  . . . . . . . . . . . . . .   7
       3.2.4.  Packet Replication and Elimination  . . . . . . . . .   7
         3.2.4.1.  Replication: Increased Attack Surface . . . . . .   8
         3.2.4.2.  Replication-related Header Manipulation . . . . .   8



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       3.2.5.  Path Choice . . . . . . . . . . . . . . . . . . . . .   8
         3.2.5.1.  Path Manipulation . . . . . . . . . . . . . . . .   8
         3.2.5.2.  Path Choice: Increased Attack Surface . . . . . .   8
       3.2.6.  Control Plane . . . . . . . . . . . . . . . . . . . .   9
         3.2.6.1.  Control or Signaling Packet Modification  . . . .   9
         3.2.6.2.  Control or Signaling Packet Injection . . . . . .   9
       3.2.7.  Scheduling or Shaping . . . . . . . . . . . . . . . .   9
         3.2.7.1.  Reconnaissance  . . . . . . . . . . . . . . . . .   9
       3.2.8.  Time Synchronization Mechanisms . . . . . . . . . . .   9
     3.3.  Threat Summary  . . . . . . . . . . . . . . . . . . . . .   9
   4.  Security Threat Impacts . . . . . . . . . . . . . . . . . . .  10
     4.1.  Delay-Attacks . . . . . . . . . . . . . . . . . . . . . .  10
       4.1.1.  Data Plane Delay Attacks  . . . . . . . . . . . . . .  11
       4.1.2.  Control Plane Delay Attacks . . . . . . . . . . . . .  11
     4.2.  Flow Identification and Spoofing  . . . . . . . . . . . .  11
       4.2.1.  Flow identification . . . . . . . . . . . . . . . . .  11
       4.2.2.  Spoofing  . . . . . . . . . . . . . . . . . . . . . .  12
         4.2.2.1.  Dataplane Spoofing  . . . . . . . . . . . . . . .  12
         4.2.2.2.  Control Plane Spoofing  . . . . . . . . . . . . .  12
     4.3.  Segmentation attacks (injection)  . . . . . . . . . . . .  12
       4.3.1.  Data Plane Segmentation . . . . . . . . . . . . . . .  12
       4.3.2.  Control Plane segmentation  . . . . . . . . . . . . .  13
     4.4.  Replication and Elimination . . . . . . . . . . . . . . .  13
       4.4.1.  Increased Attack Surface  . . . . . . . . . . . . . .  13
       4.4.2.  Header Manipulation at Elimination Bridges  . . . . .  13
     4.5.  Impact of Attacks to Path Choice  . . . . . . . . . . . .  13
     4.6.  Impact of Attacks by Use Case Industry  . . . . . . . . .  13
   5.  Security Threat Mitigation  . . . . . . . . . . . . . . . . .  15
     5.1.  Path Redundancy . . . . . . . . . . . . . . . . . . . . .  16
     5.2.  Integrity Protection  . . . . . . . . . . . . . . . . . .  16
     5.3.  DetNet Node Authentication  . . . . . . . . . . . . . . .  16
     5.4.  Encryption  . . . . . . . . . . . . . . . . . . . . . . .  17
     5.5.  Control and Signaling Message Protection  . . . . . . . .  17
     5.6.  Dynamic Performance Analytics . . . . . . . . . . . . . .  17
     5.7.  Mitigation Summary  . . . . . . . . . . . . . . . . . . .  18
   6.  Association of Attacks to Use Cases . . . . . . . . . . . . .  19
     6.1.  Use Cases by Common Themes  . . . . . . . . . . . . . . .  19
       6.1.1.  Network Layer - AVB/TSN Ethernet  . . . . . . . . . .  19
       6.1.2.  Central Administration  . . . . . . . . . . . . . . .  19
       6.1.3.  Hot Swap  . . . . . . . . . . . . . . . . . . . . . .  20
       6.1.4.  Data Flow Information Models  . . . . . . . . . . . .  20
       6.1.5.  L2 and L3 Integration . . . . . . . . . . . . . . . .  20
       6.1.6.  End-to-End Delivery . . . . . . . . . . . . . . . . .  20
       6.1.7.  Proprietary Deterministic Ethernet Networks . . . . .  20
       6.1.8.  Replacement for Proprietary Fieldbuses  . . . . . . .  20
       6.1.9.  Deterministic vs Best-Effort Traffic  . . . . . . . .  21
       6.1.10. Deterministic Flows . . . . . . . . . . . . . . . . .  21
       6.1.11. Unused Reserved Bandwidth . . . . . . . . . . . . . .  21



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       6.1.12. Interoperability  . . . . . . . . . . . . . . . . . .  21
       6.1.13. Cost Reductions . . . . . . . . . . . . . . . . . . .  21
       6.1.14. Insufficiently Secure Devices . . . . . . . . . . . .  22
       6.1.15. DetNet Network Size . . . . . . . . . . . . . . . . .  22
       6.1.16. Multiple Hops . . . . . . . . . . . . . . . . . . . .  22
       6.1.17. Level of Service  . . . . . . . . . . . . . . . . . .  22
       6.1.18. Bounded Latency . . . . . . . . . . . . . . . . . . .  23
       6.1.19. Low Latency . . . . . . . . . . . . . . . . . . . . .  23
       6.1.20. Symmetrical Path Delays . . . . . . . . . . . . . . .  23
       6.1.21. Reliability and Availability  . . . . . . . . . . . .  23
       6.1.22. Redundant Paths . . . . . . . . . . . . . . . . . . .  24
       6.1.23. Security Measures . . . . . . . . . . . . . . . . . .  24
     6.2.  Attack Types by Use Case Common Theme . . . . . . . . . .  24
   7.  Appendix A: DetNet Draft Security-Related Statements  . . . .  26
     7.1.  Architecture (draft 8)  . . . . . . . . . . . . . . . . .  27
       7.1.1.  Fault Mitigation (sec 4.5)  . . . . . . . . . . . . .  27
       7.1.2.  Security Considerations (sec 7) . . . . . . . . . . .  27
     7.2.  Data Plane Alternatives (draft 4) . . . . . . . . . . . .  28
       7.2.1.  Security Considerations (sec 7) . . . . . . . . . . .  28
     7.3.  Problem Statement (draft 5) . . . . . . . . . . . . . . .  28
       7.3.1.  Security Considerations (sec 5) . . . . . . . . . . .  28
     7.4.  Use Cases (draft 11)  . . . . . . . . . . . . . . . . . .  29
       7.4.1.  (Utility Networks) Security Current Practices and
               Limitations (sec 3.2.1) . . . . . . . . . . . . . . .  29
       7.4.2.  (Utility Networks) Security Trends in Utility
               Networks (sec 3.3.3)  . . . . . . . . . . . . . . . .  30
       7.4.3.  (BAS) Security Considerations (sec 4.2.4) . . . . . .  32
       7.4.4.  (6TiSCH) Security Considerations (sec 5.3.3)  . . . .  32
       7.4.5.  (Cellular radio) Security Considerations (sec 6.1.5)   32
       7.4.6.  (Industrial M2M) Communication Today (sec 7.2)  . . .  33
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  33
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  33
   10. Informative References  . . . . . . . . . . . . . . . . . . .  33
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  34

1.  Introduction

   Security is of particularly high importance in DetNet networks
   because many of the use cases which are enabled by DetNet
   [I-D.ietf-detnet-use-cases] include control of physical devices
   (power grid components, industrial controls, building controls) which
   can have high operational costs for failure, and present potentially
   attractive targets for cyber-attackers.

   This situation is even more acute given that one of the goals of
   DetNet is to provide a "converged network", i.e. one that includes
   both IT traffic and OT traffic, thus exposing potentially sensitive
   OT devices to attack in ways that were not previously common (usually



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   because they were under a separate control system or otherwise
   isolated from the IT network).  Security considerations for OT
   networks is not a new area, and there are many OT networks today that
   are connected to wide area networks or the Internet; this draft
   focuses on the issues that are specific to the DetNet technologies
   and use cases.

   The DetNet technologies include ways to:

   o  Reserve data plane resources for DetNet flows in some or all of
      the intermediate nodes (e.g. bridges or routers) along the path of
      the flow

   o  Provide explicit routes for DetNet flows that do not rapidly
      change with the network topology

   o  Distribute data from DetNet flow packets over time and/or space to
      ensure delivery of each packet's data' in spite of the loss of a
      path

   This draft includes sections on threat modeling and analysis, threat
   impact and mitigation, and the association of various attacks with
   various use cases both by industry and based on the Use Case Common
   Themes section of the DetNet Use Cases draft
   [I-D.ietf-detnet-use-cases].

   This draft also provides context for the DetNet security
   considerations by collecting into one place Section 7 the various
   remarks about security from the various DetNet drafts (Use Cases,
   Architecture, etc).  This text is duplicated here primarily because
   the DetNet working group has elected not to produce a Requirements
   draft and thus collectively these statements are as close as we have
   to "DetNet Security Requirements".

2.  Abbreviations

   IT         Information technology (the application of computers to
   store, study, retrieve, transmit, and manipulate data or information,
   often in the context of a business or other enterprise - Wikipedia).

   OT         Operational Technology (the hardware and software
   dedicated to detecting or causing changes in physical processes
   through direct monitoring and/or control of physical devices such as
   valves, pumps, etc. - Wikipedia)

   MITM       Man in the Middle

   SN         Sequence Number



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   STRIDE       Addresses risk and severity associated with threat
   categories: Spoofing identity, Tampering with data, Repudiation,
   Information disclosure, Denial of service, Elevation of privilege.

   DREAD       Compares and prioritizes risk represented by these threat
   categories: Damage potential, Reproducibility, Exploitability, how
   many Affected users, Discoverability.

   PTP         Precision Time Protocol [IEEE1588]

3.  Security Threats

   This section presents a threat model, and analyzes the possible
   threats in a DetNet-enabled network.

   We distinguish control plane threats from data plane threats.  The
   attack surface may be the same, but the types of attacks are
   different.  For example, a delay attack is more relevant to data
   plane than to control plane.  There is also a difference in terms of
   security solutions: the way you secure the data plane is often
   different than the way you secure the control plane.

3.1.  Threat Model

   The threat model used in this memo is based on the threat model of
   Section 3.1 of [RFC7384].  This model classifies attackers based on
   two criteria:

   o  Internal vs. external: internal attackers either have access to a
      trusted segment of the network or possess the encryption or
      authentication keys.  External attackers, on the other hand, do
      not have the keys and have access only to the encrypted or
      authenticated traffic.

   o  Man in the Middle (MITM) vs. packet injector: MITM attackers are
      located in a position that allows interception and modification of
      in-flight protocol packets, whereas a traffic injector can only
      attack by generating protocol packets.

   DetNet-Service, one of the service scenarios described in
   [I-D.varga-detnet-service-model], is the case where a service
   connects DetNet networking islands, i.e. two or more otherwise
   independent DetNet network domains are connected via a link that is
   not intrinsically part of either network.  This implies that there
   could be DetNet traffic flowing over a non-DetNet link, which may
   provide an attacker with an advantageous opportunity to tamper with
   DetNet traffic.  The security properties of non-DetNet links are
   outside of the scope of DetNet Security, but it should be noted that



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   use of non-DetNet services to interconnect DetNet networks merits
   security analysis to ensure the integrity of the DetNet networks
   involved.

3.2.  Threat Analysis

3.2.1.  Delay

3.2.1.1.  Delay Attack

   An attacker can maliciously delay DetNet data flow traffic.  By
   delaying the traffic, the attacker can compromise the service of
   applications that are sensitive to high delays or to high delay
   variation.

3.2.2.  DetNet Flow Identification

3.2.2.1.  DetNet Flow Modification or Spoofing

   An attacker can modify some header fields of en route packets in a
   way that causes the DetNet flow identification mechanisms to
   misclassify the flow.  Alternatively, the attacker can inject traffic
   that is tailored to appear as if it belongs to a legitimate DetNet
   flow.  The potential consequence is that the DetNet flow resource
   allocation cannot guarantee the performance that is expected when the
   flow identification works correctly.

   Note that in some cases there may be an explicit DetNet header, but
   in some cases the flow identification may be based on fields from the
   L3/L4 headers.  If L3/L4 headers are involved, for purposes of this
   draft we assume they are encrypted and/or integrity-protected from
   external attackers.

3.2.3.  Resource Segmentation or Slicing

3.2.3.1.  Inter-segment Attack

   An attacker can inject traffic, consuming network device resources,
   thereby affecting DetNet flows.  This can be performed using non-
   DetNet traffic that affects DetNet traffic, or by using DetNet
   traffic from one DetNet flow that affects traffic from different
   DetNet flows.

3.2.4.  Packet Replication and Elimination







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3.2.4.1.  Replication: Increased Attack Surface

   Redundancy is intended to increase the robustness and survivability
   of DetNet flows, and replication over multiple paths can potentially
   mitigate an attack that is limited to a single path.  However, the
   fact that packets are replicated over multiple paths increases the
   attack surface of the network, i.e., there are more points in the
   network that may be subject to attacks.

3.2.4.2.  Replication-related Header Manipulation

   An attacker can manipulate the replication-related header fields
   (R-TAG).  This capability opens the door for various types of
   attacks.  For example:

   o  Forward both replicas - malicious change of a packet SN (Sequence
      Number) can cause both replicas of the packet to be forwarded.
      Note that this attack has a similar outcome to a replay attack.

   o  Eliminate both replicas - SN manipulation can be used to cause
      both replicas to be eliminated.  In this case an attacker that has
      access to a single path can cause packets from other paths to be
      dropped, thus compromising some of the advantage of path
      redundancy.

   o  Flow hijacking - an attacker can hijack a DetNet flow with access
      to a single path by systematically replacing the SNs on the given
      path with higher SN values.  For example, an attacker can replace
      every SN value S with a higher value S+C, where C is a constant
      integer.  Thus, the attacker creates a false illusion that the
      attacked path has the lowest delay, causing all packets from other
      paths to be eliminated.  Once the flow is hijacked the attacker
      can either replace en route packets with malicious packets, or
      simply injecting errors, causing the packets to be dropped at
      their destination.

3.2.5.  Path Choice

3.2.5.1.  Path Manipulation

   An attacker can maliciously change, add, or remove a path, thereby
   affecting the corresponding DetNet flows that use the path.

3.2.5.2.  Path Choice: Increased Attack Surface

   One of the possible consequences of a path manipulation attack is an
   increased attack surface.  Thus, when the attack described in the




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   previous subsection is implemented, it may increase the potential of
   other attacks to be performed.

3.2.6.  Control Plane

3.2.6.1.  Control or Signaling Packet Modification

   An attacker can maliciously modify en route control packets in order
   to disrupt or manipulate the DetNet path/resource allocation.

3.2.6.2.  Control or Signaling Packet Injection

   An attacker can maliciously inject control packets in order to
   disrupt or manipulate the DetNet path/resource allocation.

3.2.7.  Scheduling or Shaping

3.2.7.1.  Reconnaissance

   A passive eavesdropper can gather information about en route DetNet
   flows, e.g., the number of DetNet flows, their bandwidths, and their
   schedules.  The gathered information can later be used to invoke
   other attacks on some or all of the flows.

3.2.8.  Time Synchronization Mechanisms

   An attacker can use any of the attacks described in [RFC7384] to
   attack the synchronization protocol, thus affecting the DetNet
   service.

3.3.  Threat Summary

   A summary of the attacks that were discussed in this section is
   presented in Figure 1.  For each attack, the table specifies the type
   of attackers that may invoke the attack.  In the context of this
   summary, the distinction between internal and external attacks is
   under the assumption that a corresponding security mechanism is being
   used, and that the corresponding network equipment takes part in this
   mechanism.












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   +-----------------------------------------+----+----+----+----+
   | Attack                                  |   Attacker Type   |
   |                                         +---------+---------+
   |                                         |Internal |External |
   |                                         |MITM|Inj.|MITM|Inj.|
   +-----------------------------------------+----+----+----+----+
   |Delay attack                             | +  |    | +  |    |
   +-----------------------------------------+----+----+----+----+
   |DetNet Flow Modification or Spoofing     | +  | +  |    |    |
   +-----------------------------------------+----+----+----+----+
   |Inter-segment Attack                     | +  | +  |    |    |
   +-----------------------------------------+----+----+----+----+
   |Replication: Increased Attack Surface    | +  | +  | +  | +  |
   +-----------------------------------------+----+----+----+----+
   |Replication-related Header Manipulation  | +  |    |    |    |
   +-----------------------------------------+----+----+----+----+
   |Path Manipulation                        | +  | +  |    |    |
   +-----------------------------------------+----+----+----+----+
   |Path Choice: Increased Attack Surface    | +  | +  | +  | +  |
   +-----------------------------------------+----+----+----+----+
   |Control or Signaling Packet Modification | +  |    |    |    |
   +-----------------------------------------+----+----+----+----+
   |Control or Signaling Packet Injection    |    | +  |    |    |
   +-----------------------------------------+----+----+----+----+
   |Reconnaissance                           | +  |    | +  |    |
   +-----------------------------------------+----+----+----+----+
   |Attacks on Time Sync Mechanisms          | +  | +  | +  | +  |
   +-----------------------------------------+----+----+----+----+

                     Figure 1: Threat Analysis Summary

4.  Security Threat Impacts

   This section describes the impact of the attacks described in
   Section 3.  Mitigations are discussed further in Section 5.

   In computer security, the impact (or consequence) of an incident can
   be measured in loss of confidentiality, integrity or availability of
   information.  In other words, this section describes the effect of a
   successful attack.  The scope is limited to the effect of a
   successful attack on DetNet itself, not the applications that _use_
   Detnet as this is highly application specific.

4.1.  Delay-Attacks







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4.1.1.  Data Plane Delay Attacks

   Dropped messages can result in stream instability.  If only a single
   path is used, the entire stream can be disrupted.  In a multipath
   scenario, large delays on one stream can lead to increased buffer and
   CPU resources on the elimination bridge.

   If the attack is carried out on a sole link (i.e. no multipath), the
   DetNet stream can be interrupted and result in outages.

4.1.2.  Control Plane Delay Attacks

   In and of itself, this is not directly a threat, the effects of
   delaying control messages can have quite adverse effects later.

   Delayed messages for tear-down can lead to resource leakage if a
   stream is not torn down at the correct time.  This can in turn result
   in failure to allocate new streams giving rise to a denial of service
   attack.

   In the case where an End-point should be added to a multicast,
   failure to deliver said signalling message will prevent the new EP
   from receiving expected frames.

   Likewise, when an EP should be removed from a multicast group,
   delaying such messages can lead to loss of privacy as the EP will
   continue to receive messages even after it is removed.

4.2.  Flow Identification and Spoofing

4.2.1.  Flow identification

   Of all the attacks, this is one of the most difficult to detect and
   counter.  Often, an attacker will start out by observing the traffic
   going through the network and use the knowledge gathered in this
   phase to mount future attacks.

   The attacker can, at their leisure, observe over time all aspects of
   the messaging and signalling, learning the intent and purpose of all
   traffic flows.  At some later date, possibly at an important time in
   an operational context, the attacker can launch a multi-faceted
   attack, possibly in conjunction with some demand for ransom.

   The flow-id in the header of the data plane-messages gives an
   attacker a very reliable identifier for DetNet traffic, and this
   traffic has a high probability of going to lucrative targets.





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4.2.2.  Spoofing

4.2.2.1.  Dataplane Spoofing

   Spoofing dataplane messages can result in increased resource
   consumptions on the bridges throughout the network as it will
   increase buffer usage and CPU utilization.  This can lead to resource
   exhaustion and/or increased delay.

   If the attacker manages to create valid headers, the false messages
   can be forwarded through the network, using part of the allocated
   bandwidth.  This in turn can cause legitimate messages to be dropped
   when the budget has been exhausted.

   Finally, the endpoint will have to deal with invalid messages being
   delivered to the endpoint instead of (or in addition to) a valid
   message.

4.2.2.2.  Control Plane Spoofing

   A successful control plane spoofing-attack has a very large
   potential.  It can do anything from modifying existing streams by
   changing the available bandwidth, add or remove endpoints or drop the
   stream altogether.  It would also be possible to falsely create new
   streams, which could give an attacker the ability to exhaust the
   systems resources, or just enable a high quality DetNet stream
   outside the Network engineer's control.

4.3.  Segmentation attacks (injection)

4.3.1.  Data Plane Segmentation

   Injection of false messages in a DetNet stream could lead to
   exhaustion of the available bandwidth for a stream if the bridges
   accounts false messages to the stream's budget.

   In a multipath scenario, injected messages will cause an increased
   CPU utilization on elimination bridges and if enough paths are
   subject to malicious injection, the legitimate messages could be
   dropped.  Likewise it can cause an increase in buffer usage.  In
   total, this will consume more resources on the bridges than normal,
   giving rise to a potential resource exhaustion attack on the bridges.

   If a stream is interrupted, the end application will be affected by
   what is now a non-deterministic stream.






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4.3.2.  Control Plane segmentation

   A successful Control Plane segmentation attack will cause control
   messages to be interpreted by nodes in the network.  This has the
   potential to create new streams (exhausting resources), drop existing
   (denial of service), add/remove end-stations to a multicast group
   (loss of privacy) or modify the stream attributes (reducing available
   bandwidth, or increasing it so that new streams cannot reserve a
   path).

   In short, this means that you cannot trust the stream reservation
   properties or the network itself.

   As with spoofing, if an attacker is able to inject control-plane
   messages and the receiving end does not detect it, the receiving
   station must be able to.

4.4.  Replication and Elimination

   The Replication and Elimination is relevant only to Data Plane
   messages as Signalling is not subject to multipath routing.

4.4.1.  Increased Attack Surface

   Covered briefly in Section 4.3

4.4.2.  Header Manipulation at Elimination Bridges

   Covered briefly in Section 4.3

4.5.  Impact of Attacks to Path Choice

   This is covered in part in Section 4.3, and as with Replication and
   Elimination (Section 4.4, this is relevant for DataPlane messages.

4.6.  Impact of Attacks by Use Case Industry

   This section rates the severity of various components of the impact
   of a successful vulnerability exploit to use cases by industry as
   described in [I-D.ietf-detnet-use-cases], including Pro Audio,
   Electrical Utilities, Building Automation, Wireless for Industrial,
   Cellular Radio, and Industrial M2M (split into two areas, M2M Data
   Gathering and M2M Control Loop).

   Components of Impact (left column) include Criticality of Failure,
   Effects of Failure, Recovery, and DetNet Functional Dependence.
   Criticality of failure summarizes the seriousness of the impact.  The
   impact of a resulting failure can affect many different metrics that



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   vary greatly in scope and severity.  In order to reduce the number of
   variables, the following were included: Financial, Health and Safety,
   People well being, Affect on a single organization, and affect on
   multiple organizations.  Recovery outlines how long it would take for
   an affected use case to get back to its pre-failure state (Recovery
   time objective, RTO), and how much of the original service would be
   lost in between the time of service failure and recovery to original
   state (Recovery Point Objective, RPO).  DetNET dependence maps how
   much the following DetNet service objectives contribute to impact of
   failure: Time dependency, data integrity, source node integrity,
   availability, latency/jitter.

   The scale of the Impact mappings is low, medium, and high.  In some
   use cases there may be a multitude of specific applications in which
   DetNET is used.  For simplicity this section attempts to average the
   varied impacts of different applications.  This section does not
   address the overall risk of a certain impact which would require the
   likelihood of a failure happening.

   In practice any such ratings will vary from case to case; the ratings
   shown here are given as examples.






























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   +------------------+-----------------------------------------+-----+
   |                  | Pro A | Util | Bldg |Wire- | Cell |M2M  |M2M  |
   |                  |       |      |      | less |      |Data |Ctrl |
   +------------------+-----------------------------------------+-----+
   | Criticality      | Med   | Hi   | Low  | Med  | Med  | Med | Med |
   +------------------+-----------------------------------------+-----+
   | Effects
   +------------------+-----------------------------------------+-----+
   |  Financial       | Med   | Hi   | Med  | Med  | Low  | Med | Med |
   +------------------+-----------------------------------------+-----+
   |  Health/Safety   | Med   | Hi   | Hi   | Med  | Med  | Med | Med |
   +------------------+-----------------------------------------+-----+
   |  People WB       | Med   | Hi   | Hi   | Low  | Hi   | Low | Low |
   +------------------+-----------------------------------------+-----+
   |  Effect 1 org    | Hi    | Hi   | Med  | Hi   | Med  | Med | Med |
   +------------------+-----------------------------------------+-----+
   |  Effect >1 org   | Med   | Hi   | Low  | Med  | Med  | Med | Med |
   +------------------+-----------------------------------------+-----+
   |Recovery
   +------------------+-----------------------------------------+-----+
   |  Recov Time Obj  | Med   | Hi   | Med  | Hi   | Hi   | Hi  | Hi  |
   +------------------+-----------------------------------------+-----+
   |  Recov Point Obj | Med   | Hi   | Low  | Med  | Low  | Hi  | Hi  |
   +------------------+-----------------------------------------+-----+
   |DetNet Dependence
   +------------------+-----------------------------------------+-----+
   |  Time Dependency | Hi    | Hi   | Low  | Hi   | Med  | Low | Hi  |
   +------------------+-----------------------------------------+-----+
   |  Latency/Jitter  | Hi    | Hi   | Med  | Med  | Low  | Low | Hi  |
   +------------------+-----------------------------------------+-----+
   |  Data Integrity  | Hi    | Hi   | Med  | Hi   | Low  | Hi  | Low |
   +------------------+-----------------------------------------+-----+
   |  Src Node Integ  | Hi    | Hi   | Med  | Hi   | Med  | Hi  | Hi  |
   +------------------+-----------------------------------------+-----+
   |  Availability    | Hi    | Hi   | Med  | Hi   | Low  | Hi  | Hi  |
   +------------------+-----------------------------------------+-----+

             Figure 2: Impact of Attacks by Use Case Industry

5.  Security Threat Mitigation

   This section describes a set of measures that can be taken to
   mitigate the attacks described in Section 3.  These mitigations
   should be viewed as a toolset that includes several different and
   diverse tools.  Each application or system will typically use a
   subset of these tools, based on a system-specific threat analysis.





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5.1.  Path Redundancy

   Description

      A DetNet flow that can be forwarded simultaneously over multiple
      paths.  Path replication and elimination
      [I-D.ietf-detnet-architecture] provides resiliency to dropped or
      delayed packets.  This redundancy improves the robustness to
      failures and to man-in-the-middle attacks.

   Related attacks

      Path redundancy can be used to mitigate various man-in-the-middle
      attacks, including attacks described in Section 3.2.1,
      Section 3.2.2, Section 3.2.3, and Section 3.2.8.

5.2.  Integrity Protection

   Description

      An integrity protection mechanism, such as a Hash-based Message
      Authentication Code (HMAC) can be used to mitigate modification
      attacks.  Integrity protection can be used on the data plane
      header, to prevent its modification and tampering.  Integrity
      protection in the control plane is discussed in Section 5.5.

   Related attacks

      Integrity protection mitigates attacks related to modification and
      tampering, including the attacks described in Section 3.2.2 and
      Section 3.2.4.

5.3.  DetNet Node Authentication

   Description

      Source authentication verifies the authenticity of DetNet sources,
      allowing to mitigate spoofing attacks.  Note that while integrity
      protection (Section 5.2) prevents intermediate nodes from
      modifying information, authentication verfies the source of the
      information.

   Related attacks

      DetNet node authentication is used to mitigate attacks related to
      spoofing, including the attacks of Section 3.2.2, and
      Section 3.2.4.




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5.4.  Encryption

   Description

      DetNet flows can be forwarded in encrypted form.

   Related attacks

      While confidentiality is not considered an important goal with
      respect to DetNet, encryption can be used to mitigate recon
      attacks (Section 3.2.7).

5.5.  Control and Signaling Message Protection

   Description

      Control and sigaling messages can be protected using
      authentication and integrity protection mechanisms.

   Related attacks

      These mechanisms can be used to mitigate various attacks on the
      control plane, as described in Section 3.2.6, Section 3.2.8 and
      Section 3.2.5.

5.6.  Dynamic Performance Analytics

   Description

      Information about the network performance can be gathered in real-
      time in order to detect anomalies and unusual behavior that may be
      the symptom of a security attack.  The gathered information can be
      based, for example, on per-flow counters, bandwidth measurement,
      and monitoring of packet arrival times.  Unusual behavior or
      potentially malicious nodes can be reported to a management
      system, or can be used as a trigger for taking corrective actions.
      The information can be tracked by DetNet end systems and transit
      nodes, and exported to a management system, for example using
      NETCONF.

   Related attacks

      Performance analytics can be used to mitigate various attacks,
      including the ones described in Section 3.2.1, Section 3.2.3, and
      Section 3.2.8.






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5.7.  Mitigation Summary

   The following table maps the attacks of Section 3 to the impacts of
   Section 4, and to the mitigations of the current section.  Each row
   specifies an attack, the impact of this attack if it is successfully
   implemented, and possible mitigation methods.


   +----------------------+---------------------+---------------------+
   | Attack               |      Impact         |     Mitigations     |
   +----------------------+---------------------+---------------------+
   |Delay Attack          |-Non-deterministic   |-Path redundancy     |
   |                      | delay               |-Performance         |
   |                      |-Data disruption     | analytics           |
   |                      |-Increased resource  |                     |
   |                      | consumption         |                     |
   +----------------------+---------------------+---------------------+
   |DetNet Flow Modificat-|-Increased resource  |-Path redundancy     |
   |ion or Spoofing       | consumption         |-Integrity protection|
   |                      |-Data disruption     |-DetNet Node         |
   |                      |                     | authentication      |
   +----------------------+---------------------+---------------------+
   |Inter-Segment Attack  |-Increased resource  |-Path redundancy     |
   |                      | consumption         |-Performance         |
   |                      |-Data disruption     | analytics           |
   +----------------------+---------------------+---------------------+
   |Replication: Increased|-All impacts of other|-Integrity protection|
   |attack surface        | attacks             |-DetNet Node         |
   |                      |                     | authentication      |
   +----------------------+---------------------+---------------------+
   |Replication-related   |-Non-deterministic   |-Integrity protection|
   |Header Manipulation   | delay               |-DetNet Node         |
   |                      |-Data disruption     | authentication      |
   +----------------------+---------------------+---------------------+
   |Path Manipulation     |-Enabler for other   |-Control message     |
   |                      | attacks             | protection          |
   +----------------------+---------------------+---------------------+
   |Path Choice: Increased|-All impacts of other|-Control message     |
   |Attack Surface        | attacks             | protection          |
   +----------------------+---------------------+---------------------+
   |Control or Signaling  |-Increased resource  |-Control message     |
   |Packet Modification   | consumption         | protection          |
   |                      |-Non-deterministic   |                     |
   |                      | delay               |                     |
   |                      |-Data disruption     |                     |
   +----------------------+---------------------+---------------------+
   |Control or Signaling  |-Increased resource  |-Control message     |
   |Packet Injection      | consumption         | protection          |



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   |                      |-Non-deterministic   |                     |
   |                      | delay               |                     |
   |                      |-Data disruption     |                     |
   +----------------------+---------------------+---------------------+
   |Reconnaissance        |-Enabler for other   |-Encryption          |
   |                      | attacks             |                     |
   +----------------------+---------------------+---------------------+
   |Attacks on Time Sync  |-Non-deterministic   |-Path redundancy     |
   |Mechanisms            | delay               |-Control message     |
   |                      |-Increased resource  | protection          |
   |                      | consumption         |-Performance         |
   |                      |-Data disruption     | analytics           |
   +----------------------+---------------------+---------------------+

            Figure 3: Mapping Attacks to Impact and Mitigations

6.  Association of Attacks to Use Cases

6.1.  Use Cases by Common Themes

   Different attacks can have different impact and/or mitigation
   depending on the use case, so we would like to make this association
   in our analysis.  However since there is a potentially unbounded list
   of use cases, we categorize the attacks with respect to the common
   themes of the use cases as identified in the Use Case Common Themes
   section of the DetNet Use Cases draft [I-D.ietf-detnet-use-cases].
   We describe each theme and its associated attacks, impacts and
   mitigations.

6.1.1.  Network Layer - AVB/TSN Ethernet

   Presumably it will be possible to run DetNet over other underlying
   network layers besides Ethernet, but Ethernet is explicitly
   supported.  Is the attack specific to the Ethernet AVB/TSN protocols?
   Does the threat affect only Ethernet, or any underlying network
   layer?

6.1.2.  Central Administration

   A DetNet network is expected to be controlled by a centralized
   network configuration and control system.  Such a system may be in a
   single central location, or it may be distributed across multiple
   control entities that function together as a unified control system
   for the network.  Is the attack directed at threat the central
   control system of the network?  Does it interfere with OAM?






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6.1.3.  Hot Swap

   A DetNet network is not expected to be "plug and play" - it is
   expected that there is some centralized network configuration and
   control system.  However, the ability to "hot swap" components (e.g.
   due to malfunction) is similar enough to "plug and play" that this
   kind of behavior may be expected in DetNet networks, depending on the
   implementation.  Does the attack target "hot swap" ("plug and play")
   operation in the network?

6.1.4.  Data Flow Information Models

   Data Flow Information Models specific to DetNet networks are to be
   specified by DetNet.  Thus they are "new" and thus potentially
   present a new attack surface.  Does the threat take advantage of any
   aspect of our new Data Flow Info Models?

6.1.5.  L2 and L3 Integration

   A DetNet network is intended to integrate between Layer 2 (bridged)
   network(s) (e.g.  AVB/TSN LAN) and Layer 3 (routed) network(s) (e.g.
   using IP-based protocols).  Does the attack target L2?  L3?  Both?
   The interaction between the two?

6.1.6.  End-to-End Delivery

   Packets sent over DetNet are guaranteed not to be dropped by the
   network due to congestion.  (Packets may however be dropped for
   intended reasons, e.g. per security measures).  Does the attack
   result in packets (which should be delivered) not being delivered?
   Does it result in packets that should not be delivered being
   delivered?

6.1.7.  Proprietary Deterministic Ethernet Networks

   There are many proprietary non-interoperable deterministic Ethernet-
   based networks currently available; DetNet is intended to provide an
   open-standards-based alternative to such networks.  Does the threat
   relate to a specific such network that is being "emulated" or
   "replaced" by DetNet, for example by exploiting specific commands
   specific to that network protocol?

6.1.8.  Replacement for Proprietary Fieldbuses

   There are many proprietary "field buses" used in today's industrial
   and other industries; DetNet is intended to provide an open-
   standards-based alternative to such buses.  Does the threat relate to
   a specific fieldbus that is being "emulated" or "replaced" by DetNet,



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   for example by exploiting specific commands specific to that network
   protocol?

6.1.9.  Deterministic vs Best-Effort Traffic

   DetNet is intended to support coexistence of time-sensitive
   operational (OT, deterministic) traffic and information (IT, "best
   effort") traffic on the same ("unified") network.  Does the attack
   affect only IT or only OT or both types of traffic?  Does the threat
   affect any interaction between IT and OT traffic, e.g. by changing
   relative priority or handling of IT vs. OT packets?

6.1.10.  Deterministic Flows

   Reserved bandwidth data flows (deterministic flows) must be isolated
   from each other and from best-effort traffic, so that even if the
   network is saturated with best-effort and/or reserved bandwidth
   traffic the configured flows are not adversely affected.  Does the
   attack affect the isolation of one (reserved) flow from another?

6.1.11.  Unused Reserved Bandwidth

   If bandwidth reservations are made for a stream but the associated
   bandwidth is not used at any point in time, that bandwidth is made
   available on the network for best-effort traffic.  If the owner of
   the reserved stream then starts transmitting again, the bandwidth is
   no longer available for best-effort traffic, on a moment-to-moment
   basis.  (Such "temporarily available" bandwidth is not available for
   time-sensitive traffic, which must have its own reservation).  Does
   the attack affect the system's ability to allocate unused reserved BW
   to best-effort traffic?

6.1.12.  Interoperability

   The DetNet network specifications are intended to enable an ecosystem
   in which multiple vendors can create interoperable products, thus
   promoting device diversity and potentially higher numbers of each
   device manufactured.  Does the threat take advantage of differences
   in implementation of "interoperable" products made by different
   vendors?

6.1.13.  Cost Reductions

   The DetNet network specifications are intended to enable an ecosystem
   in which multiple vendors can create interoperable products, thus
   promoting higher numbers of each device manufactured, promoting cost
   reduction and cost competition among vendors.  Does the threat take




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   advantage of "low cost" HW or SW components or other "cost-related
   shortcuts" that might be present in devices?

6.1.14.  Insufficiently Secure Devices

   The DetNet network specifications are intended to enable an ecosystem
   in which multiple vendors can create interoperable products, thus
   promoting device diversity and potentially higher numbers of each
   device manufactured.  Does the threat attack "naivete" of SW, for
   example SW that was not designed to be sufficiently secure (or secure
   at all) but is deployed on a DetNet network that is intended to be
   highly secure?  (For example IoT exploits like the Mirai video-camera
   botnet ([MIRAI]).

6.1.15.  DetNet Network Size

   DetNet networks range in size from very small, e.g. inside a single
   industrial machine, to very large, for example a Utility Grid network
   spanning a whole country, and involving many "hops" over various
   kinds of links for example radio repeaters, microwave links, fiber
   optic links, etc.. Does the attack affect DetNet networks of only
   certain sizes, e.g. very large networks, or very small?  This might
   be related to how the attack is introduced into the network, for
   example if the entire network is local, there is a threat that power
   can be cut to the entire network.  If the network is large, perhaps
   only a part of the network is attacked.  Does the threat take
   advantage of attack vectors that are specific to network size?

6.1.16.  Multiple Hops

   DetNet networks range in size from very small, e.g. inside a single
   industrial machine, to very large, for example a Utility Grid network
   spanning a whole country, and involving many "hops" over various
   kinds of links for example radio repeaters, microwave links, fiber
   optic links, etc.. Does the attack exploit the presence of more than
   one "hop"?  Does the threat exploit the presence of more than one
   type of "hop", e.g. between radio and microwave links?  Does the
   threat exploit a specific type of "hop", e.g.  something specific to
   a fiber optic link, or other type of link?

6.1.17.  Level of Service

   A DetNet is expected to provide means to configure the network that
   include querying network path latency, requesting bounded latency for
   a given stream, requesting worst case maximum and/or minimum latency
   for a given path or stream, and so on.  It is an expected case that
   the network cannot provide a given requested service level.  In such
   cases the network control system should reply that the requested



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   service level is not available (as opposed to accepting the parameter
   but then not delivering the desired behavior).  Does the attack
   affect any querying or replying to such service-level-related
   traffic?  Can the attack cause incorrect responses from the system
   regarding timing-related configuration?  For example replying that a
   requested level of service is available when it isn't, or that the
   requested level of service is not available when it actually is
   available?

6.1.18.  Bounded Latency

   Does the threat affect the network's ability to deliver packets
   within the agreed-upon latency boundaries?

6.1.19.  Low Latency

   Applications may require "extremely low latency" however depending on
   the application these may mean very different latency values; for
   example "low latency" across a Utility grid network is on a different
   time scale than "low latency" in a motor control loop in a small
   machine.  The intent is that the mechanisms for specifying desired
   latency include wide ranges, and that architecturally there is
   nothing to prevent arbitrarily low latencies from being implemented
   in a given network.  Does the threat affect the network's ability to
   deliver packets within the agreed-upon low latency?

6.1.20.  Symmetrical Path Delays

   Some applications would like to specify that the transit delay time
   values be equal for both the transmit and return paths.  Does the
   attack affect the network's ability to provide matched transmit and
   return path delays (latencies)?

6.1.21.  Reliability and Availability

   DetNet based systems are expected to be implemented with essentially
   arbitrarily high availability (for example 99.9999% up time, or even
   12 nines).  The intent is that the DetNet designs should not make any
   assumptions about the level of reliability and availability that may
   be required of a given system, and should define parameters for
   communicating these kinds of metrics within the network.  Does the
   attack affect the reliability of the DetNet network?  Is it a large
   or small change, e.g. the difference between completely taking down
   the network for some period of time, vs reducing its reliability by
   just one "nine"?  Does the threat affect the availability of the
   DetNet network?





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6.1.22.  Redundant Paths

   DetNet based systems are expected to be implemented with essentially
   arbitrarily high reliability/availability.  A strategy used by DetNet
   for providing such extraordinarily high levels of reliability is to
   provide redundant paths that can be seamlessly switched between, all
   the while maintaining the required performance of that system.  Does
   the attack affect the configuration or operation of redundant paths?

6.1.23.  Security Measures

   A DetNet network must be made secure against devices failures,
   attackers, misbehaving devices, and so on.  Does the threat affect
   such security measures themselves, e.g. by attacking SW designed to
   protect against device failure?

6.2.  Attack Types by Use Case Common Theme

   The following table lists the attacks of Section 3, assigning a
   number to each type of attack.  That number is then used as a short
   form identifier for the attack in Figure 5.






























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   +--+----------------------------------------+----------------------+
   |  | Attack                                 |       Section        |
   +--+----------------------------------------+----------------------+
   | 1|Delay Attack                            |  Section 3.2.1       |
   +--+----------------------------------------+----------------------+
   | 2|DetNet Flow Modification or Spoofing    |  Section 3.2.2       |
   +--+----------------------------------------+----------------------+
   | 3|Inter-Segment Attack                    |  Section 3.2.3       |
   +--+----------------------------------------+----------------------+
   | 4|Replication: Increased attack surface   |  Section 3.2.4.1     |
   +--+----------------------------------------+----------------------+
   | 5|Replication-related Header Manipulation |  Section 3.2.4.2     |
   +--+----------------------------------------+----------------------+
   | 6|Path Manipulation                       |  Section 3.2.5.1     |
   +--+----------------------------------------+----------------------+
   | 7|Path Choice: Increased Attack Surface   |  Section 3.2.5.2     |
   +--+----------------------------------------+----------------------+
   | 8|Control or Signaling Packet Modification|  Section 3.2.6.1     |
   +--+----------------------------------------+----------------------+
   | 9|Control or Signaling Packet Injection   |  Section 3.2.6.2     |
   +--+----------------------------------------+----------------------+
   |10|Reconnaissance                          |  Section 3.2.7       |
   +--+----------------------------------------+----------------------+
   |11|Attacks on Time Sync Mechanisms         |  Section 3.2.8       |
   +--+----------------------------------------+----------------------+

                         Figure 4: List of Attacks

   The following table maps the use case themes presented in this memo
   to the attacks of Figure 4.  Each row specifies a theme, and the
   attacks relevant to this theme are marked with a '+'.


   +----------------------------+--------------------------------+
   | Theme                      |             Attack             |
   |                            +--+--+--+--+--+--+--+--+--+--+--+
   |                            | 1| 2| 3| 4| 5| 6| 7| 8| 9|10|11|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Network Layer - AVB/TSN Eth.| +| +| +| +| +| +| +| +| +| +| +|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Central Administration      |  |  |  |  |  | +| +| +| +| +| +|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Hot Swap                    |  | +| +|  |  |  |  |  |  |  | +|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Data Flow Information Models|  |  |  |  |  |  |  |  |  |  |  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |L2 and L3 Integration       |  |  |  |  | +| +|  |  |  |  |  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+



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   |End-to-end Delivery         |  |  |  | +| +|  |  |  |  |  |  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Proprietary Deterministic   |  |  | +|  |  | +| +| +| +|  |  |
   |Ethernet Networks           |  |  |  |  |  |  |  |  |  |  |  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Replacement for Proprietary |  |  | +|  |  | +| +| +| +|  |  |
   |Fieldbuses                  |  |  |  |  |  |  |  |  |  |  |  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Deterministic vs. Best-     |  |  | +|  |  |  |  |  |  |  |  |
   |Effort Traffic              |  |  |  |  |  |  |  |  |  |  |  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Deterministic Flows         |  |  | +|  |  |  |  |  |  |  |  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Unused Reserved Bandwidth   |  |  | +|  |  |  |  |  |  |  |  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Interoperability            |  |  |  |  |  |  |  |  |  |  |  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Cost Reductions             |  |  |  |  |  |  |  |  |  |  |  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Insufficiently Secure       |  |  |  |  |  |  |  |  |  |  |  |
   |Devices                     |  |  |  |  |  |  |  |  |  |  |  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |DetNet Network Size         | +|  |  |  |  | +| +|  |  |  | +|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Multiple Hops               | +| +|  |  |  | +| +|  |  |  | +|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Level of Service            |  |  |  |  |  |  |  | +| +| +|  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Bounded Latency             | +|  |  |  |  |  |  |  |  |  | +|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Low Latency                 | +|  |  |  |  |  |  |  |  |  | +|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Symmetric Path Delays       | +|  |  |  |  |  |  |  |  |  | +|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Reliability and Availability| +| +| +| +| +| +| +| +| +| +| +|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Redundant Paths             |  |  |  | +| +|  |  | +| +|  |  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Security Measures           |  |  |  |  |  |  |  |  |  |  |  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+

               Figure 5: Mapping Between Themes and Attacks

7.  Appendix A: DetNet Draft Security-Related Statements

   This section collects the various statements in the currently
   existing DetNet Working Group drafts.  For each draft, the section
   name and number of the quoted section is shown.  The text shown here



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   is the work of the original draft authors, quoted verbatim from the
   drafts.  The intention is to explicitly quote all relevant text, not
   to summarize it.

7.1.  Architecture (draft 8)

7.1.1.  Fault Mitigation (sec 4.5)

   One key to building robust real-time systems is to reduce the
   infinite variety of possible failures to a number that can be
   analyzed with reasonable confidence.  DetNet aids in the process by
   providing filters and policers to detect DetNet packets received on
   the wrong interface, or at the wrong time, or in too great a volume,
   and to then take actions such as discarding the offending packet,
   shutting down the offending DetNet flow, or shutting down the
   offending interface.

   It is also essential that filters and service remarking be employed
   at the network edge to prevent non-DetNet packets from being mistaken
   for DetNet packets, and thus impinging on the resources allocated to
   DetNet packets.

   There exist techniques, at present and/or in various stages of
   standardization, that can perform these fault mitigation tasks that
   deliver a high probability that misbehaving systems will have zero
   impact on well-behaved DetNet flows, except of course, for the
   receiving interface(s) immediately downstream of the misbehaving
   device.  Examples of such techniques include traffic policing
   functions (e.g.  [RFC2475]) and separating flows into per-flow rate-
   limited queues.

7.1.2.  Security Considerations (sec 7)

   Security in the context of Deterministic Networking has an added
   dimension; the time of delivery of a packet can be just as important
   as the contents of the packet, itself.  A man-in-the-middle attack,
   for example, can impose, and then systematically adjust, additional
   delays into a link, and thus disrupt or subvert a real-time
   application without having to crack any encryption methods employed.
   See [RFC7384] for an exploration of this issue in a related context.

   Furthermore, in a control system where millions of dollars of
   equipment, or even human lives, can be lost if the DetNet QoS is not
   delivered, one must consider not only simple equipment failures,
   where the box or wire instantly becomes perfectly silent, but bizarre
   errors such as can be caused by software failures.  Because there is
   essential no limit to the kinds of failures that can occur,
   protecting against realistic equipment failures is indistinguishable,



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   in most cases, from protecting against malicious behavior, whether
   accidental or intentional.

   Security must cover:

   o  Protection of the signaling protocol

   o  Authentication and authorization of the controlling nodes

   o  Identification and shaping of the flows

7.2.  Data Plane Alternatives (draft 4)

7.2.1.  Security Considerations (sec 7)

   This document does not add any new security considerations beyond
   what the referenced technologies already have.

7.3.  Problem Statement (draft 5)

7.3.1.  Security Considerations (sec 5)

   Security in the context of Deterministic Networking has an added
   dimension; the time of delivery of a packet can be just as important
   as the contents of the packet, itself.  A man-in-the-middle attack,
   for example, can impose, and then systematically adjust, additional
   delays into a link, and thus disrupt or subvert a real-time
   application without having to crack any encryption methods employed.
   See [RFC7384] for an exploration of this issue in a related context.

   Typical control networks today rely on complete physical isolation to
   prevent rogue access to network resources.  DetNet enables the
   virtualization of those networks over a converged IT/OT
   infrastructure.  Doing so, DetNet introduces an additional risk that
   flows interact and interfere with one another as they share physical
   resources such as Ethernet trunks and radio spectrum.  The
   requirement is that there is no possible data leak from and into a
   deterministic flow, and in a more general fashion there is no
   possible influence whatsoever from the outside on a deterministic
   flow.  The expectation is that physical resources are effectively
   associated with a given flow at a given point of time.  In that
   model, Time Sharing of physical resources becomes transparent to the
   individual flows which have no clue whether the resources are used by
   other flows at other times.

   Security must cover:

   o  Protection of the signaling protocol



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   o  Authentication and authorization of the controlling nodes

   o  Identification and shaping of the flows

   o  Isolation of flows from leakage and other influences from any
      activity sharing physical resources

7.4.  Use Cases (draft 11)

7.4.1.  (Utility Networks) Security Current Practices and Limitations
        (sec 3.2.1)

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

   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.






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   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
      DoS).

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

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

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

   o  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.

7.4.2.  (Utility Networks) Security Trends in Utility Networks (sec
        3.3.3)

   Although advanced telecommunications networks can assist in
   transforming the energy industry by playing a critical role in
   maintaining high levels of reliability, performance, and
   manageability, they also introduce the need for an integrated
   security infrastructure.  Many of the technologies being deployed to
   support smart grid projects such as smart meters and sensors can
   increase the vulnerability of the grid to attack.  Top security
   concerns for utilities migrating to an intelligent smart grid
   telecommunications platform center on the following trends:

   o  Integration of distributed energy resources

   o  Proliferation of digital devices to enable management, automation,
      protection, and control

   o  Regulatory mandates to comply with standards for critical
      infrastructure protection





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   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 is imperative to understand the
   various impacts of these new components under a variety of attack
   situations on the power grid.  Consequences of a cyber attack on the
   grid telecommunications network can be catastrophic.  This is why
   security for smart grid is not just an ad hoc feature or product,
   it's a complete framework integrating both physical and Cyber
   security requirements and covering the entire smart grid networks
   from generation to distribution.  Security has therefore become one
   of the main foundations of the utility telecom network architecture
   and must be considered at every layer with a defense-in-depth
   approach.  Migrating to IP based protocols is key to address these
   challenges for two reasons:




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

   o  IP is based on open standards, which allows interoperability
      between different vendors and products, driving down the costs
      associated with implementing security solutions in OT networks.

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

7.4.3.  (BAS) Security Considerations (sec 4.2.4)

   When BAS field networks were developed it was assumed that the field
   networks would always be physically isolated from external networks
   and therefore security was not a concern.  In today's world many BASs
   are managed remotely and are thus connected to shared IP networks and
   so security is definitely a concern, yet security features are not
   available in the majority of BAS field network deployments .

   The management network, being an IP-based network, has the protocols
   available to enable network security, but in practice many BAS
   systems do not implement even the available security features such as
   device authentication or encryption for data in transit.

7.4.4.  (6TiSCH) Security Considerations (sec 5.3.3)

   On top of the classical requirements for protection of control
   signaling, it must be noted that 6TiSCH networks operate on limited
   resources that can be depleted rapidly in a DoS attack on the system,
   for instance by placing a rogue device in the network, or by
   obtaining management control and setting up unexpected additional
   paths.

7.4.5.  (Cellular radio) Security Considerations (sec 6.1.5)

   Establishing time-sensitive streams in the network entails reserving
   networking resources for long periods of time.  It is important that
   these reservation requests be authenticated to prevent malicious
   reservation attempts from hostile nodes (or accidental
   misconfiguration).  This is particularly important in the case where
   the reservation requests span administrative domains.  Furthermore,
   the reservation information itself should be digitally signed to




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   reduce the risk of a legitimate node pushing a stale or hostile
   configuration into another networking node.

   Note: This is considered important for the security policy of the
   network, but does not affect the core DetNet architecture and design.

7.4.6.  (Industrial M2M) Communication Today (sec 7.2)

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

8.  IANA Considerations

   This memo includes no requests from IANA.

9.  Security Considerations

   The security considerations of DetNet networks are presented
   throughout this document.

10.  Informative References

   [ARINC664P7]
              ARINC, "ARINC 664 Aircraft Data Network, Part 7, Avionics
              Full-Duplex Switched Ethernet Network", 2009.

   [I-D.ietf-detnet-architecture]
              Finn, N., Thubert, P., Varga, B., and J. Farkas,
              "Deterministic Networking Architecture", draft-ietf-
              detnet-architecture-03 (work in progress), August 2017.

   [I-D.ietf-detnet-use-cases]
              Grossman, E., Gunther, C., Thubert, P., Wetterwald, P.,
              Raymond, J., Korhonen, J., Kaneko, Y., Das, S., Zha, Y.,
              Varga, B., Farkas, J., Goetz, F., Schmitt, J., Vilajosana,
              X., Mahmoodi, T., Spirou, S., and P. Vizarreta,
              "Deterministic Networking Use Cases", draft-ietf-detnet-
              use-cases-12 (work in progress), April 2017.

   [I-D.varga-detnet-service-model]
              Varga, B. and J. Farkas, "DetNet Service Model", draft-
              varga-detnet-service-model-02 (work in progress), May
              2017.





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   [IEEE1588]
              IEEE, "IEEE 1588 Standard for a Precision Clock
              Synchronization Protocol for Networked Measurement and
              Control Systems Version 2", 2008.

   [MIRAI]    krebsonsecurity.com, "https://krebsonsecurity.com/2016/10/
              hacked-cameras-dvrs-powered-todays-massive-internet-
              outage/", 2016.

   [RFC7384]  Mizrahi, T., "Security Requirements of Time Protocols in
              Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384,
              October 2014, <https://www.rfc-editor.org/info/rfc7384>.

Authors' Addresses

   Tal Mizrahi
   Marvell

   Email: talmi@marvell.com


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

   Phone: +1 415 645 4726
   Email: ethan.grossman@dolby.com
   URI:   http://www.dolby.com


   Andrew J. Hacker
   MistIQ Technologies, Inc
   Harrisburg, PA
   USA

   Email: ajhacker@mistiqtech.com
   URI:   http://www.mistiqtech.com


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

   Email: sdas@appcomsci.com



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   John Dowdell
   Airbus Defence and Space
   Celtic Springs
   Newport  NP10 8FZ
   United Kingdom

   Email: john.dowdell.ietf@gmail.com


   Henrik Austad
   Cisco Systems
   Philip Pedersens vei 1
   Lysaker  1366
   Norway

   Email: henrik@austad.us


   Kevin Stanton
   Intel

   Email: kevin.b.stanton@intel.com


   Norman Finn
   Huawei

   Email: norman.finn@mail01.huawei.com























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