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Internet Engineering Task Force                               T. Mizrahi
Internet-Draft                                                    HUAWEI
Intended status: Informational                          E. Grossman, Ed.
Expires: December 1, 2020                                          DOLBY
                                                            May 30, 2020


       Deterministic Networking (DetNet) Security Considerations
                     draft-ietf-detnet-security-10

Abstract

   A DetNet (deterministic network) provides specific performance
   guarantees to its data flows, such as extremely low data loss rates
   and bounded latency.  As a result, securing a DetNet implies that in
   addition to the best practice security measures taken for any
   mission-critical network, additional security measures may be needed
   whose purpose is exclusively to secure the intended operation of
   these novel service properties.

   Designers of DetNet components (such as routers) that provide these
   unique DetNet properties have the responsibility to uphold certain
   security-related properties that can be assumed by DetNet system-
   level designers.  For example, the assumption that network traffic
   associated with a given flow can never affect traffic associated with
   a different flow is only true if the underlying components make it
   so.

   This document addresses DetNet-specific security considerations from
   the perspective of both the DetNet component designer and the DetNet
   system-level designer.  It is assumed that both classes of reader are
   already familiar with network security best practices for the data
   plane technologies underlying a given DetNet implementation.
   Component-level considerations include isolation of data flows from
   each other, ingress filtering, and detection and reporting of packet
   arrival time violations.  System-level considerations include a
   threat model and a taxonomy of relevant attacks, including their
   potential impacts and mitigations.

   A given DetNet may require securing only certain aspects of DetNet
   performance, for example extremely low data loss rates but not
   necessarily bounded latency.  Therefore this document provides an
   association of threats against various use cases by industry, and
   also against the individual service properties as defined in the
   DetNet Use Cases.

   This document also addresses common DetNet security considerations
   related to the IP and MPLS data plane technologies (the first to be



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   identified as supported by DetNet), thereby complementing the
   Security Considerations sections of the various DetNet Data Plane
   (and other) DetNet documents.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 1, 2020.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Abbreviations . . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  Security Considerations for DetNet Component Design . . . . .   7
     3.1.  Resource Allocation . . . . . . . . . . . . . . . . . . .   7
     3.2.  Explicit Routes . . . . . . . . . . . . . . . . . . . . .   7
     3.3.  Redundant Path Support  . . . . . . . . . . . . . . . . .   8
     3.4.  Timing Violation Reporting  . . . . . . . . . . . . . . .   9
   4.  DetNet Security Considerations Compared With DiffServ
       Security Considerations . . . . . . . . . . . . . . . . . . .   9
   5.  Security Threats  . . . . . . . . . . . . . . . . . . . . . .  10



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     5.1.  Threat Model  . . . . . . . . . . . . . . . . . . . . . .  10
     5.2.  Threat Analysis . . . . . . . . . . . . . . . . . . . . .  11
       5.2.1.  Delay . . . . . . . . . . . . . . . . . . . . . . . .  11
         5.2.1.1.  Delay Attack  . . . . . . . . . . . . . . . . . .  11
       5.2.2.  DetNet Flow Modification or Spoofing  . . . . . . . .  11
       5.2.3.  Resource Segmentation or Slicing  . . . . . . . . . .  11
         5.2.3.1.  Inter-segment Attack  . . . . . . . . . . . . . .  11
       5.2.4.  Packet Replication and Elimination  . . . . . . . . .  12
         5.2.4.1.  Replication: Increased Attack Surface . . . . . .  12
         5.2.4.2.  Replication-related Header Manipulation . . . . .  12
       5.2.5.  Path Choice . . . . . . . . . . . . . . . . . . . . .  12
         5.2.5.1.  Path Manipulation . . . . . . . . . . . . . . . .  12
         5.2.5.2.  Path Choice: Increased Attack Surface . . . . . .  13
       5.2.6.  Controller Plane  . . . . . . . . . . . . . . . . . .  13
         5.2.6.1.  Control or Signaling Packet Modification  . . . .  13
         5.2.6.2.  Control or Signaling Packet Injection . . . . . .  13
       5.2.7.  Scheduling or Shaping . . . . . . . . . . . . . . . .  13
         5.2.7.1.  Reconnaissance  . . . . . . . . . . . . . . . . .  13
       5.2.8.  Time Synchronization Mechanisms . . . . . . . . . . .  13
     5.3.  Threat Summary  . . . . . . . . . . . . . . . . . . . . .  13
   6.  Security Threat Impacts . . . . . . . . . . . . . . . . . . .  14
     6.1.  Delay-Attacks . . . . . . . . . . . . . . . . . . . . . .  17
       6.1.1.  Data Plane Delay Attacks  . . . . . . . . . . . . . .  17
       6.1.2.  Controller Plane Delay Attacks  . . . . . . . . . . .  18
     6.2.  Flow Modification and Spoofing  . . . . . . . . . . . . .  18
       6.2.1.  Flow Modification . . . . . . . . . . . . . . . . . .  18
       6.2.2.  Spoofing  . . . . . . . . . . . . . . . . . . . . . .  18
         6.2.2.1.  Dataplane Spoofing  . . . . . . . . . . . . . . .  18
         6.2.2.2.  Controller Plane Spoofing . . . . . . . . . . . .  19
     6.3.  Segmentation Attacks (injection)  . . . . . . . . . . . .  19
       6.3.1.  Data Plane Segmentation . . . . . . . . . . . . . . .  19
       6.3.2.  Controller Plane Segmentation . . . . . . . . . . . .  19
     6.4.  Replication and Elimination . . . . . . . . . . . . . . .  20
       6.4.1.  Increased Attack Surface  . . . . . . . . . . . . . .  20
       6.4.2.  Header Manipulation at Elimination Routers  . . . . .  20
     6.5.  Control or Signaling Packet Modification  . . . . . . . .  20
     6.6.  Control or Signaling Packet Injection . . . . . . . . . .  20
     6.7.  Reconnaissance  . . . . . . . . . . . . . . . . . . . . .  20
     6.8.  Attacks on Time Sync Mechanisms . . . . . . . . . . . . .  21
     6.9.  Attacks on Path Choice  . . . . . . . . . . . . . . . . .  21
   7.  Security Threat Mitigation  . . . . . . . . . . . . . . . . .  21
     7.1.  Path Redundancy . . . . . . . . . . . . . . . . . . . . .  21
     7.2.  Integrity Protection  . . . . . . . . . . . . . . . . . .  21
     7.3.  DetNet Node Authentication  . . . . . . . . . . . . . . .  22
     7.4.  Dummy Traffic Insertion . . . . . . . . . . . . . . . . .  23
     7.5.  Encryption  . . . . . . . . . . . . . . . . . . . . . . .  23
       7.5.1.  Encryption Considerations for DetNet  . . . . . . . .  23
     7.6.  Control and Signaling Message Protection  . . . . . . . .  24



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     7.7.  Dynamic Performance Analytics . . . . . . . . . . . . . .  25
     7.8.  Mitigation Summary  . . . . . . . . . . . . . . . . . . .  25
   8.  Association of Attacks to Use Cases . . . . . . . . . . . . .  27
     8.1.  Use Cases by Common Themes  . . . . . . . . . . . . . . .  27
       8.1.1.  Sub-Network Layer . . . . . . . . . . . . . . . . . .  27
       8.1.2.  Central Administration  . . . . . . . . . . . . . . .  28
       8.1.3.  Hot Swap  . . . . . . . . . . . . . . . . . . . . . .  28
       8.1.4.  Data Flow Information Models  . . . . . . . . . . . .  29
       8.1.5.  L2 and L3 Integration . . . . . . . . . . . . . . . .  29
       8.1.6.  End-to-End Delivery . . . . . . . . . . . . . . . . .  29
       8.1.7.  Proprietary Deterministic Ethernet Networks . . . . .  30
       8.1.8.  Replacement for Proprietary Fieldbuses  . . . . . . .  30
       8.1.9.  Deterministic vs Best-Effort Traffic  . . . . . . . .  30
       8.1.10. Deterministic Flows . . . . . . . . . . . . . . . . .  31
       8.1.11. Unused Reserved Bandwidth . . . . . . . . . . . . . .  31
       8.1.12. Interoperability  . . . . . . . . . . . . . . . . . .  31
       8.1.13. Cost Reductions . . . . . . . . . . . . . . . . . . .  32
       8.1.14. Insufficiently Secure Devices . . . . . . . . . . . .  32
       8.1.15. DetNet Network Size . . . . . . . . . . . . . . . . .  32
       8.1.16. Multiple Hops . . . . . . . . . . . . . . . . . . . .  33
       8.1.17. Level of Service  . . . . . . . . . . . . . . . . . .  33
       8.1.18. Bounded Latency . . . . . . . . . . . . . . . . . . .  33
       8.1.19. Low Latency . . . . . . . . . . . . . . . . . . . . .  34
       8.1.20. Bounded Jitter (Latency Variation)  . . . . . . . . .  34
       8.1.21. Symmetrical Path Delays . . . . . . . . . . . . . . .  34
       8.1.22. Reliability and Availability  . . . . . . . . . . . .  34
       8.1.23. Redundant Paths . . . . . . . . . . . . . . . . . . .  35
       8.1.24. Security Measures . . . . . . . . . . . . . . . . . .  35
     8.2.  Attack Types by Use Case Common Theme . . . . . . . . . .  35
     8.3.  Security Considerations for OAM Traffic . . . . . . . . .  38
   9.  DetNet Technology-Specific Threats  . . . . . . . . . . . . .  38
     9.1.  IP  . . . . . . . . . . . . . . . . . . . . . . . . . . .  39
     9.2.  MPLS  . . . . . . . . . . . . . . . . . . . . . . . . . .  40
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  41
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  41
   12. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  41
   13. Informative References  . . . . . . . . . . . . . . . . . . .  42
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  45

1.  Introduction

   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.
   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



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   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 document provides insight into such system-level
   security considerations.  In addition, designers of DetNet components
   (such as routers) face new security-related challenges in providing
   DetNet services, for example maintaining reliable isolation between
   traffic flows in an environment where IT traffic co-mingles with
   critical reserved-bandwidth OT traffic; this document also examines
   security implications internal to DetNet components.

   Security is of particularly high importance in DetNet networks
   because many of the use cases which are enabled by DetNet [RFC8578]
   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
   because they were under a separate control system or otherwise
   isolated from the IT network, for example [ARINC664P7]).  Security
   considerations for OT networks are not a new area, and there are many
   OT networks today that are connected to wide area networks or the
   Internet; this document focuses on the issues that are specific to
   the DetNet technologies and use cases.

   Given the above considerations, securing a DetNet starts with a
   scrupulously well-designed and well-managed engineered network
   following industry best practices for security at both the data plane
   and controller plane; this is the assumed starting point for the
   considerations discussed herein.  Such assumptions also depend on the
   network components themselves upholding the security-related
   properties that are to be assumed by DetNet system-level designers;
   for example, the assumption that network traffic associated with a
   given flow can never affect traffic associated with a different flow
   is only true if the underlying components make it so.  Such
   properties, which may represent new challenges to component
   designers, are also considered herein.



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   In this context we view the network design and management aspects of
   network security as being primarily concerned with denial-of service
   prevention by ensuring that DetNet traffic goes where it's supposed
   to and that an external attacker can't inject traffic that disrupts
   the DetNet's delivery timing assurance.  The time-specific aspects of
   DetNet security presented here take up where the design and
   management aspects leave off.

   The exact security requirements for any given DetNet network are
   necessarily specific to the use cases handled by that network.  Thus
   the reader is assumed to be familiar with the specific security
   requirements of their use cases, for example those outlined in the
   DetNet Use Cases [RFC8578] and the Security Considerations sections
   of the DetNet documents applicable to the network technologies in
   use, for example [I-D.ietf-detnet-ip]).  A general introduction to
   the DetNet architecture can be found in [RFC8655] and it is also
   recommended to be familiar with the Data Plane model
   [I-D.ietf-detnet-data-plane-framework] and Flow Information Model
   [I-D.ietf-detnet-flow-information-model].

   The DetNet technologies include ways to:

   o  Assign data plane resources for DetNet flows in some or all of the
      intermediate nodes (routers) along the path of the flow

   o  Provide explicit routes for DetNet flows that do not dynamically
      change with the network topology in ways that affect the quality
      of service received by the affected flow(s)

   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 document includes sections considering DetNet component design
   as well as system design.  The latter include threat modeling and
   analysis, threat impact and mitigation, and the association of
   attacks with use cases (based on the Use Case Common Themes section
   of the DetNet Use Cases).

   The structure of the threat model and threat analysis sections were
   originally derived from [RFC7384], which also considers time-related
   security considerations in IP networks.

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).



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   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

3.  Security Considerations for DetNet Component Design

   As noted above, DetNet provides resource allocation, explicit routes
   and redundant path support.  Each of these have associated security
   implications, which are discussed in this section, in the context of
   component design.  Detection, reporting and appropriate action in the
   case of packet arrival time violations are also discussed.

3.1.  Resource Allocation

   A DetNet system security designer relies on the premise that any
   resources allocated to a resource-reserved (OT-type) flow are
   inviolable, in other words there is no physical possibility within a
   DetNet component that resources allocated to a given flow can be
   compromised by any type of traffic in the network; this includes both
   malicious traffic as well as inadvertent traffic such as might be
   produced by a malfunctioning component, for example one made by a
   different manufacturer.  From a security standpoint, this is a
   critical assumption, for example when designing against DOS attacks.
   It is the responsibility of the component designer to ensure that
   this condition is met; this implies protection against excess traffic
   from adjacent flows, and against compromises to the resource
   allocation/deallocation process.

3.2.  Explicit Routes

   The DetNet-specific purpose for constraining the network's ability to
   re-route OT traffic is to maintain the specified service parameters
   (such as upper and lower latency boundaries) for a given flow.  For
   example if the network were to re-route a flow (or some part of a
   flow) based exclusively on statistical path usage metrics, or due to
   malicious activity, it is possible that the new path would have a
   latency that is outside the required latency bounds which were
   designed into the original TE-designed path, thereby violating the
   quality of service for the affected flow (or part of that flow).
   (However, is acceptable for the network to re-route OT traffic in
   such a way as to maintain the specified latency bounds (and any other
   specified service properties) for any reason, for example in response
   to a runtime component or path failure).  From a security standpoint,
   the system designer relies on the premise that the packets will be
   delivered with the specified latency boundaries; thus any component



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   that is involved in controlling or implementing any change of the
   initially TE-configured flow routes needs to prevent malicious or
   accidental re-routing of OT flows that might adversely affect
   delivering the traffic within the specified service parameters.

3.3.  Redundant Path Support

   The DetNet provision for redundant paths (PREOF) (as defined in the
   DetNet Architecture [RFC8655]) provides the foundation for high
   reliablity of a DetNet, by virtually eliminating packet loss (i.e. to
   a degree which is implementation-dependent) through hitless redundant
   packet delivery.  (Note that PREOF is not defined for a DetNet IP
   data plane).

   It is the responsibility of the system designer to determine the
   level of reliability required by their use case, and to specify
   redundant paths sufficient to provide the desired level of
   reliability (in as much as that reliability can be provided through
   the use of redundant paths).  It is the responsibility of the
   component designer to ensure that the relevant PREOF operations are
   executed reliably and securely.  (However, note that not all PREOF
   operations are necessarily implemented in every network; for example
   a packet re-ordering function may not be necessary if the packets are
   either not required to be in order, or if the ordering is performed
   in some other part of the network.)

   As noted in Section 7.2, Packet Sequence Number Integrity
   Considerations, there is a trust relationship between the pair of
   devices that replicate and remove packets, so it is the
   responsibility of the system designer to define these relationships
   with the appropriate security considerations, and the components must
   each uphold the security rights implied by these relationships.

   Ideally a redundant path could be specified from end to end of the
   flow's path, however given that this is not always possible (as
   described in [RFC8655]) the system designer will need to consider the
   resulting end-to-end reliability and security resulting from any
   given arrangment of network segments along the path, each of which
   provides its individual PREOF implementation and thus its individual
   level of reliabiilty and security.

   At the data plane the implementation of PREOF depends on the correct
   assignment and interpretation of packet sequence numbers, as well as
   the actions taken based on them, such as elimination.  Thus the
   integrity of these values must be maintained by the component as they
   are assigned by the DetNet data plane's Service sub-layer, and
   transported by the Forwarding sub-layer.




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3.4.  Timing Violation Reporting

   Another fundamental assumption of a secure DetNet is that in any case
   in which an incoming packet arrives outside of its prescribed time
   window or exceeding the reserved flow bandwidth, something can be
   done about it.  That means that the component's data plane must be
   able to detect such cases, then at least alert the control plane,
   and/or drop the packet, and/or shut down the link if violations
   persist.  Logging of such issues may not be adequate, since a delay
   in response to the situation could result in material damage, for
   example to mechanical devices controlled by the network.

4.  DetNet Security Considerations Compared With DiffServ Security
    Considerations

   DetNet is designed to be compatible with DiffServ [RFC2474] as
   applied to IT traffic in the DetNet.  DetNet also incorporates the
   use of the 6-bit value of the DSCP field of the TOS field of the IP
   header for flow identification for OT traffic, however the DetNet
   interpretation of the DSCP value for OT traffic is not equivalent to
   the PHB selection behavior as defined by DiffServ.

   Thus security consideration for DetNet have some aspects in common
   with DiffServ, in fact overlapping 100% with respect to IP IT
   traffic.  Security considerations for these aspects are part of the
   existing literature on IP network security, specifically the Security
   sections of [RFC2474] and [RFC2475].  However DetNet also introduce
   timing and other considerations which are not present in DiffServ, so
   the DiffServ security considerations are necessary but not sufficient
   for DetNet.

   In the case of DetNet OT traffic, the DSCP value, although
   interpreted differently than in DiffServ, does contribute to
   determination of the service provided to the packet.  Thus in DetNet
   there are similar consequences to DiffServ for lack of detection of,
   or incorrect handling of, packets with mismarked DSCP values, and
   thus many of the points made in the DiffServ draft Security
   discussions are also relevant to DetNet OT traffic, though perhaps in
   modified form.  For example, in DetNet the effect of an undetected or
   incorrectly handled maliciously mismarked DSCP field in an OT packet
   is not identical to affecting that packet's PHB, since DetNet does
   not use the PHB concept for OT traffic, but nonetheless the service
   provided to the packet could be affected, so mitigation measures
   analogous to those prescribed by DiffServ would be appropriate for
   DetNet.  For example, mismarked DSCP values should not cause failure
   of network nodes, and any internal link that cannot be adequately
   secured against modification of DSCP values should be treated as a
   boundary link (and hence any arriving traffic on that link is treated



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   as if it were entering the domain at an ingress node).  The remarks
   in [RFC2474] regarding IPsec and Tunnelling Interactions are also
   relevant (though this is not to say that other sections are less
   relevant).

5.  Security Threats

   This section presents a threat model, and analyzes the possible
   threats in a DetNet-enabled network.  The threats considered in this
   section are independent of any specific technologies used to
   implement the DetNet; Section 9) considers attacks that are
   associated with the DetNet technologies encompassed by
   [I-D.ietf-detnet-data-plane-framework].

   We distinguish controller plane threats from data plane threats.  The
   attack surface may be the same, but the types of attacks as well as
   the motivation behind them, are different.  For example, a delay
   attack is more relevant to data plane than to controller 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 controller plane.

5.1.  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.

   Care has also been taken to adhere to Section 5 of [RFC3552], both
   with respect to which attacks are considered out-of-scope for this
   document, but also which are considered to be the most common threats
   (explored further in Section 5.2 (Threat Analysis).  Most of the
   direct threats to DetNet are active attacks, but it is highly
   suggested that DetNet application developers take appropriate
   measures to protect the content of the DetNet flows from passive
   attacks.




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

5.2.  Threat Analysis

5.2.1.  Delay

5.2.1.1.  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.  The delay may be constant or modulated.

5.2.2.  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.

5.2.3.  Resource Segmentation or Slicing

5.2.3.1.  Inter-segment Attack

   An attacker can inject traffic that will consume network resources
   such that it affects DetNet flows.  This can be performed using non-
   DetNet traffic that indirectly affects DetNet traffic (hardware
   resource exhaustion), or by using DetNet traffic from one DetNet flow
   that directly affects traffic from different DetNet flows.








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5.2.4.  Packet Replication and Elimination

5.2.4.1.  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.

5.2.4.2.  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 in favor of the attacked path.  Once the
      flow from the compromised path is favored by the elminating
      bridge, the flow is hijacked by the attacker.  It is now posible
      to either replace en route packets with malicious packets, or
      simply injecting errors, causing the packets to be dropped at
      their destination.

5.2.5.  Path Choice

5.2.5.1.  Path Manipulation

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





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5.2.5.2.  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
   previous subsection is implemented, it may increase the potential of
   other attacks to be performed.

5.2.6.  Controller Plane

5.2.6.1.  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.

5.2.6.2.  Control or Signaling Packet Injection

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

5.2.7.  Scheduling or Shaping

5.2.7.1.  Reconnaissance

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

   Note that in some cases DetNet flows may be identified based on 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 document we assume they are encrypted
   and/or integrity-protected from external attackers.

5.2.8.  Time Synchronization Mechanisms

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

5.3.  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



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   used, and that the corresponding network equipment takes part in this
   mechanism.


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

6.  Security Threat Impacts

   This section describes and rates the impact of the attacks described
   in Section 5, Security Threats.  In this section, the impacts as
   described assume that the associated mitigation is not present or has
   failed.  Mitigations are discussed in Section 7, Security Threat
   Mitigation.

   In computer security, the impact (or consequence) of an incident can
   be measured in loss of confidentiality, integrity or availability of
   information.  In the case of time sensitive networks, the impact of a
   network exploit can also include failure or malfunction of mechanical
   and/or other OT systems.



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   DetNet raises these stakes significantly for OT applications,
   particularly those which may have been designed to run in an OT-only
   environment and thus may not have been designed for security in an IT
   environment with its associated devices, services and protocols.

   The severity of various components of the impact of a successful
   vulnerability exploit to use cases by industry is available in more
   detail in [RFC8578].  Each of the use cases in the DetNet Use Cases
   is represented in the table below, including Pro Audio, Electrical
   Utilities, Industrial M2M (split into two areas, M2M Data Gathering
   and M2M Control Loop), and others.

   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
   vary greatly in scope and severity.  In order to reduce the number of
   variables, only the following were included: Financial, Health and
   Safety, People well being (People WB), 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.


   Table, Part One (of Two)
   +------------------+-----------------------------------------+-----+
   |                  | Pro A | Util | Bldg |Wire- | Cell |M2M  |M2M  |
   |                  |       |      |      | less |      |Data |Ctrl |
   +------------------+-----------------------------------------+-----+
   | Criticality      | Med   | Hi   | Low  | Med  | Med  | Med | Med |
   +------------------+-----------------------------------------+-----+
   | Effects
   +------------------+-----------------------------------------+-----+



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

   Table, Part Two (of Two)
   +------------------+--------------------------+
   |                  | Mining | Block | Network |
   |                  |        | Chain | Slicing |
   +------------------+--------------------------+
   | Criticality      | Hi     | Med   | Hi      |
   +------------------+--------------------------+
   | Effects
   +------------------+--------------------------+
   |  Financial       | Hi     | Hi    | Hi      |
   +------------------+--------------------------+
   |  Health/Safety   | Hi     | Low   | Med     |
   +------------------+--------------------------+
   |  People WB       | Hi     | Low   | Med     |
   +------------------+--------------------------+
   |  Effect 1 org    | Hi     | Hi    | Hi      |
   +------------------+--------------------------+
   |  Effect >1 org   | Hi     | Low   | Hi      |
   +------------------+--------------------------+



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   |Recovery
   +------------------+--------------------------+
   |  Recov Time Obj  | Hi     | Low   | Hi      |
   +------------------+--------------------------+
   |  Recov Point Obj | Hi     | Low   | Hi      |
   +------------------+--------------------------+
   |DetNet Dependence
   +------------------+--------------------------+
   |  Time Dependency | Hi     | Low   | Hi      |
   +------------------+--------------------------+
   |  Latency/Jitter  | Hi     | Low   | Hi      |
   +------------------+--------------------------+
   |  Data Integrity  | Hi     | Hi    | Hi      |
   +------------------+--------------------------+
   |  Src Node Integ  | Hi     | Hi    | Hi      |
   +------------------+--------------------------+
   |  Availability    | Hi     | Hi    | Hi      |
   +------------------+--------------------------+


             Figure 2: Impact of Attacks by Use Case Industry

   The rest of this section will cover impact of the different groups in
   more detail.

6.1.  Delay-Attacks

6.1.1.  Data Plane Delay Attacks

   Note that 'delay attack' also includes the possibility of a 'negative
   delay' or early arrival of a packet, or possibly adversely changing
   the timestamp value.

   Delayed messages in a DetNet link can result in the same behavior as
   dropped messages in ordinary networks as the services attached to the
   DetNet flow have strict deterministic requirements.

   For a single path scenario, disruption is a real possibility, whereas
   in a multipath scenario, large delays or instabilities in one DetNet
   flow can lead to increased buffer and processor resources at the
   eliminating router.

   A data-plane delay attack on a system controlling substantial moving
   devices, for example in industrial automation, can cause physical
   damage.  For example, if the network promises a bounded latency of
   2ms for a flow, yet the machine receives it with 5ms latency, the
   machine's control loop can become unstable.




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6.1.2.  Controller Plane Delay Attacks

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

   o  Delayed tear-down can lead to resource leakage, which in turn can
      result in failure to allocate new DetNet flows, finally giving
      rise to a denial of service attack.

   o  Failure to deliver, or severely delaying, controller plane
      messages adding an endpoint to a multicast-group will prevent the
      new endpoint from receiving expected frames thus disrupting
      expected behavior.

   o  Delaying messages removing an endpoint from a group can lead to
      loss of privacy as the endpoint will continue to receive messages
      even after it is supposedly removed.

6.2.  Flow Modification and Spoofing

6.2.1.  Flow Modification

   If the contents of a packet header or body can be modified by the
   attacker, this can cause the packet to be routed incorrectly or
   dropped, or the payload to be corrupted or subtly modified.

6.2.2.  Spoofing

6.2.2.1.  Dataplane Spoofing

   Spoofing dataplane messages can result in increased resource
   consumptions on the routers throughout the network as it will
   increase buffer usage and processor 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 resource 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.







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6.2.2.2.  Controller Plane Spoofing

   A successful controller plane spoofing-attack will potentionally have
   adverse effects.  It can do virtually anything from:

   o  modifying existing DetNet flows by changing the available
      bandwidth

   o  add or remove endpoints from a DetNet flow

   o  drop DetNet flows completely

   o  falsely create new DetNet flows (exhaust the systems resources, or
      to enable DetNet flows that are outside the Network Engineer's
      control)

6.3.  Segmentation Attacks (injection)

6.3.1.  Data Plane Segmentation

   Injection of false messages in a DetNet flow could lead to exhaustion
   of the available bandwidth for that flow if the routers attribute
   these false messages to that flow's budget.

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

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

6.3.2.  Controller Plane Segmentation

   In a successful controller plane segmentation attack, control
   messages are acted on by nodes in the network, unbeknownst to the
   central controller or the network engineer.  This has the potential
   to:

   o  create new DetNet flows (exhausting resources)

   o  drop existing DetNet flows (denial of service)

   o  add/remove end-stations to a multicast group (loss of privacy)

   o  modify the DetNet flow attributes (affecting available bandwidth



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6.4.  Replication and Elimination

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

6.4.1.  Increased Attack Surface

   Covered briefly in Section 6.3, Segmentation Attacks.

6.4.2.  Header Manipulation at Elimination Routers

   Covered briefly in Section 6.3, Segmentation Attacks.

6.5.  Control or Signaling Packet Modification

   If control packets are subject to manipulation undetected, the
   network can be severely compromised.

6.6.  Control or Signaling Packet Injection

   If an attacker can inject control packets undetected, the network can
   be severely compromised.

6.7.  Reconnaissance

   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.

   Applications which are ported from a private OT network to the higher
   visibility DetNet environment may need to be adapted to limit
   distinctive flow properties that could make them susceptible to
   reconnaissance.






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6.8.  Attacks on Time Sync Mechanisms

   Attacks on time sync mechanisms are addressed in [RFC7384].

6.9.  Attacks on Path Choice

   This is covered in part in Section 6.3, Segmentation Attacks, and as
   with Replication and Elimination (Section 6.4), this is relevant for
   DataPlane messages.

7.  Security Threat Mitigation

   This section describes a set of measures that can be taken to
   mitigate the attacks described in Section 5, Security Threats.  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.

7.1.  Path Redundancy

   Description

      A DetNet flow that can be forwarded simultaneously over multiple
      paths.  Path replication and elimination [RFC8655] provides
      resiliency to dropped or delayed packets.  This redundancy
      improves the robustness to failures and to man-in-the-middle
      attacks.  Note: At the time of this writing, PREOF is not defined
      for the IP data plane.

   Related attacks

      Path redundancy can be used to mitigate various man-in-the-middle
      attacks, including attacks described in Section 5.2.1,
      Section 5.2.2, Section 5.2.3, and Section 5.2.8.  However it is
      also possible that multiple paths may make it more difficult to
      locate the source of a MITM attacker.

      A delay modulation attack could result in extensively exercising
      parts of the code that wouldn't normally be extensively exercised
      and thus might expose flaws in the system that might otherwise not
      be exposed.

7.2.  Integrity Protection

   Description





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      An integrity protection mechanism, such as a Hash-based Message
      Authentication Code (HMAC) can be used to mitigate modification
      attacks on IP packets.  Integrity protection in the controller
      plane is discussed in Section 7.6.

   Packet Sequence Number Integrity Considerations

      The use of PREOF in a DetNet implementation implies the use of a
      sequence number for each packet.  There is a trust relationship
      between the device that adds the sequence number and the device
      that removes the sequence number.  The sequence number may be end-
      to-end source to destination, or may be added/deleted by network
      edge devices.  The adder and remover(s) have the trust
      relationship because they are the ones that ensure that the
      sequence numbers are not modifiable.  Between those two points,
      there may or may not be replication and elimination functions.
      The elimination functions must be able to see the sequence
      numbers.  Therefore any encryption that is done between adders and
      removers must not obscure the sequence number.  If the sequence
      removers and the eliminators are in the same physical device, it
      may be possible to obscure the sequence number, however that is a
      layer violation, and is not recommended practice.  Note: At the
      time of this writing, PREOF is not defined for the IP data plane.

   Related attacks

      Integrity protection mitigates attacks related to modification and
      tampering, including the attacks described in Section 5.2.2 and
      Section 5.2.4.

7.3.  DetNet Node Authentication

   Description

      Source authentication verifies the authenticity of DetNet sources,
      enabling mitigation of spoofing attacks.  Note that while
      integrity protection (Section 7.2) prevents intermediate nodes
      from modifying information, authentication can provide traffic
      origin verification, i.e. to verify that each packet in a DetNet
      flow is from a trusted source.  Authentication may be implemented
      as part of ingress filtering, for example.

   Related attacks

      DetNet node authentication is used to mitigate attacks related to
      spoofing, including the attacks of Section 5.2.2, and
      Section 5.2.4.




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7.4.  Dummy Traffic Insertion

   Description

      With some queueing methods such as [IEEE802.1Qch-2017] it is
      possible to introduce dummy traffic in order to regularize the
      timing of packet transmission.

   Related attacks

      Removing distinctive temporal properties of individual packets or
      flows can be used to mitigate against reconnaissance attacks
      Section 5.2.7.

7.5.  Encryption

   Description

      DetNet flows can in principle be forwarded in encrypted form at
      the DetNet layer, however, regarding encryption of IP headers see
      Section 9.

      Alternatively, if the payload is end-to-end encrypted at the
      application layer, the DetNet nodes should not have any need to
      inspect the payload itself, and thus the DetNet implementation can
      be data-agnostic.

      Encryption can also be applied at the subnet layer, for example
      for Ethernet using MACSec, as noted in Section 9.

   Related attacks

      Encryption can be used to mitigate recon attacks (Section 5.2.7).
      However, for a DetNet network to give differentiated quality of
      service on a flow-by-flow basis, the network must be able to
      identify the flows individually.  This implies that in a recon
      attack the attacker may also be able to track individual flows to
      learn more about the system.

7.5.1.  Encryption Considerations for DetNet

   Any compute time which is required for encryption and decryption
   processing ('crypto') must be included in the flow latency
   calculations.  Thus, crypto algorithms used in a DetNet must have
   bounded worst-case execution times, and these values must be used in
   the latency calculations.





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   Some crypto algorithms are symmetric in encode/decode time (such as
   AES) and others are asymmetric (such as public key algorithms).
   There are advantages and disadvantages to the use of either type in a
   given DetNet context.  The discussion in this document relates to the
   timing implications of crypto for DetNet; it is assumed that
   integrity considerations are covered elsewhere in the literature.

   Asymmetrical crypto is typically not used in networks on a packet-by-
   packet basis due to its computational cost.  For example, if only
   endpoint checks or checks at a small number of intermediate points
   are required, asymmetric crypto can be used to authenticate
   distribution or exchange of a secret symmetric crypto key; a
   successful check based on that key will provide traffic origin
   verification, as long as the key is kept secret by the participants.
   TLS and IKE (for IPsec) are examples of this for endpoint checks.

   However, if secret symmetrical keys are used for this purpose the key
   must be given to all relays, which increases the probability of a
   secret key being leaked.  Also, if any relay is compromised or
   misbehaving it may inject traffic into the flow.

   Alternatively, asymmetric crypto can provide traffic origin
   verification at every intermediate node.  For example, a DetNet flow
   can be associated with an (asymmetric) keypair, such that the private
   key is available to the source of the flow and the public key is
   distributed with the flow information, allowing verification at every
   node for every packet.  However, this is more computationally
   expensive.

   In either case, origin verification also requires replay detection as
   part of the security protocol to prevent an attacker from recording
   and resending traffic, e.g., as a denial of service attack on flow
   forwarding resources.

   If crypto keys are to be regenerated over the duration of the flow
   then the time required to accomplish this must be accounted for in
   the latency calculations.

7.6.  Control and Signaling Message Protection

   Description

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

   Related attacks





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      These mechanisms can be used to mitigate various attacks on the
      controller plane, as described in Section 5.2.6, Section 5.2.8 and
      Section 5.2.5.

7.7.  Dynamic Performance Analytics

   Description

      The expectation is that the network will have a way to monitor to
      detect if timing guarantees are not being met, and a way to alert
      the controller plane in that event.  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
      YANG.

   Related attacks

      Performance analytics can be used to mitigate various attacks,
      including the ones described in Section 5.2.1 (Delay Attack),
      Section 5.2.3 (Resource Segmentation Attack), and Section 5.2.8
      (Time Sync Attack).

      For example, in the case of data plane delay attacks, one possible
      mitigation is to timestamp the data at the source, and timestamp
      it again at the destination, and if the resulting latency exceeds
      the promised bound, discard that data and warn the operator (and/
      or enter a fail-safe mode).  Note that DetNet specifies packet
      sequence numbering, however it does not specify use of packet
      timestamps, although they may be used by the underlying transport
      (for example TSN) to provide the service.

7.8.  Mitigation Summary

   The following table maps the attacks of Section 5, Security Threats,
   to the impacts of Section 6, Security Threat Impacts, 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.


   +----------------------+---------------------+---------------------+



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   | Attack               |      Impact         |     Mitigations     |
   +----------------------+---------------------+---------------------+
   |Delay Attack          |-Non-deterministic   |-Path redundancy     |
   |                      | delay               |-Performance         |
   |                      |-Data disruption     | analytics           |
   |                      |-Increased resource  |                     |
   |                      | consumption         |                     |
   +----------------------+---------------------+---------------------+
   |Reconnaissance        |-Enabler for other   |-Encryption          |
   |                      | attacks             |-Dummy traffic       |
   |                      |                     |           insertion |
   +----------------------+---------------------+---------------------+
   |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          |
   |                      |-Non-deterministic   |                     |
   |                      | delay               |                     |
   |                      |-Data disruption     |                     |
   +----------------------+---------------------+---------------------+
   |Attacks on Time Sync  |-Non-deterministic   |-Path redundancy     |



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   |Mechanisms            | delay               |-Control message     |
   |                      |-Increased resource  | protection          |
   |                      | consumption         |-Performance         |
   |                      |-Data disruption     | analytics           |
   +----------------------+---------------------+---------------------+

            Figure 3: Mapping Attacks to Impact and Mitigations

8.  Association of Attacks to Use Cases

   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 [RFC8578].

   See also Figure 2 for a mapping of the impact of attacks per use case
   by industry.

8.1.  Use Cases by Common Themes

   In this section we review each theme and discuss the attacks that are
   applicable to that theme, as well as anything specific about the
   impact and mitigations for that attack with respect to that theme.
   The table Figure 5, Mapping Between Themes and Attacks, then provides
   a summary of the attacks that are applicable to each theme.

8.1.1.  Sub-Network Layer

   DetNet is expected to run over various transmission mediums, with
   Ethernet being the first identified.  Attacks such as Delay or
   Reconnaissance might be implemented differently on a different
   transmission medium, however the impact on the DetNet as a whole
   would be essentially the same.  We thus conclude that all attacks and
   impacts that would be applicable to DetNet over Ethernet (i.e. all
   those named in this document) would also be applicable to DetNet over
   other transmission mediums.

   With respect to mitigations, some methods are specific to the
   Ethernet medium, for example time-aware scheduling using 802.1Qbv can
   protect against excessive use of bandwidth at the ingress - for other
   mediums, other mitigations would have to be implemented to provide
   analogous protection.







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8.1.2.  Central Administration

   A DetNet network can 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.

   In this document we distinguish between attacks on the DetNet
   Controller plane vs. Data plane.  But is an attack affecting control
   plane packets synonymous with an attack on the control plane itself?
   For purposes of this document let us consider an attack on the
   control system itself to be out of scope, and consider all attacks
   named in this document which are relevant to controller plane packets
   to be relevant to this theme, including Path Manipulation, Path
   Choice, Control Packet Modification or Injection, Reconaissance and
   Attacks on Time Sync Mechanisms.

8.1.3.  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.

   An attack surface related to Hot Swap is that the DetNet network must
   at least consider input at runtime from devices that were not part of
   the initial configuration of the network.  Even a "perfect" (or
   "hitless") replacement of a device at runtime would not necessarily
   be ideal, since presumably one would want to distinguish it from the
   original for OAM purposes (e.g. to report hot swap of a failed
   device).

   This implies that an attack such as Flow Modification, Spoofing or
   Inter-segment (which could introduce packets from a "new" device
   (i.e. one heretofore unknown on the network) could be used to exploit
   the need to consider such packets (as opposed to rejecting them out
   of hand as one would do if one did not have to consider introduction
   of a new device).

   Similarly if the network was designed to support runtime replacement
   of a clock device, then presence (or apparent presence) and thus
   consideration of packets from a new such device could affect the
   network, or the time sync of the network, for example by initiating a
   new Best Master Clock selection process.  Thus attacks on time sync




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   should be considered when designing hot swap type functionality (see
   [RFC7384]).

8.1.4.  Data Flow Information Models

   Data Flow YANG models specific to DetNet networks are specified by
   DetNet, and thus are 'new' and thus potentially present a new attack
   surface.

8.1.5.  L2 and L3 Integration

   A DetNet network integrates Layer 2 (bridged) networks (e.g.  AVB/TSN
   LAN) and Layer 3 (routed) networks via the use of well-known
   protocols such as IP, MPLS-PW, and Ethernet.

   There are no specific entries in our table, however that does not
   imply that there could be no relevant attacks related to L2,L3
   integration.

8.1.6.  End-to-End Delivery

   Packets sent over DetNet are not to be dropped by the network due to
   congestion.  (Packets may however intentionally be dropped for
   intended reasons, e.g. per security measures).

   A Data plane attack may force packets to be dropped, for example a
   "long" Delay or Replication/Elimination or Flow Modification attack.

   The same result might be obtained by a controller plane attack, e.g.
   Path Manipulation or Signaling Packet Modification.

   It may be that such attacks are limited to Internal MITM attackers,
   but other possibilities should be considered.

   An attack may also cause packets that should not be delivered to be
   delivered, such as by forcing packets from one (e.g. replicated) path
   to be preferred over another path when they should not be
   (Replication attack), or by Flow Modification, or by Path Choice or
   Packet Injection.  A Time Sync attack could cause a system that was
   expecting certain packets at certain times to accept unintended
   packets based on compromised system time or time windowing in the
   scheduler.

   Packets may also be dropped due to malfunctioning software or
   hardware.






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8.1.7.  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.  In cases where a
   DetNet intersects with remnants of such networks or their protocols,
   such as by protocol emulation or access to such a network via a
   gateway, new attack surfaces can be opened.

   For example an Inter-Segment or Controller plane attack such as Path
   Manipulation, Path Choice or Control Packet Modification/Injection
   could be used to exploit commands specific to such a protocol, or
   that are interpreted differently by the different protocols or
   gateway.

8.1.8.  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.  In cases where a DetNet
   intersects with such fieldbuses or their protocols, such as by
   protocol emulation or access via a gateway, new attack surfaces can
   be opened.

   For example an Inter-Segment or Controller plane attack such as Path
   Manipulation, Path Choice or Control Packet Modification/Injection
   could be used to exploit commands specific to such a protocol, or
   that are interpreted differently by the different protocols or
   gateway.

8.1.9.  Deterministic vs Best-Effort Traffic

   Most of the themes described in this document address OT (reserved)
   DetNet flows - this item is intended to address issues related to IT
   traffic on a DetNet.

   DetNet is intended to support coexistence of time-sensitive
   operational (OT, deterministic) traffic and information (IT, "best
   effort") traffic on the same ("unified") network.

   With DetNet, this coexistance will become more common, and
   mitigations will need to be established.  The fact that the IT
   traffic on a DetNet is limited to a corporate controlled network
   makes this a less difficult problem compared to being exposed to the
   open Internet, however this aspect of DetNet security should not be
   underestimated.





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   An Inter-segment attack can flood the network with IT-type traffic
   with the intent of disrupting handling of IT traffic, and/or the goal
   of interfering with OT traffic.  Presumably if the DetNet flow
   reservation and isolation of the DetNet is well-designed (better-
   designed than the attack) then interference with OT traffic should
   not result from an attack that floods the network with IT traffic.

   However the DetNet's handling of IT traffic may not (by design) be as
   resilient to DOS attack, and thus designers must be otherwise
   prepared to mitigate DOS attacks on IT traffic in a DetNet.

8.1.10.  Deterministic Flows

   Reserved bandwidth data flows (deterministic flows) must provide the
   allocated bandwidth, and must be isolated from each other.

   A Spoofing or Inter-segment attack which adds packet traffic to a
   bandwidth-reserved DetNet flow could cause that flow to occupy more
   bandwidth than it was allocated, resulting in interference with other
   DetNet flows.

   A Flow Modification or Spoofing or Header Manipulation or Control
   Packet Modification attack could cause packets from one flow to be
   directed to another flow, thus breaching isolation between the flows.

8.1.11.  Unused Reserved Bandwidth

   If bandwidth reservations are made for a DetNet flow but the
   associated bandwidth is not used at any point in time, that bandwidth
   is made available on the network for best-effort traffic.  However,
   note that security considerations for best-effort traffic on a DetNet
   network is out of scope of the present document, provided that such
   an attack does not affect performance for DetNet OT traffic.

8.1.12.  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.

   Given that the DetNet specifications are unambiguously written and
   that the implementations are accurate, then this should not in and of
   itself cause a security concern; however, in the real world, it could
   be.  The network operator can mitigate this through sufficient
   interoperability testing.





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8.1.13.  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.  Such "low cost"
   hardware or software components might present security concerns.

   Network operators can mitigate such concerns through sufficient
   product testing.

8.1.14.  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.  Software that was originally designed for
   operation in isolated OT networks (and thus may not have been
   designed to be sufficiently secure, or secure at all) but is then
   deployed on a DetNet network that is intended to be highly secure may
   present an attack surface.  (For example IoT exploits like the Mirai
   video-camera botnet ([MIRAI]).

   The DetNet network operator may need to take specific actions to
   protect such devices.

8.1.15.  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.

   The size of the network 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.

   A Delay attack might be as relevant to a small network as to a large
   network, although the amount of delay might be different.

   Attacks sourced from IT traffic might be more likely in large
   networks, since more people might have access to the network,
   presenting a larger attack surface.  Similarly Path Manipulation,
   Path Choice and Time Sync attacks seem more likely relevant to large
   networks.





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8.1.16.  Multiple Hops

   Large DetNet networks (e.g. a Utility Grid network) may involve many
   "hops" over various kinds of links for example radio repeaters,
   microwave links, fiber optic links, etc.

   An attack that takes advantage of flaws (or even normal operation) in
   the device drivers for the various links (through internal knowledge
   of how the individual driver or firmware operates, perhaps like the
   Stuxnet attack) could take proportionately greater advantage of this
   topology.

   It is also possible that this DetNet topology will not be in as
   common use as other more homogeneous topologies so there may be more
   opportunity for attackers to exploit software and/or protocol flaws
   in the implementations which have not been wrung out by extensive
   use, particularly in the case of early adopters.

   Of the attacks we have defined, the ones identified above as relevant
   to "large" networks are the most relevant.

8.1.17.  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 DetNet flow, requesting worst case maximum and/or minimum
   latency for a given path or DetNet flow, 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 service level is not available (as opposed to
   accepting the parameter but then not delivering the desired
   behavior).

   Controller plane attacks such as Signaling Packet Modification and
   Injection could be used to modify or create control traffic that
   could interfere with the process of a user requesting a level of
   service and/or the network's reply.

   Reconnaissance could be used to characterize flows and perhaps target
   specific flows for attack via the controller plane as noted above.

8.1.18.  Bounded Latency

   DetNet provides the expectation of guaranteed bounded latency.

   Delay attacks can cause packets to miss their agreed-upon latency
   boundaries.




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   Time Sync attacks can corrupt the system's time reference, resulting
   in missed latency deadlines (with respect to the "correct" time
   reference).

8.1.19.  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.

   Attacks on the controller plane (as described in the Level of Service
   theme) and Delay and Time attacks (as described in the Bounded
   Latency theme) both apply here.

8.1.20.  Bounded Jitter (Latency Variation)

   DetNet is expected to provide bounded jitter (packet to packet
   latency variation).

   Delay attacks can cause packets to vary in their arrival times,
   resulting in packet to packet latency variation, thereby violating
   the jitter specification.

8.1.21.  Symmetrical Path Delays

   Some applications would like to specify that the transit delay time
   values be equal for both the transmit and return paths.

   Delay attacks can cause path delays to materially differ between
   paths.

   Time Sync attacks can corrupt the system's time reference, resulting
   in path delays that may be perceived to be different (with respect to
   the "correct" time reference) even if they are not materially
   different.

8.1.22.  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




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   be required of a given system, and should define parameters for
   communicating these kinds of metrics within the network.

   Any attack on the system, of any type, can affect its overall
   reliability and availability, thus in our table we have marked every
   attack.  Since every DetNet depends to a greater or lesser degree on
   reliability and availability, this essentially means that all
   networks have to mitigate all attacks, which to a greater or lesser
   degree defeats the purpose of associating attacks with use cases.  It
   also underscores the difficulty of designing "extremely high
   reliability" networks.

8.1.23.  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.

   Replication-related attacks are by definition applicable here.
   Controller plane attacks can also interfere with the configuration of
   redundant paths.

8.1.24.  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?

   This is TBD, thus there are no specific entries in our table, however
   that does not imply that there could be no relevant attacks.

8.2.  Attack Types by Use Case Common Theme

   The following table lists the attacks of Section 5, Security Threats,
   assigning a number to each type of attack.  That number is then used
   as a short form identifier for the attack in Figure 5, Mapping
   Between Themes and Attacks.











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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                 | +|  |  |  |  |  |  | +| +| +| +|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Bounded Jitter              | +|  |  |  |  |  |  |  |  |  |  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Symmetric Path Delays       | +|  |  |  |  |  |  |  |  |  | +|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Reliability and Availability| +| +| +| +| +| +| +| +| +| +| +|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Redundant Paths             |  |  |  | +| +|  |  | +| +|  |  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Security Measures           |  |  |  |  |  |  |  |  |  |  |  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+

               Figure 5: Mapping Between Themes and Attacks







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8.3.  Security Considerations for OAM Traffic

   This section considers DetNet-specific security considerations for
   packet traffic that is generated and transmitted over a DetNet as
   part of OAM (Operations, Administration and Maintenance).  For
   purposes of this discussion, OAM traffic falls into one of two basic
   types:

   o  OAM traffic generated by the network itself.  The additional
      bandwidth required for such packets is added by the network
      administration, presumably transparent to the customer.  Security
      considerations for such traffic are not DetNet-specific (apart
      from such traffic being subject to the same DetNet-specific
      security considerations as any other DetNet data flow) and are
      thus not covered in this document.

   o  OAM traffic generated by the customer.  From a DetNet security
      point of view, DetNet security considerations for such traffic are
      exactly the same as for any other customer data flows.

   Thus OAM traffic presents no additional (i.e.  OAM-specific) DetNet
   security considerations.

9.  DetNet Technology-Specific Threats

   Section 5, Security Threats, described threats which are independent
   of a DetNet implementation.  This section considers threats
   specifically related to the IP- and MPLS-specific aspects of DetNet
   implementations.

   The primary security considerations for the data plane specifically
   are to maintain the integrity of the data and the delivery of the
   associated DetNet service traversing the DetNet network.

   The primary relevant differences between IP and MPLS implementations
   are in flow identification and OAM methodologies.

   As noted in [RFC8655], DetNet operates at the IP layer
   ([I-D.ietf-detnet-ip]) and delivers service over sub-layer
   technologies such as MPLS ([I-D.ietf-detnet-mpls]) and IEEE 802.1
   Time-Sensitive Networking (TSN) ([I-D.ietf-detnet-ip-over-tsn]).
   Application flows can be protected through whatever means are
   provided by the layer and sub-layer technologies.  For example,
   technology-specific encryption may be used, such as that provided by
   IPSec [RFC4301] for IP flows and/or by an underlying sub-net using
   MACSec [IEEE802.1AE-2018] for IP over Ethernet (Layer-2) flows.





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   However, if the DetNet nodes cannot decrypt IPsec traffic, IPSec may
   not be a valid option; this is because the DetNet IP data plane
   identifies flows via a 6-tuple that consists of two IP addresses, the
   transport protocol ID, two transport protocol port numbers and the
   DSCP in the IP header.  When IPsec is used, the transport header is
   encrypted and the next protocol ID is an IPsec protocol, usually ESP,
   and not a transport protocol (e.g., neither TCP nor UDP, etc.)
   leaving only three components of the 6-tuple, which are the two IP
   addresses and the DSCP, which are in general not sufficient to
   identify a DetNet flow.

   Sections below discuss threats specific to IP and MPLS in more
   detail.

9.1.  IP

   The IP protocol has a long history of security considerations and
   architectural protection mechanisms.  From a data plane perspective
   DetNet does not add or modify any IP header information, and its use
   as a DetNet Data Plane does not introduce any new security issues
   that were not there before, apart from those already described in the
   data-plane-independent threats section Section 5, Security Threats.

   Thus the security considerations for a DetNet based on an IP data
   plane are purely inherited from the rich IP Security literature and
   code/application base, and the data-plane-independent section of this
   document.

   Maintaining security for IP segments of a DetNet may be more
   challenging than for the MPLS segments of the network, given that the
   IP segments of the network may reach the edges of the network, which
   are more likely to involve interaction with potentially malevolent
   outside actors.  Conversely MPLS is inherently more secure than IP
   since it is internal to routers and it is well-known how to protect
   it from outside influence.

   Another way to look at DetNet IP security is to consider it in the
   light of VPN security; as an industry we have a lot of experience
   with VPNs running through networks with other VPNs, it is well known
   how to secure the network for that.  However for a DetNet we have the
   additional subtlety that any possible interaction of one packet with
   another can have a potentially deleterious effect on the time
   properties of the flows.  So the network must provide sufficient
   isolation between flows, for example by protecting the forwarding
   bandwidth and related resources so that they are available to detnet
   traffic, by whatever means are appropriate for that network's data
   plane.




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   In a VPN, bandwidth is generally guaranteed over a period of time,
   whereas in DetNet it is not aggregated over time.  This implies that
   any VPN-type protection mechanism must also maintain the DetNet
   timing constraints.

9.2.  MPLS

   An MPLS network carrying DetNet traffic is expected to be a "well-
   managed" network.  Given that this is the case, it is difficult for
   an attacker to pass a raw MPLS encoded packet into a network because
   operators have considerable experience at excluding such packets at
   the network boundaries, as well as excluding MPLS packets being
   inserted through the use of a tunnel.

   MPLS security is discussed extensively in [RFC5920] ("Security
   Framework for MPLS and GMPLS Networks") to which the reader is
   referred.

   [RFC6941] builds on [RFC5920] by providing additional security
   considerations that are applicable to the MPLS-TP extensions
   appropriate to the MPLS Transport Profile [RFC5921], and thus to the
   operation of DetNet over some types of MPLS network.

   [RFC5921] introduces to MPLS new Operations, Administration, and
   Maintenance (OAM) capabilities, a transport-oriented path protection
   mechanism, and strong emphasis on static provisioning supported by
   network management systems.

   The operation of DetNet over an MPLS network is modeled on the
   operation of multi-segment pseudowires (MS-PW).  Thus for guidance on
   securing the DetNet elements of DetNet over MPLS the reader is
   referred to the MS-PW security mechanisms as defined in [RFC4447],
   [RFC3931], [RFC3985], [RFC6073], and [RFC6478].

   Having attended to the conventional aspects of network security it is
   necessary to attend to the dynamic aspects.  The closest experience
   that the IETF has with securing protocols that are sensitive to
   manipulation of delay are the two way time transfer protocols (TWTT),
   which are NTP [RFC5905] and Precision Time Protocol [IEEE1588].  The
   security requirements for these are described in [RFC7384].

   One particular problem that has been observed in operational tests of
   TWTT protocols is the ability for two closely but not completely
   synchronized flows to beat and cause a sudden phase hit to one of the
   flows.  This can be mitigated by the careful use of a scheduling
   system in the underlying packet transport.





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   Further consideration of protection against dynamic attacks is work
   in progress.

10.  IANA Considerations

   This memo includes no requests from IANA.

11.  Security Considerations

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

12.  Contributors

   The Editor would like to recognize the contributions of the following
   individuals to this draft.



































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       Andrew J. Hacker (MistIQ Technologies, Inc)
       Harrisburg, PA, USA
       email ajhacker@mistiqtech.com,
       web http://www.mistiqtech.com

       Subir Das (Applied Communication Sciences)
       150 Mount Airy Road, Basking Ridge
       New Jersey, 07920, USA
       email sdas@appcomsci.com

       John Dowdell (Airbus Defence and Space)
       Celtic Springs, Newport, NP10 8FZ, United Kingdom
       email john.dowdell.ietf@gmail.com

       Henrik Austad (SINTEF Digital)
       Klaebuveien 153, Trondheim, 7037, Norway
       email henrik@austad.us

       Norman Finn
       email nfinn@nfinnconsulting.com

       Stewart Bryant
       Futurewei Technologies
       email: stewart.bryant@gmail.com

       David Black
       Dell EMC
       176 South Street, Hopkinton, MA  01748, USA
       email: david.black@dell.com

       Carsten Bormann


13.  Informative References

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

   [I-D.ietf-detnet-data-plane-framework]
              Varga, B., Farkas, J., Berger, L., Malis, A., and S.
              Bryant, "DetNet Data Plane Framework", draft-ietf-detnet-
              data-plane-framework-06 (work in progress), May 2020.

   [I-D.ietf-detnet-flow-information-model]
              Varga, B., Farkas, J., Cummings, R., Jiang, Y., and D.
              Fedyk, "DetNet Flow Information Model", draft-ietf-detnet-
              flow-information-model-10 (work in progress), May 2020.



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   [I-D.ietf-detnet-ip]
              Varga, B., Farkas, J., Berger, L., Fedyk, D., and S.
              Bryant, "DetNet Data Plane: IP", draft-ietf-detnet-ip-06
              (work in progress), April 2020.

   [I-D.ietf-detnet-ip-over-tsn]
              Varga, B., Farkas, J., Malis, A., and S. Bryant, "DetNet
              Data Plane: IP over IEEE 802.1 Time Sensitive Networking
              (TSN)", draft-ietf-detnet-ip-over-tsn-02 (work in
              progress), March 2020.

   [I-D.ietf-detnet-mpls]
              Varga, B., Farkas, J., Berger, L., Malis, A., Bryant, S.,
              and J. Korhonen, "DetNet Data Plane: MPLS", draft-ietf-
              detnet-mpls-06 (work in progress), April 2020.

   [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.

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

   [IEEE802.1AE-2018]
              IEEE Standards Association, "IEEE Std 802.1AE-2018 MAC
              Security (MACsec)", 2018,
              <https://ieeexplore.ieee.org/document/8585421>.

   [IEEE802.1Qch-2017]
              IEEE Standards Association, "IEEE Standard for Local and
              metropolitan area networks--Bridges and Bridged Networks--
              Amendment 29: Cyclic Queuing and Forwarding", 2017,
              <https://ieeexplore.ieee.org/document/7961303>.

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

   [RFC2474]  Nichols, K., Blake, S., Baker, F., and D. Black,
              "Definition of the Differentiated Services Field (DS
              Field) in the IPv4 and IPv6 Headers", RFC 2474,
              DOI 10.17487/RFC2474, December 1998,
              <https://www.rfc-editor.org/info/rfc2474>.





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   [RFC2475]  Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
              and W. Weiss, "An Architecture for Differentiated
              Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
              <https://www.rfc-editor.org/info/rfc2475>.

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552,
              DOI 10.17487/RFC3552, July 2003,
              <https://www.rfc-editor.org/info/rfc3552>.

   [RFC3931]  Lau, J., Ed., Townsley, M., Ed., and I. Goyret, Ed.,
              "Layer Two Tunneling Protocol - Version 3 (L2TPv3)",
              RFC 3931, DOI 10.17487/RFC3931, March 2005,
              <https://www.rfc-editor.org/info/rfc3931>.

   [RFC3985]  Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
              Edge-to-Edge (PWE3) Architecture", RFC 3985,
              DOI 10.17487/RFC3985, March 2005,
              <https://www.rfc-editor.org/info/rfc3985>.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <https://www.rfc-editor.org/info/rfc4301>.

   [RFC4447]  Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and
              G. Heron, "Pseudowire Setup and Maintenance Using the
              Label Distribution Protocol (LDP)", RFC 4447,
              DOI 10.17487/RFC4447, April 2006,
              <https://www.rfc-editor.org/info/rfc4447>.

   [RFC5905]  Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
              "Network Time Protocol Version 4: Protocol and Algorithms
              Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
              <https://www.rfc-editor.org/info/rfc5905>.

   [RFC5920]  Fang, L., Ed., "Security Framework for MPLS and GMPLS
              Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
              <https://www.rfc-editor.org/info/rfc5920>.

   [RFC5921]  Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau,
              L., and L. Berger, "A Framework for MPLS in Transport
              Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010,
              <https://www.rfc-editor.org/info/rfc5921>.

   [RFC6073]  Martini, L., Metz, C., Nadeau, T., Bocci, M., and M.
              Aissaoui, "Segmented Pseudowire", RFC 6073,
              DOI 10.17487/RFC6073, January 2011,
              <https://www.rfc-editor.org/info/rfc6073>.



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   [RFC6478]  Martini, L., Swallow, G., Heron, G., and M. Bocci,
              "Pseudowire Status for Static Pseudowires", RFC 6478,
              DOI 10.17487/RFC6478, May 2012,
              <https://www.rfc-editor.org/info/rfc6478>.

   [RFC6941]  Fang, L., Ed., Niven-Jenkins, B., Ed., Mansfield, S., Ed.,
              and R. Graveman, Ed., "MPLS Transport Profile (MPLS-TP)
              Security Framework", RFC 6941, DOI 10.17487/RFC6941, April
              2013, <https://www.rfc-editor.org/info/rfc6941>.

   [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>.

   [RFC8578]  Grossman, E., Ed., "Deterministic Networking Use Cases",
              RFC 8578, DOI 10.17487/RFC8578, May 2019,
              <https://www.rfc-editor.org/info/rfc8578>.

   [RFC8655]  Finn, N., Thubert, P., Varga, B., and J. Farkas,
              "Deterministic Networking Architecture", RFC 8655,
              DOI 10.17487/RFC8655, October 2019,
              <https://www.rfc-editor.org/info/rfc8655>.

Authors' Addresses

   Tal Mizrahi
   Huawei Network.IO Innovation Lab

   Email: tal.mizrahi.phd@gmail.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











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