Internet Engineering Task Force                         E. Grossman, Ed.
Internet-Draft                                                     DOLBY
Intended status: Informational                                T. Mizrahi
Expires: April 5, 2021                                            HUAWEI
                                                               A. Hacker
                                                         October 2, 2020

       Deterministic Networking (DetNet) Security Considerations


   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 requires that in
   addition to the best practice security measures taken for any
   mission-critical network, additional security measures may be needed
   to secure the intended operation of these novel service properties.

   This document addresses DetNet-specific security considerations from
   the perspectives of both the DetNet system-level designer and
   component designer.  System considerations include a threat model,
   taxonomy of relevant attacks, and associations of threats versus use
   cases and service properties.  Component-level considerations include
   ingress filtering and packet arrival time violation detection.  This
   document also addresses DetNet security considerations specific to
   the IP and MPLS data plane technologies 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

   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 April 5, 2021.

Grossman, et al.          Expires April 5, 2021                 [Page 1]

Internet-Draft               DetNet Security                October 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
   ( 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 and Terminology . . . . . . . . . . . . . . . .   6
   3.  Security Considerations for DetNet Component Design . . . . .   6
     3.1.  Resource Allocation . . . . . . . . . . . . . . . . . . .   7
     3.2.  Explicit Routes . . . . . . . . . . . . . . . . . . . . .   7
     3.3.  Redundant Path Support  . . . . . . . . . . . . . . . . .   8
     3.4.  Timing (or other) Violation Reporting . . . . . . . . . .   9
   4.  DetNet Security Considerations Compared With DiffServ
       Security Considerations . . . . . . . . . . . . . . . . . . .   9
   5.  Security Threats  . . . . . . . . . . . . . . . . . . . . . .  10
     5.1.  Threat Model  . . . . . . . . . . . . . . . . . . . . . .  11
     5.2.  Threat Analysis . . . . . . . . . . . . . . . . . . . . .  12
       5.2.1.  Delay . . . . . . . . . . . . . . . . . . . . . . . .  12
       5.2.2.  DetNet Flow Modification or Spoofing  . . . . . . . .  12
       5.2.3.  Resource Segmentation (Inter-segment Attack)  . . . .  12
       5.2.4.  Packet Replication and Elimination  . . . . . . . . .  12  Replication: Increased Attack Surface . . . . . .  12  Replication-related Header Manipulation . . . . .  12
       5.2.5.  Controller Plane  . . . . . . . . . . . . . . . . . .  13  Path Choice Manipulation  . . . . . . . . . . . .  13  Compromised Controller  . . . . . . . . . . . . .  14
       5.2.6.  Reconnaissance  . . . . . . . . . . . . . . . . . . .  14
       5.2.7.  Time Synchronization Mechanisms . . . . . . . . . . .  14
     5.3.  Threat Summary  . . . . . . . . . . . . . . . . . . . . .  14
   6.  Security Threat Impacts . . . . . . . . . . . . . . . . . . .  15
     6.1.  Delay-Attacks . . . . . . . . . . . . . . . . . . . . . .  18
       6.1.1.  Data Plane Delay Attacks  . . . . . . . . . . . . . .  18
       6.1.2.  Controller Plane Delay Attacks  . . . . . . . . . . .  19
     6.2.  Flow Modification and Spoofing  . . . . . . . . . . . . .  19
       6.2.1.  Flow Modification . . . . . . . . . . . . . . . . . .  19
       6.2.2.  Spoofing  . . . . . . . . . . . . . . . . . . . . . .  19

Grossman, et al.          Expires April 5, 2021                 [Page 2]

Internet-Draft               DetNet Security                October 2020

  Dataplane Spoofing  . . . . . . . . . . . . . . .  19  Controller Plane Spoofing . . . . . . . . . . . .  20
     6.3.  Segmentation Attacks (injection)  . . . . . . . . . . . .  20
       6.3.1.  Data Plane Segmentation . . . . . . . . . . . . . . .  20
       6.3.2.  Controller Plane Segmentation . . . . . . . . . . . .  20
     6.4.  Replication and Elimination . . . . . . . . . . . . . . .  21
       6.4.1.  Increased Attack Surface  . . . . . . . . . . . . . .  21
       6.4.2.  Header Manipulation at Elimination Routers  . . . . .  21
     6.5.  Control or Signaling Packet Modification  . . . . . . . .  21
     6.6.  Control or Signaling Packet Injection . . . . . . . . . .  21
     6.7.  Reconnaissance  . . . . . . . . . . . . . . . . . . . . .  21
     6.8.  Attacks on Time Sync Mechanisms . . . . . . . . . . . . .  22
     6.9.  Attacks on Path Choice  . . . . . . . . . . . . . . . . .  22
   7.  Security Threat Mitigation  . . . . . . . . . . . . . . . . .  22
     7.1.  Path Redundancy . . . . . . . . . . . . . . . . . . . . .  22
     7.2.  Integrity Protection  . . . . . . . . . . . . . . . . . .  22
     7.3.  DetNet Node Authentication  . . . . . . . . . . . . . . .  23
     7.4.  Dummy Traffic Insertion . . . . . . . . . . . . . . . . .  24
     7.5.  Encryption  . . . . . . . . . . . . . . . . . . . . . . .  24
       7.5.1.  Encryption Considerations for DetNet  . . . . . . . .  24
     7.6.  Control and Signaling Message Protection  . . . . . . . .  25
     7.7.  Dynamic Performance Analytics . . . . . . . . . . . . . .  26
     7.8.  Mitigation Summary  . . . . . . . . . . . . . . . . . . .  27
   8.  Association of Attacks to Use Cases . . . . . . . . . . . . .  28
     8.1.  Association of Attacks to Use Case Common Themes  . . . .  28
       8.1.1.  Sub-Network Layer . . . . . . . . . . . . . . . . . .  28
       8.1.2.  Central Administration  . . . . . . . . . . . . . . .  29
       8.1.3.  Hot Swap  . . . . . . . . . . . . . . . . . . . . . .  29
       8.1.4.  Data Flow Information Models  . . . . . . . . . . . .  30
       8.1.5.  L2 and L3 Integration . . . . . . . . . . . . . . . .  30
       8.1.6.  End-to-End Delivery . . . . . . . . . . . . . . . . .  30
       8.1.7.  Replacement for Proprietary Fieldbuses and Ethernet-
               based Networks  . . . . . . . . . . . . . . . . . . .  31
       8.1.8.  Deterministic vs Best-Effort Traffic  . . . . . . . .  31
       8.1.9.  Deterministic Flows . . . . . . . . . . . . . . . . .  32
       8.1.10. Unused Reserved Bandwidth . . . . . . . . . . . . . .  32
       8.1.11. Interoperability  . . . . . . . . . . . . . . . . . .  32
       8.1.12. Cost Reductions . . . . . . . . . . . . . . . . . . .  32
       8.1.13. Insufficiently Secure Devices . . . . . . . . . . . .  33
       8.1.14. DetNet Network Size . . . . . . . . . . . . . . . . .  33
       8.1.15. Multiple Hops . . . . . . . . . . . . . . . . . . . .  34
       8.1.16. Level of Service  . . . . . . . . . . . . . . . . . .  34
       8.1.17. Bounded Latency . . . . . . . . . . . . . . . . . . .  34
       8.1.18. Low Latency . . . . . . . . . . . . . . . . . . . . .  35
       8.1.19. Bounded Jitter (Latency Variation)  . . . . . . . . .  35
       8.1.20. Symmetrical Path Delays . . . . . . . . . . . . . . .  35
       8.1.21. Reliability and Availability  . . . . . . . . . . . .  35
       8.1.22. Redundant Paths . . . . . . . . . . . . . . . . . . .  36

Grossman, et al.          Expires April 5, 2021                 [Page 3]

Internet-Draft               DetNet Security                October 2020

       8.1.23. Security Measures . . . . . . . . . . . . . . . . . .  36
     8.2.  Summary of Attack Types per Use Case Common Theme . . . .  36
     8.3.  Security Considerations for OAM Traffic . . . . . . . . .  39
   9.  DetNet Technology-Specific Threats  . . . . . . . . . . . . .  39
     9.1.  IP  . . . . . . . . . . . . . . . . . . . . . . . . . . .  40
     9.2.  MPLS  . . . . . . . . . . . . . . . . . . . . . . . . . .  41
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  42
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  42
   12. Privacy Considerations  . . . . . . . . . . . . . . . . . . .  42
   13. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  42
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  43
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  43
     14.2.  Informative References . . . . . . . . . . . . . . . . .  44
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  47

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, [RFC8655]) specifies a set of
   technologies that enable creation of deterministic networks on IP-
   based networks of potentially wide area (on the scale of a corporate
   network) potentially bringing the OT network into contact with
   Information Technology (IT) traffic and security threats that lie
   outside of a tightly controlled and bounded area (such as the
   internals of an aircraft).

   These DetNet technologies have not previously been deployed together
   on a wide area IP-based network, and thus can present security
   considerations that may be new to IP-based wide area network
   designers; this 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.

Grossman, et al.          Expires April 5, 2021                 [Page 4]

Internet-Draft               DetNet Security                October 2020

   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.

   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 DetNet Data Plane
   [I-D.ietf-detnet-data-plane-framework] and 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

Grossman, et al.          Expires April 5, 2021                 [Page 5]

Internet-Draft               DetNet Security                October 2020

   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

   This document includes sections considering DetNet component design
   as well as system design.  The latter includes 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 [RFC8578]).

   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 and Terminology

   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 - [IT_DEF]).

   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. - [OT_DEF])

   Component       A component of a DetNet system - used here to refer
   to any hardware or software element of a DetNet network which
   implements DetNet-specific functionality, for example all or part of
   a router, switch, or end system.

   Resource Segmentation       Used as a more general form for Network
   Segmentation (the act or practice of splitting a computer network
   into subnetworks, each being a network segment - [RS_DEF])

3.  Security Considerations for DetNet Component Design

   As noted above, DetNet provides resource allocation, explicit routes
   and redundant path support.  Each of these has 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.

Grossman, et al.          Expires April 5, 2021                 [Page 6]

Internet-Draft               DetNet Security                October 2020

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, for example through the use of
   traffic shaping and policing.

   As an example, consider the implementation of Flow Aggregation for
   DetNet flows (as discussed in
   [I-D.ietf-detnet-data-plane-framework]).  In this example say there
   are N flows that are to be aggregated, thus the bandwidth resources
   of the aggregate flow must be sufficient to contain the sum of the
   bandwidth reservation for the N flows.  However if one of those flows
   were to consume more than its individually allocated BW, this could
   cause starvation of the other flows.  Thus simply providing and
   enforcing the calculated aggregate bandwidth may not be a complete
   solution - the bandwidth for each individual flow must still be
   guaranteed, for example via ingress policing of each flow (i.e.
   before it is aggregated).  Alternatively, if by some other means each
   flow to be aggregated can be trusted not to exceed its allocated
   bandwidth, the same goal can be achieved.

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, it 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

Grossman, et al.          Expires April 5, 2021                 [Page 7]

Internet-Draft               DetNet Security                October 2020

   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
   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, to avoid potentially catastrophic
   situations for the operational technology relying on them.

   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.

   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 (including
   elimination of packets with spurious sequence numbers).  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.  This is no different than
   the integrity of the values in any header used by the DetNet (or any

Grossman, et al.          Expires April 5, 2021                 [Page 8]

Internet-Draft               DetNet Security                October 2020

   other) data plane, and is not unique to redundant paths.  From the
   sequence number injection perspective, it is no different from any
   other protocols that use sequence numbers.

3.4.  Timing (or other) Violation Reporting

   Another fundamental assumption of a secure DetNet is that in any case
   in which an incoming packet arrives with any timing or bandwidth
   violation, something can be done about it which doesn't cause damage
   to the system.  For example having the network shut down a link if a
   packet arrives outside of its prescribed time window may serve the
   attacker better than it serves the network.  That means that the
   component's data plane must be able to detect and act on a variety of
   such violations, at least alerting the controller plane.  Any action
   apart from that needs to be carefully considered in the context of
   the specific system.  Some possible violations that warrant detection
   include cases where a packet arrives:

   o  Outside of its prescribed time window

   o  Within its time window but with a compromised time stamp that
      makes it appear that it is not within its window

   o  Exceeding the reserved flow bandwidth

   Logging of such issues is unlikely to be adequate, since a delay in
   response to the situation could result in material damage, for
   example to mechanical devices controlled by the network.  Given that
   the data plane component probably has no knowledge of the use case of
   the network, or its applications and end systems, it would seem
   useful for a data plane component to allow the system designer to
   configure its actions in the face of such violations.

   Possible direct actions that may be taken at the data plane include
   dropping the packet and/or shutting down the link; however if any
   such actions are configured to be taken, the system designer must
   ensure that such actions do not compromise the continued safe
   operation of the system.  For example, the controller plane should
   mitigate in a timely fashion any potential adverse effect on
   mechanical devices controlled by the network.

4.  DetNet Security Considerations Compared With DiffServ Security

   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

Grossman, et al.          Expires April 5, 2021                 [Page 9]

Internet-Draft               DetNet Security                October 2020

   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 introduces
   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
   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

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

   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

Grossman, et al.          Expires April 5, 2021                [Page 10]

Internet-Draft               DetNet Security                October 2020

   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 employs organizational elements of
   the threat models of [RFC7384] and [RFC7835] . 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  On-path vs. off-path: on-path attackers are located in a position
      that allows interception and modification of in-flight protocol
      packets, whereas off-path attackers 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 (i.e. attacks that modify
   DetNet traffic), but it is highly suggested that DetNet application
   developers take appropriate measures to protect the content of the
   DetNet flows from passive attacks (i.e. attacks that observe but do
   not modify DetNet traffic) for example through the use of TLS or

   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

Grossman, et al.          Expires April 5, 2021                [Page 11]

Internet-Draft               DetNet Security                October 2020

5.2.  Threat Analysis

5.2.1.  Delay

   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 (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.

5.2.4.  Packet Replication and Elimination  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.  Replication-related Header Manipulation

   An attacker can manipulate the replication-related header fields.
   This capability opens the door for various types of attacks.  For

   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.

Grossman, et al.          Expires April 5, 2021                [Page 12]

Internet-Draft               DetNet Security                October 2020

   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

   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.

   o  Amplification - an attacker who injects packets into a flow that
      is to be replicated will have their attack amplified through the
      replication process.  This is no different than any attacker who
      injects packets that are delivered through multicast, broadcast,
      or other point-to-multi-point mechanisms.

5.2.5.  Controller Plane  Path Choice Manipulation  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.  Control or Signaling Packet Injection

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

Grossman, et al.          Expires April 5, 2021                [Page 13]

Internet-Draft               DetNet Security                October 2020  Compromised Controller

   An attacker can subvert a controller, or enable a compromised
   controller to falsely represent itself as a controller so that the
   network nodes believe it to be authorized to instruct them.

   Presence of compromised nodes in a DetNet is not a "new" threat that
   arises as a result of determinism or time sensitivity; the same
   techniques used to prevent or mitigate against compromised nodes in
   any network are equally applicable in the DetNet case.  However this
   underscores the requirement for careful system security design in a
   DetNet, given that the effects of even one bad actor on the network
   can be potentially catastrophic.

   Security concerns specific to any given controller plane technology
   used in DetNet will be addressed by the DetNet documents associated
   with that technology.

5.2.6.  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 the purposes of this document we assume they are
   encrypted and/or integrity-protected from external attackers.

5.2.7.  Time Synchronization Mechanisms

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

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

Grossman, et al.          Expires April 5, 2021                [Page 14]

Internet-Draft               DetNet Security                October 2020

   | Attack                                  |   Attacker Type   |
   |                                         +---------+---------+
   |                                         |Internal |External |
   |                                         |On-P|Off-P|On-P|Off-P|
   |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

   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.

   DetNet raises these stakes significantly for OT applications,
   particularly those which may have been designed to run in an OT-only

Grossman, et al.          Expires April 5, 2021                [Page 15]

Internet-Draft               DetNet Security                October 2020

   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 the DetNet Use Cases [RFC8578].  Each of these 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
   |  Financial       | Med   | Hi   | Med  | Med  | Low  | Med | Med |

Grossman, et al.          Expires April 5, 2021                [Page 16]

Internet-Draft               DetNet Security                October 2020

   |  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 |
   |  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      |

Grossman, et al.          Expires April 5, 2021                [Page 17]

Internet-Draft               DetNet Security                October 2020

   |  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.

Grossman, et al.          Expires April 5, 2021                [Page 18]

Internet-Draft               DetNet Security                October 2020

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  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

Grossman, et al.          Expires April 5, 2021                [Page 19]

Internet-Draft               DetNet Security                October 2020  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

   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

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

   o  create new DetNet flows (exhausting resources)

   o  drop existing DetNet flows (denial of service)

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

   o  remove end-stations from a multicast group (reduction of service)

Grossman, et al.          Expires April 5, 2021                [Page 20]

Internet-Draft               DetNet Security                October 2020

   o  modify the DetNet flow attributes (affecting available bandwidth)

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

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

Grossman, et al.          Expires April 5, 2021                [Page 21]

Internet-Draft               DetNet Security                October 2020

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


      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 on-path attacks.  Note:
      At the time of this writing, PREOF is not defined for the IP data

   Related attacks

      Path redundancy can be used to mitigate various on-path attacks,
      including attacks described in Section 5.2.1, Section 5.2.2,
      Section 5.2.3, and Section 5.2.7.  However it is also possible
      that multiple paths may make it more difficult to locate the
      source of an on-path 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


Grossman, et al.          Expires April 5, 2021                [Page 22]

Internet-Draft               DetNet Security                October 2020

      An integrity protection mechanism, such as a hash-based Message
      Authentication Code (MAC) can be used to mitigate modification
      attacks on IP packets.  Such MAC usage needs to be part of a
      security association that is established and managed by a security
      association protocol (such as IKEv2 for IPsec security
      associations).  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


      Authentication verifies the identity of DetNet nodes (including
      DetNet Controller Plane nodes), enabling mitigation of spoofing
      attacks.  Note that while integrity protection (Section 7.2)
      prevents intermediate nodes from modifying information,
      authentication (such as provided by IPsec or MACsec) can provide
      traffic origin verification, i.e. to verify that each packet in a
      DetNet flow is from a trusted source.

   Related attacks

Grossman, et al.          Expires April 5, 2021                [Page 23]

Internet-Draft               DetNet Security                October 2020

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

7.4.  Dummy Traffic Insertion


      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 5.2.6.

7.5.  Encryption


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

      DetNet nodes do not have any need to inspect the payload of any
      DetNet packets, making them data-agnostic.  This means that end-
      to- end encryption at the application layer is an acceptable way
      to protect user data.

      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 5.2.6).
      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

Grossman, et al.          Expires April 5, 2021                [Page 24]

Internet-Draft               DetNet Security                October 2020

   bounded worst-case execution times, and these values must be used in
   the latency calculations.

   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

   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


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

Grossman, et al.          Expires April 5, 2021                [Page 25]

Internet-Draft               DetNet Security                October 2020

   Related attacks

      These mechanisms can be used to mitigate various attacks on the
      controller plane, as described in Section 5.2.5, Section 5.2.7 and

7.7.  Dynamic Performance Analytics


      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

      If the monitoring or reporting mechanism itself is attacked or
      subverted, this can result in malfunction of the network.  The
      design of the monitoring system needs to take this into account
      based on the specifics of the monitoring or reporting system being

   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 5.2.7
      (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.

Grossman, et al.          Expires April 5, 2021                [Page 26]

Internet-Draft               DetNet Security                October 2020

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.

   | 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   |                     |

Grossman, et al.          Expires April 5, 2021                [Page 27]

Internet-Draft               DetNet Security                October 2020

   |                      | 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     |
   |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.  Association of Attacks to Use Case 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.

Grossman, et al.          Expires April 5, 2021                [Page 28]

Internet-Draft               DetNet Security                October 2020

   With respect to mitigations, some methods are specific to the
   Ethernet medium, for example time-aware scheduling using 802.1Qbv
   [IEEE802.1Qbv-2015] can protect against excessive use of bandwidth at
   the ingress - for other mediums, other mitigations would have to be
   implemented to provide analogous protection.

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

   All attacks named in this document which are relevant to controller
   plane packets (and the controller itself) are 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

   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

   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

Grossman, et al.          Expires April 5, 2021                [Page 29]

Internet-Draft               DetNet Security                October 2020

   should be considered when designing hot swap type functionality (see

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

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 Pseudowire, and Ethernet.

   There are no specific entries in the mapping table Figure 4, 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 on-path
   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

Grossman, et al.          Expires April 5, 2021                [Page 30]

Internet-Draft               DetNet Security                October 2020

8.1.7.  Replacement for Proprietary Fieldbuses and Ethernet-based

   There are many proprietary "field buses" used in today's industrial
   and other industries, as well as proprietary non-interoperable
   deterministic Ethernet-based networks.  DetNet is intended to provide
   an open-standards-based alternative to such buses/networks.  In cases
   where a DetNet intersects with such fieldbuses/networks 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

8.1.8.  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

   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.

Grossman, et al.          Expires April 5, 2021                [Page 31]

Internet-Draft               DetNet Security                October 2020

8.1.9.  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.

8.1.10.  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.

8.1.11.  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.

8.1.12.  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.

   This envisioned breadth of DetNet-enabled products is in general a
   positive factor, however implementation flaws in any individual
   component can present an attack surface.  In addition, implementation
   differences between components from different vendors can result in

Grossman, et al.          Expires April 5, 2021                [Page 32]

Internet-Draft               DetNet Security                October 2020

   attack surfaces (resulting from their interaction) which may not
   exist in any individual component.

   Network operators can mitigate such concerns through sufficient
   product and interoperability testing.

8.1.13.  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.  However this raises the possibility that a
   vendor might repurpose for DetNet applications a hardware or software
   component that was originally designed for operation in an isolated
   OT network, and thus may not have been designed to be sufficiently
   secure, or secure at all.  Deployment of such a device on a DetNet
   network that is intended to be highly secure may present an attack

   The DetNet network operator may need to take specific actions to
   protect such devices, such as implementing a dedicated security layer
   around the device.

8.1.14.  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

   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

Grossman, et al.          Expires April 5, 2021                [Page 33]

Internet-Draft               DetNet Security                October 2020

8.1.15.  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) 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 tested through extensive
   use, particularly in the case of early adopters.

   Of the attacks we have defined, the ones identified in Section 8.1.14
   as germane to large networks are the most relevant.

8.1.16.  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

   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 in
   Section 6.7.

8.1.17.  Bounded Latency

   DetNet provides the expectation of guaranteed bounded latency.

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

Grossman, et al.          Expires April 5, 2021                [Page 34]

Internet-Draft               DetNet Security                October 2020

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

8.1.18.  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 Section 8.1.16) and Delay and Time attacks (as described in the
   Bounded Latency theme Section 8.1.17) both apply here.

8.1.19.  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.

8.1.20.  Symmetrical Path Delays

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

   Delay attacks can cause path delays to materially differ between

   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

8.1.21.  Reliability and Availability

   DetNet based systems are expected to be implemented with essentially
   arbitrarily high availability (for example 99.9999% up time, or even
   12 nines).  The intent is that the DetNet designs should not make any
   assumptions about the level of reliability and availability that may

Grossman, et al.          Expires April 5, 2021                [Page 35]

Internet-Draft               DetNet Security                October 2020

   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 the mapping table Figure 4 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.

8.1.22.  Redundant Paths

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

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

8.1.23.  Security Measures

   A DetNet network must be made secure against devices failures,
   attackers, misbehaving component, and so on.  If the security
   mechanisms protecting the DetNet are attacked or subverted, this can
   result in malfunction of the network.  The design of the security
   system itself needs to take this into account based on the specifics
   of the security system being considered.  The general topic of
   protection of security mechanisms is not unique to DetNet; it is
   identical to the case of securing any security mechanism for any
   network.  The text of this document addresses these concerns to the
   extent that they are relevant to DetNet.

8.2.  Summary of Attack Types per Use Case Common Theme

   The List of Attacks table Figure 4 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.

Grossman, et al.          Expires April 5, 2021                [Page 36]

Internet-Draft               DetNet Security                October 2020

   |    | Attack                                 |
   |  1 |Delay Attack                            |
   |  2 |DetNet Flow Modification or Spoofing    |
   |  3 |Inter-Segment Attack                    |
   |  4 |Replication: Increased attack surface   |
   |  5 |Replication-related Header Manipulation |
   |  6 |Path Manipulation                       |
   |  7 |Path Choice: Increased Attack Surface   |
   |  8 |Control or Signaling Packet Modification|
   |  9 |Control or Signaling Packet Injection   |
   | 10 |Reconnaissance                          |
   | 11 |Attacks on Time Sync Mechanisms         |

                         Figure 4: List of Attacks

   The Mapping Between Themes and Attacks table Figure 5 maps the use
   case themes of [RFC8578] (as also enumerated in this document) to the
   attacks of Figure 4.  Each row specifies a theme, and the attacks
   relevant to this theme are marked with a '+'.  The row items which
   have no threats associated with them are included in the table for
   completeness of the list of Use Case Common Themes, and do not have
   DetNet-specific threats associated with them.

   | Theme                      |             Attack             |
   |                            +--+--+--+--+--+--+--+--+--+--+--+
   |                            | 1| 2| 3| 4| 5| 6| 7| 8| 9|10|11|
   |Network Layer - AVB/TSN Eth.| +| +| +| +| +| +| +| +| +| +| +|
   |Central Administration      |  |  |  |  |  | +| +| +| +| +| +|
   |Hot Swap                    |  | +| +|  |  |  |  |  |  |  | +|

Grossman, et al.          Expires April 5, 2021                [Page 37]

Internet-Draft               DetNet Security                October 2020

   |Data Flow Information Models|  |  |  |  |  |  |  |  |  |  |  |
   |L2 and L3 Integration       |  |  |  |  |  |  |  |  |  |  |  |
   |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

Grossman, et al.          Expires April 5, 2021                [Page 38]

Internet-Draft               DetNet Security                October 2020

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 the
   purposes of this discussion, OAM traffic falls into one of two basic

   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.

   From the perspective of an attack, OAM traffic is indistinguishable
   from DetNet traffic and the network needs to be secure against
   injection, removal, or modification of traffic of any kind, including
   OAM traffic.  A DetNet is sensitive to any form of packet injection,
   removal or manipulation and in this respect DetNet OAM traffic is no
   different.  Techniques for securing a DetNet against these threats
   have been discussed elsewhere in this document.

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

   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,

Grossman, et al.          Expires April 5, 2021                [Page 39]

Internet-Draft               DetNet Security                October 2020

   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.

   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

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, so the
   carriage of DetNet traffic over an IP 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

   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

Grossman, et al.          Expires April 5, 2021                [Page 40]

Internet-Draft               DetNet Security                October 2020

   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, for example through the use of queueing mechanisms.

   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

   [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

Grossman, et al.          Expires April 5, 2021                [Page 41]

Internet-Draft               DetNet Security                October 2020

   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.

   Further consideration of protection against dynamic attacks is work
   in progress.  New work on MPLS security may also be applicable, for
   example [I-D.ietf-mpls-opportunistic-encrypt].

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.  Privacy Considerations

   Privacy in the context of DetNet is maintained by the base
   technologies specific to the DetNet and user traffic.  For example
   TSN can use MACsec, IP can use IPsec, applications can use IP
   transport protocol-provided methods e.g.  TLS and DTLS.  MPLS
   typically uses L2/L3 VPNs combined with the previously mentioned
   privacy methods.

13.  Contributors

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

Grossman, et al.          Expires April 5, 2021                [Page 42]

Internet-Draft               DetNet Security                October 2020

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

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

       Henrik Austad (SINTEF Digital)
       Klaebuveien 153, Trondheim, 7037, Norway

       Norman Finn

       Stewart Bryant
       Futurewei Technologies

       David Black
       Dell EMC
       176 South Street, Hopkinton, MA  01748, USA

       Carsten Bormann

14.  References

14.1.  Normative References

              Varga, B., Farkas, J., Berger, L., Fedyk, D., and S.
              Bryant, "DetNet Data Plane: IP", draft-ietf-detnet-ip-07
              (work in progress), July 2020.

              Varga, B., Farkas, J., Berger, L., Malis, A., Bryant, S.,
              and J. Korhonen, "DetNet Data Plane: MPLS", draft-ietf-
              detnet-mpls-12 (work in progress), September 2020.

   [RFC8655]  Finn, N., Thubert, P., Varga, B., and J. Farkas,
              "Deterministic Networking Architecture", RFC 8655,
              DOI 10.17487/RFC8655, October 2019,

Grossman, et al.          Expires April 5, 2021                [Page 43]

Internet-Draft               DetNet Security                October 2020

14.2.  Informative References

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

              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.

              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.

              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-03 (work in
              progress), June 2020.

              Farrel, A. and S. Farrell, "Opportunistic Security in MPLS
              Networks", draft-ietf-mpls-opportunistic-encrypt-03 (work
              in progress), March 2017.

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

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

              IEEE Standards Association, "IEEE Std 802.1AE-2018 MAC
              Security (MACsec)", 2018,

              IEEE Standards Association, "IEEE Standard for Local and
              metropolitan area networks -- Bridges and Bridged Networks
              - Amendment 25: Enhancements for Scheduled Traffic", 2015,

Grossman, et al.          Expires April 5, 2021                [Page 44]

Internet-Draft               DetNet Security                October 2020

              IEEE Standards Association, "IEEE Standard for Local and
              metropolitan area networks--Bridges and Bridged Networks--
              Amendment 29: Cyclic Queuing and Forwarding", 2017,

   [IT_DEF]   Wikipedia, "IT Definition", 2020,

   [OT_DEF]   Wikipedia, "OT Definition", 2020,

   [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,

   [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,

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552,
              DOI 10.17487/RFC3552, July 2003,

   [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,

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

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <>.

   [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,

Grossman, et al.          Expires April 5, 2021                [Page 45]

Internet-Draft               DetNet Security                October 2020

   [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,

   [RFC5920]  Fang, L., Ed., "Security Framework for MPLS and GMPLS
              Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,

   [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,

   [RFC6073]  Martini, L., Metz, C., Nadeau, T., Bocci, M., and M.
              Aissaoui, "Segmented Pseudowire", RFC 6073,
              DOI 10.17487/RFC6073, January 2011,

   [RFC6478]  Martini, L., Swallow, G., Heron, G., and M. Bocci,
              "Pseudowire Status for Static Pseudowires", RFC 6478,
              DOI 10.17487/RFC6478, May 2012,

   [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, <>.

   [RFC7384]  Mizrahi, T., "Security Requirements of Time Protocols in
              Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384,
              October 2014, <>.

   [RFC7835]  Saucez, D., Iannone, L., and O. Bonaventure, "Locator/ID
              Separation Protocol (LISP) Threat Analysis", RFC 7835,
              DOI 10.17487/RFC7835, April 2016,

   [RFC8578]  Grossman, E., Ed., "Deterministic Networking Use Cases",
              RFC 8578, DOI 10.17487/RFC8578, May 2019,

   [RS_DEF]   Wikipedia, "RS Definition", 2020,

Grossman, et al.          Expires April 5, 2021                [Page 46]

Internet-Draft               DetNet Security                October 2020

Authors' Addresses

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

   Phone: +1 415 465 4339

   Tal Mizrahi
   Huawei Network.IO Innovation Lab


   Andrew  J. Hacker
   MistIQ Technologies, Inc
   Harrisburg, PA


Grossman, et al.          Expires April 5, 2021                [Page 47]