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Versions: (draft-sdt-detnet-security) 00 01 02 03 04 05 06 07 08 09 10 11 12 13

Internet Engineering Task Force                         E. Grossman, Ed.
Internet-Draft                                                     DOLBY
Intended status: Informational                                T. Mizrahi
Expires: June 14, 2021                                            HUAWEI
                                                               A. Hacker
                                                                  MISTIQ
                                                       December 11, 2020


       Deterministic Networking (DetNet) Security Considerations
                     draft-ietf-detnet-security-13

Abstract

   A DetNet (deterministic network) provides specific performance
   guarantees to its data flows, such as extremely low data loss rates
   and bounded latency (including bounded latency variation, i.e.
   "jitter").  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 security considerations specific to the
   IP and MPLS data plane technologies, thereby complementing the
   Security Considerations sections of those documents.

Status of This Memo

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

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

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




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   This Internet-Draft will expire on June 14, 2021.

Copyright Notice

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

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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Abbreviations and Terminology . . . . . . . . . . . . . . . .   6
   3.  Security Considerations for DetNet Component Design . . . . .   7
     3.1.  Resource Allocation . . . . . . . . . . . . . . . . . . .   7
     3.2.  Explicit Routes . . . . . . . . . . . . . . . . . . . . .   8
     3.3.  Redundant Path Support  . . . . . . . . . . . . . . . . .   8
     3.4.  Timing (or other) Violation Reporting . . . . . . . . . .   9
   4.  DetNet Security Considerations Compared With DiffServ
       Security Considerations . . . . . . . . . . . . . . . . . . .  10
   5.  Security Threats  . . . . . . . . . . . . . . . . . . . . . .  11
     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  . . . . . . . . .  13
         5.2.4.1.  Replication: Increased Attack Surface . . . . . .  13
         5.2.4.2.  Replication-related Header Manipulation . . . . .  13
       5.2.5.  Controller Plane  . . . . . . . . . . . . . . . . . .  14
         5.2.5.1.  Path Choice Manipulation  . . . . . . . . . . . .  14
         5.2.5.2.  Compromised Controller  . . . . . . . . . . . . .  14
       5.2.6.  Reconnaissance  . . . . . . . . . . . . . . . . . . .  14
       5.2.7.  Time Synchronization Mechanisms . . . . . . . . . . .  15
     5.3.  Threat Summary  . . . . . . . . . . . . . . . . . . . . .  15
   6.  Security Threat Impacts . . . . . . . . . . . . . . . . . . .  16
     6.1.  Delay-Attacks . . . . . . . . . . . . . . . . . . . . . .  19
       6.1.1.  Data Plane Delay Attacks  . . . . . . . . . . . . . .  19
       6.1.2.  Controller Plane Delay Attacks  . . . . . . . . . . .  20
     6.2.  Flow Modification and Spoofing  . . . . . . . . . . . . .  20



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       6.2.1.  Flow Modification . . . . . . . . . . . . . . . . . .  20
       6.2.2.  Spoofing  . . . . . . . . . . . . . . . . . . . . . .  20
         6.2.2.1.  Dataplane Spoofing  . . . . . . . . . . . . . . .  20
         6.2.2.2.  Controller Plane Spoofing . . . . . . . . . . . .  21
     6.3.  Segmentation Attacks (injection)  . . . . . . . . . . . .  21
       6.3.1.  Data Plane Segmentation . . . . . . . . . . . . . . .  21
       6.3.2.  Controller Plane Segmentation . . . . . . . . . . . .  21
     6.4.  Replication and Elimination . . . . . . . . . . . . . . .  22
       6.4.1.  Increased Attack Surface  . . . . . . . . . . . . . .  22
       6.4.2.  Header Manipulation at Elimination Routers  . . . . .  22
     6.5.  Control or Signaling Packet Modification  . . . . . . . .  22
     6.6.  Control or Signaling Packet Injection . . . . . . . . . .  22
     6.7.  Reconnaissance  . . . . . . . . . . . . . . . . . . . . .  22
     6.8.  Attacks on Time Synchronization Mechanisms  . . . . . . .  23
     6.9.  Attacks on Path Choice  . . . . . . . . . . . . . . . . .  23
   7.  Security Threat Mitigation  . . . . . . . . . . . . . . . . .  23
     7.1.  Path Redundancy . . . . . . . . . . . . . . . . . . . . .  23
     7.2.  Integrity Protection  . . . . . . . . . . . . . . . . . .  24
     7.3.  DetNet Node Authentication  . . . . . . . . . . . . . . .  25
     7.4.  Dummy Traffic Insertion . . . . . . . . . . . . . . . . .  26
     7.5.  Encryption  . . . . . . . . . . . . . . . . . . . . . . .  26
       7.5.1.  Encryption Considerations for DetNet  . . . . . . . .  27
     7.6.  Control and Signaling Message Protection  . . . . . . . .  28
     7.7.  Dynamic Performance Analytics . . . . . . . . . . . . . .  28
     7.8.  Mitigation Summary  . . . . . . . . . . . . . . . . . . .  30
   8.  Association of Attacks to Use Cases . . . . . . . . . . . . .  32
     8.1.  Association of Attacks to Use Case Common Themes  . . . .  32
       8.1.1.  Sub-Network Layer . . . . . . . . . . . . . . . . . .  32
       8.1.2.  Central Administration  . . . . . . . . . . . . . . .  33
       8.1.3.  Hot Swap  . . . . . . . . . . . . . . . . . . . . . .  33
       8.1.4.  Data Flow Information Models  . . . . . . . . . . . .  34
       8.1.5.  L2 and L3 Integration . . . . . . . . . . . . . . . .  34
       8.1.6.  End-to-End Delivery . . . . . . . . . . . . . . . . .  34
       8.1.7.  Replacement for Proprietary Fieldbuses and Ethernet-
               based Networks  . . . . . . . . . . . . . . . . . . .  35
       8.1.8.  Deterministic vs Best-Effort Traffic  . . . . . . . .  35
       8.1.9.  Deterministic Flows . . . . . . . . . . . . . . . . .  36
       8.1.10. Unused Reserved Bandwidth . . . . . . . . . . . . . .  36
       8.1.11. Interoperability  . . . . . . . . . . . . . . . . . .  36
       8.1.12. Cost Reductions . . . . . . . . . . . . . . . . . . .  37
       8.1.13. Insufficiently Secure Components  . . . . . . . . . .  37
       8.1.14. DetNet Network Size . . . . . . . . . . . . . . . . .  37
       8.1.15. Multiple Hops . . . . . . . . . . . . . . . . . . . .  38
       8.1.16. Level of Service  . . . . . . . . . . . . . . . . . .  38
       8.1.17. Bounded Latency . . . . . . . . . . . . . . . . . . .  39
       8.1.18. Low Latency . . . . . . . . . . . . . . . . . . . . .  39
       8.1.19. Bounded Jitter (Latency Variation)  . . . . . . . . .  39
       8.1.20. Symmetrical Path Delays . . . . . . . . . . . . . . .  39



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       8.1.21. Reliability and Availability  . . . . . . . . . . . .  40
       8.1.22. Redundant Paths . . . . . . . . . . . . . . . . . . .  40
       8.1.23. Security Measures . . . . . . . . . . . . . . . . . .  40
     8.2.  Summary of Attack Types per Use Case Common Theme . . . .  41
     8.3.  Security Considerations for OAM Traffic . . . . . . . . .  43
   9.  DetNet Technology-Specific Threats  . . . . . . . . . . . . .  43
     9.1.  IP  . . . . . . . . . . . . . . . . . . . . . . . . . . .  44
     9.2.  MPLS  . . . . . . . . . . . . . . . . . . . . . . . . . .  45
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  46
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  46
   12. Privacy Considerations  . . . . . . . . . . . . . . . . . . .  46
   13. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  46
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  47
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  47
     14.2.  Informative References . . . . . . . . . . . . . . . . .  48
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  52

1.  Introduction

   A DetNet is one that can carry data flows for real-time applications
   with extremely low data loss rates and bounded latency.  The bounds
   on latency defined by DetNet
   ([I-D.ietf-detnet-flow-information-model]) include both worst case
   latency (Maximum Latency, Section 5.9.2) and worst case jitter
   (Maximum Latency Variation, Section 5.9.3).  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 flows 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 (OT-type) technologies may not have previously been
   deployed on a wide area IP-based network that also carries IT
   traffic, 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.




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   Security is of particularly high importance in DetNet because many of
   the use cases which are enabled by DetNet [RFC8578] include control
   of physical devices (power grid devices, industrial controls,
   building controls) which can have high operational costs for failure,
   and present potentially attractive targets for cyber-attackers.

   This situation is even more acute given that one of the goals of
   DetNet is to provide a "converged network", i.e. one that includes
   both IT traffic and OT traffic, thus exposing potentially sensitive
   OT devices to attack in ways that were not previously common (usually
   because they were under a separate control system or otherwise
   isolated from the IT network, for example [ARINC664P7]).  Security
   considerations for OT networks are not a new area, and there are many
   OT networks today that are connected to wide area networks or the
   Internet; this document focuses on the issues that are specific to
   the DetNet technologies and use cases.

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

   In this context we view the "traditional" (i.e. non-time-sensitive)
   network design and management aspects of network security as being
   primarily concerned with denial-of service prevention, i.e. they must
   ensure that DetNet traffic goes where it's supposed to and that an
   external attacker can't inject traffic that disrupts the delivery
   timing assurance of the DetNet.  The time-specific aspects of DetNet
   security presented here take up where those "traditional" design and
   management aspects leave off.

   However note that "traditional" methods for mitigating (among all the
   others) denial-of service attack (such as throttling) can only be
   effectively used in a DetNet when their use does not compromise the
   required time-sensitive or behavioral properties required for the OT
   flows on the network.  For example, a "retry" protocol is typically
   not going to be compatible with a low-latency (worst-case maximum
   latency) requirement, however if in a specific use case and
   implementation such a retry protocol is able to meet the timing
   constraints, then it may well be used in that context.  Similarly if



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   common security protocols such as TLS/DTLS or IPsec are to be used,
   it must be verified that their implementations are able to meet the
   timing and behavioral requirements of the time-sensitive network as
   implemented for the given use case.  An example of "behavioral
   properties" might be that dropping of more than a specific number of
   packets in a row is not acceptable according to the service level
   agreement.

   The exact security requirements for any given DetNet 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
   [RFC8939]).  Readers can find a general introduction to the DetNet
   Architecture in [RFC8655], the DetNet Data Plane in [RFC8938], and
   the Flow Information Model in
   [I-D.ietf-detnet-flow-information-model].

   The DetNet technologies include ways to:

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

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

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

   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]).




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

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

   Device: Used here to refer to a physical entity controlled by the
   DetNet, for example a motor.

   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.

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 [RFC8938]).  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



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   were to consume more than its individually allocated bandwidth, 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 ability of the
   DetNet 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
   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




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   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 for a flow could be specified from end to
   end, 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 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
   other) data plane, and is not unique to redundant paths.  The
   integrity protection of header values is technology-dependent; for
   example, in Layer 2 networks the integrity of the header fields can
   be protected by using MACsec [IEEE802.1AE-2018].  Similary, 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 data
   plane of the component 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




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   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.

   Some possible direct actions that may be taken at the data plane
   include traffic policing and shaping functions (e.g., those described
   in [RFC2475]), separating flows into per-flow rate-limited queues,
   and potentially applying active queue management [RFC7567].  However
   if those (or any other) actions are to be taken, the system designer
   must ensure that the results of such actions do not compromise the
   continued safe operation of the system.  For example, the network
   (i.e. the controller plane and data plane working together) must
   mitigate in a timely fashion any potential adverse effect on
   mechanical devices controlled by the network.

4.  DetNet Security Considerations Compared With DiffServ Security
    Considerations

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

   Thus security consideration for DetNet have some aspects in common
   with DiffServ, in fact overlapping 100% with respect to IP IT
   traffic.  Security considerations for these aspects are part of the
   existing literature on IP network security, specifically the Security
   Considerations 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 is interpreted
   differently than in DiffServ and contribute to determination of the
   service provided to the packet.  In DetNet, there are similar
   consequences to DiffServ for lack of detection of, or incorrect
   handling of, packets with mismarked DSCP values, and many of the



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   points made in the DiffServ Security discussions ([RFC2475] Sec. 6.1
   , [RFC2474] Sec. 7 and [RFC6274] Sec 3.3.2.1) 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
   the PHB of that packet, 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.  The remarks
   in [RFC2474] regarding IPsec and Tunnelling Interactions are also
   relevant (though this is not to say that other sections are less
   relevant).

5.  Security Threats

   This section presents a threat model, and analyzes the possible
   threats in a DetNet-enabled network.  The threats considered in this
   section are independent of any specific technologies used to
   implement the DetNet; Section 9 considers attacks that are associated
   with the DetNet technologies encompassed by [RFC8938].

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

5.1.  Threat Model

   The threat model used in this document 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.





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   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
   DTLS.

   DetNet-Service, one of the service scenarios described in
   [I-D.varga-detnet-service-model], is the case where a service
   connects DetNet islands, i.e. two or more otherwise independent
   DetNets 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 DetNets merits security analysis to ensure the integrity
   of the networks involved.

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




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   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

5.2.4.1.  Replication: Increased Attack Surface

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

5.2.4.2.  Replication-related Header Manipulation

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

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

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

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

   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.



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5.2.5.  Controller Plane

5.2.5.1.  Path Choice Manipulation

5.2.5.1.1.  Control or Signaling Packet Modification

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

5.2.5.1.2.  Control or Signaling Packet Injection

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

5.2.5.1.3.  Increased Attack Surface

   One of the possible consequences of a path manipulation attack is an
   increased attack surface.  Thus, when the attack described in the
   previous subsection is implemented, it may increase the potential of
   other attacks to be performed.

5.2.5.2.  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.





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   DetNet flows are typically uniquely identified by their 6-tuple, i.e.
   fields within the IP header, however in some implementations the flow
   ID may also be augmented by additional per-flow attributes known to
   the system, e.g. above the IP-layer.  For the purpose of this
   document we assume any such additional fields used for flow ID 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
   service.

5.3.  Threat Summary

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





























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   +-------------------------------------------+----+-----+----+-----+
   | 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 Synchronization Mechanisms | +  |  +  | +  |  +  |
   +-------------------------------------------+----+-----+----+-----+

                     Figure 1: Threat Analysis Summary

6.  Security Threat Impacts

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

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

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




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   environment and thus may not have been designed for security in an IT
   environment with its associated components, services and protocols.

   The extent of impact of a successful vulnerability exploit varies
   considerably by use case and by industry; additional insights
   regarding the individual use cases is available from [RFC8578],
   DetNet Use Cases.  Each of those use cases is represented in
   Figure 2, including Pro Audio, Electrical Utilities, Industrial M2M
   (split into two areas, M2M Data Gathering and M2M Control Loop), and
   others.

   Aspects 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 |



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   +------------------+-----------------------------------------+-----+
   |  Health/Safety   | Med   | Hi   | Hi   | Med  | Med  | Med | Med |
   +------------------+-----------------------------------------+-----+
   |  People WB       | Med   | Hi   | Hi   | Low  | Hi   | Low | Low |
   +------------------+-----------------------------------------+-----+
   |  Effect 1 org    | Hi    | Hi   | Med  | Hi   | Med  | Med | Med |
   +------------------+-----------------------------------------+-----+
   |  Effect >1 org   | Med   | Hi   | Low  | Med  | Med  | Med | Med |
   +------------------+-----------------------------------------+-----+
   |Recovery
   +------------------+-----------------------------------------+-----+
   |  Recov Time Obj  | Med   | Hi   | Med  | Hi   | Hi   | Hi  | Hi  |
   +------------------+-----------------------------------------+-----+
   |  Recov Point Obj | Med   | Hi   | Low  | Med  | Low  | Hi  | Hi  |
   +------------------+-----------------------------------------+-----+
   |DetNet Dependence
   +------------------+-----------------------------------------+-----+
   |  Time Dependency | Hi    | Hi   | Low  | Hi   | Med  | Low | Hi  |
   +------------------+-----------------------------------------+-----+
   |  Latency/Jitter  | Hi    | Hi   | Med  | Med  | Low  | Low | Hi  |
   +------------------+-----------------------------------------+-----+
   |  Data Integrity  | Hi    | Hi   | Med  | Hi   | Low  | Hi  | Low |
   +------------------+-----------------------------------------+-----+
   |  Src Node Integ  | Hi    | Hi   | Med  | Hi   | Med  | Hi  | Hi  |
   +------------------+-----------------------------------------+-----+
   |  Availability    | Hi    | Hi   | Med  | Hi   | Low  | Hi  | Hi  |
   +------------------+-----------------------------------------+-----+

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



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   +------------------+--------------------------+
   |  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, control
   loop of the machine can become unstable.





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6.1.2.  Controller Plane Delay Attacks

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

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

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

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

6.2.  Flow Modification and Spoofing

6.2.1.  Flow Modification

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

6.2.2.  Spoofing

6.2.2.1.  Dataplane Spoofing

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

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

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







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6.2.2.2.  Controller Plane Spoofing

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

   o  modifying existing DetNet flows by changing the available
      bandwidth

   o  add or remove endpoints from a DetNet flow

   o  drop DetNet flows completely

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

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 the resource budget of that flow.

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

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

6.3.2.  Controller Plane Segmentation

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

   o  create new DetNet flows (exhausting resources)

   o  drop existing DetNet flows (denial of service)

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

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



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   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
   routing.

6.4.1.  Increased Attack Surface

   Covered briefly in Section 6.3, Segmentation Attacks.

6.4.2.  Header Manipulation at Elimination Routers

   Covered briefly in Section 6.3, Segmentation Attacks.

6.5.  Control or Signaling Packet Modification

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

6.6.  Control or Signaling Packet Injection

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

6.7.  Reconnaissance

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

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

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

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




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6.8.  Attacks on Time Synchronization Mechanisms

   Attacks on time synchronization 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.

   Some of the technology-specific security considerations and
   mitigation approaches are further discussed in the DETNET data plane
   solution documents, such as [RFC8939], [RFC8938],
   [I-D.ietf-detnet-mpls-over-udp-ip], and
   [I-D.ietf-detnet-ip-over-mpls].

7.1.  Path Redundancy

   Description

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

   Related attacks

      Path redundancy can be used to mitigate various 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




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      and thus might expose flaws in the system that might otherwise not
      be exposed.

7.2.  Integrity Protection

   Description

      Integrity Protection in the scope of DetNet is the ability to
      detect if a header has been modified (either maliciously or by
      chance) and propagate a warning to a responsible monitoring agent.
      An integrity protection mechanism is designed to counteract header
      modification attacks where a Message Authentication Code (MAC) is
      the most common.  The MAC can be distributed either in-line
      (included in the same packet) or via a side channel.  Due to the
      nature of DetNet traffic.  Note: a sideband approach may yield too
      high overhead and complexity and should only be used as a very
      last resort if in-line approaches are not viable.

      There are different levels of security available for integrity
      protection, ranging from the basic ability to detect if a header
      has been corrupted in transit (no malicious attack) to stopping a
      skilled and determined attacker capable of both subtly modifying
      fields in the headers as well as updating an unsigned MAC.  Common
      for all are the 2 steps that need to be performed in both ends.
      The first is computing the checksum or MAC.  The corresponding
      verification step must perform the same steps before comparing the
      provided with the computed value.  Only then can the receiver be
      reasonably sure that the header is authentic.

      The most basic protection mechanism consists of computing a simple
      checksum of the header fields and provide it to the next entity in
      the packets path for verification.  Using a MAC combined with a
      secret key provides the best protection against modification and
      replication attacks (see Section 5.2.2 and Section 5.2.4).  This
      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.  The secret
      key, regardless of MAC used, must be protected from falling into
      the hands of unauthorized users.

      DetNet system- and/or component- level designers need to be aware
      of these distinctions and enforce appropriate integrity protection
      mechanisms as needed based on a threat analysis.  Note that adding
      integrity protection mechanisms may introduce latency, thus many
      of the same considerations in Section 7.5.1 also apply here.

   Packet Sequence Number Integrity Considerations



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      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 component that adds the sequence number and the
      component that removes the sequence number.  The sequence number
      may be end-to-end source to destination, or may be added/deleted
      by network edge components.  The adder and remover(s) have the
      trust relationship because they are the ones that ensure that the
      sequence numbers are not modifiable.  Thus, sequence numbers can
      be protected by using encryption, or by a MAC without using
      encryption.  Between the adder and remover there may or may not be
      replication and elimination functions.  The elimination functions
      must be able to see the sequence numbers.  Therefore, if
      encryption is done between adders and removers it must not obscure
      the sequence number.  If the sequence removers and the eliminators
      are in the same physical component, it may be possible to obscure
      the sequence number, however that is a layer violation, and is not
      recommended practice.  Note: At the time of this writing, PREOF is
      not defined for the IP data plane.

   Related attacks

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

7.3.  DetNet Node Authentication

   Description

      Authentication verifies the identity of DetNet nodes (including
      DetNet Controller Plane nodes), and this enables mitigation of
      spoofing attacks.  While integrity protection ( Section 7.2)
      prevents intermediate nodes from modifying information,
      authentication (such as IPsec [RFC4301] or MACsec
      [IEEE802.1AE-2018]) can provide traffic origin verification, i.e.
      to verify that each packet in a DetNet flow is from a known
      source.

   Related attacks

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








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7.4.  Dummy Traffic Insertion

   Description

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

   Related attacks

      Removing distinctive temporal properties of individual packets or
      flows can be used to mitigate against reconnaissance attacks
      Section 5.2.6.  For example, dummy traffic can be used to
      synthetically maintain constant traffic rate even when no user
      data is transmitted, thus making it difficult to collect
      information about the times at which users are active, and the
      times at which DETNET flows are added or removed.

7.5.  Encryption

   Description

      Reconnaissance attacks (Section 5.2.6) can be mitigated by using
      encryption.  Specific encryption protocols will depend on the
      lower layers that DetNet is forwarded over.  For example, IP flows
      may be forwarded over IPsec [RFC4301], and Ethernet flows may be
      secured using MACsec [IEEE802.1AE-2018].

      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.

      Note that reconnaissance is a threat that is not specific to
      DetNet flows, and therefore reconnaissance mitigation will
      typically be analyzed and addressed by a network operator
      regardless of whether DetNet flows are deployed.  Thus, encryption
      requirements will typically not be defined in DetNet technology-
      specific specifications, but considerations of using DetNet in
      encrypted environments will be discussed in these specifications.
      For example, Section 5.1.2.3. of [RFC8939] discusses flow
      identification of DetNet flows running over IPsec.

   Related attacks

      As noted above, encryption can be used to mitigate reconnaissance
      attacks ( Section 5.2.6).  However, for a DetNet to provide
      differentiated quality of service on a flow-by-flow basis, the



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      network must be able to identify the flows individually.  This
      implies that in a reconnaissance attack the attacker may also be
      able to track individual flows to learn more about the system.

7.5.1.  Encryption Considerations for DetNet

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

   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 (v1.3 [RFC8446], in particular section 4.1 "Key exchange") and
   IKEv2 [RFC6071]) are examples of this for endpoint checks.

   However, if secret symmetric 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 faulty
   then it may inject traffic into the flow.  Group key management
   protocols can be used to automate management of such symmetric keys;
   for an example in the context of IPsec, see
   [I-D.ietf-ipsecme-g-ikev2].

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

   In either case, origin verification also requires replay detection as
   part of the security protocol to prevent an attacker from recording




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   and resending traffic, e.g., as a denial of service attack on flow
   forwarding resources.

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

7.6.  Control and Signaling Message Protection

   Description

      Control and signaling messages can be protected through the use of
      any or all of encryption, authentication, and integrity protection
      mechanisms.

   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
      Section 5.2.5.1.

7.7.  Dynamic Performance Analytics

   Description

      Incorporating Dynamic Performance Analytics ("DPA") implies that
      the DetNet design includes a performance monitoring system to
      validate that timing guarantees are being met and to detect timing
      violations or other anomalies that may be the symptom of a
      security attack or system malfunction.  If this monitoring system
      detects unexpected behavior, it must then cause action to be
      initiated to address the situation in an appropriate and timely
      manner, either at the data plane or controller plane, or both in
      concert.

      The overall DPA system can thus be decomposed into the "detection"
      and "notification" functions.  Although the time-specific DPA
      performance indicators and their implementation will likely be
      specific to a given DetNet, and as such are nascent technology at
      the time of this writing, DPA is commonly used in existing
      networks so we can make some observations on how such a system
      might be implemented for a DetNet, given that it would need to be
      adapted to address the time-specific performance indicators.

   Detection Mechanisms

      Measurement of timing performance can be done via "passive" or
      "active" monitoring, as discussed below.



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      Examples of passive monitoring strategies include



      *  Monitoring of queue and buffer levels, e.g. via Active Queue
         Management (e.g.  [RFC7567]

      *  Monitoring of per-flow counters

      *  Measurement of link statistics such as traffic volume,
         bandwidth, and QoS

      *  Detection of dropped packets

      *  Use of commercially available Network Monitoring tools

      Examples of active monitoring include



      *  In-band timing measurements (such as packet arrival times) e.g.
         by timestamping and packet inspection

      *  Use of OAM.  For DetNet-specific OAM considerations see
         [I-D.ietf-detnet-ip-oam], [I-D.ietf-detnet-mpls-oam].  Note: At
         the time of this writing, specifics of DPA have not been
         developed for the DetNet OAM, but could be a subject for future
         investigation

      *  For OAM for Ethernet specifically, see also Connectivity Fault
         Management (CFM, [IEEE802.1Q]) which defines protocols and
         practices for OAM for paths through 802.1 bridges and LANs

      *  Out-of-band detection. following the data path or parts of a
         data path, for example Bidirectional Forwarding Detection (BFD,
         e.g.  [RFC5880])

      Note that for some measurements (e.g. packet delay) it may be
      necessary to make and reconcile measurements from more than one
      physical location (e.g. a source and destination), possibly in
      both directions, in order to arrive at a given performance
      indicator value.

   Notification Mechanisms

      Making DPA measurement results available at the right place(s) and
      time(s) to effect timely response can be challenging.  Two
      notification mechanisms that are in general use are Netconf/YANG



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      Notifications (e.g.  [RFC5880]) and the proprietary local
      telemetry interfaces provided with components from some vendors.

      At the time of this writing YANG Notifications are not addressed
      by the DetNet YANG drafts, however this may be a topic for future
      work.  It is possible that some of the passive mechanisms could be
      covered by notifications from non-DetNet-specific YANG modules;
      for example if there is OAM or other performance monitoring that
      can monitor delay bounds then that could have its own associated
      YANG model which could be relevant to DetNet, for example some
      "threshold" values for timing measurement notifications.

      At the time of this writing there is an IETF Working Group for
      network/performance monitoring (IP Performance Measurement, ippm).
      See also previous work by the completed Remote Network Monitoring
      Working Group (rmonmib).  See also [RFC6632], An Overview of the
      IETF Network Management Standards.

      Vendor-specific local telemetry may be available on some
      commercially available systems, whereby the system can be
      programmed (via a proprietary dedicated port and API) to monitor
      and report on specific conditions, based on both passive and
      active measurements.

   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 Synchronization 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, take appropriate action.  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, [IEEE802.1BA]) to provide
      the service.

7.8.  Mitigation Summary

   The following table maps the attacks of Section 5, Security Threats,
   to the impacts of Section 6, Security Threat Impacts, and to the
   mitigations of the current section.  Each row specifies an attack,
   the impact of this attack if it is successfully implemented, and
   possible mitigation methods.




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



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   |Attacks on Time       |-Non-deterministic   |-Path redundancy     |
   |Synchronization       | delay               |-Control message     |
   |Mechanisms            |-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.

   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.






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8.1.2.  Central Administration

   A DetNet network can be controlled by a centralized network
   configuration and control system.  Such a system may be in a single
   central location, or it may be distributed across multiple control
   entities that function together as a unified control system for the
   network.

   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 Synchronization
   Mechanisms.

8.1.3.  Hot Swap

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

   An attack surface related to Hot Swap is that the DetNet network must
   at least consider input at runtime from components that were not part
   of the initial configuration of the network.  Even a "perfect" (or
   "hitless") replacement of a component 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 component).

   This implies that an attack such as Flow Modification, Spoofing or
   Inter-segment (which could introduce packets from a "new" component,
   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 component).

   To mitigate this situation, deployments should provide a method for
   dynamic and secure registration of new components, and (possibly
   manual) deregistration of retired components.  This would avoid the
   situation in which the network must accommodate potentially insecure
   packet flows from unknown components.

   Similarly if the network was designed to support runtime replacement
   of a clock component, then presence (or apparent presence) and thus
   consideration of packets from a new such component could affect the
   network, or the time synchronization of the network, for example by



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   initiating a new Best Master Clock selection process.  These types of
   attacks should therefore be considered when designing hot swap type
   functionality (see [RFC7384]).

8.1.4.  Data Flow Information Models

   DetNet specifies new YANG models which may present new attack
   surfaces.  Per IETF guidelines, security considerations for any YANG
   model are expected to be part of the YANG model specification, as
   described in [IETF_YANG_SEC].

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 (e.g.  IP) via the use of well-
   known protocols such as IP, MPLS Pseudowire, and Ethernet.  Various
   DetNet drafts address many specific aspects of Layer 2 and Layer 3
   integration within a DetNet, and these are not individually
   referenced here; security considerations for those aspects are
   covered within those drafts or within the related subsections of the
   present document.

   Please note that although there are no entries in the L2 and L3
   Integration line of the Mapping Between Themes and Attacks table
   Figure 4, this 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 Synchronization attack could cause a system
   that was expecting certain packets at certain times to accept



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   unintended packets based on compromised system time or time windowing
   in the scheduler.

8.1.7.  Replacement for Proprietary Fieldbuses and Ethernet-based
        Networks

   There are many proprietary "field buses" used in 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
   gateway.

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
   underestimated.

   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 handling of IT traffic by the DetNet 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.




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   The network design as a whole also needs to consider possible
   application-level dependencies of "OT"-type applications on services
   provided by the "IT part" of the network; for example, does the OT
   application depend on IT network services such as DNS or OAM?  If
   such dependencies exist, how are malicious packet flows handled?
   Such considerations are typically outside the scope of DetNet proper,
   but nonetheless need to be addressed in the overall DetNet network
   design for a given use case.

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 component diversity and potentially higher numbers of each
   component manufactured.

   The security mechanisms and protocols that are discussed in this
   document also require interoperability.  It is expected that DETNET
   network specifications that define security measures and protocols
   will be defined in a way that allows interoperability.

   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




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   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 component 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
   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 Components

   The DetNet network specifications are intended to enable an ecosystem
   in which multiple vendors can create interoperable products, thus
   promoting component diversity and potentially higher numbers of each
   component 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 component on a DetNet
   network that is intended to be highly secure may present an attack
   surface.

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

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
   attacked.



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   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 Synchronization attacks seem more likely
   relevant to large networks.

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
   behavior).

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






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   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
   boundaries.

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

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
   paths.





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

8.1.21.  Reliability and Availability

   DetNet based systems are expected to be implemented with essentially
   arbitrarily high availability (for example 99.9999% up time, or even
   12 nines).  The intent is that the DetNet designs should not make any
   assumptions about the level of reliability and availability that may
   be required of a given system, and should define parameters for
   communicating these kinds of metrics within the network.

   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.

   In practice, network designers can adopt a risk-based approach, in
   which only those attacks are mitigated whose potential cost is higher
   than the cost of mitigation.

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 sufficiently secure against problematic
   component or traffic behavior, whether malicious or incidental, and
   whether affecting a single component or multiple components.  If any
   of the security mechanisms which protect the DetNet from such
   problems are attacked or subverted, this can result in malfunction of
   the network.  Thus the design of the security system itself needs to
   be robust against attacks.



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   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.  This document addresses these concerns
   only to the extent that they are unique 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.


   +----+-------------------------------------------+
   |    | 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 Synchronization Mechanisms |
   +----+-------------------------------------------+

                         Figure 4: List of Attacks

   The Mapping Between Themes and Attacks table Figure 5maps 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.



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   +----------------------------+--------------------------------+
   | Theme                      |             Attack             |
   |                            +--+--+--+--+--+--+--+--+--+--+--+
   |                            | 1| 2| 3| 4| 5| 6| 7| 8| 9|10|11|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Network Layer - AVB/TSN Eth.| +| +| +| +| +| +| +| +| +| +| +|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Central Administration      |  |  |  |  |  | +| +| +| +| +| +|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Hot Swap                    |  | +| +|  |  |  |  |  |  |  | +|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Data Flow Information Models|  |  |  |  |  |  |  |  |  |  |  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |L2 and L3 Integration       |  |  |  |  |  |  |  |  |  |  |  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |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       |  |  |  |  |  |  |  |  |  |  |  |
   |Components                  |  |  |  |  |  |  |  |  |  |  |  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |DetNet Network Size         | +|  |  |  |  | +| +|  |  |  | +|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Multiple Hops               | +| +|  |  |  | +| +|  |  |  | +|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Level of Service            |  |  |  |  |  |  |  | +| +| +|  |
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Bounded Latency             | +|  |  |  |  |  |  |  |  |  | +|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Low Latency                 | +|  |  |  |  |  |  | +| +| +| +|
   +----------------------------+--+--+--+--+--+--+--+--+--+--+--+
   |Bounded Jitter              | +|  |  |  |  |  |  |  |  |  |  |



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

               Figure 5: Mapping Between Themes and Attacks

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
   types:

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

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

   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
   implementations.





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   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 ( [RFC8939])
   and delivers service over sub-layer technologies such as MPLS
   ([RFC8938]) and IEEE 802.1 Time-Sensitive Networking (TSN)
   ([I-D.ietf-detnet-ip-over-tsn]).  Application flows can be protected
   through whatever means are provided by the layer and sub-layer
   technologies.  For example, technology-specific encryption may be
   used, for example for IP flows, IPSec [RFC4301].  For IP over
   Ethernet (Layer 2) flows using an underlying sub-net, MACSec
   [IEEE802.1AE-2018] may be appropriate.  For some use cases packet
   integrity protection without encryption may be sufficient.

   However, if the DetNet nodes cannot decrypt IPsec traffic, then
   DetNet flow identification for encrypted IP traffic flows must be
   performed in a different way than it would be for unencrypted IP
   DetNet flows.  The DetNet IP Data Plane identifies unencrypted 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, leaving only three components of the 6-tuple,
   which are the two IP addresses and the DSCP.  Identification of
   DetNet flows over IPsec is further discussed in Section 5.1.2.3.  of
   [RFC8939].

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

9.1.  IP

   The IP protocol has a long history of security considerations and
   architectural protection mechanisms.  From a data plane perspective
   DetNet does not add or modify any IP header information, 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
   document.



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

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

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

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




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   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 [RFC8077],
   [RFC3931], [RFC3985], [RFC6073], and [RFC6478].

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

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

   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 document 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.






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

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

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

       Norman Finn (Huawei)
       3101 Rio Way, Spring Valley, California 91977, USA
       email nfinn@nfinnconsulting.com

       Stewart Bryant (Futurewei Technologies)

       email: stewart.bryant@gmail.com

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

       Carsten Bormann (Universitat Bremen TZI)
       Postfach 330440, D-28359 Bremen, Germany
       email: cabo@tzi.org



14.  References

14.1.  Normative References

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

   [RFC8938]  Varga, B., Ed., Farkas, J., Berger, L., Malis, A., and S.
              Bryant, "Deterministic Networking (DetNet) Data Plane
              Framework", RFC 8938, DOI 10.17487/RFC8938, November 2020,
              <https://www.rfc-editor.org/info/rfc8938>.

   [RFC8939]  Varga, B., Ed., Farkas, J., Berger, L., Fedyk, D., and S.
              Bryant, "Deterministic Networking (DetNet) Data Plane:
              IP", RFC 8939, DOI 10.17487/RFC8939, November 2020,
              <https://www.rfc-editor.org/info/rfc8939>.



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14.2.  Informative References

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

   [I-D.ietf-detnet-flow-information-model]
              Varga, B., Farkas, J., Cummings, R., Jiang, Y., and D.
              Fedyk, "DetNet Flow Information Model", draft-ietf-detnet-
              flow-information-model-12 (work in progress), December
              2020.

   [I-D.ietf-detnet-ip-oam]
              Mirsky, G., Chen, M., and D. Black, "Operations,
              Administration and Maintenance (OAM) for Deterministic
              Networks (DetNet) with IP Data Plane", draft-ietf-detnet-
              ip-oam-00 (work in progress), September 2020.

   [I-D.ietf-detnet-ip-over-mpls]
              Varga, B., Berger, L., Fedyk, D., Bryant, S., and J.
              Korhonen, "DetNet Data Plane: IP over MPLS", draft-ietf-
              detnet-ip-over-mpls-09 (work in progress), October 2020.

   [I-D.ietf-detnet-ip-over-tsn]
              Varga, B., Farkas, J., Malis, A., and S. Bryant, "DetNet
              Data Plane: IP over IEEE 802.1 Time Sensitive Networking
              (TSN)", draft-ietf-detnet-ip-over-tsn-04 (work in
              progress), November 2020.

   [I-D.ietf-detnet-mpls-oam]
              Mirsky, G. and M. Chen, "Operations, Administration and
              Maintenance (OAM) for Deterministic Networks (DetNet) with
              MPLS Data Plane", draft-ietf-detnet-mpls-oam-01 (work in
              progress), July 2020.

   [I-D.ietf-detnet-mpls-over-udp-ip]
              Varga, B., Farkas, J., Berger, L., Malis, A., and S.
              Bryant, "DetNet Data Plane: MPLS over UDP/IP", draft-ietf-
              detnet-mpls-over-udp-ip-07 (work in progress), October
              2020.

   [I-D.ietf-ipsecme-g-ikev2]
              Smyslov, V. and B. Weis, "Group Key Management using
              IKEv2", draft-ietf-ipsecme-g-ikev2-01 (work in progress),
              July 2020.






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

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

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

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

   [IEEE802.1BA]
              IEEE Standards Association, "IEEE Standard for Local and
              Metropolitan Area Networks -- Audio Video Bridging (AVB)
              Systems", 2011,
              <https://ieeexplore.ieee.org/document/6032690>.

   [IEEE802.1Q]
              IEEE Standards Association, "IEEE Standard for Local and
              metropolitan area networks--Bridges and Bridged Networks -
              Annex J - Connectivity Fault Management", 2014,
              <https://ieeexplore.ieee.org/document/6991462>.

   [IEEE802.1Qbv-2015]
              IEEE Standards Association, "IEEE Standard for Local and
              metropolitan area networks -- Bridges and Bridged Networks
              - Amendment 25: Enhancements for Scheduled Traffic", 2015,
              <https://ieeexplore.ieee.org/document/8613095>.

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

   [IETF_YANG_SEC]
              IETF, "YANG Module Security Considerations", 2018,
              <https://trac.ietf.org/trac/ops/wiki/yang-security-
              guidelines>.



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   [IT_DEF]   Wikipedia, "IT Definition", 2020,
              <https://en.wikiquote.org/wiki/Information_technology>.

   [OT_DEF]   Wikipedia, "OT Definition", 2020,
              <https://en.wikipedia.org/wiki/Operational_technology>.

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

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

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

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

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

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

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
              <https://www.rfc-editor.org/info/rfc5880>.

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

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



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

   [RFC6071]  Frankel, S. and S. Krishnan, "IP Security (IPsec) and
              Internet Key Exchange (IKE) Document Roadmap", RFC 6071,
              DOI 10.17487/RFC6071, February 2011,
              <https://www.rfc-editor.org/info/rfc6071>.

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

   [RFC6274]  Gont, F., "Security Assessment of the Internet Protocol
              Version 4", RFC 6274, DOI 10.17487/RFC6274, July 2011,
              <https://www.rfc-editor.org/info/rfc6274>.

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

   [RFC6632]  Ersue, M., Ed. and B. Claise, "An Overview of the IETF
              Network Management Standards", RFC 6632,
              DOI 10.17487/RFC6632, June 2012,
              <https://www.rfc-editor.org/info/rfc6632>.

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

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

   [RFC7567]  Baker, F., Ed. and G. Fairhurst, Ed., "IETF
              Recommendations Regarding Active Queue Management",
              BCP 197, RFC 7567, DOI 10.17487/RFC7567, July 2015,
              <https://www.rfc-editor.org/info/rfc7567>.

   [RFC7835]  Saucez, D., Iannone, L., and O. Bonaventure, "Locator/ID
              Separation Protocol (LISP) Threat Analysis", RFC 7835,
              DOI 10.17487/RFC7835, April 2016,
              <https://www.rfc-editor.org/info/rfc7835>.




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   [RFC8077]  Martini, L., Ed. and G. Heron, Ed., "Pseudowire Setup and
              Maintenance Using the Label Distribution Protocol (LDP)",
              STD 84, RFC 8077, DOI 10.17487/RFC8077, February 2017,
              <https://www.rfc-editor.org/info/rfc8077>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

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

   [RS_DEF]   Wikipedia, "RS Definition", 2020,
              <https://en.wikipedia.org/wiki/Network_segmentation>.

Authors' Addresses

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

   Phone: +1 415 465 4339
   Email: ethan@ieee.org
   URI:   http://www.dolby.com


   Tal Mizrahi
   Huawei Network.IO Innovation Lab

   Email: tal.mizrahi.phd@gmail.com


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

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









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