Internet Engineering Task Force T. Mizrahi
Internet-Draft HUAWEI
Intended status: Informational E. Grossman, Ed.
Expires: July 13, 2020 DOLBY
A. Hacker
MISTIQ
S. Das
Applied Communication Sciences
J. Dowdell
Airbus Defence and Space
H. Austad
SINTEF Digital
N. Finn
HUAWEI
January 10, 2020
Deterministic Networking (DetNet) Security Considerations
draft-ietf-detnet-security-07
Abstract
A deterministic network is one that can carry data flows for real-
time applications with extremely low data loss rates and bounded
latency. Deterministic networks have been successfully deployed in
real-time operational technology (OT) applications for some years.
However, such networks are typically isolated from external access,
and thus the security threat from external attackers is low. IETF
Deterministic Networking (DetNet) specifies a set of technologies
that enable creation of deterministic networks on IP-based networks
of potentially wide area (on the scale of a corporate network)
potentially bringing the OT network into contact with Information
Technology (IT) traffic and security threats that lie outside of a
tightly controlled and bounded area (such as the internals of an
aircraft). These DetNet technologies have not previously been
deployed together on a wide area IP-based network, and thus can
present security considerations that may be new to IP-based wide area
network designers. This document, intended for use by DetNet network
designers, provides insight into these security considerations.
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
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working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 13, 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Security Threats . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Threat Model . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Threat Analysis . . . . . . . . . . . . . . . . . . . . . 7
3.2.1. Delay . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2.1.1. Delay Attack . . . . . . . . . . . . . . . . . . 7
3.2.2. DetNet Flow Modification or Spoofing . . . . . . . . 7
3.2.3. Resource Segmentation or Slicing . . . . . . . . . . 7
3.2.3.1. Inter-segment Attack . . . . . . . . . . . . . . 7
3.2.4. Packet Replication and Elimination . . . . . . . . . 8
3.2.4.1. Replication: Increased Attack Surface . . . . . . 8
3.2.4.2. Replication-related Header Manipulation . . . . . 8
3.2.5. Path Choice . . . . . . . . . . . . . . . . . . . . . 8
3.2.5.1. Path Manipulation . . . . . . . . . . . . . . . . 8
3.2.5.2. Path Choice: Increased Attack Surface . . . . . . 9
3.2.6. Control Plane . . . . . . . . . . . . . . . . . . . . 9
3.2.6.1. Control or Signaling Packet Modification . . . . 9
3.2.6.2. Control or Signaling Packet Injection . . . . . . 9
3.2.7. Scheduling or Shaping . . . . . . . . . . . . . . . . 9
3.2.7.1. Reconnaissance . . . . . . . . . . . . . . . . . 9
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3.2.8. Time Synchronization Mechanisms . . . . . . . . . . . 9
3.3. Threat Summary . . . . . . . . . . . . . . . . . . . . . 9
4. Security Threat Impacts . . . . . . . . . . . . . . . . . . . 10
4.1. Delay-Attacks . . . . . . . . . . . . . . . . . . . . . . 13
4.1.1. Data Plane Delay Attacks . . . . . . . . . . . . . . 13
4.1.2. Control Plane Delay Attacks . . . . . . . . . . . . . 13
4.2. Flow Modification and Spoofing . . . . . . . . . . . . . 14
4.2.1. Flow Modification . . . . . . . . . . . . . . . . . . 14
4.2.2. Spoofing . . . . . . . . . . . . . . . . . . . . . . 14
4.2.2.1. Dataplane Spoofing . . . . . . . . . . . . . . . 14
4.2.2.2. Control Plane Spoofing . . . . . . . . . . . . . 14
4.3. Segmentation attacks (injection) . . . . . . . . . . . . 15
4.3.1. Data Plane Segmentation . . . . . . . . . . . . . . . 15
4.3.2. Control Plane segmentation . . . . . . . . . . . . . 15
4.4. Replication and Elimination . . . . . . . . . . . . . . . 15
4.4.1. Increased Attack Surface . . . . . . . . . . . . . . 15
4.4.2. Header Manipulation at Elimination Bridges . . . . . 16
4.5. Control or Signaling Packet Modification . . . . . . . . 16
4.6. Control or Signaling Packet Injection . . . . . . . . . . 16
4.7. Reconnaissance . . . . . . . . . . . . . . . . . . . . . 16
4.8. Attacks on Time Sync Mechanisms . . . . . . . . . . . . . 16
4.9. Attacks on Path Choice . . . . . . . . . . . . . . . . . 16
5. Security Threat Mitigation . . . . . . . . . . . . . . . . . 17
5.1. Path Redundancy . . . . . . . . . . . . . . . . . . . . . 17
5.2. Integrity Protection . . . . . . . . . . . . . . . . . . 17
5.3. DetNet Node Authentication . . . . . . . . . . . . . . . 18
5.4. Dummy Traffic Insertion . . . . . . . . . . . . . . . . . 18
5.5. Encryption . . . . . . . . . . . . . . . . . . . . . . . 18
5.5.1. Encryption Considerations for DetNet . . . . . . . . 19
5.6. Control and Signaling Message Protection . . . . . . . . 20
5.7. Dynamic Performance Analytics . . . . . . . . . . . . . . 20
5.8. Mitigation Summary . . . . . . . . . . . . . . . . . . . 21
6. Association of Attacks to Use Cases . . . . . . . . . . . . . 22
6.1. Use Cases by Common Themes . . . . . . . . . . . . . . . 22
6.1.1. Network Layer - AVB/TSN Ethernet . . . . . . . . . . 22
6.1.2. Central Administration . . . . . . . . . . . . . . . 23
6.1.3. Hot Swap . . . . . . . . . . . . . . . . . . . . . . 23
6.1.4. Data Flow Information Models . . . . . . . . . . . . 24
6.1.5. L2 and L3 Integration . . . . . . . . . . . . . . . . 24
6.1.6. End-to-End Delivery . . . . . . . . . . . . . . . . . 24
6.1.7. Proprietary Deterministic Ethernet Networks . . . . . 25
6.1.8. Replacement for Proprietary Fieldbuses . . . . . . . 25
6.1.9. Deterministic vs Best-Effort Traffic . . . . . . . . 25
6.1.10. Deterministic Flows . . . . . . . . . . . . . . . . . 26
6.1.11. Unused Reserved Bandwidth . . . . . . . . . . . . . . 26
6.1.12. Interoperability . . . . . . . . . . . . . . . . . . 27
6.1.13. Cost Reductions . . . . . . . . . . . . . . . . . . . 27
6.1.14. Insufficiently Secure Devices . . . . . . . . . . . . 27
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6.1.15. DetNet Network Size . . . . . . . . . . . . . . . . . 27
6.1.16. Multiple Hops . . . . . . . . . . . . . . . . . . . . 28
6.1.17. Level of Service . . . . . . . . . . . . . . . . . . 28
6.1.18. Bounded Latency . . . . . . . . . . . . . . . . . . . 29
6.1.19. Low Latency . . . . . . . . . . . . . . . . . . . . . 29
6.1.20. Bounded Jitter (Latency Variation) . . . . . . . . . 29
6.1.21. Symmetrical Path Delays . . . . . . . . . . . . . . . 29
6.1.22. Reliability and Availability . . . . . . . . . . . . 30
6.1.23. Redundant Paths . . . . . . . . . . . . . . . . . . . 30
6.1.24. Security Measures . . . . . . . . . . . . . . . . . . 30
6.2. Attack Types by Use Case Common Theme . . . . . . . . . . 31
6.3. Security Considerations for OAM Traffic . . . . . . . . . 33
7. DetNet Technology-Specific Threats . . . . . . . . . . . . . 33
7.1. IP . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
7.2. MPLS . . . . . . . . . . . . . . . . . . . . . . . . . . 35
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36
9. Security Considerations . . . . . . . . . . . . . . . . . . . 36
10. Informative References . . . . . . . . . . . . . . . . . . . 36
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 38
1. Introduction
Security is of particularly high importance in DetNet networks
because many of the use cases which are enabled by DetNet [RFC8578]
include control of physical devices (power grid components,
industrial controls, building controls) which can have high
operational costs for failure, and present potentially attractive
targets for cyber-attackers.
This situation is even more acute given that one of the goals of
DetNet is to provide a "converged network", i.e. one that includes
both IT traffic and OT traffic, thus exposing potentially sensitive
OT devices to attack in ways that were not previously common (usually
because they were under a separate control system or otherwise
isolated from the IT network, for example [ARINC664P7]). Security
considerations for OT networks are not a new area, and there are many
OT networks today that are connected to wide area networks or the
Internet; this document focuses on the issues that are specific to
the DetNet technologies and use cases.
Given the above considerations, securing a DetNet starts with a
scrupulously well-designed and well-managed engineered network
following industry best practices for security at both the data plane
and control plane; this is the assumed starting point for the
considerations discussed herein. In this context we view the network
design and managment aspects of network security as being primarily
concerned with denial-of service prevention by ensuring that DetNet
traffic goes where it's supposed to and that an external attacker
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can't inject traffic that disrupts the DetNet's delivery timing
assurance. The time-specific aspects of DetNet security presented
here take up where the design and management aspects leave off.
The security requirements for any given DetNet network are
necessarily specific to the use cases handled by that network. Thus
the reader is assumed to be familiar with the specific security
requirements of their use cases, for example those outlined in the
DetNet Use Cases [RFC8578] and the Security Considerations sections
of the DetNet documents applicable to the network technologies in
use, for example [I-D.ietf-detnet-ip]).
The DetNet technologies include ways to:
o Reserve data plane resources for DetNet flows in some or all of
the intermediate nodes (e.g. bridges or routers) along the path of
the flow
o Provide explicit routes for DetNet flows that do not rapidly
change with the network topology
o Distribute data from DetNet flow packets over time and/or space to
ensure delivery of each packet's data' in spite of the loss of a
path
This document includes sections on 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].
2. Abbreviations
IT Information technology (the application of computers to
store, study, retrieve, transmit, and manipulate data or information,
often in the context of a business or other enterprise - Wikipedia).
OT Operational Technology (the hardware and software
dedicated to detecting or causing changes in physical processes
through direct monitoring and/or control of physical devices such as
valves, pumps, etc. - Wikipedia)
MITM Man in the Middle
SN Sequence Number
STRIDE Addresses risk and severity associated with threat
categories: Spoofing identity, Tampering with data, Repudiation,
Information disclosure, Denial of service, Elevation of privilege.
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DREAD Compares and prioritizes risk represented by these threat
categories: Damage potential, Reproducibility, Exploitability, how
many Affected users, Discoverability.
PTP Precision Time Protocol [IEEE1588]
3. Security Threats
This section presents a threat model, and analyzes the possible
threats in a DetNet-enabled network. The threats considered in this
section are independent of any specific technologies used to
implement the DetNet; Section 7) considers attacks that are
associated with the DetNet technologies encompassed by
[I-D.ietf-detnet-data-plane-framework].
We distinguish control 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 control plane. There
is also a difference in terms of security solutions: the way you
secure the data plane is often different than the way you secure the
control plane.
3.1. Threat Model
The threat model used in this memo is based on the threat model of
Section 3.1 of [RFC7384]. This model classifies attackers based on
two criteria:
o Internal vs. external: internal attackers either have access to a
trusted segment of the network or possess the encryption or
authentication keys. External attackers, on the other hand, do
not have the keys and have access only to the encrypted or
authenticated traffic.
o Man in the Middle (MITM) vs. packet injector: MITM attackers are
located in a position that allows interception and modification of
in-flight protocol packets, whereas a traffic injector can only
attack by generating protocol packets.
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 3.2. Most of the direct threats to
DetNet are Active attacks, but it is highly suggested that DetNet
application developers take appropriate measures to protect the
content of the streams from passive attacks.
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DetNet-Service, one of the service scenarios described in
[I-D.varga-detnet-service-model], is the case where a service
connects DetNet networking islands, i.e. two or more otherwise
independent DetNet network domains are connected via a link that is
not intrinsically part of either network. This implies that there
could be DetNet traffic flowing over a non-DetNet link, which may
provide an attacker with an advantageous opportunity to tamper with
DetNet traffic. The security properties of non-DetNet links are
outside of the scope of DetNet Security, but it should be noted that
use of non-DetNet services to interconnect DetNet networks merits
security analysis to ensure the integrity of the DetNet networks
involved.
3.2. Threat Analysis
3.2.1. Delay
3.2.1.1. Delay Attack
An attacker can maliciously delay DetNet data flow traffic. By
delaying the traffic, the attacker can compromise the service of
applications that are sensitive to high delays or to high delay
variation. The delay may be constant or modulated.
3.2.2. 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.
3.2.3. Resource Segmentation or Slicing
3.2.3.1. Inter-segment Attack
An attacker can inject traffic, consuming network device resources,
thereby affecting DetNet flows. This can be performed using non-
DetNet traffic that affects DetNet traffic, or by using DetNet
traffic from one DetNet flow that affects traffic from different
DetNet flows.
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3.2.4. Packet Replication and Elimination
3.2.4.1. Replication: Increased Attack Surface
Redundancy is intended to increase the robustness and survivability
of DetNet flows, and replication over multiple paths can potentially
mitigate an attack that is limited to a single path. However, the
fact that packets are replicated over multiple paths increases the
attack surface of the network, i.e., there are more points in the
network that may be subject to attacks.
3.2.4.2. Replication-related Header Manipulation
An attacker can manipulate the replication-related header fields
(R-TAG). This capability opens the door for various types of
attacks. For example:
o Forward both replicas - malicious change of a packet SN (Sequence
Number) can cause both replicas of the packet to be forwarded.
Note that this attack has a similar outcome to a replay attack.
o Eliminate both replicas - SN manipulation can be used to cause
both replicas to be eliminated. In this case an attacker that has
access to a single path can cause packets from other paths to be
dropped, thus compromising some of the advantage of path
redundancy.
o Flow hijacking - an attacker can hijack a DetNet flow with access
to a single path by systematically replacing the SNs on the given
path with higher SN values. For example, an attacker can replace
every SN value S with a higher value S+C, where C is a constant
integer. Thus, the attacker creates a false illusion that the
attacked path has the lowest delay, causing all packets from other
paths to be eliminated. Once the flow is hijacked the attacker
can either replace en route packets with malicious packets, or
simply injecting errors, causing the packets to be dropped at
their destination.
3.2.5. Path Choice
3.2.5.1. Path Manipulation
An attacker can maliciously change, add, or remove a path, thereby
affecting the corresponding DetNet flows that use the path.
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3.2.5.2. Path Choice: Increased Attack Surface
One of the possible consequences of a path manipulation attack is an
increased attack surface. Thus, when the attack described in the
previous subsection is implemented, it may increase the potential of
other attacks to be performed.
3.2.6. Control Plane
3.2.6.1. Control or Signaling Packet Modification
An attacker can maliciously modify en route control packets in order
to disrupt or manipulate the DetNet path/resource allocation.
3.2.6.2. Control or Signaling Packet Injection
An attacker can maliciously inject control packets in order to
disrupt or manipulate the DetNet path/resource allocation.
3.2.7. Scheduling or Shaping
3.2.7.1. Reconnaissance
A passive eavesdropper can identify DetNet flows and then gather
information about en route DetNet flows, e.g., the number of DetNet
flows, their bandwidths, their schedules, or other temporal
properties. The gathered information can later be used to invoke
other attacks on some or all of the flows.
Note that in some cases DetNet flows may be identified based on an
explicit DetNet header, but in some cases the flow identification may
be based on fields from the L3/L4 headers. If L3/L4 headers are
involved, for purposes of this document we assume they are encrypted
and/or integrity-protected from external attackers.
3.2.8. Time Synchronization Mechanisms
An attacker can use any of the attacks described in [RFC7384] to
attack the synchronization protocol, thus affecting the DetNet
service.
3.3. Threat Summary
A summary of the attacks that were discussed in this section is
presented in Figure 1. For each attack, the table specifies the type
of attackers that may invoke the attack. In the context of this
summary, the distinction between internal and external attacks is
under the assumption that a corresponding security mechanism is being
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used, and that the corresponding network equipment takes part in this
mechanism.
+-----------------------------------------+----+----+----+----+
| Attack | Attacker Type |
| +---------+---------+
| |Internal |External |
| |MITM|Inj.|MITM|Inj.|
+-----------------------------------------+----+----+----+----+
|Delay attack | + | + | + | + |
+-----------------------------------------+----+----+----+----+
|DetNet Flow Modification or Spoofing | + | + | | |
+-----------------------------------------+----+----+----+----+
|Inter-segment Attack | + | + | | |
+-----------------------------------------+----+----+----+----+
|Replication: Increased Attack Surface | + | + | + | + |
+-----------------------------------------+----+----+----+----+
|Replication-related Header Manipulation | + | | | |
+-----------------------------------------+----+----+----+----+
|Path Manipulation | + | + | | |
+-----------------------------------------+----+----+----+----+
|Path Choice: Increased Attack Surface | + | + | + | + |
+-----------------------------------------+----+----+----+----+
|Control or Signaling Packet Modification | + | | | |
+-----------------------------------------+----+----+----+----+
|Control or Signaling Packet Injection | | + | | |
+-----------------------------------------+----+----+----+----+
|Reconnaissance | + | | + | |
+-----------------------------------------+----+----+----+----+
|Attacks on Time Sync Mechanisms | + | + | + | + |
+-----------------------------------------+----+----+----+----+
Figure 1: Threat Analysis Summary
4. Security Threat Impacts
This section describes and rates the impact of the attacks described
in Section 3. In this section, the impacts as described assume that
the associated mitigation is not present or has failed. Mitigations
are discussed in Section 5.
In computer security, the impact (or consequence) of an incident can
be measured in loss of confidentiality, integrity or availability of
information.
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 devices, services and protocols.
The severity of various components of the impact of a successful
vulnerability exploit to use cases by industry is available in more
detail in [RFC8578]. Each of the use cases in the DetNet Use Cases
is represented in the table below, including Pro Audio, Electrical
Utilities, Industrial M2M (split into two areas, M2M Data Gathering
and M2M Control Loop), and others.
Components of Impact (left column) include Criticality of Failure,
Effects of Failure, Recovery, and DetNet Functional Dependence.
Criticality of failure summarizes the seriousness of the impact. The
impact of a resulting failure can affect many different metrics that
vary greatly in scope and severity. In order to reduce the number of
variables, only the following were included: Financial, Health and
Safety, People well being (People WB), Affect on a single
organization, and affect on multiple organizations. Recovery
outlines how long it would take for an affected use case to get back
to its pre-failure state (Recovery time objective, RTO), and how much
of the original service would be lost in between the time of service
failure and recovery to original state (Recovery Point Objective,
RPO). DetNet dependence maps how much the following DetNet service
objectives contribute to impact of failure: Time dependency, data
integrity, source node integrity, availability, latency/jitter.
The scale of the Impact mappings is low, medium, and high. In some
use cases there may be a multitude of specific applications in which
DetNet is used. For simplicity this section attempts to average the
varied impacts of different applications. This section does not
address the overall risk of a certain impact which would require the
likelihood of a failure happening.
In practice any such ratings will vary from case to case; the ratings
shown here are given as examples.
Table, Part One (of Two)
+------------------+-----------------------------------------+-----+
| | Pro A | Util | Bldg |Wire- | Cell |M2M |M2M |
| | | | | less | |Data |Ctrl |
+------------------+-----------------------------------------+-----+
| Criticality | Med | Hi | Low | Med | Med | Med | Med |
+------------------+-----------------------------------------+-----+
| Effects
+------------------+-----------------------------------------+-----+
| 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.
4.1. Delay-Attacks
4.1.1. Data Plane Delay Attacks
Delayed messages in a DetNet link can result in the same behavior as
dropped messages in ordinary networks as the services attached to the
stream has strict deterministic requirements.
For a single path scenario, disruption is a real possibility, whereas
in a multipath scenario, large delays or instabilities in one stream
can lead to increased buffer and CPU resources on the elimination
bridge.
A data-plane delay attack on a system controlling substantial moving
devices, for example in industrial automation, can cause physical
damage. For example, if the network promises a bounded latency of
2ms for a flow, yet the machine receives it with 5ms latency, the
machine's control loop can become unstable.
4.1.2. Control 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.
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o Delayed tear-down can lead to resource leakage, which in turn can
result in failure to allocate new streams finally giving rise to a
denial of service attack.
o Failure to deliver, or severely delaying, signalling messages
adding an end-point to a multicast-group will prevent the new EP
from receiving expected frames thus disrupting expected behavior.
o Delaying messages removing an EP from a group can lead to loss of
privacy as the EP will continue to receive messages even after it
is supposedly removed.
4.2. Flow Modification and Spoofing
4.2.1. 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.
4.2.2. Spoofing
4.2.2.1. Dataplane Spoofing
Spoofing dataplane messages can result in increased resource
consumptions on the bridges throughout the network as it will
increase buffer usage and CPU utilization. This can lead to resource
exhaustion and/or increased delay.
If the attacker manages to create valid headers, the false messages
can be forwarded through the network, using part of the allocated
bandwidth. This in turn can cause legitimate messages to be dropped
when the budget has been exhausted.
Finally, the endpoint will have to deal with invalid messages being
delivered to the endpoint instead of (or in addition to) a valid
message.
4.2.2.2. Control Plane Spoofing
A successful control plane spoofing-attack will potentionally have
adverse effects. It can do virtually anything from:
o modifying existing streams by changing the available bandwidth
o add or remove endpoints from a stream
o drop streams completly
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o falsely create new streams (exhaust the systems resources, or to
enable streams outside the Network engineer's control)
4.3. Segmentation attacks (injection)
4.3.1. Data Plane Segmentation
Injection of false messages in a DetNet stream could lead to
exhaustion of the available bandwidth for a stream if the bridges
accounts false messages to the stream's budget.
In a multipath scenario, injected messages will cause increased CPU
utilization in elimination bridges. 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 bridges than normal, giving rise to a
resource exhaustion attack on the bridges.
If a stream is interrupted, the end application will be affected by
what is now a non-deterministic stream.
4.3.2. Control Plane segmentation
A successful Control Plane segmentation attack control messages to be
interpreted by nodes in the network, unbeknownst to the central
controller or the network engineer. This has the potential to create
o new streams (exhausting resources)
o drop existing (denial of service)
o add/remove end-stations to a multicast group (loss of privacy)
o modify the stream attributes (affecting available bandwidth
4.4. Replication and Elimination
The Replication and Elimination is relevant only to Data Plane
messages as Signalling is not subject to multipath routing.
4.4.1. Increased Attack Surface
Covered briefly in Section 4.3
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4.4.2. Header Manipulation at Elimination Bridges
Covered briefly in Section 4.3
4.5. Control or Signaling Packet Modification
If the control plane packets are subject to manipulation undetected,
the network can be severely compromised.
4.6. Control or Signaling Packet Injection
If an attacker can inject control plane packets undetected, the
network can be severely compromised.
4.7. 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.
4.8. Attacks on Time Sync Mechanisms
Attacks on time sync mechanisms are addressed in [RFC7384].
4.9. Attacks on Path Choice
This is covered in part in Section 4.3, and as with Replication and
Elimination (Section 4.4), this is relevant for DataPlane messages.
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5. Security Threat Mitigation
This section describes a set of measures that can be taken to
mitigate the attacks described in Section 3. These mitigations
should be viewed as a toolset that includes several different and
diverse tools. Each application or system will typically use a
subset of these tools, based on a system-specific threat analysis.
5.1. Path Redundancy
Description
A DetNet flow that can be forwarded simultaneously over multiple
paths. Path replication and elimination [RFC8655] provides
resiliency to dropped or delayed packets. This redundancy
improves the robustness to failures and to man-in-the-middle
attacks.
Related attacks
Path redundancy can be used to mitigate various man-in-the-middle
attacks, including attacks described in Section 3.2.1,
Section 3.2.2, Section 3.2.3, and Section 3.2.8. However it is
also possible that multiple paths may make it more difficult to
locate the source of a MITM attacker.
5.2. Integrity Protection
Description
An integrity protection mechanism, such as a Hash-based Message
Authentication Code (HMAC) can be used to mitigate modification
attacks on IP packets. Integrity protection in the control plane
is discussed in Section 5.6.
Packet Sequence Number Integrity Considerations
The use of PREOF in a DetNet implementation implies the use of a
sequence number for each packet. There is a trust relationship
between the device that adds the sequence number and the device
that removes the sequence number. The sequence number may be end-
to-end source to destination, or may be added/deleted by network
edge devices. The adder and remover(s) have the trust
relationship because they are the ones that ensure that the
sequence numbers are not modifiable. Between those two points,
there may or may not be replication and elimination functions.
The elimination functions must be able to see the sequence
numbers. Therefore any encryption that is done between adders and
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removers must not obscure the sequence number. If the sequence
removers and the eliminators are in the same physical device, it
may be possible to obscure the sequence number, however that is a
layer violation, and is not recommended practice.
Related attacks
Integrity protection mitigates attacks related to modification and
tampering, including the attacks described in Section 3.2.2 and
Section 3.2.4.
5.3. DetNet Node Authentication
Description
Source authentication verifies the authenticity of DetNet sources,
enabling mitigation of spoofing attacks. Note that while
integrity protection (Section 5.2) prevents intermediate nodes
from modifying information, authentication can provide traffic
origin verification, i.e. to verify that each packet in a DetNet
flow is from a trusted source. Authentication may be implemented
as part of ingress filtering, for example.
Related attacks
DetNet node authentication is used to mitigate attacks related to
spoofing, including the attacks of Section 3.2.2, and
Section 3.2.4.
5.4. 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 3.2.7.
5.5. Encryption
Description
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DetNet flows can be forwarded in encrypted form at the DetNet
layer. Alternatively, if the payload is end-to-end encrypted at
the application layer, the DetNet nodes should not have any need
to inspect the payload itself, and thus the DetNet implementation
can be data-agnostic.
Related attacks
Encryption can be used to mitigate recon attacks (Section 3.2.7).
However, for a DetNet network to give differentiated quality of
service on a flow-by-flow basis, the network must be able to
identify the flows individually. This implies that in a recon
attack the attacker may also be able to track individual flows to
learn more about the system.
5.5.1. 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.
Asymmetrical crypto is typically not used in networks on a packet-by-
packet basis due to its computational cost. For example, if only
endpoint checks or checks at a small number of intermediate points
are required, asymmetric crypto can be used to authenticate
distribution or exchange of a secret symmetric crypto key; a
successful check based on that key will provide traffic origin
verification, as long as the key is kept secret by the participants.
TLS and IKE (for IPsec) are examples of this for endpoint checks.
However, if secret symmetrical keys are used for this purpose the key
must be given to all relays, which increases the probability of a
secret key being leaked. Also, if any relay is compromised or
misbehaving it may inject traffic into the flow.
Alternatively, asymmetric crypto can provide traffic origin
verification at every intermediate node. For example, a DetNet flow
can be associated with an (asymmetric) keypair, such that the private
key is available to the source of the flow and the public key is
distributed with the flow information, allowing verification at every
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node for every packet. However, this is more computationally
expensive.
In either case, origin verification also requires replay detection as
part of the security protocol to prevent an attacker from recording
and resending traffic, e.g., as a denial of service attack on flow
forwarding resources.
If crypto keys are to be regenerated over the duration of the flow
then the time required to accomplish this must be accounted for in
the latency calculations.
5.6. Control and Signaling Message Protection
Description
Control and sigaling messages can be protected using
authentication and integrity protection mechanisms.
Related attacks
These mechanisms can be used to mitigate various attacks on the
control plane, as described in Section 3.2.6, Section 3.2.8 and
Section 3.2.5.
5.7. Dynamic Performance Analytics
Description
Information about the network performance can be gathered in real-
time in order to detect anomalies and unusual behavior that may be
the symptom of a security attack. The gathered information can be
based, for example, on per-flow counters, bandwidth measurement,
and monitoring of packet arrival times. Unusual behavior or
potentially malicious nodes can be reported to a management
system, or can be used as a trigger for taking corrective actions.
The information can be tracked by DetNet end systems and transit
nodes, and exported to a management system, for example using
NETCONF.
Related attacks
Performance analytics can be used to mitigate various attacks,
including the ones described in Section 3.2.1 (Delay Attack),
Section 3.2.3 (Resource Segmentation Attack), and Section 3.2.8
(Time Sync Attack).
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For example, in the case of data plane delay attacks, one possible
mitigation is to timestamp the data at the source, and timestamp
it again at the destination, and if the resulting latency exceeds
the promised bound, discard that data and warn the operator (and/
or enter a fail-safe mode).
5.8. Mitigation Summary
The following table maps the attacks of Section 3 to the impacts of
Section 4, and to the mitigations of the current section. Each row
specifies an attack, the impact of this attack if it is successfully
implemented, and possible mitigation methods.
+----------------------+---------------------+---------------------+
| Attack | Impact | Mitigations |
+----------------------+---------------------+---------------------+
|Delay Attack |-Non-deterministic |-Path redundancy |
| | delay |-Performance |
| |-Data disruption | analytics |
| |-Increased resource | |
| | consumption | |
+----------------------+---------------------+---------------------+
|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 |
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|Attack Surface | attacks | protection |
+----------------------+---------------------+---------------------+
|Control or Signaling |-Increased resource |-Control message |
|Packet Modification | consumption | protection |
| |-Non-deterministic | |
| | delay | |
| |-Data disruption | |
+----------------------+---------------------+---------------------+
|Control or Signaling |-Increased resource |-Control message |
|Packet Injection | consumption | protection |
| |-Non-deterministic | |
| | delay | |
| |-Data disruption | |
+----------------------+---------------------+---------------------+
|Attacks on Time Sync |-Non-deterministic |-Path redundancy |
|Mechanisms | delay |-Control message |
| |-Increased resource | protection |
| | consumption |-Performance |
| |-Data disruption | analytics |
+----------------------+---------------------+---------------------+
Figure 3: Mapping Attacks to Impact and Mitigations
6. Association of Attacks to Use Cases
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.
6.1. Use Cases by Common Themes
In this section we review each theme and discuss the attacks that are
applicable to that theme, as well as anything specific about the
impact and mitigations for that attack with respect to that theme.
The table Figure 5 then provides a summary of the attacks that are
applicable to each theme.
6.1.1. Network Layer - AVB/TSN Ethernet
DetNet is expected to run over various transmission mediums, with
Ethernet being explicitly supported. Attacks such as Delay or
Reconnaissance might be implemented differently on a different
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transmission medium, however the impact on the DetNet as a whole
would be essentially the same. We thus conclude that all attacks and
impacts that would be applicable to DetNet over Ethernet (i.e. all
those named in this document) would also be applicable to DetNet over
other transmission mediums.
With respect to mitigations, some methods are specific to the
Ethernet medium, for example time-aware scheduling using 802.1Qbv can
protect against excessive use of bandwidth at the ingress - for other
mediums, other mitigations would have to be implemented to provide
analogous protection.
6.1.2. Central Administration
A DetNet network is expected to be controlled by a centralized
network configuration and control system (CNC). Such a system may be
in a single central location, or it may be distributed across
multiple control entities that function together as a unified control
system for the network.
In this document we distinguish between attacks on the DetNet Control
plane vs. Data plane. But is an attack affecting control plane
packets synonymous with an attack on the CNC itself? For purposes of
this document let us consider an attack on the CNC itself to be out
of scope, and consider all attacks named in this document which are
relevant to control plane packets to be relevant to this theme,
including Path Manipulation, Path Choice, Control Packet Modification
or Injection, Reconaissance and Attacks on Time Sync Mechanisms.
6.1.3. Hot Swap
A DetNet network is not expected to be "plug and play" - it is
expected that there is some centralized network configuration and
control system. However, the ability to "hot swap" components (e.g.
due to malfunction) is similar enough to "plug and play" that this
kind of behavior may be expected in DetNet networks, depending on the
implementation.
An attack surface related to Hot Swap is that the DetNet network must
at least consider input at runtime from devices that were not part of
the initial configuration of the network. Even a "perfect" (or
"hitless") replacement of a device at runtime would not necessarily
be ideal, since presumably one would want to distinguish it from the
original for OAM purposes (e.g. to report hot swap of a failed
device).
This implies that an attack such as Flow Modification, Spoofing or
Inter-segment (which could introduce packets from a "new" device
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(i.e. one heretofore unknown on the network) could be used to exploit
the need to consider such packets (as opposed to rejecting them out
of hand as one would do if one did not have to consider introduction
of a new device).
Similarly if the network was designed to support runtime replacement
of a clock device, then presence (or apparent presence) and thus
consideration of packets from a new such device could affect the
network, or the time sync of the network, for example by initiating a
new Best Master Clock selection process. Thus attacks on time sync
should be considered when designing hot swap type functionality.
6.1.4. Data Flow Information Models
Data Flow Information Models specific to DetNet networks are to be
specified by DetNet. Thus they are "new" and thus potentially
present a new attack surface. Does the threat take advantage of any
aspect of our new Data Flow Info Models?
This is TBD, thus there are no specific entries in our table, however
that does not imply that there could be no relevant attacks.
6.1.5. L2 and L3 Integration
A DetNet network integrates Layer 2 (bridged) networks (e.g. AVB/TSN
LAN) and Layer 3 (routed) networks via the use of well-known
protocols such as IP, MPLS-PW, and Ethernet.
There are no specific entries in our table, however that does not
imply that there could be no relevant attacks related to L2,L3
integration.
6.1.6. 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 Control plane attack, e.g.
Path Manipulation or Signaling Packet Modification.
It may be that such attacks are limited to Internal MITM attackers,
but other possibilities should be considered.
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An attack may also cause packets that should not be delivered to be
delivered, such as by forcing packets from one (e.g. replicated) path
to be preferred over another path when they should not be
(Replication attack), or by Flow Modification, or by Path Choice or
Packet Injection. A Time Sync attack could cause a system that was
expecting certain packets at certain times to accept unintended
packets based on compromised system time or time windowing in the
scheduler.
Packets may also be dropped due to malfunctioning software or
hardware.
6.1.7. Proprietary Deterministic Ethernet Networks
There are many proprietary non-interoperable deterministic Ethernet-
based networks currently available; DetNet is intended to provide an
open-standards-based alternative to such networks. In cases where a
DetNet intersects with remnants of such networks or their protocols,
such as by protocol emulation or access to such a network via a
gateway, new attack surfaces can be opened.
For example an Inter-Segment or Control 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.
6.1.8. Replacement for Proprietary Fieldbuses
There are many proprietary "field buses" used in today's industrial
and other industries; DetNet is intended to provide an open-
standards-based alternative to such buses. In cases where a DetNet
intersects with such fieldbuses or their protocols, such as by
protocol emulation or access via a gateway, new attack surfaces can
be opened.
For example an Inter-Segment or Control 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.
6.1.9. Deterministic vs Best-Effort Traffic
DetNet is intended to support coexistence of time-sensitive
operational (OT, deterministic) traffic and information (IT, "best
effort") traffic on the same ("unified") network.
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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.
Most of the themes described in this document address OT (reserved)
streams - this item is intended to address issues related to IT
traffic on a DetNet.
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 stream reservation
and isolation of the DetNet is well-designed (better-designed than
the attack) then interference with OT traffic should not result from
an attack that floods the network with IT traffic.
However the DetNet's handling of IT traffic may not (by design) be as
resilient to DOS attack, and thus designers must be otherwise
prepared to mitigate DOS attacks on IT traffic in a DetNet.
6.1.10. Deterministic Flows
Reserved bandwidth data flows (deterministic flows) must provide the
allocated bandwidth, and must be isolated from each other.
A Spoofing or Inter-segment attack which adds packet traffic to a
bandwidth-reserved stream could cause that stream to occupy more
bandwidth than it is allocated, resulting in interference with other
deterministic 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.
6.1.11. Unused Reserved Bandwidth
If bandwidth reservations are made for a stream but the associated
bandwidth is not used at any point in time, that bandwidth is made
available on the network for best-effort traffic. If the owner of
the reserved stream then starts transmitting again, the bandwidth is
no longer available for best-effort traffic, on a moment-to-moment
basis. (Such "temporarily available" bandwidth is not available for
time-sensitive traffic, which must have its own reservation).
An Inter-segment attack could flood the network with IT traffic,
interfering with the intended IT traffic.
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A Flow Modification or Spoofing or Control Packet Modification or
Injection attack could cause extra bandwidth to be reserved by a new
or existing stream, thus making it unavailable for use by best-effort
traffic.
6.1.12. Interoperability
The DetNet network specifications are intended to enable an ecosystem
in which multiple vendors can create interoperable products, thus
promoting device diversity and potentially higher numbers of each
device manufactured. Does the threat take advantage of differences
in implementation of "interoperable" products made by different
vendors?
This is TBD, thus there are no specific entries in our table, however
that does not imply that there could be no relevant attacks.
6.1.13. Cost Reductions
The DetNet network specifications are intended to enable an ecosystem
in which multiple vendors can create interoperable products, thus
promoting higher numbers of each device manufactured, promoting cost
reduction and cost competition among vendors. Does the threat take
advantage of "low cost" HW or SW components or other "cost-related
shortcuts" that might be present in devices?
This is TBD, thus there are no specific entries in our table, however
that does not imply that there could be no relevant attacks.
6.1.14. Insufficiently Secure Devices
The DetNet network specifications are intended to enable an ecosystem
in which multiple vendors can create interoperable products, thus
promoting device diversity and potentially higher numbers of each
device manufactured. Does the threat attack "naivete" of SW, for
example SW that was not designed to be sufficiently secure (or secure
at all) but is deployed on a DetNet network that is intended to be
highly secure? (For example IoT exploits like the Mirai video-camera
botnet ([MIRAI]).
This is TBD, thus there are no specific entries in our table, however
that does not imply that there could be no relevant attacks.
6.1.15. DetNet Network Size
DetNet networks range in size from very small, e.g. inside a single
industrial machine, to very large, for example a Utility Grid network
spanning a whole country.
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The size of the network might be related to how the attack is
introduced into the network, for example if the entire network is
local, there is a threat that power can be cut to the entire network.
If the network is large, perhaps only a part of the network is
attacked.
A Delay attack might be as relevant to a small network as to a large
network, although the amount of delay might be different.
Attacks sourced from IT traffic might be more likely in large
networks, since more people might have access to the network.
Similarly Path Manipulation, Path Choice and Time Sync attacks seem
more likely relevant to large networks.
6.1.16. Multiple Hops
Large DetNet networks (e.g. a Utility Grid network) may involve many
"hops" over various kinds of links for example radio repeaters,
microwave links, fiber optic links, etc..
An attack that takes advantage of flaws (or even normal operation) in
the device drivers for the various links (through internal knowledge
of how the individual driver or firmware operates, perhaps like the
Stuxnet attack) could take proportionately greater advantage of this
topology. We don't currently have an attack like this defined; we
have only "protocol" (time or packet) based attacks. Perhaps we need
to define an attack like this? Or is that out of scope for DetNet?
It is also possible that this DetNet topology will not be in as
common use as other more homogeneous topologies so there may be more
opportunity for attackers to exploit software and/or protocol flaws
in the implementations which have not been wrung out by extensive
use, particularly in the case of early adopters.
Of the attacks we have defined, the ones identified above as relevant
to "large" networks seem to be most relevant.
6.1.17. Level of Service
A DetNet is expected to provide means to configure the network that
include querying network path latency, requesting bounded latency for
a given stream, requesting worst case maximum and/or minimum latency
for a given path or stream, and so on. It is an expected case that
the network cannot provide a given requested service level. In such
cases the network control system should reply that the requested
service level is not available (as opposed to accepting the parameter
but then not delivering the desired behavior).
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Control plane attacks such as Signaling Packet Modification and
Injection could be used to modify or create control traffic that
could interfere with the process of a user requesting a level of
service and/or the network's reply.
Reconnaissance could be used to characterize flows and perhaps target
specific flows for attack via the Control plane as noted above.
6.1.18. Bounded Latency
DetNet provides the expectation of guaranteed bounded latency.
Delay attacks can cause packets to miss their agreed-upon latency
boundaries.
Time Sync attacks can corrupt the system's time reference, resulting
in missed latency deadlines (with respect to the "correct" time
reference).
6.1.19. Low Latency
Applications may require "extremely low latency" however depending on
the application these may mean very different latency values; for
example "low latency" across a Utility grid network is on a different
time scale than "low latency" in a motor control loop in a small
machine. The intent is that the mechanisms for specifying desired
latency include wide ranges, and that architecturally there is
nothing to prevent arbitrarily low latencies from being implemented
in a given network.
Attacks on the Control plane (as described in the Level of Service
theme) and Delay and Time attacks (as described in the Bounded
Latency theme) both apply here.
6.1.20. Bounded Jitter (Latency Variation)
DetNet is expected to provide bounded jitter (packet to packet
latency variation).
Delay attacks can cause packets to vary in their arrival times,
resulting in packet to packet latency variation, thereby violating
the jitter specification.
6.1.21. Symmetrical Path Delays
Some applications would like to specify that the transit delay time
values be equal for both the transmit and return paths.
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Delay attacks can cause path delays to differ.
Time Sync attacks can corrupt the system's time reference, resulting
in differing path delays (with respect to the "correct" time
reference).
6.1.22. Reliability and Availability
DetNet based systems are expected to be implemented with essentially
arbitrarily high availability (for example 99.9999% up time, or even
12 nines). The intent is that the DetNet designs should not make any
assumptions about the level of reliability and availability that may
be required of a given system, and should define parameters for
communicating these kinds of metrics within the network.
Any attack on the system, of any type, can affect its overall
reliability and availability, thus in our table we have marked every
attack. Since every DetNet depends to a greater or lesser degree on
reliability and availability, this essentially means that all
networks have to mitigate all attacks, which to a greater or lesser
degree defeats the purpose of associating attacks with use cases. It
also underscores the difficulty of designing "extremely high
reliability" networks.
6.1.23. Redundant Paths
DetNet based systems are expected to be implemented with essentially
arbitrarily high reliability/availability. A strategy used by DetNet
for providing such extraordinarily high levels of reliability is to
provide redundant paths that can be seamlessly switched between, all
the while maintaining the required performance of that system.
Replication-related attacks are by definition applicable here.
Control plane attacks can also interfere with the configuration of
redundant paths.
6.1.24. Security Measures
A DetNet network must be made secure against devices failures,
attackers, misbehaving devices, and so on. Does the threat affect
such security measures themselves, e.g. by attacking SW designed to
protect against device failure?
This is TBD, thus there are no specific entries in our table, however
that does not imply that there could be no relevant attacks.
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6.2. Attack Types by Use Case Common Theme
The following table lists the attacks of Section 3, assigning a
number to each type of attack. That number is then used as a short
form identifier for the attack in Figure 5.
+--+----------------------------------------+----------------------+
| | Attack | Section |
+--+----------------------------------------+----------------------+
| 1|Delay Attack | Section 3.2.1 |
+--+----------------------------------------+----------------------+
| 2|DetNet Flow Modification or Spoofing | Section 3.2.2 |
+--+----------------------------------------+----------------------+
| 3|Inter-Segment Attack | Section 3.2.3 |
+--+----------------------------------------+----------------------+
| 4|Replication: Increased attack surface | Section 3.2.4.1 |
+--+----------------------------------------+----------------------+
| 5|Replication-related Header Manipulation | Section 3.2.4.2 |
+--+----------------------------------------+----------------------+
| 6|Path Manipulation | Section 3.2.5.1 |
+--+----------------------------------------+----------------------+
| 7|Path Choice: Increased Attack Surface | Section 3.2.5.2 |
+--+----------------------------------------+----------------------+
| 8|Control or Signaling Packet Modification| Section 3.2.6.1 |
+--+----------------------------------------+----------------------+
| 9|Control or Signaling Packet Injection | Section 3.2.6.2 |
+--+----------------------------------------+----------------------+
|10|Reconnaissance | Section 3.2.7 |
+--+----------------------------------------+----------------------+
|11|Attacks on Time Sync Mechanisms | Section 3.2.8 |
+--+----------------------------------------+----------------------+
Figure 4: List of Attacks
The following table maps the use case themes presented in this memo
to the attacks of Figure 4. Each row specifies a theme, and the
attacks relevant to this theme are marked with a '+'.
+----------------------------+--------------------------------+
| Theme | Attack |
| +--+--+--+--+--+--+--+--+--+--+--+
| | 1| 2| 3| 4| 5| 6| 7| 8| 9|10|11|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Network Layer - AVB/TSN Eth.| +| +| +| +| +| +| +| +| +| +| +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Central Administration | | | | | | +| +| +| +| +| +|
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+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|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 | | | | | | | | | | | |
|Devices | | | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|DetNet Network Size | +| | | | | +| +| | | | +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Multiple Hops | +| +| | | | +| +| | | | +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Level of Service | | | | | | | | +| +| +| |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Bounded Latency | +| | | | | | | | | | +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Low Latency | +| | | | | | | +| +| +| +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Bounded Jitter | +| | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Symmetric Path Delays | +| | | | | | | | | | +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Reliability and Availability| +| +| +| +| +| +| +| +| +| +| +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Redundant Paths | | | | +| +| | | +| +| | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Security Measures | | | | | | | | | | | |
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+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
Figure 5: Mapping Between Themes and Attacks
6.3. Security Considerations for OAM Traffic
This section considers DetNet-specific security considerations for
packet traffic that is generated and transmitted over a DetNet as
part of OAM (Operations, Administration and Maintenance). For
purposes of this discussion, OAM traffic falls into one of two basic
types:
o OAM traffic generated by the network itself. The additional
bandwidth required for such packets is added by the network
administration, presumably transparent to the customer. Security
considerations for such traffic are not DetNet-specific (apart
from such traffic being subject to the same DetNet-specific
security considerations as any other DetNet data flow) and are
thus not covered in this document.
o OAM traffic generated by the customer. From a DetNet security
point of view, DetNet security considerations for such traffic are
exactly the same as for any other customer data flows.
Thus OAM traffic presents no additional (i.e. OAM-specific) DetNet
security considerations.
7. DetNet Technology-Specific Threats
Section 3 described threats which are independent of a DetNet
implementation. This section considers threats specifically related
to the IP- and MPLS-specific aspects of DetNet implementations.
The primary security considerations for the data plane specifically
are to maintain the integrity of the data and the delivery of the
associated DetNet service traversing the DetNet network.
The primary relevant differences between IP and MPLS implementations
are in flow identification and OAM methodologies.
As noted in [RFC8655], DetNet operates at the IP layer
([I-D.ietf-detnet-ip]) and delivers service over sub-layer
technologies such as MPLS ([I-D.ietf-detnet-mpls]) and IEEE 802.1
Time-Sensitive Networking (TSN) ([I-D.ietf-detnet-ip-over-tsn]).
Application flows can be protected through whatever means are
provided by the layer and sub-layer technologies. For example,
technology-specific encryption may be used, such as that provided by
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IPSec [RFC4301] for IP flows and/or by an underlying sub-net using
MACSec [IEEE802.1AE-2018] for IP over Ethernet (Layer-2) flows.
However, if the DetNet nodes cannot decrypt IPsec traffic, IPSec may
not be a valid option; this is because the DetNet IP data plane
identifies flows via a 6-tuple that consists of two IP addresses, the
transport protocol ID, two transport protocol port numbers and the
DSCP in the IP header. When IPsec is used, the transport header is
encrypted and the next protocol ID is an IPsec protocol, usually ESP,
and not a transport protocol (e.g., neither TCP nor UDP, etc.)
leaving only three components of the 6-tuple, which are the two IP
addresses and the DSCP, which are in general not sufficient to
identify a DetNet flow.
Sections below discuss threats specific to IP and MPLS in more
detail.
7.1. IP
The IP protocol has a long history of security considerations and
architectural protection mechanisms. From a data plane perspective
DetNet does not add or modify any IP header information, and its use
as a DetNet Data Plane does not introduce any new security issues
that were not there before, apart from those already described in the
data-plane-independent threats section Section 3.
Thus the security considerations for a DetNet based on an IP data
plane are purely inherited from the rich IP Security literature and
code/application base, and the data-plane-independent section of this
document.
Maintaining security for IP segments of a DetNet may be more
challenging than for the MPLS segments of the network, given that the
IP segments of the network may reach the edges of the network, which
are more likely to involve interaction with potentially malevolent
outside actors. Conversely MPLS is inherently more secure than IP
since it is internal to routers and it is well-known how to protect
it from outside influence.
Another way to look at DetNet IP security is to consider it in the
light of VPN security; as an industry we have a lot of experience
with VPNs running through networks with other VPNs, it is well known
how to secure the network for that. However for a DetNet we have the
additional subtlety that any possible interaction of one packet with
another can have a potentially deleterious effect on the time
properties of the flows. So the network must provide sufficient
isolation between flows, for example by protecting the forwarding
bandwidth and related resources so that they are available to detnet
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traffic, by whatever means are appropriate for that network's data
plane.
7.2. MPLS
An MPLS network carrying DetNet traffic is expected to be a "well-
managed" network. Given that this is the case, it is difficult for
an attacker to pass a raw MPLS encoded packet into a network because
operators have considerable experience at excluding such packets at
the network boundaries, as well as excluding MPLS packets being
inserted through the use of a tunnel.
MPLS security is discussed extensively in [RFC5920] ("Security
Framework for MPLS and GMPLS Networks") to which the reader is
referred.
[RFC6941] builds on [RFC5920] by providing additional security
considerations that are applicable to the MPLS-TP extensions
appropriate to the MPLS Transport Profile [RFC5921], and thus to the
operation of DetNet over some types of MPLS network.
[RFC5921] introduces to MPLS new Operations, Administration, and
Maintenance (OAM) capabilities, a transport-oriented path protection
mechanism, and strong emphasis on static provisioning supported by
network management systems.
The operation of DetNet over an MPLS network is modeled on the
operation of multi-segment pseudowires (MS-PW). Thus for guidance on
securing the DetNet elements of DetNet over MPLS the reader is
referred to the MS-PW security mechanisms as defined in [RFC4447],
[RFC3931], [RFC3985], [RFC6073], and [RFC6478].
Having attended to the conventional aspects of network security it is
necessary to attend to the dynamic aspects. The closest experience
that the IETF has with securing protocols that are sensitive to
manipulation of delay are the two way time transfer protocols (TWTT),
which are NTP [RFC5905] and Precision Time Protocol [IEEE1588]. The
security requirements for these are described in [RFC7384].
One particular problem that has been observed in operational tests of
TWTT protocols is the ability for two closely but not completely
synchronized streams to beat and cause a sudden phase hit to one of
the streams. 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.
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8. IANA Considerations
This memo includes no requests from IANA.
9. Security Considerations
The security considerations of DetNet networks are presented
throughout this document.
10. Informative References
[ARINC664P7]
ARINC, "ARINC 664 Aircraft Data Network, Part 7, Avionics
Full-Duplex Switched Ethernet Network", 2009.
[I-D.ietf-detnet-data-plane-framework]
Varga, B., Farkas, J., Berger, L., Fedyk, D., Malis, A.,
Bryant, S., and J. Korhonen, "DetNet Data Plane
Framework", draft-ietf-detnet-data-plane-framework-03
(work in progress), October 2019.
[I-D.ietf-detnet-ip]
Varga, B., Farkas, J., Berger, L., Fedyk, D., Malis, A.,
Bryant, S., and J. Korhonen, "DetNet Data Plane: IP",
draft-ietf-detnet-ip-04 (work in progress), November 2019.
[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-01 (work in
progress), October 2019.
[I-D.ietf-detnet-mpls]
Varga, B., Farkas, J., Berger, L., Fedyk, D., Malis, A.,
Bryant, S., and J. Korhonen, "DetNet Data Plane: MPLS",
draft-ietf-detnet-mpls-04 (work in progress), November
2019.
[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.
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[IEEE802.1AE-2018]
IEEE Standards Association, "IEEE Std 802.1AE-2018 MAC
Security (MACsec)", 2018,
<https://ieeexplore.ieee.org/document/8585421>.
[IEEE802.1Qch-2017]
IEEE Standards Association, "IEEE Standard for Local and
metropolitan area networks--Bridges and Bridged Networks--
Amendment 29: Cyclic Queuing and Forwarding", 2017,
<https://ieeexplore.ieee.org/document/7961303>.
[MIRAI] krebsonsecurity.com, "https://krebsonsecurity.com/2016/10/
hacked-cameras-dvrs-powered-todays-massive-internet-
outage/", 2016.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
<https://www.rfc-editor.org/info/rfc2475>.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552,
DOI 10.17487/RFC3552, July 2003,
<https://www.rfc-editor.org/info/rfc3552>.
[RFC3931] Lau, J., Ed., Townsley, M., Ed., and I. Goyret, Ed.,
"Layer Two Tunneling Protocol - Version 3 (L2TPv3)",
RFC 3931, DOI 10.17487/RFC3931, March 2005,
<https://www.rfc-editor.org/info/rfc3931>.
[RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
Edge-to-Edge (PWE3) Architecture", RFC 3985,
DOI 10.17487/RFC3985, March 2005,
<https://www.rfc-editor.org/info/rfc3985>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <https://www.rfc-editor.org/info/rfc4301>.
[RFC4447] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and
G. Heron, "Pseudowire Setup and Maintenance Using the
Label Distribution Protocol (LDP)", RFC 4447,
DOI 10.17487/RFC4447, April 2006,
<https://www.rfc-editor.org/info/rfc4447>.
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[RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
"Network Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
<https://www.rfc-editor.org/info/rfc5905>.
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
<https://www.rfc-editor.org/info/rfc5920>.
[RFC5921] Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau,
L., and L. Berger, "A Framework for MPLS in Transport
Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010,
<https://www.rfc-editor.org/info/rfc5921>.
[RFC6073] Martini, L., Metz, C., Nadeau, T., Bocci, M., and M.
Aissaoui, "Segmented Pseudowire", RFC 6073,
DOI 10.17487/RFC6073, January 2011,
<https://www.rfc-editor.org/info/rfc6073>.
[RFC6478] Martini, L., Swallow, G., Heron, G., and M. Bocci,
"Pseudowire Status for Static Pseudowires", RFC 6478,
DOI 10.17487/RFC6478, May 2012,
<https://www.rfc-editor.org/info/rfc6478>.
[RFC6941] Fang, L., Ed., Niven-Jenkins, B., Ed., Mansfield, S., Ed.,
and R. Graveman, Ed., "MPLS Transport Profile (MPLS-TP)
Security Framework", RFC 6941, DOI 10.17487/RFC6941, April
2013, <https://www.rfc-editor.org/info/rfc6941>.
[RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in
Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384,
October 2014, <https://www.rfc-editor.org/info/rfc7384>.
[RFC8578] Grossman, E., Ed., "Deterministic Networking Use Cases",
RFC 8578, DOI 10.17487/RFC8578, May 2019,
<https://www.rfc-editor.org/info/rfc8578>.
[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>.
Authors' Addresses
Tal Mizrahi
Huawei Network.IO Innovation Lab
Email: tal.mizrahi.phd@gmail.com
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Ethan Grossman (editor)
Dolby Laboratories, Inc.
1275 Market Street
San Francisco, CA 94103
USA
Phone: +1 415 645 4726
Email: ethan.grossman@dolby.com
URI: http://www.dolby.com
Andrew J. Hacker
MistIQ Technologies, Inc
Harrisburg, PA
USA
Phone:
Email: ajhacker@mistiqtech.com
URI: http://www.mistiqtech.com
Subir Das
Applied Communication Sciences
150 Mount Airy Road, Basking Ridge
New Jersey, 07920
USA
Email: sdas@appcomsci.com
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
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Norman Finn
Huawei
Email: norman.finn@mail01.huawei.com
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