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Versions: (draft-sdt-detnet-security) 00 01
02 03 04 05 06 07 08 09 10 11 12
Internet Engineering Task Force E. Grossman, Ed.
Internet-Draft DOLBY
Intended status: Informational T. Mizrahi
Expires: April 5, 2021 HUAWEI
A. Hacker
MISTIQ
October 2, 2020
Deterministic Networking (DetNet) Security Considerations
draft-ietf-detnet-security-12
Abstract
A DetNet (deterministic network) provides specific performance
guarantees to its data flows, such as extremely low data loss rates
and bounded latency. As a result, securing a DetNet requires that in
addition to the best practice security measures taken for any
mission-critical network, additional security measures may be needed
to secure the intended operation of these novel service properties.
This document addresses DetNet-specific security considerations from
the perspectives of both the DetNet system-level designer and
component designer. System considerations include a threat model,
taxonomy of relevant attacks, and associations of threats versus use
cases and service properties. Component-level considerations include
ingress filtering and packet arrival time violation detection. This
document also addresses DetNet security considerations specific to
the IP and MPLS data plane technologies thereby complementing the
Security Considerations sections of the various DetNet Data Plane
(and other) DetNet documents.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at 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 April 5, 2021.
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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 . . . . . 6
3.1. Resource Allocation . . . . . . . . . . . . . . . . . . . 7
3.2. Explicit Routes . . . . . . . . . . . . . . . . . . . . . 7
3.3. Redundant Path Support . . . . . . . . . . . . . . . . . 8
3.4. Timing (or other) Violation Reporting . . . . . . . . . . 9
4. DetNet Security Considerations Compared With DiffServ
Security Considerations . . . . . . . . . . . . . . . . . . . 9
5. Security Threats . . . . . . . . . . . . . . . . . . . . . . 10
5.1. Threat Model . . . . . . . . . . . . . . . . . . . . . . 11
5.2. Threat Analysis . . . . . . . . . . . . . . . . . . . . . 12
5.2.1. Delay . . . . . . . . . . . . . . . . . . . . . . . . 12
5.2.2. DetNet Flow Modification or Spoofing . . . . . . . . 12
5.2.3. Resource Segmentation (Inter-segment Attack) . . . . 12
5.2.4. Packet Replication and Elimination . . . . . . . . . 12
5.2.4.1. Replication: Increased Attack Surface . . . . . . 12
5.2.4.2. Replication-related Header Manipulation . . . . . 12
5.2.5. Controller Plane . . . . . . . . . . . . . . . . . . 13
5.2.5.1. Path Choice Manipulation . . . . . . . . . . . . 13
5.2.5.2. Compromised Controller . . . . . . . . . . . . . 14
5.2.6. Reconnaissance . . . . . . . . . . . . . . . . . . . 14
5.2.7. Time Synchronization Mechanisms . . . . . . . . . . . 14
5.3. Threat Summary . . . . . . . . . . . . . . . . . . . . . 14
6. Security Threat Impacts . . . . . . . . . . . . . . . . . . . 15
6.1. Delay-Attacks . . . . . . . . . . . . . . . . . . . . . . 18
6.1.1. Data Plane Delay Attacks . . . . . . . . . . . . . . 18
6.1.2. Controller Plane Delay Attacks . . . . . . . . . . . 19
6.2. Flow Modification and Spoofing . . . . . . . . . . . . . 19
6.2.1. Flow Modification . . . . . . . . . . . . . . . . . . 19
6.2.2. Spoofing . . . . . . . . . . . . . . . . . . . . . . 19
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6.2.2.1. Dataplane Spoofing . . . . . . . . . . . . . . . 19
6.2.2.2. Controller Plane Spoofing . . . . . . . . . . . . 20
6.3. Segmentation Attacks (injection) . . . . . . . . . . . . 20
6.3.1. Data Plane Segmentation . . . . . . . . . . . . . . . 20
6.3.2. Controller Plane Segmentation . . . . . . . . . . . . 20
6.4. Replication and Elimination . . . . . . . . . . . . . . . 21
6.4.1. Increased Attack Surface . . . . . . . . . . . . . . 21
6.4.2. Header Manipulation at Elimination Routers . . . . . 21
6.5. Control or Signaling Packet Modification . . . . . . . . 21
6.6. Control or Signaling Packet Injection . . . . . . . . . . 21
6.7. Reconnaissance . . . . . . . . . . . . . . . . . . . . . 21
6.8. Attacks on Time Sync Mechanisms . . . . . . . . . . . . . 22
6.9. Attacks on Path Choice . . . . . . . . . . . . . . . . . 22
7. Security Threat Mitigation . . . . . . . . . . . . . . . . . 22
7.1. Path Redundancy . . . . . . . . . . . . . . . . . . . . . 22
7.2. Integrity Protection . . . . . . . . . . . . . . . . . . 22
7.3. DetNet Node Authentication . . . . . . . . . . . . . . . 23
7.4. Dummy Traffic Insertion . . . . . . . . . . . . . . . . . 24
7.5. Encryption . . . . . . . . . . . . . . . . . . . . . . . 24
7.5.1. Encryption Considerations for DetNet . . . . . . . . 24
7.6. Control and Signaling Message Protection . . . . . . . . 25
7.7. Dynamic Performance Analytics . . . . . . . . . . . . . . 26
7.8. Mitigation Summary . . . . . . . . . . . . . . . . . . . 27
8. Association of Attacks to Use Cases . . . . . . . . . . . . . 28
8.1. Association of Attacks to Use Case Common Themes . . . . 28
8.1.1. Sub-Network Layer . . . . . . . . . . . . . . . . . . 28
8.1.2. Central Administration . . . . . . . . . . . . . . . 29
8.1.3. Hot Swap . . . . . . . . . . . . . . . . . . . . . . 29
8.1.4. Data Flow Information Models . . . . . . . . . . . . 30
8.1.5. L2 and L3 Integration . . . . . . . . . . . . . . . . 30
8.1.6. End-to-End Delivery . . . . . . . . . . . . . . . . . 30
8.1.7. Replacement for Proprietary Fieldbuses and Ethernet-
based Networks . . . . . . . . . . . . . . . . . . . 31
8.1.8. Deterministic vs Best-Effort Traffic . . . . . . . . 31
8.1.9. Deterministic Flows . . . . . . . . . . . . . . . . . 32
8.1.10. Unused Reserved Bandwidth . . . . . . . . . . . . . . 32
8.1.11. Interoperability . . . . . . . . . . . . . . . . . . 32
8.1.12. Cost Reductions . . . . . . . . . . . . . . . . . . . 32
8.1.13. Insufficiently Secure Devices . . . . . . . . . . . . 33
8.1.14. DetNet Network Size . . . . . . . . . . . . . . . . . 33
8.1.15. Multiple Hops . . . . . . . . . . . . . . . . . . . . 34
8.1.16. Level of Service . . . . . . . . . . . . . . . . . . 34
8.1.17. Bounded Latency . . . . . . . . . . . . . . . . . . . 34
8.1.18. Low Latency . . . . . . . . . . . . . . . . . . . . . 35
8.1.19. Bounded Jitter (Latency Variation) . . . . . . . . . 35
8.1.20. Symmetrical Path Delays . . . . . . . . . . . . . . . 35
8.1.21. Reliability and Availability . . . . . . . . . . . . 35
8.1.22. Redundant Paths . . . . . . . . . . . . . . . . . . . 36
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8.1.23. Security Measures . . . . . . . . . . . . . . . . . . 36
8.2. Summary of Attack Types per Use Case Common Theme . . . . 36
8.3. Security Considerations for OAM Traffic . . . . . . . . . 39
9. DetNet Technology-Specific Threats . . . . . . . . . . . . . 39
9.1. IP . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
9.2. MPLS . . . . . . . . . . . . . . . . . . . . . . . . . . 41
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 42
11. Security Considerations . . . . . . . . . . . . . . . . . . . 42
12. Privacy Considerations . . . . . . . . . . . . . . . . . . . 42
13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 42
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 43
14.1. Normative References . . . . . . . . . . . . . . . . . . 43
14.2. Informative References . . . . . . . . . . . . . . . . . 44
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 47
1. Introduction
A deterministic network is one that can carry data flows for real-
time applications with extremely low data loss rates and bounded
latency. Deterministic networks have been successfully deployed in
real-time Operational Technology (OT) applications for some years.
However, such networks are typically isolated from external access,
and thus the security threat from external attackers is low. IETF
Deterministic Networking (DetNet, [RFC8655]) specifies a set of
technologies that enable creation of deterministic networks on IP-
based networks of potentially wide area (on the scale of a corporate
network) potentially bringing the OT network into contact with
Information Technology (IT) traffic and security threats that lie
outside of a tightly controlled and bounded area (such as the
internals of an aircraft).
These DetNet technologies have not previously been deployed together
on a wide area IP-based network, and thus can present security
considerations that may be new to IP-based wide area network
designers; this document provides insight into such system-level
security considerations. In addition, designers of DetNet components
(such as routers) face new security-related challenges in providing
DetNet services, for example maintaining reliable isolation between
traffic flows in an environment where IT traffic co-mingles with
critical reserved-bandwidth OT traffic; this document also examines
security implications internal to DetNet components.
Security is of particularly high importance in DetNet networks
because many of the use cases which are enabled by DetNet [RFC8578]
include control of physical devices (power grid components,
industrial controls, building controls) which can have high
operational costs for failure, and present potentially attractive
targets for cyber-attackers.
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This situation is even more acute given that one of the goals of
DetNet is to provide a "converged network", i.e. one that includes
both IT traffic and OT traffic, thus exposing potentially sensitive
OT devices to attack in ways that were not previously common (usually
because they were under a separate control system or otherwise
isolated from the IT network, for example [ARINC664P7]). Security
considerations for OT networks are not a new area, and there are many
OT networks today that are connected to wide area networks or the
Internet; this document focuses on the issues that are specific to
the DetNet technologies and use cases.
Given the above considerations, securing a DetNet starts with a
scrupulously well-designed and well-managed engineered network
following industry best practices for security at both the data plane
and controller plane; this is the assumed starting point for the
considerations discussed herein. Such assumptions also depend on the
network components themselves upholding the security-related
properties that are to be assumed by DetNet system-level designers;
for example, the assumption that network traffic associated with a
given flow can never affect traffic associated with a different flow
is only true if the underlying components make it so. Such
properties, which may represent new challenges to component
designers, are also considered herein.
In this context we view the network design and management aspects of
network security as being primarily concerned with denial-of service
prevention by ensuring that DetNet traffic goes where it's supposed
to and that an external attacker can't inject traffic that disrupts
the DetNet's delivery timing assurance. The time-specific aspects of
DetNet security presented here take up where the design and
management aspects leave off.
The exact security requirements for any given DetNet network are
necessarily specific to the use cases handled by that network. Thus
the reader is assumed to be familiar with the specific security
requirements of their use cases, for example those outlined in the
DetNet Use Cases [RFC8578] and the Security Considerations sections
of the DetNet documents applicable to the network technologies in
use, for example [I-D.ietf-detnet-ip]). A general introduction to
the DetNet architecture can be found in [RFC8655] and it is also
recommended to be familiar with the DetNet Data Plane
[I-D.ietf-detnet-data-plane-framework] and Flow Information Model
[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
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o Provide explicit routes for DetNet flows that do not dynamically
change with the network topology in ways that affect the quality
of service received by the affected flow(s)
o Distribute data from DetNet flow packets over time and/or space to
ensure delivery of each packet's data' in spite of the loss of a
path
This document includes sections considering DetNet component design
as well as system design. The latter includes threat modeling and
analysis, threat impact and mitigation, and the association of
attacks with use cases (based on the Use Case Common Themes section
of the DetNet Use Cases [RFC8578]).
The structure of the threat model and threat analysis sections were
originally derived from [RFC7384], which also considers time-related
security considerations in IP networks.
2. Abbreviations and Terminology
IT Information Technology (the application of computers to
store, study, retrieve, transmit, and manipulate data or information,
often in the context of a business or other enterprise - [IT_DEF]).
OT Operational Technology (the hardware and software
dedicated to detecting or causing changes in physical processes
through direct monitoring and/or control of physical devices such as
valves, pumps, etc. - [OT_DEF])
Component A component of a DetNet system - used here to refer
to any hardware or software element of a DetNet network which
implements DetNet-specific functionality, for example all or part of
a router, switch, or end system.
Resource Segmentation Used as a more general form for Network
Segmentation (the act or practice of splitting a computer network
into subnetworks, each being a network segment - [RS_DEF])
3. Security Considerations for DetNet Component Design
As noted above, DetNet provides resource allocation, explicit routes
and redundant path support. Each of these has associated security
implications, which are discussed in this section, in the context of
component design. Detection, reporting and appropriate action in the
case of packet arrival time violations are also discussed.
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3.1. Resource Allocation
A DetNet system security designer relies on the premise that any
resources allocated to a resource-reserved (OT-type) flow are
inviolable, in other words there is no physical possibility within a
DetNet component that resources allocated to a given flow can be
compromised by any type of traffic in the network; this includes both
malicious traffic as well as inadvertent traffic such as might be
produced by a malfunctioning component, for example one made by a
different manufacturer. From a security standpoint, this is a
critical assumption, for example when designing against DOS attacks.
It is the responsibility of the component designer to ensure that
this condition is met; this implies protection against excess traffic
from adjacent flows, and against compromises to the resource
allocation/deallocation process, for example through the use of
traffic shaping and policing.
As an example, consider the implementation of Flow Aggregation for
DetNet flows (as discussed in
[I-D.ietf-detnet-data-plane-framework]). In this example say there
are N flows that are to be aggregated, thus the bandwidth resources
of the aggregate flow must be sufficient to contain the sum of the
bandwidth reservation for the N flows. However if one of those flows
were to consume more than its individually allocated BW, this could
cause starvation of the other flows. Thus simply providing and
enforcing the calculated aggregate bandwidth may not be a complete
solution - the bandwidth for each individual flow must still be
guaranteed, for example via ingress policing of each flow (i.e.
before it is aggregated). Alternatively, if by some other means each
flow to be aggregated can be trusted not to exceed its allocated
bandwidth, the same goal can be achieved.
3.2. Explicit Routes
The DetNet-specific purpose for constraining the network's ability to
re-route OT traffic is to maintain the specified service parameters
(such as upper and lower latency boundaries) for a given flow. For
example if the network were to re-route a flow (or some part of a
flow) based exclusively on statistical path usage metrics, or due to
malicious activity, it is possible that the new path would have a
latency that is outside the required latency bounds which were
designed into the original TE-designed path, thereby violating the
quality of service for the affected flow (or part of that flow).
However, it is acceptable for the network to re-route OT traffic in
such a way as to maintain the specified latency bounds (and any other
specified service properties) for any reason, for example in response
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to a runtime component or path failure. From a security standpoint,
the system designer relies on the premise that the packets will be
delivered with the specified latency boundaries; thus any component
that is involved in controlling or implementing any change of the
initially TE-configured flow routes needs to prevent malicious or
accidental re-routing of OT flows that might adversely affect
delivering the traffic within the specified service parameters.
3.3. Redundant Path Support
The DetNet provision for redundant paths (PREOF) (as defined in the
DetNet Architecture [RFC8655]) provides the foundation for high
reliablity of a DetNet, by virtually eliminating packet loss (i.e. to
a degree which is implementation-dependent) through hitless redundant
packet delivery. (Note that PREOF is not defined for a DetNet IP
data plane).
It is the responsibility of the system designer to determine the
level of reliability required by their use case, and to specify
redundant paths sufficient to provide the desired level of
reliability (in as much as that reliability can be provided through
the use of redundant paths). It is the responsibility of the
component designer to ensure that the relevant PREOF operations are
executed reliably and securely, to avoid potentially catastrophic
situations for the operational technology relying on them.
However, note that not all PREOF operations are necessarily
implemented in every network; for example a packet re-ordering
function may not be necessary if the packets are either not required
to be in order, or if the ordering is performed in some other part of
the network.
Ideally a redundant path could be specified from end to end of the
flow's path, however given that this is not always possible (as
described in [RFC8655]) the system designer will need to consider the
resulting end-to-end reliability and security resulting from any
given arrangment of network segments along the path, each of which
provides its individual PREOF implementation and thus its individual
level of reliabiilty and security.
At the data plane the implementation of PREOF depends on the correct
assignment and interpretation of packet sequence numbers, as well as
the actions taken based on them, such as elimination (including
elimination of packets with spurious sequence numbers). Thus the
integrity of these values must be maintained by the component as they
are assigned by the DetNet Data Plane's Service sub-layer, and
transported by the Forwarding sub-layer. This is no different than
the integrity of the values in any header used by the DetNet (or any
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other) data plane, and is not unique to redundant paths. From the
sequence number injection perspective, it is no different from any
other protocols that use sequence numbers.
3.4. Timing (or other) Violation Reporting
Another fundamental assumption of a secure DetNet is that in any case
in which an incoming packet arrives with any timing or bandwidth
violation, something can be done about it which doesn't cause damage
to the system. For example having the network shut down a link if a
packet arrives outside of its prescribed time window may serve the
attacker better than it serves the network. That means that the
component's data plane must be able to detect and act on a variety of
such violations, at least alerting the controller plane. Any action
apart from that needs to be carefully considered in the context of
the specific system. Some possible violations that warrant detection
include cases where a packet arrives:
o Outside of its prescribed time window
o Within its time window but with a compromised time stamp that
makes it appear that it is not within its window
o Exceeding the reserved flow bandwidth
Logging of such issues is unlikely to be adequate, since a delay in
response to the situation could result in material damage, for
example to mechanical devices controlled by the network. Given that
the data plane component probably has no knowledge of the use case of
the network, or its applications and end systems, it would seem
useful for a data plane component to allow the system designer to
configure its actions in the face of such violations.
Possible direct actions that may be taken at the data plane include
dropping the packet and/or shutting down the link; however if any
such actions are configured to be taken, the system designer must
ensure that such actions do not compromise the continued safe
operation of the system. For example, the controller plane should
mitigate in a timely fashion any potential adverse effect on
mechanical devices controlled by the network.
4. DetNet Security Considerations Compared With DiffServ Security
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
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interpretation of the DSCP value for OT traffic is not equivalent to
the PHB selection behavior as defined by DiffServ.
Thus security consideration for DetNet have some aspects in common
with DiffServ, in fact overlapping 100% with respect to IP IT
traffic. Security considerations for these aspects are part of the
existing literature on IP network security, specifically the Security
sections of [RFC2474] and [RFC2475]. However DetNet also introduces
timing and other considerations which are not present in DiffServ, so
the DiffServ security considerations are necessary but not sufficient
for DetNet.
In the case of DetNet OT traffic, the DSCP value, although
interpreted differently than in DiffServ, does contribute to
determination of the service provided to the packet. Thus in DetNet
there are similar consequences to DiffServ for lack of detection of,
or incorrect handling of, packets with mismarked DSCP values, and
thus many of the points made in the DiffServ draft Security
discussions are also relevant to DetNet OT traffic, though perhaps in
modified form. For example, in DetNet the effect of an undetected or
incorrectly handled maliciously mismarked DSCP field in an OT packet
is not identical to affecting that packet's PHB, since DetNet does
not use the PHB concept for OT traffic, but nonetheless the service
provided to the packet could be affected, so mitigation measures
analogous to those prescribed by DiffServ would be appropriate for
DetNet. For example, mismarked DSCP values should not cause failure
of network nodes, and any internal link that cannot be adequately
secured against modification of DSCP values should be treated as a
boundary link (and hence any arriving traffic on that link is treated
as if it were entering the domain at an ingress node). The remarks
in [RFC2474] regarding IPsec and Tunnelling Interactions are also
relevant (though this is not to say that other sections are less
relevant).
5. Security Threats
This section presents a threat model, and analyzes the possible
threats in a DetNet-enabled network. The threats considered in this
section are independent of any specific technologies used to
implement the DetNet; Section 9 considers attacks that are associated
with the DetNet technologies encompassed by
[I-D.ietf-detnet-data-plane-framework].
We distinguish controller plane threats from data plane threats. The
attack surface may be the same, but the types of attacks as well as
the motivation behind them, are different. For example, a delay
attack is more relevant to data plane than to controller plane.
There is also a difference in terms of security solutions: the way
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you secure the data plane is often different than the way you secure
the controller plane.
5.1. Threat Model
The threat model used in this memo employs organizational elements of
the threat models of [RFC7384] and [RFC7835] . This model classifies
attackers based on two criteria:
o Internal vs. external: internal attackers either have access to a
trusted segment of the network or possess the encryption or
authentication keys. External attackers, on the other hand, do
not have the keys and have access only to the encrypted or
authenticated traffic.
o On-path vs. off-path: on-path attackers are located in a position
that allows interception and modification of in-flight protocol
packets, whereas off-path attackers can only attack by generating
protocol packets.
Care has also been taken to adhere to Section 5 of [RFC3552], both
with respect to which attacks are considered out-of-scope for this
document, but also which are considered to be the most common threats
(explored further in Section 5.2, Threat Analysis). Most of the
direct threats to DetNet are active attacks (i.e. attacks that modify
DetNet traffic), but it is highly suggested that DetNet application
developers take appropriate measures to protect the content of the
DetNet flows from passive attacks (i.e. attacks that observe but do
not modify DetNet traffic) for example through the use of TLS or
DTLS.
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.
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5.2. Threat Analysis
5.2.1. Delay
An attacker can maliciously delay DetNet data flow traffic. By
delaying the traffic, the attacker can compromise the service of
applications that are sensitive to high delays or to high delay
variation. The delay may be constant or modulated.
5.2.2. DetNet Flow Modification or Spoofing
An attacker can modify some header fields of en route packets in a
way that causes the DetNet flow identification mechanisms to
misclassify the flow. Alternatively, the attacker can inject traffic
that is tailored to appear as if it belongs to a legitimate DetNet
flow. The potential consequence is that the DetNet flow resource
allocation cannot guarantee the performance that is expected when the
flow identification works correctly.
5.2.3. Resource Segmentation (Inter-segment Attack)
An attacker can inject traffic that will consume network resources
such that it affects DetNet flows. This can be performed using non-
DetNet traffic that indirectly affects DetNet traffic (hardware
resource exhaustion), or by using DetNet traffic from one DetNet flow
that directly affects traffic from different DetNet flows.
5.2.4. Packet Replication and Elimination
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.
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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.
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.
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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.
Note that in some cases DetNet flows may be identified based on an
explicit DetNet header, but in some cases the flow identification may
be based on fields from the L3/L4 headers. If L3/L4 headers are
involved, for the purposes of this document we assume they are
encrypted and/or integrity-protected from external attackers.
5.2.7. Time Synchronization Mechanisms
An attacker can use any of the attacks described in [RFC7384] to
attack the synchronization protocol, thus affecting the DetNet
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 Sync Mechanisms | + | + | + | + |
+-----------------------------------------+----+----+----+----+
Figure 1: Threat Analysis Summary
6. Security Threat Impacts
This section describes and rates the impact of the attacks described
in Section 5, Security Threats. In this section, the impacts as
described assume that the associated mitigation is not present or has
failed. Mitigations are discussed in Section 7, Security Threat
Mitigation.
In computer security, the impact (or consequence) of an incident can
be measured in loss of confidentiality, integrity or availability of
information. In the case of time sensitive networks, the impact of a
network exploit can also include failure or malfunction of mechanical
and/or other OT systems.
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 the DetNet Use Cases [RFC8578]. Each of these use cases is
represented in the table below, including Pro Audio, Electrical
Utilities, Industrial M2M (split into two areas, M2M Data Gathering
and M2M Control Loop), and others.
Components of Impact (left column) include Criticality of Failure,
Effects of Failure, Recovery, and DetNet Functional Dependence.
Criticality of failure summarizes the seriousness of the impact. The
impact of a resulting failure can affect many different metrics that
vary greatly in scope and severity. In order to reduce the number of
variables, only the following were included: Financial, Health and
Safety, People well being (People WB), Affect on a single
organization, and affect on multiple organizations. Recovery
outlines how long it would take for an affected use case to get back
to its pre-failure state (Recovery time objective, RTO), and how much
of the original service would be lost in between the time of service
failure and recovery to original state (Recovery Point Objective,
RPO). DetNet dependence maps how much the following DetNet service
objectives contribute to impact of failure: Time dependency, data
integrity, source node integrity, availability, latency/jitter.
The scale of the Impact mappings is low, medium, and high. In some
use cases there may be a multitude of specific applications in which
DetNet is used. For simplicity this section attempts to average the
varied impacts of different applications. This section does not
address the overall risk of a certain impact which would require the
likelihood of a failure happening.
In practice any such ratings will vary from case to case; the ratings
shown here are given as examples.
Table, Part One (of Two)
+------------------+-----------------------------------------+-----+
| | Pro A | Util | Bldg |Wire- | Cell |M2M |M2M |
| | | | | less | |Data |Ctrl |
+------------------+-----------------------------------------+-----+
| Criticality | Med | Hi | Low | Med | Med | Med | Med |
+------------------+-----------------------------------------+-----+
| Effects
+------------------+-----------------------------------------+-----+
| Financial | Med | Hi | Med | Med | Low | Med | Med |
+------------------+-----------------------------------------+-----+
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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, the
machine's control loop can become unstable.
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6.1.2. Controller Plane Delay Attacks
In and of itself, this is not directly a threat to the DetNet
service, but the effects of delaying control messages can have quite
adverse effects later.
o Delayed tear-down can lead to resource leakage, which in turn can
result in failure to allocate new DetNet flows, finally giving
rise to a denial of service attack.
o Failure to deliver, or severely delaying, controller plane
messages adding an endpoint to a multicast-group will prevent the
new endpoint from receiving expected frames thus disrupting
expected behavior.
o Delaying messages removing an endpoint from a group can lead to
loss of privacy as the endpoint will continue to receive messages
even after it is supposedly removed.
6.2. Flow Modification and Spoofing
6.2.1. Flow Modification
If the contents of a packet header or body can be modified by the
attacker, this can cause the packet to be routed incorrectly or
dropped, or the payload to be corrupted or subtly modified.
6.2.2. Spoofing
6.2.2.1. Dataplane Spoofing
Spoofing dataplane messages can result in increased resource
consumptions on the routers throughout the network as it will
increase buffer usage and processor utilization. This can lead to
resource exhaustion and/or increased delay.
If the attacker manages to create valid headers, the false messages
can be forwarded through the network, using part of the allocated
bandwidth. This in turn can cause legitimate messages to be dropped
when the resource budget has been exhausted.
Finally, the endpoint will have to deal with invalid messages being
delivered to the endpoint instead of (or in addition to) a valid
message.
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6.2.2.2. Controller Plane Spoofing
A successful controller plane spoofing-attack will potentionally have
adverse effects. It can do virtually anything from:
o modifying existing DetNet flows by changing the available
bandwidth
o add or remove endpoints from a DetNet flow
o drop DetNet flows completely
o falsely create new DetNet flows (exhaust the systems resources, or
to enable DetNet flows that are outside the Network Engineer's
control)
6.3. Segmentation Attacks (injection)
6.3.1. Data Plane Segmentation
Injection of false messages in a DetNet flow could lead to exhaustion
of the available bandwidth for that flow if the routers attribute
these false messages to that flow's budget.
In a multipath scenario, injected messages will cause increased
processor utilization in elimination routers. If enough paths are
subject to malicious injection, the legitimate messages can be
dropped. Likewise it can cause an increase in buffer usage. In
total, it will consume more resources in the routers than normal,
giving rise to a resource exhaustion attack on the routers.
If a DetNet flow is interrupted, the end application will be affected
by what is now a non-deterministic flow.
6.3.2. Controller Plane Segmentation
In a successful controller plane segmentation attack, control
messages are acted on by nodes in the network, unbeknownst to the
central controller or the network engineer. This has the potential
to:
o create new DetNet flows (exhausting resources)
o drop existing DetNet flows (denial of service)
o add 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 Sync Mechanisms
Attacks on time sync mechanisms are addressed in [RFC7384].
6.9. Attacks on Path Choice
This is covered in part in Section 6.3, Segmentation Attacks, and as
with Replication and Elimination (Section 6.4), this is relevant for
DataPlane messages.
7. Security Threat Mitigation
This section describes a set of measures that can be taken to
mitigate the attacks described in Section 5, Security Threats. These
mitigations should be viewed as a toolset that includes several
different and diverse tools. Each application or system will
typically use a subset of these tools, based on a system-specific
threat analysis.
7.1. Path Redundancy
Description
A DetNet flow that can be forwarded simultaneously over multiple
paths. Path replication and elimination [RFC8655] provides
resiliency to dropped or delayed packets. This redundancy
improves the robustness to failures and to 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
and thus might expose flaws in the system that might otherwise not
be exposed.
7.2. Integrity Protection
Description
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An integrity protection mechanism, such as a hash-based Message
Authentication Code (MAC) can be used to mitigate modification
attacks on IP packets. Such MAC usage needs to be part of a
security association that is established and managed by a security
association protocol (such as IKEv2 for IPsec security
associations). Integrity protection in the controller plane is
discussed in Section 7.6.
Packet Sequence Number Integrity Considerations
The use of PREOF in a DetNet implementation implies the use of a
sequence number for each packet. There is a trust relationship
between the device that adds the sequence number and the device
that removes the sequence number. The sequence number may be end-
to-end source to destination, or may be added/deleted by network
edge devices. The adder and remover(s) have the trust
relationship because they are the ones that ensure that the
sequence numbers are not modifiable. Between those two points,
there may or may not be replication and elimination functions.
The elimination functions must be able to see the sequence
numbers. Therefore any encryption that is done between adders and
removers must not obscure the sequence number. If the sequence
removers and the eliminators are in the same physical device, it
may be possible to obscure the sequence number, however that is a
layer violation, and is not recommended practice. Note: At the
time of this writing, PREOF is not defined for the IP data plane.
Related attacks
Integrity protection mitigates attacks related to modification and
tampering, including the attacks described in Section 5.2.2 and
Section 5.2.4.
7.3. DetNet Node Authentication
Description
Authentication verifies the identity of DetNet nodes (including
DetNet Controller Plane nodes), enabling mitigation of spoofing
attacks. Note that while integrity protection (Section 7.2)
prevents intermediate nodes from modifying information,
authentication (such as provided by IPsec or MACsec) can provide
traffic origin verification, i.e. to verify that each packet in a
DetNet flow is from a trusted source.
Related attacks
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DetNet node authentication is used to mitigate attacks related to
spoofing, including the attacks of Section 5.2.2, and
Section 5.2.4.
7.4. Dummy Traffic Insertion
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.
7.5. Encryption
Description
DetNet flows can in principle be forwarded in encrypted form at
the DetNet layer, however, regarding encryption of IP headers see
Section 9.
DetNet nodes do not have any need to inspect the payload of any
DetNet packets, making them data-agnostic. This means that end-
to- end encryption at the application layer is an acceptable way
to protect user data.
Encryption can also be applied at the subnet layer, for example
for Ethernet using MACSec, as noted in Section 9.
Related attacks
Encryption can be used to mitigate recon attacks (Section 5.2.6).
However, for a DetNet network to give differentiated quality of
service on a flow-by-flow basis, the network must be able to
identify the flows individually. This implies that in a recon
attack the attacker may also be able to track individual flows to
learn more about the system.
7.5.1. Encryption Considerations for DetNet
Any compute time which is required for encryption and decryption
processing ('crypto') must be included in the flow latency
calculations. Thus, crypto algorithms used in a DetNet must have
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bounded worst-case execution times, and these values must be used in
the latency calculations.
Some crypto algorithms are symmetric in encode/decode time (such as
AES) and others are asymmetric (such as public key algorithms).
There are advantages and disadvantages to the use of either type in a
given DetNet context. The discussion in this document relates to the
timing implications of crypto for DetNet; it is assumed that
integrity considerations are covered elsewhere in the literature.
Asymmetrical crypto is typically not used in networks on a packet-by-
packet basis due to its computational cost. For example, if only
endpoint checks or checks at a small number of intermediate points
are required, asymmetric crypto can be used to authenticate
distribution or exchange of a secret symmetric crypto key; a
successful check based on that key will provide traffic origin
verification, as long as the key is kept secret by the participants.
TLS and IKE (for IPsec) are examples of this for endpoint checks.
However, if secret symmetrical keys are used for this purpose the key
must be given to all relays, which increases the probability of a
secret key being leaked. Also, if any relay is compromised or
misbehaving it may inject traffic into the flow.
Alternatively, asymmetric crypto can provide traffic origin
verification at every intermediate node. For example, a DetNet flow
can be associated with an (asymmetric) keypair, such that the private
key is available to the source of the flow and the public key is
distributed with the flow information, allowing verification at every
node for every packet. However, this is more computationally
expensive.
In either case, origin verification also requires replay detection as
part of the security protocol to prevent an attacker from recording
and resending traffic, e.g., as a denial of service attack on flow
forwarding resources.
If crypto keys are to be regenerated over the duration of the flow
then the time required to accomplish this must be accounted for in
the latency calculations.
7.6. Control and Signaling Message Protection
Description
Control and sigaling messages can be protected using
authentication and integrity protection mechanisms.
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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
The expectation is that the network will have a way to monitor to
detect if timing guarantees are not being met, and a way to alert
the controller plane in that event. Information about the network
performance can be gathered in real-time in order to detect
anomalies and unusual behavior that may be the symptom of a
security attack. The gathered information can be based, for
example, on per-flow counters, bandwidth measurement, and
monitoring of packet arrival times. Unusual behavior or
potentially malicious nodes can be reported to a management
system, or can be used as a trigger for taking corrective actions.
The information can be tracked by DetNet end systems and transit
nodes, and exported to a management system, for example using
YANG.
If the monitoring or reporting mechanism itself is attacked or
subverted, this can result in malfunction of the network. The
design of the monitoring system needs to take this into account
based on the specifics of the monitoring or reporting system being
considered.
Related attacks
Performance analytics can be used to mitigate various attacks,
including the ones described in Section 5.2.1 (Delay Attack),
Section 5.2.3 (Resource Segmentation Attack), and Section 5.2.7
(Time Sync Attack).
For example, in the case of data plane delay attacks, one possible
mitigation is to timestamp the data at the source, and timestamp
it again at the destination, and if the resulting latency exceeds
the promised bound, discard that data and warn the operator (and/
or enter a fail-safe mode). Note that DetNet specifies packet
sequence numbering, however it does not specify use of packet
timestamps, although they may be used by the underlying transport
(for example TSN) to provide the service.
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7.8. Mitigation Summary
The following table maps the attacks of Section 5, Security Threats,
to the impacts of Section 6, Security Threat Impacts, and to the
mitigations of the current section. Each row specifies an attack,
the impact of this attack if it is successfully implemented, and
possible mitigation methods.
+----------------------+---------------------+---------------------+
| Attack | Impact | Mitigations |
+----------------------+---------------------+---------------------+
|Delay Attack |-Non-deterministic |-Path redundancy |
| | delay |-Performance |
| |-Data disruption | analytics |
| |-Increased resource | |
| | consumption | |
+----------------------+---------------------+---------------------+
|Reconnaissance |-Enabler for other |-Encryption |
| | attacks |-Dummy traffic |
| | | insertion |
+----------------------+---------------------+---------------------+
|DetNet Flow Modificat-|-Increased resource |-Path redundancy |
|ion or Spoofing | consumption |-Integrity protection|
| |-Data disruption |-DetNet Node |
| | | authentication |
+----------------------+---------------------+---------------------+
|Inter-Segment Attack |-Increased resource |-Path redundancy |
| | consumption |-Performance |
| |-Data disruption | analytics |
+----------------------+---------------------+---------------------+
|Replication: Increased|-All impacts of other|-Integrity protection|
|attack surface | attacks |-DetNet Node |
| | | authentication |
+----------------------+---------------------+---------------------+
|Replication-related |-Non-deterministic |-Integrity protection|
|Header Manipulation | delay |-DetNet Node |
| |-Data disruption | authentication |
+----------------------+---------------------+---------------------+
|Path Manipulation |-Enabler for other |-Control message |
| | attacks | protection |
+----------------------+---------------------+---------------------+
|Path Choice: Increased|-All impacts of other|-Control message |
|Attack Surface | attacks | protection |
+----------------------+---------------------+---------------------+
|Control or Signaling |-Increased resource |-Control message |
|Packet Modification | consumption | protection |
| |-Non-deterministic | |
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| | delay | |
| |-Data disruption | |
+----------------------+---------------------+---------------------+
|Control or Signaling |-Increased resource |-Control message |
|Packet Injection | consumption | protection |
| |-Non-deterministic | |
| | delay | |
| |-Data disruption | |
+----------------------+---------------------+---------------------+
|Attacks on Time Sync |-Non-deterministic |-Path redundancy |
|Mechanisms | delay |-Control message |
| |-Increased resource | protection |
| | consumption |-Performance |
| |-Data disruption | analytics |
+----------------------+---------------------+---------------------+
Figure 3: Mapping Attacks to Impact and Mitigations
8. Association of Attacks to Use Cases
Different attacks can have different impact and/or mitigation
depending on the use case, so we would like to make this association
in our analysis. However since there is a potentially unbounded list
of use cases, we categorize the attacks with respect to the common
themes of the use cases as identified in the Use Case Common Themes
section of the DetNet Use Cases [RFC8578].
See also Figure 2 for a mapping of the impact of attacks per use case
by industry.
8.1. Association of Attacks to Use Case Common Themes
In this section we review each theme and discuss the attacks that are
applicable to that theme, as well as anything specific about the
impact and mitigations for that attack with respect to that theme.
The table Figure 5, Mapping Between Themes and Attacks, then provides
a summary of the attacks that are applicable to each theme.
8.1.1. Sub-Network Layer
DetNet is expected to run over various transmission mediums, with
Ethernet being the first identified. Attacks such as Delay or
Reconnaissance might be implemented differently on a different
transmission medium, however the impact on the DetNet as a whole
would be essentially the same. We thus conclude that all attacks and
impacts that would be applicable to DetNet over Ethernet (i.e. all
those named in this document) would also be applicable to DetNet over
other transmission mediums.
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With respect to mitigations, some methods are specific to the
Ethernet medium, for example time-aware scheduling using 802.1Qbv
[IEEE802.1Qbv-2015] can protect against excessive use of bandwidth at
the ingress - for other mediums, other mitigations would have to be
implemented to provide analogous protection.
8.1.2. Central Administration
A DetNet network can be controlled by a centralized network
configuration and control system. Such a system may be in a single
central location, or it may be distributed across multiple control
entities that function together as a unified control system for the
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 Sync Mechanisms.
8.1.3. Hot Swap
A DetNet network is not expected to be "plug and play" - it is
expected that there is some centralized network configuration and
control system. However, the ability to "hot swap" components (e.g.
due to malfunction) is similar enough to "plug and play" that this
kind of behavior may be expected in DetNet networks, depending on the
implementation.
An attack surface related to Hot Swap is that the DetNet network must
at least consider input at runtime from devices that were not part of
the initial configuration of the network. Even a "perfect" (or
"hitless") replacement of a device at runtime would not necessarily
be ideal, since presumably one would want to distinguish it from the
original for OAM purposes (e.g. to report hot swap of a failed
device).
This implies that an attack such as Flow Modification, Spoofing or
Inter-segment (which could introduce packets from a "new" device
(i.e. one heretofore unknown on the network) could be used to exploit
the need to consider such packets (as opposed to rejecting them out
of hand as one would do if one did not have to consider introduction
of a new device).
Similarly if the network was designed to support runtime replacement
of a clock device, then presence (or apparent presence) and thus
consideration of packets from a new such device could affect the
network, or the time sync of the network, for example by initiating a
new Best Master Clock selection process. Thus attacks on time sync
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should be considered when designing hot swap type functionality (see
[RFC7384]).
8.1.4. Data Flow Information Models
Data Flow YANG models specific to DetNet networks are specified by
DetNet, and thus are 'new' and thus potentially present a new attack
surface.
8.1.5. L2 and L3 Integration
A DetNet network integrates Layer 2 (bridged) networks (e.g. AVB/TSN
LAN) and Layer 3 (routed) networks via the use of well-known
protocols such as IP, MPLS Pseudowire, and Ethernet.
There are no specific entries in the mapping table Figure 4, however
that does not imply that there could be no relevant attacks related
to L2-L3 integration.
8.1.6. End-to-End Delivery
Packets sent over DetNet are not to be dropped by the network due to
congestion. (Packets may however intentionally be dropped for
intended reasons, e.g. per security measures).
A data plane attack may force packets to be dropped, for example a
"long" Delay or Replication/Elimination or Flow Modification attack.
The same result might be obtained by a controller plane attack, e.g.
Path Manipulation or Signaling Packet Modification.
It may be that such attacks are limited to Internal on-path
attackers, but other possibilities should be considered.
An attack may also cause packets that should not be delivered to be
delivered, such as by forcing packets from one (e.g. replicated) path
to be preferred over another path when they should not be
(Replication attack), or by Flow Modification, or by Path Choice or
Packet Injection. A Time Sync attack could cause a system that was
expecting certain packets at certain times to accept unintended
packets based on compromised system time or time windowing in the
scheduler.
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8.1.7. Replacement for Proprietary Fieldbuses and Ethernet-based
Networks
There are many proprietary "field buses" used in today's industrial
and other industries, as well as proprietary non-interoperable
deterministic Ethernet-based networks. DetNet is intended to provide
an open-standards-based alternative to such buses/networks. In cases
where a DetNet intersects with such fieldbuses/networks or their
protocols, such as by protocol emulation or access via a gateway, new
attack surfaces can be opened.
For example an Inter-Segment or Controller plane attack such as Path
Manipulation, Path Choice or Control Packet Modification/Injection
could be used to exploit commands specific to such a protocol, or
that are interpreted differently by the different protocols or
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 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.
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8.1.9. Deterministic Flows
Reserved bandwidth data flows (deterministic flows) must provide the
allocated bandwidth, and must be isolated from each other.
A Spoofing or Inter-segment attack which adds packet traffic to a
bandwidth-reserved DetNet flow could cause that flow to occupy more
bandwidth than it was allocated, resulting in interference with other
DetNet flows.
A Flow Modification or Spoofing or Header Manipulation or Control
Packet Modification attack could cause packets from one flow to be
directed to another flow, thus breaching isolation between the flows.
8.1.10. Unused Reserved Bandwidth
If bandwidth reservations are made for a DetNet flow but the
associated bandwidth is not used at any point in time, that bandwidth
is made available on the network for best-effort traffic. However,
note that security considerations for best-effort traffic on a DetNet
network is out of scope of the present document, provided that such
an attack does not affect performance for DetNet OT traffic.
8.1.11. Interoperability
The DetNet network specifications are intended to enable an ecosystem
in which multiple vendors can create interoperable products, thus
promoting device diversity and potentially higher numbers of each
device manufactured.
Given that the DetNet specifications are unambiguously written and
that the implementations are accurate, then this should not in and of
itself cause a security concern; however, in the real world, it could
be. The network operator can mitigate this through sufficient
interoperability testing.
8.1.12. Cost Reductions
The DetNet network specifications are intended to enable an ecosystem
in which multiple vendors can create interoperable products, thus
promoting higher numbers of each device manufactured, promoting cost
reduction and cost competition among vendors.
This envisioned breadth of DetNet-enabled products is in general a
positive factor, however implementation flaws in any individual
component can present an attack surface. In addition, implementation
differences between components from different vendors can result in
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attack surfaces (resulting from their interaction) which may not
exist in any individual component.
Network operators can mitigate such concerns through sufficient
product and interoperability testing.
8.1.13. Insufficiently Secure Devices
The DetNet network specifications are intended to enable an ecosystem
in which multiple vendors can create interoperable products, thus
promoting device diversity and potentially higher numbers of each
device manufactured. However this raises the possibility that a
vendor might repurpose for DetNet applications a hardware or software
component that was originally designed for operation in an isolated
OT network, and thus may not have been designed to be sufficiently
secure, or secure at all. Deployment of such a device on a DetNet
network that is intended to be highly secure may present an attack
surface.
The DetNet network operator may need to take specific actions to
protect such devices, such as implementing a dedicated security layer
around the device.
8.1.14. DetNet Network Size
DetNet networks range in size from very small, e.g. inside a single
industrial machine, to very large, for example a Utility Grid network
spanning a whole country.
The size of the network might be related to how the attack is
introduced into the network, for example if the entire network is
local, there is a threat that power can be cut to the entire network.
If the network is large, perhaps only a part of the network is
attacked.
A Delay attack might be as relevant to a small network as to a large
network, although the amount of delay might be different.
Attacks sourced from IT traffic might be more likely in large
networks, since more people might have access to the network,
presenting a larger attack surface. Similarly Path Manipulation,
Path Choice and Time Sync attacks seem more likely relevant to large
networks.
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8.1.15. 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 network's reply.
Reconnaissance could be used to characterize flows and perhaps target
specific flows for attack via the controller plane as noted in
Section 6.7.
8.1.17. Bounded Latency
DetNet provides the expectation of guaranteed bounded latency.
Delay attacks can cause packets to miss their agreed-upon latency
boundaries.
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Time Sync attacks can corrupt the system's time reference, resulting
in missed latency deadlines (with respect to the "correct" time
reference).
8.1.18. 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.
Time Sync attacks can corrupt the system's time reference, resulting
in path delays that may be perceived to be different (with respect to
the "correct" time reference) even if they are not materially
different.
8.1.21. 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
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be required of a given system, and should define parameters for
communicating these kinds of metrics within the network.
Any attack on the system, of any type, can affect its overall
reliability and availability, thus in the mapping table Figure 4 we
have marked every attack. Since every DetNet depends to a greater or
lesser degree on reliability and availability, this essentially means
that all networks have to mitigate all attacks, which to a greater or
lesser degree defeats the purpose of associating attacks with use
cases. It also underscores the difficulty of designing "extremely
high reliability" networks.
8.1.22. Redundant Paths
DetNet based systems are expected to be implemented with essentially
arbitrarily high reliability/availability. A strategy used by DetNet
for providing such extraordinarily high levels of reliability is to
provide redundant paths that can be seamlessly switched between, all
the while maintaining the required performance of that system.
Replication-related attacks are by definition applicable here.
Controller plane attacks can also interfere with the configuration of
redundant paths.
8.1.23. Security Measures
A DetNet network must be made secure against devices failures,
attackers, misbehaving component, and so on. If the security
mechanisms protecting the DetNet are attacked or subverted, this can
result in malfunction of the network. The design of the security
system itself needs to take this into account based on the specifics
of the security system being considered. The general topic of
protection of security mechanisms is not unique to DetNet; it is
identical to the case of securing any security mechanism for any
network. The text of this document addresses these concerns to the
extent that they are relevant to DetNet.
8.2. Summary of Attack Types per Use Case Common Theme
The List of Attacks table Figure 4 lists the attacks of Section 5,
Security Threats, assigning a number to each type of attack. That
number is then used as a short form identifier for the attack in
Figure 5, Mapping Between Themes and Attacks.
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+----+----------------------------------------+
| | Attack |
+----+----------------------------------------+
| 1 |Delay Attack |
+----+----------------------------------------+
| 2 |DetNet Flow Modification or Spoofing |
+----+----------------------------------------+
| 3 |Inter-Segment Attack |
+----+----------------------------------------+
| 4 |Replication: Increased attack surface |
+----+----------------------------------------+
| 5 |Replication-related Header Manipulation |
+----+----------------------------------------+
| 6 |Path Manipulation |
+----+----------------------------------------+
| 7 |Path Choice: Increased Attack Surface |
+----+----------------------------------------+
| 8 |Control or Signaling Packet Modification|
+----+----------------------------------------+
| 9 |Control or Signaling Packet Injection |
+----+----------------------------------------+
| 10 |Reconnaissance |
+----+----------------------------------------+
| 11 |Attacks on Time Sync Mechanisms |
+--+----------------------------------------+
Figure 4: List of Attacks
The Mapping Between Themes and Attacks table Figure 5 maps the use
case themes of [RFC8578] (as also enumerated in this document) to the
attacks of Figure 4. Each row specifies a theme, and the attacks
relevant to this theme are marked with a '+'. The row items which
have no threats associated with them are included in the table for
completeness of the list of Use Case Common Themes, and do not have
DetNet-specific threats associated with them.
+----------------------------+--------------------------------+
| Theme | Attack |
| +--+--+--+--+--+--+--+--+--+--+--+
| | 1| 2| 3| 4| 5| 6| 7| 8| 9|10|11|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Network Layer - AVB/TSN Eth.| +| +| +| +| +| +| +| +| +| +| +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Central Administration | | | | | | +| +| +| +| +| +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Hot Swap | | +| +| | | | | | | | +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
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|Data Flow Information Models| | | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|L2 and L3 Integration | | | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|End-to-end Delivery | +| +| +| +| +| +| +| +| +| | +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Proprietary Deterministic | | | +| | | +| +| +| +| | |
|Ethernet Networks | | | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Replacement for Proprietary | | | +| | | +| +| +| +| | |
|Fieldbuses | | | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Deterministic vs. Best- | | | +| | | | | | | | |
|Effort Traffic | | | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Deterministic Flows | | +| +| | +| +| | +| | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Unused Reserved Bandwidth | | +| +| | | | | +| +| | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Interoperability | | | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Cost Reductions | | | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Insufficiently Secure | | | | | | | | | | | |
|Devices | | | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|DetNet Network Size | +| | | | | +| +| | | | +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Multiple Hops | +| +| | | | +| +| | | | +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Level of Service | | | | | | | | +| +| +| |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Bounded Latency | +| | | | | | | | | | +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Low Latency | +| | | | | | | +| +| +| +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Bounded Jitter | +| | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Symmetric Path Delays | +| | | | | | | | | | +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Reliability and Availability| +| +| +| +| +| +| +| +| +| +| +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Redundant Paths | | | | +| +| | | +| +| | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Security Measures | | | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
Figure 5: Mapping Between Themes and Attacks
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8.3. Security Considerations for OAM Traffic
This section considers DetNet-specific security considerations for
packet traffic that is generated and transmitted over a DetNet as
part of OAM (Operations, Administration, and Maintenance). For 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.
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,
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technology-specific encryption may be used, such as that provided by
IPSec [RFC4301] for IP flows and/or by an underlying sub-net using
MACSec [IEEE802.1AE-2018] for IP over Ethernet (Layer-2) flows.
However, if the DetNet nodes cannot decrypt IPsec traffic, IPSec may
not be a valid option; this is because the DetNet IP Data Plane
identifies flows via a 6-tuple that consists of two IP addresses, the
transport protocol ID, two transport protocol port numbers and the
DSCP in the IP header. When IPsec is used, the transport header is
encrypted and the next protocol ID is an IPsec protocol, usually ESP,
and not a transport protocol (e.g., neither TCP nor UDP, etc.)
leaving only three components of the 6-tuple, which are the two IP
addresses and the DSCP, which are in general not sufficient to
identify a DetNet flow.
Sections below discuss threats specific to IP and MPLS in more
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.
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
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isolation between flows, for example by protecting the forwarding
bandwidth and related resources so that they are available to detnet
traffic, by whatever means are appropriate for that network's data
plane, for example through the use of queueing mechanisms.
In a VPN, bandwidth is generally guaranteed over a period of time,
whereas in DetNet it is not aggregated over time. This implies that
any VPN-type protection mechanism must also maintain the DetNet
timing constraints.
9.2. MPLS
An MPLS network carrying DetNet traffic is expected to be a "well-
managed" network. Given that this is the case, it is difficult for
an attacker to pass a raw MPLS encoded packet into a network because
operators have considerable experience at excluding such packets at
the network boundaries, as well as excluding MPLS packets being
inserted through the use of a tunnel.
MPLS security is discussed extensively in [RFC5920] ("Security
Framework for MPLS and GMPLS Networks") to which the reader is
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
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synchronized flows to beat and cause a sudden phase hit to one of the
flows. This can be mitigated by the careful use of a scheduling
system in the underlying packet transport.
Further consideration of protection against dynamic attacks is work
in progress. New work on MPLS security may also be applicable, for
example [I-D.ietf-mpls-opportunistic-encrypt].
10. IANA Considerations
This memo includes no requests from IANA.
11. Security Considerations
The security considerations of DetNet networks are presented
throughout this document.
12. Privacy Considerations
Privacy in the context of DetNet is maintained by the base
technologies specific to the DetNet and user traffic. For example
TSN can use MACsec, IP can use IPsec, applications can use IP
transport protocol-provided methods e.g. TLS and DTLS. MPLS
typically uses L2/L3 VPNs combined with the previously mentioned
privacy methods.
13. Contributors
The Editor would like to recognize the contributions of the following
individuals to this draft.
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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
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
14. References
14.1. Normative References
[I-D.ietf-detnet-ip]
Varga, B., Farkas, J., Berger, L., Fedyk, D., and S.
Bryant, "DetNet Data Plane: IP", draft-ietf-detnet-ip-07
(work in progress), July 2020.
[I-D.ietf-detnet-mpls]
Varga, B., Farkas, J., Berger, L., Malis, A., Bryant, S.,
and J. Korhonen, "DetNet Data Plane: MPLS", draft-ietf-
detnet-mpls-12 (work in progress), September 2020.
[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>.
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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-data-plane-framework]
Varga, B., Farkas, J., Berger, L., Malis, A., and S.
Bryant, "DetNet Data Plane Framework", draft-ietf-detnet-
data-plane-framework-06 (work in progress), May 2020.
[I-D.ietf-detnet-flow-information-model]
Varga, B., Farkas, J., Cummings, R., Jiang, Y., and D.
Fedyk, "DetNet Flow Information Model", draft-ietf-detnet-
flow-information-model-10 (work in progress), May 2020.
[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-03 (work in
progress), June 2020.
[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>.
[IEEE802.1Qbv-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>.
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[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>.
[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>.
[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>.
[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>.
[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>.
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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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