RFC9055: Deterministic Networking (DetNet) Security Considerations
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(DetNet)
(security)
Internet Engineering Task Force (IETF) E. Grossman, Ed.
Request for Comments: 9055 DOLBY
Category: Informational T. Mizrahi
ISSN: 2070-1721 HUAWEI
A. Hacker
THOUGHT
June 2021
Deterministic Networking (DetNet) Security Considerations
Abstract
A DetNet (deterministic network) provides specific performance
guarantees to its data flows, such as extremely low data loss rates
and bounded latency (including bounded latency variation, i.e.,
"jitter"). As a result, securing a DetNet requires that in addition
to the best practice security measures taken for any mission-critical
network, additional security measures may be needed to secure the
intended operation of these novel service properties.
This document addresses DetNet-specific security considerations from
the perspectives of both the DetNet system-level designer and
component designer. System considerations include a taxonomy of
relevant threats and attacks, and associations of threats versus use
cases and service properties. Component-level considerations include
ingress filtering and packet arrival-time violation detection.
This document also addresses security considerations specific to the
IP and MPLS data plane technologies, thereby complementing the
Security Considerations sections of those documents.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are candidates for any level of Internet
Standard; see Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9055.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
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described in the Simplified BSD License.
Table of Contents
1. Introduction
2. Abbreviations and Terminology
3. Security Considerations for DetNet Component Design
3.1. Resource Allocation
3.1.1. Inviolable Flows
3.1.2. Design Trade-Off Considerations in the Use Cases
Continuum
3.1.3. Documenting the Security Properties of a Component
3.1.4. Fail-Safe Component Behavior
3.1.5. Flow Aggregation Example
3.2. Explicit Routes
3.3. Redundant Path Support
3.4. Timing (or Other) Violation Reporting
4. DetNet Security Considerations Compared with Diffserv Security
Considerations
5. Security Threats
5.1. Threat Taxonomy
5.2. Threat Analysis
5.2.1. Delay
5.2.2. DetNet Flow Modification or Spoofing
5.2.3. Resource Segmentation (Inter-segment Attack)
Vulnerability
5.2.4. Packet Replication and Elimination
5.2.4.1. Replication: Increased Attack Surface
5.2.4.2. Replication-Related Header Manipulation
5.2.5. Controller Plane
5.2.5.1. Path Choice Manipulation
5.2.5.2. Compromised Controller
5.2.6. Reconnaissance
5.2.7. Time-Synchronization Mechanisms
5.3. Threat Summary
6. Security Threat Impacts
6.1. Delay Attacks
6.1.1. Data Plane Delay Attacks
6.1.2. Controller Plane Delay Attacks
6.2. Flow Modification and Spoofing
6.2.1. Flow Modification
6.2.2. Spoofing
6.2.2.1. Data Plane Spoofing
6.2.2.2. Controller Plane Spoofing
6.3. Segmentation Attacks (Injection)
6.3.1. Data Plane Segmentation
6.3.2. Controller Plane Segmentation
6.4. Replication and Elimination
6.4.1. Increased Attack Surface
6.4.2. Header Manipulation at Elimination Routers
6.5. Control or Signaling Packet Modification
6.6. Control or Signaling Packet Injection
6.7. Reconnaissance
6.8. Attacks on Time-Synchronization Mechanisms
6.9. Attacks on Path Choice
7. Security Threat Mitigation
7.1. Path Redundancy
7.2. Integrity Protection
7.3. DetNet Node Authentication
7.4. Synthetic Traffic Insertion
7.5. Encryption
7.5.1. Encryption Considerations for DetNet
7.6. Control and Signaling Message Protection
7.7. Dynamic Performance Analytics
7.8. Mitigation Summary
8. Association of Attacks to Use Cases
8.1. Association of Attacks to Use Case Common Themes
8.1.1. Sub-network Layer
8.1.2. Central Administration
8.1.3. Hot Swap
8.1.4. Data Flow Information Models
8.1.5. L2 and L3 Integration
8.1.6. End-to-End Delivery
8.1.7. Replacement for Proprietary Fieldbuses and
Ethernet-Based Networks
8.1.8. Deterministic vs. Best-Effort Traffic
8.1.9. Deterministic Flows
8.1.10. Unused Reserved Bandwidth
8.1.11. Interoperability
8.1.12. Cost Reductions
8.1.13. Insufficiently Secure Components
8.1.14. DetNet Network Size
8.1.15. Multiple Hops
8.1.16. Level of Service
8.1.17. Bounded Latency
8.1.18. Low Latency
8.1.19. Bounded Jitter (Latency Variation)
8.1.20. Symmetrical Path Delays
8.1.21. Reliability and Availability
8.1.22. Redundant Paths
8.1.23. Security Measures
8.2. Summary of Attack Types per Use Case Common Theme
9. Security Considerations for OAM Traffic
10. DetNet Technology-Specific Threats
10.1. IP
10.2. MPLS
11. IANA Considerations
12. Security Considerations
13. Privacy Considerations
14. References
14.1. Normative References
14.2. Informative References
Contributors
Authors' Addresses
1. Introduction
A deterministic IP network ("Deterministic Networking Architecture"
[RFC8655]) can carry data flows for real-time applications with
extremely low data loss rates and bounded latency. The bounds on
latency defined by DetNet (as described in [RFC9016]) include both
worst-case latency (Maximum Latency, Section 5.9.2 of [RFC9016]) and
worst-case jitter (Maximum Latency Variation, Section 5.9.3 of
[RFC9016]). Data flows with deterministic properties are well
established for Ethernet networks (see Time-Sensitive Networking
(TSN), [IEEE802.1BA]); DetNet brings these capabilities to the IP
network.
Deterministic IP 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. An
example of such an isolated network is a network deployed within an
aircraft, which is "air gapped" from the outside world. DetNet
specifies a set of technologies that enable creation of deterministic
flows on IP-based networks of a potentially wide area (on the scale
of a corporate network), potentially merging OT traffic with best-
effort Information Technology (IT) traffic, and placing OT network
components into contact with IT network components, thereby exposing
the OT traffic and components to security threats that were not
present in an isolated OT network.
These DetNet (OT-type) technologies may not have previously been
deployed on a wide area IP-based network that also carries IT
traffic, and thus they 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 because many of
the use cases that are enabled by DetNet [RFC8578] include control of
physical devices (power grid devices, industrial controls, building
controls, etc.) that can have high operational costs for failure and
present potentially attractive targets for cyber attackers.
This situation is even more acute given that one of the goals of
DetNet is to provide a "converged network", i.e., one that includes
both IT traffic and OT traffic, thus exposing potentially sensitive
OT devices to attack in ways that were not previously common (usually
because they were under a separate control system or otherwise
isolated from the IT network, for example [ARINC664P7]). Security
considerations for OT networks are not a new area, and there are many
OT networks today that are connected to wide area networks or the
Internet; this document focuses on the issues that are specific to
the DetNet technologies and use cases.
Given the above considerations, securing a DetNet starts with a
scrupulously well-designed and well-managed engineered network
following industry best practices for security at both the data plane
and controller plane, as well as for any Operations, Administration,
and Maintenance (OAM) implementation; 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.
Starting with a "well-managed network", as noted above, enables us to
exclude some of the more powerful adversary capabilities from the
Internet Threat Model of [BCP72], such as the ability to arbitrarily
drop or delay any or all traffic. Given this reduced attacker
capability, we can present security considerations based on attacker
capabilities that are more directly relevant to a DetNet.
In this context, we view the "conventional" (i.e., non-time-
sensitive) network design and management aspects of network security
as being primarily concerned with preventing denial of service, i.e.,
they must ensure that DetNet traffic goes where it's supposed to and
that an external attacker can't inject traffic that disrupts the
delivery timing assurance of the DetNet. The time-specific aspects
of DetNet security presented here take up where those "conventional"
design and management aspects leave off.
However, note that "conventional" methods for mitigating (among all
the others) denial-of-service attacks (such as throttling) can only
be effectively used in a DetNet when their use does not compromise
the required time-sensitive or behavioral properties required for the
OT flows on the network. For example, a "retry" protocol is
typically not going to be compatible with a low-latency (worst-case
maximum latency) requirement; however, if in a specific use case and
implementation such a retry protocol is able to meet the timing
constraints, then it may well be used in that context. Similarly, if
common security protocols such as TLS/DTLS or IPsec are to be used,
it must be verified that their implementations are able to meet the
timing and behavioral requirements of the time-sensitive network as
implemented for the given use case. An example of "behavioral
properties" might be that dropping of more than a specific number of
packets in a row is not acceptable according to the service level
agreement.
The exact security requirements for any given DetNet are necessarily
specific to the use cases handled by that network. Thus, the reader
is assumed to be familiar with the specific security requirements of
their use cases, for example, those outlined in the DetNet Use Cases
[RFC8578] and the Security Considerations sections of the DetNet
documents applicable to the network technologies in use, for example,
[RFC8939] for an IP data plane and [RFC8964] for an MPLS data plane.
Readers can find a general introduction to the DetNet Architecture in
[RFC8655], the DetNet Data Plane in [RFC8938], and the Flow
Information Model in [RFC9016].
The DetNet technologies include ways to:
* Assign data plane resources for DetNet flows in some or all of the
intermediate nodes (routers) along the path of the flow
* 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)
* Distribute data from DetNet flow packets over time and/or space to
ensure delivery of the data in each packet in spite of the loss of
a path
This document includes sections considering DetNet component design
as well as system design. The latter includes a taxonomy and
analysis of threats, threat impacts and mitigations, and an
association of attacks with use cases (based on Section 11 of
[RFC8578]).
This document is based on the premise that there will be a very broad
range of DetNet applications and use cases, ranging in size and scope
from individual industrial machines to networks that span an entire
country [RFC8578]. Thus, no single set of prescriptions (such as
exactly which mitigation should be applied to which segment of a
DetNet) can be applicable to all of them, and indeed any single one
that we might prescribe would inevitably prove impractical for some
use case, perhaps one that does not even exist at the time of this
writing. Thus, we are not prescriptive here; we are stating the
desired end result, with the understanding that most DetNet use cases
will necessarily differ from each other, and there is no "one size
fits all".
2. Abbreviations and Terminology
Information Technology (IT): 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].
Operational Technology (OT): 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 that implements
DetNet-specific functionality, for example, all or part of a
router, switch, or end system.
Device: Used here to refer to a physical entity controlled by the
DetNet, for example, a motor.
Resource Segmentation: Used as a more general form for Network
Segmentation (the act or practice of splitting a computer network
into sub-networks, each being a network segment [NS-DEF]).
Controller Plane: In DetNet, the Controller Plane corresponds to the
aggregation of the Control and Management Planes (see [RFC8655],
Section 4.4.2).
3. Security Considerations for DetNet Component Design
This section provides guidance for implementers of components to be
used in a DetNet.
As noted above, DetNet provides resource allocation, explicit routes,
and redundant path support. Each of these has associated security
implications, which are discussed in this section, in the context of
component design. Detection, reporting and appropriate action in the
case of packet arrival-time violations are also discussed.
3.1. Resource Allocation
3.1.1. Inviolable Flows
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 DetNet flow can
be compromised by any type of traffic in the network. This includes
malicious traffic as well as inadvertent traffic such as might be
produced by a malfunctioning component, or due to interactions
between components that were not sufficiently tested for
interoperability. From a security standpoint, this is a critical
assumption, for example, when designing against DoS attacks. In
other words, with correctly designed components and security
mechanisms, one can prevent malicious activities from impacting other
resources.
However, achieving the goal of absolutely inviolable flows may not be
technically or economically feasible for any given use case, given
the broad range of possible use cases (e.g., [RFC8578]) and their
associated security considerations as outlined in this document. It
can be viewed as a continuum of security requirements, from isolated
ultra-low latency systems that may have little security vulnerability
(such as an industrial machine) to broadly distributed systems with
many possible attack vectors and OT security concerns (such as a
utility network). Given this continuum, the design principle
employed in this document is to specify the desired end results,
without being overly prescriptive in how the results are achieved,
reflecting the understanding that no individual implementation is
likely to be appropriate for every DetNet use case.
3.1.2. Design Trade-Off Considerations in the Use Cases Continuum
For any given DetNet use case and its associated security
requirements, it is important for the DetNet system designer to
understand the interaction and design trade-offs that inevitably need
to be reconciled between the desired end results and the DetNet
protocols, as well as the DetNet system and component design.
For any given component, as designed for any given use case (or scope
of use cases), it is the responsibility of the component designer to
ensure that the premise of inviolable flows is supported to the
extent that they deem necessary to support their target use cases.
For example, the component may include traffic shaping and policing
at the ingress to prevent corrupted, malicious, or excessive packets
from entering the network, thereby decreasing the likelihood that any
traffic will interfere with any DetNet OT flow. The component may
include integrity protection for some or all of the header fields
such as those used for flow ID, thereby decreasing the likelihood
that a packet whose flow ID has been compromised might be directed
into a different flow path. The component may verify every single
packet header at every forwarding location, or only at certain
points. In any of these cases, the component may use dynamic
performance analytics (Section 7.7) to cause action to be initiated
to address the situation in an appropriate and timely manner, either
at the data plane or controller plane, or both in concert. The
component's software and hardware may include measures to ensure the
integrity of the resource allocation/deallocation process. Other
design aspects of the component may help ensure that the adverse
effects of malicious traffic are more limited, for example, by
protecting network control interfaces or minimizing cascade failures.
The component may include features specific to a given use case, such
as configuration of the response to a given sequential packet loss
count.
Ultimately, due to cost and complexity factors, the security
properties of a component designed for low-cost systems may be (by
design) far inferior to a component with similar intended
functionality, but designed for highly secure or otherwise critical
applications, perhaps at substantially higher cost. Any given
component is designed for some set of use cases and accordingly will
have certain limitations on its security properties and
vulnerabilities. It is thus the responsibility of the system
designer to assure themselves that the components they use in their
design are capable of satisfying their overall system security
requirements.
3.1.3. Documenting the Security Properties of a Component
In order for the system designer to adequately understand the
security-related behavior of a given component, the designer of any
component intended for use with DetNet needs to clearly document the
security properties of that component. For example, to address the
case where a corrupted packet in which the flow identification
information is compromised and thus may incidentally match the flow
ID of another ("victim") DetNet flow, resulting in additional
unauthorized traffic on the victim, the documentation might state
that the component employs integrity protection on the flow
identification fields.
3.1.4. Fail-Safe Component Behavior
Even when the security properties of a component are understood and
well specified, if the component malfunctions, for example, due to
physical circumstances unpredicted by the component designer, it may
be difficult or impossible to fully prevent malfunction of the
network. The degree to which a component is hardened against various
types of failures is a distinguishing feature of the component and
its design, and the overall system design can only be as strong as
its weakest link.
However, all networks are subject to this level of uncertainty; it is
not unique to DetNet. Having said that, DetNet raises the bar by
changing many added latency scenarios from tolerable annoyances to
unacceptable service violations. That in turn underscores the
importance of system integrity, as well as correct and stable
configuration of the network and its nodes, as discussed in
Section 1.
3.1.5. Flow Aggregation Example
As another example regarding resource allocation implementation,
consider the implementation of Flow Aggregation for DetNet flows (as
discussed in [RFC8938]). In this example, say there are N flows that
are to be aggregated; thus, the bandwidth resources of the aggregate
flow must be sufficient to contain the sum of the bandwidth
reservation for the N flows. However, if one of those flows were to
consume more than its individually allocated bandwidth, this could
cause starvation of the other flows. Thus, simply providing and
enforcing the calculated aggregate bandwidth may not be a complete
solution; the bandwidth for each individual flow must still be
guaranteed, for example, via ingress policing of each flow (i.e.,
before it is aggregated). Alternatively, if by some other means each
flow to be aggregated can be trusted not to exceed its allocated
bandwidth, the same goal can be achieved.
3.2. Explicit Routes
The DetNet-specific purpose for constraining the ability of the
DetNet to reroute 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 reroute 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 that 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 reroute OT traffic in
such a way as to maintain the specified latency bounds (and any other
specified service properties) for any reason, for example, in
response to a runtime component or path failure.
So from a DetNet security standpoint, the DetNet system designer can
expect that any component designed for use in a DetNet will deliver
the packets within the agreed-upon service parameters. For the
component designer, this means that in order for a component to
achieve that expectation, any component that is involved in
controlling or implementing any change of the initially TE-configured
flow routes must prevent rerouting of OT flows (whether malicious or
accidental) that might adversely affect delivering the traffic within
the specified service parameters.
3.3. Redundant Path Support
The DetNet provision for redundant paths (i.e., PREOF, or "Packet
Replication, Elimination, and Ordering Functions"), as defined in the
DetNet Architecture [RFC8655], provides the foundation for high
reliability of a DetNet by virtually eliminating packet loss (i.e.,
to a degree that is implementation dependent) through hitless
redundant packet delivery.
| Note: At the time of this writing, PREOF is not defined for the
| 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 reordering
function may not be necessary if the packets are either not required
to be in order or if the ordering is performed in some other part of
the network.
Ideally, a redundant path for a flow could be specified from end to
end; however, given that this is not always possible (as described in
[RFC8655]), the system designer will need to consider the resulting
end-to-end reliability and security resulting from any given
arrangement of network segments along the path, each of which
provides its individual PREOF implementation and thus its individual
level of reliability and security.
At the data plane, the implementation of PREOF depends on the correct
assignment and interpretation of packet sequence numbers, as well as
the actions taken based on them, such as elimination (including
elimination of packets with spurious sequence numbers). Thus, the
integrity of these values must be maintained by the component as they
are assigned by the DetNet Data Plane Service sub-layer and
transported by the Forwarding sub-layer. This is no different than
the integrity of the values in any header used by the DetNet (or any
other) data plane and is not unique to redundant paths. The
integrity protection of header values is technology dependent; for
example, in Layer 2 networks, the integrity of the header fields can
be protected by using MACsec [IEEE802.1AE-2018]. Similarly, from the
sequence number injection perspective, it is no different from any
other protocols that use sequence numbers; for particulars of
integrity protection via IPsec Authentication Headers, useful
insights are provided by Section 3 of [RFC4302].
3.4. Timing (or Other) Violation Reporting
A task of the DetNet system designer is to create a network such that
for any incoming packet that arrives with any timing or bandwidth
violation, an appropriate action can be taken in order to prevent
damage to the system. The reporting step may be accomplished through
dynamic performance analysis (see Section 7.7) or by any other means
as implemented in one or more components. The action to be taken for
any given circumstance within any given application will depend on
the use case. The action may involve intervention from the
controller plane, or it may be taken "immediately" by an individual
component, for example, if a very fast response is required.
The definitions and selections of the actions that can be taken are
properties of the components. The component designer implements
these options according to their expected use cases, which may vary
widely from component to component. Clearly, selecting an
inappropriate response to a given condition may cause more problems
than it is intending to mitigate; for example, a naive approach might
be to have the component shut down the link if a packet arrives
outside of its prescribed time window. However, such a simplistic
action may serve the attacker better than it serves the network.
Similarly, simple logging of such issues may not be adequate since a
delay in response could result in material damage, for example, to
mechanical devices controlled by the network. Thus, a breadth of
possible and effective security-related actions and their
configuration is a positive attribute for a DetNet component.
Some possible violations that warrant detection include cases where a
packet arrives:
* Outside of its prescribed time window
* Within its time window but with a compromised timestamp that makes
it appear that it is not within its window
* Exceeding the reserved flow bandwidth
Some possible direct actions that may be taken at the data plane
include traffic policing and shaping functions (e.g., those described
in [RFC2475]), separating flows into per-flow rate-limited queues,
and potentially applying active queue management [RFC7567]. However,
if those (or any other) actions are to be taken, the system designer
must ensure that the results of such actions do not compromise the
continued safe operation of the system. For example, the network
(i.e., the controller plane and data plane working together) must
mitigate in a timely fashion any potential adverse effect on
mechanical devices controlled by the network.
4. DetNet Security Considerations Compared with Diffserv Security
Considerations
DetNet is designed to be compatible with Diffserv [RFC2474] as
applied to IT traffic in the DetNet. DetNet also incorporates the
use of the 6-bit value of the Differentiated Services Code Point
(DSCP) field of the Type of Service (IPv4) and Traffic Class (IPv6)
bytes for flow identification. However, the DetNet interpretation of
the DSCP value for OT traffic is not equivalent to the per-hop
behavior (PHB) selection behavior as defined by Diffserv.
Thus, security considerations for DetNet have some aspects in common
with Diffserv, in fact overlapping 100% with respect to IP IT
traffic. Security considerations for these aspects are part of the
existing literature on IP network security, specifically the Security
Considerations sections of [RFC2474] and [RFC2475]. However, DetNet
also introduces timing and other considerations that are not present
in Diffserv, so the Diffserv security considerations are a subset of
the DetNet security considerations.
In the case of DetNet OT traffic, the DSCP value is interpreted
differently than in Diffserv and contributes to determination of the
service provided to the packet. In DetNet, there are similar
consequences to Diffserv for lack of detection of, or incorrect
handling of, packets with mismarked DSCP values, and many of the
points made in the Diffserv Security discussions (Section 6.1 of
[RFC2475], Section 7 of [RFC2474], and Section 3.3.2.1 of [RFC6274])
are also relevant to DetNet OT traffic though perhaps in modified
form. For example, in DetNet, the effect of an undetected or
incorrectly handled maliciously mismarked DSCP field in an OT packet
is not identical to affecting the PHB of that packet, since DetNet
does not use the PHB concept for OT traffic. Nonetheless, the
service provided to the packet could be affected, so mitigation
measures analogous to those prescribed by Diffserv would be
appropriate for DetNet. For example, mismarked DSCP values should
not cause failure of network nodes. The remarks in [RFC2474]
regarding IPsec and Tunneling Interactions are also relevant (though
this is not to say that other sections are less relevant).
In this discussion, interpretation (and any possible intentional re-
marking) of the DSCP values of packets destined for DetNet OT flows
is expected to occur at the ingress to the DetNet domain; once inside
the domain, maintaining the integrity of the DSCP values is subject
to the same handling considerations as any other field in the packet.
5. Security Threats
This section presents a taxonomy of threats 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 10 considers attacks that are
associated with the DetNet technologies encompassed by [RFC8938].
We distinguish controller plane threats from data plane threats. The
attack surface may be the same, but the types of attacks, as well as
the motivation behind them, are different. For example, a Delay
attack is more relevant to the data plane than to the controller
plane. There is also a difference in terms of security solutions;
the way you secure the data plane is often different than the way you
secure the controller plane.
5.1. Threat Taxonomy
This document employs organizational elements of the threat models of
[RFC7384] and [RFC7835]. This model classifies attackers based on
two criteria:
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.
On-path vs. off-path:
On-path attackers are located in a position that allows
interception, modification, or dropping of in-flight protocol
packets, whereas off-path attackers can only attack by generating
protocol packets.
Regarding the boundary between internal vs. external attackers as
defined above, note that in this document we do not make concrete
recommendations regarding which specific segments of the network are
to be protected in any specific way, for example, via encryption or
authentication. As a result, the boundary as defined above is not
unequivocally specified here. Given that constraint, the reader can
view an internal attacker as one who can operate within the perimeter
defined by the DetNet Edge Nodes (as defined in the DetNet
Architecture [RFC8655]), allowing that the specifics of what is
encrypted or authenticated within this perimeter will vary depending
on the implementation.
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, and also which are considered to be the most common threats
(explored further in Section 5.2). 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
[DETNET-SERVICE-MODEL], is the case where a service connects DetNet
islands, i.e., two or more otherwise independent DetNets are
connected via a link that is not intrinsically part of either
network. This implies that there could be DetNet traffic flowing
over a non-DetNet link, which may provide an attacker with an
advantageous opportunity to tamper with DetNet traffic. The security
properties of non-DetNet links are outside of the scope of DetNet
Security, but it should be noted that use of non-DetNet services to
interconnect DetNets merits security analysis to ensure the integrity
of the networks involved.
5.2. Threat Analysis
5.2.1. Delay
An attacker can maliciously delay DetNet data flow traffic. By
delaying the traffic, the attacker can compromise the service of
applications that are sensitive to high delays or to high delay
variation. The delay may be constant or modulated.
5.2.2. DetNet Flow Modification or Spoofing
An attacker can modify some header fields of en route packets in a
way that causes the DetNet flow identification mechanisms to
misclassify the flow. Alternatively, the attacker can inject traffic
that is tailored to appear as if it belongs to a legitimate DetNet
flow. The potential consequence is that the DetNet flow resource
allocation cannot guarantee the performance that is expected when the
flow identification works correctly.
5.2.3. Resource Segmentation (Inter-segment Attack) Vulnerability
DetNet components are expected to split their resources between
DetNet flows in a way that prevents traffic from one DetNet flow from
affecting the performance of other DetNet flows and also prevents
non-DetNet traffic from affecting DetNet flows. However, perhaps due
to implementation constraints, some resources may be partially
shared, and an attacker may try to exploit this property. For
example, an attacker can inject traffic in order to exhaust network
resources such that DetNet packets that share resources with the
injected traffic may be dropped or delayed. Such injected traffic
may be part of DetNet flows or non-DetNet traffic.
Another example of a Resource Segmentation attack is the case in
which an attacker is able to overload the exception path queue on the
router, i.e., a "slow path" typically taken by control or OAM packets
that are diverted from the data plane because they require processing
by a CPU. DetNet OT flows are typically configured to take the "fast
path" through the data plane to minimize latency. However, if there
is only one queue from the forwarding Application-Specific Integrated
Circuit (ASIC) to the exception path, and for some reason the system
is configured such that any DetNet packets must be handled on this
exception path, then saturating the exception path could result in
the delaying or dropping of DetNet packets.
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:
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.
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.
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 eliminating bridge, the flow
has effectively been hijacked by the attacker. It is now possible
for the attacker to either replace en route packets with malicious
packets, or to simply inject errors into the packets, causing the
packets to be dropped at their destination.
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.
5.2.5.2. Compromised Controller
An attacker can subvert a legitimate controller (or subvert another
component such that it represents itself as a legitimate controller)
with the result that the network nodes incorrectly believe it is
authorized to instruct them.
The presence of a compromised node or controller in a DetNet is not a
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. The
act of compromising a controller may not even be within the
capabilities of our defined attacker types -- in other words, it may
not be achievable via packet traffic at all, whether internal or
external, on path or off path. It might be accomplished, for
example, by a human with physical access to the component, who could
upload bogus firmware to it via a USB stick. All of this underscores
the requirement for careful overall 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 or
statistical properties. The gathered information can later be used
to invoke other attacks on some or all of the flows.
DetNet flows are typically uniquely identified by their 6-tuple,
i.e., fields within the L3 or L4 header. However, in some
implementations, the flow ID may also be augmented by additional per-
flow attributes known to the system, e.g., above L4. For the purpose
of this document, we assume any such additional fields used for flow
ID are encrypted and/or integrity protected from external attackers.
Note however that existing OT protocols designed for use on dedicated
secure networks may not intrinsically provide such protection, in
which case IPsec or transport-layer security mechanisms may be
needed.
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 Table 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.
+======================+=========================================+
| Attack | Attacker Type |
| +====================+====================+
| | Internal | External |
| +=========+==========+=========+==========+
| | On-Path | Off-Path | On-Path | Off-Path |
+======================+=========+==========+=========+==========+
| Delay Attack | + | | + | |
+----------------------+---------+----------+---------+----------+
| DetNet Flow | + | + | | |
| Modification or | | | | |
| Spoofing | | | | |
+----------------------+---------+----------+---------+----------+
| Inter-segment Attack | + | + | + | + |
+----------------------+---------+----------+---------+----------+
| Replication: | + | + | + | + |
| Increased Attack | | | | |
| Surface | | | | |
+----------------------+---------+----------+---------+----------+
| Replication-Related | + | | | |
| Header Manipulation | | | | |
+----------------------+---------+----------+---------+----------+
| Path Manipulation | + | + | | |
+----------------------+---------+----------+---------+----------+
| Path Choice: | + | + | + | + |
| Increased Attack | | | | |
| Surface | | | | |
+----------------------+---------+----------+---------+----------+
| Control or Signaling | + | | | |
| Packet Modification | | | | |
+----------------------+---------+----------+---------+----------+
| Control or Signaling | + | + | | |
| Packet Injection | | | | |
+----------------------+---------+----------+---------+----------+
| Reconnaissance | + | | + | |
+----------------------+---------+----------+---------+----------+
| Attacks on Time- | + | + | + | + |
| Synchronization | | | | |
| Mechanisms | | | | |
+----------------------+---------+----------+---------+----------+
Table 1: Threat Analysis Summary
6. Security Threat Impacts
When designing security for a DetNet, as with any network, it may be
prohibitively expensive or technically infeasible to thoroughly
protect against every possible threat. Thus, the security designer
must be informed (for example, by an application domain expert such
as a product manager) regarding the relative significance of the
various threats and their impact if a successful attack is carried
out. In this section, we present an example of a possible template
for such a communication, culminating in a table (Table 2) that lists
a set of threats under consideration, and some values characterizing
their relative impact in the context of a given industry. The
specific threats, industries, and impact values in the table are
provided only as an example of this kind of assessment and its
communication; they are not intended to be taken literally.
This section considers assessment of the relative impacts of the
attacks described in Section 5. In this section, the impacts as
described assume that the associated mitigation is not present or has
failed. Mitigations are discussed in Section 7.
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 OT or time sensitive networks (though
not to the exclusion of IT or non-time-sensitive networks), the
impact of an exploit can also include failure or malfunction of
mechanical and/or other physical systems.
DetNet raises these stakes significantly for OT applications,
particularly those that may have been designed to run in an OT-only
environment and thus may not have been designed for security in an IT
environment with its associated components, services, and protocols.
The extent of impact of a successful vulnerability exploit varies
considerably by use case and by industry; additional insight
regarding the individual use cases is available from "Deterministic
Networking Use Cases" [RFC8578]. Each of those use cases is
represented in Table 2, including Pro Audio, Electrical Utilities,
Industrial M2M (split into two areas: M2M Data Gathering and M2M
Control Loop), and others.
Aspects of Impact (left column) include Criticality of Failure,
Effects of Failure, Recovery, and DetNet Functional Dependence.
Criticality of failure summarizes the seriousness of the impact. The
impact of a resulting failure can affect many different metrics that
vary greatly in scope and severity. In order to reduce the number of
variables, only the following were included: Financial, Health and
Safety, Effect on a Single Organization, and Effect 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,
and 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 that 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.
+==============+=====+======+======+==========+======+======+======+
| | PRO | Util | Bldg | Wireless | Cell | M2M | M2M |
| | A | | | | | Data | Ctrl |
+==============+=====+======+======+==========+======+======+======+
| Criticality | Med | Hi | Low | Med | Med | Med | Med |
+==============+=====+======+======+==========+======+======+======+
| Effects |
+==============+=====+======+======+==========+======+======+======+
| Financial | Med | Hi | Med | Med | Low | Med | Med |
+--------------+-----+------+------+----------+------+------+------+
| Health/ | Med | Hi | Hi | Med | Med | Med | Med |
| Safety | | | | | | | |
+--------------+-----+------+------+----------+------+------+------+
| Affects 1 | Hi | Hi | Med | Hi | Med | Med | Med |
| org | | | | | | | |
+--------------+-----+------+------+----------+------+------+------+
| Affects >1 | Med | Hi | Low | Med | Med | Med | Med |
| org | | | | | | | |
+==============+=====+======+======+==========+======+======+======+
| Recovery |
+==============+=====+======+======+==========+======+======+======+
| Recov Time | Med | Hi | Med | Hi | Hi | Hi | Hi |
| Obj | | | | | | | |
+--------------+-----+------+------+----------+------+------+------+
| Recov Point | Med | Hi | Low | Med | Low | Hi | Hi |
| Obj | | | | | | | |
+==============+=====+======+======+==========+======+======+======+
| DetNet Dependence |
+==============+=====+======+======+==========+======+======+======+
| Time | Hi | Hi | Low | Hi | Med | Low | Hi |
| Dependence | | | | | | | |
+--------------+-----+------+------+----------+------+------+------+
| Latency/ | Hi | Hi | Med | Med | Low | Low | Hi |
| Jitter | | | | | | | |
+--------------+-----+------+------+----------+------+------+------+
| Data | Hi | Hi | Med | Hi | Low | Hi | Hi |
| Integrity | | | | | | | |
+--------------+-----+------+------+----------+------+------+------+
| Src Node | Hi | Hi | Med | Hi | Med | Hi | Hi |
| Integ | | | | | | | |
+--------------+-----+------+------+----------+------+------+------+
| Availability | Hi | Hi | Med | Hi | Low | Hi | Hi |
+--------------+-----+------+------+----------+------+------+------+
Table 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, since the services attached to
the DetNet flow are likely to have strict delivery time requirements.
For a single-path scenario, disruption within the single flow is a
real possibility. In a multipath scenario, large delays or
instabilities in one DetNet flow can also lead to increased buffer
and processor resource consumption 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 2
ms for a flow, yet the machine receives it with 5 ms latency, the
control loop of the machine may become unstable.
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.
* Delayed teardown 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.
* 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.
* Delaying messages that remove 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. Thus,
the potential impact of a Modification attack includes disrupting the
application as well as the network equipment.
6.2.2. Spoofing
6.2.2.1. Data Plane Spoofing
Spoofing data plane messages can result in increased resource
consumption 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.
6.2.2.2. Controller Plane Spoofing
A successful Controller Plane Spoofing attack will potentially have
adverse effects. It can do virtually anything from:
* modifying existing DetNet flows by changing the available
bandwidth
* adding or removing endpoints from a DetNet flow
* dropping DetNet flows completely
* falsely creating new DetNet flows (exhausting the systems
resources or enabling DetNet flows that are outside the control of
the network engineer)
6.3. Segmentation Attacks (Injection)
6.3.1. Data Plane Segmentation
Injection of false messages in a DetNet flow could lead to exhaustion
of the available bandwidth for that flow if the routers attribute
these false messages to the resource budget of that flow.
In a multipath scenario, injected messages will cause increased
processor utilization in elimination routers. If enough paths are
subject to malicious injection, the legitimate messages can be
dropped. Likewise, it can cause an increase in buffer usage. In
total, it will consume more resources in the routers than normal,
giving rise to a resource-exhaustion attack on the routers.
If a DetNet flow is interrupted, the end application will be affected
by what is now a non-deterministic flow. Note that there are many
possible sources of flow interruptions, for example, but not limited
to, such physical-layer conditions as a broken wire or a radio link
that is compromised by interference.
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:
* create new DetNet flows (exhausting resources)
* drop existing DetNet flows (denial of service)
* add end stations to a multicast group (loss of privacy)
* remove end stations from a multicast group (reduction of service)
* modify the DetNet flow attributes (affecting available bandwidth)
If an attacker can inject control messages without the central
controller knowing, then one or more components in the network may
get into a state that is not expected by the controller. At that
point, if the controller initiates a command, the effect of that
command may not be as expected, since the target of the command may
have started from a different initial state.
6.4. Replication and Elimination
The Replication and Elimination functions are relevant only to data
plane messages as controller plane messages are not subject to
multipath routing.
6.4.1. Increased Attack Surface
The impact of an increased attack surface is that it increases the
probability that the network can be exposed to an attacker. This can
facilitate a wide range of specific attacks, and their respective
impacts are discussed in other subsections of this section.
6.4.2. Header Manipulation at Elimination Routers
This attack can potentially cause DoS to the application that uses
the attacked DetNet flows or to the network equipment that forwards
them. Furthermore, it can allow an attacker to manipulate the
network paths and the behavior of the network layer.
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.
An attacker can, at their leisure, observe over time various aspects
of the messaging and signaling, learning the intent and purpose of
the traffic flows. Then at some later date, possibly at an important
time in the operational context, they might launch an attack based on
that knowledge.
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 that 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.
6.8. Attacks on Time-Synchronization Mechanisms
DetNet relies on an underlying time-synchronization mechanism;
therefore, a compromised synchronization mechanism may cause DetNet
nodes to malfunction. Specifically, DetNet flows may fail to meet
their latency requirements and deterministic behavior, thus causing
DoS to DetNet applications.
6.9. Attacks on Path Choice
This is covered in part in Section 6.3 (Segmentation Attacks
(Injection)) and, as with Replication and Elimination (see
Section 6.4), this is relevant for data plane messages.
7. Security Threat Mitigation
This section describes a set of measures that can be taken to
mitigate the attacks described in Section 5. These mitigations
should be viewed as a set of tools, any of which can be used
individually or in concert. The DetNet component and/or system and/
or application designer can apply these tools as necessary based on a
system-specific threat analysis.
Some of the technology-specific security considerations and
mitigation approaches are further discussed in DetNet data plane
solution documents, such as [RFC8938], [RFC8939], [RFC8964],
[RFC9025], and [RFC9056].
7.1. Path Redundancy
Description: Path redundancy is a DetNet flow that can be forwarded
simultaneously over multiple paths. Packet Replication and
Elimination [RFC8655] provide 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 Sections 5.2.1,
5.2.2, 5.2.3, and 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
otherwise unused code paths to expose hidden flaws. Subtle race
conditions and memory allocation bugs in error-handling paths are
classic examples of this.
7.2. Integrity Protection
Description: Integrity protection in the scope of DetNet is the
ability to detect if a packet header has been modified
(maliciously or otherwise) and if so, take some appropriate action
(as discussed in Section 7.7). The decision on where in the
network to apply integrity protection is part of the DetNet system
design, and the implementation of the protection method itself is
a part of a DetNet component design.
The most common technique for detecting header modification is the
use of a Message Authentication Code (MAC) (see Section 10 for
examples). The MAC can be distributed either in line (included in
the same packet) or via a side channel. Of these, the in-line
method is generally preferred due to the low latency that may be
required on DetNet flows and the relative complexity and
computational overhead of a sideband approach.
There are different levels of security available for integrity
protection, ranging from the basic ability to detect if a header
has been corrupted in transit (no malicious attack) to stopping a
skilled and determined attacker capable of both subtly modifying
fields in the headers as well as updating an unkeyed checksum.
Common for all are the 2 steps that need to be performed in both
ends. The first is computing the checksum or MAC. The
corresponding verification step must perform the same steps before
comparing the provided with the computed value. Only then can the
receiver be reasonably sure that the header is authentic.
The most basic protection mechanism consists of computing a simple
checksum of the header fields and providing it to the next entity
in the packets path for verification. Using a MAC combined with a
secret key provides the best protection against Modification and
Replication attacks (see Sections 5.2.2 and 5.2.4). This MAC
usage needs to be part of a security association that is
established and managed by a security association protocol (such
as IKEv2 for IPsec security associations). Integrity protection
in the controller plane is discussed in Section 7.6. The secret
key, regardless of the MAC used, must be protected from falling
into the hands of unauthorized users. Once key management becomes
a topic, it is important to understand that this is a delicate
process and should not be undertaken lightly. BCP 107 [BCP107]
provides best practices in this regard.
DetNet system and/or component designers need to be aware of these
distinctions and enforce appropriate integrity-protection
mechanisms as needed based on a threat analysis. Note that adding
integrity-protection mechanisms may introduce latency; thus, many
of the same considerations in Section 7.5.1 also apply here.
Packet Sequence Number Integrity Considerations: The use of PREOF in
a DetNet implementation implies the use of a sequence number for
each packet. There is a trust relationship between the component
that adds the sequence number and the component that removes the
sequence number. The sequence number may be end-to-end source to
destination, or it may be added/deleted by network edge
components. The adder and remover(s) have the trust relationship
because they are the ones that ensure that the sequence numbers
are not modifiable. Thus, sequence numbers can be protected by
using authenticated encryption or by a MAC without using
encryption. Between the adder and remover there may or may not be
replication and elimination functions. The elimination functions
must be able to see the sequence numbers. Therefore, if
encryption is done between adders and removers, it must not
obscure the sequence number. If the sequence removers and the
eliminators are in the same physical component, it may be possible
to obscure the sequence number; however, that is a layer violation
and is not recommended practice.
| Note: At the time of this writing, PREOF is not defined for
| the IP data plane.
Related attacks: Integrity protection mitigates attacks related to
modification and tampering, including the attacks described in
Sections 5.2.2 and 5.2.4.
7.3. DetNet Node Authentication
Description: Authentication verifies the identity of DetNet nodes
(including DetNet Controller Plane nodes), and this enables
mitigation of Spoofing attacks. While integrity protection
(Section 7.2) prevents intermediate nodes from modifying
information, authentication can provide traffic origin
verification, i.e., to verify that each packet in a DetNet flow is
from a known source. Although node authentication and integrity
protection are two different goals of a security protocol, in most
cases, a common protocol (such as IPsec [RFC4301] or MACsec
[IEEE802.1AE-2018]) is used for achieving both purposes.
Related attacks: DetNet node authentication is used to mitigate
attacks related to spoofing, including the attacks of Sections
5.2.2 and 5.2.4.
7.4. Synthetic Traffic Insertion
Description: With some queuing methods such as [IEEE802.1Qch-2017],
it is possible to introduce synthetic traffic in order to
regularize the timing of packet transmission. (Synthetic traffic
typically consists of randomly generated packets injected in the
network to mask observable transmission patterns in the flows,
which may allow an attacker to gain insight into the content of
the flows). This can subsequently reduce the value of passive
monitoring from internal threats (see Section 5) as it will be
much more difficult to associate discrete events with particular
network packets.
Related attacks: Removing distinctive temporal properties of
individual packets or flows can be used to mitigate against
reconnaissance attacks (Section 5.2.6). For example, synthetic
traffic can be used to maintain constant traffic rate even when no
user data is transmitted, thus making it difficult to collect
information about the times at which users are active and the
times at which DetNet flows are added or removed.
Traffic Insertion Challenges: Once an attacker is able to monitor
the frames traversing a network to such a degree that they can
differentiate between best-effort traffic and traffic belonging to
a specific DetNet flow, it becomes difficult to not reveal to the
attacker whether a given frame is valid traffic or an inserted
frame. Thus, having the DetNet components generate and remove the
synthetic traffic may or may not be a viable option unless certain
challenges are solved; for example, but not limited to:
* Inserted traffic must be indistinguishable from valid stream
traffic from the viewpoint of the attacker.
* DetNet components must be able to safely identify and remove
all inserted traffic (and only inserted traffic).
* The controller plane must manage where to insert and remove
synthetic traffic, but this information must not be revealed to
an attacker.
An alternative design is to have the insertion and removal of
synthetic traffic be performed at the application layer rather
than by the DetNet itself. For example, the use of RTP padding
to reduce information leakage from variable-bit-rate audio
transmission via the Secure Real-time Transport Protocol (SRTP)
is discussed in [RFC6562].
7.5. Encryption
Description: Reconnaissance attacks (Section 5.2.6) can be mitigated
to some extent through the use of encryption, thereby preventing
the attacker from accessing the packet header or contents.
Specific encryption protocols will depend on the lower layers that
DetNet is forwarded over. For example, IP flows may be forwarded
over IPsec [RFC4301], and Ethernet flows may be secured using
MACsec [IEEE802.1AE-2018].
However, despite the use of encryption, a reconnaissance attack
can provide the attacker with insight into the network, even
without visibility into the packet. For example, an attacker can
observe which nodes are communicating with which other nodes,
including when, how often, and with how much data. In addition,
the timing of packets may be correlated in time with external
events such as action of an external device. Such information may
be used by the attacker, for example, in mapping out specific
targets for a different type of attack at a different time.
DetNet nodes do not have any need to inspect the payload of any
DetNet packets, making them data agnostic. This means that end-
to-end encryption at the application layer is an acceptable way to
protect user data.
Note that reconnaissance is a threat that is not specific to
DetNet flows; therefore, reconnaissance mitigation will typically
be analyzed and provided by a network operator regardless of
whether DetNet flows are deployed. Thus, encryption requirements
will typically not be defined in DetNet technology-specific
specifications, but considerations of using DetNet in encrypted
environments will be discussed in these specifications. For
example, Section 5.1.2.3 of [RFC8939] discusses flow
identification of DetNet flows running over IPsec.
Related attacks: As noted above, encryption can be used to mitigate
reconnaissance attacks (Section 5.2.6). However, for a DetNet to
provide differentiated quality of service on a flow-by-flow basis,
the network must be able to identify the flows individually. This
implies that in a reconnaissance attack, the attacker may also be
able to track individual flows to learn more about the system.
7.5.1. Encryption Considerations for DetNet
Any compute time that is required for encryption and decryption
processing ("crypto") must be included in the flow latency
calculations. Thus, cryptographic algorithms used in a DetNet must
have bounded worst-case execution times, and these values must be
used in the latency calculations. Fortunately, encryption and
decryption operations typically are designed to have constant
execution times in order to avoid side channel leakage.
Some cryptographic algorithms are symmetric in encode/decode time
(such as AES), and others are asymmetric (such as public key
algorithms). There are advantages and disadvantages to the use of
either type in a given DetNet context. The discussion in this
document relates to the timing implications of crypto for DetNet; it
is assumed that integrity considerations are covered elsewhere in the
literature.
Asymmetrical crypto is typically not used in networks on a packet-by-
packet basis due to its computational cost. For example, if only
endpoint checks or checks at a small number of intermediate points
are required, asymmetric crypto can be used to authenticate
distribution or exchange of a secret symmetric crypto key; a
successful check based on that key will provide traffic origin
verification as long as the key is kept secret by the participants.
TLS (v1.3 [RFC8446], in particular, Section 4.1 ("Key Exchange
Messages")) and IKEv2 [RFC6071] are examples of this for endpoint
checks.
However, if secret symmetric keys are used for this purpose, the key
must be given to all relays, which increases the probability of a
secret key being leaked. Also, if any relay is compromised or
faulty, then it may inject traffic into the flow. Group key
management protocols can be used to automate management of such
symmetric keys; for an example in the context of IPsec, see
[IPSECME-G-IKEV2].
Alternatively, asymmetric crypto can provide traffic origin
verification at every intermediate node. For example, a DetNet flow
can be associated with an (asymmetric) keypair, such that the private
key is available to the source of the flow and the public key is
distributed with the flow information, allowing verification at every
node for every packet. However, this is more computationally
expensive.
In either case, origin verification also requires replay detection as
part of the security protocol to prevent an attacker from recording
and resending traffic, e.g., as a denial-of-service attack on flow
forwarding resources.
In the general case, cryptographic hygiene requires the generation of
new keys during the lifetime of an encrypted flow (e.g., see
Section 9 of [RFC4253]), and any such key generation (or key
exchange) requires additional computing time, which must be accounted
for in the latency calculations for that flow. For modern ECDH
(Elliptical Curve Diffie-Hellman) key-exchange operations (such as
x25519 [RFC7748]), these operations can be performed in constant
(predictable) time; however, this is not universally true (for
example, for legacy RSA key exchange [RFC4432]). Thus, implementers
should be aware of the time properties of these algorithms and avoid
algorithms that make constant-time implementation difficult or
impossible.
7.6. Control and Signaling Message Protection
Description: Control and signaling messages can be protected through
the use of any or all of encryption, authentication, and
integrity-protection mechanisms. Compared with data flows, the
timing constraints for controller and signaling messages may be
less strict, and the number of such packets may be fewer. If that
is the case in a given application, then it may enable the use of
asymmetric cryptography for the signing of both payload and
headers for such messages, as well as encrypting the payload.
Given that a DetNet is managed by a central controller, the use of
a shared public key approach for these processes is well proven.
This is further discussed in Section 7.5.1.
Related attacks: These mechanisms can be used to mitigate various
attacks on the controller plane, as described in Sections 5.2.5,
5.2.7, and 5.2.5.1.
7.7. Dynamic Performance Analytics
Description: Incorporating Dynamic Performance Analytics (DPA)
implies that the DetNet design includes a performance monitoring
system to validate that timing guarantees are being met and to
detect timing violations or other anomalies that may be the
symptom of a security attack or system malfunction. If this
monitoring system detects unexpected behavior, it must then cause
action to be initiated to address the situation in an appropriate
and timely manner, either at the data plane or controller plane or
both in concert.
The overall DPA system can thus be decomposed into the "detection"
and "notification" functions. Although the time-specific DPA
performance indicators and their implementation will likely be
specific to a given DetNet, and as such are nascent technology at
the time of this writing, DPA is commonly used in existing
networks so we can make some observations on how such a system
might be implemented for a DetNet given that it would need to be
adapted to address the time-specific performance indicators.
Detection Mechanisms: Measurement of timing performance can be done
via "passive" or "active" monitoring, as discussed below.
Examples of passive monitoring strategies include:
* Monitoring of queue and buffer levels, e.g., via active queue
management (e.g., [RFC7567]).
* Monitoring of per-flow counters.
* Measurement of link statistics such as traffic volume,
bandwidth, and QoS.
* Detection of dropped packets.
* Use of commercially available Network Monitoring tools.
Examples of active monitoring include:
* In-band timing measurements (such as packet arrival times),
e.g., by timestamping and packet inspection.
* Use of OAM. For DetNet-specific OAM considerations, see
[DETNET-IP-OAM] and [DETNET-MPLS-OAM]. Note: At the time of
this writing, specifics of DPA have not been developed for the
DetNet OAM but could be a subject for future investigation.
- For OAM for Ethernet specifically, see also Connectivity
Fault Management (CFM [IEEE802.1Q]), which defines protocols
and practices for OAM for paths through 802.1 bridges and
LANs.
* Out-of-band detection. Following the data path or parts of a
data path, for example, Bidirectional Forwarding Detection
(BFD, e.g., [RFC5880]).
Note that for some measurements (e.g., packet delay), it may be
necessary to make and reconcile measurements from more than one
physical location (e.g., a source and destination), possibly in
both directions, in order to arrive at a given performance
indicator value.
Notification Mechanisms: Making DPA measurement results available at
the right place(s) and time(s) to effect timely response can be
challenging. Two notification mechanisms that are in general use
are NETCONF/YANG Notifications and the proprietary local telemetry
interfaces provided with components from some vendors. The
Constrained Application Protocol (CoAP) Observe Option [RFC7641]
could also be relevant to such scenarios.
At the time of this writing, YANG Notifications are not addressed
by the DetNet YANG documents; however, this may be a topic for
future work. It is possible that some of the passive mechanisms
could be covered by notifications from non-DetNet-specific YANG
modules; for example, if there is OAM or other performance
monitoring that can monitor delay bounds, then that could have its
own associated YANG data model, which could be relevant to DetNet,
for example, some "threshold" values for timing measurement
notifications.
At the time of this writing, there is an IETF Working Group for
network/performance monitoring (IP Performance Metrics (IPPM)).
See also previous work by the completed Remote Network Monitoring
Working Group (RMONMIB). See also "An Overview of the IETF
Network Management Standards", [RFC6632].
Vendor-specific local telemetry may be available on some
commercially available systems, whereby the system can be
programmed (via a proprietary dedicated port and API) to monitor
and report on specific conditions, based on both passive and
active measurements.
Related attacks: Performance analytics can be used to detect various
attacks, including the ones described in Section 5.2.1 (Delay
attack), Section 5.2.3 (Resource Segmentation attack), and
Section 5.2.7 (Time-Synchronization attack). Once detection and
notification have occurred, the appropriate action can be taken to
mitigate the threat.
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 does not
meet the service agreement, take appropriate action. Note that
DetNet specifies packet sequence numbering; however, it does not
specify use of packet timestamps, although they may be used by the
underlying transport (for example, TSN [IEEE802.1BA]) to provide
the service.
7.8. Mitigation Summary
The following table maps the attacks of Section 5 (Security Threats)
to the impacts of Section 6 (Security Threat Impacts) and to the
mitigations of the current section. Each row specifies an attack,
the impact of this attack if it is successfully implemented, and
possible mitigation methods.
+======================+======================+=====================+
| Attack | Impact | Mitigations |
+======================+======================+=====================+
| Delay Attack | * Non-deterministic | * Path redundancy |
| | delay | |
| | | * Performance |
| | * Data disruption | analytics |
| | | |
| | * Increased | |
| | resource | |
| | consumption | |
+----------------------+----------------------+---------------------+
| Reconnaissance | * Enabler for other | * Encryption |
| | attacks | |
| | | * Synthetic |
| | | traffic |
| | | insertion |
+----------------------+----------------------+---------------------+
| DetNet Flow | * Increased | * Path redundancy |
| Modification or | resource | |
| Spoofing | consumption | * Integrity |
| | | protection |
| | * Data disruption | |
| | | * DetNet Node |
| | | authentication |
+----------------------+----------------------+---------------------+
| Inter-segment Attack | * Increased | * Path redundancy |
| | resource | |
| | consumption | * Performance |
| | | analytics |
| | * Data disruption | |
+----------------------+----------------------+---------------------+
| Replication: | * All impacts of | * Integrity |
| Increased Attack | other attacks | protection |
| Resource | | |
| | | * DetNet Node |
| | | authentication |
| | | |
| | | * Encryption |
+----------------------+----------------------+---------------------+
| Replication-Related | * Non-deterministic | * Integrity |
| Header Manipulation | delay | protection |
| | | |
| | * Data disruption | * DetNet Node |
| | | authentication |
+----------------------+----------------------+---------------------+
| Path Manipulation | * Enabler for other | * Control and |
| | attacks | signaling |
| | | message |
| | | protection |
+----------------------+----------------------+---------------------+
| Path Choice: | * All impacts of | * Control and |
| Increased Attack | other attacks | signaling |
| Surface | | message |
| | | protection |
+----------------------+----------------------+---------------------+
| Control or Signaling | * Increased | * Control and |
| Packet Modification | resource | signaling |
| | consumption | message |
| | | protection |
| | * Non-deterministic | |
| | delay | |
| | | |
| | * Data disruption | |
+----------------------+----------------------+---------------------+
| Control or Signaling | * Increased | * Control and |
| Packet Injection | resource | signaling |
| | consumption | message |
| | | protection |
| | * Non-deterministic | |
| | delay | |
| | | |
| | * Data disruption | |
+----------------------+----------------------+---------------------+
| Attacks on Time- | * Non-deterministic | * Path redundancy |
| Synchronization | delay | |
| Mechanisms | | * Control and |
| | * Increased | signaling |
| | resource | message |
| | consumption | protection |
| | | |
| | * Data disruption | * Performance |
| | | analytics |
+----------------------+----------------------+---------------------+
Table 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 Section 11 of
[RFC8578].
See also Table 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.
Table 5, Mapping between Themes and Attacks, then provides a summary
of the attacks that are applicable to each theme.
8.1.1. Sub-network Layer
DetNet is expected to run over various transmission mediums, with
Ethernet being the first identified. Attacks such as Delay or
Reconnaissance might be implemented differently on a different
transmission medium; however, the impact on the DetNet as a whole
would be essentially the same. We thus conclude that all attacks and
impacts that would be applicable to DetNet over Ethernet (i.e., all
those named in this document) would also be applicable to DetNet over
other transmission mediums.
With respect to mitigations, some methods are specific to the
Ethernet medium, for example, time-aware scheduling using 802.1Qbv
[IEEE802.1Qbv-2015] can protect against excessive use of bandwidth at
the ingress -- for other mediums, other mitigations would have to be
implemented to provide analogous protection.
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 that 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, Reconnaissance, and Attacks on Time-Synchronization
Mechanisms.
8.1.3. Hot Swap
A DetNet network is not expected to be "plug and play"; it is
expected that there is some centralized network configuration and
control system. However, the ability to "hot swap" components (e.g.,
due to malfunction) is similar enough to "plug and play" that this
kind of behavior may be expected in DetNet networks, depending on the
implementation.
An attack surface related to hot swap is that the DetNet network must
at least consider input at runtime from components that were not part
of the initial configuration of the network. Even a "perfect" (or
"hitless") replacement of a component at runtime would not
necessarily be ideal, since presumably one would want to distinguish
it from the original for OAM purposes (e.g., to report hot swap of a
failed component).
This implies that an attack such as Flow Modification, Spoofing, or
Inter-segment (which could introduce packets from a "new" component,
i.e., one heretofore unknown on the network) could be used to exploit
the need to consider such packets (as opposed to rejecting them out
of hand as one would do if one did not have to consider introduction
of a new component).
To mitigate this situation, deployments should provide a method for
dynamic and secure registration of new components, and (possibly
manual) deregistration and re-keying of retired components. This
would avoid the situation in which the network must accommodate
potentially insecure packet flows from unknown components.
Similarly, if the network was designed to support runtime replacement
of a clock component, then presence (or apparent presence) and thus
consideration of packets from a new such component could affect the
network, or the time synchronization of the network, for example, by
initiating a new Best Master Clock selection process. These types of
attacks should therefore be considered when designing hot-swap-type
functionality (see [RFC7384]).
8.1.4. Data Flow Information Models
DetNet specifies new YANG data models [DETNET-YANG] that may present
new attack surfaces. Per IETF guidelines, security considerations
for any YANG data model are expected to be part of the YANG data
model specification, as described in [IETF-YANG-SEC].
8.1.5. L2 and L3 Integration
A DetNet network integrates Layer 2 (bridged) networks (e.g., AVB/TSN
LAN) and Layer 3 (routed) networks (e.g., IP) via the use of well-
known protocols such as IP, MPLS Pseudowire, and Ethernet. Various
DetNet documents address many specific aspects of Layer 2 and Layer 3
integration within a DetNet, and these are not individually
referenced here; security considerations for those aspects are
covered within those documents or within the related subsections of
the present document.
Please note that although there are no entries in the L2 and L3
Integration line of the Mapping between Themes and Attacks table
(Table 5), this does not imply that there could be no relevant
attacks related to L2-L3 integration.
8.1.6. End-to-End Delivery
Packets that are part of a resource-reserved DetNet flow are not to
be dropped by the DetNet due to congestion. Packets may however be
dropped for intended reasons, for example, security measures. For
example, consider the case in which a packet becomes corrupted
(whether incidentally or maliciously) such that the resulting flow ID
incidentally matches the flow ID of another DetNet flow, potentially
resulting in additional unauthorized traffic on the latter. In such
a case, it may be a security requirement that the system report and/
or take some defined action, perhaps when a packet drop count
threshold has been reached (see also Section 7.7).
A data plane attack may force packets to be dropped, for example, as
a result of a Delay attack, Replication/Elimination attack, or Flow
Modification attack.
The same result might be obtained by a Controller plane attack, e.g.,
Path Manipulation or Signaling Packet Modification.
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 Path Choice or
Packet Injection. A Time-Synchronization 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.
8.1.7. Replacement for Proprietary Fieldbuses and Ethernet-Based
Networks
There are many proprietary "fieldbuses" used in Industrial and other
industries, as well as proprietary non-interoperable deterministic
Ethernet-based networks. DetNet is intended to provide an open-
standards-based alternative to such buses/networks. In cases where a
DetNet intersects with such fieldbuses/networks or their protocols,
such as by protocol emulation or access via a gateway, new attack
surfaces can be opened.
For example, an Inter-segment or Controller plane attack such as Path
Manipulation, Path Choice, or Control Packet Modification/Injection
could be used to exploit commands specific to such a protocol or that
are interpreted differently by the different protocols or gateway.
8.1.8. Deterministic vs. Best-Effort Traffic
Most of the themes described in this document address OT (reserved)
DetNet flows -- this item is intended to address issues related to IT
traffic on a DetNet.
DetNet is intended to support coexistence of time-sensitive
operational (OT, deterministic) traffic and informational (IT, "best
effort") traffic on the same ("unified") network.
With DetNet, this coexistence 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 the 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.
The handling of IT traffic (i.e., traffic that by definition is not
guaranteed any given deterministic service properties) by the DetNet
will by definition not be given the DetNet-specific protections
provided to DetNet (resource-reserved) flows. The implication is
that the IT traffic on the DetNet network will necessarily have its
own specific set of product (component or system) requirements for
protection against attacks such as DoS; presumably they will be less
stringent than those for OT flows, but nonetheless, component and
system designers must employ whatever mitigations will meet the
specified security requirements for IT traffic for the given
component or DetNet.
The network design as a whole also needs to consider possible
application-level dependencies of OT-type applications on services
provided by the IT part of the network; for example, does the OT
application depend on IT network services such as DNS or OAM? If
such dependencies exist, how are malicious packet flows handled?
Such considerations are typically outside the scope of DetNet proper,
but nonetheless need to be addressed in the overall DetNet network
design for a given use case.
8.1.9. Deterministic Flows
Reserved bandwidth data flows (deterministic flows) must provide the
allocated bandwidth and must be isolated from each other.
A Spoofing or Inter-segment attack that 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, Spoofing, 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 any
such attacks on best-effort traffic do not affect performance for
DetNet OT traffic.
8.1.11. Interoperability
The DetNet specifications as a whole are intended to enable an
ecosystem in which multiple vendors can create interoperable
products, thus promoting component diversity and potentially higher
numbers of each component manufactured. Toward that end, the
security measures and protocols discussed in this document are
intended to encourage interoperability.
Given that the DetNet specifications are unambiguously written and
that the implementations are accurate, the property of
interoperability should not in and of itself cause security concerns;
however, flaws in interoperability between components could result in
security weaknesses. The network operator, as well as system and
component designers, can all contribute to reducing such weaknesses
through interoperability testing.
8.1.12. Cost Reductions
The DetNet network specifications are intended to enable an ecosystem
in which multiple vendors can create interoperable products, thus
promoting higher numbers of each component manufactured, promoting
cost reduction and cost competition among vendors.
This envisioned breadth of DetNet-enabled products is in general a
positive factor; however, implementation flaws in any individual
component can present an attack surface. In addition, implementation
differences between components from different vendors can result in
attack surfaces (resulting from their interaction) that may not exist
in any individual component.
Network operators can mitigate such concerns through sufficient
product and interoperability testing.
8.1.13. Insufficiently Secure Components
The DetNet network specifications are intended to enable an ecosystem
in which multiple vendors can create interoperable products, thus
promoting component diversity and potentially higher numbers of each
component manufactured. However, this raises the possibility that a
vendor might repurpose for DetNet applications a hardware or software
component that was originally designed for operation in an isolated
OT network and thus may not have been designed to be sufficiently
secure, or secure at all, against the sorts of attacks described in
this document. Deployment of such a component on a DetNet network
that is intended to be highly secure may present an attack surface;
thus, the DetNet network operator may need to take specific actions
to protect such components, for example, by implementing a secure
interface (such as a firewall) to isolate the component from the
threats that may be present in the greater network.
8.1.14. DetNet Network Size
DetNet networks range in size from very small, e.g., inside a single
industrial machine, to very large, e.g., 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-Synchronization attacks seem more likely
relevant to large networks.
8.1.15. Multiple Hops
Large DetNet networks (e.g., a Utility Grid network) may involve many
"hops" over various kinds of links, for example, radio repeaters,
microwave links, fiber optic links, etc.
An attacker who has knowledge of the operation of a component or
device's internal software (such as "device drivers") may be able to
take advantage of this knowledge to design an attack that could
exploit flaws (or even the specifics of normal operation) in the
communication between the various links.
It is also possible that a large-scale DetNet topology containing
various kinds of links may not be in as common use as other more
homogeneous topologies. This situation may present more opportunity
for attackers to exploit software and/or protocol flaws in or between
these components because these components or configurations may not
have been sufficiently tested for interoperability (in the way they
would be as a result of broad usage). This may be of particular
concern to early adopters of new DetNet components or technologies.
Of the attacks we have defined, the ones identified in Section 8.1.14
as germane to large networks are the most relevant.
8.1.16. Level of Service
A DetNet is expected to provide means to configure the network that
include querying network path latency, requesting bounded latency for
a given DetNet flow, requesting worst-case maximum and/or minimum
latency for a given path or DetNet flow, and so on. It is an
expected case that the network cannot provide a given requested
service level. In such cases, the network control system should
reply that the requested service level is not available (as opposed
to accepting the parameter but then not delivering the desired
behavior).
Controller plane attacks such as Signaling Packet Modification and
Injection could be used to modify or create control traffic that
could interfere with the process of a user requesting a level of
service and/or the reply from the network.
Reconnaissance could be used to characterize flows and perhaps target
specific flows for attack via the controller plane as noted in
Section 6.7.
8.1.17. Bounded Latency
DetNet provides the expectation of guaranteed bounded latency.
Delay attacks can cause packets to miss their agreed-upon latency
boundaries.
Time-Synchronization attacks can corrupt the time reference of the
system, resulting in missed latency deadlines (with respect to the
"correct" time reference).
8.1.18. Low Latency
Applications may require "extremely low latency"; however, depending
on the application, these may mean very different latency values.
For example, "low latency" across a Utility Grid network is on a
different time scale than "low latency" in a motor control loop in a
small machine. The intent is that the mechanisms for specifying
desired latency include wide ranges, and that architecturally there
is nothing to prevent arbitrarily low latencies from being
implemented in a given network.
Attacks on the controller plane (as described in the Level of Service
theme; see Section 8.1.16) and Delay and Time attacks (as described
in the Bounded Latency theme; see 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-Synchronization attacks can corrupt the time reference of the
system, resulting in path delays that may be perceived to be
different (with respect to the "correct" time reference) even if they
are not materially different.
8.1.21. Reliability and Availability
DetNet-based systems are expected to be implemented with essentially
arbitrarily high availability (for example, 99.9999% up time, or even
12 nines). The intent is that the DetNet designs should not make any
assumptions about the level of reliability and availability that may
be required of a given system and should define parameters for
communicating these kinds of metrics within the network.
Any attack on the system, of any type, can affect its overall
reliability and availability; thus, in the mapping table (Table 5),
we have marked every attack. Since every DetNet depends to a greater
or lesser degree on reliability and availability, this essentially
means that all networks have to mitigate all attacks, which to a
greater or lesser degree defeats the purpose of associating attacks
with use cases. It also underscores the difficulty of designing
"extremely high reliability" networks.
In practice, network designers can adopt a risk-based approach in
which only those attacks are mitigated whose potential cost is higher
than the cost of mitigation.
8.1.22. Redundant Paths
This document expects that each DetNet system will be implemented to
some essentially arbitrary level of reliability and/or availability,
depending on the use case. A strategy used by DetNet for providing
extraordinarily high levels of reliability when justified is to
provide redundant paths between which traffic can be seamlessly
switched, 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
If any of the security mechanisms that protect the DetNet are
attacked or subverted, this can result in malfunction of the network.
Thus, the security systems themselves need to be robust against
attacks.
The general topic of protection of security mechanisms is not unique
to DetNet; it is identical to the case of securing any security
mechanism for any network. This document addresses these concerns
only to the extent that they are unique to DetNet.
8.2. Summary of Attack Types per Use Case Common Theme
The List of Attacks table (Table 4) lists the attacks described in
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 Table 5, Mapping between Themes and Attacks.
+====+============================================+
| | Attack |
+====+============================================+
| 1 | Delay Attack |
+----+--------------------------------------------+
| 2 | DetNet Flow Modification or Spoofing |
+----+--------------------------------------------+
| 3 | Inter-segment Attack |
+----+--------------------------------------------+
| 4 | Replication: Increased Attack Surface |
+----+--------------------------------------------+
| 5 | Replication-Related Header Manipulation |
+----+--------------------------------------------+
| 6 | Path Manipulation |
+----+--------------------------------------------+
| 7 | Path Choice: Increased Attack Surface |
+----+--------------------------------------------+
| 8 | Control or Signaling Packet Modification |
+----+--------------------------------------------+
| 9 | Control or Signaling Packet Injection |
+----+--------------------------------------------+
| 10 | Reconnaissance |
+----+--------------------------------------------+
| 11 | Attacks on Time-Synchronization Mechanisms |
+----+--------------------------------------------+
Table 4: List of Attacks
The Mapping between Themes and Attacks table (Table 5) maps the use
case themes of [RFC8578] (as also enumerated in this document) to the
attacks of Table 4. Each row specifies a theme, and the attacks
relevant to this theme are marked with a "+". The row items that
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 | | + | + | | | | | | | | + |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| Data Flow | | | | | | | | | | | |
| Information Models | | | | | | | | | | | |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| L2 and L3 | | | | | | | | | | | |
| Integration | | | | | | | | | | | |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| End-to-End | + | + | + | + | + | + | + | + | | + | |
| Delivery | | | | | | | | | | | |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| Proprietary | | | + | | | + | + | + | + | | |
| Deterministic | | | | | | | | | | | |
| Ethernet Networks | | | | | | | | | | | |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| Replacement for | | | + | | | | | | | | |
| Proprietary | | | | | | | | | | | |
| Fieldbuses | | | | | | | | | | | |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| Deterministic vs. | + | + | + | | + | + | | + | | | |
| Best-Effort | | | | | | | | | | | |
| Traffic | | | | | | | | | | | |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| Deterministic | + | + | + | | + | + | | + | | | |
| Flows | | | | | | | | | | | |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| Unused Reserved | | + | + | | | | | + | + | | |
| Bandwidth | | | | | | | | | | | |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| Interoperability | | | | | | | | | | | |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| Cost Reductions | | | | | | | | | | | |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| Insufficiently | | | | | | | | | | | |
| Secure Components | | | | | | | | | | | |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| DetNet Network | + | | | | | + | + | | | | + |
| Size | | | | | | | | | | | |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| Multiple Hops | + | + | | | | + | + | | | | + |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| Level of Service | | | | | | | | + | + | + | |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| Bounded Latency | + | | | | | | | | | | + |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| Low Latency | + | | | | | | | + | + | | + |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| Bounded Jitter | + | | | | | | | | | | |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| Symmetric Path | + | | | | | | | | | | + |
| Delays | | | | | | | | | | | |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| Reliability and | + | + | + | + | + | + | + | + | + | + | + |
| Availability | | | | | | | | | | | |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| Redundant Paths | | | | + | + | | | + | + | | |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
| Security Measures | | | | | | | | | | | |
+--------------------+---+---+---+---+---+---+---+---+---+----+----+
Table 5: Mapping between Themes and Attacks
9. 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:
* 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.
* 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.
10. DetNet Technology-Specific Threats
Section 5, Security Threats, describes threats that 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 [RFC8939] and
delivers service over sub-layer technologies such as MPLS [RFC8964]
and IEEE 802.1 Time-Sensitive Networking (TSN) [RFC9023].
Application flows can be protected through whatever means are
provided by the layer and sub-layer technologies. For example,
technology-specific encryption may be used for IP flows (IPsec
[RFC4301]). For IP-over-Ethernet (Layer 2) flows using an underlying
sub-net, MACsec [IEEE802.1AE-2018] may be appropriate. For some use
cases, packet integrity protection without encryption may be
sufficient.
However, if the DetNet nodes cannot decrypt IPsec traffic, then
DetNet flow identification for encrypted IP traffic flows must be
performed in a different way than it would be for unencrypted IP
DetNet flows. The DetNet IP data plane identifies unencrypted flows
via a 6-tuple that consists of two IP addresses, the transport
protocol ID, two transport protocol port numbers, and the DSCP in the
IP header. When IPsec is used, the transport header is encrypted and
the next protocol ID is an IPsec protocol, usually Encapsulating
Security Payload (ESP), and not a transport protocol, leaving only
three components of the 6-tuple, which are the two IP addresses and
the DSCP. If the IPsec sessions are established by a controller,
then this controller could also transmit (in the clear) the Security
Parameter Index (SPI) and thus the SPI could be used (in addition to
the pair of IP addresses) for flow identification. Identification of
DetNet flows over IPsec is further discussed in Section 5.1.2.3 of
[RFC8939].
Sections below discuss threats specific to IP and MPLS in more
detail.
10.1. IP
IP 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).
Thus, the security considerations for a DetNet based on an IP data
plane are purely inherited from the rich IP security literature and
code/application base, and the data-plane-independent section of this
document.
Maintaining security for IP segments of a DetNet may be more
challenging than for the MPLS segments of the network given that the
IP segments of the network may reach the edges of the network, which
are more likely to involve interaction with potentially malevolent
outside actors. Conversely, MPLS is inherently more secure than IP
since it is internal to routers and it is well known how to protect
it from outside influence.
Another way to look at DetNet IP security is to consider it in the
light of VPN security. As an industry, we have a lot of experience
with VPNs running through networks with other VPNs -- it is well
known how to secure the network for that. However, for a DetNet, we
have the additional subtlety that any possible interaction of one
packet with another can have a potentially deleterious effect on the
time properties of the flows. So the network must provide sufficient
isolation between flows, for example, by protecting the forwarding
bandwidth and related resources so that they are available to DetNet
traffic, by whatever means are appropriate for the data plane of that
network, for example, through the use of queuing 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.
10.2. 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 builds on MPLS and
pseudowire encapsulation. Thus, for guidance on securing the DetNet
elements of DetNet over MPLS, the reader is also referred to the
security considerations of [RFC4385], [RFC5586], [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
(TWTT) protocols, which are NTP [RFC5905] and the Precision Time
Protocol [IEEE1588]. The security requirements for these are
described in [RFC7384].
One particular problem that has been observed in operational tests of
TWTT protocols is the ability for two closely but not completely
synchronized flows to beat and cause a sudden phase hit to one of the
flows. This can be mitigated by the careful use of a scheduling
system in the underlying packet transport.
Some investigations into protection of MPLS systems against dynamic
attacks exist, such as [MPLS-OPP-ENCRYPT]; perhaps deployment of
DetNets will encourage additional such investigations.
11. IANA Considerations
This document has no IANA actions.
12. Security Considerations
The security considerations of DetNet networks are presented
throughout this document.
13. 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, and 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.
However, note that reconnaissance threats such as traffic analysis
and monitoring of electrical side channels can still cause there to
be privacy considerations even when traffic is encrypted.
14. References
14.1. Normative References
[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>.
[RFC8938] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., and S.
Bryant, "Deterministic Networking (DetNet) Data Plane
Framework", RFC 8938, DOI 10.17487/RFC8938, November 2020,
<https://www.rfc-editor.org/info/rfc8938>.
[RFC8939] Varga, B., Ed., Farkas, J., Berger, L., Fedyk, D., and S.
Bryant, "Deterministic Networking (DetNet) Data Plane:
IP", RFC 8939, DOI 10.17487/RFC8939, November 2020,
<https://www.rfc-editor.org/info/rfc8939>.
[RFC8964] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., Bryant,
S., and J. Korhonen, "Deterministic Networking (DetNet)
Data Plane: MPLS", RFC 8964, DOI 10.17487/RFC8964, January
2021, <https://www.rfc-editor.org/info/rfc8964>.
14.2. Informative References
[ARINC664P7]
ARINC, "Aircraft Data Network Part 7 Avionics Full-Duplex
Switched Ethernet Network", ARINC 664 P7, September 2009.
[BCP107] Bellovin, S. and R. Housley, "Guidelines for Cryptographic
Key Management", BCP 107, RFC 4107, June 2005.
<https://www.rfc-editor.org/info/bcp107>
[BCP72] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552, July
2003.
<https://www.rfc-editor.org/info/bcp72>
[DETNET-IP-OAM]
Mirsky, G., Chen, M., and D. Black, "Operations,
Administration and Maintenance (OAM) for Deterministic
Networks (DetNet) with IP Data Plane", Work in Progress,
Internet-Draft, draft-ietf-detnet-ip-oam-02, 30 March
2021, <https://datatracker.ietf.org/doc/html/draft-ietf-
detnet-ip-oam-02>.
[DETNET-MPLS-OAM]
Mirsky, G. and M. Chen, "Operations, Administration and
Maintenance (OAM) for Deterministic Networks (DetNet) with
MPLS Data Plane", Work in Progress, Internet-Draft, draft-
ietf-detnet-mpls-oam-03, 30 March 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-detnet-
mpls-oam-03>.
[DETNET-SERVICE-MODEL]
Varga, B., Ed. and J. Farkas, "DetNet Service Model", Work
in Progress, Internet-Draft, draft-varga-detnet-service-
model-02, May 2017,
<https://datatracker.ietf.org/doc/html/draft-varga-detnet-
service-model-02>.
[DETNET-YANG]
Geng, X., Chen, M., Ryoo, Y., Fedyk, D., Rahman, R., and
Z. Li, "Deterministic Networking (DetNet) YANG Model",
Work in Progress, Internet-Draft, draft-ietf-detnet-yang-
12, 19 May 2021, <https://datatracker.ietf.org/doc/html/
draft-ietf-detnet-yang-12>.
[IEEE1588] IEEE, "IEEE 1588 Standard for a Precision Clock
Synchronization Protocol for Networked Measurement and
Control Systems", IEEE Std. 1588-2008,
DOI 10.1109/IEEESTD.2008.4579760, July 2008,
<https://doi.org/10.1109/IEEESTD.2008.4579760>.
[IEEE802.1AE-2018]
IEEE, "IEEE Standard for Local and metropolitan area
networks-Media Access Control (MAC) Security", IEEE Std.
802.1AE-2018, DOI 10.1109/IEEESTD.2018.8585421, December
2018, <https://ieeexplore.ieee.org/document/8585421>.
[IEEE802.1BA]
IEEE, "IEEE Standard for Local and metropolitan area
networks--Audio Video Bridging (AVB) Systems", IEEE Std.
802.1BA-2011, DOI 10.1109/IEEESTD.2011.6032690, September
2011, <https://ieeexplore.ieee.org/document/6032690>.
[IEEE802.1Q]
IEEE, "IEEE Standard for Local and metropolitan area
networks--Bridges and Bridged Networks", IEEE Std. 802.1Q-
2014, DOI 10.1109/IEEESTD.2014.6991462, December 2014,
<https://ieeexplore.ieee.org/document/6991462>.
[IEEE802.1Qbv-2015]
IEEE, "IEEE Standard for Local and metropolitan area
networks -- Bridges and Bridged Networks - Amendment 25:
Enhancements for Scheduled Traffic", IEEE Std. 802.1Qbv-
2015, DOI 10.1109/IEEESTD.2016.8613095, March 2016,
<https://ieeexplore.ieee.org/document/8613095>.
[IEEE802.1Qch-2017]
IEEE, "IEEE Standard for Local and metropolitan area
networks--Bridges and Bridged Networks--Amendment 29:
Cyclic Queuing and Forwarding", IEEE Std. 802.1Qch-2017,
DOI 10.1109/IEEESTD.2017.7961303, June 2017,
<https://ieeexplore.ieee.org/document/7961303>.
[IETF-YANG-SEC]
IETF, "YANG module security considerations", October 2018,
<https://trac.ietf.org/trac/ops/wiki/yang-security-
guidelines>.
[IPSECME-G-IKEV2]
Smyslov, V. and B. Weis, "Group Key Management using
IKEv2", Work in Progress, Internet-Draft, draft-ietf-
ipsecme-g-ikev2-02, 11 January 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-ipsecme-
g-ikev2-02>.
[IT-DEF] Wikipedia, "Information technology", March 2020,
<https://en.wikiquote.org/w/
index.php?title=Information_technology&oldid=2749907>.
[MPLS-OPP-ENCRYPT]
Farrel, A. and S. Farrell, "Opportunistic Security in MPLS
Networks", Work in Progress, Internet-Draft, draft-ietf-
mpls-opportunistic-encrypt-03, 28 March 2017,
<https://datatracker.ietf.org/doc/html/draft-ietf-mpls-
opportunistic-encrypt-03>.
[NS-DEF] Wikipedia, "Network segmentation", December 2020,
<https://en.wikipedia.org/w/
index.php?title=Network_segmentation&oldid=993163264>.
[OT-DEF] Wikipedia, "Operational technology", March 2021,
<https://en.wikipedia.org/w/
index.php?title=Operational_technology&oldid=1011704361>.
[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>.
[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>.
[RFC4253] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
Transport Layer Protocol", RFC 4253, DOI 10.17487/RFC4253,
January 2006, <https://www.rfc-editor.org/info/rfc4253>.
[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>.
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302,
DOI 10.17487/RFC4302, December 2005,
<https://www.rfc-editor.org/info/rfc4302>.
[RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385,
February 2006, <https://www.rfc-editor.org/info/rfc4385>.
[RFC4432] Harris, B., "RSA Key Exchange for the Secure Shell (SSH)
Transport Layer Protocol", RFC 4432, DOI 10.17487/RFC4432,
March 2006, <https://www.rfc-editor.org/info/rfc4432>.
[RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
"MPLS Generic Associated Channel", RFC 5586,
DOI 10.17487/RFC5586, June 2009,
<https://www.rfc-editor.org/info/rfc5586>.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<https://www.rfc-editor.org/info/rfc5880>.
[RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
"Network Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
<https://www.rfc-editor.org/info/rfc5905>.
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
<https://www.rfc-editor.org/info/rfc5920>.
[RFC5921] Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau,
L., and L. Berger, "A Framework for MPLS in Transport
Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010,
<https://www.rfc-editor.org/info/rfc5921>.
[RFC6071] Frankel, S. and S. Krishnan, "IP Security (IPsec) and
Internet Key Exchange (IKE) Document Roadmap", RFC 6071,
DOI 10.17487/RFC6071, February 2011,
<https://www.rfc-editor.org/info/rfc6071>.
[RFC6073] Martini, L., Metz, C., Nadeau, T., Bocci, M., and M.
Aissaoui, "Segmented Pseudowire", RFC 6073,
DOI 10.17487/RFC6073, January 2011,
<https://www.rfc-editor.org/info/rfc6073>.
[RFC6274] Gont, F., "Security Assessment of the Internet Protocol
Version 4", RFC 6274, DOI 10.17487/RFC6274, July 2011,
<https://www.rfc-editor.org/info/rfc6274>.
[RFC6478] Martini, L., Swallow, G., Heron, G., and M. Bocci,
"Pseudowire Status for Static Pseudowires", RFC 6478,
DOI 10.17487/RFC6478, May 2012,
<https://www.rfc-editor.org/info/rfc6478>.
[RFC6562] Perkins, C. and JM. Valin, "Guidelines for the Use of
Variable Bit Rate Audio with Secure RTP", RFC 6562,
DOI 10.17487/RFC6562, March 2012,
<https://www.rfc-editor.org/info/rfc6562>.
[RFC6632] Ersue, M., Ed. and B. Claise, "An Overview of the IETF
Network Management Standards", RFC 6632,
DOI 10.17487/RFC6632, June 2012,
<https://www.rfc-editor.org/info/rfc6632>.
[RFC6941] Fang, L., Ed., Niven-Jenkins, B., Ed., Mansfield, S., Ed.,
and R. Graveman, Ed., "MPLS Transport Profile (MPLS-TP)
Security Framework", RFC 6941, DOI 10.17487/RFC6941, April
2013, <https://www.rfc-editor.org/info/rfc6941>.
[RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in
Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384,
October 2014, <https://www.rfc-editor.org/info/rfc7384>.
[RFC7567] Baker, F., Ed. and G. Fairhurst, Ed., "IETF
Recommendations Regarding Active Queue Management",
BCP 197, RFC 7567, DOI 10.17487/RFC7567, July 2015,
<https://www.rfc-editor.org/info/rfc7567>.
[RFC7641] Hartke, K., "Observing Resources in the Constrained
Application Protocol (CoAP)", RFC 7641,
DOI 10.17487/RFC7641, September 2015,
<https://www.rfc-editor.org/info/rfc7641>.
[RFC7748] Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves
for Security", RFC 7748, DOI 10.17487/RFC7748, January
2016, <https://www.rfc-editor.org/info/rfc7748>.
[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>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[RFC8578] Grossman, E., Ed., "Deterministic Networking Use Cases",
RFC 8578, DOI 10.17487/RFC8578, May 2019,
<https://www.rfc-editor.org/info/rfc8578>.
[RFC9016] Varga, B., Farkas, J., Cummings, R., Jiang, Y., and D.
Fedyk, "Flow and Service Information Model for
Deterministic Networking (DetNet)", RFC 9016,
DOI 10.17487/RFC9016, March 2021,
<https://www.rfc-editor.org/info/rfc9016>.
[RFC9023] Varga, B., Ed., Farkas, J., Malis, A., and S. Bryant,
"Deterministic Networking (DetNet) Data Plane: IP over
IEEE 802.1 Time-Sensitive Networking (TSN)", RFC 9023,
DOI 10.17487/RFC9023, June 2021,
<https://www.rfc-editor.org/info/rfc9023>.
[RFC9025] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., and S.
Bryant, "Deterministic Networking (DetNet) Data Plane:
MPLS over UDP/IP", RFC 9025, DOI 10.17487/RFC9025, April
2021, <https://www.rfc-editor.org/info/rfc9025>.
[RFC9056] Varga, B., Ed., Berger, L., Fedyk, D., Bryant, S., and J.
Korhonen, "Deterministic Networking (DetNet) Data Plane:
IP over MPLS", RFC 9056, DOI 10.17487/RFC9056, June 2021,
<https://www.rfc-editor.org/info/rfc9056>.
Contributors
The Editor would like to recognize the contributions of the following
individuals to this document.
Stewart Bryant
Futurewei Technologies
Email: sb@stewartbryant.com
David Black
Dell EMC
176 South Street
Hopkinton, Massachusetts 01748
United States of America
Henrik Austad
SINTEF Digital
Klaebuveien 153
7037 Trondheim
Norway
Email: henrik@austad.us
John Dowdell
Airbus Defence and Space
Celtic Springs
Newport, NP10 8FZ
United Kingdom
Email: john.dowdell.ietf@gmail.com
Norman Finn
3101 Rio Way
Spring Valley, California 91977
United States of America
Email: nfinn@nfinnconsulting.com
Subir Das
Applied Communication Sciences
150 Mount Airy Road
Basking Ridge, New Jersey 07920
United States of America
Email: sdas@appcomsci.com
Carsten Bormann
Universitat Bremen TZI
Postfach 330440 D-28359 Bremen
Germany
Email: cabo@tzi.org
Authors' Addresses
Ethan Grossman (editor)
Dolby Laboratories, Inc.
1275 Market Street
San Francisco, CA 94103
United States of America
Email: ethan@ieee.org
URI: https://www.dolby.com
Tal Mizrahi
Huawei
Email: tal.mizrahi.phd@gmail.com
Andrew J. Hacker
Thought LLC
Harrisburg, PA
United States of America
Email: andrew@thought.live