Deterministic Networking (DetNet) Security Considerations

Security is of particularly high importance in DetNet networks because many of the use cases which are enabled by DetNet include control of physical devices (power grid components, industrial controls, building controls) which can have high operational costs for failure, and present potentially attractive targets for cyber-attackers. This situation is even more acute given that one of the goals of DetNet is to provide a "converged network", i.e. one that includes both IT traffic and OT traffic, thus exposing potentially sensitive OT devices to attack in ways that were not previously common (usually because they were under a separate control system or otherwise isolated from the IT network). Security considerations for OT networks is not a new area, and there are many OT networks today that are connected to wide area networks or the Internet; this draft focuses on the issues that are specific to the DetNet technologies and use cases. The DetNet technologies include ways to: Reserve data plane resources for DetNet flows in some or all of the intermediate nodes (e.g. bridges or routers) along the path of the flow Provide explicit routes for DetNet flows that do not rapidly change with the network topology Distribute data from DetNet flow packets over time and/or space to ensure delivery of each packet's data' in spite of the loss of a path This draft includes sections on threat modeling and analysis, threat impact and mitigation, and the association of various attacks with various use cases both by industry and based on the Use Case Common Themes section of the DetNet Use Cases draft . This draft also provides context for the DetNet security considerations by collecting into one place the various remarks about security from the various DetNet drafts (Use Cases, Architecture, etc). This text is duplicated here primarily because the DetNet working group has elected not to produce a Requirements draft and thus collectively these statements are as close as we have to "DetNet Security Requirements".

IT Information technology (the application of computers to store, study, retrieve, transmit, and manipulate data or information, often in the context of a business or other enterprise - Wikipedia). OT Operational Technology (the hardware and software dedicated to detecting or causing changes in physical processes through direct monitoring and/or control of physical devices such as valves, pumps, etc. - Wikipedia) MITM Man in the Middle SN Sequence Number STRIDE Addresses risk and severity associated with threat categories: Spoofing identity, Tampering with data, Repudiation, Information disclosure, Denial of service, Elevation of privilege. DREAD Compares and prioritizes risk represented by these threat categories: Damage potential, Reproducibility, Exploitability, how many Affected users, Discoverability. PTP Precision Time Protocol

This section presents a threat model, and analyzes the possible threats in a DetNet-enabled network. We distinguish control plane threats from data plane threats. The attack surface may be the same, but the types of attacks are different. For example, a delay attack is more relevant to data plane than to control plane. There is also a difference in terms of security solutions: the way you secure the data plane is often different than the way you secure the control plane.

The threat model used in this memo is based on the threat model of Section 3.1 of . 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. Man in the Middle (MITM) vs. packet injector: MITM attackers are located in a position that allows interception and modification of in-flight protocol packets, whereas a traffic injector can only attack by generating protocol packets. DetNet-Service, one of the service scenarios described in , is the case where a service connects DetNet networking islands, i.e. two or more otherwise independent DetNet network domains are connected via a link that is not intrinsically part of either network. This implies that there could be DetNet traffic flowing over a non-DetNet link, which may provide an attacker with an advantageous opportunity to tamper with DetNet traffic. The security properties of non-DetNet links are outside of the scope of DetNet Security, but it should be noted that use of non-DetNet services to interconnect DetNet networks merits security analysis to ensure the integrity of the DetNet networks involved.

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.

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. Note that in some cases there may be an explicit DetNet header, but in some cases the flow identification may be based on fields from the L3/L4 headers. If L3/L4 headers are involved, for purposes of this draft we assume they are encrypted and/or integrity-protected from external attackers.

An attacker can inject traffic, consuming network device resources, thereby affecting DetNet flows. This can be performed using non-DetNet traffic that affects DetNet traffic, or by using DetNet traffic from one DetNet flow that affects traffic from different DetNet flows.

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.

An attacker can manipulate the replication-related header fields (R-TAG). 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. Once the flow is hijacked the attacker can either replace en route packets with malicious packets, or simply injecting errors, causing the packets to be dropped at their destination.

An attacker can maliciously change, add, or remove a path, thereby affecting the corresponding DetNet flows that use the path.

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.

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

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

A passive eavesdropper can gather information about en route DetNet flows, e.g., the number of DetNet flows, their bandwidths, and their schedules. The gathered information can later be used to invoke other attacks on some or all of the flows.

An attacker can use any of the attacks described in to attack the synchronization protocol, thus affecting the DetNet service.

A summary of the attacks that were discussed in this section is presented in . 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.

This section describes the impact of the attacks described in . Mitigations are discussed further in . In computer security, the impact (or consequence) of an incident can be measured in loss of confidentiality, integrity or availability of information. In other words, this section describes the effect of a successful attack. The scope is limited to the effect of a successful attack on DetNet itself, not the applications that _use_ Detnet as this is highly application specific.

Dropped messages can result in stream instability. If only a single path is used, the entire stream can be disrupted. In a multipath scenario, large delays on one stream can lead to increased buffer and CPU resources on the elimination bridge. If the attack is carried out on a sole link (i.e. no multipath), the DetNet stream can be interrupted and result in outages.

In and of itself, this is not directly a threat, the effects of delaying control messages can have quite adverse effects later. Delayed messages for tear-down can lead to resource leakage if a stream is not torn down at the correct time. This can in turn result in failure to allocate new streams giving rise to a denial of service attack. In the case where an End-point should be added to a multicast, failure to deliver said signalling message will prevent the new EP from receiving expected frames. Likewise, when an EP should be removed from a multicast group, delaying such messages can lead to loss of privacy as the EP will continue to receive messages even after it is removed.

Of all the attacks, this is one of the most difficult to detect and counter. Often, an attacker will start out by observing the traffic going through the network and use the knowledge gathered in this phase to mount future attacks. The attacker can, at their leisure, observe over time all aspects of the messaging and signalling, learning the intent and purpose of all traffic flows. At some later date, possibly at an important time in an operational context, the attacker can launch a multi-faceted attack, possibly in conjunction with some demand for ransom. The flow-id in the header of the data plane-messages gives an attacker a very reliable identifier for DetNet traffic, and this traffic has a high probability of going to lucrative targets.

Spoofing dataplane messages can result in increased resource consumptions on the bridges throughout the network as it will increase buffer usage and CPU utilization. This can lead to resource exhaustion and/or increased delay. If the attacker manages to create valid headers, the false messages can be forwarded through the network, using part of the allocated bandwidth. This in turn can cause legitimate messages to be dropped when the budget has been exhausted. Finally, the endpoint will have to deal with invalid messages being delivered to the endpoint instead of (or in addition to) a valid message.

A successful control plane spoofing-attack has a very large potential. It can do anything from modifying existing streams by changing the available bandwidth, add or remove endpoints or drop the stream altogether. It would also be possible to falsely create new streams, which could give an attacker the ability to exhaust the systems resources, or just enable a high quality DetNet stream outside the Network engineer's control.

Injection of false messages in a DetNet stream could lead to exhaustion of the available bandwidth for a stream if the bridges accounts false messages to the stream's budget. In a multipath scenario, injected messages will cause an increased CPU utilization on elimination bridges and if enough paths are subject to malicious injection, the legitimate messages could be dropped. Likewise it can cause an increase in buffer usage. In total, this will consume more resources on the bridges than normal, giving rise to a potential resource exhaustion attack on the bridges. If a stream is interrupted, the end application will be affected by what is now a non-deterministic stream.

A successful Control Plane segmentation attack will cause control messages to be interpreted by nodes in the network. This has the potential to create new streams (exhausting resources), drop existing (denial of service), add/remove end-stations to a multicast group (loss of privacy) or modify the stream attributes (reducing available bandwidth, or increasing it so that new streams cannot reserve a path). In short, this means that you cannot trust the stream reservation properties or the network itself. As with spoofing, if an attacker is able to inject control-plane messages and the receiving end does not detect it, the receiving station must be able to.

The Replication and Elimination is relevant only to Data Plane messages as Signalling is not subject to multipath routing.

Covered briefly in

This is covered in part in , and as with Replication and Elimination (, this is relevant for DataPlane messages.

This section rates the severity of various components of the impact of a successful vulnerability exploit to use cases by industry as described in , including Pro Audio, Electrical Utilities, Building Automation, Wireless for Industrial, Cellular Radio, and Industrial M2M (split into two areas, M2M Data Gathering and M2M Control Loop). Components of Impact (left column) include Criticality of Failure, Effects of Failure, Recovery, and DetNet Functional Dependence. Criticality of failure summarizes the seriousness of the impact. The impact of a resulting failure can affect many different metrics that vary greatly in scope and severity. In order to reduce the number of variables, the following were included: Financial, Health and Safety, People well being, Affect on a single organization, and affect on multiple organizations. Recovery outlines how long it would take for an affected use case to get back to its pre-failure state (Recovery time objective, RTO), and how much of the original service would be lost in between the time of service failure and recovery to original state (Recovery Point Objective, RPO). DetNET dependence maps how much the following DetNet service objectives contribute to impact of failure: Time dependency, data integrity, source node integrity, availability, latency/jitter. The scale of the Impact mappings is low, medium, and high. In some use cases there may be a multitude of specific applications in which DetNET is used. For simplicity this section attempts to average the varied impacts of different applications. This section does not address the overall risk of a certain impact which would require the likelihood of a failure happening. In practice any such ratings will vary from case to case; the ratings shown here are given as examples.

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

This section describes a set of measures that can be taken to mitigate the attacks described in . These mitigations should be viewed as a toolset that includes several different and diverse tools. Each application or system will typically use a subset of these tools, based on a system-specific threat analysis.

Description A DetNet flow that can be forwarded simultaneously over multiple paths. Path replication and elimination provides resiliency to dropped or delayed packets. This redundancy improves the robustness to failures and to man-in-the-middle attacks. Related attacks Path redundancy can be used to mitigate various man-in-the-middle attacks, including attacks described in , , , and .

Description An integrity protection mechanism, such as a Hash-based Message Authentication Code (HMAC) can be used to mitigate modification attacks. Integrity protection can be used on the data plane header, to prevent its modification and tampering. Integrity protection in the control plane is discussed in . Related attacks Integrity protection mitigates attacks related to modification and tampering, including the attacks described in and .

Description Source authentication verifies the authenticity of DetNet sources, allowing to mitigate spoofing attacks. Note that while integrity protection () prevents intermediate nodes from modifying information, authentication verfies the source of the information. Related attacks DetNet node authentication is used to mitigate attacks related to spoofing, including the attacks of , and .

Description DetNet flows can be forwarded in encrypted form. Related attacks While confidentiality is not considered an important goal with respect to DetNet, encryption can be used to mitigate recon attacks ().

Description Control and sigaling messages can be protected using authentication and integrity protection mechanisms. Related attacks These mechanisms can be used to mitigate various attacks on the control plane, as described in , and .

Description Information about the network performance can be gathered in real-time in order to detect anomalies and unusual behavior that may be the symptom of a security attack. The gathered information can be based, for example, on per-flow counters, bandwidth measurement, and monitoring of packet arrival times. Unusual behavior or potentially malicious nodes can be reported to a management system, or can be used as a trigger for taking corrective actions. The information can be tracked by DetNet end systems and transit nodes, and exported to a management system, for example using NETCONF. Related attacks Performance analytics can be used to mitigate various attacks, including the ones described in , , and .

The following table maps the attacks of to the impacts of , 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.

Different attacks can have different impact and/or mitigation depending on the use case, so we would like to make this association in our analysis. However since there is a potentially unbounded list of use cases, we categorize the attacks with respect to the common themes of the use cases as identified in the Use Case Common Themes section of the DetNet Use Cases draft . We describe each theme and its associated attacks, impacts and mitigations.

Presumably it will be possible to run DetNet over other underlying network layers besides Ethernet, but Ethernet is explicitly supported. Is the attack specific to the Ethernet AVB/TSN protocols? Does the threat affect only Ethernet, or any underlying network layer?

A DetNet network is expected to 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. Is the attack directed at threat the central control system of the network? Does it interfere with OAM?

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. Does the attack target "hot swap" ("plug and play") operation in the network?

Data Flow Information Models specific to DetNet networks are to be specified by DetNet. Thus they are "new" and thus potentially present a new attack surface. Does the threat take advantage of any aspect of our new Data Flow Info Models?

A DetNet network is intended to integrate between Layer 2 (bridged) network(s) (e.g. AVB/TSN LAN) and Layer 3 (routed) network(s) (e.g. using IP-based protocols). Does the attack target L2? L3? Both? The interaction between the two?

Packets sent over DetNet are guaranteed not to be dropped by the network due to congestion. (Packets may however be dropped for intended reasons, e.g. per security measures). Does the attack result in packets (which should be delivered) not being delivered? Does it result in packets that should not be delivered being delivered?

There are many proprietary non-interoperable deterministic Ethernet-based networks currently available; DetNet is intended to provide an open-standards-based alternative to such networks. Does the threat relate to a specific such network that is being "emulated" or "replaced" by DetNet, for example by exploiting specific commands specific to that network protocol?

There are many proprietary "field buses" used in today's industrial and other industries; DetNet is intended to provide an open-standards-based alternative to such buses. Does the threat relate to a specific fieldbus that is being "emulated" or "replaced" by DetNet, for example by exploiting specific commands specific to that network protocol?

DetNet is intended to support coexistence of time-sensitive operational (OT, deterministic) traffic and information (IT, "best effort") traffic on the same ("unified") network. Does the attack affect only IT or only OT or both types of traffic? Does the threat affect any interaction between IT and OT traffic, e.g. by changing relative priority or handling of IT vs. OT packets?

Reserved bandwidth data flows (deterministic flows) must be isolated from each other and from best-effort traffic, so that even if the network is saturated with best-effort and/or reserved bandwidth traffic the configured flows are not adversely affected. Does the attack affect the isolation of one (reserved) flow from another?

If bandwidth reservations are made for a stream but the associated bandwidth is not used at any point in time, that bandwidth is made available on the network for best-effort traffic. If the owner of the reserved stream then starts transmitting again, the bandwidth is no longer available for best-effort traffic, on a moment-to-moment basis. (Such "temporarily available" bandwidth is not available for time-sensitive traffic, which must have its own reservation). Does the attack affect the system's ability to allocate unused reserved BW to best-effort traffic?

The DetNet network specifications are intended to enable an ecosystem in which multiple vendors can create interoperable products, thus promoting device diversity and potentially higher numbers of each device manufactured. Does the threat take advantage of differences in implementation of "interoperable" products made by different vendors?

The DetNet network specifications are intended to enable an ecosystem in which multiple vendors can create interoperable products, thus promoting higher numbers of each device manufactured, promoting cost reduction and cost competition among vendors. Does the threat take advantage of "low cost" HW or SW components or other "cost-related shortcuts" that might be present in devices?

The DetNet network specifications are intended to enable an ecosystem in which multiple vendors can create interoperable products, thus promoting device diversity and potentially higher numbers of each device manufactured. Does the threat attack "naivete" of SW, for example SW that was not designed to be sufficiently secure (or secure at all) but is deployed on a DetNet network that is intended to be highly secure? (For example IoT exploits like the Mirai video-camera botnet ().

DetNet networks range in size from very small, e.g. inside a single industrial machine, to very large, for example a Utility Grid network spanning a whole country, and involving many "hops" over various kinds of links for example radio repeaters, microwave links, fiber optic links, etc.. Does the attack affect DetNet networks of only certain sizes, e.g. very large networks, or very small? This 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. Does the threat take advantage of attack vectors that are specific to network size?

DetNet networks range in size from very small, e.g. inside a single industrial machine, to very large, for example a Utility Grid network spanning a whole country, and involving many "hops" over various kinds of links for example radio repeaters, microwave links, fiber optic links, etc.. Does the attack exploit the presence of more than one "hop"? Does the threat exploit the presence of more than one type of "hop", e.g. between radio and microwave links? Does the threat exploit a specific type of "hop", e.g. something specific to a fiber optic link, or other type of link?

A DetNet is expected to provide means to configure the network that include querying network path latency, requesting bounded latency for a given stream, requesting worst case maximum and/or minimum latency for a given path or stream, and so on. It is an expected case that the network cannot provide a given requested service level. In such cases the network control system should reply that the requested service level is not available (as opposed to accepting the parameter but then not delivering the desired behavior). Does the attack affect any querying or replying to such service-level-related traffic? Can the attack cause incorrect responses from the system regarding timing-related configuration? For example replying that a requested level of service is available when it isn't, or that the requested level of service is not available when it actually is available?

Does the threat affect the network's ability to deliver packets within the agreed-upon latency boundaries?

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. Does the threat affect the network's ability to deliver packets within the agreed-upon low latency?

Some applications would like to specify that the transit delay time values be equal for both the transmit and return paths. Does the attack affect the network's ability to provide matched transmit and return path delays (latencies)?

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. Does the attack affect the reliability of the DetNet network? Is it a large or small change, e.g. the difference between completely taking down the network for some period of time, vs reducing its reliability by just one "nine"? Does the threat affect the availability of the DetNet network?

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

A DetNet network must be made secure against devices failures, attackers, misbehaving devices, and so on. Does the threat affect such security measures themselves, e.g. by attacking SW designed to protect against device failure?

The following table lists the attacks of , assigning a number to each type of attack. That number is then used as a short form identifier for the attack in .

The following table maps the use case themes presented in this memo to the attacks of . Each row specifies a theme, and the attacks relevant to this theme are marked with a '+'.

This section collects the various statements in the currently existing DetNet Working Group drafts. For each draft, the section name and number of the quoted section is shown. The text shown here is the work of the original draft authors, quoted verbatim from the drafts. The intention is to explicitly quote all relevant text, not to summarize it.

One key to building robust real-time systems is to reduce the infinite variety of possible failures to a number that can be analyzed with reasonable confidence. DetNet aids in the process by providing filters and policers to detect DetNet packets received on the wrong interface, or at the wrong time, or in too great a volume, and to then take actions such as discarding the offending packet, shutting down the offending DetNet flow, or shutting down the offending interface. It is also essential that filters and service remarking be employed at the network edge to prevent non-DetNet packets from being mistaken for DetNet packets, and thus impinging on the resources allocated to DetNet packets. There exist techniques, at present and/or in various stages of standardization, that can perform these fault mitigation tasks that deliver a high probability that misbehaving systems will have zero impact on well-behaved DetNet flows, except of course, for the receiving interface(s) immediately downstream of the misbehaving device. Examples of such techniques include traffic policing functions (e.g. [RFC2475]) and separating flows into per-flow rate- limited queues.

Security in the context of Deterministic Networking has an added dimension; the time of delivery of a packet can be just as important as the contents of the packet, itself. A man-in-the-middle attack, for example, can impose, and then systematically adjust, additional delays into a link, and thus disrupt or subvert a real-time application without having to crack any encryption methods employed. See for an exploration of this issue in a related context. Furthermore, in a control system where millions of dollars of equipment, or even human lives, can be lost if the DetNet QoS is not delivered, one must consider not only simple equipment failures, where the box or wire instantly becomes perfectly silent, but bizarre errors such as can be caused by software failures. Because there is essential no limit to the kinds of failures that can occur, protecting against realistic equipment failures is indistinguishable, in most cases, from protecting against malicious behavior, whether accidental or intentional. Security must cover: Protection of the signaling protocol Authentication and authorization of the controlling nodes Identification and shaping of the flows

This document does not add any new security considerations beyond what the referenced technologies already have.

Security in the context of Deterministic Networking has an added dimension; the time of delivery of a packet can be just as important as the contents of the packet, itself. A man-in-the-middle attack, for example, can impose, and then systematically adjust, additional delays into a link, and thus disrupt or subvert a real-time application without having to crack any encryption methods employed. See [RFC7384] for an exploration of this issue in a related context. Typical control networks today rely on complete physical isolation to prevent rogue access to network resources. DetNet enables the virtualization of those networks over a converged IT/OT infrastructure. Doing so, DetNet introduces an additional risk that flows interact and interfere with one another as they share physical resources such as Ethernet trunks and radio spectrum. The requirement is that there is no possible data leak from and into a deterministic flow, and in a more general fashion there is no possible influence whatsoever from the outside on a deterministic flow. The expectation is that physical resources are effectively associated with a given flow at a given point of time. In that model, Time Sharing of physical resources becomes transparent to the individual flows which have no clue whether the resources are used by other flows at other times. Security must cover: Protection of the signaling protocol Authentication and authorization of the controlling nodes Identification and shaping of the flows Isolation of flows from leakage and other influences from any activity sharing physical resources

Grid monitoring and control devices are already targets for cyber attacks, and legacy telecommunications protocols have many intrinsic network-related vulnerabilities. For example, DNP3, Modbus, PROFIBUS/PROFINET, and other protocols are designed around a common paradigm of request and respond. Each protocol is designed for a master device such as an HMI (Human Machine Interface) system to send commands to subordinate slave devices to retrieve data (reading inputs) or control (writing to outputs). Because many of these protocols lack authentication, encryption, or other basic security measures, they are prone to network-based attacks, allowing a malicious actor or attacker to utilize the request-and-respond system as a mechanism for command-and-control like functionality. Specific security concerns common to most industrial control, including utility telecommunication protocols include the following: Network or transport errors (e.g. malformed packets or excessive latency) can cause protocol failure. Protocol commands may be available that are capable of forcing slave devices into inoperable states, including powering-off devices, forcing them into a listen-only state, disabling alarming. Protocol commands may be available that are capable of restarting communications and otherwise interrupting processes. Protocol commands may be available that are capable of clearing, erasing, or resetting diagnostic information such as counters and diagnostic registers. Protocol commands may be available that are capable of requesting sensitive information about the controllers, their configurations, or other need-to-know information. Most protocols are application layer protocols transported over TCP; therefore it is easy to transport commands over non-standard ports or inject commands into authorized traffic flows. Protocol commands may be available that are capable of broadcasting messages to many devices at once (i.e. a potential DoS). Protocol commands may be available to query the device network to obtain defined points and their values (i.e. a configuration scan). Protocol commands may be available that will list all available function codes (i.e. a function scan). These inherent vulnerabilities, along with increasing connectivity between IT an OT networks, make network-based attacks very feasible. Simple injection of malicious protocol commands provides control over the target process. Altering legitimate protocol traffic can also alter information about a process and disrupt the legitimate controls that are in place over that process. A man-in-the-middle attack could provide both control over a process and misrepresentation of data back to operator consoles.

Although advanced telecommunications networks can assist in transforming the energy industry by playing a critical role in maintaining high levels of reliability, performance, and manageability, they also introduce the need for an integrated security infrastructure. Many of the technologies being deployed to support smart grid projects such as smart meters and sensors can increase the vulnerability of the grid to attack. Top security concerns for utilities migrating to an intelligent smart grid telecommunications platform center on the following trends: Integration of distributed energy resources Proliferation of digital devices to enable management, automation, protection, and control Regulatory mandates to comply with standards for critical infrastructure protection Migration to new systems for outage management, distribution automation, condition-based maintenance, load forecasting, and smart metering Demand for new levels of customer service and energy management This development of a diverse set of networks to support the integration of microgrids, open-access energy competition, and the use of network-controlled devices is driving the need for a converged security infrastructure for all participants in the smart grid, including utilities, energy service providers, large commercial and industrial, as well as residential customers. Securing the assets of electric power delivery systems (from the control center to the substation, to the feeders and down to customer meters) requires an end-to-end security infrastructure that protects the myriad of telecommunications assets used to operate, monitor, and control power flow and measurement. "Cyber security" refers to all the security issues in automation and telecommunications that affect any functions related to the operation of the electric power systems. Specifically, it involves the concepts of: Integrity : data cannot be altered undetectably Authenticity : the telecommunications parties involved must be validated as genuine Authorization : only requests and commands from the authorized users can be accepted by the system Confidentiality : data must not be accessible to any unauthenticated users When designing and deploying new smart grid devices and telecommunications systems, it is imperative to understand the various impacts of these new components under a variety of attack situations on the power grid. Consequences of a cyber attack on the grid telecommunications network can be catastrophic. This is why security for smart grid is not just an ad hoc feature or product, it's a complete framework integrating both physical and Cyber security requirements and covering the entire smart grid networks from generation to distribution. Security has therefore become one of the main foundations of the utility telecom network architecture and must be considered at every layer with a defense-in-depth approach. Migrating to IP based protocols is key to address these challenges for two reasons: IP enables a rich set of features and capabilities to enhance the security posture IP is based on open standards, which allows interoperability between different vendors and products, driving down the costs associated with implementing security solutions in OT networks. Securing OT (Operation technology) telecommunications over packet-switched IP networks follow the same principles that are foundational for securing the IT infrastructure, i.e., consideration must be given to enforcing electronic access control for both person-to-machine and machine-to-machine communications, and providing the appropriate levels of data privacy, device and platform integrity, and threat detection and mitigation.

When BAS field networks were developed it was assumed that the field networks would always be physically isolated from external networks and therefore security was not a concern. In today's world many BASs are managed remotely and are thus connected to shared IP networks and so security is definitely a concern, yet security features are not available in the majority of BAS field network deployments . The management network, being an IP-based network, has the protocols available to enable network security, but in practice many BAS systems do not implement even the available security features such as device authentication or encryption for data in transit.

On top of the classical requirements for protection of control signaling, it must be noted that 6TiSCH networks operate on limited resources that can be depleted rapidly in a DoS attack on the system, for instance by placing a rogue device in the network, or by obtaining management control and setting up unexpected additional paths.

Establishing time-sensitive streams in the network entails reserving networking resources for long periods of time. It is important that these reservation requests be authenticated to prevent malicious reservation attempts from hostile nodes (or accidental misconfiguration). This is particularly important in the case where the reservation requests span administrative domains. Furthermore, the reservation information itself should be digitally signed to reduce the risk of a legitimate node pushing a stale or hostile configuration into another networking node. Note: This is considered important for the security policy of the network, but does not affect the core DetNet architecture and design.

Industrial network scenarios require advanced security solutions. Many of the current industrial production networks are physically separated. Preventing critical flows from be leaked outside a domain is handled today by filtering policies that are typically enforced in firewalls.

This memo includes no requests from IANA.

The security considerations of DetNet networks are presented throughout this document.