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Industrial Ethernet Book 104

TAepcphlincoaltoiognys stream. Besides the targeted overloading of certain time slots, the IEEE1588 protocol for time synchronization is a potential attack target itself as well. Many automation networks today already use PTP. For this reason, it will be utilized in many applications for the synchronization of TSN clocks. Yet, by design, PTP has no integrated security mechanism and relies completely on the security mechanisms that are present in the network. With no means of network security in place, a potential attacker could, therefore, hijack the function of the central time source, the “grandmaster”, using falsified PTP data packets. The false grandmaster could then send time synchronization information with large jitter into the network, sabotaging the proper alignment of the time slots on the individual devices. Furthermore, the attacker could enforce time discontinuity, which would result in many time-sensitive end-device applications to go to a safe shutdown state immediately. So, what does that mean for cyber security in a TSN network? Network protection For the most part, traditional security solutions such as firewalls will remain key mechanisms for securing a TSN network. The real-time properties of TSN, however, have an impact on the design of some of these security measures. If data packets that are passing through a firewall cannot be checked in real-time, because the software has to look into the payload of each forwarded packet (Deep Packet Inspection), the computational overhead creates an additional transmission delay. If this delay is not taken into account when time slots are reserved, there is a risk that data packets will be delayed to a point, where they move into reserved time slots for which they were not intended. One possibility to get on top of this issue is to employ firewall technologies that are guaranteed to work in real-time. Another possibility is to make the delay visible in the network, such that SOURCE: BELDEN The Time-Aware Scheduler implements time-based prioritization via newly-introduced Time-Aware Gates. SOURCE: BELDEN With Ethernet frame pre-emption, the guard band size can be reduced to the size of a partial packet. the calculation of the TDMA schedule can be adjusted accordingly when reserving a stream. This type of delay transparency also applies to switches, which support security mechanisms at the hardware level, for example, Access Control Lists (ACL) and stateless packet filters. Even though these mechanisms usually operate at wire-speed, a slight delay may still be introduced. This has no impact on regular Ethernet networks. In TSN networks, where data transmissions rely on microsecond precision or even less, data communication could, however, be disrupted. Nonetheless, this does not imply that established security mechanisms can no longer be used in a TSN network. Nothing is With the Credit-Based Shaper, data streams with reserved bandwidths are handled with higher priority than best effort traffic, as long as positive transmission credit is available. 8 industrial ethernet book 2.2018


Industrial Ethernet Book 104
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