Fault-tolerant Clock Synchronization using Precise Time Protocol Multi-Domain Aggregation

Distributed real-time systems often rely on time-triggered communication and task execution to guarantee end-to-end latency and time-predictable computation. Such systems require a reliable synchronized network time to be shared among end-systems. The IEEE 1588 Precision Time Protocol (PTP) enables such clock synchronization throughout an Ethernet-based network. While security was not addressed in previous versions of the IEEE 1588 standard, in its most recent iteration (IEEE 1588-2019), several security mechanisms and recommendations were included describing different measures that can be taken to improve system security and safety. One proposal to improve security and reliability is to add redundancy to the network through modifications in the topology. However, this recommendation omits implementation details and leaves the question open of how it affects synchronization quality. This work investigates the quality impact and security properties of redundant PTP deployment and proposes an observation window-based multi-domain, PTP end-system, design to increase fault-tolerance and security. We implement the proposed design inside a discrete-event network simulator and evaluate its clock synchronization quality using two test-case network topologies with simulated faults.