A communication unit (S1, S2) for industrial automation for use in a communication system (10) of series-connected communication units (M, S1, S2). The communication unit includes a first input (E1), a first output (A1), and an internal clock generator (TG) which is adapted to provide an internal clock signal as system clock for clocking the communication unit (S1, S2), and wherein the communication unit (S1, S2) is configured to receive, via the input (E1), a serial input data stream with payload data. The communication unit (S1, S2) has a timer (ZG) for providing a time value, the timer (ZG) being adapted to provide the time value based on an input symbol clock included in the input data stream.

Systems and methods for implementing bi-directional synchronization propagation between first and second communication devices are provided. The devices are arranged in a loop-timing configuration. A method includes detecting, by the second communication device, a switching signal comprising an indication to switch a timing role of the second communication device and engaging, by the second communication device, in a synchronization handshake with the first communication device over a communication link based on the detection of the switching signal. Engaging in the synchronization handshake includes determining whether the first communication device is configured to support bi-directional synchronization propagation. The method includes switching the timing role of the second communication device based on the synchronization handshake.

There is provided a time synchronization method, including: an adjustment stage including N adjustment cycles, N being an integer greater than 1; in each adjustment cycle, generating a physical clock signal at least according to a pre-acquired frequency control word corresponding to the adjustment cycle, and obtaining logical time at least according to the physical clock signal and a physical time deviation; a clock slope of the physical clock signal generated in each adjustment cycle reaches its corresponding target value, and the target values of the clock slopes of the physical clock signals in the N adjustment cycles gradually approach 1; the physical time deviation is: a time difference between the reference time and the physical time corresponding to the physical clock signal in an Nth adjustment cycle at the end of the Nth adjustment cycle. A time synchronization device and a network node device are provided.

Systems, apparatuses and methods for synchronizing communication actions between multiple communication devices by accounting for discrepancies between timing functionality in communicating devices. A time value indicative of a remote device's view of current time is received. Where it is determined that the time value differs from a locally generated view of current time by at least an established amount, the range of time in which communications signals with the remote device will be monitored and transmitted is extended.

A network device includes a packet processor, a plurality of interface circuits, a phase-locked loop (PLL) circuit and a configuration controller. The interface circuits are configured to transmit and receive signals to/from other devices that are coupled to the network device. A master interface circuit among the interface circuits is configured to recover a network clock from a received signal. The PLL circuit is configured to generate an interface clock based on a system clock of the network device and a configuration of the PLL circuit and to provide the interface clock to the plurality of interface circuits to govern communication timings of the interface circuits. The configuration controller is configured to detect a difference of the interface clock relative to the recovered network clock, and to determine the configuration of the PLL circuit based on the difference to govern operation of the PLL circuit.

A method for indicating one-way latency in a data network, with continuous clock synchronization, between first and second node having clocks that are not synchronized with each other includes a continuous synchronization session and a measurement session. The method repetitively sends predetermined synchronization messages from the first node to the second node and from the second node to the first node, calculates a round trip time for each message at the first node, updates a synchronization point if the calculated round trip time is smaller than a previously calculated round trip time, stores the updated synchronization points of a synchronization window, and calculates a virtual clock from the updated synchronization points of the synchronization window. The measurement session collects multiple measurements of one-way latency between the first and second nodes using the virtual clock, and generates a latency profile by interpolating the multiple measurements.

A network includes a first plurality of nodes operating in a first clock domain based on a first clock source, a second plurality of nodes operating in a second clock domain based on a second clock source, and synchronization circuitry accessible to both of the clock domains without requiring network traffic between the clock domains. The synchronization circuitry is configured to periodically calculate a drift rate between the time of day in the respective clock domains. Each node in one of the clock domains is configured to, when sending a message to a node in the other of the clock domains, calculate a time of day in the other of the clock domains based on an actual time of day in the one of the clock domains and the drift rate, and to include, in the message to the node in the other clock domain, the calculated time of day.

A time synchronization method and apparatus for network devices and a time synchronization server are disclosed, which relates to the field of communication technology, to solve the problem of failing to perform high-capacity and centralized time synchronization due to less timely processing of a time synchronization message in the related art. The method includes: a programmable logic device receiving and parsing a time synchronization message from a to-be-synchronized device in a physical layer, wherein the time synchronization message carries a synchronization parameter; the programmable logic device generating a reply message for the time synchronization message according to local reference time and update configurations of the synchronization parameter; and the programmable logic device sending the reply message and a link establishment and communication message from a CPU to the to-be-synchronized device in a preset order.

An aspect of the present disclosure enables each receiver node of a wireless network to synchronize active widows with those of the sender node. In an embodiment, a receiver node receives a packet from a sender node on a wireless network, with the packet including data indicating a position of the packet in an active window of the sender node. The receiver node determines the position at which the packet is received in an active window of the receiver node. The receiver node determines a difference between the two positions and adjusts a start position of the next active window (of the receiver node) based on the determined difference to synchronize the future active windows at the receiver node to respective active windows at the sender node.

A method of operation of a Multiprotocol Label Switching network involves, in an active node of the network, receiving a first data packet from a source node and forwarding the first data packet to a destination node. At the same time, the active node measures a residence time of the first data packet in the active node. The active node then sends a further data packet containing residence time information.