A method for detecting a timing reference affected by a change in path delay asymmetry in a communications network comprising a master node having a master clock and a plurality of slave nodes each having a respective slave clock is provided. The method comprises: determining that a first timing reference received by a first slave node indicates a time correction to its slave clock greater than a time correction threshold; determining whether one or more other slave nodes have received a timing reference indicating a time correction to their slave clock greater than a time correction threshold; and determining whether the first timing reference is affected by a change in path delay asymmetry based on the determining of whether one or more other slave nodes have received a timing reference indicating a time correction to their slave clock greater than a time correction threshold. Apparatus and a computer program for detecting a timing reference affected by a change in path delay asymmetry in a communications network are also provided.

Multiple network controllers are interconnected in a full mesh structure, e.g., through a cyclical cross connector, to form a distributed control system for a network of a large number of nodes. A network controller acquires characterizing information of links emanating from a respective set of nodes, communicates the information to each other network controller, and determines a route set from each node of the respective set of nodes to each other node of the network. The network controller may determine, for each link included in the route set, identifiers of specific route sets which traverse the link. Accordingly, a state-change of any link in the network can be expeditiously communicated to network controllers to take corrective actions where necessary. A network controller may rank routes of a route set according to some criterion to facilitate selection of a favourable available route for a connection.

A ranging method for an optical network, an OLT, an ONU, and an optical network system are provided. The OLT sends a bandwidth allocation message to the ONU; an OLT receiving a response message sent by an ONU in a first sending mode, wherein the first sending mode comprises sending power and a transmission rate; and the OLT performs ranging on the ONU according to the response message.

A multi-node, quantum communication network for providing quantum-secure time transfer with Damon attack detection is described. The network includes three or more nodes connected via authenticated communication channels forming a closed loop. By determining differences between the local times at as well as the time durations required for photons to travel between the three or more nodes, the network detects a Damon attack, if present. For example, the network imposes a closed loop condition to detect the Damon attack. The network can also use the local time differences and time durations for photon travel between nodes to synchronize the local clocks at the three or more nodes of the network.

An in-vehicle network system includes first device and second device configured to send or receive to or from each other, and an intermediate node connected between the first device and the second device, the intermediate node being configured to output buffered messages in a sequence determined by a relative priority scheme. The first device includes a control unit configured to measure a communication delay for each of a plurality of different priority messages, set a delay representative value less than a maximum value of the plurality of communication delays, and adjust time that a time management unit manages, based on time that the first device manages, time that the second device manages, and the delay representative value.

[Problem] To synchronize timings of transmitting and receiving a pulse signal (1 PPS signal) at a constant interval between communication apparatuses even in a case where an optical fiber connecting the communication apparatuses fluctuates in an optical characteristic and an optical fiber length. [Solution] The time synchronization system 20 transmits and receives a pulse signal at a constant interval between a local apparatus L (apparatus L) and a remote apparatus R (apparatus R) connected through the two-core bidirectional optical fibers F1 and F2 to synchronize time. A propagation delay amount τ1 in the fiber F1 is calculated, from a proportional relationship between T1 and T2 and a proportional relationship of τud and τ1, where T1 represents a propagation delay time difference between a pulse signals P1 and P4 of an identical wavelength λ.sub.1 returned after transmitting a pulse signal P1 of wavelength λ.sub.1 and a pulse signal P2 of wavelength λ.sub.2 different from λ.sub.1 to the remote apparatus R, T2 represents a propagation delay time difference between the pulse signal P1 of wavelength λ.sub.1 and a pulse signal P3 of wavelength λ.sub.2, and τud represents the round-trip delay time between the apparatuses L and R. The pulse signals P1 and P2 are transmitted with a time difference td corresponding to a difference between the current and last calculated propagation delay amounts τ1 being set so that the difference is zero.

Disclosed is a method of operating a network, the network having one or more nodes which are in communication with a server, the server including or being in communication with a high precision time source, to estimate a time delay between the server and each node, comprising initiating a delay request from the server which is transported over a transport layer to the node, the server receiving a delay response from the node receiving the delay request, wherein a timestamp for the delay request and a timestamp for the delay response are times recorded from the high precision time source, wherein the time delay is estimated from half of a time difference between the timestamps.

The present disclosure relates to message transmission methods in a PON system. One example method includes sending, by an optical line terminal (OLT), a first message to an unregistered optical network unit (ONU), where the first message includes at least one piece of indication message, and one piece of indication message of the at least one piece of indication message indicates a first power range and a first time range associated with the first power range, and receiving, by the OLT in the first time range, a registration message sent by the ONU, where a downstream receive power of the ONU falls within the first power range.

Aspects of the present disclosure describe a system and method for synchronizing time, frequency, and phase among a plurality of devices.

A distributed network system can include a master controller having a master clock configured to output a master time, and a master transmission delay time module configured to modify the master time to add a known master transmission delay to the master time to output an adjusted master time. The system can include a first device operatively connected to the master controller and configured to receive the adjusted master time from the master controller.