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.

The forwarding of a management message received in a network device includes determining whether a previously received message sent by the same sender has looped back to the network device. The message is forwarded if the received message is not a loop back of a previously received message, and dropped otherwise.

In one embodiment, a computer apparatus includes a first NIC including at least one network interface port to transfer data with a first packet-data network (PDN) including a master clock to provide a clock synchronization signal S1, a first physical hardware clock (PHC) to maintain a time value T1 responsively to S1, and a first clock controller to generate a clock synchronization signal S2 responsively to S1, S2 having a frequency set responsively to S1, and send S2 over a connection to a second NIC including at least one network interface port to transfer data with a second PDN, a second PHC, and a second clock controller to receive S2, update the second PHC with a time value T2 responsively to S2, send another clock synchronization signal to network nodes in the second PDN responsively to T2, the second NIC acting as a master clock in the second PDN.

A method for exchanging a clock synchronization packet performed by a network apparatus, including: exchanging a clock synchronization packet with a first clock source, where the network apparatus includes a boundary clock; determining a first time deviation of the boundary clock relative to the first clock source according to the clock synchronization packet exchanged with the first clock source, where the boundary clock avoids performing an operation of calibrating a time of a local clock of the boundary clock according to the first time deviation; and sending a clock synchronization packet to a first slave clock of the boundary clock, where the clock synchronization packet includes a first timestamp, a value of the first timestamp is equal to a first corrected value, and the first corrected value is a value obtained by the boundary clock by correcting the time of the local clock by using the first time deviation.

A method for assisting in synchronization of slave clocks in a communication network comprises receiving, in a node of the communication network, a message comprising a value of a synchronization accuracy (σ.sub.rec) of a first upstream node in the communication network. A value of an accuracy (σ.sub.link) of a link latency unbalance between forward and reverse signalling in a link on which the node received the message is obtained. A value of a total synchronization accuracy (σ.sub.tot) of the node comprises at least the accuracy (σ.sub.link) of the link latency unbalance of the link on which the node received the message is calculated. A node for assisting in synchronization of slave clocks in a communication network is also presented.

There is provided a technique of clock managing in a packet data network implementing a time-transfer protocol. The technique comprises: modifying, by the timing-server, a timestamp record to enable a controllable access to data informative of the least significant part of clock-informative data (CLSP data), wherein modifying the timestamp record comprises modifying the least significant part of the timestamp record (RLSP) to comprise the CLSP data in an encrypted form or to comprise values substituting, in a predefined manner, the CLSP data; transferring the modified timestamp record to all timing-clients, wherein CLSP data are transferred in a controllable access manner; enabling access to the CLSP data merely to authorized timing-clients among the plurality of timing-clients; and enabling the authorized timing-clients to obtain the CLSP data and synchronize the respective clocks using the CLSP data together with data informative of the most significant part of the clock-informative data.

Upon receiving a dummy packet, a data collection terminal slave device (2) appends, to a return packet, a timestamp indicating the reception time of the dummy packet and a timestamp indicating the transmission time of the return packet, and transmits the return packet to a data collection terminal master device (3). When performing a time synchronization process, the data collection terminal master device (3) transmits the dummy packet to the data collection terminal slave device (2). Upon receiving the return packet, the data collection terminal master device (3) calculates a synchronization deviation time of the data collection terminal master device (3) and the data collection terminal slave device (2) and a propagation delay time between the data collection terminal master device (3) and the data collection terminal slave device (2), based on the transmission time of the dummy packet and the reception time of the return packet, and the reception time of the dummy packet and the transmission time of the return packet obtained from the timestamps of the return packet.

A system and method for transmitting packets from a transceiver to a repeater in the presence of relative motion between the transceiver and the repeater. In some embodiments, the method includes: adjusting a plurality of transmission times; transmitting each of a plurality of packets, at a respective adjusted transmission time, from the transceiver to the repeater; and retransmitting, by the repeater, each of the packets, at a respective retransmission time, each of the retransmission times being, as a result of the adjusting, more nearly the same as it would have been, in the absence of: the relative motion, and the adjusting.

This application provides a synchronization method and an apparatus, to implement synchronization with a TSN clock in a mobile network. The synchronization method is performed by a first network element in a relay network. The relay network includes a radio access network RAN device and a terminal device. The method includes: The first network element receives a clock synchronization packet. The first network element determines first duration of the relay network, where the first duration of the relay network includes a first downlink transmission delay of transmitting the clock synchronization packet between the RAN device and the terminal device. The first network element determines a time correction field of the relay network, where the time correction field includes the first downlink transmission delay.

According to an embodiment, in a network system 1 in which at least one data of the audio data and the video data is transmitted from a first node to a second node through a network, the second node includes a processor configured to generate a clock signal for reproduction of the audio data and the like. The processor is configured to synchronize a current time in the second node with a current time in the first node, based on a transmission time that is based on the current time in the first node and is contained in a received extended CRF frame, a reception time that is based on the current time in the second node and at which the extended CRF frame is received, and a delay time period occurring while the extended CRF frame is transmitted from the first node to the second node.