Systems and methods are disclosed for direct passive monitoring of packet delay variation and time error in network packet communications. Packets traversing between slave and master clocks are monitored to provide direct results of the actual conditions without the need to rely upon inference determinations. Certain embodiments provide tap configurations to monitor packet flows, while certain other embodiments provide in-line configurations to monitor packet flows. Certain further embodiments provide multiple monitoring devices that can be used for passive monitoring purposes, such as passive monitoring to test boundary clock. These multiple monitoring devices can be configured to be within a single or different test instruments. Other variations are also described.

A packet processing method includes receiving a first packet by a first receiving interface of a media conversion module of a first network device, where the first packet includes a first alignment marker (AM), sending a second packet by a first sending interface of the media conversion module, where the second packet includes the first AM, and the second packet is the first packet processed by the media conversion module, and calculating a time interval T.sub.1 between a time at which the media conversion module receives the first packet and a time at which the media conversion module sends the second packet, where the T.sub.1 is used to compensate for a first timestamp at which the first network device receives or sends the third packet.

The present disclosure discloses a method for remotely configuring a Precision Time Protocol PTP service of an Optical Network Unit ONU. The method includes: after an ONU performs an initialization, the ONU creates a PTP management entity; the ONU receives a PTP management entity attribute sent by an OLT and set by the OLT; and the ONU parses the PTP management entity attribute sent by the OLT and sets a corresponding PTP service according to the PTP management entity attribute. The present disclosure further discloses an ONU, an OLT and a system corresponding to the method.

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.

In a hybrid network comprising both guided and wireless communications technologies, a grandmaster clock is designated in one portion of the network and can be propagated across to the other portion by means of a timing synchronization message. This message may include timestamping information and other information to enable recipient devices to correctly synchronize to the grandmaster clock.

Techniques are disclosed for performing time synchronization for a plurality of computing devices that exhibit asymmetric path delay. In one example, processing circuitry receives data indicative of a graph comprising a plurality of nodes and vertices, wherein each node represents a clock and each vertex represents a bidirectional path between two clocks. Each bidirectional path has a first path delay in a first direction that is different from a second path delay in a second direction. The processing circuitry determines one or more closed loops in the graph and a path delay of the closed loop. The processing circuitry applies a minimization function to the path delay of each closed loop to determine values for the first and second path delays of each bidirectional path. The processing circuitry applies, based on the values for the first and second path delays of each bidirectional path, a time correction to a clock.

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.

The present disclosure provides a high-precision time synchronization method. With the method, a traditional time synchronization protocol of a traditional IEEE 1588 network can be improved by introducing a periodic perturbation time between any two nodes in the time synchronization network, the perturbation time can be caused by changing the lengths of transmission paths or introducing clock phase perturbation due to different clock frequencies in the transistor and the receiver. With the method, the relevance of resulting errors of multiple synchronizations can be eliminated, and the perturbation can be compensated by means of statistical averaging, such that the synchronization error due to the low clock resolution of the synchronization node can be decreased. The method may realize the time synchronization at the precision of nanosecond, having significant advantages over the traditional time synchronization method based on IEEE 1588 protocol.

[Problem] It is possible to improve the quality of time information by suppressing a jump in time which arises when switching a transfer path in a BC apparatus to which transfer paths of time information of at least 2 systems are connected to an input side. [Solution] A time synchronization apparatus 20 is mounted on a BC apparatus 12c in which two systems of at least a 0-system route (0-system) and a 1-system route (1-system) are connected to an input side, and includes a time correction value holding unit 26 configured to hold a 0-system correction value in which a time error resulting from delay of UTC due to performance inherent to the BC apparatus is the same value as a time error accumulated on the 0-system side and a 1-system correction value in which the time error is the same value as a time error accumulated on the 1-system side. Further, a failure restoration detection unit 23 configured to detect a failure in the 0-system or the 1-system, a time calculation unit 24 configured to perform correction by subtracting a 1-system correction value relating to a normal 1-system from UTC having time error accumulated on the normal 1-system side, when a failure in the 0-system is detected, and a path switching unit 25 configured to switch to the normal 1-system side such that the UTC after correction is transferred, when the failure is detected, are included.

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.