A first network device may receive, from a second network device, a clock quality indication that is associated with a clock of the second network device, wherein the clock of the second network device is a reference clock for a network that includes the first network device and the second network device. The first network device may determine, based on a clock signal of the second network device, that a quality metric of the clock does not satisfy a threshold. The first network device may provide, to the second network device, a clock fault notification to cause the second network device to downgrade the clock quality indication transmitted by the second network device. The first network device may select a new reference clock for the first network device based on receiving the downgraded clock quality indication from the second network device.

A system is provided for synchronizing clocks. The system includes a plurality of devices in a network, each device having a local clock. The system is configured to synchronize the local clocks according to a primary spanning tree, where the primary spanning tree has a plurality of nodes connected through a plurality of primary links, each node of the plurality of nodes representing a respective device of the plurality of devices. The system is also configured to compute a backup spanning tree before a failure is detected in the primary spanning tree, wherein the backup spanning tree includes one or more backup links that are different from the primary links. As such, upon detection of a failure in the primary spanning tree, the system reconfigures the plurality of devices such that clock synchronization is performed according to the backup spanning tree.

Techniques described herein may be used for determining an offset between clocks in a network. Such techniques may include obtaining, by a passive time device, a first timestamp pair corresponding to a first time protocol message; obtaining, by the passive time device, a second timestamp pair corresponding to a second time protocol message; and calculating, by the passive time device, a clock offset between a time protocol master and the passive time device using the first timestamp pair, the second timestamp pair, and a pre-determined time delay constant corresponding to a network tap.

A performance instrument for a vehicle wherein an electronic device receives one or more operational quantities from internal sensors and/or external sensors and represents the one or more operational quantities as an analog clock face so that each clock hand is a function of one of the one or more operational quantities. The analog clock face representation provides at-a-glance apparency of the operational quantities for a user of the vehicle.

[Problem] To select an optimal transmission path having a minimum total MTIE value of total MTIE values between a plurality of master apparatuses configured to transmit time information serving as a reference and a specific relay apparatus configured to receive the time information via a plurality of relay apparatuses to achieve time synchronization. [Solution] A time path selection apparatus 30 selects a transmission path employed for time synchronization, on the basis of a MTIE value evaluated in each of relay apparatuses 13 to 16, between master apparatuses 11 and 12 configured to transmit time information serving as a reference and a relay apparatus 15 or 16 at an edge configured to receive the time information via a relay apparatus 13 or 14 to achieve the time synchronization. The time path selection apparatus 30 includes a time information reception unit 31 configured to receive the MTIE value evaluated in each of the relay apparatuses 13 to 16, and an optimal path derivation unit 33 configured to evaluate, on the basis of the received MTIE value, a total MTIE value for every transmission path in transmission paths between the relay apparatus 15 and the master apparatuses 11 and 12 and to select and derive, as the transmission path employed for the transmission path for time synchronization, a transmission path where the total MTIE value is a minimum (170 ns).

A communication system (100) includes communication device (1) to communication device (9). Communication device (1) to communication device (9) select a first representative device that represents a same domain. Communication device (3) is selected from domain D (1), communication device (6) is selected from domain D (2), and communication device (9) is selected from domain D (3). For communication device (3), communication device (6), and communication device (9) selected from each domain, communication device (3) sets to communication device (3), communication device (6) sets to communication device (6), and communication device (9) sets to communication device (9), domain D (0) as a common domain to which communication device (3), communication device (6), and communication device (9) belong. Communication device (3), communication device (6), and communication device (9) select communication device (9) as a network grandmaster that is a second representative device that represents domain D (0).

The present application generally relates to network timing synchronization in the presence of link faults including apparatus and methods In various embodiments, a method includes generating a time synchronization signal, transmitting the time synchronization signal from a first switch to a second switch via a first link and from the first switch to a third switch via a second link, detecting a link failure of the first link, and transmitting the time synchronization signal from the second switch to the third switch via a third link in response to the link failure.

This application discloses a clock synchronization method and apparatus, and related storage medium, and pertains to the field of communications technologies. A network device receives an announce message from a first master clock node and an announce message from a second master clock node; and when an identifier of a first clock source node carried in the announce message of the first master clock node is the same as an identifier of a second clock source node carried in the announce message of the second master clock node, selects a master clock node with a smaller clock deviation from the first master clock node and the second master clock node, and then calibrates a clock of the network device based on time information of the master clock node. The precision of clock synchronization by the network device is improved.

A system is provided for synchronizing clocks. The system includes a plurality of devices in a network, each device having a local clock. The system is configured to synchronize the local clocks according to a primary spanning tree, where the primary spanning tree has a plurality of nodes connected through a plurality of primary links, each node of the plurality of nodes representing a respective device of the plurality of devices. The system is also configured to compute a backup spanning tree before a failure is detected in the primary spanning tree, wherein the backup spanning tree includes one or more backup links that are different from the primary links. As such, upon detection of a failure in the primary spanning tree, the system reconfigures the plurality of devices such that clock synchronization is performed according to the backup spanning tree.

A method establishes an improved clock topology for a computation system, where the computation system is a network of nodes, and where multiple nodes are capable of being a grandmaster clock source. The method includes sequentially selecting each selectable node as an acting grandmaster node, the acting grandmaster node sending announce messages, each node with a determinative communication requirement extracting topology information from the announce messages. The above steps are repeated with another node until each selectable node has been an acting grandmaster. The method then includes selecting the clock source based on the best clock topology for the set of nodes with determinative communication requirements.