A data network has at least three line branches connected via a common star node to distribute message signals from one of the line branches onto the other line branches, wherein connected to at least one of the line branches is at least one bus-user device is configured to generate in a corresponding transmit mode by a corresponding transmit unit at least one of the message signals, wherein in the corresponding bus-user device, the transmit unit has a current source circuit which, in generating the message signal (16), is configured to inject an electric current into electrical lines of the line branch to which the bus-user device is connected, and via the current source circuit the lines are connected to an internal impedance value of the current source circuit that in transmit mode is constantly greater than 10 times the value of the characteristic impedance, for example greater than 500 Ohms.

Methods and systems are provided for providing secure Ethernet transmissions. In some aspects, an autonomous vehicle system is provided and can include a first system-on-chip being configured to provide data to a second system-on-chip via an Ethernet harness, a first switch being configured to: receive the data from the first system-on-chip, and provide the data to a first transceiver for transmission to the second system-on-chip, the first switch being configured to provide first transmission data to the first transceiver and to prohibit receipt of retrieval data from the second system-on-chip, and the first transceiver configured to communicate with the second system-on-chip via the Ethernet harness.

Methods and systems are provided for providing secure Ethernet transmissions. In some aspects, an autonomous vehicle system is provided and can include a first system-on-chip being configured to provide data to a second system-on-chip via an Ethernet harness, a first switch being configured to: receive the data from the first system-on-chip, and provide the data to a first transceiver for transmission to the second system-on-chip, the first switch being configured to provide first transmission data to the first transceiver and to prohibit receipt of retrieval data from the second system-on-chip, and the first transceiver configured to communicate with the second system-on-chip via the Ethernet harness.

Messaging between an ultra-tag and external microcontroller. In an embodiment, a transmitting device is communicatively connected to a receiving device by a clear-to-communicate line and request line. When data to be transmitted has normal priority, the transmitting device detects whether the clear-to-communicate line indicates that the receiving device is available, indicates a request to transmit on the request line if so, waits until the receiving device is available and then indicates a request to transmit on the request line if not, after indicating a request to transmit, transmits the data when the clear-to-communicate line indicates that the receiving device is unavailable, and, after transmitting the data, releases the indication of the request to transmit on the request line. On the other hand, when the data has high priority, the transmitting device indicates a request to transmit on the request line, regardless of an indication on the clear-to-communicate line.

A relay device includes a plurality of ports, a medium access control unit, and a relay processing unit. Each of the plurality of ports provides a physical layer. The medium access control unit is connected to the plurality of ports. The medium access control unit receives a communication frame from one port out of the plurality of ports. The medium access control unit transmits the communication frame to another port out of the plurality of ports. The relay processing unit transmits, in cooperation with the medium access control unit and through the medium access control unit, the communication frame received from the medium access control unit to another port that corresponds to destination information included in the communication frame.

A relay device includes a plurality of ports, a medium access control unit, and a relay processing unit. Each of the plurality of ports provides a physical layer. The medium access control unit is connected to the plurality of ports. The medium access control unit receives a communication frame from one port out of the plurality of ports. The medium access control unit transmits the communication frame to another port out of the plurality of ports. The relay processing unit transmits, in cooperation with the medium access control unit and through the medium access control unit, the communication frame received from the medium access control unit to another port that corresponds to destination information included in the communication frame.

An embodiment is directed to switchover operations with a virtualized network device in a cloud or remote infrastructure. The virtualized hardware switchover operations may be used to selectively and temporarily provide virtualized control-plane operations to the data-plane of a non-redundant network device undergoing an upgrade or a reboot of its control plane. A non-redundant network device may operate hitless, or near hitless, operation even when its control plane is unavailable.

An embodiment is directed to switchover operations with a virtualized network device in a cloud or remote infrastructure. The virtualized hardware switchover operations may be used to selectively and temporarily provide virtualized control-plane operations to the data-plane of a non-redundant network device undergoing an upgrade or a reboot of its control plane. A non-redundant network device may operate hitless, or near hitless, operation even when its control plane is unavailable.

An optical network unit according to one manner of the present invention includes an optical transceiver configured to be connected to an optical communication line, a plurality of media access control (MAC) processing units, a plurality of user network interface (UNI) ports each connected to one MAC processing unit of the plurality of MAC processing units, and an integration unit integrating a plurality of communication paths connected to the plurality of MAC processing units, respectively, and connected to the optical transceiver.

The present invention provides a network system of a railcar, the network system being capable of efficiently performing maintenance work. One example of the network system of the railcar of the present invention includes: intra-car networks (N1 to N3) to which first and second apparatuses are connected; an inter-car network (NA) for transmission of information between the apparatuses mounted on different cars; routers (R1 to R3) each provided and connected between the corresponding intra-car network (N1 to N3) and the inter-car network (NA) and each including a network address translation portion configured to mutually convert a private address of the first apparatus and an IP address of the inter-car network (NA); and a maintenance transmission path forming unit configured to form a transmission path through which the transmission and reception of the information are performed between a maintenance terminal (5) and a maintenance target apparatus selected from the first and second apparatuses, the transmission path not passing through the network address translation portion of the car on which the maintenance target apparatus is mounted.