A communication device capable of preventing occurrence of packet loss in a network in which path configuration is determined by RSTP. In a switch, a control unit detects reconnection of a port that is in a discarding state and sends back, to a transmission source, a BPDU that includes a path cost having a value larger than that of a path cost contained in a BPDU that is received after the reconnection from the port at which the reconnection is detected.

One aspect of the present invention is a communication system for a passive optical network that includes: an OLT (optical line terminal); a first splitter configured to output an optical signal that is output from the OLT, to optical communication channels from a first port and a second port; a plurality of second splitters that are connected between the first port and second port of the first splitter using optical communication channels; and ONUs (optical network units) that are connected to the respective second splitters using optical communication channels.

An object is to provide a route switching method, a transfer device, and communication system that can continue communication even during route switching work. In a route switching method according to the present invention, in bypass transfer that transfers a packet while bypassing a non-transferable route, the transfer device having detected the non-transferable route attaches a bypass packet flag to the packet that passes through a non-transferable route and specifies the packet as a bypass packet, the transfer device having detected the non-transferable route returns the bypass packet and transfers the bypass packet in a direction opposite to that of the packet in the ring network, and the transfer device for which the blocked port is set in the ring network transfers the bypass packet through the blocked port before the route switching work.

A communication device with an activated ring controller provided in both first and second subnetworks for data transmission in a redundantly operable communications network, which includes at least one first and one second subnetwork, which each include communication devices interconnected within a ring topology, wherein the subnetworks are interconnected via coupling line sections to which coupling communication devices are connected, where the coupling line section to which a selected coupling communication device is connected is operated as an inactive reserve coupling line section until a disruption occurs, whilst another coupling line section is operated as an active main coupling line section, where coupling communication devices connected to the main coupling line section transmit status datagrams to the selected coupling communication device which additionally include configuration information about whether the particular coupling communication device connected to the main coupling line section is an activatable ring controller.

A communication device with an activated ring controller provided in both first and second subnetworks for data transmission in a redundantly operable communications network, which includes at least one first and one second subnetwork, which each include communication devices interconnected within a ring topology, wherein the subnetworks are interconnected via coupling line sections to which coupling communication devices are connected, where the coupling line section to which a selected coupling communication device is connected is operated as an inactive reserve coupling line section until a disruption occurs, whilst another coupling line section is operated as an active main coupling line section, where coupling communication devices connected to the main coupling line section transmit status datagrams to the selected coupling communication device which additionally include configuration information about whether the particular coupling communication device connected to the main coupling line section is an activatable ring controller.

Examples disclosed herein relate to managing a second ring link failure in a multi-ring Ethernet network. In an example, an inter-connection network node in a multi-ring Ethernet network comprising a major ring and a sub-ring may propagate a signal failure (SF) event, received in response to a second ring link failure in the major ring, to one or more nodes in the sub-ring. In response to receiving the SF event, a Ring Protection Link (RPL) on the sub-ring may be unlocked to allow network traffic through the RPL and avoid loop formation on the multi-ring Ethernet network. The sub-ring may be moved to the ring protection switching state, including performing a filtering database (FDB) flush at every node on the multi-ring Ethernet network whereby all MAC addresses and related port associations for traffic forwarding are cleared from the FDB.

Examples disclosed herein relate to managing a second ring link failure in a multi-ring Ethernet network. In an example, an inter-connection network node in a multi-ring Ethernet network comprising a major ring and a sub-ring may propagate a signal failure (SF) event, received in response to a second ring link failure in the major ring, to one or more nodes in the sub-ring. In response to receiving the SF event, a Ring Protection Link (RPL) on the sub-ring may be unlocked to allow network traffic through the RPL and avoid loop formation on the multi-ring Ethernet network. The sub-ring may be moved to the ring protection switching state, including performing a filtering database (FDB) flush at every node on the multi-ring Ethernet network whereby all MAC addresses and related port associations for traffic forwarding are cleared from the FDB.

A machine automation system for controlling and operating an automated machine. The system includes a controller and sensor bus including a central processing core and a multi-medium transmission intranet for implementing a dynamic burst to broadcast transmission scheme where messages are burst from nodes to the central processing core and broadcast from the central processing core to all of the nodes.

A machine automation system for controlling and operating an automated machine. The system includes a controller and sensor bus including a central processing core and a multi-medium transmission intranet for implementing a dynamic burst to broadcast transmission scheme where messages are burst from nodes to the central processing core and broadcast from the central processing core to all of the nodes.

Techniques for uplink connectivity determination are disclosed. In an example, a Frame Link Module (FLM) in a frame, belonging to a group of frames connected in a ring network, may generate an uplink discovery packet. The FLM may determine, based on a Link Layer Discovery Protocol (LLDP) packet received by the standby uplink from a customer network accessing the ring that the standby uplink has a link to the customer network. The FLM may forward the uplink discovery packet to the standby uplink via a Peripheral Component Interconnect (PCI) interface. The FLM may send the uplink discovery packet to the customer network through the standby uplink directed to an owner FLM. The owner FLM may monitor receipt of the uplink discovery packet from the customer network through a current active uplink and on successful receipt may determine that the standby uplink and switches in the customer network are correctly configured.