Abstract: The central apparatus obtains the destination information of a plurality of terminal devices, generates one request packet consolidating the obtained plural destination information, and transmits the generated one request packet. The relay unit receives one request packet, generates a plurality of request packets on the basis of the consolidated destination information, and transmits the generated request packet. The relay unit receives reply packets from a plurality of terminal devices, generates one reply packet consolidating the destination information of the transmission origins of the received plural reply packets, and transmits them to the central apparatus. The central apparatus receives the returned one reply packet and determines continuation and blockade of the network connection for each terminal device.

Abstract: A transmission apparatus transmits/receives test frames to test connectivity between the transmission apparatus and another transmission apparatus to/from the other transmission apparatus at regular intervals. The transmission apparatus includes a frame length changing unit that changes a frame length, which is capacity of each of the test frames, at every transmission when the test frames are transmitted to the other transmission apparatus at the regular intervals; a reception determining unit that determines whether the test frames having changed frame lengths transmitted from the other transmission apparatus at the regular intervals have been received at the regular intervals; and a frame length calculating unit that calculates the frame length of the test frame that has not been received if the reception determining unit determines that the test frame has not been received.

Abstract: The central apparatus obtains the destination information of a plurality of terminal devices, generates one request packet consolidating the obtained plural destination information, and transmits the generated one request packet. The relay unit receives one request packet, generates a plurality of request packets on the basis of the consolidated destination information, and transmits the generated request packet. The relay unit receives reply packets from a plurality of terminal devices, generates one reply packet consolidating the destination information of the transmission origins of the received plural reply packets, and transmits them to the central apparatus. The central apparatus receives the returned one reply packet and determines continuation and blockade of the network connection for each terminal device.

Abstract: A data sending system which prevents a parity error occurrence in a data receiving unit is provided. The data sending system provided is related to data sending systems and, particularly, to a data sending system where plurality of data sending units share a path for data transmission. The data sending system provided comprises a network consisting of a data path and control path, a control unit for instructing data sending through said control path, one or plural data sending units for sending, according to an instruction from said control path, data to a specific one of plural logical paths of said data path, and a data receiving unit permanently connected to the one of plural logical paths of said data path. Said control unit has a determining section which determines a time span, during which no sending data exists in a logical path connected to said data receiving unit, and also instructs a specific unit of said data sending units to send dummy data during the time span.

Abstract: A data sending system which prevents a parity error occurrence in a data receiving unit is provided. The data sending system provided is related to data sending systems and, particularly, to a data sending system where plurality of data sending units share a path for data transmission. The data sending system provided comprises a network consisting of a data path and control path, a control unit for instructing data sending through said control path, one or plural data sending units for sending, according to an instruction from said control path, data to a specific one of plural logical paths of said data path, and a data receiving unit permanently connected to the one of plural logical paths of said data path. Said control unit has a determining section which determines a time span, during which no sending data exists in a logical path connected to said data receiving unit, and also instructs a specific unit of said data sending units to send dummy data during the time span.