A data transmission apparatus connecting to a network consisted of a plurality of data transmission apparatuses comprises a disconnecting device that disconnects a connection established between a transmission plug of a transmitting node and a reception plug of a receiving node, both nodes being connected to the network, an optimization requesting device that requests optimization of transmitting sequences to the transmitting node, a receiver that receives information about a transmission plug newly assigned to the transmitting sequence used by the transmitting nodes of which connection has been disconnected by the disconnecting device, the information being received as an answer for the optimization request from the transmitting node, and a connecting device that establishes a new connection between the newly assigned transmission plug and the reception plug of the receiving node of which connection has been disconnected by the disconnecting device.