A connecting node in a first sub-network system reserves a transmission channel in a connecting network, reads waveform data having a designated signal name from a TL frame in the first sub-network system, and writes the read waveform data into the reserved transmission channel in a TL frame in the connecting network, and a connecting node in a second sub-network system reserves a transmission channel in the second sub-network system, reads the waveform data having the designated signal name from the TL frame in the connecting network, and writes the read waveform data into the reserved transmission channel in a TL frame in the second sub-network system.