PURPOSE: To improve the reliability by performing the distribution management while allowing each transmission node device to automatically set the broadcast type cell layer connection and to omit the excess transmission of cell by unnecessitating the setting of cell layer connections for each reception node device in setting the broadcast connection in the node device of the ring-shape network system dividing cells in a data transmission unit.

CONSTITUTION: When a connection setting request processing section 10 receives the request of setting the broadcast cell layer connection, a logic channel number selection section 6 refers to a using logical channel number recording section 5 to select one of the unused logical channel numbers. A dummy broadcast request section 7 transmits the dummy cell storing the selected logical channel number and the self group address as an address. A logical channel collision detection section 8 monitors the cell making a round of the ring-shape network 3. When no collision of the logical channel occurs, the number is used as the logical channel of the broadcast cell.