To construct an optimum execution time environment in a network hierarchy model and to efficiently perform data communication at high speed by applying first processing through a first program object to a data unit, afterwards, supplying the data unit to a second program object and applying second processing.

The data unit generated by application objects 20 and 21 in an mCoop 13 is successively dispatched to program objects 22-26 in an mNet 14 and processed by the respective program objects 22-26. A device driver 27 in an mDrive 15 has the function of a serial driver, and a device driver program 28 has the function of an ATM driver. The data unit, to which processing is applied by the program objects 22-26, is sent out of these device driver programs 27 and 28 of the lowest layer to a physical network.