PURPOSE: To improve the availability of a work area as well as the processing ability in a protocol control system by acquiring the total using work areas and issuing the requests from each lower rank layer via the request blocks.

CONSTITUTION: A requested layer using work area calculation means 11 calculates the work area that is used by an N layer, and a lower rank layer using work area calculation means 12 calculates the work areas which are used by the layers lower than an N-1 layer. A total using work area calculation means 13 adds together the N and lower rank layers to calculate a total using work area. A work area acquiring means 14 acquires the calculated total work area, and a requested block production means 21 produces a request block in the work area received from the N layer. Then a value setting means 22 sets the value to the produced request block, and a request issue means 23 produces a request. In such a constitution, the availability of a work area is improved together with improvement of the processing ability secured in a protocol control system.