SYSTEM FOR CONTROLLING CELL ANNULMENT

PROBLEM TO BE SOLVED: To transfer a prescribed kind of cell without annulment even when a congestion state occurs inside an ATM exchange network concerning a cell annulment control system in the ATM exchange network. SOLUTION: In the ATM exchange network providing an ATM switch 100 which output a cell inputted from an input terminal 200 to an output terminal 300 by way of an incorporated buffer 101, the ATM switch 100 is constituted by providing a cell kind detecting means 102 for detecting the prescribed kind cell from the respective cells inputted from the input terminal 200 and a cell annulment protecting means 103 for reducing the possibility of the prescribed kind of cell detected by the cell kind detecting means 102 to be annulled even when a congestion occurs in the buffer 101.