To allow a system to use the validity connecting to a node through the use of a maintenance equipment by transferring a test cell when an asynchronous transfer mode connection aiming at unidirectional communication is established.

When a point-multipoint connection 3 is established from a sender side terminal equipment 1A to receiver side terminal equipments 1B, 1C, 1D, a maintenance equipment 4A makes a transmission instruction of a test cell to a node 2A at the sender side. A receiver side node 2C receives a test cell by an instruction of the maintenance equipment 4A and verifies the cell and informs the result to the maintenance equipment 4A. Thus, the validity test of the asynchronous mode transfer (ATM) connection aiming at unidirectional communication is attained.