A method of modifying a virtual path capacity in a communication network which transfers a first cell in an asynchronous transfer mode between node apparatuses. The first cell has a first virtual path identifier indicative of a virtual path which the first cell passes through. A bandwidth allocated to the virtual path is modified. Notification of the modification of the bandwidth is provided to a node apparatus included in the virtual path by passing a second cell through said virtual path. The second cell has information of the modification and a second virtual path identifier same as the first virtual path identifier. The second cell is received by the node apparatus and a third cell having information of confirmation of reception of the second cell is returned by the node apparatus.