With the object of eliminating congestion that has occurred in a station which can not prevent or eliminate the occurrence of congestion autonomously, the SMPP response time in output interfaces 21h-21k of a first PPG 21 are measured and when the time mta, which is m-times of the SMPP response time ta in the normal state, is exceeded, congestion is assumed to occur in an interconnected station of the first PPG 21 and the response to push transfer request in an input interface 21a is delayed. Further, changes in the filling ratio in a buffer memory 21b are monitored and when the filling ratio exceeds h %, a decision is made that congestion has occurred in the first PPG 21 and the response to the push transfer request in the input interface 21a is delayed.