Abstract: In a communication apparatus of the type performing ISDN LAPD signal processing, the assignment of buffers each for temporarily storing a received data signal is supervised. Idle buffers are reserved in a common idle buffer pool while transmit buffers and receive buffers are supervised for each of service access points. The number of buffers awaiting processing or transmission is monitored at each predetermined period, on the identifier basis. As the number of idle buffers reserved in the idle buffer pool decreases to a value which is less than a predetermined value, the idle buffer assignment allowable for processing is restricted in number on the service access point basis and in a matching relationship to a function of the current number of waiting buffers and a predetermined threshold value.