Patent ID: 6987733

Claim:
An Asynchronous Transfer Mode (ATM) communication apparatus which is connected to a plurality of input lines and a plurality of output lines and transmits a cell received from each of the input lines to one of the plurality of output lines, which is specified by connection identification information included in a header of the cell, comprising: a buffer memory for temporarily storing cells received from each of the input lines; a write control unit for writing the cells received from each of the input lines into the buffer memory so that cells stored in the buffer memory form cell queues corresponding to connections for each output line; a read control unit for reading out cells from each of cell queues formed in the buffer memory while guaranteeing a minimum cell rate predetermined for each connection within a range not exceeding a predetermined peak cell rate; and means for adding congestion indication to a cell read out from a cell queue of which stored cell amount exceeds a preset threshold, wherein the read control unit comprises: a guaranteed bandwidth table in which information for allocating time slots to each of a plurality of connections multiplexed on the output line while guaranteeing a minimum cell rate is stored for each of the output lines, a shared bandwidth table in which information indicative of an allocation range of idle time slots allowed to each of the connections multiplexed is stored for each of the output lines, and means for determining a connection for which a cell is to be read out by referring to the shared bandwidth table in a time slot which enters an idle state since there is no cell to be transmitted in a cell queue in a connection designated by the guaranteed bandwidth table and an idle time slot to which a connection is not designated in the guaranteed bandwidth table.