Abstract: A resource usage of a switching section can be reduced and operations for connection can be facilitated in high speed even if a failure occurs on the switching section by a line switching method. The line switching method in an asynchronous transfer mode exchange including a line concentration and distribution device, to which a subscriber circuit for accommodating a plurality of subscribers, is connected and a switching section, includes the steps of comparing information for identifying a path of a subscriber's cell with information registered in a monitor table, detecting that a first subscriber circuit for accommodating a called subscriber is connected to a same line concentration and distribution device to which a second subscriber circuit for accommodating calling subscriber is connected, and looping back and connecting the call sent from the calling subscriber to the called subscriber without passing through the switching section.

Abstract: The quality and performance of the connectionless communications system are improved. When a BOM is received, the destination address DA of the L3-PDU stored in the payload of the BOM is retrieved, and the tag information is obtained from the DA (S11). The output message identifier MID is reserved (S12), and the tag information and output MID are assigned to the BOM (S13). Then, the tag information and output MID are written to the table. When a COM is received, the tag information and output MID are retrieved using the MID of the COM as a key, and the information is provided for the COM (S31 and S32). When an EOM is received, the tag information and output MID are retrieved using the MID of the EOM as a key, and the information is provided for the EOM (S41 and S42). Then, the output MID is released (S43).