Abstract: A looping detection apparatus used in a frame-relay communications system and capable of detecting looping without fail through confirmation of link completeness according to a two-way PVC status confirmation procedure. A status enquiry message transmitting unit transmits a status enquiry message with a first identification code carried at a predetermined position of a signal by means of which the status enquiry message is transmitted. On receiving the status enquiry message, a status response message returning unit creates a status response message based on the status enquiry message and sends the status response message back to a first node with a second identification code carried at the predetermined position.

Abstract: The present invention has as its object to provide a frame relay switching node for enabling the performance of fault traces without causing insufficiency in the trace area. To achieve this object, in the case where the discarding of a frame has been performed by the frame reception processing section or by the relay frame reception processing section, or in the case where the loss of a frame has occurred within the relay frame reception processing section, the contents of the discarded or lost frame are reported to the frame relay trace control section. The frame relay trace control section is made to set within the trace area only the contents and the discard factors of frames that have been discarded or lost.