Patent ID: 6877105

Claim:
A method for sending a notice of failure detection in a system connecting first and second network interfaces incorporated in first and second apparatuses by a line including a transmission side transfer path and a reception side transfer path, said system performing data communication between said first and second apparatuses via said line, wherein: said first and second network interfaces periodically transmit a utilizability signal representing normality of said line or an own apparatus to said transmission side transfer path; said first apparatus judges an occurrence of a failure when it cannot detect said utilizability signal from said second network interface of said second apparatus as a mating apparatus for a predetermined period from said reception side transfer path; said first network interface of said first apparatus stops transmitting said utilizabiltiy signal to be transmitted to said network interface of said second apparatus, and thereby reports the occurrence of the failure to said second apparatus; when said first network interface of said first apparatus stops transmitting said utilizability signal, said first apparatus starts transmitting periodically said utilizability signal to said reception side transfer path after passage of a predetermined period, and monitors thereafter whether or not said utilizability signal can be detected on said reception side transfer path; said first apparatus judges that the failure is not yet restored when said first apparatus cannot detect said utilizability signal for the predetermined period on said reception side transfer path, and stops again transmitting said utilizability signal that has been transmitted periodically to said transmission side transfer path; and when said first apparatus can detect continuously said utilizability signal on said reception side transfer path for a predetermined period, on the other hand, said first apparatus judges that the failure is restored, continues thereafter to transmit periodically said utilizability signal, and starts again the data communication.