Patent ID: 8638673

Claim:
A communication path monitoring method, wherein: a first transmission apparatus and a second transmission apparatus recognize a working path used for transmitting a client signal and a back-up path group other than the working path from a plurality of communication paths between the both apparatuses; the first transmission apparatus selects a measurement path from the back-up path group, and transmits a test signal to the second transmission apparatus via the measurement path; the second transmission apparatus measures a communication quality by using the test signal from the first transmission apparatus, records data of the measurement, and transmits a test signal containing the recorded measurement data to the first transmission apparatus via the measurement path; and the first transmission apparatus records the measurement data contained in the test signal from the second transmission apparatus, measures a communication quality by using the test signal from the second transmission apparatus, records the measurement data, selects a new measurement path from the back-up path group, and transmits a test signal containing the recorded measurement data to the second transmission apparatus via the new measurement path.