Patent ID: 7486613

Claim:
A protection-switching apparatus in an asynchronous transfer mode system with ring topology, comprising: an optical network unit for detecting trouble and abnormal states of an optical path connected to the optical network unit itself, the asynchronous transfer mode system using an auto protection switching cell, with a virtual channel identifier field, to store data of an optical path having abnormal or normal states when the asynchronous transfer mode system, transmitting an asynchronous transfer mode cell simultaneously in two directions, is in a ring shape with a host digital terminal and a plurality of optical network units, each of the optical network units comprising: a hardware unit; a software unit, the hardware unit and the software unit in combination generating and transmitting the auto protection switching cell; and an auto protection switching register, to which copying of the virtual channel identifier field of the auto protection switching cell is performed by the hardware unit, and from which the virtual channel identifier field is read and set by the software unit; wherein the optical network unit performs a protection-switching function by receiving the asynchronous transfer mode cell from a first direction opposite to a second direction of the optical path having the trouble; said software unit of the optical network unit inserting node identification data of the optical network unit into the auto protection switching register of the optical path of normal states; and said hardware unit and said software unit of the optical network unit in combination generating the auto protection switching cell by performing copying of contents of the auto protection switching register to the virtual channel identifier field of the auto protection switching cell, and transmitting the auto protection switching cell in a direction the same as a direction of an optical path having the abnormal states.