Patent ID: 6023455
Filing Date: 2000-02-08
Classification: H04L,H04Q

Abstract:
A loopback cell control system comprising:a plurality of ATM apparatuses, each adapted to generate information about a loopback as a loopback cell according to a predetermined format of an ATM cell, and transmitting the loopback cell while controlling transmission/reception, passing, and returning of the cell; anda plurality of forward paths and a plurality of backward paths as transmission paths through which said ATM apparatuses are cascaded, said ATM apparatuses and said transmission paths constituting an ATM network,said loopback cell control system being adapted to perform a loopback test by circulating the loopback cell through a predetermined route in said ATM netwvork once, andeach of said ATM apparatuses including:time managing means for counting the current time, measuring an elapsed time between the transmission of the loopback cell and the reception thereof, and notifyg a timeout when the elapsed time exceeds a predetermined reference time;loopback control means constituted by transmission control means for, when the loopback cell is transmitted at a start point, transmitting the loopback cell to one of said forward paths and acquiring a transmission time from said time managing means, turning control means for, when the loopback cell is received at a turning point, writing turning time in the received loopback cell and transmitting the cell as a backward loopback cell to one of the backward paths, relay control means for, when the loopback cell and the backward loopback cell are received at a passing point, allowing the received loopback cell and the received backward loopback cell to pass therethrough, and reception control means for, when the backward loopback cell is received at an end point, checking validity of the received backward loopback cell first, then acquiring a reception time from said time managing means, and reading the turning time written in the backward loopback cell; anddelay measuring means for, when the backward loopback cell is received at an end point, calculating a delay time in each of said forward and backward paths on the basis of the transmission time, the turning time, and the reception time notified from said loopback control means, and outputting an alarm signal when each of the calculated delay times is longer than a predetermined reference time.