NETWORK SYSTEM

摘要

A link control function unit 506 of a device 500 notifies a counterpart device 600 of a line in which a link disconnection occurs among lines 508 to 510 and L500 terminated at line terminals 501 to 503 or a lower stage line terminal 504 of the self device 500 and the cause of the link disconnection is not a forcible closure of a line terminal of the self device. Further, the link control function unit 506 does not forcibly close the lower stage line terminal 504 of the self device 500 if a line in which a link disconnection occurs, notified from the counterpart device 600, is a line terminated at a lower stage line terminal 604 of the counterpart device 600.