INTER-LAN CONNECTION SYSTEM AND ITS ALARM TRANSFER SYSTEM

摘要

PROBLEM TO BE SOLVED: To effectively announce a fault in a user station or a repeating place to an enterprise when a user LAN is connected to the wide-area LAN of a communication enterprise by an optical fiber transmission line via the repeating site. SOLUTION: When a link disconnection or a power source interruption is detected in the transmission line, an optical conversion repeater 50 in the user station and first and second repeaters 80 and 90 in a repeater unit 70 generate an alarm packet which is shorter than the packet length of an 'Ethernet(R)' frame and transfer it to an optical conversion bridge 60 in the enterprise. In this case, the first and second repeaters 80 and 90 impart and transmit an identifying code expressing the packet's passage through the repeaters 80 and 90. The optical conversion bridge determines from which device each alarm packet is transferred, dicides its alarm kind and outputs the result to an external part. The alarm packet is shorter than a normal frame and abrogated by an MAC switch so that the alarm packet is not drained to the wide area LAN.