A reconfigurable wiring concentrator in hierarchical star with dual-ring LAN

The in-house information communication network using local area network (LAN) is required to cope flexibly with the expansion/modification of the system and to avoid the system-down in the generation of a fault by detaching the fault domain. This paper considers the star-ring LAN with the ring spurs and a dual ring. It proposes also the structure and control of the wiring concentrator of ring LAN with the dedicated automatic reconfiguration control by the ring spur bypass and the ring wrapback. Since the ring contains both the ordinary terminals and WC, the reconfiguration-dedicated medium access control (MAC) frame is introduced anew and can be sent only by wiring concentration (WC), making unnecessary the specification modification of the MAC layer of the terminal. The WC which handles the localization and detachment of the fault point is determined by this mechanism. The test ring is automatically expanded from the local ring in WC to the ring containing the ring spur and the ring containing the dual ring successively by testing the conductivity. Using WC, a ring LAN system with the automatic ring degeneration/expansion function can be realized, while providing the terminal with the function of connection/detachment/shift on LAN (hot-pluggability). The time required for reconfiguration by the proposed reconfiguration control is evaluated by summing up the times for the major control steps and by experimental examination.