Abstract: A Local Area Network (LAN) Switch includes conventional switching functions and integrated Remote Monitoring (RMON) Universal Feature Card (UFC). The UFC allows simultaneously statistically monitoring the traffic on all ports, 100% monitoring of the traffic on one port, and monitoring the internal LAN Switch switching fabric to obtain RMON statistics about the operation of networks attached to the LAN Switch.

Abstract: Controller triple modular redundancy is substantially achieved and reliability improved in a system having duplicate controllers that serve peripheral units. Both controllers detect suspected faults in itself and in the other controller. A peripheral unit that suspects a faulty active controller requests a switch of the active controller. A voting circuit processes votes from the controllers and the active controller switch signal from the peripheral units to select the active controller. The signaling paths between the controllers used to convey votes and active controller information are duplicated. The signals on these signaling paths convey information by using oscillating signals of different frequencies.

Abstract: Controller triple modular redundancy is substantially achieved and reliability improved in a system having duplicate controllers that serve peripheral units. Both controllers detect suspected faults in itself and in the other controller. A peripheral unit that suspects a faulty active controller requests a switch of the active controller. A voting circuit processes votes from the controllers and the active controller switch signal from the peripheral units to select the active controller. The signaling paths between the controllers used to convey votes and active controller information are duplicated. The signals on these signaling paths convey information by using oscillating signals of different frequencies.