A scheduler allowing high-speed scheduling scalable with the number of input and output ports of a crosspoint switch and suppressed unfairness among inputs is disclosed. The value of a current to be supplied to the light-emitting element for edge detection is determined in the following manner. Data that is accessed more frequently can be migrated toward higher performance storage tiers while data that is accessed less frequently can be migrated towards lower performance storage tiers. In an exemplary embodiment, the present invention includes a network management system and method with a plurality of network elements operating a management agent communicatively coupled to an element manager which in turn is communicatively coupled to another element manager, a network management system, an operations support system, or the like. The outer bushing is connected to the base and mounted on the elevation adjusting mechanism.