An apparatus for the rental or sale, and distribution of digital content via the Internet. The degradation in network performance caused by each failure is quantified based on user-defined sets of thresholds of degradation severity for each performance measure. The front-end and back-end interfaces convert electrical signals destined for transmission over the pair into optical signals prior to transmission. The plunger assembly further defines a plurality of cam-like members that each engage and cooperate with a respective helical path of steps formed on the inner wall of the syringe body to provide stepwise movement of the plunger and, in turn, precise metering of the substance dispensed therefrom.