Internet Traffic Periodicities and Oscillations by Reginald D. Smith

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User traffic driven periodicities were the first known and most easily recognized. The first discovered and most well-known periodicity is the 24 hour diurnal cycle and its companion cycle of 12 hours. These cycles have been known for decades and reported as early as 1980 and again in 1991 as well as in many subsequent studies. This obviously refers to the 24 hour work-day and its 12-hour second harmonic as well as activity from around the globe. The other major periodicity from human behavior is the week with a period of 7 days and a second harmonic at 3.5 days and barely perceptible third harmonic at 2.3 days.