Busy hour
Busy hour: In a communications system, the sliding 60-minute period during which occurs the maximum total traffic load in a given 24-hour period.
The busy hour is determined by fitting a horizontal line segment equivalent to one hour under the traffic load curve about the peak load point.
If the service time interval is less than 60 minutes, the busy hour is the 60-minute interval that contains the service timer interval.
In cases where more than one busy hour occurs in a 24-hour period, i.e., when saturation occurs, the busy hour or hours most applicable to the particular situation are used. Synonym peak busy hour.
The idea behind the busy hour is that the traffic is not leveled throughout the day. There are some peak hours in a day which are busy and have more traffic than normal hours. During these hours traffic is at maximum level. The users will receive Grade of Services according to the traffic measured in those hours.
References
This article incorporates public domain material from the General Services Administration document "Federal Standard 1037C" (in support of MIL-STD-188).