The Jev model's behavior comes from three components. The arrival process describes how work shows up over time, including its average rate and how bursty it is. The service process describes how much the system can clear and how variable that clearing is. The scheduling rule decides which waiting item is served next and how work is shared. Each component contributes a different kind of variability, and together they determine how close the system runs to its capacity.
The Jev Model: An Intuitive Overview