in computer network research, network simulation is a technique whereby a software program models the behavior of a network by calculating the interaction between the different network entities (routers, switches, nodes, access points, links etc.). most simulators use discrete event simulation - the modeling of systems in which state variables change at discrete points in time. the behavior of the network and the various applications and services it supports can then be observed in a test lab; various attributes of the environment can also be modified in a controlled manner to assess how the network / protocols would behave under different conditions.