Difficulties in simulating the Internet

Simulating how the global Internet behaves is an immensely challenging undertaking because of the network´s great heterogeneity and rapid change. The heterogeneity ranges from the individual links that carry the network´s traffic, to the protocols that interoperate over the links, the “mix” of different applications used at a site, and the levels of congestion seen on different links. We discuss two key strategies for developing meaningful simulations in the face of these difficulties: searching for invariants and judiciously exploring the simulation parameter space. We finish with a look at a collaborative effort within the research community to develop a common network simulator