The ability to use a visualisation tool to steer large simulations provides innovative and novel usage scenarios, e.g. the ability to use new algorithms for the computation of free energy profiles along a nanopore [1]. However, we find that the performance of interactive simulations is sensitive to the quality of service of the network with variable latency and packet loss in particular having a detrimental effect. The use of dedicated networks (provisioned in this case as a circuit-switched, point-to-point optical lightpath or lambda) can lead to significant (50% or more) performance enhancement. When running on say 128 or 256 processors of a high-end supercomputer this saving has a significant value. We perform experiments to understand the impact of network characteristics on the performance of a large parallel classical molecular dynamics simulation when coupled interactively to a remote visualisation tool. This paper discusses the experiments performed and presents the results from the systematic studies.