Abstract— In order to efficiently use Grid resources, users or middlewares must use some network information, and in particular some knowledge of the platform network. As such knowledge is usually not available, one must use tools which automatically build a topological network model through some measurements. Our aim is to define a methodology to assess the quality of these network model building tools, and to apply this methodology to representatives of the main classes of model builders. Using this approach, we show that none of the main existing techniques build models that enable to accurately predict the running time of simple application kernels for actual platforms.