The Computing Model Simulation Program, ModNet, developed at CERN, allows us to model the expected WAN configuration during LHC data taking, and the expected tasks distribution amongst the collaborating institutes. In the screen shot shown, a simulation of a distributed event reconstruction task is underway. The graph window indicates the number of processors (CPUs) required at Caltech to accomodate the instantaneous job load. Similar graphs can be plotted for network traffic on the links between the institutes. ModNet will be used in the context of the Caltech/CERN/HP project to model strategies for replicating the event data between CERN and remote institutes, and in developing cost algorithms for optimising the location of tasks that analyse the data.