Computer modeling the ATLAS trigger/DAQ system performance

In this paper, simulation ("computer modeling") of the Trigger/data acquisition (DAQ) system of the ATLAS experiment at the LHC accelerator is discussed. The system will consist of a few thousand end nodes, which are interconnected by a large Ethernet network. The nodes will run various applications under the Linux operating system (OS). Predictions for the latency, throughput and queue development in various places have been obtained. Results are presented with respect to the application of traffic shaping to reduce the probability of possible frame loss (which may cause severe performance degradation).