ATLAS is one of the two general purpose detectors proposed for the Large Hadron Collider at CERN. The second level trigger will receive events at rates up to 100 kHz and must reduce this by around two orders of magnitude. The second level trigger architecture chosen for this study is called the local-global model. This architecture has four local processor farms, one per sub-detector, each connected by its own network to data buffers. The local processors are connected via another network to a global processor farm where results from the local processing farms are collected and evaluated.

The architecture has been emulated on two large hardware platforms, Macramé and GPIMMD. Both platforms use DS-Link technology. Improvements to the running of these platforms by designing, implementing and testing a diagnostic software utility called Net--probe are described. This utility facilitates hardware. board and system-setup debugging.

Macramé is a test-bed for studying network traffic patterns. It consists of C104 routers and specially-designed traffic-generating nodes and timing nodes. These components can be configured into a variety of topologies.

Each of the five networks were mapped to Macramé one at a time and the traffic patterns expected in each case were run through the network. The results obtained are presented and interpreted.

A process model of the second level trigger was developed and implemented on GPMIMD, a general purpose parallel computer, and is described together with benchmark results of the components. Results from running this model with both test and detector specific data are presented.