Evaluation of the Delivery QoS Characteristics of Gigabit Ethernet Switches

The event selection system for ATLAS1 is designed to perform real-time image processing on particle collision data equivalent to 2 TB/s. This data is ltered by a multi-level architecture, resulting in 200 GB/s of data analysed by a distributed system consisting of several thousand PCs and switches. As part of our ongoing work on this system, we performed tests on several Gigabit Ethernet switches manufactured by market leaders, using our custom-built test equipment. We analysed the implications of running network devices at, and just beyond, saturation while de-ploying service dierentiation mechanisms. We quantied the quality degradation that trac \ud ows experienced when passing through switches. We focused on emergent properties in saturation, including fairness and delity to expectations. We dis-cuss the ideals for switch behaviour and compare them against the ob-served behaviour of real implementations of dierentiation mechanisms in switches. This creates a generic benchmark, which is independent of the switch internals