Triggering and event building results using the C104 packet routing chip

The C104 is an asynchronous 32-way dynamic packet routing chip. It has a 264Mbytes/s bi-directional bandwidth and a 1 µsec switching latency. It offers high-density cost- effective commodity communications, which allow large switching networks to be con- structed. Results are presented on the performance of this switching technology within the context of future High Energy Physics level II and level III trigger data traffic patterns

Testing and Modeling Ethernet Switches and Networks for Use in ATLAS High-level Triggers

The ATLAS second level trigger will use a multi-layered LAN network to transfer 5 Gbyte/s detector data from ~1500 buffers to a few hundred processors. A model of the network has been constructed to evaluate its performance. A key component of the network model is a model of an individual switch, reproducing the behavior measured in real devices. A small number of measurable parameters are used to model a variety of commercial Ethernet switches. Using parameters measured on real devices, the impact on the overall network performance is modeled. In the Atlas context, both 100 Mbit and Gigabit Ethernet links are required. A system is described which is capable of characterizing the behavior of commercial switches with the required number of nodes under traffic conditions resembling those to be encountered in the Atlas experiment. Fast Ethernet traffic is provided by a high density, custom built tester based on FPGAs, programmed in Handel-C and VHDL, while the Gigabit Ethernet traffic is generated using Alteon NICs with custom firmware. The system is currently being deployed with 32 100Mbit ports and 16 Gigabit ports, and will be expanded to ~256 nodes of 100 Mbit and ~50 GBE nodes

The ATLAS Data Acquisition and High-Level Trigger: Concept, Design and Status

The Trigger and Data Acquisition system (TDAQ) of the ATLAS experiment at the CERN Large Hadron Collider is based on a multi-level selection process and a hierarchical acquisition tree. The system, consisting of a combination of custom electronics and commercial products from the computing and telecommunication industry, is required to provide an online selection power of 105 and a total throughput in the range of Terabit/sec. This paper introduces the basic system requirements and concepts, describes the architecture of the system, discusses the basic measurements supporting the validity of the design and reports on the actual status of construction and installation

The ATLAS trigger - high-level trigger commissioning and operation during early data taking

The ATLAS experiment is one of the two general-purpose experiments due to start operation soon at the Large Hadron Collider (LHC). The LHC will collide protons at a centre of mass energy of 14~TeV, with a bunch-crossing rate of 40~MHz. The ATLAS three-level trigger will reduce this input rate to match the foreseen offline storage capability of 100-200~Hz. This paper gives an overview of the ATLAS High Level Trigger focusing on the system design and its innovative features. We then present the ATLAS trigger strategy for the initial phase of LHC exploitation. Finally, we report on the valuable experience acquired through in-situ commissioning of the system where simulated events were used to exercise the trigger chain. In particular we show critical quantities such as event processing times, measured in a large-scale HLT farm using a complex trigger menu

Performance of the final Event Builder for the ATLAS Experiment

Event data from proton-proton collisions at the LHC will be selected by the ATLAS experiment in a three level trigger system, which reduces the initial bunch crossing rate of 40 MHz at its first two trigger levels (LVL1+LVL2) to ~3 kHz. At this rate the Event-Builder collects the data from all Read-Out system PCs (ROSs) and provides fully assembled events to the the Event-Filter (EF), which is the third level trigger, to achieve a further rate reduction to ~200 Hz for permanent storage. The Event-Builder is based on a farm of O(100) PCs, interconnected via Gigabit Ethernet to O(150) ROSs. These PCs run Linux and multi-threaded software applications implemented in C++. All the ROSs and one third of the Event-Builder PCs are already installed and commissioned. We report on performance tests on this initial system, which show promising results to reach the final data throughput required for the ATLAS experiment