Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS

High energy physics data filtering (application)

Modern high energy physics experiments use multilevel trigger systems to select very rare (10E-13) events with interesting physics phenomena, subject for further studies. Performance of the third level of the triggering system for the ATLAS experiment at the LHC collider at CERN, which will generate over 40 millions interactions per second, depends on complex analysis programs executed on ordinary PCs. Current estimate soars for 3500 processors necessary to perform the selection process.

Some of these processors can be sought for in remote locations providing good connection is available. Using custom designed measurement system, based on programmable 1Gbps Network Interface Cards (NICs) and the Global Positioning System (GPS), we demonstrated that the long haul connection between CERN-Geneva-Switzerland and Cyfronet-Krakow-Poland using pan-european GEANT network and Polish National Research and Education Network (NREN) Pionier can provide almost 1 Gbps throughput.

The network QoS measurements were followed by integration phase where initial merge of the CrossGrid services and the ATLAS High Level Trigger system (HLT) was implemented. Thus we demonstrated a possible solution to cater deficit of the CPU power for the HLT system for ATLAS. The first results however, in terms of achieved throughput, were much below the expected limit with a clear indication of transmission bottleneck being the TCP/IP protocol and request-response type of communication implemented in the HLT system. The latter is especially sensitive to long latencies observed in the long distances.

We plan to continue our research using the CrossGrid testbed. The work did so far can become a foundation for continuation studies leading to design of mechanisms aimed at improving the long haul transfers of large data in real time.

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Instytut Fizyki Jadrowej Im Henryka Niewodniczanskiego W Krakowie
Radzikowskiego 152
31-342 Krakow
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