CERN from collisions to network collaborations

CERN, the European Organization for Nuclear Research, is exploring fundamental physics, finding out what the Universe is made of and how it works. The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions. CERN is not an isolated laboratory, but rather a focus for an extensive community that now includes about 60 countries and about 8000 scientists. These scientists typically work remotely from universities and national laboratories in their home countries. This workshop will open with an overview of CERN and explore the impact of optical technologies on the full infrastructure that supports its scientific programme. Starting with the accelerator itself, we move on to the experiments, massive detectors with millions of channels of electronics which are read-out by high-speed data acquisition systems capable of handling data flows of 1 petabyte per second. Following data-reduction, data is transferred over a local area network to be written to mass storage systems at the computer centre, the hub of CERN's network infrastructure. The CERN campus network has more than 50000 active user devices interconnected by 10000 km of cables and fibres, with more than 2500 switches and routers and a potential of 4.8 terabit per second throughput. This campus network will be described, together with the challenges associated to its operation. To conclude, the data processing flow for LHC will be presented. It is assured by the World-wide LHC Computing Grid (WLCG) which provides a distributed computing platform aggregating the resources of nearly 150 centres around the globe. This unique and novel tiered model, where CERN is tier-0 linked to 11 tier-1's and many tier-2s, is supported by a high-performance Optical Private Network which provides 140 gigabit per second connectivity to external networks and ensures access to LHC data for physicists around the world.