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An implementation of a reliable message broadcast for the CMS event builder system

Ichiro Suzuki

Speaker: Ichiro Suzuki

  The CMS DAQ system utilizes a dedicated network to distribute commands to all the DAQ units responsible for reading out the detector Front-Ends. This network must have low latency ($\sim ms$) since it must carry the signals indicating the presence of a new event (maximum rate of 100 kHz) in the Front-Ends which in turn do not have deep buffering capability. A reliable broadcast functionality is necessary for this. Although many implementations of reliable broadcast/multicast protocols exist and are available, the requirements of total reliability and short latency have kept us from using any of these. A NACK-based reliable broadcast protocol with Forward-Error correction was implemented on a system of PCs connected FastEthernet along with software for the CMS event builder system development. The implementation was tested in various system configurations and proved its technical feasibility. Several modifications to increase the system performance and stability are also introduced and are described here.

Presentation:  Adobe Acrobat pdf Short Paper:  Adobe Acrobat pdf 

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