Performance Evaluation of the CMS DAQ System Using Simulations

The data acquisition system of the Compact Muon Solenoid ( CMS) experiment must run at the very high trigger rates expected at the LHC. A 512x512 data switch with an aggregate bandwidth of 500 Gb/s is planned as the core of the event builder, which will feed events in at least two stages to the computing farm running the post level-1 triggers in software. Currently small scale hardware setups are built to test various hardware architectures. In order to see how the test bed results apply to the full scale system simulation activities have started.This paper describes the modular discrete event simulation developed for the CMS data acquisition system. Module interfaces are defined as sets of messages, represented as objects that know how to send themselves to the correct destination modules. Implementation was done in C++ with the underlying event scheduler from the CNCL class library. Results of first simulation runs are presented and discussed.