Protocol-Independent Event Building Evaluator for the LHCb DAQ System

The Data Acquisition (DAQ) system of LHCb is a complex real-time system. It will be upgraded to provide LHCb with an all-software, trigger-free readout starting from 2020. Consequently, more CPU power in the form of servers will be needed and the DAQ network will grow to a capacity of 40 Tbps. A PC-based readout system would receive data incoming from the detector, which would then be scattered across builder nodes, and further distributed to a computing farm for data filtering. The design bandwidth of such a DAQ system requires rates as high as 400 Gbps single-duplex per node. These builder nodes will be connected with cost-effective, high-bandwidth data-centre switches in order to minimize the system cost. The behaviour of such an Event Building network can of course be studied in simulation but experience tells us that it is crucial to test, in particular to find out limitations in the switches themselves and to which extent various Event Building protocols can mitigate these limitations. We present a protocol, topology and transport independent emulation software named DAQ Protocol-Independent Performance Evaluator (DAQPIPE). It allows us to test different communication architectures, such as push or pull, with regards to the initiator of the communication. Different topologies and transport protocols can also be tested. We present throughput and stress tests on an InfiniBand FDR multi-rail based LAN network setup, with a focus on the network performance. Large tests on the current system LHCb DAQ are shown to demonstrate the scalability of DAQPIPE itself and its capability to be deployed on any kind of large, tightly interconnected network to test its suitability for Event Building applications.