Network simulation of a 40 MHz event building system for the LHCb experiment

The LHCb experiment will be upgraded in 2021, and a new triggerless readout system will be implemented. In the upgraded system, both Event Building (EB) and event selection will be performed in software for every collision produced in every bunch-crossing of the LHC. In order to transport the full data rate of 32 Tb/s, we will use state of the art off-the-shelf network technologies, e.g. InfiniBand EDR. The full event building system will require around 500 nodes interconnected together via a non-blocking topology. Because of the size of the system it is challenging to test at production scale, before the actual procurement. Therefore, we resort to network simulations as a powerful tool for finding the optimal configuration. We developed an accurate low-level description of an InfiniBand based network with event building like traffic. We will present a full-scale simulation of a possible implementation of the LHCb EB network.