The CMS Orbit Builder for the HL-LHC at CERN

The Compact Muon Solenoid (CMS) experiment at CERN incorporates one of the highest throughput data acquisition systems in the world and is expected to increase its throughput by more than a factor of ten for High-Luminosity phase of Large Hadron Collider (HL-LHC). To achieve this goal, the system will be upgraded in most of its components. Among them, the event builder software, in charge of assembling all the data read out from the different sub-detectors, is planned to be modified from a single event builder to an orbit builder that assembles multiple events at the same time. The throughput of the event builder will be increased from the current 1.6 Tb/s to 51 Tb/s for the HL-LHC orbit builder. This paper presents preliminary network transfer studies in preparation for the upgrade. The key conceptual characteristics are discussed, concerning differences between the CMS event builder in Run 3 and the CMS Orbit Builder for the HL-LHC. For the feasibility studies, a pipestream benchmark, mimicking event-builder-like traffic has been developed. Preliminary performance tests and results are discussed.