Abstract The CERN Data Centre is the heart of CERN’s entire scientific, administrative, and computing infrastructure. All IT services use equipment located in the data centre. Because of its significant role, the performance of the devices deployed in the network is essential for providing high quality network services. In order to provide a reliable and high-performance network the performance and limitations of each device have to be checked. The Flow Visualizer project consists in developing a flow visualization framework, which enables real-time monitoring of the flows generated by a distributed traffic generator and allows visualizing the monitored information at different levels of detail.