Preparing for the Next WLCG Network Data Challenge: Site Network Monitoring

During the first WLCG Network Data Challenge in fall of 2021 (DC21) we identified shortcomings in the monitoring that impeded our ability to fully understand the results collected during the data challenge. One of the simplest missing components was site-specific network information, especially information about traffic entering and leaving any of the participating sites. Without this information, it is very difficult to understand which sites are experiencing bottlenecks or might be misconfigured or under-used based on their capacity. The WLCG Monitoring Task Force, formed at the end of 2021, was tasked with three main work areas, one of which was site network monitoring. We will describe the work carried out by the task force to enhance our knowledge of network use for WLCG by enabling site network documentation and use, the status of the deployment, and the implications for the next data challenge.