PRTG - Paessler Router Traffic Grapher is a boon to network administrators for managing and optimizing networks.
    Network administrators can perfectly and precisely gather all information related to resource consumption and bandwidth. This application has many uses including providing detailed information related to bandwidth and server performance. You can avoid costs involved due to bottlenecks or extra load. All data traffic information is monitored in order to determine usage, CPU and memory utilization as well as bandwidth information. This is reported in the form of comprehensive graphs and tables. All data gathered is stored on an internal database and can be displayed in graphical and tabular formats.
    It works on all Windows versions and supports most network products. The common methods used are SNMP, Packet Sniffing and Net Flow.