Cacti is an open-source, network monitoring and graphing tool, that uses the industry-standard data logging tool, RRDtool. Cacti polls services at predetermined intervals and graphs the resulting data. It can graph time-series data of metrics such as CPU load and network bandwidth utilization. It can monitor network traffic by polling a network switch or router interface via Simple Network Management Protocol (SNMP).
The front end can handle multiple users, each with their own graph so it is sometimes used by web hosting providers to display bandwidth statistics for their clients.