PRTG Traffic Grapher 

PRTG Traffic Grapher is an easy-to-use software for monitoring and classifying bandwidth traffic usage. It provides system administrators with live readings and long-term usage trends for their network devices. The most common usage is bandwidth management, but you can also monitor many other aspects of your network like memory and CPU utilizations. With PRTG Traffic Grapher you will receive bandwidth and network usage data that helps to optimize the efficiency of your network. Understanding bandwidth traffic and resource consumption is the key to better network management: