There are many Open Source bandwidth monitoring tools available FREE. These tools also provides for alerts and limiting the bandwidth usage. They also provides the network performance reports to help in monitoring the network health. Some of the tools available are:
It monitors bandwidth in real time.
Check the bandwidth every half second.
Facility to set critical and warning thresholds to get informed when the usage is out of limits.
It is useful in Network troubleshooting, development of communication and software protocol, analysis and education.
This is useful and easy to use when testing the network performance having GUI.
It provides numerical values of both upload and download speeds and represents them graphically also for ease of understanding.
It records bandwidth usage also.
Generates daily, weekly and monthly bandwidth usage reports.
Evaluates LAN network, VPN connection and Internet Network on computers.
It supports variety of network interfaces.
Gives alert when network activity exceeds a certain level. It ensures you never exceeds bandwidth limits.
It monitors network speed and the upload and download data on any network interface.
It keeps the data and reports it.
Other bandwidth monitoring tools to name are:
Internet Bandwidth Monitor (IBM)