bmon

The bmon utility is an application to view network bandwidth usage with a Linux system.  With a Debian-based system, the following command should install the application.

sudo apt-get install bmon

To launch the utility, simply use the command bmon.  The default is to display bytes per second.  To display bits per second, launch the application with a -b switch.

https://www.networkworld.com/article/3447936/viewing-network-bandwidth-usage-with-bmon.html