IPerf is a tool which allows you to benchmark your connectivity.
It can be run on either client of server mode. Server mode you'll probably only need if you're testing an intra VPN site.
Client mode is more common but you need a reliable public server to be able to use this. Currently the official IPerf webpage hosts a short list of public servers https://iperf.fr/iperf-servers.php. Some do not work so try a different server if you get an error back. You might also try unofficial servers but the location and availability is likely to change often. Once you have set up the Server address, protocol and port you can start your test.
Mode Server/Client - sets the operational mode
Host address - only visible in client mode defines the target server address
Protocol TCP/UDP - defines the layer 4 protocol to be used for the test
Port - defines the port to be used for the test (default is 5201)
Type Time-limites/Buffer-limites - Define if your test should stop after a specific amount of time as opposite to amount of data transferred.
Time/Bytes limit - Unit for the limit type as defined above
NOTE: unfortunately as per today there are few reachable severs, also it is important to use a server with geographical proximity for accurate result. The example above was run on a 200/12 MB connectivity, as you can see the result is far from accurate. Still this tool can be useful fro intra VPN connectivity.