Use Iperf to Measure Network Throughput (Bandwidth)

Iperf
Iperf was developed by NLANR/DAST as a modern alternative for measuring maximum TCP and UDP bandwidth performance. Iperf allows the tuning of various parameters and UDP characteristics. Iperf reports bandwidth, delay jitter, datagram loss.

Install iperf on Windows - just download, unzip and run iperf.exe.

Install iperf on Ubuntu:

sudo apt-get install iperf

Iperf supports several options, but generally you would run it on one device as a "server" and another as a "client."

To launch iperf in server mode just enter iperf -s at the terminal.  It will report, "Server listening on TCP port 5001. . ."

From another system launch iperf in client mode with iperf -c <server IP>. By default Iperf will run a 10 second test and report amount of data transferred and bandwidth speed.

Note: Iperf can be used to test LAN speeds as well as over the Internet.

Download Iperf and get more information from SourceForge.