BWMeter is a tiny but powerful broadband/traffic monitor and controller based on WinpkFilter network drivers. It can perform real-time measure and control to any Internet/Network traffic through your computer. Meanwhile, it visually shows them in the way of chart.
Without any doubt, Wireshark (formerly called Ethereal) is currently the world's most famous, foremost free and open source network packets capture & analysis tool. Its appearance puts an end to the future of all similar business software.