RWIN Expansion

TCP Auto-Tuning measures the RTT of connections at the beginning and if data is sent. For connections with only received data and no data to send, this measurement can become inaccurate, so the resulting RWIN remains too small. You can easily verify this behavior with a fast Internet connection and high latency, for example a 50Mbit/s connection from Europe to America or a mobile broadband connection.

Results of cFosSpeed RWIN-Expansion-Award 2012

A lot of users don’t get the maximum speed available for their Internet connection. In many cases the TCP Auto-Tuning of Windows 7/ Windows Vista cannot use the full download speed. In other cases the downloading programs are not written for today’s high speed connections. cFosSpeed’s RWIN expansion now accelerates these downloads by dynamically expanding the receive window size of the TCP connection to a value suitable for the current connection. This leads to unexpected speed improvements!
For example, we could double the download speed with Internet Explorer and nearly triple the speed of mobile UMTS downloads.

To demonstrate these dramatic speed improvements, we (with the help of our users) compiled a list of scenarios in which the new cFosSpeed RWIN Expansion achieves these huge speed improvements.