Google and others have published several whitepapers showing benchmarks where tuning tcp/ip on servers can really help web browsing performance.
One of these important tweaks is known as IW10 which improves the tcp/ip congestion window by reducing ACKs (initally sending 10 packets instead of only 3) and is enabled by increasing initcwnd and initrwnd.
Unfortunately those on CentOS (one of the most popular linux production distributions) were not able to take advantage of this – until this weekend when CentOS 6.4 was shipped.
CentOS 6.3 could change initcwnd but NOT initrwnd (RWIN) which requires a kernel > 2.6.33
CentOS 6.4 is 2.6.32-358.0.1.el6 (Red Hat 4.4.7-3) so the feature has been backported