Recent kernels already have initcwnd and initrwnd set to 10. Since 2.6.38 or so. If you're using recent kernels (any 3.x), manually setting those to 10 won't change anything.
Somewhere in the early 2.6.3x, I think around .32 or .33, had the two patches to allow setting initcwnd and initrwnd as you demonstrate.
Somewhere in 2.6.35 or 2.6.36 era, initrwnd was changed to 10. Later, around 2.6.38, initcwnd was changed to 10.
I've seen people claim that certain web accelerators use an initcwnd more like 20 to 40.
CentOS 6.2 (the most recent version of a very popular server linux) is using 2.6.32
You can change initcwnd on CentOS 6.2 but not initrwnd. And it defaults to 3
People can check their server kernel version with
uname -a
Servers that appear to be at 20 or especially 40 might just be setting the buffers to match the maximum client side window (which is what Microsoft appears to do on their servers).
Somewhere in the early 2.6.3x, I think around .32 or .33, had the two patches to allow setting initcwnd and initrwnd as you demonstrate.
Somewhere in 2.6.35 or 2.6.36 era, initrwnd was changed to 10. Later, around 2.6.38, initcwnd was changed to 10.
I've seen people claim that certain web accelerators use an initcwnd more like 20 to 40.