investigate what values we have to set for net.ipv4.tcp_{r,w}mem

[aimxhaisse]

This is tricky because:

• it depends on the kernel version (we don't have the same behavior between 3.2.34 and 3.17)
• it can have unexpected side effects

This ticket is not well defined, it depends on what we find, maybe its right place is in the kernel configurations, or in the initrd.

[moul]

I think we should configure this in the initrd with the best values depending on the kernel version and the server type (C1 vs C2 vs...)

Then, the user can override this setting in /etc/sysctl*