Here goes my default Linux 2.6 network stack tweaks

cat /etc/sysctl.conf

[...]

net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.ipv4.tcp_rmem = 4096 87380 16777216
net.ipv4.tcp_wmem = 4096 65536 16777216
net.ipv4.tcp_window_scaling=1
net.ipv4.tcp_timestamps=1
net.ipv4.tcp_sack=1