sudo gedit /etc/sysctl.conf
add the text at the bottom given here
http://ubuntumanual.org/posts/10/how-to-increase-internet-speed-in-ubuntu
type in at the terminal
~/Downloads$ sudo sysctl -p
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_no_metrics_save = 1
net.ipv4.tcp_moderate_rcvbuf = 1
net.core.netdev_max_backlog = 2500
net.ipv4.tcp_sack = 0
net.ipv4.tcp_window_scaling = 1
http://ubuntumanual.org/posts/10/how-to-increase-internet-speed-in-ubuntu
http://www.ubuntugeek.com/how-to-change-mtu-maximum-transmission-unit-of-network-interface-in-ubuntu-linux.html
frankly it did not really work on my system (April 2011) that article was written in 2008 so not sure if that is the reason
http://www.bufferbloat.net/projects/bloat/wiki/Linux_Tips