If you are a Network Administrator with little knowledge in Network Protocols and IPtables, don't worry you can also controll your network traffic with a simple tool named wondershaper.
sudo apt-get install wondershaper
official site : http://lartc.org/wondershaper/
Readme files in /usr/share/doc/wondershaper
$ifconfig this will help you to find the network interface (eth0, eth1 or wifi0 etc..)
Now
$sudo wondershaper eth0 downspeed upspeed
eg: sudo wonderspeed 128 64
To Disable this settings
$sudo wondershaper clear eth0
make these connection settings permanent by editing /etc/network/interfaces file :
$ sudo gedit /etc/network/interfaces and add the following lines
up /sbin/wondershaper eth0 downspeed upspeed
down /sbin/wondershaper clear eth0