A networking firewall is a logical barrier designed to prevent unauthorized or unwanted communications between sections of a computer network. Linux-based firewalls besides being highly customizable and versatile are also robust, inexpensive, and reliable. The two things needed to build firewalls and QoS with Linux are two packages named netfilter and iproute. While netfilter is a packet-filtering framework included in the Linux kernels and , iproute is a package containing a few utilities that allow Linux users to do advanced routing and traffic shaping
