A firewall located at a network gateway server, that protects the resources of a private network from users from other networks. An enterprise with an intranet that allows its workers access to the wider Internet installs a firewall to prevent outsiders from accessing its own private data resources and for controlling what outside resources its own users have access to.

It may be a hardware device or a software program running on a secure host computer. In either case, it must have at least two network interfaces, one for the network it is intended to protect, and one for the network it is exposed to. A network firewall sits at the junction point or gateway between the two networks, usually a private network and a public network such as the Internet.

Basically, a firewall working closely with a router program, examines each network packet to determine whether to forward it toward its destination. A firewall also includes or works with a proxy server that makes network requests on behalf of workstation users. A firewall is often installed in a specially designated computer separate from the rest of the network so that no incoming request can get directly at private network resources.

How is a Proxy Server different from a Firewall?

The functions of proxy, firewall, and caching can be in separate server programs or combined into a single package.  Different server programs can be located on different computers.  A typical firewall only affects traffic that is deems inappropriate, or needs to be forwarded – it leaves all other traffic alone.  A typical proxy server will affect all traffic in order to improve response time and forward requests through the firewall. [Top]