Firewall
252
8.2
What is a Firewall?
BAT54-Rail/F..
Release
7.54
06/08
8.2 What is a Firewall?
The term “Firewall” is interpreted very differently. We want to define at this
point the meaning of “Firewall” within the boundaries of this user manual con-
figuration
.
The Firewall can consist of hard and/or software components:
D In pure hardware systems the Firewall software often runs on a propri-
etary operating system.
D The Firewall software can also run on a conventional workstation, which
is dedicated to this task under Linux, Unix or Windows.
D As a third and frequently used alternative, the Firewall software runs di-
rectly within the router, which connects the LAN to the Internet.
In the following sections we only look at the Firewall in a router.
Note: The functions “Intrusion Detection” and “DoS protection“ are part of the
content of a Firewall in some applications. The BAT contains these func-
tions also, but they are realised as separate modules beside the Firewall.
Further information can be found in the section ’Intrusion Detection’
→ page 302 and ’Denial of Service’ → page 304.
8.2.1 Tasks of a Firewall
U Checking data packets
How does the Firewall supervises the data traffic? The Firewall works in prin-
ciple like a door keeper for data packets: Each packet will be checked, wheth-
er it may pass the door of the network (Firewall) in the desired direction or
not. For such a checking different criteria are used, in common language of
Firewalls called “rules” or “guidelines”. Depending on the kind of information,
which are used for creation of the rules and which are checked during the op-
eration of the Firewall, one distinguishes different types of Firewalls.
A Firewall is a compilation of components, which monitors at a central
place the data exchange between two networks. Mostly the Firewall mon-
itors the data exchange between an internal, local network (LAN), and an
external network like the Internet.
To Next Page
Loading...
Need help?
General
