Nortel BSR222, Configuration, Page: 155 / 451

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Nortel Business Secure Router 222 Configuration — Basics
Chapter 10
Firewalls
This chapter gives some background information on firewalls and introduces the
Business Secure Router firewall.
Firewall overview
Originally, the term firewall referred to a construction technique designed to
prevent the spread of fire from one room to another. The networking term firewall
is a system or group of systems that enforces an access control policy between two
networks. It can also be defined as a mechanism used to protect a trusted network
from an untrusted network. Of course, firewalls cannot solve every security
problem. A firewall is one
of the mechanisms used to establish a network security
perimeter in support of a network security policy. It must never be the only
mechanism or method employed. For a firewall to guard effectively, you must
design and deploy it appropriately. This requires integrating the firewall into a
broad information security policy. In addition, specific policies must be
implemented within the firewall itself.
Types of firewalls
There are three main types of firewalls:
1
Packet Filtering firewalls
2 Application level firewalls
3
Stateful Inspection firewalls