B2B Integration : A Practical Guide to Collaborative E-commerce

Firewall
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Screening router
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Internet Security 303
Proxies
Figure 10.12. — Firewall between internal LAN and the internet
A firewall insulates a company's internal networks from the outside
world. It is the first line of defense between the internal LAN and the
Internet (see Figure 10.12). It works by enforcing an access control
policy to and from the private network. All messages entering or
leaving the Intranet pass through the firewall, which examines each
message and blocks those not meeting the specified security criteria.
Firewalls can be implemented in both hardware and software, or a
combination of both.
10.7.2. Functions performed by firewalls
The functions performed by firewalls are:
1. Allow the traffic from the Internet to enter only when it is going
to a particular set of applications. For these applications, traffic is
allowed to go only to certain internal addresses (machines) and not