Biwu Yang (East Carolina University, USA)
DOI: 10.4018/978-1-61350-507-6.ch008
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Firewall is a critical technology in protecting enterprise network systems and individual hosts. Firewalls can be implemented through a specific software application or as a dedicated appliance. Depending on the security policies in an organization, several firewall implementation architectures are available, each with its advantages and disadvantages. Therefore, a thorough understanding of firewall technology, its features and limitations, and implementation considerations is very important in the design and implementation of effective firewall architecture in an organization. This chapter covers the life cycle of firewall design, selection, and implementation.
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Type Of Firewalls

Firewalls can be classified as software solution and dedicated hardware solution. In the early days, firewalls were software solutions.

As a software solution, a firewall is designed as an application to be installed on a regular computer. The computer would have at least two network interface cards (NIC) installed, one connects to the “outside” network and the other connects to the “internal” network, as illustrated in Figure 1. The computer is termed “dual homed host”. More NICs can be used if the firewall is designed to connect to multiple internal networks.

Figure 1.

Dual Homed Host in a Network


A hardware solution, also termed as “dedicated firewall” or “firewall appliance”, is a device specifically designed to perform the function of monitoring and filtering network traffic. In most cases, this is a “single purpose” computer with a stripped down operating system that is specially designed to perform firewall related functions.

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