In order to gain a thorough understanding of firewall technology, it is important to understand the various types of firewalls. These various types of firewalls provide more or less the same functions that were outlined earlier. However, their methods of doing so provide differentiation in terms of performance and level of security offered.
The firewalls discussed in this section are divided into five categories based on the mechanism that each uses to provide firewall functionality:
Proxy server firewalls
Nonstateful packet filters
Stateful packet filters
These various types of firewalls gather different types of information from the data flowing through them to keep track of legitimate ...