This document provides an overview of firewall technologies and discusses their security capabilities and relative advantages and disadvantages in detail. It also provides examples of where firewalls can be placed within networks, and the implications of deploying firewalls in particular locations. The document also makes recommendations for establishing firewall policies and for selecting, configuring, testing, deploying, and managing firewall solutions.
This document does not cover technologies that are called “firewalls” but primarily examine only application layer activity, not lower layers of network traffic. Technologies that focus on activity for a particular type of application are not covered in detail in this document.