2. Overview of firewall functions

With the exception of the filtering function, which will be discussed in detail in the following sections, this section provides an overview of the other functions traditionally hosted in a firewall to support either a security need or a network-related functional requirement. The aim here is to understand the interactions between these functions and the filtering function. The functions are as follows:

• NAT (Network Address Translation ): address translation (private and public) enables the administrator of a private network to allocate as many private addresses as necessary to his terminal park, and to assign public addresses (in limited numbers) virtually to some of his servers accessible from the public network. By defining NAT rules, the administrator regulates the accessibility of a terminal to the public network and the accessibility...