A firewall is a system that enforces an access control policy between networks. Located on a gateway into the network, the firewall blocks traffic that does not have permission to access the network. An organization establishes a firewall so that it can control access to resources. For example, an organization that allows intranet users access to the Internet installs a firewall to prevent external users from accessing internal resources.
Proxy servers are typically used to constrain and secure connections from an organization’s computers to sites that require connecting across the Internet. To enhance security, some network configurations require all Internet connections to go through a proxy server, including IIOP connections to an application server.
See Chapter 12, “Deploying Applications Around Proxies and Firewalls” for more information.
