abstract:In the context of computer networking, an application-level gatewayRFC 2663 - ALG: official definition (refer section 2.9) (also known as ALG or application layer gateway) consists of a security component that augments a firewall or NAT employed in a computer network.
This paperintroduces the ideaoflogicintegration, and presents the architecture of an aero-messageswitchingsystem, which is the applicationlevelgateway.
The truly paranoid may elect to use the 2.4 kernels' Netfilter4 facility (adding stateful packet filtering) or a commercial application-level proxy gateway.