application level gateway
- A server, application, or system that serves as an intermediary between a private network, such as a LAN, and all other networks. Its two main functions are to provide document caching and access control. When caching, an application level gateway first attempts to access data which it has cached, and if not present there, it fetches it from a remote server where said data resides. When controlling access, it serves as a firewall. Its abbreviation is ALG. Also called proxy server, or proxy.