Microsoft Internet Security and Acceleration Server 2000

About the Firewall Service

The Firewall service is a generic, circuit-level proxy for Windows Sockets (Winsock) applications. The ISA Firewall service makes Telnet, e-mail, news, Microsoft NetShow®, RealNetworks RealAudio, Internet Relay Chat (IRC), and other Winsock-compatible client applications perform as though they were directly connected to the Internet. The client application makes Winsock application programming interface (API) calls to communicate with an application running on an Internet-based host. The ISA Firewall service redirects the necessary functions to the ISA Server computer, thus establishing a communication path from the internal application to the Internet application through the ISA Server computer. This redirection eliminates the need for a specific gateway for each protocol, such as Network News Transfer Protocol (NNTP), Simple Mail Transfer Protocol (SMTP), Telnet, or File Transfer Protocol (FTP). The ISA Firewall service allows applications with no built-in support for a proxy to benefit from proxy service without using the protocols.

The Firewall service runs as a stand-alone service on Windows 2000. It establishes gateway connections between the Windows Sockets (Winsock) applications on the client and the Internet host. The local network remains secure, because communication is channeled through the ISA Server. The Firewall service can be enhanced by using application filters.

This section contains the following topics: