ISA Server Web Proxy Architecture

The ISA Server Web proxy is an application filter on the Microsoft Firewall service. Functions provided by the Web proxy include:

• Parsing of HTTP protocol traffic.
• Support for HTTP 1.1 protocol features.
• Authentication of client requests.
• Web filter-notification support.

Note to Developers of Web Filters for Internet Information Services

There are several differences between the implementation of ISAPI in Internet Information Services (IIS) and in ISA Server. These are described in ISAPI: Comparing IIS and ISA Server.