ISA Server Firewall and Caching Technology Background

Today, nearly all organizations must connect their LANs to the Internet to perform business processes ranging from simple interorganizational e-mail to sophisticated e-commerce, business-to-business data exchanges, and streaming multimedia content. These organizations need to protect their LANs while optimizing their connection to the Internet. In some cases, larger organizations face similar internal security and performance issues when interconnecting autonomous divisions.

A class of devices, firewalls and caching servers, has evolved to perform these functions.

A firewall sits between a trusted private network and less-secure untrusted networks, typically the Internet. A firewall inspects traffic and allows it to pass only if it meets a set of rules. A proxy server is a particular type of firewall that can filter traffic using application-level proxy technology, explained below.

A caching server saves bandwidth and improves response time by caching traffic for certain network protocols. The most common use is to cache content downloaded through protocols such as HTTP and the File Transfer Protocol (FTP).