Overview

Acting as a reverse proxy, or a forward proxy, Caching Proxy intercepts data requests from a client, retrieves the requested information from content-hosting machines, and delivers that content back to the client. Most commonly, the requests are for documents stored on Web server machines (also called origin servers or content hosts) and delivered via the Hypertext Transfer Protocol (HTTP). However, you can configure Caching Proxy to handle other protocols, such as File Transfer Protocol (FTP), and Gopher.

Caching Proxy stores cacheable content in a local cache before delivering it to the requester. Examples of cacheable content include static Web pages and JavaServer Pages (JSP) FILES with dynamically generated but infrequently changing fragments. Caching enables the Caching Proxy to satisfy subsequent requests for the same content by delivering it directly from the local cache, which is much quicker than retrieving it again from the content host.

IMPORTANT: Caching Proxy is available on all Edge component installations, with the following exceptions:

Basic Caching Proxy configurations

The two basic proxy configurations are reverse proxy and forward proxy.

Reverse proxy (default)

By default, Caching Proxy is configured as a reverse proxy server. In a reverse proxy configuration, a proxy server is located between one or more content servers and the Internet. It accepts requests from Internet clients for content stored on the proxy server's home site. The proxy server appears to the client to be the origin (content) server; the client is not aware that the request has been sent to another server.

Forward proxy

Alternatively, you can configure Caching Proxy as a forward proxy server. However, client browsers must be individually configured to use the proxy. In a forward proxy configuration, a proxy server is located between the client and the Internet. Caching Proxy forwards a client's request to content hosts located across the Internet, caches the retrieved data, and delivers the retrieved data to the client.

The following changes in the ibmproxy.conf configuration file should be made to enable the forward proxy configuration:

Making these changes allows the forward proxy to do the following:

Transparent proxy (Linux systems only)

A variation of the forward Caching Proxy is a transparent Caching Proxy. In this role, Caching Proxy performs the same function as a basic forward Caching Proxy, but it does so without the client being aware of its presence. The transparent Caching Proxy configuration is supported on Linux systems only.

As with regular forward Caching Proxy, the transparent Caching Proxy is installed on a machine near the Internet/gateway, but client browser programs are not configured to direct requests to a forward Caching Proxy. Clients are not aware that a proxy exists in the configuration. Instead, a router is configured to intercept client requests and direct them to the transparent Caching Proxy.

For information on the directive for this configuration, see TransparentProxy -- Enable transparent proxy on Linux.