Overview on the Caching Proxy, WebSphere Edge Components.

Overview on the Caching Proxy Component in Websphere Application Server.

In an enterprise environment, a proxy server is a server that acts as an intermediary, typically placed in a demilitarized zone (DMZ). This DMZ is between the Internet and the server environment in the internal zone, providing the business services. It validates the request for an Internet service.
If the request passes filtering requirements, the proxy server forwards it to servers in the internal (secure) zone and acts as the requester. This mechanism prevents direct access from the (insecure external zone) to the sensitive servers in the internal zone .
The proxy servers used here can also improve performance by caching content locally.

The two main advantages of using a proxy server are system security and performance:

Security: A proxy server provides an additional layer of security and can protect HTTP servers further up the chain. It intercepts requests from the client, retrieves the requested information from the content-hosting machines, and delivers that information back to the client. If you are using a firewall between the reverse proxy server and the content HTTP server, you can configure the firewall to allow only HTTP requests from the proxy server.

Performance: A proxy server can increase the performance of your WebSphere Application Server in several ways.
Encryption/SSL acceleration: You can equip the proxy server with SSL acceleration hardware that can improve the performance of SSL requests.
Caching: The proxy server can cache static content to provide better performance.
Load balancing: The proxy server can balance the workload among several content HTTP servers.

WebSphere Edge Components Caching Proxy (CPS)

The WebSphere Edge Component Caching Proxy reduces bandwidth usage and improves a Web site's speed and reliability by providing a point-of-presence node for one or more backend content servers. Caching Proxy can cache and serve static content and content dynamically generated by WebSphere Application Server.

The proxy server 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 using the Hypertext Transfer Protocol (HTTP). However, you can configure the proxy server to handle other protocols, such as File Transfer Protocol (FTP) and Gopher.
The proxy server stores cache-able content in a local cache before delivering it to the requester. Examples of cache-able content include static Web pages and
JavaServer Pages files that contain dynamically generated, but infrequently changing, information. Caching enables the proxy server 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.
There are several plugins for the Caching Proxy and for additional functionality to the proxy server, but we used only the default setup.

WebSphere Proxy Server (PS)

WebSphere Proxy Server (PS) is a new type of server supported in WebSphere Application Server Network Deployment (ND) package (in version 6.0.2 and later). This Proxy server receives requests from clients initially on behalf of content servers and work load manages, and routes the requests across content servers depending on the policies and filter classification definitions.
WebSphere Proxy servers can secure the transport (using SSL), content and protect the identity of application servers using the response transformation feature (URL rewriting). The Proxy server can also cache responses to improve throughput and performance. Another good feature to note is SSL offload at the Proxy server. When using this feature you can terminate an SSL (HTTPS) connection at the proxy server after receiving the request from the client and use HTTP as transport protocol between proxy server and the content server(s) (which are application server(s)). You can administer and configure this Proxy server from the deployment manager's administrator console (or wsadmin) in an ND environment.
This Proxy server is much more capable than the reverse proxy servers (the Edge caching server and the WebSphere plugin) with its advanced configuration capabilities, dynamic routing policies, and integrated system management in ND topology.
It is interesting to note that the Proxy server can also route requests across multiple cells and supports session affinity and failover.