A proxy server, in a general sense of the term proxy, is a stand-in server. In a network, a proxy server is the entity that sits between corporate client machines and the Internet. For example, it may sit between a client application, such as a Web browser and the corporate server. Proxies are used to intercept incoming and outgoing requests to see if it can fulfill the requests itself. If not, it then forwards the request to the real server. 

Forward and Reverse Proxies
The most common types of proxy servers are called forward and reverse proxies. A forward proxy is used to forward outgoing requests from a private network or intranet to the Internet, usually through a firewall. The main goal of the forward proxy is to provide a level of security and also to reduce network traffic. For example, if a Web browser is configured to do so, all requests will be made through the proxy, which in turn will apply filtering rules. The proxy will then request the site the user was trying to reach on his or her behalf, or more accurately: "by proxy."

In contrast, a reverse proxy handles requests coming from the Internet to the private network or intranet. This provides a level of security that prevents the Internet clients from having direct access to data on the corporate servers. The reverse proxy sits between your Web server and the world. When an HTTP connection comes in, the reverse proxy will decide what to do, and then make a request to the appropriate backend Web server. Reverse proxies are very important, and they are commonly used to secure and load balance Web servers and also act as a content filter.

Proxy servers can also be chained. This is not a type of proxy server, but rather a method for using reverse and forward proxy servers across your network or across multiple networks in cases where the number of requests to the proxy may exceed its limits causing it to slow down. A proxy server chain lets you assign a specific number of clients to each proxy within the chain.

The Purpose of a Proxy Server
Proxy servers have two main purposes:

Improve Performance: Proxy servers can dramatically improve performance for groups of users. This is because it saves the results of all requests for a certain amount of time. Consider the case where both user X and user Y access the World Wide Web through a proxy server. First user X requests a certain Web page, which we'll call Page 1. Sometime later, user Y requests the same page. Instead of forwarding the request to the Web server where Page 1 resides, which can be a time-consuming operation, the proxy server simply returns the Page 1 that it already fetched for user X. Since the proxy server is often on the same network as the user, this is a much faster operation. Proxy servers can support hundreds or thousands of users.

Filter Requests: Proxy servers can also be used to filter requests. For example, a company might use a proxy server to prevent its employees from accessing a specific set of Web sites.

Last updated: August 22, 2008
Article adapted from "Secure by Proxy" on EnterpriseNetworkingPlanet, and "Server Types" on Webopedia.com

 

What is a Server
Servers are often dedicated, meaning that they perform no other tasks besides their server tasks. On multiprocessing operating systems, however, a single computer can execute several programs at once. A server in this case could refer to the program that is managing resources rather than the entire computer.

Secure by Proxy
A reverse proxy can be used to secure and load balance Web servers. In this article we'll discuss the concept of a proxy server and reverse proxies, and how they can be used to provide better Web (HTTP) services.

Software Proxy Troubleshooting : Windows Proxy Software
Below is the latest version release information for some of our favorite proxy software applications. Many have free downloadable trial versions that will allow you to test drive before you buy.

Compare Proxy Server Features
Looking for a server that meets specific requirements? Please select key criteria from the features noted below. (Hint: To maximize results, check off only the most critical requirements.)

Creating a Proxy Server Chain
Now that you know how an individual Proxy Server works, keep in mind that each Proxy Server is only capable of servicing a limited number of requests before it begins to get bogged down. Therefore, it's possible to use multiple Proxy Servers in your organization in chains.