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What is a Proxy Server?

what is proxy server diagram

A proxy server is a computer or usually set of computers that act as an intermediary between a client computer and a web server. It enables client computers to make indirect requests through it for resources or services such as web pages, videos, PDF files, etc.

Here’s how it works: A client contacts the proxy server, requests a file, web page or other resource from a different server. If the proxy server has the requested file or web page in its cache, the proxy server returns the file or web page to the client. Otherwise, it connects to the requested server, provides the client with the file or webpage, and then save it in its cache for use later.

Because of their position between client and the requested resource, proxy servers can potentially alter a client’s request or the server’s response.

Using Web Proxy Server to Cache Files or Web Pages

Caching Web proxies can speed up access to frequently accessed web pages, by building a cache of frequently requested web pages or files. By speeding up the network traffic, it also provides needed reliefs to server load.

After getting a client’s request for a website URL or file, the proxy first looks in its own cache. If the data is in the cache, this immediately goes to the requesting client.

Otherwise, the proxy asks for the connection to the server, and forwards the results to the client after keeping a copy for itself. The proxy keeps its cache updated by discarding the least used or oldest files.

Using Web Proxy Servers to Restrict or Unblock Internet Traffic

Companies frequently use web proxy servers to restrict internet traffic to a single entrance or exit point within the company network.

This has dual benefits for the company. Not only is it easier to guard against threats and malware coming in from a single point (by scanning the transmitted content), proxy servers also enable organizations to control employees’ internet activities by filtering content and restricting visits to certain websites.

For individual computer users, web proxies are often used for precisely the opposite result – circumvent company internet filters and to browse the Web anonymously by hiding their device’s IP addresses.

Many services exist to provide consumers with proxies to surf the web anonymously. By accessing a website via a proxy server, the website that the proxy server connects to is only able to track the IP address of the proxy server. The IP address of the client computer (your computer) stays hidden to the web server.

Only the proxy has information on the IP address of the client computer (individual computer user). To protect customers’ privacy, companies that provide the proxy services claim that they delete the logs frequently.

Example of How a Proxy Server Work

Figure 1) Two computers, connected through a third computer (shown in red) acting as a proxy, communicate with each other (shown in grey). Figure 1) Two computers, connected through a third computer (shown in red) acting as a proxy, communicate with each other (shown in grey).

The drawing of Alice (client computer), Proxy, and Bob (web server) shows how a proxy server theoretically works. Alice can relay questions to Bob through the proxy server using the proxy server’s IP address without having to contact him directly. Bob, from his perspective, thinks he is communicating directly with the proxy.

In practice, not all web proxies are created equal. There is a huge variance in how a web proxy can be set up and its technical capabilities. Decoding how a web proxy provides clients with enhanced privacy and security primarily depends upon how the individual proxy handles the individual data packets (the information postcards of the Internet) traveling between Alice and Bob, use of encryption techniques, and the intent of the proxy owner.

Here are three basic communications that a web proxy server might communicate with the users:

The Different Types of Proxies


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