What is a Proxy Server?
By definition 'proxy' is the authority to act for another. That is, a person or device that is authorized to act on behalf of another.
This is exactly what a proxy server achieves. Clients computers make requests for information and a proxy server services those requests by acting as an intermediary between the client computer and the destination server.
Proxy servers are usually used in large networks where many clients require internet access. Providing a central point of access has administrative and security benefits. Content filters, for example, can be installed on the proxy server preventing the client computers from exposure to undesired content. Although most proxy servers today are used for web surfing, technically, many other protocols can be proxied as well.
Related Content
Transparent proxy ocurs when packets destined for the Internet are intercepted by WCCP (Web Cache Communications Protocol) and redirected to a proxy server. The advantage of using transparent proxy is that there is no client configuration required.
Public proxy servers achieve the same result but instead of the traffic being proxied on its way out to the Internet from the local network, it is proxied when it is out on the Internet by the public proxy. Public proxy servers can be used to bypass firewalls and web filters. Requests made to any proxy server are difficult to track from the Internet because the requestor's address always appears as the proxy server address - not the requesting client.
Reverse proxy servers work the same way as a proxy server but in a logically opposite direction. Normally, the client computer is on the inside of the network and makes a request out to the Internet. With a reverse proxy, computers on the Internet make requests that are proxied into your network. Typically to a web server that is providing web content.
For those after a technical perspective; In the case of a web proxy the most common TCP ports used by the proxy service are 8080 or 3128. A proxy server will establish a TCP connection between itself and the requesting client (on port 8080 or 3128) and establish a different TCP connection between itself and the destination web site on port 80. The source address for the HTTP request is the proxy server itself, not the client PC.
Related Content
What is the difference between direct access and access by proxy?
When a computer accesses a website directly, it establishes a TCP session directly with the web server. An example of a directly connected session can be seen below:
1, A single session between the PC and the website
TCP pc2:1257 www.it-pathways.com:http ESTABLISHED
When a computer accesses the same website by proxy, it establishes a TCP session with the proxy server who in turn establishes a TCP session with the web server.
Example of a proxy connected session can be seen below.
1. One session between the PC and the proxy server
TCP pc2:1257 proxyserver:3128 ESTABLISHED
2. And another session between the proxy server and the website
TCP proxyserver:1292 www.it-pathways.com:http ESTABLISHED
