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What is a Proxy?

A Proxy is a computer connected the internet and situated between your machine and the website server you are requesting a webpage from. Although there are many different roles for a Proxy server, generally there are two common reasons for using one:

  1. To speed up browsing by caching webpage data (images etc) therefore saving a full trip and download from the website you are visiting.
  2. To remain anonymous towards the website you are visiting whereby the Proxy acts as a "Go Between". The website server will only see and/or log the Proxy IP address, not your machines IP address.

The visual diagram 1.a below shows how and where a proxy is located on the network chain with further explanation below.

Diagram showing the concept of a Proxy server
  1. Computer number #1 is your home machine, it's IP address is 127.158.84.110. Lets say you open your web browser and enter the website address www.example.com and hit enter. Your computer will send a request for www.example.com but because you are using a Proxy server, that request will be sent to the Proxy server, not the www.example.com web server (yet).
  2. Computer number #2 is the Proxy server, it's IP address is 167.101.22.126. The Proxy server receives the request from your home computer for www.example.com. It then sends the exact same request to the www.example.com web server, but uses it's own IP address of 167.101.22.126, not your home computers IP address.
  3. Computer number #3 is the web server for www.example.com. It receives the request from the Proxy server, and logs it's IP address of 167.101.22.126. It then sends the web page back to the Proxy server, who then sends it back to your home computer completing the entire transfer request.
  4. Number #4 in our diagram is the Proxy servers Cache. When the Proxy receives the webpage from www.example.com it stores a local copy of it (html, images etc) on it's hard drive along with a time-stamp. Lets say 30 minutes later you decide to visit www.example.com again and your request is sent to the proxy server, but this time the proxy simply checks if the page on the web server has been altered in the past 30 minutes by comparing the time-stamp it recorded, with the last modified date and time of the web page. If the web page has not changed in the past 30 minutes, the Proxy server will send the Cached local copy of www.example.com web page making the entire process significantly faster than downloading the whole page and data again.

The Caching example above is one of many different ways a Proxy decides when to send the cached copy of a web page, and when to retrieve a fresh version, it really depends on the software used and it's settings.

Further Reading