Proxy servers

Proxy servers  : a server, which acts as an intermediary between internal users and external host

The proxy server takes requests from a user and then performs those requests on behalf of the user. To the external system, the request looks as if it originated from the proxy server, not from the user on the internal network.

To perform NAT functions : A proxy server can process and execute commands on behalf of clients that have private IP addresses. This enables an organization with only one registered IP address to provide Internet access to a large number of computers. This process is known as IP proxy.

To allow Internet access to be controlled : Having a centralized point of access allows for a great deal of control over the use of the Internet. By using the functionality of a proxy server application or by using an add-on feature, proxy servers can filter requests made by clients and either allow or disallow them. You can, for example, implement uniform resource locator (URL) filtering, which allows or denies users access to certain sites. More sophisticated products can also perform tests on retrieved material, to see if it fits acceptable criteria. Such measures are intended to prevent users from accessing inappropriate Internet web pages. As an "after the event" feature, proxy server applications also normally provide logging capabilities so that Internet usage can be monitored.

Caching Proxy Server : Caching enables the proxy server to store pages that it retrieves as files on disk. Consequently, if the same pages are requested again, they can be provided more quickly from the cache than if the proxy server had to continue going back to the Web server.

Increase performance where there is a great likelihood that more than one user might retrieve the same page.

To prevent issue of new page not been updated in the proxy server cache : Aging of cached information is implemented so that it is removed from the cache after a certain amount of time. Some proxy applications can also make sure that the page stored in the cache is the same as the page currently available on the Internet. If the page in the cache is the same as the one on the Internet, it is served to the client from the cache. If the page is not the same, the newer page is retrieved, cached, and supplied to the client.

Anonymizing Proxy Server : generally attempts to anonymize web surfing.

The socks  : an IETF (Internet Engineering Task Force ) standard.It is like a proxy system which supports the proxy aware applications.