WhAT IS PROXY SERVER ?

       
         Friends we always face this term in our normal life,for example if we cannot connect to any website then it notifies as "NOT CONNECTED TO PROXY SERVER",so what is this term proxy server?? some might even get this term in your syllabus, so it might be better to get some basic knowledge about this term.
 So WHAT IS PROXY SERVER?
            A proxy server is a computer that offers a computer network service to allow clients to make indirect network connections to other network services. A client connects to the proxy server, then requests a connection, file, or other resource available on a different server. The proxy provides the resource either by connecting to the specified server or by serving it from a cache. In some cases, the proxy may alter the client's request or the server's response for various purposes.For example, it may filter traffic by IP address or protocol. If the request is validated by the filter, the proxy provides the resource by connecting to the relevant server and requesting the service on behalf of the client. A proxy server may optionally alter the client's request or the server's response, and sometimes it may serve the request without contacting the specified server. In this case, it 'caches' responses from the remote server, and returns subsequent requests for the same content directly.

schematic representation of a proxy server, where the computer in the middle acts as the proxy server between the other two.

A proxy server has a large variety of potential purposes, including:

• To keep machines behind it anonymous (mainly for security) 
• To speed up access to resources (using caching). Web proxies are commonly used to cache web pages from a web server. 
• To apply access policy to network services or content, e.g. to block undesired sites. 
• To log / audit usage, i.e. to provide company employee Internet usage reporting. 
• To bypass security / parental controls. 
• To scan transmitted content for malware before delivery. 
• To scan outbound content, e.g., for data leak protection. 
• To circumvent regional restrictions. 
• To allow a web site to make web requests to externally hosted resources (e.g. images, music files, etc.) when cross-domain restrictions prohibit the web site from linking directly to the outside domains. 

You may see references to four different types of proxy servers:

Transparent Proxy
        This type of proxy server identifies itself as a proxy server and also makes the original IP address available through the http headers. These are generally used for their ability to cache websites and do not effectively provide any anonymity to those who use them. However, the use of a transparent proxy will get you around simple IP bans. They are transparent in the terms that your IP address is exposed, not transparent in the terms that you do not know that you are using it (your system is not specifically configured to use it.)

Anonymous Proxy
      This type of proxy server identifies itself as a proxy server, but does not make the original IP address available. This type of proxy server is detectable, but provides reasonable anonymity for most users.

Distorting Proxy
     This type of proxy server identifies itself as a proxy server, but make an incorrect original IP address available through the http headers.

High Anonymity Proxy
  This type of proxy server does not identify itself as a proxy server and does not make available the original IP address.

some of the uses of proxy servers are:-

1)FILTERING:-
        A content-filtering web proxy server provides administrative control over the content that may be relayed through the proxy. It is commonly used in both commercial and non-commercial organizations (especially schools) to ensure that Internet usage conforms to acceptable use policy.

2)CACHING:-
     A caching proxy server accelerates service requests by retrieving content saved from a previous request made by the same client or even other clients. Caching proxies keep local copies of frequently requested resources, allowing large organizations to significantly reduce their upstream bandwidth usage and costs, while significantly increasing performance. Most ISPs and large businesses have a caching proxy. Caching proxies were the first kind of proxy server.

3) Bypassing filters and censorship
      If the destination server filters content based on the origin of the request, the use of a proxy can remove this filter. For example, a server using IP-based geolocation to restrict its service to a certain country can be accessed using a proxy located in that country to access the service.Likewise, a badly configured proxy can provide access to a network otherwise isolated from the Internet.

4)Access control:-
     Some proxy servers implement a log on requirement. In large organizations, authorized users must log on to gain access to the web. The organization can thereby track usage to individuals.I hope this post would have helped you to some extent,as topic was on technology reference was taken from wikipedia, thank you friends for your feedback on previous topics,and hope you give feedback on this topic as well.