The World Wide Web (WWW) is a repository of information linked together from points all over the world. The WWW project was initiated by CERN (European Laboratory for Particle Physics) to create a system to handle distributed resources necessary for scientific research.
The WWW is a distributed client-server service, in which a client using a browser can access a service using a server. However, the service provided is distributed over many locations called sites. Each site holds one or more documents, referred to as Web pages. Each Web page can contain a link to other pages in the same site or at other sites.
The browser interprets and displays a Web page. Each browser usually consists of three parts:
The Web page is stored at the server. Each time a client request arrives, the corresponding document is sent to the client. To improve efficiency, servers normally store requested files in a cache in memory; memory is faster to access than disk. A server can answer more than one request at a time by using multithreading or multiprocessing.
A client that wants to access a Web page needs the address. To facilitate the access of documents distributed throughout the world, HTTP uses locators. The uniform resource locator (URL) is a standard for specifying any kind of information on the Internet. The URL defines four things:
The web document on World Wide Web (WWW) can be broadly divided into two categories:
The Hypertext Transfer Protocol (HTTP) is a protocol used mainly to access data on the World Wide Web. HTTP uses the services of TCP on well-known port 80. HTTP is a stateless protocol.
A proxy server is a server which acts on behalf of other clients, and presents requests from other clients to a server. It acts as a server while talking with a client, and as a client while talking with a server. It is a server that sits between a client application (Web browser), and a real server. It improves performance and filter requests to prevent users from accessing a specific set of web sites.
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