Data Bases • Custom Term Papers • Free Term Papers • Free Research Papers • Free Essays • Free Book Reports • Plagiarism? Links • Top 100 Term Paper Sites • Top 25 Essay Sites • Top 50 Essay Sites • Search 97,000 Papers @ DirectEssays.com • Search 101,000 Papers @ ExampleEssays.com • Search 90,000 Papers @ MegaEssays.com Free Essays • Term Paper Sites • Chuck III's Free Essays • Free College Essays • TermPaperSites.com • My Term Papers • Get Free Essays • Essay World • Planet Papers	Search Lots of Essays Back to Subjects - Technology How the internet works How the internet works What are the Advantages of the Internet? 2 What is Required for the Internet to Work? 4 What Client Applications Can be Used on the Internet? 9 Summary 12 Gossary 14 This paper will answer the following questions about the Internet: Ψ What Are the Advantages of the Internet? Ψ What is Required For the Internet to Work? Ψ What Client Applications Can be Used on the Internet? This document uses a number of terms with which you need to be familiar. They can be found in the Glossary found on page 13. We will start this section by answering this question, "What is the Internet?" The Internet is a world-wide network of computers. It is an Information Superhighway that carries traffic to and from a collection of servers-- remote computers that handle requests for data and information, much like the waiter in a restaurant that takes orders for food. This collection of servers distributed all over the world and is called the World Wide Web (WWW). Servers respond to clients-- computers that request information, much like a customer in a restaurant orders food from the waiter. You click links to text, pictures, music, or video located on these servers. In addition, you can play the selected files on your local client PC, workstation, or terminal, as well as, links to related information located on these servers. Therefore, you do not have to remember where the information is located or to learn any obscure commands to access the Web. What are the Advantages of the Internet? Now that you know what theI internet is, you will learn about its advantages and how it is used to For computers to access the Internet, they require Ψ a physical means of transferring information Ψ software applications that retrieve and send information and allow users access information. There are three common methods of accessing the Internet: Dial Up Modem: First, the most common method for individual computers to connect to the Internet is via dial up modem, which is used to provide a connection to an ISP-- Internet Service Provider over normal telephone lines: Dedicated Line: Another method for computers to connect is through a dedicated line. Companies may use a dedicated communications link connection, such as an ISDN-- telephone company land-lines or On Ramp-- a utility to connect to an ISP or the main link (backbone) of the telecommunications carrier. The dedicated line allows you to connect to an ISP or the main link (backbone) of their telecommunications carrier. Mobile: Mobile users can connect to the Internet through mobile phones or via satellite using a portable satellite transceiver. This section has provided an analysis of the physical means to transfer data. Now that we know the physical means to transfer data, the next section discusses the physical requirements for the Internet to work. What is Required for the Internet to Work? The following physical requirements are needed for the Internet to work: Clients: Clients communicate with a WWW server using the Hypertext Transfer Protocol (HTTP). Thus, when you select a WWW link, the client looks up the hostname and makes a connection with the WWW server. Then the HTTP software on the server responds to the client's request and the client and the server close the connection. Servers: For applications to work, there must be computers to provide e-mail and Web services. Servers run server applications that store and transmit e-mail messages, as well as distribute Web page content. Other servers provide additional support services such as identification of computers by name, e-commerce payment gateways (which process credit card payments) and proxy servers (which allow your ISP to provide faster Web browsing services). Since every Internet application requires a server somewhere to provide these services, still other servers run multi-play games, store and distribute news, provide chat and ICQ facilities and distribute music. Routers: In addition to servers to run applications, routers are needed to direct information. Routers are dedicated computers that interconnect the various parts of the Internet. When a router receives a packet-- a package of data exchanged between devices over a data communication link-- of information it reads the header. This determines where the information came from and where it needs to go. If the packet needs to go to a computer on the same network, the router simply ignores it. On the other hand, if the packet needs to go to a computer on a different network, the packet is passed on to the destination network. At the destination network, the destination router performs a similar function. It ignores packets destined for its network and passes packets on to other networks as appropriate. Packets: The Internet transfers data around the network in discrete packets of information. Since there are now millions of computers on the Internet, it is impossible to have physical circuits connecting each computer to the others. Thus, it is impossible to use switched circuits since the delay in establishing and disconnecting switched circuits each time a connection was made would effectively stop the Internet. Data is exchanged between programs by using protocols. The four most common are Ψ Hypertext Transfer Protocol (HTTP) Ψ Transfer Control Protocol/Internet Protocol (TCP/IP) First, File Transfer Protocol (FTP) is one of the oldest and most popular of all Internet services. FTP is a simple protocol that defines how binary files are transferred between computers. Users can access millions of files, documentation, source code, and other useful objects on anonymous FTP archives. A WWW browser can view and retrieve information from FTP archives. Gopher was developed at the University of Minnesota as a distributed campus information service. There are Gopher servers everywhere, many of them which provide campus-wide information systems. Gopher information is organized into menus. However, because hypertext provides the same services as Gopher and more, many sites are moving from gopher-supplied information to WWW-supplied information. Hypertext Transfer Protocol (HTTP) is the protocol provided by WWW servers. It includes hypertext linking, HyperText Markup Language (HTML), and server scripts. Transmission Control Protocol/Internet Protocol (TCP/IP): The Internet uses he TCP/IP protocol. Once physically connected, the computer must use the agreed TCP/IP network protocol in order to communicate. The software to do this is usually built into the computer or network operating system and is installed with Windows or Macintosh when you configure your Internet connection. Now that we know how data is exchanged, in the next section we will discuss how Internet addresses help computers find information. Addresses contain directions to get you to a specific address. Three types of Internet addresses are: Uniform Resource Locators (URL's) consist of an Internet Protocol prefix, generally HTTP, an Internet domain name, and file or folder names, which refer to a specific document location. The URL tells you that a page is in a domain, directory, folder, and has a name with the html extension. This address specifies the access-method (how), the server name (where), and the location (what) is needed for a WWW client to find and access a WWW object. As shown below, the general form of a URL is access-method://server-name[:port]/location. http://www.upandaway.com/balloons/hotair.html Protocol Server Domain or Site Directory File name or name folder name type inside folder web page Server name - system on Internet on which information is stored Domain/Folder Name - the Web server name .net - network provider organization Directory inside folder - directory or folder on the Web server that contains a group of related Web pages within the website www.upandaway.com.balloons File Name - a Web page inside the folder Next, IP Addresses. Each computer connected to the Internet transfers data around the Internet using virtual circuits. These circuits route data to the individual computers that are identified by their IP-address. An IP-address is currently four bytes long and is usually written as four number separated by dots (e.g., 192.40.254.0 ). Since a byte can contain a number from 0 to 255, it is theoretically possible to have 4.3 billion unique addresses. However, the number of addresses available is less than that. Some addresses are used for specific purposes, such as broadcast packets to all computers on a particular network or to identify a network. In addition, the address the address space is distributed across geographic regions. Some countries, such as Australia, have effectively run out of address space. Other countries (and some corporations) have more address space than they presently need. The server name is an IP host name or an IP address. WWW servers often start with the name "www", as in www.wright.edu. The port number is usually not needed. If there are many servers on one machine (e.g., two different WWW servers on the same host), a user would use a port number to select one of them. By default, WWW servers are on port 80. Other protocols have different ports (e.g., the default for FTP is 21). Most users never need to know about port numbers. Domain Name System (DNS). Another method used to help find an Internet address is the DNS. This system became a part of the Internet in the early 1980's. It is a distributed database that computers can use to find the IP address of any computer registered in the DNS database. The DNS works on a hierarchy where each organization has responsibility to manage their own part of the DNS and must provide name server computers, which provide the address information as requested. Therefore, when a computer needs to find the address of a particular computer, it goes one of the top level or root domain name server computers that are run by the Internet Authority and distributed around the world. These computers then direct the querying computer to the most appropriate name server to answer the query. These second level domain name server computers are usually responsible for the names for a particular class of domain name (com, edu, org) or for a country's domain names (au, uk, nz, sg). Now that you know what is an Internet address, we can look at client applications. What Client Applications Can be Used on the Internet? Useful client software applications that can be used on the Internet include Hypertext provides the links between different documents and different document types. In a hypertext document, links from one place in the document to another are included with the text. By selecting a link, you are able to jump immediately to another part of the document or even to a different document. Moreover, in the WWW, links can go not only from one document to another but also from one computer to another. URLs provide the hypertext links between one document and another. Links can access a variety of protocols (e.g., ftp, gopher, or http) on different machines (or your own machine). To use the Internet for Web browsing or to send and receive e-mail, you require applications to request information from the Internet and display it on your computer. These client applications include Web browsers to display Web pages containing the text and graphics displayed on your screen, e-mail packages to send and receive e-mail, and media players to play music. Now that you know what components are involved in making the Internet work, this section explains the steps involved in the entire Internet process. When you "call up" a URL through your Web browser, the browser first has to resolve the address it has been given. In the case of http//www.wright.edu, the Web browser will first look for the computer that stores information on the ".edu" domain. The domain name system is structured as a hierarchy of names, and .edu is what is referred to as a gTLD, a generic top-level domain name. A second level domain name consists of a top-level domain name, with another name preceding it, separated by a dot. Thus "wright.edu" is a second level domain name. Once the URL is selected, packets are sent. When an application needs to communicate with a server application on a remote computer, it sends packets to the specific server's IP address and appropriate port number. On the remote computer, the server application constantly "listens" for IP packets addressed to the specific port. If you want to send someone an email, your software will either contact the mail server at your ISP, which will then relay the message. Or it will use the DNS to locate the remote computer and communicate directly. After the packet is sent, the data is collected. Once the data arrives at the destination computer, the destination computer needs to know what the data contains so that it can deal with it. Thus an additional address field is thus built into the protocol. This additional address field, known as the socket or port number, is used to identify where the data is to be directed so the connection can be made. Upon making the connection, the two computers exchange a dialogue to identify each other, the recipient, any special delivery instructions, and the email message itself. Just as email relies upon a standard dialogue to transfer information, so does Web browsing. Using HTTP, your browser software connects to a Web server and starts downloading Web pages by requesting files from the server. After the connection is made, the files are downloaded. If you need to download a file, the Web browser may request either that file via HTTP or may open an FTP session to another application running on the server. In essence, the computer opens a connection, requests a specific file, and specifies whether the file to be transferred as a binary or text file. The remote computer, upon receiving the request, authenticates the requestor computer and,upon successful authentication, delivers the file in the correct format. Now the page can be displayed. As your browser downloads and interprets the Hypertext Markup Language (HTML)-- code, which the Web page is written in, it will display the contents of the page on your screen. If it encounters a tag that links to a graphic or audio file, the browser will use HTTP to request the file from the Web server and display it accordingly. If the file is not a .GIF or .JPG graphics file, the browser uses MIME to help identify the file and determine the correct application to process the data. The Internet is a world-wide network of computers used to communicate, learn and play. You can access the Internet via dial-up modem, dedicated line, mobile phone or by portable satellite transceiver. For the Internet to work, clients, servers, routers and packets are needed. Once you have these physical components, the data is exchanged between programs using protocols. The most common are FTP, Gopher, HTTP and TCP/IP. There are three types of Internet addresses: URL's, IP, and Domain Name System. Hypertext, Browsers and E-mail are client application software used on the Internet. URL's provide hypertext links between different document and document types. Web browsers display Web pages and e-mail to send and receive e-mail messages. In the Internet process, you call up a URL. Packets are then sent to the specific server's IP address to relay the message; the DNS locates the remote computer and communicate directly. The data arrives at the destination computer that identifies where the data is to be directed so the connection can be made. Once connected, the two computers exchange a dialogue to identify each other and the e-mail message. Next, the browser software connects to the Web server, requests files, and downloads Web pages As your browser downloads and interprets the HTML code, the contents are displayed on the screen. Backbone - the main link of a telecommunications carrier. Client - a computer that requests information from the server, much like a customer in a restaurant orders food from the waiter. Client Applications - the software applications used on the Internet. Domain - part of the Uniform Resource Locator (URL) that refers you to the Web server name, much like the name of a folder in which you have certain information filed. Domain Name System (DNS) - a system in which the DNS Server matches Domain Names to IP addresses much like the Yellow Pages matches business names to phone numbers. File Transfer Protocol (FTP) - one of the oldest and most popular Internet services used to transfer files. .GIF - Graphics Interchange Format; a graphic file gTLD - a generic top level domain name. Gopher - a utility to search the Internet. Hypertext - text containing the links between different documents and different document types. Hypertext Markup Language (HTML) - the language of the World Wide Web. Hypertext Transfer Protocol (HTTP) - the method by which data is transferred over the Internet. ICQ - an on-line instant messaging program. Internet - a world-wide network of computers, an information Superhighway that carries traffic. Internet Protocol Address (IP) - an address used to identify individual computers. Internet Service Domain Name (ISDN) - telephone company land lines. Internet Service Provider (ISP) - a company that provides access to Internet service. .JPG - Joint Photographics Expert Group graphics file MIME - Multipurpose Internet Mail Extension used by a browser to help identify the file and determine the correct application to process the data. On Ramp -a utility to connect to an ISP or the main link (backbone) of the telecommunications carrier. Packet - a package of data exchanged between devices over a data communication link. Protocol - a set of conventions (a computer dialect) that determines how data will be exchanged between programs. Proxy server - a server designed to protect internal resources on networks that are connected to other networks such as the Internet. Router - a dedicated computer that interconnects the various parts of the Internet, like a traffic cop that directs Internet traffic. Server - a remote computer that handle clients' requests for data and information, much like the waiter in a restaurant takes orders for food. Socket - the additional address field and is used to identify where the data is to be directed. TCP/IP (Transfer Control Protocol/Internet Protocol) - the protocol of the Internet. Uniform Resource Locator (URL) - the hypertext link between one document and another. WWW - the general form used for the World Wide Web; refers to the server name. World Wide Web - a collection of servers distributed all over the world that respond to various clients. Bibliography: Word Count: 3281
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