THE INTERNET. How the Internet Works What is the Internet?

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1 THE INTERNET How the Internet Works What is the Internet? It is a collection of local, regional, national and international computer networks that are linked together to exchange data and distribute processing tasks. It has been evolving over the past 30 years from an experiment with just four computers, into a vast information network that connects millions of micro, mini, mainframes and super computers. It is still evolving and will continue to evolve. Internet Technology Contains several components that ensure the functioning of the Internet: Network Service Providers (NSP): they maintain a series of communications links for Internet data (Sprint, MCI). Network Access Points (NAP): they serve as interconnection points for Internet data mentioned above. Thus, data can travel between NSP s. Internet Backbone: refers to the major Internet communications links. Internet Host: it is a computer on the Internet that provides services such as Web pages, e- mailboxes, or data routing services.

2 Internet Service Providers (ISP) It is a company that maintains an Internet host computer providing Internet access to businesses, organizations and individuals. When your computer connects to the Internet, it doesn t connect directly to the backbone. Instead your computer connects to the ISP and the ISP in turn is the one that connects to the backbone. There are several ways to connect to an ISP. While some access the Internet through a cable system TV system or personal satellite dish, the most common is through the telephone lines. This type connection is known as dial-up connection. Using a modem, the computer dials your ISP computer and establishes a connection using the phone line. As soon as the connection is established, the ISP routes data between your computer and the Internet backbone. Internet Addresses and Domains Every computer that connects to the Internet must have a unique identifier number called an IP address. The IP is a set of four numbers between 0 and 255 that are separated by periods. Examples of IP addresses are:

3 When your computer connects to with a dial-up connection, the ISP assigns a temporary IP address from a pool of addresses. Once you disconnect, your temporary IP address goes back to the pool of available addresses. In contrast, the Internet host computers have permanent IP addresses and they (in most cases) remain the same. Other terms that you should know: Router: it is a device that examines the data s IP address and then forwards the data towards its destination. Fully Qualified Domain Name: Also known as domain name, it is a name that is associated with an IP address. Users favor these names over only using IP addresses, since it is easier to remember a name, than a string of numbers. What is easier for you to remember, cocacola.com or ? Top-level Domain: it is the three-letter extension that is found in the FQDN. For commercial businesses, the domain name ends in.com, for educational institutions.edu. Outside USA, country codes serve as top-level domains (uk for United Kingdom, es for Spain, pa for Panama)

4 Web site: it is a location in a computer with a domain name that is part of the Internet. It contains information, distributed in one or several Web pages that can contain text and/or multimedia. These pages are related together via links, such as hypertext links. URL and Other Type of Internet Servers As was previously mentioned, a Web site is composed of several Web pages that contain information. These Web pages are stored as separate files. In order for a user to have access to these files, he needs to know the URL address. It stands for Uniform Resource Locator. It is an Internet address of a document in a computer, rather than just the address of the computer. These addresses usually begin with the prefix The http or Hypertext Transfer Protocol allows Web browsers such as Internet Explorer to communicate with the Web servers. Relevant terms to this section are: Web Server: it is a computer that uses special software to transmit Web pages over the Internet. Many Web server names are domain names prefixed with www. Home Page: it is the main or index page of a Web site and it generally contains links to other pages at the site.

5 For Example: My Website is at the Web Server There is an IP address associated with it, but I don t care, since csam.montclair.edu (my FQDN) is easier to remember. My URL address is and it specifies my Website s home page. Although the Web is the most popular Internet Service, it is not the only one. There are also FTP servers, which provides FTP services (see lab #7) to send or receive available files. There are also Usenet servers and IRC servers (Internet Relay Chat servers) handle the exchange of comments among members of Internet discussion groups, and chat groups respectively. The Versatile Web Browser In the past, if you needed to use an FTP service, you needed an FTP client program installed on your own computer. If you also wanted to use the other services (Usenet, Gopher, etc.) you needed to have a client program for each one. Today, Web Browsers handles all these different services in only one program. How does a Web browser display a Web page? There are three steps: 1. The Web browser requests a Web page from a Web server, by typing the URL or clicking a Web page link. 2. The Web server sends the data for the Web page over the Internet to your computer. 3. The data that you computer received is separated in two: the information and a set of instructions. The set of instructions determines how the information is presented to you in your Web browser.

6 By typing a valid URL address, your browser will receive its information from that site. But there are special Web sites called Web Portals, which supply services, search engine, chat rooms and links to shopping, weather, news, and sports. AOL, MSN, CompuServe and Lycos are some examples. Many of these services are generally free. However, some of these portals are maintained by commercial information services, which also serve as ISP. America Online and MSN are the most popular of them. More Terms: Streaming media: technology that sends a media file to your computer divided in small segments. When your computer starts playing the first segment, the Web server sends another one, and so on until the media segment ends. Animated GIF: it is an animated image file that plays seamlessly as part of a Web page. Downloading: refers to the process of transferring a file from a remote computer to your computer s disk drive. Most browsers allow downloading. Uploading: refers to the processing of transferring a file from your computer s hard drive to a remote computer. Few browsers allow uploading; you must use an FTP client program.

7 Plug-in: also known as viewer or player. It is a software module that provides your computer with the capability to view or play a specific type of file. For example.ra files require the RealAudio player, otherwise you would not be able to view the file. Web Authoring and Site Management It means that you can use the Web to publish your own Web pages, rather than only accessing information and interact with other users. Some terms you need to understand: Web Publishing: refers to when you create a single Web page or several pages (a Web site) and you put them in a Web server, so that everyone with Internet access can view their content. HTML: stands for Hyper-Text Markup Language. It is the format of the Web page file, which contains special instructions that tell Web browsers how to display the text, graphics, and background on the screen. The elements in the Web page cannot be changed while it is being viewed. HTML Tag: is a HTML instruction that is inserted into the text of the document and they usually come in pairs (Check out an example in the book).

8 DHTML: stands for Dynamic HTML. It allows elements of a Web page to be changed while the page is being viewed. XML: stands for extensible Markup Language. Allows the person who develops a Web page to define customized tags to produce effects not available with standard HTML. HTML Authoring Tools and Web Page Design Tips To create an HTML document, you can hard code it yourself with a text editor, such as the Notepad from Windows. However, you can use tools that will let you create quicker Web pages for your Web site in a matter of minutes. Popular Web authoring software titles include Microsoft FrontPage and Claris Home Page. There are other web authoring tools that you could use instead that are much cheaper, and others are even free (Netscape Composer). Having the right tools to design a Web site is important, but they can t replace good planning. Here are some tips to design a Web page (or site): Plan your Web page so that it fulfills its purpose Design a template to unify your pages Follow basic rules for good Web page design o Maintain narrow line widths (use text in columns, rather than everything in one line). o Proofread your pages

9 o Use contrasting colors for text and background o Avoid drab gray as your background, but don t let background colors or graphics overpower your text o Use small graphic files, unless your site is going to be specifically about image processing and such (30 KB) o Use graphics with.gif or.jpg filename extensions o Present a large graphic as a small thumbnail with a link to the larger version of it. Identify your pages (the TITLE HTML tag) Include dates Plan your pages (Establish a navigational hierarchy) Include Navigation Elements Respect the copyright and intellectual property rights of other Web sites. Publishing your Pages After you finish creating your individual pages with their links and all their elements, you need to: Test each page locally Transfer pages to a Web server Test all links Update your site to keep it current

10 Building an E-commerce site E-commerce refers to buying products and services by means of the Internet. Places such as Amazon.com and Can you create an e-commerce site? The answer is yes, and you don t have to be a big company to do so. It can be as simple as displaying the products that you want to sell in your Web site with a telephone number to place an order. Or, it could hire professional companies to build and lease you an e-commerce site for as low as $40 per month.