The Internet
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THE INTERNET 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. The main high capacity routes of the Internet are referred to as the Internet backbone. Communication between all of the different devices on the Internet is made possible by TCP/IP (Transmission Control Protocol/ Internet Protocol). Internet Connections What are my options for Internet connections? • Existing telephone line • Cable television line • Personal satellite link • Wireless or cell phone service • High-speed telephone services – ISDN, DSL User ID’s and Passwords • A user ID is a series of characters that becomes a person’s unique identifier • A password is a different series of characters that verifies your identity • Some computers are case-sensitive; they differentiate between upper and lower case letters • To minimize memorizing 40 user ID’s and passwords, pick a unique user ID that you can use with every system • Pick 2 passwords, one for high security, and one for low security – Use high security password for critical data and low security for non-critical data Where is all of the Internet data stored? • It is estimated that the Internet provides access to more data than is stored in all the academic research libraries in the U. S. • Most of the information is stored on servers which are owned and maintained by government agencies, corporations, small businesses, schools, organizations, and even individuals What sort of resources does the Internet provide? • Web Sites – various locations in cyberspace that correspond to a corporation, a store, a magazine, and more • Search engines – help catalog a huge portion of the data stored on servers that are connected to the Internet • E-commerce – online activities such as banking and shopping • E-mail – electronic messages – Mailing list server • Bulletin boards – discussion groups – Usenet – Newsgroups • Downloads and uploads – Downloading – Uploading What is a search engine? Search engine popularly refers to a Web site that provides a variety of tools to help you find information – A software program that helps you locate web pages on certain topics – Enter keywords or descriptions – AltaVista, Google, Yahoo, etc. You look for information submitting a query. Exactly what is a query? • Describes information you want to find • You can enter more than one search term. Separate each term with a space or search operator – A search operator is a word or symbol that describes a relationship between keywords and thereby helps you create a more focused query • AND, OR, and NOT • Quotation marks • NEAR • Wildcards • Field Searches 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. Internet Service Providers (ISP) They are the companies that maintain 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. According to the type a connections offered, they need to have the corresponding hardware. – An ISP that offers dial-up connections, for example, maintains a bank of modems – AOL, Earthlink, are examples of ISPs, and so is MSU 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: 204.146.144.253 131.98.45.120 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 204.140.144.253? 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) 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 http://. 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. For Example: My Website is at the Web Server www.csam.montclair.edu. 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 www.csam.montclair.edu/~gutierre 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 (remember lab #2) to send or receive available files. There are also Usenet servers and IRC servers (Internet Relay Chat servers) that 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, i.e., they provide Internet users with all-purpose client software for accessing many types of servers. The most frequently used are: Internet Explorer Netscape Mozilla (Note that the general browser is Mozilla. Mozilla Firefox is not a general purpose browser) 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. 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 e-mail 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.