Introduction to Internet

Transcription

1 Introduction to Internet 1) INTRODUCTION: ) WHAT IS THE INTERNET? ) HISTORY & DEVELOPMENT OF THE INTERNET: ) WHO PAYS FOR THE INTERNET? ) WHAT MAKES THE INTERNET WORK? ) THE CLIENT/SERVER MODEL: ) THE USE OF LOCAL CLIENTS: ) ELECTRONIC MAIL ON THE INTERNET: ) HOW DOES WORK? ) READING AN INTERNET ADDRESS: ) TYPES OF DISCUSSION LISTS: ) INTRODUCTION TO NETWORK NEWS: ) HOW DOES NETWORK NEWS WORK? ) NEWSGROUPS: WHAT'S IN A NAME? ) REMOTE LOGIN & FILE TRANSFER: ) INTRODUCTION TO FTP, FILE TRANSFER PROTOCOL: ) RESOURCES AVAILABLE TO YOU VIA FTP ) INTRODUCTION TO GOPHER: ) INTRODUCTION TO THE WORLD WIDE WEB ) WHAT MAKES THE WWW WORK? ) UNIFORM RESOURCE LOCATORS, OR URLS: ) WWW CLIENTS, OR "BROSWERS": ) CHATTING: ) A LOOK AT SEARCH ENGINES:... 13

2 1) Introduction: By the turn of the century, information, including access to the Internet, will be the basis for personal, economic, and political advancement. The popular name for the Internet is the information superhighway. Whether you want to find the latest financial news, browse through library catalogs, exchange information with colleagues, or join in a lively political debate, the Internet is the tool that will take you beyond telephones, faxes, and isolated computers to a burgeoning networked information frontier. The Internet supplements the traditional tools you use to gather information, Data Graphics, News and correspond with other people. Used skillfully, the Internet shrinks the world and brings information, expertise, and knowledge on nearly every subject imaginable straight to your computer. 2) What is the Internet? The Internet links are computer networks all over the world so that users can share resources and communicate with each other. Some computers, have direct access to all the facilities on the Internet such as the universities. And other computers, eg privatelyowned ones, have indirect links through a commercial service provider, who offers some or all of the Internet facilities. In order to be connected to Internet, you must go through service suppliers. Many options are offered with monthly rates. Depending on the option chosen, access time may vary. The Internet is what we call a metanetwork, that is, a network of networks that spans the globe. It's impossible to give an exact count of the number of networks or users that comprise the Internet, but it is easily in the thousands and millions respectively. The Internet employs a set of standardized protocols which allow for the sharing of resources among different kinds of computers that communicate with each other on the network. These standards, sometimes referred to as the Internet Protocol Suite, are the rules that developers adhere to when creating new functions for the Internet. The Internet is also what we call a distributed system; there is no central archives. Technically, no one runs the Internet. Rather, the Internet is made up of thousands of smaller networks. The Internet thrives and develops as its many users find new ways to create, display and retrieve the information that constitutes the Internet. 3) History & Development of the Internet: In its infancy, the Internet was originally conceived by the Department of Defense as a way to protect government communications systems in the event of a military strike. The original network, dubbed ARPANet (for the Advanced Research Projects Agency that

3 developed it) evolved into a communications channel among contractors, military personnel, and university researchers who were contributing to ARPA projects. The network employed a set of standard protocols to create an effective way for these people to communicate and share data with each other. ARPAnet's popularity continued to spread among researchers, and in the 1980's the National Science Foundation, whose NSFNet, linked several high speed computers, took charge of the what had come to be known as the Internet. By the late 1980's, thousands of cooperating networks were participating in the Internet. In 1991, the U.S. High Performance Computing Act established the NREN (National Research & Education Network). NREN's goal was to develop and maintain high-speed networks for research and education, and to investigate commercial uses for the Internet. The rest, as they say, is history in the making. The Internet has been improved through the developments of such services as Gopher and the World Wide Web. Even though the Internet is predominantly thought of as a research oriented network, it continues to grow as an informational, creative, and commercial resource every day and all over the world. 4) Who Pays for the Internet? There is no clear answer to this question because the Internet is not one "thing", it's many things. No one central agency exists that charges individual Internet users. Rather, individuals and institutions who use the Internet pay a local or regional Internet service provider for their share of services. And in turn, those smaller Internet service providers might purchase services from an even larger network. So basically, everyone who uses the Internet in some way pays for part of it. 5) what makes the internet work? The unique thing about the Internet is that it allows many different computers to connect and talk to each other. This is possible because of a set of standards, known as protocols, that govern the transmission of data over the network: TCP/IP (Transmission Control Protocol/Internet Protocol). Most people who use the Internet aren't so interested in details related to these protocols. They do, however, want to know what they can do on the Internet and how to do it effectively.

4 6) The Client/Server Model: The most popular Internet tools operate as client/server systems. You're running a program called a Web client. This piece of software displays documents for you and carries out your requests. If it becomes necessary to connect to another type of service-- say, to set up a Telnet session, or to download a file--your Web client will take care of this, too. Your Web client connects (or "talks") to a Web server to ask for information on your behalf. The Web server is a computer running another type of Web software which provides data, or "serves up" an information resource to your Web client. All of the basic Internet tools--including Telnet, FTP, Gopher, and the World Wide Web- -are based upon the cooperation of a client and one or more servers. In each case, you interact with the client program and it manages the details of how data is presented to you or the way in which you can look for resources. In turn, the client interacts with one or more servers where the information resides. The server receives a request, processes it, and sends a result, without having to know the details of your computer system, because the client software on your computer system is handling those details. The advantage of the client/server model lies in distributing the work so that each tool can focus or specialize on particular tasks: the server serves information to many users while the client software for each user handles the individual user's interface and other details of the requests and results. 7) The Use of Local Clients: Every computer should be equipped with basic client software packages that allow you to perform functions such as electronic mail, Telnet, Gopher, and FTP. 8) Electronic mail on the internet: Electronic mail, or , is probably the most popular and widely used Internet function. , , or just mail, is a fast and efficient way to communicate with friends or colleagues. You can communicate with one person at a time or thousands; you can receive and send files and other information. You can even subscribe to electronic journals and newsletters. You can send an message to a person in the same building or on the other side of the world.

5 9) How does Work? is an asynchronous form of communication, meaning that the person whom you want to read your message doesn't have to be available at the precise moment you send your message. This is a great convenience for both you and the recipient. On the other hand, the telephone, which is a synchronous communication medium, requires that both you and your listener be on the line at the same time in order for you to communicate (unless you leave a voice message). It will be impossible to discuss all the details of the many packages available to Internet users. Fortunately, however, most of these programs share basic functionality which allow you to: *send and receive mail messages *save your messages in a file *print mail messages *reply to mail messages *attach a file to a mail message 10) Reading an Internet Address: To use Internet successfully, you must understand how the names and addresses for computers and people on the Internet are formatted. Mastering this technique is just as important as knowing how to use telephone numbers or postal addresses correctly. Fortunately, after you get the hang of them, Internet addresses are usually no more complex than phone numbers and postal addresses. And, like those methods of identifying a person, an organization, or a geographic location--usually by a telephone number or a street address--internet addresses have rules and conventions for use. Sample Internet Address: custcare@aucegypt.edu The Internet address has three parts: 1. a user name [custcare in the example above] 2. an "at" sign (@)

6 3. the address of the user's mail server [aucegypt.edu in the example above] Sometimes it's useful to read an Internet address (like or a domain name from right to left because it helps you determine information about the source of the address. An address like 201B6DQF@asu.edu doesn't tell me much about the person who's sending me a message, but I can deduce that the sender is affiliated with an educational institution because of the suffix edu. The right-most segment of domain names usually adhere to the naming conventions listed below: EDU Educational sites in the United States COM Commercial sites in the United States GOV Government sites in the United States NET Network administrative organizations MIL Military sites in the United States ORG Organizations in the U.S. not covered by the categories above (e.g., non-profit orginaizations)..xx where xx is the country code (e.g.,.gr for Greece). Introduction: Once you've become adept at using , you may want to communicate with others on the Internet who share your interests. Newsgroups are one way to do this; the other is through an electronic discussion group. An electronic discussion is a group of persons who have come together to discuss a particular topic via . There are several methods that network users can use to participate in electronic discussions; however, the basic purpose is to bring together persons with similar interests to share information, ideas, problems, solutions, and opinions. Since an electronic discussion is conducted by , it's commonly called a mailing list. If you find yourself interested in a topic, you can subscribe to a suitable mailing list. From then on, any message sent to the mailing list is automatically distributed as electronic mail to you--as well as to all previously subscribed members of that particular

7 discussion. The beauty of a mailing list is that traffic (the mail generated by that list) covers a specific topic and the mail it generates comes straight to your electronic mailbox, without any extra work on your part. There are thousands of mailing lists operating on the Internet, dedicated to myriad topics. Some are created to serve local needs only (i.e., a list for the members of a regional computer user group), while many are open to anyone on the network. There are discussions on professional topics, vocational subjects, and topics of personal interest. You can roughly separate the thousands of mailing lists available on the Internet into the following groups: 11) Types of discussion lists: Moderated vs. Unmoderated Lists Mailing lists can be moderated or unmoderated. The distinction is whether messages are automatically forwarded to all subscribers (unmoderated) or whether a moderator (a human being) first screens and perhaps combines similar messages before sending them to subscribers (moderated). Open vs. Closed Lists Electronic discussions can also be "open" or "closed." Anyone can subscribe to an open discussion, but a closed discussion is limited to a particular group of persons, for example, those in a particular professional field. 12) Introduction to network news: Network News (sometimes referred to as Usenet News) is a service comprised of several thousand electronic discussions providing users an effective way to share information with others on just about any topic. If you're unclear about the concept of Network News, it's helpful to think about a bulletin board that you might see on campus. Here, one might find posted messages advertising a futon for sale, asking for students to join a math study group. In the newsgroup environment, the same kind of process take place: User X may access a newsgroup on a particular topic and post a message, question, or respond to a previously posted message, and anyone accessing that newsgroup would then be able to see User X's message.

8 Network News newsgroups provide this same kind of forum online, where users have access to the messages posted by all other users of that newsgroup. Network News has been described as an "international meeting place" where you're likely to find a discussion going on just about anything. 13) How Does Network News work? Messages posted on Network News newsgroups are sent from host computer to host computer all over the world, using the network news transfer protocol. Because Network News newsgroups are located on one server, Network News is a very efficient way to share information that might otherwise be disseminated to several individual users. This way, several people can read a given newsgroup message, but the host system stores only one copy of it. 14) Newsgroups: What's in a Name? As mentioned before, Network News is essentially made up of newsgroups, each newsgroup a collection of messages focusing on a related theme. You can probably find a newsgroup on any topic, no matter how arcane or bizarre. A newsgroup's name gives you a good idea of that group's focus, and also illustrates the hierarchical naming scheme given to newsgroups. Newsgroups with the prefix comp, for example, are for computer-related topics. After the initial prefix, you'll see an additional series of names assigned to the newsgroup that tell its specific concern: Note the following examples: comp.mac.performa for "computers--macintosh--performas" rec.auto.antique for "recreation--autos--antiques" alt.backrubs for "alternative--backrubs" soc.culture.japan for "social--culture--japan"

9 15) Remote Login & File Transfer: Introduction to telnet: Telnet is the protocol used to establish a login session on a remote computer on the network. While many computers on the Internet require users to have authorization, others are open to the public and can be logged onto with telnet. Telnet is not a method to transfer files from one machine to another, but rather is a way to remotely connect to another system with priveleges to run specific programs on that system. Some uses of the Telnet protocol include: connecting to a library catalog to search that library's collection connecting to a location that allows public priveleges to search its campus information system connecting to a location that gives you an up-to-the minute weather report Basic Telnet Commands open - establishes a connection to the specified host.close - closes an open connection and leaves you in the telnet software quit - closes any open telnet sessions and exits the telnet software. When using a telnet program like NCSA Telnet, you invoke these commands by way of pull-down menus or command keys. 16) Introduction to FTP, File Transfer Protocol: Basic commands in FTP: To do FTP, a user invokes one of two commands: get the command for transferring a file from another server to your own computer. put the command for moving a file from your computer to another one. Who can do FTP? Anonymous vs. authorized priveleges On many servers, called anonymous FTP servers, anyone can do FTP. All that is required to login is a username (anonymous) and a password (your address). To get an idea of the many resources available via FTP, you can look at this selected list of FTP servers. Other servers require you to be a registered "authorized" user before you're permitted to do FTP. In such a case, you would need to contact the system operator for the server you wish to access, and request an authorization and a password. Getting an authorization and password might mean that you can get and put only to specific subdirectories on that server.

10 17) Resources available to you via FTP Freeware When you download freeware, the author continues to carry the copyright to the software, but permits you to use the program for free. You can share freeware with others, as long as you don't sell it. Public Domain When you download public domain software, you can use it freely. The creator carries no copyright, and has released it for anyone to use. There are no limits on distribution or sale--and anyone can modify the program. Shareware When you download shareware, the author continues to carry the copyright to the software, but you're permitted short-term use of the program for evaluation purposes. At the end of evaluation period, you must either pay the copyright holder for the program or destroy all copies you've made of it. 18) Introduction to Gopher: Gopher is a client/server system that allows you to access many Internet resources simply by making selections from a sequence of menus. Each time you make a selection, Gopher carries out your request to the computer that contains the information and "serves" it up. For example, if you select a menu item that represents a text file, Gopher will get that file--wherever it happens to be--and display it for you. As you use Gopher, some menu items lead to other menus. If you choose one of these, Gopher will retrieve the new menu and display it for you. Thus you can move from menu to menu, using only a few key strokes or a mouse to navigate. The power of Gopher is that the resources listed in a menu may be anywhere on the Internet. As Gopher connects to computers to comply with your menu selection, you don't need to be preoccupied with the behind-the-scenes work of connecting to and disconnecting from these various computers. Gopher does this for you without your even needing to be aware of it. This automatic connecting makes Gopher popular and useful. Where did Gopher come from? "Born" in April 1991, gopher began as a project at the Microcomputer, Workstation, and Networks Center at the University of Minnesota to help people on campus get answers to computer-related questions. At the time, the computer center staff had accumulated answers to thousands of questions regarding computers and software.

11 What was needed was an easy and efficient way to deliver this information to students, faculty and staff. Thus, the creation of Gopher reaffirms the adage that necessity is the mother of invention. Why is it called Gopher? The name "Gopher" is appropriate for three reasons: 1. Just as a real gopher successfully navigates beneath the prairie, the Internet Gopher tunnels through the invisible paths of the Internet to help you find the information you want. 2. The name refers to someone who fetches things or provides service for other people. 3. The Golden Gopher is the mascot of the University of Minnesota. 19) Introduction to the World Wide Web The World Wide Web (also referred to as WWW or W3) is the fastest growing area of the Internet. While gopher was an important step in allowing users to "browse" through the Internet's vast resources, the World Wide Web has raised excitement about the Internet to new heights. What makes the World Wide Web appealing and innovative is its use of hypertext as a way of linking documents to each other. A highlighted word or phrase in one document acts as a pointer to another document that amplifies or relates to the first document. When looking at a WWW document, the reader doesn't have to follow every pointer, or link (also called a hypertext link), only those that look interesting or useful. In this way, the user tailors the experience to suit his or her needs or interests. The other very appealing aspect of the World Wide Web is the use of graphics and sound capabilities. Documents on the WWW include text, but they may also include still images, video, and audio for a very exciting presentation. People who create WWW documents often include a photograph of themselves along with detailed professional information and personal interests. (This is often called a person's home page.) 20) What makes the WWW work? WWW is another example of client/server computing. Each time a link is followed, the client is requesting a document (or graphic or sound file) from a server (also called a Web server) that's part of the World Wide Web that "serves" up the document. The server uses a protocol called HTTP or HyperText Transport Protocol. The standard for creating

12 hypertext documents for the WWW is HyperText Markup Language or HTML. HTML essentially codes plain text documents so they can be viewed on the Web. 21) Uniform Resource Locators, or URLs: A Uniform Resource Locator, or URL is the address of a document you'll find on the WWW. Your WWW browser interprets the information in the URL in order to connect to the proper Internet server and to retrieve your desired document. Each time you click on a hyperlink in a WWW document, you're actually instructing your browser to find the URL that's embedded within the hyperlink. The elements in a URL:Protocol://server's address/filename Hypertext protocol: Gopher protocol: gopher://gopher.umm.tc.edu File Transfer Protocol: ftp://ftp.dartmouth.edu Telnet Protocol: telnet://pac.carl.org News Protocol: news:alt.rock-n-roll.stones 22) WWW Clients, or "Broswers": The program you use to access the WWW is known as a browser because it "browses" the WWW and requests these hypertext documents. Browsers can be graphical, like Netscape and Mosaic, allowing you to see and hear the graphics and audio; text-only browsers (i.e., those with no sound or graphics capability) are also available. All of these programs understand http and other Internet protocols such as FTP, gopher, mail, and news, making the WWW a kind of "one stop shopping" for Internet users. 23) Chatting: Internet Relay Chat (IRC), the other method for Internet conversation, is less common than talk because someone must set up the Chat before others can join in. Chat sessions allow many users to join in the same free-form conversation, usually centered around a discussion topic. When users see a topic that interests them, they type a command to join

13 and then type another command to choose a nickname. Nicknames allow people in the session to find you on IRC Networks or Channels. 24) A look at search engines: The World Wide Web is "indexed" through the use of search engines, which are also referred to as "spiders," "robots," "crawlers," or "worms". These search engines comb through the Web documents, identifying text that is the basis for keyword searching. Each search engine works in a different way. Some engines scan for information in the title or header of the document; others look at the bold "headings" on the page for their information. The fact that search engines gather information differently means that each will probably yield different results. Therefore, it's wise to try more than one search engine when doing Web searching. The list below lists several search engines and how each one gathers information, plus resources that evaluate the search engines. Selected Search Engines (listed alphabetically) Google The most famous search engine currently. Enables users to search the Web, Usenet, and images. Features include PageRank, caching and translation of results, and an option to find similar pages Alta Vista Alta Vista, maintained by The Digital Equipment Corp., indexes the full text of over 16 million pages including newsgroups. Check out the Alta Vista Tips page. Excite Netsearch Excite includes approximately 1.5 million indexed pages, including newsgroups. Check out the Excite NetSearch handbook. InfoSeek Net Search Indexes full text of web pages, including selected newsgroups and electronic journals. Just under one-half million pages indexed. Check out the InfoSeek Search Tips. Inktomi

14 As of December 1995, the Inktomi search engine offers a database of approximately 2.8 million indexed Web documents and promises very fast search retrievals. Results are ranked in order of how many of your searched terms are used on the retrieved pages. Lycos Lycos indexes web pages (1.5 million +), web page titles, headings, subheadings, URLs, and significant text. Search results are returned in a ranked order. Magellan Magellan indexes over 80,000 web sites. Search results are ranked and annotated. Open Text Index Indexes full text of approximately 1.3 million pages. Check out the Open Text Help pages for tips on using this search engine. WebCrawler Maintained by America Online, WebCrawler indexes over 200,000 pages on approximately 75,000 web servers. URLs, titles, and document content are indexed. WWWW -- World Wide Web Worm Approximately 250,000 indexed pages; indexed content includes hypertext, URLs, and document titles. Yahoo A favorite directory and search engine, Yahoo has organized over 80,000 Web sites (including newsgroups) into 14 broad categories. Yahoo also maintains a comprehensive list of links to Yahoo - Computers and Internet:Internet:World Wide Web: Searching the Web other web search engines, indexes, and guides. Finally the internet is a huge source of information in all fields of knowledge.