Internet and the World Wide Web n n

Internet and the World Wide Web

n n The Internet is made up of more than 100, 000 interconnected networks in over 100 countries, comprised of commercial, academic and government networks. From the user’s point of view, the Internet is a way of connecting to essentially any other machine on the network.

Main Uses of the Internet n n n electronic mail (email) World Wide Web newsgroups and bulletin boards chat rooms and instant messaging telnet ftp

Email n n Uses mail composing and reading programs (e. g. , MS Outlook) Email can be sent directly from many Microsoft applications like Word and Excel, with the corresponding documents or spreadsheets included as attachments.

World Wide Web n n Provides a standardized way for information residing on one computer (the web server) to be downloaded and read by another computer (the client). The file(s) to be downloaded from the server use HTML (hypertext markup language), and the downloading takes place using HTTP (hypertext transfer protocol).

n n n On the client computer, a web browser is used to display the information contained in the downloaded files. The most commonly used web browsers are Netscape and Internet Explorer. Web pages can provide access to a wide variety of information, all of which can potentially be downloaded to any computer.

n Usenet (User Network) newsgroups, which allow anyone to post messages and read everyone else’s postings, have been around since long before the Web was created.

n n These newsgroups are organized around specific subjects of interest to particular subscribers. Newsgroups can be selected and read directly from your Web browser.

n n n Chat rooms provide another popular Internet service. Internet Relay Chat (IRC) offers multiuser text conferencing on diverse topics. Dozens of IRC servers provide hundreds of channels that anyone can log onto and participate in via the keyboard.

Internet Access n n Today, all the major online services provide full Internet access. In addition, thousands of Internet service providers (ISPs) have risen out of the woodwork to offer individuals and organizations access.

TCP/IP n n All data is transmitted along the Internet using what is called TCP/IP. TCP stands for Transmission Control Protocol and IP stands for Internet Protocol.

n These protocols were developed by DARPA (Defense Advanced Research Projects Agency) to enable communication between different types of computers and computer networks, back when what is now the Internet was just a small collection of widely distributed experimental networks known as the ARPAnet.

n n The Internet Protocol is a connectionless protocol which provides packet routing. A packet is a unit of data formatted for transmission on a network.

n n Data is broken up into packets for sending over a packet switching network. All the data packets making up a single message may not take the same route to get to their destination; they are reassembled once they have arrived.

Internet Services n Although most new users interact with the Internet via their Web browsers, for years, command-line UNIX utilities have been used.

n For example, an FTP (File Transfer Protocol) program allows files to be transferred between machines.

n n Telnet is a terminal emulation program that lets you log onto a computer in the Internet and run a program, assuming you have an account that lets you access that computer. Note: In the CCS labs, use F-Secure SSH, which is a more secure version of telnet.

World Wide Web n n The World Wide Web is an Internet facility that links documents locally and remotely. The Web document is called a Web page, and links in the page let users jump from page to page (hypertext) whether the pages are stored on the same server or on servers around the world.

n The fundamental Web format is a text document embedded with HTML (Hypertext Markup Language) tags that provide the formatting of the page as well as the hypertext links (URLs-Uniform Resource Locators) to other pages.

n HTML codes are common alphanumeric characters that can be typed with any text editor or word processor.

n Numerous Web publishing programs, such as Frontpage, provide a graphical interface for Web page creation and automatically generate the codes.

n Many word processors, such as Word, and publishing programs also export their existing documents to the HTML format, allowing Web pages to be created by users without learning any coding system.

n Web pages are maintained at Web sites, which are computers that support the Web's HTTP (Hypertext Transfer Protocol) protocol.

n n When you access a Web site, you generally first link to its home page, which is an HTML document that serves as an index to the site's contents. Large organizations create and manage their own Web sites. Smaller ones have their sites hosted on servers run by their Internet service providers (ISPs).

n n Many individuals have developed personal Web home pages since many ISPs include this service with their monthly access charge. Individuals can post their resumes, hobbies and whatever else they want as a way of introducing themselves to the world at large.

How to transfer a file over the Internet n n n There are two ways to transfer files over the Internet. One is to send a file along with an email message, and the other is to use an FTP program.

Via E-mail n E-mail programs have the ability to "attach a file" to a message, which means that any type of file (program, graphics, spreadsheet, etc. ) can be transmitted along with the text message.

n n n This is the simplest way to send a file via the Internet. However, although widely used, it can be problematic. Old e-mail programs, light versions of email programs and some mail gateways can cause problems.

n n The standard Internet mail protocol supports only text. And if the computer receiving the message does not have the Word program, for example, an attached Word document will be unreadable by the recipient.

Sending files via FTP and the Web n . The protocol on the Internet that was designed to handle file transfers is FTP (file transfer protocol).

n n With a Web browser, you can download from an FTP site. You would use the ftp: // prefix and address (URL), which includes the domain name and directories.

Internet addresses n n There are two kinds of addresses that are widely used on the Internet. One is a person's e-mail address, and the other is the address of a Web site, which is known as its URL.

n The format for addressing an email message to an Internet user is USER NAME @ DOMAIN NAME.

n n For example, your address might be ldecaprio@lynx. neu. edu. There are no spaces between any of the words. ldecaprio is the user name and lynx. neu. edu is the domain name. The. edu stands for the academic top level domain category.

How to Find Someone Else's Address n n There are Web sites that maintain directories, or white pages, of e-mail addresses. New sites are coming online all the time. You may have to try several sites to find someone, and there's no guarantee. In the meantime, check out:

n n n www. bigfoot. com www. four 11. com www. whowhere. com www. switchboard. com www. infospace. com

IP address n n An Internet Protocol address is the physical address of a computer attached to a TCP/IP network. Every client and server station must have a unique IP address.

n Client workstations have either a permanent address or one that is dynamically assigned to them each dialup session. IP addresses are written as four sets of numbers separated by periods; for example, 204. 171. 64. 2.

URL n n Uniform Resource Locator is the address that defines the route to a file on the Web or any other Internet facility. URLs are typed into the browser to access Web pages, and URLs are embedded within the pages themselves to provide the hypertext links to other pages.

n For example, http: //www. ccs. neu. edu retrieves the home page of the College of Computer Science Web site. The http: // is the Web protocol, and www. ccs. neu. edu is the domain name.

n n If the page is stored in another directory, or if a page other than the home page is required, slashes are used to separate the names. For example, http: //www. ccs. neu. edu/index. html points to the index page.

n n n If a required page is stored in a subdirectory, its name is separated by a slash. Like path names in DOS and Windows, subdirectories can be several levels deep. For example, the components of the following hypothetical URL are described below:

n n n http: //www. abc. com/clothes/shirts/formal. ht ml means the following: http: // protocol www. abc. com/ domain name clothes/ subdirectory name shirts/ subdirectory name formal. html document or file name

Internet domain names n n An Internet domain name is an organization's unique name combined with a top level domain name (TLD). For example, ccs. neu. edu is the domain name of the College of Computer Science.

n n n n The following are the top level domains (the. edu, . mil and. gov domains are traditionally U. S. domains). . commercial. net gateway or host. org non-profit organization. educational and research. government. military agency. international intergovernmental

n n The. int domain name is not widely used. Outside of the U. S. , the top level domains are typically the country code; for example, uk for United Kingdom.

Country code n n n A country code is a two-character component of an e-mail or Web address that identifies a country. Web servers read addresses from right to left. So, on encountering sven@univ. oslo. net. se, the message would first be sent to Sweden, since se is the country code for Sweden.

n Swedish routers would then send the message to univ. oslo. net where it will be waiting for Sven the next time he logs on.

Search Engines and Sites n n There are various Web sites that maintain databases about the contents of other Web sites. Most sites are free and are paid for by advertising banners, while others charge for the service.

n Some of the best known search sites are: n n n Yahoo! Lycos Infoseek Altavista There are many others. Here is a more complete list of such sites:

n n n n n www. altavista. digital. com www. excite. com www. hotbot. com www. infoseek. com www. lycos. com www. metacrawler. com www. opentext. com www. search. com www. webcrawler. com www. yahoo. com

Special-Purpose Search Sites n n n Following are popular sites for searching specific topics. For example, Four 11 searches a database of the nation's white pages for phone numbers and addresses. Deja News searches a database of postings to Usenet newsgroups:

n n Authors & Books, www. amazon. com Automobile Buyers Guides, www. edmunds. com Book Reviews, www. nytimes. com/books Business News, www. wsj. com

n n n Computer Supersite, www. cmp. com Computer Supersite, www. cnet. com Computer Supersite, www. zdnet. com Consumer Info, www. consumerworld. org Education & Career Info, www. petersons. com

n n Government (U. S. ), http: //thomas. loc. gov Health & Medicine, www. healthatoz. com Jobs & Careers, www. occ. com Legal Resources, www. findlaw. com

n n Literature (Great Works), www. promo. net/pg Mailing Lists (Internet), www. liszt. com Maps & Driving Directions, www. mapquest. com Microsoft Support, www. microsoft. com/support

n n Music & Videos, www. cdnow. com Newsgroups (Usenet), www. dejanews. com Package Tracking & Drop Offs, www. fedex. com Package Tracking & Drop Offs, www. ups. com

n n n Parenting Library, www. parentsoup. com Recipes & Cooking, www. epicurious. com Research, www. clearinghouse. net Research, www. elibrary. com Restaurant Menus, www. menusonline. com

n n n n Shareware, www. shareware. com Shareware, www. softseek. com Subculture, www. disinfo. com Tax Forms, www. 1040. com White Pages (people), www. four 11. com Yellow Pages (business), www. zip 2. com Zipcodes, www. usps. gov

Microsoft Internet Explorer n n Internet Explorer (IE) is a Web browser from Microsoft that runs under Windows 95/98/NT, Mac and UNIX. In Windows 98, Internet Explorer is fully integrated into the desktop.

How to download a picture from the Web Point to the picture and right click. n Select Save Picture As from the menu. n Specify the name (and location) of the file where you want the picture to be saved. This picture file is then available to be inserted into a Word document or a Power. Point presentation, for example. n

Cache n n While you explore the Web, your browser is working behind the scenes, keeping track of the sites you've visited, and even saving images from these pages on your hard disk so they'll load faster when you return. The saved files are collectively referred to as your "temporary Internet files" (or more broadly termed, your disk cache).

Browsing speed n n Having Web pages and files (such as graphics) stored on your desktop computer allows you to open pages you frequently visit, and have already seen, a lot faster, since you can open them from your hard disk instead of from the Internet. This capability also makes it easy for you to save money because you can view Web files without being connected to the Internet.

IE disk cache operations n To empty your IE cache, or change the amount of disk space allocated for it: n n On the View menu of your IE toolbar, click Options. In the resulting dialog box, click the Advanced tab. In the Temporary Internet Files area, click Settings. The remaining step should then be obvious.

Cookies n A cookie is a set of data that a website server gives to a browser the first time the user visits the site, that is updated with each return visit.

n n The remote server saves the information the cookie contains about the user and the user's browser does the same, as a text file stored in the Netscape or Explorer system folder. Not all browsers support cookies.

n Cookies store information such as user name and password and what parts of the site were visited; this information can be updated with each visit

n The browser only shares each cookie with the server that originated it; other servers can only read their own cookies.

n n I. E. 4. 0 can be set up to alert the user when a cookie is being sent so the user can accept it or not, by means of the Network Preferences window. There also downloadable applications that eat cookies such as Cookie Killers, Cookie Monster (Mac), and Kill Cookie Batch File (PC).

n n n A good illustration of how cookies are used can be found in various movie links. They provide information about movie times at theaters in cities across the country. The first time you visit their site, the link asks you to type in your zip code to let them know where you are.

n n The next time you visit, the site automatically knows to show you information about theaters and show times in your area. That saves you from having to log in multiple times and from having to enter your interests multiple times. That saves you time.

n Basically, the site uses a cookie to customize the experience for you.

n Because of this ability to customize according to your areas of interest, some people fear that cookies somehow invade their privacy.

n n In many ways, a cookie provides an added level of privacy By storing information on your own computer rather than Internet servers, you can examine the data files and see exactly which information is being recorded by the Internet service using cookies.

Viruses on the Net n n n Once you log on to the Internet, you're entering a vast online society. And, as in human society, not everyone there is nice. Threats to security exist in the online world, just as they do in the rest of the world. By learning to protect yourself – your computer and your data – you'll ensure that your time online is productive and fun.

n n n You've probably heard dire warnings about the possibility of downloading a computer virus from the Internet. Don't ignore them. The truth is that there are viruses, and they can be destructive. Fortunately, by following a few easy guidelines and using some common sense, you can keep your computer virus-free.

n n You can pick up a computer virus only when you interact with another computer. So when you're downloading free software from the Internet, sharing files with friends, or even transferring files from work to home, take the precautions outlined below, and your computer and your data should stay reasonably safe.

Know your source! n n On the Internet, knowing a source means downloading files only from Web sites you know to be safe. Generally, this warning applies to program files or applications because viruses are most often hidden within programs and become activated only when the programs are run.

n n However, executable files can also be attached to special-action Web files, video files, active software agents, and email messages. Generally you will see a warning message on your screen whenever such an application is about to be downloaded.

n n When downloading a file, you will be presented with the choice to open it or save it to disk. If you aren't sure an application is safe, or you don't know whether you can trust the site it is coming from, you might want to cancel the download at this opportunity.

Immunize your computer n n n Many anti-virus programs are available that function, in effect, like virtual inoculations against known viruses. Make sure you have an up-to-date anti-virus program on your computer and use it. But also be aware that new viruses are constantly being developed, so you need to update your anti-virus programs frequently.