Technology Infrastructure: The Internet and the World Wide Web Week of June 10 – June 16 The History of the Internet: o A computer network is a group of computers connected to one another in order to exchange information. The Internet is a large system of interconnected computers that open the world (p. 53). o The Internet’s existence dates back to the 1960s. The U.S. Department of Defense funded the creation of a worldwide network of computers that could survive even if a portion of the network were to be destroyed. Their efforts led to ARPANET in 1969 (p. 54). o In 1972, e-mail was invented (p. 54). o In the 1970s and 1980s, the focus of the Internet moved from military applications to academic research functions (p. 53). o In 1989, MCI Mail and CompuServe were allowed to offer e-mail services to individual citizens, greatly expanding the scope of the Internet (p. 55). o Also in 1989, Tim Berners-Lee developed a hypertext server program. Hypertext is a concept in which documents could be stored in a non-sequential, non-linear fashion and one document can be accessed from another through the use of links (p. 57). Could you imagine the Internet without hypertext? Without it, you would have to read through all of the pages of the Internet in order, one after another, in much the same way you would read a book. With it, you can jump from one page precisely to the next page you would like to see by simply clicking a link. Berners-Lee also developed HyperText Markup Language (HTML). HTML is the language in which all Web pages are coded today (p. 58). o Despite the emergence of HTML, very few people could read it. In 1993, a group of students at the University of Illinois wrote a program for rendering HTML on the screen in a graphical format (p. 59). This program eventually became the Netscape Navigator Web browser. Shortly thereafter, Microsoft introduced the Internet Explorer Web Technology Infrastructure 1 of 7 browser, which is currently the most popular browser in the world (pp. 58-59). Most people date the birth of the World Wide Web to 1993 and the creation of the Web browser. Note the World Wide Web and the Internet are not the same thing. The Internet is the large computer network and the underlying technologies. The World Wide Web is the graphical Internet as it is viewed through a Web browser. A Little More About HTML: o Here is a brief analogy explaining the basic fundamentals of HTML. Let’s say you write a resume and give it a friend and ask them to be proofread it. They take out their red pen and make suggestions by writing on it. In other words, they “marked up” your page. Remember that HTML stands for Hyper Text MARKUP Language. Instead of using a red pen, HTML uses “tags” to markup a Web page. o An HTML document is broken into two elements: document content and tags. Document content is those parts of the document that the user actually sees. The tags are used to format the document content, such as making the document content bold. o Below is a brief example of HTML code as well as how a Web browser will render it to the screen. <B> is an example of an opening tag and </B> is an example of a closing tag. Everything between the tags will be bolded when displayed on the screen. <B>Scott Tollison</B> Technology Infrastructure 2 of 7 o Below is another brief example of HTML code as well as how a Web browser will render it to the screen. <FONT> is an example of an opening tag and </FONT> is an example of a closing tag. Everything between the tags will be displayed in blue and made three sizes bigger than normal when displayed on the screen. <FONT COLOR=BLUE SIZE=+3>Scott Tollison</FONT> o If you would like to view the HTML of any Web page, simply right-click anywhere in the page (so long as it is not on top of a picture) and select View Source from the menu that appears. Technology of the Internet: o Circuit Switching vs. Packet Switching: Our telephone system works by establishing a dedicated connection from caller to receiver known as a circuit. The circuit is maintained for the entire length of the call. This method is known as circuit switching (p. 60). Circuit switching would not work well for the Internet. If someone was sending a data file to someone else and the circuit was interrupted, the entire file would be lost. With millions and millions of pieces of data sent everyday, this would quickly turn into a disaster. This is not a big deal with telephone traffic because if the circuit was disconnected, the sender would probably call the receiver back and they would continue the call from where they left off. The Internet, instead uses packet-switching technology. In packet switching, data files are broken down into smaller chunks known as Technology Infrastructure 3 of 7 packets. Each packet is labeled and numbered. Packets are sent over the Internet separately and are free to take whatever route is quickest and easiest to reach their destination. Because packets take different routes to the same destination, packets may arrive at the destination out of order. This is no problem, however, because they are numbered, they may quickly be reassembled (p. 60). o LINK FOR PS HERE Routers: As packets move from one network to another, computers known as routers determine the best path for getting the packet from one network to the next. Routers do through small software programs and the maintenance of tables of information (p. 60). These routing tables often include information such as the location of the nearest routers and how long it will take a data packet to reach each one. o Protocols: A protocol is a collection of rules for formatting, ordering, and errorchecking data sent across a network. These rules also dictate what is allowed in a transmission and how it is formatted. Before two computers exchange data, they must use the same protocol so they can understand one another (p. 62). The primary protocol used on the Internet today is TCP/IP (p. 62). The TCP portion controls the breaking down of data into packets from the sender and their reassembly at the receiver. The IP portion controls the routing and addressing functions. In other words, IP is responsible for finding the right computer. All computers using the TCP/IP protocol are assigned an IP address. The number will look something like 216.115.108.245. Technology Infrastructure 4 of 7 o Each number is known as an octet and each octet can be any number between 0 and 255. These octets can form over 4 billion separate addresses. o If you would like to view the IP address of the computer you are working at, click Start, then Run, then either command or cmd (depending on what operating system you are using), and then either ipconfig or winipcfg (depending on what operating system you are using. Another necessary protocol is HTTP. HTTP are the rules responsible for delivering Web pages for the recipients in a format understood by his of her Web browser. Notice that the first word of any Web address (a.k.a. URL) is http://. o Domain Names: It would be somewhat difficult to remember the IP addresses of all the Web sites you like. Therefore, an alternative addressing scheme was created. Domain names are sets of words that are assigned to specific IP addresses (p. 64). Without domain names, you would have to remember the IP address of every Web site you wished to visit. Would you prefer to remember the IP address of your favorite Web site (such as 129.33.95.163) or the domain name of your favorite Web site (such as www.coke.com)? If you would like a demonstration of how domain names work, try the following: Technology Infrastructure Open Internet Explorer, and type http://129.33.95.163 Open Internet Explorer, and type http://www.coke.com Notice they do the same thing. Most domain names consist three parts (p. 65): www – which indicates it is part of the world wide web name of the organization – such as Harvard, coke, pespi, muw 5 of 7 and a top-level domain which identifies the type of Web site (.edu for colleges, .com for commercial, .org for non-profit organizations, etc.) o Since 1998, an organization known as the Internet Corporation for Assigned Names and Numbers (ICANN) has been responsible for managing domain names (p. 65). Intranets vs. Extranets: o An intranet does not extend beyond the organization itself. An intranet may use the same technologies such as a Web browser, e-mail, etc., but it can only be seen by people working for the company (p. 82). o An extranet is similar to an intranet except that an extranet grants access to a limited portion of the organization’s data to business partners (p. 83). Internet Connectivity: o Connectivity to the Internet is generally through an Internet Service Provider (ISP). These companies sell Internet access directly to individuals (p. 56). o The quality of the connection is generally measured through bandwidth or the amount of data that can travel through a communication line. The better the bandwidth, the faster the download files or view Web pages (p. 85). o A fundamental unit of computer storage space is the bit. 8 bits equal one byte which is capable of storing one character. Bandwidth is measured in either Kbps (kilobits of bits transmitted per second, or thousands of bits per second) or Mbps (megabits per second, or millions of bits per second). o Bandwidth Comparisons (pp. 86-88): Dial-up (plain-old telephone system, POTS) – 28-56 Kbps of bandwidth DSL (digital subscriber line) – the textbook reports from 1.5 – 9 Mbps, but more realistically it is between 1.5-3 Mbps T1 – 1.544 Mbps (not generally available to individual consumers, but instead to organizations such as large businesses or colleges) Technology Infrastructure 6 of 7 T3 – 44.736 Mbps (not generally available to individual consumers, but instead to organizations such as large businesses or colleges) Fiber-optic – up to 10 Gbps (Gbps=gigabits, or billions of bits per second; not generally used by individual consumers or organizations, but instead used by telecommunications companies to connect cities over great distances (p. 88). If you are interested in testing your own bandwidth, you can do so at http://reviews.cnet.com/7004-7254_7-0.html. Technology Infrastructure 7 of 7