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Computers Are Networked Chapter 11 Computers are networked In the very early days, according to a remark often attributed to Howard Aiken, some of the people in business believed that “only a very small number of computers would be needed to serve the needs of the whole world, per- haps a dozen, with eight or ten for the United States.”. Although it is somewhat misquoted, the fact is that there used to be very few computers, and they were quite expensive. As a result, it was not very accessible to the general public. 1 It certainly has changed.... This situation started to change in the early 1980’s, when IBM introduced its personal com- puter (IBM PC) for use in the home, office and schools. With an introduction of $1,995, followed by many clones, computers suddenly became af- fordable. The number of personal computers in use was more than doubled from 2 million in 1981 to 5.5 million in 1982. Ten years later, 65 million PCs were being used. The computers were getting smaller: from desk- top to laptop, notebook, to tablets today, while retaining its processing power, and the price keeps on dropping. We are even talking about $100 notebook for the kids. Thus, many of us can now afford to have a computer. 2 A big thing All such computers, big or small, were con- nected together into networks to share hard- ware such as a printer, software such as Alice, and, more importantly, information. Just look at any cluster on campus: twenty plus computers share one or two printers, they share some of the applications, such as the Microsoft Office suite, as well as the data: In- deed, when any one tries to look at your grade, they are looking at the same document. Eventually, a global web of computer, the In- ternet, links computers worldwide into a single network of information. 3 How did we get Internet? In October 1962, Joseph Licklider was appointed head of the United States Department of De- fense’s Advanced Research Projects Agency (DARPA), within the Information Processing Office. Joseph formed an informal group within DARPA to further computer research, including installing three network terminals: one for System De- velopment Corporation in Santa Monica, one for Project Genie at the UC Berkeley and one for the Compatible Time-Sharing System project at the MIT. Question: What is Timing sharing? Answers: When you have to do multiple things, they take turns. 4 Then what? Several research programs began to explore and articulate principles of networking between physically separate networks, leading to the de- velopment of the packet switching model of digital networking. The basic idea of packet switching is this: When sending data between two computers connected to a network, we will cut the data into la- beled packets, select paths in between, often the shortest ones, send the packets over to the destination, possibly along different paths, then reassemble them back to the original doc- ument. 5 Finally,... Such research led to the development of sev- eral packet-switching networks in the late 1960s and 1970s, including the ARPANET. But, these networks were still disjointed sepa- rate networks, served only by limited connec- tion (gateways) between networks. Further efforts were then made to develop a protocol(a set of rules) for internetworking, where multiple different networks could be joined together into a bigger network. This spread of internetworking began to form a global network, i.e., Internet, based on stan- dardized protocols officially implemented in 1982. 6 Local area network At the same time, the technology of inter- connecting many networks of a much smaller scale(local area network) enabled the sharing of software, hardware and information in a lo- cal area such as Memorial 213. Thus, as we discussed in the Data structure module, Internet is really a complicated graph structure that interconnect computers, many form their own local area networks. 7 Here comes the Web... As the Internet grew through the 1980s and early 1990s, people felt the need to organize files and information spread in such a incre- mentally complicated structure so that they can be easily found. Projects such as Gopher, WAIS, and the FTP Archive list made early attempts to create ways to organize distributed data, but, unfortunately, they all failed to accommodate all the existing data types. Furthermore, none was user friendly, i.e., they were pretty difficult to use. 8 A better interface One of the most promising user interface paradigms during this period was hypertext, which we use today in web pages, i.e., when you click a link, it goes to somewhere in the Net. It consists of two pieces, one is the name of this link, which the user knows; and the other is the where- abouts of this link, which is technical and the user does not need to know. This technology actually occurred earlier, Go- pher implemented the first commonly-used hy- pertext interface to the Internet. 9 Just a bit technical When you launch such a browser, you are con- nected to its Home page, the start point of your navigation. When you click at any of its hypertext links, with its hidden address in the form of a URL, the browser will display that web page, which again contains many links, and the navigation continues. A typical URL is the following: http://www.nps.gov/yose/planyourvisit/rvcamping.htm Here, the http stands for hypertext transfer protocol, which tells the browser how to talk to that particular machine. The site www.nps.gov tells who owns this web site, and implicitly where the machine is, via an address book. The rest of the address yose/planyourvisit/rvcamping.htm provides the name of the web page. 10 ... and the other stuff In 1989, while working at CERN, Tim Berners- Lee invented a network-based implementation of the hypertext concept, which led to the eventual development of the World Wide Web. A turning point is the Mosaic graphic web browser that a team based in University of Illinois at Urbana-Champaign, developed in 1993, led by Marc Andreessen, and completed by the Netscape company. Yahoo was founded in 1995, Google started in 1996, all doing business to help us to find what we want in the Web. Then, the software giant Microsoft introduced IE in August 2005. The rest is history. 11 Other Internet service 1. FTP(File Transfer Protocol): This is for you to connect to a remote computer, an FTP site, to transfer files to your own computers. 2. Telnet: This is for you to connect to a remote computer. For example, when you are home, but want to log on to a mainframe com- puter such as oz or turing. It is especially useful if you keep your files there, or to get informa- tion from a large data depository, such as a library. If you want to log on to your M: drive from a remote site, and transfer files in between, you need to download a piece of software, e.g., PuTTY. 3. Newsgroups: This is for you to join or just read electronic news bulletins. 4. Chat rooms: This is for you to join a live discussion about anything. 12 Internet Service Provider (ISP) An ISP is a company that provides the ser- vice so that you can connect to the Internet, just like what a phone company does when you want to talk to other people. Examples include AOL, AT&T, MSN, and many of your local providers, such as Metrocast. The process is very similar to order other com- munication service. Once they come to install the equipment, and hook you up, you log on and in. 13 Spam: unwanted email These days, we often have to spend lots of time in discovering, and deleting email, that we don’t want. It is estimated that over 60 % of the emails are spam mails. In fact, for the California-based Postini Inc., about 85% percent of the roughly 1 billion pieces of e-mail the company handles each week are spams. AOL blocks about 2.4 billion pieces of spam mail every day. It costs about 10 billion dollars to fight spam mails. 14 Fight Spam Besides the measures as suggested in pp. 53, such as deletion w/o opening, never reply to such a message, and add on a filter, etc., Some legal actions have also been taken. President Bush signed into law which makes span illegal. Some states, such as California, already has strict anti-spam laws. But, as we saw, the hard-core spammers have yet to show any sign to clean their act, which now pays about $200 to $500 for sending out a million spam messages. 15 Black Penny project Some serious efforts, e.g., the Penny Black Project, have been made to destroy the busi- ness model of email spam. The essential idea is to let the sender spend more time, but not the receiver. “If I don’t know you, you have to prove to me that you spent ten seconds of your CPU time just for me, and just for this message.” In practice, an algorithm is put in every email system so that it takes several seconds to send it out to any receiver, which will make the practice of spamming essentially infeasible. Microsoft, among others, has been working on such a project. 16 Activities Activities Write a one-page single-space es- say either for, or against, one of the following statements: 1. In this information age, English will become a universal language.
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