How the Internet works On the Internet, when you want to retrieve a document from another computer, you request a service from this computer. Your computer is the client, the computer on which the information you want to access is stored, is called the server. Therefore the Internet's architecture is called client-server architecture. A common set of standards allows the exchange of data and commands independent from locations, time, and operating systems through the Internet. These standards are called communication protocols, or the Internet Protocol Suite, and are implemented in Internet software. Sometimes the Internet Protocol Suite is erroneously identified with TCP/IP (Transmission Control Protocol / Internet Protocol). Any information to be transferred is broken down into pieces, so-called packets, and the Internet Protocol figures out how the data is supposed to get from A to B by passing through routers. Each packet is "pushed" from router to router via gateways and might take a different route. It is not possible to determine in advance which ways these packets will take. At the receiving end the packets are checked and reassembled. The technique of breaking down all messages and requests into packets has the advantage that a large data bundle (e.g. videos) sent by a single user cannot block a whole network, because the bandwidth needed is deployed on several packets sent on different routes. Detailed information about routing in the Internet can be obtained at http://www.scit.wlv.ac.uk/~jphb/comms/iproute.html. One of the Internet's (and of the Matrix's) beginnings was the ARPANet, whose design was intended to withstand any disruption, as for example in military attacks. The ARPANet was able to route data around damaged areas, so that the disruption would not impede communication. This design, whith its origin in strategic and military considerations, remained unchanged for the Internet. Yet the design of the ARPANet's design cannot be completely applied to the Internet. Routing around depends on the location of the interruption and on the availability of intersecting points between networks. If, for example, an E-mail message is sent from Brussels to Athens and in Germany a channel is down, it will not affect access very much, the message will be routed around this damage, as long as a major Internet exchange is not affected. However, if access depends on a single backbone connection to the Internet and this connection is cut off, there is no way to route around. In most parts of the world the Internet is therefore vulnerable to disruption. "The idea of the Internet as a highly distributed, redundant global communications system is a myth. Virtually all communications between countries take place through a very small number of bottlenecks, and the available bandwidth isn't that great," says Douglas Barnes. These bottlenecks are the network connections to neighboring countries. Many countries rely on a one single connection to the Net, and in some places, such as the Suez Canal, there is a concentration of fiber-optic cables of critical importance.

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In Search of Reliable Internet Measurement Data Newspapers and magazines frequently report growth rates of Internet usage, number of users, hosts, and domains that seem to be beyond all expectations. Growth rates are expected to accelerate exponentially. However, Internet measurement data are anything thant reliable and often quite fantastic constructs, that are nevertheless jumped upon by many media and decision makers because the technical difficulties in measuring Internet growth or usage are make reliable measurement techniques impossible. Equally, predictions that the Internet is about to collapse lack any foundation whatsoever. The researchers at the Internet Performance Measurement and Analysis Project (IPMA) compiled a list of news items about Internet performance and statistics and a few responses to them by engineers. Size and Growth In fact, "today's Internet industry lacks any ability to evaluate trends, identity performance problems beyond the boundary of a single ISP (Internet service provider, M. S.), or prepare systematically for the growing expectations of its users. Historic or current data about traffic on the Internet infrastructure, maps depicting ... there is plenty of measurement occurring, albeit of questionable quality", says K. C. Claffy in his paper Internet measurement and data analysis: topology, workload, performance and routing statistics (http://www.caida.org/Papers/Nae/, Dec 6, 1999). Claffy is not an average researcher; he founded the well-known Cooperative Association for Internet Data Analysis (CAIDA). So his statement is a slap in the face of all market researchers stating otherwise. In a certain sense this is ridiculous, because since the inception of the ARPANet, the offspring of the Internet, network measurement was an important task. The very first ARPANet site was established at the University of California, Los Angeles, and intended to be the measurement site. There, Leonard Kleinrock further on worked on the development of measurement techniques used to monitor the performance of the ARPANet (cf. Michael and Ronda Hauben, Netizens: On the History and Impact of the Net). And in October 1991, in the name of the Internet Activities Board Vinton Cerf proposed guidelines for researchers considering measurement experiments on the Internet stated that the measurement of the Internet. This was due to two reasons. First, measurement would be critical for future development, evolution and deployment planning. Second, Internet-wide activities have the potential to interfere with normal operation and must be planned with care and made widely known beforehand. So what are the reasons for this inability to evaluate trends, identity performance problems beyond the boundary of a single ISP? First, in early 1995, almost simultaneously with the worldwide introduction of the World Wide Web, the transition of the stewardship role of the National Science Foundation over the Internet into a competitive industry (bluntly spoken: its privatization) left no framework for adequate tracking and monitoring of the Internet. The early ISPs were not very interested in gathering and analyzing network performance data, they were struggling to meet demands of their rapidly increasing customers. Secondly, we are just beginning to develop reliable tools for quality measurement and analysis of bandwidth or performance. CAIDA aims at developing such tools. "There are many estimates of the size and growth rate of the Internet that are either implausible, or inconsistent, or even clearly wrong", K. G. Coffman and Andrew, both members of different departments of AT & T Labs-Research, state something similar in their paper The Size and Growth Rate of the Internet, published in First Monday. There are some sources containing seemingly contradictory information on the size and growth rate of the Internet, but "there is no comprehensive source for information". They take a well-informed and refreshing look at efforts undertaken for measuring the Internet and dismantle several misunderstandings leading to incorrect measurements and estimations. Some measurements have such large error margins that you might better call them estimations, to say the least. This is partly due to the fact that data are not disclosed by every carrier and only fragmentarily available. What is measured and what methods are used? Many studies are devoted to the number of users; others look at the number of computers connected to the Internet or count IP addresses. Coffman and Odlyzko focus on the sizes of networks and the traffic they carry to answer questions about the size and the growth of the Internet. You get the clue of their focus when you bear in mind that the Internet is just one of many networks of networks; it is only a part of the universe of computer networks. Additionally, the Internet has public (unrestricted) and private (restricted) areas. Most studies consider only the public Internet, Coffman and Odlyzko consider the long-distance private line networks too: the corporate networks, the Intranets, because they are convinced (that means their assertion is put forward, but not accompanied by empirical data) that "the evolution of the Internet in the next few years is likely to be determined by those private networks, especially by the rate at which they are replaced by VPNs (Virtual Private Networks) running over the public Internet. Thus it is important to understand how large they are and how they behave." Coffman and Odlyzko check other estimates by considering the traffic generated by residential users accessing the Internet with a modem, traffic through public peering points (statistics for them are available through CAIDA and the National Laboratory for Applied Network Research), and calculating the bandwidth capacity for each of the major US providers of backbone services. They compare the public Internet to private line networks and offer interesting findings. The public Internet is currently far smaller, in both capacity and traffic, than the switched voice network (with an effective bandwidth of 75 Gbps at December 1997), but the private line networks are considerably larger in aggregate capacity than the Internet: about as large as the voice network in the U. S. (with an effective bandwidth of about 330 Gbps at December 1997), they carry less traffic. On the other hand, the growth rate of traffic on the public Internet, while lower than is often cited, is still about 100% per year, much higher than for traffic on other networks. Hence, if present growth trends continue, data traffic in the U. S. will overtake voice traffic around the year 2002 and will be dominated by the Internet. In the future, growth in Internet traffic will predominantly derive from people staying longer and from multimedia applications, because they consume more bandwidth, both are the reason for unanticipated amounts of data traffic. Hosts The Internet Software Consortium's Internet Domain Survey is one of the most known efforts to count the number of hosts on the Internet. Happily the ISC informs us extensively about the methods used for measurements, a policy quite rare on the Web. For the most recent survey the number of IP addresses that have been assigned a name were counted. At first sight it looks simple to get the accurate number of hosts, but practically an assigned IP address does not automatically correspond an existing host. In order to find out, you have to send a kind of message to the host in question and wait for a reply. You do this with the PING utility. (For further explanations look here: Art. PING, in: Connected: An Internet Encyclopaedia) But to do this for every registered IP address is an arduous task, so ISC just pings a 1% sample of all hosts found and make a projection to all pingable hosts. That is ISC's new method; its old method, still used by RIPE, has been to count the number of domain names that had IP addresses assigned to them, a method that proved to be not very useful because a significant number of hosts restricts download access to their domain data. Despite the small sample, this method has at least one flaw: ISC's researchers just take network numbers into account that have been entered into the tables of the IN-ADDR.ARPA domain, and it is possible that not all providers know of these tables. A similar method is used for Telcordia's Netsizer. Internet Weather Like daily weather, traffic on the Internet, the conditions for data flows, are monitored too, hence called Internet weather. One of the most famous Internet weather report is from The Matrix, Inc. Another one is the Internet Traffic Report displaying traffic in values between 0 and 100 (high values indicate fast and reliable connections). For weather monitoring response ratings from servers all over the world are used. The method used is to "ping" servers (as for host counts, e. g.) and to compare response times to past ones and to response times of servers in the same reach. Hits, Page Views, Visits, and Users Let us take a look at how these hot lists of most visited Web sites may be compiled. I say, may be, because the methods used for data retrieval are mostly not fully disclosed. For some years it was seemingly common sense to report requested files from a Web site, so called "hits". A method not very useful, because a document can consist of several files: graphics, text, etc. Just compile a document from some text and some twenty flashy graphical files, put it on the Web and you get twenty-one hits per visit; the more graphics you add, the more hits and traffic (not automatically to your Web site) you generate. In the meantime page views, also called page impressions are preferred, which are said to avoid these flaws. But even page views are not reliable. Users might share computers and corresponding IP addresses and host names with others, she/he might access not the site, but a cached copy from the Web browser or from the ISP's proxy server. So the server might receive just one page request although several users viewed a document. Especially the editors of some electronic journals (e-journals) rely on page views as a kind of ratings or circulation measure, Rick Marin reports in the New York Times. Click-through rates - a quantitative measure - are used as a substitute for something of intrinsically qualitative nature: the importance of a column to its readers, e. g. They may read a journal just for a special column and not mind about the journal's other contents. Deleting this column because of not receiving enough visits may cause these readers to turn their backs on their journal. More advanced, but just slightly better at best, is counting visits, the access of several pages of a Web site during one session. The problems already mentioned apply here too. To avoid them, newspapers, e.g., establish registration services, which require password authentication and therefore prove to be a kind of access obstacle. But there is a different reason for these services. For content providers users are virtual users, not unique persons, because, as already mentioned, computers and IP addresses can be shared and the Internet is a client-server system; in a certain sense, in fact computers communicate with each other. Therefore many content providers are eager to get to know more about users accessing their sites. On-line registration forms or WWW user surveys are obvious methods of collecting additional data, sure. But you cannot be sure that information given by users is reliable, you can just rely on the fact that somebody visited your Web site. Despite these obstacles, companies increasingly use data capturing. As with registration services cookies come here into play. For If you like to play around with Internet statistics instead, you can use Robert Orenstein's Web Statistics Generator to make irresponsible predictions or visit the Internet Index, an occasional collection of seemingly statistical facts about the Internet. Measuring the Density of IP Addresses Measuring the Density of IP Addresses or domain names makes the geography of the Internet visible. So where on earth is the most density of IP addresses or domain names? There is no global study about the Internet's geographical patterns available yet, but some regional studies can be found. The Urban Research Initiative and Martin Dodge and Narushige Shiode from the Centre for Advanced Spatial Analysis at the University College London have mapped the Internet address space of New York, Los Angeles and the United Kingdom (http://www.geog.ucl.ac.uk/casa/martin/internetspace/paper/telecom.html and http://www.geog.ucl.ac.uk/casa/martin/internetspace/paper/gisruk98.html). Dodge and Shiode used data on the ownership of IP addresses from RIPE, Europe's most important registry for Internet numbers.

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1970s: Computer-Integrated Manufacturing (CIM) Since the 1970s there had been a growing trend towards the use of computer programs in manufacturing companies. Especially functions related to design and production, but also business functions should be facilitated through the use of computers. Accordingly the CAD/CAM technology, related to the use of computer systems for design and production, was developed. CAD (computer-aided design) was created to assist in the creation, modification, analysis, and optimization of design. CAM (computer-aided manufacturing) was designed to help with the planning, control, and management of production operations. CAD/CAM technology, since the 1970s, has been applied in many industries, including machined components, electronics products, equipment design and fabrication for chemical processing. To enable a more comprehensive use of computers in firms the CIM (computer-integrated manufacturing) technology, which also includes applications concerning the business functions of companies, was created. CIM systems can handle order entry, cost accounting, customer billing and employee time records and payroll. The scope of CIM technology includes all activities that are concerned with production. Therefore in many ways CIM represents the highest level of automation in manufacturing.

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Backbone Networks Backbone networks are central networks usually of very high bandwidth, that is, of very high transmitting capacity, connecting regional networks. The first backbone network was the NSFNet run by the National Science Federation of the United States.

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Electronic Messaging (E-Mail) Electronic messages are transmitted and received by computers through a network. By E-Mail texts, images, sounds and videos can be sent to single users or simultaneously to a group of users. Now texts can be sent and read without having them printed. E-Mail is one of the most popular and important services on the Internet.

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Automation Automation is concerned with the application of machines to tasks once performed by humans or, increasingly, to tasks that would otherwise be impossible. Although the term mechanization is often used to refer to the simple replacement of human labor by machines, automation generally implies the integration of machines into a self-governing system. Automation has revolutionized those areas in which it has been introduced, and there is scarcely an aspect of modern life that has been unaffected by it. Nearly all industrial installations of automation, and in particular robotics, involve a replacement of human labor by an automated system. Therefore, one of the direct effects of automation in factory operations is the dislocation of human labor from the workplace. The long-term effects of automation on employment and unemployment rates are debatable. Most studies in this area have been controversial and inconclusive. As of the early 1990s, there were fewer than 100,000 robots installed in American factories, compared with a total work force of more than 100 million persons, about 20 million of whom work in factories.

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