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How the Internet works |
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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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ARPAnet
ARPAnet was the small network of individual computers connected by leased lines that marked the beginning of today's global data networks. Being an experimental network mainly serving the purpose to test the feasibility of wide area networks, the possibility of remote computing, it was created for resource sharing between research institutions, not for messaging services like E-mail. Although research was sponsored by US military, ARPAnet was not designed for directly martial use but to support military-related research.
In 1969 ARPANET went online and links the first two computers, one of them located at the University of California, Los Angeles, the other at the Stanford Research Institute.
But ARPAnet has not become widely accepted before it was demonstrated in action to a public of computer experts at the First International Conference on Computers and Communication in Washington, D. C. in 1972.
Before it was decommissioned in 1990, NSFnet, a network of scientific and academic computers funded by the National Science Foundation, and a separate new military network went online in 1986. In 1988 the first private Internet service providers offered a general public access to NSFnet. Beginning in 1995, after having become the backbone of the Internet in the USA, NSFnet was turned over to a consortium of commercial backbone providers. This and the launch of the World Wide Web added to the success of the global data network we call the Net.
In the USA commercial users already outnumbered military and academic users in 1994.
Despite the rapid growth of the Net, most computers linked to it are still located in the United States.
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