20-09-2012, 12:00 PM
Internet
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The Internet is a global system of interconnected computer networks that use the standardInternet protocol suite (often called TCP/IP, although not all applications use TCP) to serve billions of users worldwide. It is a network of networks that consists of millions of private, public, academic, business, and government networks, of local to global scope, that are linked by a broad array of electronic, wireless and optical networking technologies. The Internet carries an extensive range of information resources and services, such as the inter-linked hypertext documents of theWorld Wide Web (WWW) and the infrastructure to support email.
Most traditional communications media including telephone, music, film, and television are reshaped or redefined by the Internet, giving birth to new services such as Voice over Internet Protocol (VoIP) and Internet Protocol Television (IPTV). Newspaper, book and other print publishing are adapting to Web site technology, or are reshaped into blogging and web feeds. The Internet has enabled and accelerated new forms of human interactions through instant messaging, Internet forums, and social networking. Online shopping has boomed both for major retail outlets and smallartisans and traders. Business-to-business and financial services on the Internet affect supply chains across entire industries.
The origins of the Internet reach back to research of the 1960s, commissioned by the United States government in collaboration with private commercial interests to build robust, fault-tolerant, and distributed computer networks. The funding of a new U.S. backbone by the National Science Foundation in the 1980s, as well as private funding for other commercial backbones, led to worldwide participation in the development of new networking technologies, and the merger of many networks. The commercialization of what was by the 1990s an international network resulted in its popularization and incorporation into virtually every aspect of modern human life. As of 2011, more than 2.2 billion people – nearly a third of Earth's population — use the services of the Internet
History
The first two nodes of what would become the ARPANET were interconnected between Leonard Kleinrock's Network Measurement Center at the UCLA's School of Engineering and Applied Scienceand Douglas Engelbart's NLS system at SRI International (SRI) in Menlo Park, California, on 29 October 1969.[10] The third site on the ARPANET was the Culler-Fried Interactive Mathematics center at the University of California at Santa Barbara, and the fourth was the University of Utah Graphics Department. In an early sign of future growth, there were already fifteen sites connected to the young ARPANET by the end of 1971.[11][12] These early years were documented in the 1972 film Computer Networks: The Heralds of Resource Sharing.
Early international collaborations on ARPANET were sparse. For various political reasons, European developers were concerned with developing the X.25 networks.[13] Notable exceptions were the Norwegian Seismic Array (NORSAR) in 1972, followed in 1973 by Sweden with satellite links to the Tanum Earth Station and Peter T. Kirstein's research group in the UK, initially at the Institute of Computer Science, London University and later at University College London
General structure
The Internet structure and its usage characteristics have been studied extensively. It has been determined that both the Internet IP routing structure and hypertext links of the World Wide Web are examples of scale-free networks.[30]
Many computer scientists describe the Internet as a "prime example of a large-scale, highly engineered, yet highly complex system".[31] The Internet is heterogeneous; for instance, data transfer rates and physical characteristics of connections vary widely. The Internet exhibits "emergent phenomena" that depend on its large-scale organization. For example, data transfer rates exhibit temporalself-similarity. The principles of the routing and addressing methods for traffic in the Internet reach back to their origins in the 1960s when the eventual scale and popularity of the network could not be anticipated. Thus, the possibility of developing alternative structures is investigated.[32] The Internet structure was found to be highly robust[33] to random failures and very vulnerable to high degree attacks