Computer Networks

Computer Networks:-

During the period 1943 to 1946, the first electronic digital computer, called the ENIAC, was built at the Moore School of Electrical Engineering of the University of Pennsylvania under the technical direction of J. Presper Eckert, Jr., and John W. Mauchly. However, John von Neumann’s contributions were among the earliest and most fundamental to the theory, design, and application of digital computers, which go back to the first draft of a report written in 1945. Computers and terminals started communicating with each other over long distances in the early 1950s. The links used were initially voice-grade telephone channels operating at low speeds (300 to 1200 b/s). Various factors have contributed to a dramatic increase in data transmission rates; notable among them are the idea of adaptive equalization, pioneered by Robert Lucky in 1965, and efficient modulation techniques, pioneered by G. Ungerboeck in 1982. Another idea widely employed in computer communications is that of automatic repeat-request (ARQ). The ARQ method was originally devised by H. C. A. van Duuren during World War II and published in 1946. It was used to improve radio-telephony for telex transmission over long distances. From 1950 to 1970, various studies were made on computer networks. However, the most significant of them in terms of impact on computer communications was the Advanced Research Projects Agency Network (ARPANET), first put into service in 1971. The development of ARPANET was sponsored by the Advanced Research Projects Agency of the U. S. Department of Defense. The pioneering work in packet switching was done on ARPANET. In 1985, ARPANET was renamed the Internet. The turning point in the evolution of the Internet occurred in 1990 when Tim Berners-Lee proposed a hypermedia software interface to the Internet, which he named the World Wide Web. In the space of only about two years, the Web went from nonexistence to worldwide popularity, culminating in its commercialization in 1994. We may explain the explosive growth of the Internet by offering these reasons:

•   Before the Web exploded into existence, the ingredients for its creation were already in place. In particular, thanks to VLSI, personal computers (PCs) had already become ubiquitous in homes throughout the world, and they were increasingly equipped with modems for interconnectivity to the outside world. 
•  For about two decades, the Internet had grown steadily (albeit within a confined community of users), reaching a critical threshold of electronic mail and file transfer.
•  Standards for document description and transfer, hypertext markup language (HTML), and hypertext transfer protocol (HTTP) had been adopted.