History

Early networks of communicating computers included the military radar system Semi-Automatic Ground Environment (SAGE) and its relative the commercial airline reservation system Semi-Automatic Business Research Environment (SABRE), starting in the late 1950s.

In the 1960s, the Advanced Research Projects Agency (ARPA) started funding the design of the Advanced Research Projects Agency Network (ARPANET) for the United States Department of Defense. Development of the network began in 1969, based on designs developed during the 1960s.The ARPANET evolved into the modern Internet.

Purpose

§  Facilitating communications. Using a network, people can communicate efficiently and easily via email, instant messaging, chat rooms, telephone, video telephone calls, and video conferencing.

§  Sharing hardware. In a networked environment, each computer on a network may access and use hardware resources on the network, such as printing a document on a shared network printer.

§  Sharing files, data, and information. In a network environment, authorized user may access data and information stored on other computers on the network. The capability of providing access to data and information on shared storage devices is an important feature of many networks.

§  Sharing software. Users connected to a network may run application programs on remote computers.

§  Information preservation.

§  Security.

 

Network Classification.

Connection method

Computer networks can be classified according to the hardware and software technology that is used to interconnect the individual devices in the network, such as optical fiber, Ethernet, wireless LAN, HomePNA, power line communication or G.hn.

Ethernet as it is defined by IEEE 802 utilizes various standards and mediums that enable communication between devices. Frequently deployed devices include hubs, switches, bridges, or routers. Wireless LAN technology is designed to connect devices without wiring. These devices use radio waves or infrared signals as a transmission medium. ITU-T G.hn technology uses existing home wiring (coaxial cable, phone lines and power lines) to create a high-speed (up to 1 Gigabit/s) local area