Q. What is Computer communications networks?

Computer communications networks are the outcome of a combination of computers and telecommunication products. An interconnected group of independent computers and peripheral devices that communicate with each other for the purpose of sharing software and hardware resources is known as a computer communications network. A local-area network (LAN) is any physical network technology that operates at high speed (usually tens ofMbits per second through several Gbits per second) over short distances (up to a few thousand meters). Examples include Ethernet and proNET-10. The stations, also known as nodes, within a LAN are physically linked with each other through twisted pairs of copper wires, coaxial cables, or fiber-optic cables. A wide- area network (WAN, also known as long-haul network) is any physical network that spans large geographic distances, usually operates at slower speeds, and has significantly higher delays than a LAN. Stations within a WAN communicate with each other through standard telephone lines, dedicated telephone lines, line-of-sight microwave systems, or fiber-optic links. Public-data network (PDN) is network service offered by a common carrier, such as Telnet, Tymnet, and Dataphone Digital Services of AT&T. ARPANET (Advanced Research Projects Agency of the U.S. Department of Defense) is an example of a private communications network. CYBERNET is an example of a remote-access communications network that provides access to huge databases for their users in different countries. The Internet is a collection of networks and gateways (special- purpose dedicated computers attached to various networks routing packets of information fromone to the other), including theMilnet (military network) and NSFNET (National Science Foundation network), that function as a single, cooperative virtual network providing universal connectivity and application-level services such as the electronic mail. The Internet reaches many universities, government research labs, and military installations in several countries.