COMPUTER NETWORKING

Computer networking is the scientific and engineering discipline concerned with communication between computer systems. Such networks involve at least two computers seperated by a few inches (e.g. via Bluetooth) or thousands of miles (e.g. via the Internet). Computer networking is sometimes considered a sub-discipline of telecommunications.

History
Carrying instructions between calculation machines and early computers was done by human users. In September, 1940 George Stibitz used a teletype machine to send instructions for a problem set from his Model K at Dartmouth College in New Hampshire to his Complex Number Calculator in New York and received results back by the same means. Linking output systems like teletypes to computers was an interest at the Advanced Research Projects Agency ARPA when, in 1962, J.C.R. Licklider was hired and developed a working group he called the “Intergalactic Network”, a precursor to the ARPANet. In 1964, researchers at Dartmouth developed a time sharing system for distributed users of large computer systems. The same year, at MIT, a research group supported by General Electric and Bell Labs used a computer (DEC’s PDP-8) to route and manage telephone connections. In 1968 Paul Baran proposed a network system consisting of datagrams or packets that could be used in a packet switching network between computer systems. In 1969 the University of California at Los Angeles, SRI (in Stanford), University of California at Santa Barbara, and the University of Utah were connected as the beginning of the ARPANet network using 50 kbit/s circuits.

Categorizing

Local area network
A local area network (LAN) is a computer network covering a small local area, like a home, office, or small group of buildings such as a home, office, or college. Current LANs are most likely to be based on switched Ethernet or Wi-Fi technology running at from 10 to 10000 Mbit/s. The defining characteristics of LANs in contrast to WANs are: a) much higher data rates, b) smaller geographic range - at most a few kilometers, and c) they do not involve leased telecommunication lines. “LAN” usually does not refer to data running over local analog telephone lines, as on a private branch exchange (PBX).

Wide area network
A wide area network or WAN is a computer network covering a wide geographical area, involving a vast array of computers. This is different from personal area networks (PANs), metropolitan area networks (MANs) or local area networks (LANs) that are usually limited to a room, building or campus. The most well-known example of a WAN is the Internet.

WANs are used to connect local area networks (LANs) together, so that users and computers in one location can communicate with users and computers in other locations. Many WANs are built for one particular organization and are private. Others, built by Internet Service Providers, provide connections from an organization’s LAN to the Internet. WANs are most often built using leased lines. At each end of the leased line, a router connects to the LAN on one side and a hub within the WAN on the other.

Network protocols including TCP/IP deliver transport and addressing functions. Protocols including Packet over SONET/SDH, MPLS, ATM and Frame relay are often used by service providers to deliver the links that are used in WANs. X.25 was an important early WAN protocol, and is often considered to be the “grandfather” of Frame Relay as many of the underlying protocols and functions of X.25 are still in use today (with upgrades) by Frame Relay.

Benefits of Networks

•	Exchanging Data
•	Sharing system resources
•	Creation of workgroups
•	Centralized Management
•	Security
•	Access to more than one operating system
•	Enhancement of the corporate structure

Components of Networks

•	Server - A server runs the network operating system and offers network services to users at their individual workstations. It offers services such as file, storage, security, resource management, user management. The types of server are 1. File server 2. E-mail server or E-mail gateway 3. Database server 4. Fax server 5. Print server 6. Backup and archive server
•	Workstations - When a computer is connected to a network, it becomes a node on the network and is called a workstation or client. A workstation’s job has been to execute program files retrieved from the network, and the server’s job is to deliver those files to the workstation.
•	NICs - Network Interface Cards provides interface between the server and workstations. Each computer attached to a network requires a network interface card (NIC) that supports a specific networking scheme. The type of NICs used usually decides the maximum data transfer rate
•	Cabling - The network cabling system is the media used to connect the server and the workstations together.
•	Shared resources and peripherals - Shared resources and peripherals include storage devices attached to the server, optical disk drives, printers, plotters, modem and other equipment that can be used by everyone on the network.