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Computer Networks | Types of Network according to Physical Span | Advantages and Disadvantages of Computer Networks


Computer Network

According to Tanenbaum, computer network is a collection of ―autonomous‖ computers interconnected by a single technology. It is a collection of computers and other devices interconnected by communication channels that allow sharing of resources and information. The connection can be done as peer-to-peer or client/server.


Basic Elements of a Network:

        Data
a  collection of known facts and figures that can be represented and transferred in an electronic format, e.g. text, numbers, pictures, audio, video
        Sender
a  collection of User and Hardware, e.g. a computer
        Receiver
a  collection of User and Hardware, e.g. a computer
        Medium
the channel or path through which the data transfers, e.g. cable
        Protocol
system of digital message formats and rules for exchanging those messages

Applications of Computer Networks:

        Business Applications (Electronic Inventory, Information Systems, Email, Accounting/Payroll, OLTP, MIS/Reporting, Online Database, etc)
        Home Applications (Communication, Gaming, Ecommerce, Remote Sharing)
        Mobile Users (24x7 Online, GPS / Location tracking, Instant communication)

Advantages and Disadvantages of Computer Networks:

Advantage:

        Communication
        Sharing of files, data, and other types of information
        Sharing of network and computing resources
        Increased Storage Capacity
        Increased Performance
        Increased Cost Efficiency
        Increased Fault Tolerance / High Availability

Disadvantage:

        Security Issues
        Threat of Computer Viruses
        Dependency
        Interference with other technologies
        Expensive and difficult Setup
        Legal and Social Issues

Networks may be classified according to a wide variety of characteristics such as:

        Scale / Span of the network
        Topology the network follows,
        Medium used to transport the data,
        communications Protocol used,
        organizational Scope



Types of Network according to Physical Span:


Local Area Network (LAN)

A LAN connects network devices over a relatively short distance. A networked office building, school, or home usually contains a single LAN, though sometimes one building will contain a few small LANs (perhaps one per room), and occasionally a LAN will span a group of nearby buildings. In TCP/IP networking, a LAN is often but not always implemented as a single IP subnet. 
In addition to operating in a limited space, LANs are also typically owned, controlled, and managed by a single person or organization. They also tend to use certain connectivity technologies, primarily Ethernet and Token Ring. 
Most local area networks are built with relatively inexpensive hardware such as Ethernet cables, network adapters, and hubs. Some of the major technologies that the LANs use are Ethernet, Token Ring, FDDI, WiFi, etc.

Metropolitan Area Network (MAN)

A metropolitan area network (MAN) is a computer network that usually spans a city or a large campus. A MAN usually interconnects a number of local area networks (LANs) using a high-capacity backbone technology, such as fiber-optical links, and provides up-link services to wide area networks (or WAN) and the Internet. An example of MAN can be the Cable Television broadcasting.
Some technologies used for this purpose are Asynchronous Transfer Mode (ATM), FDDI, and SMDS, however, they are in the verse of being replaced by the Ethernet based MAN, also known as Metro-Ethernet. MAN can also use wireless technologies like microwave, radio, or infra-red laser links

Wide Area Networks (WAN)

WAN spans a large physical distance. It is a geographically-dispersed collection of LANs. A network device called a router connects LANs to a WAN. In IP networking, the router maintains both a LAN address and a WAN address. The Internet is the largest WAN, spanning the Earth.
A WAN differs from a LAN in several important ways. Most WANs (like the Internet) are not owned by any one organization but rather exist under collective or distributed ownership and management. WANs tend to use technology like ATM, Frame Relay and X.25 for connectivity over the longer distances. 




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