Monday 18 June 2012


COMPUTER TECHNOLOGY

COMPUTER NETWORKS
·         A computer network, often simply referred to as a network, is a collection of computers and other hardware components interconnected by communication channels that allow sharing of resources and information. Simply, more than one computer interconnected through a communication medium for information interchange is called a computer network.

TYPE OF COMPUTER NETWORK.

LOCAL AREA NETWORK :


Network that connects computers and devices in a limited geographical area such as home, school computer laboratory and office building.


METROPOLITAN AREA NETWORK :


High speed area network that connects local area networks in a metropolitan area such as city or town.

WIDE AREA NETWORK:


Networks that covers a large geographical area such as country or the world.

Type of Network Architecture.

Client/Server :
  • One computer acts as a sever tat provides services and the other computers (client) on teh network request services from the services from the server.

-A server is a computer that control access to the hardware, software and other resources on the networks and provides a centralized storage area for program. there are many type of server such as mail server, web server, file server and ftp server.

            -A client is a computer that requests services from a server computer.
            -Client/server networks are typically used when there is a constant need to access large files and applications or when multiple users want to share peripherals.


Peer-to Peer:

Network that typically connects fewer than 10 computers.  All computers in the network have equal capabilities to use the resources (hardware, software, data and files) available on the network. With peer-to peer, there is no central server.


THREE TYPES OF NETWORK TOPOLOGY.
 
 
Topology
Explanation
Ring topology
·         A cable forms a closed loop(ring) with all computers and devices arranged along the ring.
·         Data transmitted on the ring networks travels from device around the entire ring, in one direction.
·         The ring topology primarily is used for LANs, but also is used in WANs.
Bus topology
·         A bus network comsists of a single central cable, to which all computers and other devices connect.
·         Data, instructions, and informations is transmitted in both directions.
·         Bus networks are popular on LANs because they are inexpensive and easy to install.
Star topology
·         All of the computers and devices (node) on the network connet to central device, thus forming a star.
·         The central devices that provides a common connection point fro nodes on the network is called the hub.
·         All data that transfer from one node to another passes through the hub in one direction.


Topology
Bus
Ring
Star
Diagrams



Central Device
Not available
Not availabe
Hub or Switch
Data Transmitted
Both direction
One direction
Both direction
Installation and Maintenance
Easy
Difficult
Easy
If one node fails
Does not effects the rest of the nodes.
 The entire network stop working.
Does not effects the rest of nodes.

WIRED COMMUNICATION MEDIA

  • Wired communication refers to the data over the wire-based communication technology. Also waveguide (electromagnetism), used for high-power applications, is considered as wired line.
Alternatively, communication technologies that don't rely on wires to transmit data are considered wireless.

TYPE OF WIRED COMMUNICATION MEDIA
a)         Twisted Pair Cable.

·         Twisted pair cable consists of two strands of insulated copper wire, twisted around each other.  This twisted  pair configuration some-what reduces interference from electrical field.
·         Data is transmit through electric signal.


b)         Coaxial Cable.


·         Coaxial cable, or coax, has an inner conductor surrounded by a flexible, tubular insulating layer, surrounded by a tubular conducting shield.
·         Coaxial cable differs from other shield cable used for carrying lower-frequency signals, such as audio signals.

c)          Fibre Optic.

·         Method of transmitting information from one place to another by sending pulses of light through an optical fibre. The light forms an electromagnetic carrier wave that is modulated to carry information.

WIRELESS COMMUNICATION MEDIA

*      Wireless telecommunications is the transfer of information between two or more points that are not physically connected. Distances can be short, such as a few metres for television remote control, or as far as thousands or even millions of kilometres for deep-space radio communications. It encompasses various types of fixed, mobile, and portable.

TYPE OF WIRELESS COMMUNICATION MEDIA
a)          Infrared.
·         Infrared(IR) short-range communication, for example from consumer IR devices such as remote controls or via Infrared Data Association(IrDA).
·         Infrared devices often must be within about 5 meters.

b)          Radio Wave.
·         Bluetooth technology uses short-range radio wave to transmit data between two Bluetooth devices. To communicate each other, Bluetooth devices often must be within about 10 meters.
·         WiFi (Wireless Fidelity) transfer data between devices at rate of 11-54 Mbps. To communicate each other, WiFi devices often must be within about 30 meters.

c)           Satellite.
·         Satellite is a space station that receives microwave signals from an earth-based station, amplifies the signals, and broadcasts the signal back over a wide area to any number of earth-based stations.

COMMUNICATION PROTOCOL
*      A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications. A protocol may have a formal description.
*      TCP/IP is short for Transmission Control Protocol/Internet Protocol. TCP/IP is a network standard, specially a protocol, that defines how messages are routed from one end of a network to the other, ensures the data arrives correctly.
     FDDI is a Fiber Distributed Data Interface (FDDI) is a network protocol that is used primarily to interconnect two or more local area networks, often over large distances. The access method used by FDDI involves token-passing. FDDI uses a dual ring physical topology. Transmission normally occurs on one of the rings; however, if a break occurs, the system keeps information moving by automatically using portions of the second ring to create a new complete ring.


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REFERENCES
ü Books
·         SCORE A INFORMATION AND COMMUNICATION TECHNOLOGY by Ismail bin Shaari.

ü Websites
     http://www.edrawsoft.com/Network-Protocol.php