INTRODUCTION
In the past, the only way computers could share hardware resources: particularly printers or share data files was by copying the file on a diskette from the source computer and physically taking it to the destination computer or printing.
There was no way for them to share resources like printers, photocopier and other devices, except by taking what needs to be done to the computer thy has the resource needed. Thus, the need to link computer equipment together became necessary and this led to the Development of computer network.
DEFINITION
A computer network simply means a group of computers and associated equipments, which are connected together so that they can communicate with each other, as well as share resources. The shared resources could be printer, scanner, photocopier, hard disk, fax machine etc. Every Computer connected to the network is said to be on the network and would have a Network Interface Card(NIC). Each computer on the is referred to as a node. When a computer is turned on and is able to access the network, the computer is said to be on - line. When the computer is unable to access the network, it is said to be offl - line.
A computer network works by connecting two or more computers and associated devices together by means of a cable or other transmission media like through satellite technology. In addition to connecting computer and associated devices by means of a transmission Media, there has to be a set of rules and Instructions guiding the way the various connected computers and other devices communicate with each other. This set of instructions are known as communication software.
Computer network communication software is generally called network Operating system. Examples include Microsoft Windows NT, Novell Netware, etc.
Hence, a computer network comprises of both hardware Components as well as communication software.
In summary, all computer network must have the following:
• Something to share ( files, hardware resources, etc )
• A physical pathway ( communication channel)
• Rules of communication
COMPUTER NETWORK HARDWARE
Here are some examples of basic computer hardware:
1.1 Transmission Media: When data is transmitted between two hardware devices, a transmission medium is used. The commonly used media are twisted - pair cable, coaxial cable and Optical fibre. Where a physical connection is not practical, then radio, infared, microwave or laser technologies maybe used.
1.2 Twisted pairc cable is the commonly used Transmission medium because it is commonly available as our telephone lines. Microwave are high frequency radio signals and can be used when the distance between communicating device is much. This technology is often used in conjunction with the communication satellite.
1.3 Network sever: A network server is a computer that's specifically designed to provide services for other computers ( network clients) on the network.
1.4 Network clients: A network clients or clients accesses the resources available From the network server.
1.5 Modem: A modem is an electronic device that connects a computer to a transmission medium; say a telephone line.
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| External Computer Modem |
The Function of the modem is that it converts the signals coming from the computer to the form that the Transmission medium can understand and transmit. At the receiving end, another modem converts the signals from the Transmission medium back to the form a computer can understand and interpret. Most modern computers have in built modem. Therefore, once you acquire such computers you may not need to get another modem. But, if your computer does not have an in built modem, you may have to get an external modem.
TYPES OF COMPUTER NETWORKS
Computer networks come in different sizes. Different computer networks are usually classified according to their geographical size. The most common classifications are:
• Local Area Network (LAN)
• Metropolitan Area Network (MAN)
• Wide Area Network (WAN)
Local Area Network
A Local Area Network is a group of computers and network communication devices interconnected with a small area as a room, or building. For instance - school, offices, hospital, cybercafé, etc. A LAN uses only one type of Transmission medium (cabling). The characteristics of Local Area Network includes:
• It transfers data at high speed
• They are relatively error free
• They exist in a small geographical landmark
• Their technology is inexpensive
The components of a LAN are:
• User Workstation or personal computer
• Server
• Network Software
• Applications and
• Cabling and Transmission Media
A number of different ways exists by which to organize computer and it's peripherals to form a network and hence provide multiple ways of classifying networks. Local Area Networks are classified by their shape or Topology.
NETWORK TOPOLOGY
Topology refers to the manner in which a network is connected and shows the physical layout of the system resources such as computer, servers, and printers on the entire network. Each end unit on a network is called a node. The three most commonly topologies ate the star, bus, and ring. The choice of Topology depends on:
• The type of Application System being used on the network
• Physical location and distance of the node being serviced
• Reliability and Performance
• Expandability
• Cost
Star Network Topology
A stat network Topology generally has a central computer ( network server) at the hub, with terminals or nodes connected directly to it. In this structure, all messages pass through the central computer.
Advantages of star topology
• When one workstation fails, other workstation do not fail, because of the central hub
• Eliminates a number of lengthy cables runs if the hub is properly positioned
• Trouble shooting becomes easier due to shorter cable length
• Fewer problems caused by cut cabling, because all cables runs to a central hub
Disadvantages of the star Topology
• Potential for the central hub to become inactive, thereby forcing the entire network down
• Remote trouble shooting may not be possible due to lack of built in tolerance such as redundant disks.
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