An Introduction to the use of LIBRARY, STUDY SKILLS & ICT I
Chapter Sixteen
. | I An Introduction to the use of ' 111 LIBRARY, STUDY SKILLS & ICT
controls.
2. Local Area Network (LAN):
This is a network which covers the inside of a building or group of buildings, and operated under a single administrative system. With a LAN, resources like printers, file servers, scanners, and the Internet can be shared among computers in the same building or group of buildings. ALAN can be connected to another LAN with the aid of telephone lines and radio waves. A system of LANs connected in this way is referred to as a WAN (Wide Area Network).
3. Metropolitan Area Network (MAN):
A Metropolitan Area Network is a network designed for a town or a city. It is larger than a LAN in terms of area coverage, but smaller than a WAN. A MAN is characterized by very high speed connections using co-axial cables, fiber optic cables and other digital media and may also be formed by a connection of LANs which may belong to different organizations.
4. WideArea Network (WAN):
A Wide Area Network covers a relatively large geographical area. Computers connected through a WAN are usually connected through public networks e.g. telephone systems, and use high speed communication links e.g. satellite, microwave links, and telephone lines. The cost of setting up a WAN is usually high, compared to the other networks. The largest WAN in existence is the Internet.
NETWORK TOPOLOGIES
Topology refers to the shape of a network or network's layout; That is, the arrangement and mapping of the elements o f a network to show the interconnection between the nodes. How the
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different nodes in a network are connected to each other and how they communicate is determined by the network's topology.The topology of a network can be physical or logical. The physical topology refers to the physical design of the network including the devices, locations and cable installations. The logical topology on the other hand refers to how data is transmitted in the network.
There are five common topologies used to establish computer network connections, viz: the Bus. Ring, Star Mesh, Tree and Hybrid topologies.
1. Bus topology
In a Bus design, a single linear network cable known as the Bus or the backbone runs through a building or campus, and all the nodes (computers) are linked along this single linear cable. Each end o f the cable is terminated using a special terminator. In this type of topology, if one node is damaged or develops a fault, all the other nodes may be affected as they all share the same cable for sending and receiving information. . It is the least expensive of all the network designs.
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An Introduction to the use or LIBRARY, STUDY SKILLS & ICT
A dvantages
* It is reliable in small networks as well as easy to use and understand.
* Compared to the other topologies, it requires the least amount o f cables to connect the nodes together and is therefore the least expensive among them.
* It is easy to extend the Bus topology in case there is need to add more nodes. The cables can be easily joined with a connector making a longer cable for
more computers or nodes to join in.
D isadvantages
* Heavy network traffic can slow aa Bus down considerably. Any o f the computers can transmit at any time and the networks do not coordinate when information is sent. As such, computers interrupting each other can use up a lot o f bandwidth.
* Each connection between two cables weakens the computer signal.
* The Bus configuration can be difficult to find and this may cause the whole network to stop working.
2. Ring topology
A ring topology is arranged in such a way that all the network cables pass from one node to another until all the nodes are arranged in the form o f a ring. There is a direct point to point line between two neighboring nodes i.e. the previous node and the next node. These connections can either be unidirectional or bi
directional. which ensures that the transmission made by a node goes through the whole ring and comes back to the transmitting node. A ring topology uses a token ring i.e. a small data packet
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that is continuously passed around the network. When a node needs to transmit, it reserves the token, then attaches the data packet to it and passes it to the next node.
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Advantages
* It offers high performance for a small number of nodes orb for a larger number where it has the same work load.
* It is easier to manage than Bus.
* Ring can span longer distances than other types of networks.
* It is also easily extendable.
Disadvantages:
* It is relatively expensive and difficult to install.
* Failureofonecom putercanaffectall theothers
* When there is a fault in the network, it is difficult to discover where the fault is.
* Adding and removing computers can disrupt the network.
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3. Star topology
The star topology uses a center hub which is the host and through which all the nodes or components are connected. The center hub may be a computer or a simple switch or just a common connection point. The computers at each of the terminals communicate across the network by passing data to the hub. It uses a significant amount of cable as each terminal is wired back to the center hub. The center hub makes all the routing decisions i.e. sending information to all the computers. Failure of one of the terminals do not affect the others, however, failure of the center hub affects all the terminals. It is usually used in LANs which span a larger geographical area than Bus can cope with.
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Star Topology Advantages
* It is more re lia b le -if one connection fails, it does not affect the others.
* The center hub provides a good place to diagnose network faults. If one computer fails, the whole
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