An Introduction to Computer Network

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A computer network is comprised of nodes and links, a node is the end point of any branch in a computer, a terminal device, workstation or interconnecting equipment facility.

There are different types of the topologies like bus, ring, tree, mesh etc. The following are the types of topology.

 1. Bus topology

This structure is very popular for local area networks. In this structure or topology, a single network cable runs in the building or campus and all nodes are linked along with this communication line with two endpoints called the bus or backbone.

Buss Topology

Advantages of Bus Topology

  • Reliable in very small networks as well as easy to use and understand.
  • Requires least amount of cable to connect the computers (nodes) together and therefore is less expensive than other cabling arrangements.
  • It’s easy to extend, two cables can be easily joined with a connector, making a longer cable for more computers to join the network.
  • A repeater can also be used to extend a bus configuration.

Disadvantages of Bus topology

  • Heavy network traffic can slow a bus considerably because any computer can transmit at any time. But networks do not coordinate when information is sent. Computer interrupting each other can use a lot of bandwidth.
  • Each connection between two cables weakens the electrical signal.
  • The bus configuration can be difficult to find and can cause the whole networks to stop functioning.

2. Ring topology

This is another structure for local area networks. In this topology, the network cable passes from one node to another until all nodes are connected in the form of a loop or ring. There is a direct point-to-point link between two neighboring nodes (the next and the previous). These links are unidirectional which ensures that transmission by a node traverses the whole ring and comes back to the node, which made the transmission.

Ring topology

Advantages ring topology

  •  Ring networks offer high performance for a small number of workstations or for larger networks where each station has a similar workload.
  • Ring networks can span longer distances than other types of networks.
  • Ring networks are easily extendable.
  • Unlike Bus topology, there is no signal loss in Ring topology because the tokens are data packets that are re-generated at each node.

Disadvantages ring topology

  •  Relatively expensive and difficult to install.
  • Failure of one computer on the network can affect the whole network.
  • It is difficult to find fault in a ring network.
  • Adding or removing computers can disrupt the network.

3. Star topology

Star topology uses a central hub through which, all components are connected. In a Star topology, the central hub is the host computer, and at the end of each connection is a terminal.

Star topology

Advantages of star topology

  •  It is more reliable (if one connection fails, it does not affect others)
  • The center of a star network is a good place to diagnose network faults and if one computer fails whole network is not disturbed.
  • It is easy to replace, install or remove hosts or other devices, the problem can be easily detected.
  • Use of multiple cable types in a same network with a hub.
  • It has good performance.

Disadvantages of star topology

  •  It is expensive to install as it requires more cable, it costs more to cable a star network because all network cables must be pulled to one central point, requiring more cable length than other networking topologies.
  • Central node dependency, if central hub fails, the whole network fails to operate.
  • Many star networks require a device at the central point to rebroadcast or switch the network traffic.

4. Mesh Topology

These devices are connected with many redundant interconnections between network nodes. In a well connected topology, every node has a connection to every other node in the network.

The cable requirements are high, but there are redundant paths built in. Failure in one of the computers does not cause the network to break down, as they have alternative paths to other computers.

Mesh Topology

Advantages of mesh topology

  • Yield the greatest amount of redundancy in the event that one of the nodes fails where network traffic can be redirected to another node.
  • Point-to-point link makes fault isolation easy.
  • Privacy between computers is maintained as messages travel along dedicated path.
  • Network problems are easier to diagnose.

Disadvantages of mesh topology

  •  The amount of cabling required is high.
  • A large number of input/output ports are required.



Prepared by:

Yakobo W. Mgemela-2014

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