• सुखार्थी त्यजते विद्यं विध्यार्थी त्यजते सुखम्सु sखर्थीन: कुतॊ विद्या कुतॊ विध्यार्थीन: सुखम् ||
  • “Luxury people leave knowledge, but a student leaves Luxury No knowledge for one who seeks Luxury, No luxury for student”
  • न चोर हार्यं न च राज हार्यं न भात्रू भाज्यं न च भारकारि |व्ययं कृते वर्धत एव नित्यं विद्याधनं सर्वधनप्रधानम ||
  • Cannot be snatched away by thief, cannot be snatched away by king, Cannot be divided among brothers, Not heavy either If spent daily, it always keeps growing. The wealth of knowledge is the precious of wealth of all”

Bus Topology




Introduction

Bus topology was the one of the first topologies used in the design of early local area networks. Ethernet LANs can use a bus topology, but they are less popular now. 

A bus topology is multipoint. One long cable acts as a backbone to link all the devices in a network as in figure.


Nodes are connected to the bus cable by drop lines and taps. A drop line is a connection running between the device and the main cable. A tap is a connector that either splices into the main cable or punctures the sheathing of a cable to create a contact with the metallic core. As a signal travels along the backbone, some of its energy is transformed into heat. Therefore, it becomes weaker and weaker as it travels farther and farther. For this reason there is a limit on the number of taps a bus can support and on the distance between those taps.

Advantages of Bus topology

Advantages of a bus topology includes:

1) Ease of installation: Backbone cable can be laid along the most efficient path, and then connected to the nodes by drop lines of various lengths, thus a bus uses less cabling than mesh or star topologies.

 For example:

 

In a star, six  network devices in the same room require six  lengths of cable reaching all the way to the hub/switch. In a bus, only the backbone cable stretches through the entire facility. Each drop line has to reach only as far as the nearest point on the backbone.

Disadvantages of Bus Topology

1) Fault Isolation  is difficult.

2) Not salable: It is difficult to add new devices.  As  bus is usually designed to be optimally efficient at the time of installation. Adding new devices may therefore require modification or replacement of the backbone.

3)  Signal reflected  at the taps can cause degradation in quality. It can be controlled by limiting the number devices and space between the  devices connected to a given length of cable.

 4) A fault or break in the bus cable stops all transmission, even between devices on the same side of the problem. The damaged area reflects signals back in the direction of origin, creating noise in both directions.

Related Question:

Question:    Explain the working of ring topology. Explain its advantages and disadvantages.     [5 marks]