Introduction of Topology
Physical or Logical layout of structure called topology, in which all nodes are connected. Network topology is the arrangement of the elements of a communication network. The physical topology of LAN refers to the way in which the stations are physically interconnected. Each topology has its own strengths and weakness.
Feature of network topology: 1. The topology should be flexible. You can increase or decrease number of nodes in topology. 2. The cost of physical media and installation should be minimum. 3. The network should not have any single point of complete failures.
Types of Topologies
There are 5 types of topologies in computer network:
Bus Topology
A bus
topology is a network setup in which each computer and network
device are connected to a single cable or backbone. Bus topology also
called horizontal topology. In bus topology, multiple devices are connected one
by one, by means of connectors or drop cables. When one computer sends a signal
up (and down) the wire, all the computers on network receive the information,
but only one accepts the information (using address matching). The rest discard
the message.
Figure: Bus Topology Structure
The cable
to which the nodes connect is called a "backbone". A host on
a bus network is called a Station or workstation. Bus is passive
topology, because it requires termination. Cable cannot be left un-terminated
in a bus network. Terminators are required both ends of cable. Terminators were
the 50-ohm resistor that were connected to each end of cable.
Figure: Bus Topology Animation |
In a bus network, every station will receive all network traffic, and the traffic generated by each station has equal transmission priority. For example, station 1 wants communicate to station 2. But after sending data by station 1, all stations those are connected with bus will received data. In order for nodes to transmit on the same bus simultaneously, they use carrier sense multiple access (CSMA) protocol.
Advantages:
Easy to
use and easy to install.
Needs
fewer physical connectivity devices.
A
repeater can also be used to extend a bus topology.
Low cost.
Disadvantages:
Heavy
network traffic can slow a bus considerably.
It is
difficult to troubleshoot a bus topology.
Failure
of cable affects all devices on the network.
Difficult to add new node.
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