order to build a simple network, the first and foremost requirement
is to define the ‘structure of the network’. It must satisfy
the two questions
How are the computers going to be connected in the network?
• How will the computers communicate with each other?
technical terms, the structure of the network is called as the
network topology. Network Topology has two parts namely physical
and logical topology.
Topology tells us how to connect the computers whereas Logical
Topology tells us how the computers can communicate in the network.
begin with, one can think of physical topology as a network's
"shape" and so let’s take a look at the commonly used
“shapes” for designing a network...
A bus network has a common cable which connects all the devices
in the network
• This common cable functions as the backbone of the network
and all the devices share this cable.
• This cable is the lifeline of communication between the devices
• Now, in a bus network let us assume that computer A wants
to communicate with one another computer B. In such a case,
the computer A sends a message to B which all the computers
in the network can ‘see’ but only commuter B can respond.
As the name implies, the computers are connected to form a ‘ring’.
• In this network, one computer has exactly two neighbors for
• All messages in this network travel through this ring in the
• But a failure at one terminal will cause the whole network
to breakdown. This is the major disadvantage of a ring network.
• Here all the computers are connected to a central connection
point called as a hub.
• While comparing with a bus network, the star network uses
more cable but it is more reliable as the failure in any of
the star network cable will result in the failure of only one
terminal and not the entire network.
• Many home networks use star topology.
More complex networks can be built as hybrids of two or more
of the above basic topologies.
• Tree topologies are formed by integrating many star topologies.
• This is done by attaching the hub of each star network to
a ‘tree’ bus. The tree bus acts as the common bus for the several
• Now each hub functions as the "root" to its star
• This bus/star hybrid approach helps us to expand the network
in the future easily.
• Each computer is connected to every other computer in the
• So, the messages sent on a mesh network can take any of several
possible paths from one terminal to the other
• This network provides the best possible protection
• One excellent example to cite is the use of mesh networks
in the networked control systems of a nuclear power plant.
The two types are
• Token passing
Broadcast topology simply means that each computer sends its
data to all other computers. One good example is the Ethernet
Token passing controls network access by passing an electronic
token to a computer. When a computer receives the token, it
can send data. If the computer has no data to send, it passes
the token to the next computer and the process repeats itself.
Resources on the Internet :