When a machin
sends a
data, it will be
associated wi
is
An address field
all the others.
specifies for which destination It
sent.
receivea
the
1.09
Topologies
(a) Easy
A topology is a model of network
the devices are connected with the
(ii) Star
Bus
(ii) Aing
(iv) Mesh
cabling
(c)
Less cabling
(c)Less
does not affect the network.
Failure of one device
d)
(v) Hybrid
(a)
(b)
figure given below
shows the bus
extent
Disadvantages
i ) Bus topology
The
to instali the
suited for temporary rbtworks
(b) Well
which
network. The nes h
are the few standard network topologios.
Thev
They are follow
)
Asra
Advantages
fault
Reconfiguration and
Difficult to add
in
(c) Break
topoloou
blogy.
new
finding
are dificult.
devices.
trunk cable
stops all
transmission in
the
in the
run.
network.
(d)
Maintenance cost may be the
highest
long
ti) Star topology
Drop line
The
Tap
Trunk
cable
Terminator
this.
topology devices
are
of star
below shows the structure
topology.
As shown in the above
figure the bus topology
connects the devices with the trunk link
by using taps. Each
end of the trunk line ends with a
device caled
terminator
figure given
Node
Hub
Tn
uniquely identified by network
address. Using this address
only the devices can
communicate among one another. If a
device wants to send
a
message to a destination device, it
broadcasts the
message with destination address
through the trunk line.
devices are connected
Asshown in the above figure all
This acts
central device called hub or switch.
Each device in the
topology checks the address of the data in
the bus (trunk line).
If the address matches, the
to
a
controller
corresponding device receives the data else the signal
identified by a network address.
th
travels
an on
the bus.
as a
of the topology. In this topology devices are uniquely
1.10
1.11
If a device wants to send a data to another devica
sends it to the controller. The controller receives the da
and re-directs it to the proper address called
destination
a
Advantages
(a) Easy to add new devices.
(b) Less expensive.
(a) Easy to install and reconfigure.
to monitor and trouble shoot.
(b) Adding or removing a device is easy.
(e) Since it is having multilinks, the failure of one link does
not affect the topology.
Disadvantages
(a) More cable required.
(a) If a node fails to transmit data then the entire network
fails.
(b) If the controller (hub) fails, entire network fails.
it supports one direction, there is
of data traffic problem in the link.
(b) Since
iRing topology
figure given
below shows the
ing topology.
a
possibility
(iv) Mesh topology
Device 1
The figure given below shows the structure of mesh
Device 6
topology.
Device 2
Device 5
Device 3
Device4
As shown in the
above
connected in both direction to form
figure,
each device is
The devices are
ring.
uniquely identified by means of a network
address. Signal is
passed along the ring in one
another.
(c) The length of cable required is short.
(d) Fautt finding is simple.
Diadadvantages
The
device
wants to send a data to
another, it sends
the data to the adjacent device along the
ring direction. If the
destination address matches t receives the data, else, the
sianal is boosted and is sent to the next device. This
process
is repeated until the destination address is reached.
a
Advantages
(c) Easy to instal and reconfigure.
(d) Easy
If
a
direction from
one
device
to
112
As shown in
with all other
identified
topology
devices in the
by
to send a
the above figure
means
data to
of a network
another, it
each device
The devices are
address.
can
f a
send
1.13
is conne
nec
nique
device
uni
directly
wan
.t
to
destination device.
Star
Hub
Advantages
(a)
Data
can
trom diferent
be transmitted
devic.
ice
simultaneously.
(b)Ifone device in the network
path to do
BUs
fails,
there is an
alterna
communication.
Ring
(c) Expansion and modification can be carried o
Ou
without affecting the network.
Disadvantages
(a) High chance of redundancy in, many connections
(b) High cost.
Advantages
(a) Fault detection and troubleshooting is easy.
(c) Set-up and maintenance is very difficult.
(b)
(v) Hybrid topology
By
combining
more than one
network
topology
() These networks can be designed according to the
hybrid topology
The following figure shows the
hybrid topology formed by one star, one bus and one
is formed.
requirement of the organization using the available
star
ring topology
It is easy to increase the size of the network by adding new components with out affecting the network.
resources.
Disadvantages
(a)
It is very
difficult
design.
(b) The hubs (connection points) used to
different network are very expensive.
to
connect two