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(b) The hardware required to connect each link (I/O ports and cable) can be prohibitively
expensive.

(c) Set-up and maintenance of this topology is very difficult. Even administration of the network
is tough.
CTM: When there is a point-to-point link between each computer in a network, it forms mesh topology.

8.11.2 Star Topology

In star topology, each communicating device is connected
to a central controller called hub. (A hub is a hardware

device used to connect several computers together.)
Unlike mesh topology, the devices in star topology
send and receive data indirectly; the data passes to and
from the hub. If the data is required to be sent from one
computer and received by another computer, then this
can be accomplished only by the central controller as
each data is first sent to the hub, which then relays that
data to the destination computer.
Fig. 8.20: Star Topology
Most popular and widely used LAN technology, Ethernet,
currently operates in Star Topology.

Advantages of Star Topology

(a) Fewer wires are required as compared to mesh topology which, thus, reduces the number
of input/output ports.
(b) Installation and maintenance of network is easy and takes less time.

(c) It is easy to detect faults in this network as all computers are dependent on the central hub.
This means that any problem which makes the network non-functioning can b e traced to
the central hub.

(d) The rate of data transfer is fast as all the data packets or messages are transferred through
central hub.
(e) As the nodes are not connected to each other, any problem in one node does not hamper the
performance of other nodes in the network.

(f) Removal or addition of any node in star topology can take place easily without affecting the
entire performance of t h e network.
Disadvantages of Star Topology

(a) Extra hardware is required for installation of central controller known as hub.

(b) All nodes of star topology are dependent on central hub and, therefore, any problem in the
Computer Networks
hub makes the entire network shut down.
(c) The performance of the entire network is directly dependent on the performance of the
hub. If the server is slow, it will cause the entire network to slow down.

(d) More cabling is required in star topology as compared to any other topology (ring, bus,
tree) as all nodes are directly connected to a central hub.
8.19