network topology

1. Definition
Types of Topology
Network Topologies
 Bus Topology
 Ring Topology
 Star Topology
 Tree Topology
 Mesh Topology
 Hybrid Topology
References
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CONTENTS
2

2. Two types of Serial Transmission
1. Synchronous Transmission
2. Asynchronous Transmission
Network Topology

3. Synchronous Transmission
1. Transmission is done under the control of a common master clock
2. The bits are synchronised to the reference clock
3. No start and stop bits instead the bytes are transmitted in a continuous
stream of bits.
4. There is an inter block idle time that are filled with idle character, flag is
prefixed to each block to identify to each block.

4. Characteristics of Synchronous ransmission
1. There are no spaces in between characters being sent.
2. Timing is provided by modems or other devices at the end
of the transmission.
3. Special ’syn’ characters goes before the data being
sent.
4. The syn characters are included between chunks of data
for timing functions.
Examples of Synchronous Transmission
1. Chatrooms
2. Video conferencing
3. Telephonic conversations
4. Face-to-face interactions

5. Characteristics of Asynchronous Transmission
Each character is headed by a beginning bit and concluded
with one or more end bits.
There may be gaps or spaces in between characters.
Examples of Asynchronous Transmission
1. Emails
2. Forums
3. Letters
4. Radios
5. Televisions

6. Synchronous vs. Asynchronous Transmission
In synchronous transmission data is transmitted in the form of chunks, while in
asynchronous transmission data is transmitted one byte at a time.
Synchronous transmission needs a clock signal between the source and target to
let the target know of the new byte. In comparison, with asynchronous
transmission, a clock signal is not needed because of the parity bits that are
attached to the data being transmitted, which serves as a start indicator of the
new byte.
The data transfer rate of synchronous transmission is faster since it transmits in
chunks of data, compared to asynchronous transmission which transmits one byte
at a time.
Asynchronous transmission is straightforward and cost-effective, while
synchronous transmission is complicated and relatively pricey.
Synchronous transmission is systematic and necessitates lower overhead figures
compared to asynchronous transmission.

7. DEFINITION
 Network topology refers to the
physical or logical layout of
a network.
 It defines the way different
nodes are placed and
interconnected with each
other.
 Network topology may describe
how the data is transferred
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8. Types of topology
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There are two types of network
topologies:
Physical Topology
logical Topology
Physical Topology emphasizes the physical
layout of the connected devices and
nodes.
logical Topology focuses the pattern of
data transfer between network nodes.

9. Both Physical and
Logical Network
Topologies can be
categorized into 6
basic types:
Bus Topology
Ring Topology
Star Topology
Tree Topology
Mesh Topology
Hybrid Topology
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10. BUS TOPOLOGY
In Bus Topology, all
devices are connected
sequentially to the same
backbone or transmission
line.
A signal from the source
travels in both
directions to all
stations until it finds
the intended recipient.
If the station address
matches the intended
address, it accepts the
data otherwise ignored.
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11. Bus Topology is further divided into 2 types:
Linear Bus- All of the nodes of the network are
connected to a common transmission medium
which has exactly two endpoints.
Distributed Bus- All of the nodes of the
network are connected to a common transmission
medium which has more than two endpoints.
A fully connected Bus Topology is having only 1
linking channel.
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12. Use: Local Area Network(LAN)
Advantage-
Less expensive and easy to implement.
Disadvantage-
Since one cable is utilized, when it breaks,
the entire network will be terminated.
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13. RING TOPOLOGY
In Ring Topology, all
network devices are
connected
sequentially to a
backbone forming a
physical ring.
Here the data flow is
unidirectional, so
when a device sends
data, it must travel
through each device
on the ring until it
reaches its
destination.
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14. A fully connected Ring Topology is having (n)
linking channels.
Use: Local Area Network(LAN)
Advantage-
Less expensive in nature.
Disadvantage-
Since one cable is used, when it fails, the
whole network will be effected.
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15. STAR TOPOLOGY
In Star Topology, all
the nodes in the
network are connected
to a central device
called Hub or Switch
via cables.
All traffic is
controlled by the
Hub. Devices transfer
the data to each
other only through
the Hub not directly.
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16. Star Topology is further divided into 2 types:
Extended Star- A network which has one or more
repeaters used to extend the maximum distance
between the Hub and other devices.
Distributed Star- A network which is composed
of individual networks connected in a linear
fashion with no central connection.
A fully connected Star Topology is having (n)
linking channels.
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17. Use: Client-Server network
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Advantage-
Simple, Easy to design and implement.
Disadvantage-
• Since a central Hub controls all devices, if
it fails, the entire network will be
terminated.
• Wiring is more, so highly expensive.

18. TREE TOPOLOGY
In Tree Topology, a
root node is
connected to two or
more sub-level nodes,
which themselves are
connected
hierarchically to
sub-level nodes.
Here the top level node
is called Root and
the low level node is
called Child.
It is the combination
of Bus and Star
Topology.
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19. Use: Cable TV technology, Wireless networks for
military, Mobile applications
Advantage-
• Easier fault identification and isolation.
• It is scalable; Secondary nodes allow more
devices to be connected to a central
node.
Disadvantage-
• Maintenance of the network may be difficult when
the network spans a great area.
• Since it is a variation of bus topology, if the
backbone fails, the entire network is
crippled.
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20. MESH TOPOLOGY
In Mesh Topology,
each node is
directly connected
to some or all the
other nodes present
in the network.
A fully connected
Mesh Topology is
having n(n-1)/2
linking channels.
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21. Mesh Topology is further divided into 2 types:
Fully Connected- A network in which every node is
connected to each other. It doesn't need to
use switching nor broadcasting.
Partially Connected- A network in which some of
the nodes are connected to more than one
other.
Use: Long distance transmission of data
It has more disadvantages so that rarely used.
Disadvantage-
• Message delay may be high.
• Requires more cabling, hence costly.
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22. HYBRID TOPOLOGY
Hybrid Topologies
use a combination
of any two or
more topologies
in such a way
that the
resulting network
does not exhibit
one of the
standard
topologies.
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23. A hybrid topology is always produced when
two different basic network topologies are
connected.
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For Example: Star-Ring network and Star-Bus
network

24. REFERENCES
Data Communications and Networking : Behrouz A.
Forouzan, Tata MCGraw-Hill, 4th Ed
Computer Networks: A.S. Tannenbum, D.Wetherall,
Prentice Hall, Imprint of Pearson,5th Ed
 http://en.wikipedia.org/wiki/Network_topology
 http://www.techopedia.com/definition/5538/network-
topology
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