This document discusses various network topologies including bus, ring, star, mesh, extended star, and hybrid topologies. It also distinguishes between physical and logical topologies. A physical topology refers to the actual layout and wiring of the network, while logical topology refers to how data is transmitted through the network. For example, while a network may have a star-shaped physical topology with cables connecting devices to a central hub, the hub may use a logical bus or ring topology to transmit data internally.

1. Network Topology
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2. Introduction
Physical and Logical Topologies
Topologies
Bus
Ring
Star
Extended Star
Mesh
Hybrid
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3. Physical vs. Logical Topology
The actual layout of a network and its media
is its Physical Topology
The way in which the data access the medium
and transmits packets is the Logical Topology
A glance at a network is not always revealing.
Cables emerging from a Hub does not make
it necessarily a Star Topology – it may
actually be a bus or a ring
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4. Bus Topology
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5. Bus Topology (5)
Advantages Disadvantages
Inexpensive to install No longer recommended
Easy to add stations Backbone breaks, whole
network down
Use less cable than Limited no of devices can
other topologies be attached
Works well for small Difficult to isolate problems
networks Sharing same cable slows
response rates
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6. Ring Topology
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7. Ring Topology (3)
Advantages Disadvantages
Data packets travel Requires more cable
at great speed than a bus
No collisions A break in the ring
Easier to fault find will bring it down
No terminators Not as common as
required the bus – less
devices available
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8. Star Topology
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9. Star Topology (3)
Advantages Disadvantages
Easy to add devices as the A star network requires more
network expands cable than a ring or bus
One cable failure does not network
bring down the entire Failure of the central hub can
network (resilience) bring down the entire
Hub provides centralised network
management Costs are higher (installation
Easy to find device and cable and equipment) than for most
problems bus networks
Can be upgraded to faster
speeds
Lots of support as it is the
most used
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10. Extended Star Topology
A Star
Network
which has
been
expanded to
include an
additional
hub or hubs.
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11. Mesh Topology (Web)
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12. Mesh Topology (2)
Not common on LANs
Most often used in WANs to interconnect
LANS
Each node is connected to every other node
Allows communication to continue in the
event of a break in any one connection
It is “Fault Tolerant”
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13. Mesh Topology (3)
Advantages Disadvantages
Improves Fault Expensive
Tolerance Difficult to install
Difficult to
manage
Difficult to
troubleshoot
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14. Hybrid Topology
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15. Logical Bus
•Modern Ethernet networks are Star Topologies (physically)
•The Hub is at the centre, and defines a Star Topology
•The Hub itself uses a Logical Bus Topology internally, to
transmit data to all segments
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16. Logical Bus
Advantages Disadvantages
A single node failure Collisions can occur
does not bring the easily
network down Only one device can
Most widely access the network
implemented topology media at a time
Network can be added
to or changed without
affecting other
stations
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17. Logical Ring
Data in a Star Topology can transmit data
in a Ring
The MAU (Multistation Access Unit) looks
like an ordinary Hub, but data is passed
internally using a logical ring
It is superior to a Logical Bus Hub – see
later slide
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18. Logical Ring (2)
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19. Logical Ring (3)
Advantages Disadvantages
The amount of data A broken ring will
that can be carried stop all
in a single message transmissions
is greater than on a A device must wait
logical bus for an empty token
There are no to be able to
collisions transmit
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20. Summary
Bus Topology
Ring Topology
Star Topology
Other Topologies
Logical Topologies
Questions and Answers
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