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LAN (Local Area Network)
◦ A group of computers and
associated devices (printers, etc.)
◦ connected through a wired or
wireless medium
◦ by networking devices (hubs,
switches, routers)
◦ use protocols for
communication
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Topology
◦ Layout of how devices connect on network
 Wired Networks
 Wireless Networks
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Two types of connections:
 Dedicated or Point-to-point
◦ Direct connection between two computers
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Shared
◦ Multiple computers share the media
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Topology: Physical
layout of network.
Some of the popular
network topologies are:
◦ Star Topology
 Distributed Star
◦ Bus Topology
◦ Ring Topology
◦ Tree Topology
◦ Mesh
 Full Mesh
 Partial Mesh
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Point to Point network
Advantages
 Each network connection is
independent
Computer A
 It can be customised to suit the
type of data
◦ for example: data speed and
technology
It is easy to enforce security and
privacy.
Disadvantages

Not scalable for large
networks
Black links show four
connections from computer A to
all computers in the network
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Individual computers are connected to a
central point – a hardware device, called a
hub/switch .
Max distance between a computer and
hub/switch is restricted based on cable
used.
◦ With UTP cable, distance limited to
100m.
Popular topology for LAN (local area
networks)
Adv: Failure of any computer does not
affect other communications in the
network
Disadv: Failure of hub/switch can bring
the network down, also called SPF( Single
Point of Failure)
Star Topology
Extended Star Topology
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Also called a "hierarchical"
or "star of stars" topology
Nodes are connected in
groups of star-configured
workstations that branch out
from a single "root,"
The root node usually
controls the network and
sometimes network traffic
flow.
This topology is easy to
extend: when new users
need to be added
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Full Mesh
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Full mesh topology
◦ each node is physically
connected to every other node
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Adv: Highly fault tolerant: when
one node fails, traffic can easily be
diverted to other nodes
Disadv: Not scalable for large
networks
Partial mesh topologies are
popular for backbone
networks, where redundancy
is desirable
Partial Mesh
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Computers are connected to each
other to form a closed loop.
Common Examples
◦ FDDI Network
 Usually Fibre optic cable
based backbone networks
◦ Token Ring Network
 Example: IBM token ring
network
 Proprietary network
Adding and removing computers
disrupts the network.
What should be done to provide
redundancy in a ring topology ?
cable
computer
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Most wireless implementations are based on
◦ Star, tree or line topology
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Two modes:
◦ Ad hoc
 No need of central access point
 Problem: Not scalable
◦ Infrastructure (more common)
 Central Access Point (AP) is needed
 Scalable
Many wireless implementations are based on
more than one topology
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Star
• Hotspots, Offices and WISP's
• Point to Multipoint
• The most common infrastructure in wireless
networking
point-2-point
• Connecting two wireless clients directly
• Building to building (when one has Internet
connection and the other one does not)
point-2-point - Repeating
Necessary when direct line of sight
(LOS) is obstructed
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Mesh topologies are an
interesting option
mainly in
◦ dynamic environments
(urban areas) where
central infrastructure is
hard to implement
◦ when redundancy is
desired
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Typical cases are:
municipal networks,
campus networks etc.
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At the center of any cellular
technology is the cellular
transceiver, an omnidirectional antenna whose
range projects a circular
"footprint." This footprint is
the "cell" that gives cellular
technology its name
As the cellular user moves
from one cell to another, the
user's signal is transferred
from one antenna to another
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Use packet tracer to set up a network using following
Topologies
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Star
Distributed Star
Point-to-point
Tree
Refer to your task sheet for details
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