Transcript New Network Topologies

Network Topologies
Contents
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What is topology?
Types of topology?
Working of topologies
Flow of data with in topologies
Advantages and disadvantages
What is Topology?
The way devices on the network are
physically connected is known as topology.
or
The physical layout or the way in which
network connections are made is called a
topology.
Types of Topologies
Four Types of Topology
1.
2.
3.
4.
Bus Topology
Star Topology
Ring Topology
Mesh Topology
Bus Topology
In bus topology, all computers or network
nodes are connected to a common
communication medium. This medium is a
central wire called a “bus”.
Working of Bus Topology
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If one computer wants to send the data to
another computer in the network, it sends
the data & destination address via the
“bus”.
This data & address move from one end of
the network to the other.
Each computer checks this address & if it
matches with this computer, the computer
keeps the data. Otherwise…………….
the data moves to the next computer.
a network setup using bus topology
Data Flow
Communication on the bus topology occurs
in the following manner
Sending the signal
 Signal bounce back
 Terminators
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Sending Signal
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Data is sent to all of the computers on the
network
Transmission of data is bi-directional
Information is accepted only by the computer
whose address matches
Only one computer can send data on the cable at
a time
While two computers are communicating, all
other computers remain in wait.
Signal Bounce
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If the signals were allowed to continue, it
would keep bouncing back and forth along
the cable and stop other computers from
sending signals.
Backing of the signals is called bounce
back.
Terminators
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To stop the signals from bouncing,
terminator is placed at each end of the
cable to absorb free signals.
Absorbing the signal clears the cable, so
that other computers can send data.
Terminators are used to avoid collisions.
Bus topology uses coaxial cable as a medium.
Advantages
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It is very simple, easy to use & reliable for
very small networks
It is easy to install and configure
Least amount of cable is required to
connect the computers so it is less
expensive
It is easy to extend as two cables can be
joined to make a larger cable
Disadvantages
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It can support only a small number of computers.
As the number of computers increases, the
network get slower.
It is difficult to troubleshoot a bus. A cable break,
fault in any one computer or a loose connection
can breakdown the whole network.
Each connector reduces the strength of the
electrical signal
Star Topology
In star topology all the cables run from
the computers to a central location,
where they all are connected to a
device called “HUB”
Working of Star Topology
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If two computers want to share data , the
sender computer sends the data to the hub
& hub sends it to the receiving computer.
Each computer communicate with each
other by a central HUB.
So, hub provide a central connection point
for all computers across a network.
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Star topology uses a separate cable for each
computer, that cable connects a computer
to a central device i.e hub.
a network setup using star topology
Data Flow
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Multiple computers can send and receive
data at the same time
Each computer sends and receives data
using its own cable
Connectivity
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A specific device is used as a central
component called “hub”.
Advantages
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It is easy to modify & new computers can be
added to the central hub or any computer can be
removed without affecting the network.
It is usually easy to troubleshoot a star network.
If any computer in the star topology breaks down,
the network is not affected.
It is more flexible among the remaining topology.
It is much fast topology.
Multiple cable types supported by hubs.
Disadvantages
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If the central hub fails, the whole network
breaks down.
Star network requires more communication
cable than any other network.
It is more expensive.
Ring Topology
Ring topology looks like the bus topology
with connected ends.
But………………
In functionality it is different.
Working of Star Topology
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Each computer is connected to the next
computer in the form of ring.
Each retransmit what it receives from the
previous computer.
The message flow in one direction.
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Ring topology connects computers on a
single circle of cable.
There is no terminated ends
Signals travel around the loop in one
direction and pass through each computer.
Unlike bus topology, each computer acts
like a repeater to boost the signal and
send it to the next computer.
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It is called endless topology.
In ring topology, data flows in ring and in
clock-wise direction.
Ring topology is based on “Token Ring
Mechanism”.
a network setup using ring topology
Token Passing……..
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A token is passed around the network.
The computer that has token can transmit
data.
Token is passed from computer to
computer until it reaches to its destination.
The destination device returns an
acknowledgement to the sender.
The token is then given to another device,
giving it ability to transmit.
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The sending computer modified the token,
puts address with the data and sends it
around the ring.
Data passed by each computer until it finds
the computer with an address that matches.
Token is used as a carrier.
It is called token grab.
Advantages
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All computers on the ring have equal
access to the network.
It performs well under a heavy load.
Disadvantages
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Failure of one computer can affect the
whole network.
It is difficult to troubleshoot the ring
network.
Adding or removing a computer affects the
whole network.
a network setup using mesh topology