Download - Network topology....sajal
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Network Topology
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Introduction Physical and Logical Topologies Topologies
Bus Ring Star Extended Star Mesh Hybrid
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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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Bus Topology
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Bus Topology (5)Advantages Inexpensive to install Easy to add stations Use less cable than
other topologies Works well for small
networks
Disadvantages No longer recommended Backbone breaks, whole
network down Limited no of devices can
be attached Difficult to isolate problems Sharing same cable slows
response rates
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Ring Topology
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Ring Topology (3)Advantages Data packets travel
at great speed No collisions Easier to fault find No terminators
required
Disadvantages Requires more
cable than a bus A break in the ring
will bring it down Not as common as
the bus – less devices available
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Star Topology
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Star Topology (3) Advantages Easy to add devices as the
network expands One cable failure does not
bring down the entire network (resilience)
Hub provides centralised management
Easy to find device and cable problems
Can be upgraded to faster speeds
Lots of support as it is the most used
Disadvantages A star network requires
more cable than a ring or bus network
Failure of the central hub can bring down the entire network
Costs are higher (installation and equipment) than for most bus networks
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Extended Star Topology
A Star Network
which has been
expanded to include an additional
hub or hubs.
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Mesh Topology (Web)
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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”
CP2073 Networking 13
Mesh Topology (3)Advantages Improves Fault
Tolerance
Disadvantages Expensive Difficult to install Difficult to
manage Difficult to
troubleshoot
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Hybrid Topology
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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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Logical BusAdvantages A single node failure
does not bring the network down
Most widely implemented topology
Network can be added to or changed without affecting other stations
Disadvantages Collisions can occur
easily Only one device can
access the network media at a time
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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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Logical Ring (2)
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Logical Ring (3)Advantages The amount of
data that can be carried in a single message is greater than on a logical bus
There are no collisions
Disadvantages A broken ring will
stop all transmissions
A device must wait for an empty token to be able to transmit
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Summary Bus Topology Ring Topology Star Topology Other Topologies Logical Topologies Questions and Answers