2. Content Transmission Media
Wired Media: Wireless Media:
Twisted Pair Radio Waves
Co-Axial Cable Microwaves
Opticl fibre Cable Infrared
Network Devices
Topologies
Bus
Star
Ring
Tree
Types of network
LAN
MAN
WAN
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3. What is Tranmission Media ?
In data communication,
• Transmission media is a pathway that carries the
information from sender to receiver.
• We use different types of cables or waves to transmit
data.
• Data is transmitted normally through electrical or
electromagnetic signals.
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5. Twisted-pair cable
A twisted pair consists of two conductors
Basically copper based
With its own plastic insulation, twisted together.
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6. Twisted Pair Description
• Provide protection against cross talk or interference(noise)
• One wire use to carry signals to the receiver
• Second wire used as a ground reference
• For twisting, after receiving the signal remains same.
• Therefore number of twists per unit length, determines the
quality of cable.
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8. Twisted Pair - Applications
• Very common medium
• Can be use in telephone network
• Connection Within the buildings
• For local area networks (LAN)
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10. Unshielded Twisted Pair (UTP):
Description
• Pair of unshielded wires
wound around each other
• Easiest to install
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11. Applications
UTP :
Telephone subscribers connect to the central telephone
office
DSL lines
LAN – 10Mbps or 100Mbps
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12. Advantages of UTP:
Affordable
Most compatible cabling
Major networking system
Disadvantages of UTP:
• Suffers from external Electromagnetic interference
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13. Shielded Twisted Pair (STP)
• Pair of wires wound
around each other
placed inside a
protective foil wrap
• Metal braid or sheath
foil that reduces
interference
• Harder to handle (thick,
heavy)
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14. STP Application
• STP is used in IBM token ring networks.
• Higher transmission rates over longer distances.
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15. Advantages of STP:
Shielded
Faster than UTP
Disadvantages of STP:
More expensive than UTP
High attenuation rate
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16. Co-axial cable carries signal of higher frequency ranges than twisted
pair cable
Co-axial Cable
• Inner conductor is a solid wire
• Outer conductor serves as a shield against noise and a second conductor
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17. Coaxial Cable Applications
• Most versatile medium
• Television distribution
• Long distance telephone transmission
• Can carry 10,000 voice calls simultaneously
• Short distance computer systems links
• Local area networks
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18. ADVANTAGES
Easy to wire
Easy to expand
Moderate level of Electro Magnetic Interference
DISADVANTAGE
Single cable failure can take down an entire network
Cost of installation of a coaxial cable is high due to its thickness
and stiffness
Cost of maintenance is also high
COAXIAL CABLE
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19. Fiber-Optic Cable
A fiber optic cable is made of glass or plastic and transmit signals in
the form of light.
Nature of light:
Light travels in a straight line
If light goes from one substance to another then the ray of light changes
direction
Ray of light changes direction when goes from more dense to a less dence
substance
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20. Optical fiber
• Uses reflection to guide
light through a channel
• Core is of glass or plastic
surrounded by Cladding
• Cladding is of less dense
glass or plastic
An optical fiber cable has a cylindrical shape
and consists of three concentric sections:
the core, the cladding, and the jacket(outer
part of the cable).
Jacket
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22. Areas of Application
Telecommunications
Local Area Networks
Cable TV
CCTV
Medical Education
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23. Optical Fiber Advantages
Greater capacity
Example: Data rates at 100 Gbps
Smaller size & light weight
Lower attenuation
Electromagnetic isolation
More resistance to corrosive materials
Greater repeater spacing facility
Example: After every 10s of km at least
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24. Optical Fiber Disadvantages
• Installation and maintenance need expertise
• Only Unidirectional light propagation
• Much more expensive
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26. Omnidirectional Antenna
Frequencies between 3 KHz
and 1 GHz.
Used for multicasts(multiple
way) communications, such
as radio and television, and
paging system.
Radio waves can penetrate
buildings easily, so that
widely use for indoors &
outdoors communication.
Unguided Media – Radio Waves
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27. Microwaves are ideal when large areas need to be covered
and there are no obstacles in the path
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Microwaves
28. Micro waves Transmission
• Microwaves are unidirectional
• Micro waves electromagnetic waves having frequency between 1 GHZ
and 300 GHZ.
• There are two types of micro waves data communication system :
terrestrial and satellite
• Micro waves are widely used for one to one communication between
sender and receiver,
example: cellular phone, satellite networks and in wireless
LANs(wifi), WiMAX,GPS
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29. Infrared
Frequencies between 300 GHz to 400 THz.
Used for short-range communication
Example: Night Vision Camera,Remote control, File
sharing between two phones,
Communication between a PC and peripheral device,
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30. Network Devices
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• LANs do not normally operate in isolation but
they are connected to one another or to the
Internet.
• Toconnect LANs, connecting devices are
needed and various connecting devices are
such as bridge, switch, router, hub, repeater.
31. • A hub is used as a central point of connectionamong
• media segments.
• Cables from network devices plug in to the portson
• thehub.
• Types of HUBS :
– A passive hub is just a connector. It connects the wires
• coming from different branches.
– The signal pass through a passive hub without regeneration
• or amplification.
– Connect several networking cables together
– Active hubs or Multiport repeaters- They regenerate or
• amplify the signal before they are retransmitted.
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Hubs
32. • A repeater is a device that operates only at the
PHYSICAL
• layer.
• A repeater can be used to increase the length of the network
• by eliminating the effect of attenuation on thesignal.
• It connects two segments of the same network, overcoming
• the distance limitations of the transmissionmedia.
• A repeaterforwards every frame; it has no
filtering capability.
• A repeater is a regenerator, not anamplifier.
• Repeaters can connect segments that have the same access.
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Repeaters
34. 34
Bridges
• Operates in both the PHYSICAL and the data linklayer.
• As a PHYSICAL layer device, it regenerates the signal it
receives.
• As a data link layer device, the bridge can check the
PHYSICAL/MAC addresses (source and destination)
contained in theframe.
• A bridge has a table used in filtering decisions.
• It can check the destination address of a frame and decide
• if the frame should be forwarded or dropped.
• If the frame is to be forwarded, the decision mustspecify
the port.
• A bridge has a table that maps address to ports.
• Limit or filter traffic keeping local traffic local yet allow
• connectivity to other parts (segments).
35. 35
A bridge connecting twoLANs
A bridge does not change the physical (MAC) addresses in a frame.
36. 36
Gateway
• Interchangeably used term router and gateway
• Connect two networks above the network layer of OSI
model.
• Are capable of converting data frames and network
protocols into the format needed by another network.
• Provide for translation services between different
computerprotocols.
• Transport gateways make a connection between two
networks at the transport layer.
• Application gateways connect two parts of an
application in the application layer, e.g., sendingemail
between two machines using different mail formats
• Broadband-modem-router is one e.g. of gateway
37. Network Topology
• Topology refers to the layout of connected
devices on a network.
• Here, some logical layout of topology.
oMesh
oStar
oBus
oRing
oTree and Hybrid
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39. 39
Mesh Topology
• Here every device has a point to point link to
every other device.
• Node 1 node must be connected with n-1
nodes.
• A fully connected mesh can have n(n-1)/2
physical channels to link n devices.
• It must have n-1 I/O ports.
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Mesh Topology
Advantages:
1. They use dedicated links so each link can only
carry its own data load. So traffic problem can be
avoided.
2. It is robust. If any one link get damaged it cannot
affect others.
3. It gives privacy and security.(Message travels
along a dedicated link)
4. Fault identification and fault isolation are easy.
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Star Topology
• Here each device has a dedicated point-to-point link
to the central controller called “Hub”(Act as a
Exchange).
• There is no direct traffic between devices.
• The transmission are occurred only through the
central “hub”.
• When device 1 wants to send data to device 2; First
sends the data to hub. Which then relays the data to
the other connected device.
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Star Topology
• Advantages:
1. Less expensive then mesh since each device is
connected only to the hub.
2. Installation and configuration are easy.
3. Less cabling is need then mesh.
4. Robustness.(if one link fails, only that links is
affected. All other links remain active)
5. Easy to fault identification & to remove parts.
6. No distruptions to the network then connecting(or)
removing devices.
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Star Topology
• Disadvantages:
1. Even it requires less cabling then mesh when
compared with other topologies it still large.(Ring or
bus).
2. Dependency(whole n/w dependent on one single
point(hub). When it goes down. The whole system is
dead.
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Bus Topology
• A bus topology is multipoint.
• Here one long cable act as a backbone to link all the
devices are connected to the backbone by drop lines
and taps.
• Drop line- is the connection b/w the devices and the
cable.
• Tap- is the splitter that cut the main link.
• This allows only one device to transmit at a time.
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Bus Topology
• Advantages:
1. Ease of installation
2. Less cabling
Disadvantages:
1. Difficult reconfiguration and fault isolation.
2. Difficult to add new devices.
3. Signal reflection at top can degradation in quality.
4. If any fault in backbone can stops all transmission.
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Ring Topology
• Here each device has a dedicated connection with two
devices on either side.
• The signal is passed in one direction from device to
device until it reaches the destination and each device
have repeater.
• When one device received signals instead of intended
another device, its repeater then regenerates the data
and passes them along.
• To add or delete a device requires changing only two
connections.
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Ring Topology
• Advantages:
1. Easy to install.
2. Easy to reconfigure.
3. Fault identification is easy.
Disadvantages:
1. Unidirectional traffic.
2. Break in a single ring can break entire network.
54. 54
Ring Topology
• Applications:
• Ring topologies are found in some office buildings or
school campuses.
• Today high speed LANs made this topology less
popular.
55. 55
Tree Topology
• Alternatively referred to as a star bus topology.
• Tree topology is one of the most common network
setups that is similar to a bus topology and a star
topology.
• A tree topology connects multiple star networks to
other star networks. Below is a visual example of a
simple computer setup on a network using the star
topology.
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Computer Network:
A network consists of two or more computers
that are linked in order to share resources,
exchange files, or allow electronic
communications.
The computers on a network may be linked
through cables, telephone lines, radio waves,
satellites, or infrared light beams
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Types Of Network
• Local Area Network
• Wide Area Network
• Metropolitan Area Network
59. Local Area Network:
• A local area network (LAN) is a group of computers and
associated devices that share a common
communications line or wireless link.
• Typically, connected devices share the resources of a
single processor or server within a small geographic
area .
• . A local area network may serve as few as two or three
users or as many as thousands of users.
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61. Wide Area Network:
• The WAN is a communications network that makes use
of existing technology to connect local
computer networks into a larger working network that
may cover both national and international locations.
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63. Metropolitan Area Network
(MAN):
• A metropolitan area network (MAN) is a network that
interconnects users with computer resources in a
geographic area or region larger than that covered by
even a large local area network but smaller than the
area covered by a wide area network (WAN).
• It is also used to mean the interconnection of several
local area networks by bridging them
with backbone lines
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