COMPUTER

NETWORKS II

CL ASS 12

CBSE
Transmission Media
• Transmission media are
communication channels of
network is the way how the
devices are getting
connected.

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 TRANSMISSION
MEDIA

UNGUIDED
GUIDED MEDIA
MEDIA
(WIRED)
(WIRELESS)

TWISTED PAIR COAXIAL

OPTICAL FIBRE MICROWAVES INFRARED
CABLE CABLE

RADIAWAVES LASER

SATELLITES
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Twisted Pair Cable
• Twisted Pair cable consists
of four insulated pairs of
wires twisted around each
other
• Twisting of wires reduces
crosstalk
• Crosstalk is the bleeding of a
signal from one wire to
another which can corrupt
signal and cause network
errors
• Used in telecommunication
and Ethernet network KRISH INFO TECH
 TWISTED PAIR CABLE
ADVANTAGES DISADVANTAGES

• Simple, easy to install and • Incapable to carry signal

maintain over long distances without
• Physically flexible a repeater (> 100)
• Low weight • Has low bandwidth
• Can be easily connected capabilities
• Very inexpensive • Unsuitable for broadband
applications

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 SHIELDED TWISTED PAIR CABLE
STP

Gives greater
protection from
Shielded individual Maximum length can Heavier and costlier
interference and
pair of wires be 100 m than UTP
crosstalk due to
shielding

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UNSHIELDED
TWISTED P
AIR CABLE
UTP

U S E D FO R VA R I E T Y O F E L E C TRO N I C C O MM U N I C AT I O N S

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COAXIAL CABLE
• Consists of a solid wire core
surrounded by one or more
foil or wire shields
• Each separated by plastic
insulator
• Inner core carries the signal
and the shield provides the
ground
• Suitable for high speed
communication
• Most common in cable TV
transmission
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 COAXIAL CABLE
ADVANTAGES DISADVANTAGES
• Data transmission is • Expensive compared to twisted
better than twisted pair cable pair cable
• Used for shared cable network • Not compatible with
• Used for twisted pair cable
broadband transmission
• Offer higher bandwidths
upto 400 Mbps

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 TYPES OF COAXIAL CABLE
THICKNET THINNET
• Thicker than thinnet • Thinner
• Segments can be upto 500 • Segment length can be
m long (while joining nodes) upto 185 m

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OPTICAL FIBERS
• Optical fibers consist of thin
strands of glass or glass like
material which carry light.
• Uses LEDs or LDs
• The data to be transmitted is
modulated onto the light beam
using frequency modulation
techniques
• The signals at the receiving end
are demodulated
• The bandwidth is very high
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OPTICAL FIBERS
• The fiber cable consists of three
pieces
(i) The core – the glass or
plastic through which the light
travels
(ii)The cladding – covering of
the core that reflects light back
to the core
(iii)Protective coating –
protects the fiber cable from
hostile environment
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 OPTICAL FIBERS
ADVANTAGES DISADVANTAGES
Immune to electrical and magnetic
interference • Installation problem
because cables are fragile
Highly suitable for harsh industrial • Connecting two fibers
environments together is a difficult process
• Connection losses
Guarantees secure transmission
• More difficult to solder
• Most expensive of all
Very high transmission capacity the cables

Used for broadband transmission

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 TYPES OF FIBRE OPTIC
SINGLE MODE
• Supports a segment length upto
5 km
• Bandwidth upto 10 Gbps

MULTIMODE
• Supports a segment length upto
1 km
• Bandwidth upto 100 Gbps

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GUIDED MEDIA COMPARED
Max
Bandwidth
Type Sub Type segment Installation Cost Interference
supported
length

UTP 100 m 40 Gbps Easy Cheapest High

Twisted
Pair Cable STP 100 m 500 Mbps Moderate Moderate Moderate

Thinnet 185 m 10 Mbps Easy Cheap Moderate

Coaxial
Cable Thicknet 500 m 10 Mbps Hard Moderate Low

Singlenode 2 km 100 Mbps Very hard Expensive None

Fiber
Optic
Cable Multinode 100 km 2 Gbps Very hard Expensive None
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 UNGUIDED MEDIA - MICROWAVE

• The microwave transmission is a line of sight transmission.

• Similar to radio and television signals
• Used for long distance communication
• Consists of a transmitter, receiver and the atmosphere
• Two directional parabolic antennas are mounted on towers, buildings
or hills to send and receive signals through air.
• Higher the tower, greater is the range

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 MICROWAVE
ADVANTAGES DISADVANTAGES

Cheaper (no cables or • Insecure communication

repeaters) • Antenna propogation
issue (reduces signal
strength)
Ease of communication
over difficult terrain • Susceptable to weather effects
• Bandwidth is limited
• Cost of design,
Ability to communicate implementation and
over oceans maintenance is high
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 RADIO WAVE
• Use radio frequencies. Uses transmitter
and receiver
• Both the transmitter and receiver use
antennas to radiate and fetch radio signals.
• Radio waves are omnidirectional, i.e., the signals are propagated in all
the directions.
• Radio waves cover a large area, and they can penetrate the walls, bricks,
woods.
• It provides a higher transmission rate.
• Examples: An FM radio, television, cordless phones.
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 RADIOWAVE
ADVANTAGES DISADVANTAGES
• Insecure
Offers mobility
• Susceptible to weather effects

Ease of
Cheaper (no
communication
cables or
over difficult
repeaters)
terrain

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SATELLITE (SATELLITE MICROWAVE)

• Satellite is a special type

of microwave
transmission medium
• It provides various types
of services such as
transmitting fax, voice
data, video, email
and other internet
applications.
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 SATELLITE
ADVANTAGES DISADVANTAGES
Quite large area is covered • Technological
limitations preventing the
deployment of large, high gain
No intercontinental cables required antennas on the satellite platform
• Over-crowding of
Heavy usage of available bandwidths
intercontinental traffic
• High investment and
Covers large areas of the Earth insurance cost
• High atmospheric losses
Particularly used for above 30GHz limit carrier
sparsely populated areas frequencies KRISH INFO TECH
 INFRARED

Uses infrared light to send data

Short range communication(approx. 5

meters) using wireless signals.
The data is transmitted through air and
can propagate in the open space
It can propagate throughout a room, but
will not penetrate walls.
Secured transmission

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 LASER
• The laser transmission requires direct
line of sight.
• It is unidirectional like microwave, but
has much higher speed than
microwaves.
• It requires the uses of laser
transmitter and the photosensitive
receiver at each end.
• It is point to point transmission
cleaning buildings.
• Major disadvantage of lasers is it can
be adversely affected by weather.

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Bluetooth
• Bluetooth is a wireless short
range ( up to 30 feet ( 10
meters)) communication
technology standard.
• With the bluetooth
technology, communication
takes place using low power
radio waves on a frequency
band between 2.400 GHz
and 2.483.5 GHz. KRISH INFO TECH
NETWORK TOPOLOGIES
• The pattern of
interconnectio Factors to be considered
n of nodes in a
network - Cost
Topology
Flexibility Reliability
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 TYPES OF NETWORK TOPOLOGIES

Point-to- Bus / Ring /

Star
Point Linear Circular

Fully
Tree Mesh
Connected

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POINT-TO-POINT TOPOLOGY
• Point-to-Point link basically relies upon 2 functions :
oTransmit
oReceive
• The main characteristics of P-P network is that each station
receives exactly from one transmitter and each transmitter
transmits to exactly one receiver.

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THE STAR
TOPOLOGY
• Each node (computer) is
directly connected to a central
device like HUB or switch.
• It is used in most existing
information networks involving
data processing or voice
communications.
• Eg. IBM 370 installations.
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 STAR TOPOLOGY
ADVANTAGES DISADVANTAGES
Ease of service
Long cable Difficult to
length expand
One device per connection

Centralized
control/problem diagnosis Central node
dependency

Simple access protocol

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 • Uses a common single length of
transmission
BUS OR LINEAR medium(coaxial cable) called backbone to
TOPOLOGY connect all the workstations.
• The bus has terminators at either end
which absorb the signal, removing it from
the bus.

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 BUS TOPOLOGY

ADVANTAGES DISADVANTAGES

Short cable length Fault diagnosis is difficult

Simple and easy to maintain wiring layout Fault isolation is difficult
Less installation cost
Repeater configuration
Resilient architecture

Easy to extend Nodes must be intelligent

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THE TREE
TOPOLOGY
• Uses combination of
bus and
star topologies
• Best suitable
for applications
having hierarchical
flow of data
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 TREE TOPOLOGY
ADVANTAGES DISADVANTAGES
Point to point
wiring
for individual
• Overall length of
segments each segment is limited
by the type of cabling
• If backbone line
breaks, entire segment
goes down
• More difficult to
Supported by configure and wire than
Flexible and several other topologies
scalable hardware and
software venders

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THE RING
TOPOLOGY
• Each node is connected to two
and only two neighbouring
nodes.
• Data travel in one direction only,
from node to node around the
ring.
• After passing through each node
it returns to the sending node
which removes it.
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Mesh topology
• In this topology each node is
connected to more than one node
to provide an alternative route in
the case the host is either down
or too busy.
• It is an extension to point to point
network.

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Fully
connected
• When in a network, there
is a direct link between
each host, then the
network is said to be fully
connected.
• This characteristics is
termed as full
connectivity.
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Factors to consider for topology selection

Cruciality of work - it is an important factor for example military networks

must not fail at any cost thus fully connected topology is preferred

Cost - keeping in mind the budget, you should decide about the topology. a
linear bus topology is least expensive whereas fully connected is most
expensive.

length of the cable needed - length of the cable must be saved on; linear
bus topology uses shorter lengths of the cable.

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Factors to consider for topology selection
Future growth - if a network has to grow in future then the
topology must support expansion. star topology helps in
expanding the network easily.

Communication media - you cannot use regular cables in hill

stations. for such conditions linear bus topologies are not
possible. the most common cable in schools is unshielded
twisted pair which is most often used with star topology.

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identifying nodes on a
computer network

• Two addresses plays an

important role in reaching
to the destination
computer:
oIP address
oMAC address

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 the IP address used by TCP/IP protocol to
reach to the destination network.

IP address
(Internet it is also a unique address for host.

Protocol
address) It is a local address, which may change
depending upon factors like connection
with the different gateway upon rebooting
the modem/ router or connecting to a
different network.
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Versions of IP addresses

• IPv4:
oInternet Protocol version 4 is A4 byte address written in the form
of dotted decimal notation, where each bytes value is separated
with a period as:
IPv4, the 32 bit address, could represent maximum4.3 billion unique address
• IPv6:
oInternet Protocol version 6 is a 16 byte address written in the
form of eight groups of hexadecimal numbers, separated with a
colon.
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