Application of Computer and Information technology

This slide is about computer knowledge required for daily life computing operations

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Ref. PageChapter 17: Data Communications and Computer Networks
Slide 1/57

2. In this chapter you will learn about:
▪Basic elements of a communication system
▪Techniques, channels, and devices used to transmit data
between distant locations
▪Types of computer networks
▪Communication protocols and their use in computer networks
▪Internetworking tools and their use in building large
computer networks
▪Characteristics and advantages of distributed data
processing
Learning Objectives

3. Sender
(source)


Receiver
(sink)

Medium
Carries the message
Creates and sends
a message
Receives the
message
Basic Elements of a Communication System

4. Data Transmission Modes
Sender Receiver
(a) Simplex
Sender
(or Receiver)

Receiver
(or Sender)

OR
(b) Half-duplex
Sender
(and Receiver)

Receiver
(and Sender)

AND
(c) Full-duplex

5. ▪Bandwidth:
▪The capacity at which a network can transmit data
▪Range of frequencies available for data transmission
▪Higher the bandwidth, the more data it can transmit
▪Baud:
▪Unit of measurement of data transfer rate
▪Measured in bits per second (bps)
Data Transmission Speed

6. Types of data transmission media include:
▪Guided / Wired Media
▪Unguided / Wireless

Data Transmission Media

7. ▪Guided / Wired Media
▪Physical medium through which the signals are transmitted. E.g.,
▪Twisted-pair wire (UTP cable)
▪Coaxial cable
▪Optical fibre
▪Unguided / Wireless
▪An unguided transmission transmits the electromagnetic waves
without using any physical medium
▪Microwave system
▪Communications satellite
▪Infrared
Data Transmission Media

8. Twisted-Pair (UTP) Cable (Wired)
▪Unshielded Twisted-Pair (UTP) Cable
▪UTP consists of two insulated copper wires twisted around one
another.
▪This type of cable has the ability to block interference.
▪It is used for telephonic applications
▪Shielded Twisted-Pair (STP) Cable
▪This type of cable consists of a special jacket (a copper braid
covering or a foil shield) to block external interference.
▪It is used in fast-data-rate Ethernet and in voice and data
channels of telephone lines.

9. Coaxial Cable (Wired)
Central copper wire
PVC insulation

Copper mesh
Outer PVC shield
▪It has an outer plastic covering containing:
▪An insulation layer made of PVC or Teflon
▪2 parallel conductors each having a separate insulated
protection cover.
▪The coaxial cable transmits information in two modes:
▪Baseband mode(dedicated cable bandwidth)
▪Broadband mode(cable bandwidth is split into separate
ranges).
▪Cable TVs and analog television
networks widely use Coaxial cables.

10. Optical Fiber Communication System (Wired)
Electrical
signal
Optical fiber
Amplifier
Electrical
signal
Light to
electrical wave
converter
Electrical to
light wave
converter
Light waves
Sender Receiver
▪It uses the concept of refraction of light through a core made up
of glass or plastic.
▪The core is surrounded by a less dense glass or plastic covering
called the cladding.
▪It is used for the transmission of large volumes of data.
▪The cable can be unidirectional or bidirectional.

11. Microwave Communication System (Wireless)
Transmitting
station
Receiving
station
In between
repeaters
Transmitting antennas Receiving
antennas
Line of sight Line of sight Line of sight
▪It is a line of sight transmission
▪The sending and receiving antennas need to be properly aligned
with each other.
▪These are majorly used for mobile phone communication and
television distribution.

12. Satellite Communication System (Wireless)
Satellite in space
Transmitting
station on earth
6 GHz 4 GHz
Uplink Downlink
Receiving
station on earth
▪A satellite is a physical object that revolves around the earth at
a known height.
▪The satellite accepts the signal that is transmitted from the
earth station, and it amplifies the signal.
▪The amplified signal is retransmitted to another earth station.

13. Infrared (Wireless)
▪Infrared waves are used for very short distance communication.
▪They cannot penetrate through obstacles.
▪This prevents interference between systems.
▪Frequency Range:300GHz – 400THz.
▪It is used in TV remotes, wireless mouse, keyboard, printer, etc.

14. Digital and Analog Data Transmission
▪Analog signal: Transmitted power varies over a continuous
range. Example: sound, light, and radio waves
▪Digital signal: Sequence of voltage pulses represented in
binary form
▪Computer generated data signal is digital, whereas
telephone lines carry analog signals

15. ▪When digital data is to be sent over an analog facility,
digital signals must be converted to analog form
▪Conversion of digital signal to analog form is known as
modulation
▪Conversion of analog signal to digital form is known as
demodulation
▪Digital transmission of data is preferred over analog
transmission of data due to lower cost, higher
transmission speeds, and lower error rate
Digital and Analog Data Transmission

16. Analog and Digital Signals
v
t
0
111 1
000
(b)Digital signal
-v
0 1/f2/f

(a)Analog signal
Voltage
+v
t

17. Modems
▪Modem is short for MOdulator/DEModulator
▪Special device used for conversion of digital data to
analog form (modulation) and vice-versa (demodulation)
▪Essential piece of hardware where two digital devices
(say two computers) want to communicate over an
analog transmission channel (say a telephone line)

18. Multiplexing
▪Method of dividing physical channel into many logical
channels so that a number of independent signals may be
simultaneously transmitted
▪Electronic device that performs multiplexing is known as
a multiplexer
▪Multiplexing enables a single transmission medium to
concurrently transmit data between several transmitters
and receivers

19. Two Basic Methods of Multiplexing
▪Frequency-Division Multiplexing (FDM): Available
bandwidth of a physical medium is divided into several
smaller, disjoint logical bandwidths. Each component
bandwidth is used as a separate communication line
▪Time-Division Multiplexing (TDM): Total time
available in a channel is divided among several users,
and each user of the channel is allotted a time slice
during which he/she may transmit a message

20. 40 KHz
50 KHz
60 KHz
70 KHz
80 KHz
Signal-1
Signal-2
Signal-3
Signal-4
Signal-5

Channel
40 KHz
50 KHz
60 KHz
70 KHz
80 KHz
Signal-1
Signal-2
Signal-3
Signal-4
Signal-5
Sending endReceiving end
Modulator Demodulator
Frequency-Division Multiplexing
Frequency-Division Multiplexing

21. A3 A2 A1
B3 B2 B1
C3 C2 C1
Signal
A
Signal
B
Signal
C
C3C2C1
B3B2B1
A3A2A1
Channel
…
C2 B2 A2 C1 B1 A1
Time sliced
signals
Reassembled
signals
Sending
end
Receiving
end

Demulti-
plexer
Time-Division Multiplexing

22. Asynchronous and Synchronous Transmission
▪Two modes of data transmission on a communication line are
▪Asynchronous Transmission
▪synchronous Transmission
▪Asynchronous transmission
▪Sender can send data at any convenient time and the
receiver will accept it
▪Data is transmitted character by character at irregular
intervals
▪Well suited to many keyboard type terminals

23. Asynchronous and Synchronous Transmission
▪Synchronous transmission
▪Sender and receiver must synchronize with each other to get
ready for data transmission before it takes place
▪Entire blocks of characters are framed and transmitted
together
▪Well suited to remote communication between a computer
and such devices as buffered terminals and printers

24. Irregular time intervals
between two characters
Each character framed by
start and stop bits
Character Character Character
(a) Asynchronous transmission
CharChar CharChar CharChar
Indefinite time interval
between two blocks of data
A block of characters may
consist of hundreds of
characters
Trailer containing end of block
indication
Header containing synchronizing
and other information
(b) Synchronous transmission
Data Transmission

25. Switching Techniques
▪Data is often transmitted from source to destination
through a network of intermediate nodes
▪Switching techniques deal with the methods of establishing
communication links between the sender and receiver in a
communication network
▪Three commonly used switching techniques are:
▪Circuit switching: Dedicated physical path is established
between sending and receiving stations through nodes of
the network for the duration of communication

26. ▪Message switching: Sender appends receiver’s
destination address to the message and it is
transmitted from source to destination either by
store-and-forward method or broadcast method
▪Packet switching: Message is split up into fixed size
packets and each packet is transmitted independently
from source to destination node. Each packet is sent
with a header address which tells where its final
destination is. Either store-and-forward or broadcast
method is used for transmitting the packets. All the
packets of a message are re-assembled into original
message at the destination node
Switching Techniques

27. Network Topologies
▪Term network topology refers to the way in which
the nodes of a network are linked together
▪Major network topologies are:
▪Mesh Topology
▪Bus Topology
▪Star Topology
▪Ring Topology
▪Tree Topology
▪Hybrid Topology

28. Mesh Topology
▪In a mesh topology, every device is connected to another
device via a particular channel.
▪Examples are; Thermostats, security systems, smart
appliances, and lighting systems

29. Bus Topology
▪Bus Topology is a network type in which every
computer and network device is connected to a
single cable.
▪It is bi-directional.
▪It is a multi-point connection and a non-robust
topology because if the backbone fails the topology
crashes.
▪Examples are;
▪Ethernet LAN
▪Cable TV networks

30. Star Topology
▪In Star Topology, all the devices are connected to a
single hub through a cable.
▪This hub is the central node and all other nodes are
connected to the central node.
▪The hub is not an intelligent hub such as broadcasting
devices
▪The hub can be intelligent known as an active hub. Active
hubs have repeaters in them.
▪Coaxial cables or RJ-45 cables are used
to connect the computers.
▪Examples are; Airports, Hospitals,
Banks, and Educational Institutes.

31. Ring Topology
▪It forms a ring connecting devices with exactly two
neighbouring devices.
▪A number of repeaters are used for Ring topology with a
large number of nodes, because if someone wants to send
some data to the last node in the ring topology with 100
nodes, then the data will have to pass through 99 nodes to
reach the 100th node. Hence to prevent data loss repeaters
are used in the network.
▪The data flows in one direction
▪It can be made bidirectional by having 2 connections
between each Network Node, it is called Dual Ring
Topology.
▪Used in industrial control systems, where devices are
interconnected in a ring to monitor and control processes.

32. Ring Topology

33. Tree Topology
▪This topology is the variation of the Star topology.
▪This topology has a hierarchical flow of data
▪Tree topology is often used to connect multiple devices,
such as printers and computers, in a home or small
office.

34. Hybrid
Topology
▪This topological technology is the combination of all the
various types of topologies.
▪Hybrid Topology is used when the nodes are free to take
any form.

35. Network Types
▪Networks are broadly classified into three types:
▪Local Area Network (LAN)
▪Connects a small group of computers in a given
geographical area
▪Metropolitan Area Network (MAN)
▪Comparatively a wider network that covers large
regions- like towns, cities, etc.
▪Wide Area Network (WAN)
▪It spans to an even larger locality.
▪It has the capacity to connect various countries
together.

36. Network Types
Parameter LAN MAN WAN
Network Ownership The LAN is private.
Hospitals, homes, schools,
offices, etc., may own it.
The MAN can be both
private or public. Many
organizations and telecom
operators may own them.
The WAN can also be both
private or public.
Speed LAN offers a very high
Internet speed.
MAN offers a moderate
Internet speed.
WAN offers a low Internet
speed.
Delay in Propagation It faces a very short
propagation delay.
It faces a moderate
propagation delay.
It faces a high propagation
delay.
Faulty Tolerance The LAN exhibits a better
fault tolerance than the
rest of the networks.
The MAN exhibits a lesser
fault tolerance.
The WAN also exhibits a
lesser fault tolerance.
Congestion The congestion in the
network is very low.
It exhibits a higher
network congestion.
It exhibits a higher
congestion in the network.
Communication AllotmentLAN typically allows a
single pair of devices to
establish a communication.
But it may also support
more computers.
MAN allows multiple
computers to interact
simultaneously with each
other.
A huge group of computers
can easily interact with
each other using the WAN.
Uses Schools, homes, colleges,
hospitals, offices, etc., can
privately use it.
It basically covers a city, a
small town, or any given
area with a bigger radius
than the LAN.
It covers an entire country,
a subcontinent, or an
equivalent area.

37. Network Models
▪Client-Server Network:
▪Broadly used network model.
▪Clients and server are differentiated.
▪In Client-Server Network, Centralized server is
used to store the data because its management is
centralized.
▪In Client-Server Network, Server respond the
services requested by the Client.

38. Network Models- Client Server Network

39. Network Models – Peer to Peer Network
▪This model does not differentiate the clients and
the servers
▪Each and every node is itself client and server.
▪In Peer-to-Peer Network, each and every node can
do both request and respond for the services.
▪In peer-to-peer networks, the nodes both consume
and produce resources.
▪Whereas in client-server networks, an increase in
nodes causes the server to become overloaded.
▪The majority of contemporary operating systems,
including Windows and Mac OS, come with
software to implement peer to peer network

40. Network Models- Peer to Peer Network