Fundamentals of Data Communication and Computer Networks

Chapter 1
Fundamentals of Data
Communication and Computer
Networks
Mr. C. P. Divate
Department of Computer Engineering

Contents
1.0 Objectives
1.1 Data & Information
1.2 Data Communication
1.2.1 Characteristics of Data Communication
1.2.2 Components of Data Communication
1.3 Data Representation
1.4 Data Flow
1.4.1. Simplex
1.4.2. Half Duplex
1.4.3. Full Duplex
1.5 Computer Network
1.5.1 Categories of a network
1.6 Protocol
1.6.1 Elements of a Protocol
1.7 Standards In Networking
1.7.1 Concept of Standard
1.7.2 Standard Organizations in field of Networking
1.8 Review Questions

1.2 Data Communication
• Data communication is the process to exchange of data
between two devices via some form of transmission
medium such as a wire cable or wireless medium.

1.2 Data Communication in Computer Network
• Data communication In case of computer networks is
the process of exchange of data between two devices
over a transmission medium or wireless medium.

1.2 Data Communication Systems
• Data communication Systems This involves a
communication system which is made up of hardware
and software.
• Hard Ware Part : It involves the sender and receiver
devices and the intermediate devices through which the
data passes.
• Software part (Protocol): It involves certain rules which
specify what is to be communicated, how it is to be
communicated and when. It is also called as a Protocol.

• Data communication Systems This involves a
communication system which is made up of hardware
and software.

• Software part (Protocol): It involves certain rules which
specify what is to be communicated, how it is to be
communicated and when. It is also called as a Protocol.

1.3 Components of a data communication system
1. Message
• Message is the data / information to be communicated by the sender to
the receiver.
• A message could be in any form, it may be in form of a text file, an audio
file, a video file, etc.
• The message can be of any size from one byte to Mega byte.
• Message can be of either Analog or Digital signal format depending on
transmission media(wired / wireless).

Figure 1.1 Components of a data communication system
2. Sender
• The sender is any device that is capable of sending the data (message).
• The sender device could be in form of a computer, mobile, telephone,
laptop, video camera, or a workstation, etc.
• The sender device must keep high memory buffer for the sending large data
/ information to medium.
• Sender should transmit its data with speed as that of transmission media
bandwidth(speed).
• Sender device must be loaded with network operating system that contains
all protocols of transmission.

3. Receiver
• It is a device that receives message.
• Same as sender, receiver can also be in form of a computer, telephone
mobile, workstation, etc.
• The receiver device must keep high memory buffer for the large large data /
information from medium.
• Receiver should receives its data with speed as that of transmission media
bandwidth(speed).
• Receiver device must be loaded with network operating system that
contains all protocols of transmission.

4. Transmission Medium
• It is the path by which the message travels from sender to receiver.
• It can be wired or wireless and many subtypes in both.
• Examples are twisted pair cable, fiber optic cable, radio waves,
microwaves, etc.
• The data transmission rate for medium is depending of transmission
medium.
• Data transmission rates various from 10 Mbps to 1000 Gbps
• The data transmission medium is connected to different networking
devices between sender and receiver.

5. Protocols
• It is an agreement of set or rules used by the sender and receiver to
communicate data.
• A protocol is a set of rules that governs data communication.
• A Protocol is a necessity in data communications without which the
communicating entities are like two persons trying to talk to each other in
a different language without know the other language.
• It provides security to data messages on transmission medium.
• Examples OSI Model, TCP/IP, UDP / IP, FTP, DHCP, PPP etc.

Figure 1.1 Characteristics of Data Communication
The effectiveness of any data communications system depends upon the
following fundamental characteristics:
1. Delivery: The data should be delivered to the correct destination and correct
user.
2. Accuracy / Integrity : The communication system should deliver the data
accurately, without introducing any errors. The data may get corrupted during
transmission affecting the accuracy of the delivered data.
3. Timeliness: Audio and Video data has to be delivered in a timely manner
without any delay; such a data delivery is called real time transmission of data.
4. Jitter: It is the variation in the packet arrival time. Uneven Jitter may affect the
timeliness of data being transmitted.

5. Error detection & Correction: The data communication systems should
communicate with automatic detect errors and correct errors in messages
during the transmissions. e.g. Parity check, Checksum, CRC
6. Routing-Routing means to send data to appropriate destinations. It is used to
find shortest path among devise or server.
7. Reliable: It is measured by frequency of failure, the time it takes a link to
recover from a failure, and the network’s robustness.
8. Flow Control: At the time of transmission of data, source computer is
generating data faster than receiver device capable to receive it. To handle
such problem, there is some kind of flow control mechanism used.

9. Security: Security issues include protecting data from unauthorized access and
virus. Network must be secured. The data that is sent should reach its
destination safely without any third-party reading or altering or destroying the
data in the midway.
10. Performance: It means achieving higher throughput(number of Users in
network) and smaller delay times(data transmission delay between sender and
receiver)

1.17
Figure 1.2 Data flow / Transmission modes in communication systems
(simplex, half-duplex, and full-duplex)
• The way in which data is transmitted from one device to another device is
known as transmission mode.
• The transmission mode is also known as the communication mode.
• Each communication channel has a direction associated with it, and
transmission media provide the direction. Therefore, the transmission mode
is also known as a directional mode.
• The transmission mode is defined in the physical layer.

1.18
The Transmission mode is divided into three categories
• Simplex mode
• Half-duplex mode
• Full-duplex mode

1.19

1.20
Figure 1.2 Data flow / Transmission modes in communication systems - simplex
• In Simplex mode, the communication is unidirectional, i.e., the
data flow in one direction.
• A device can only send the data but cannot receive it or it can
receive the data but cannot send the data.
• This transmission mode is not very popular as mainly
communications require the two-way exchange of data.
• The main advantage of the simplex mode is that the full
capacity of the communication channel can be utilized during
transmission.

1.21
Examples of Simplex Transmission modes:
• The simplex mode is used in the business field as in sales that
do not require any corresponding reply.
• The radio station is a simplex channel as it transmits the signal
to the listeners but never allows them to transmit back.
• Keyboard and Monitor are the examples of the simplex mode as
a keyboard can only accept the data from the user and monitor
can only be used to display the data on the screen.

1.22
Advantage of Simplex mode:
• In simplex mode, the station can utilize the entire bandwidth of
the communication channel, so that more data can be
transmitted at a time.
Disadvantage of Simplex mode:
• Communication is unidirectional, so it has no inter-
communication between devices.

1.23
Figure 1.2 Data flow / Transmission modes in communication systems - Half-
Duplex mode
• In a Half-duplex channel, direction can be reversed, i.e., the station can
transmit and receive the data as well.
• Messages flow in both the directions, but not at the same time.
• The entire bandwidth of the communication channel is utilized in one
direction at a time.
• In half-duplex mode, it is possible to perform the error detection, and if
any error occurs, then the receiver requests the sender to retransmit the
data.

1.24
Duplex mode

1.25
Duplex mode (Stop – and – Wait Protocol)

1.26
Duplex mode (Stop – and – Wait Protocol with sliding window)

1.27
Duplex mode
Examples of Half Duplex Transmission modes:
• A Walkie-talkie: In Walkie-talkie, one party speaks, and another party
listens. After a pause, the other speaks and first party listens. Speaking
simultaneously will create the distorted sound which cannot be
understood.
• WhatsApp Messenger, Facebook messenger, Mobile Messenger etc.
• ATM Machine, Bus Ticket machines

1.28
Duplex mode
Advantage of Half-duplex mode:
• In half-duplex mode, both the devices can send and receive
the data and also can utilize the entire bandwidth of the
communication channel during the transmission of data.
Disadvantage of Half-Duplex mode:
• In half-duplex mode, when one device is sending the data,
then another has to wait, this causes the delay in sending
the data at the right time.

1.29
Figure 1.2 Data flow / Transmission modes in communication systems - Full-
Duplex mode
• In Full duplex mode, the communication is bi-directional, i.e., the data
flow in both the directions.
• Both the stations can send and receive the message simultaneously.
• Full-duplex mode has two simplex channels. One channel has traffic
moving in one direction, and another channel has traffic flowing in the
opposite direction.
• The Full-duplex mode is the fastest mode of communication between
devices.

1.30
Duplex mode(sliding window protocol)

1.31
Duplex mode
Examples of Full Duplex Transmission modes:
• Telephone/ Mobile communication: The most common example of the
full-duplex mode is a telephone network. When two people are
communicating with each other by a telephone line, both can talk and
listen at the same time.

1.32
Duplex mode
Advantage of Full-duplex mode:
• Both the stations can send and receive the data at the
same time.
Disadvantage of Full-duplex mode:
• If there is no dedicated path exists between the devices,
then the capacity of the communication channel is divided
into two parts.

PROTOCOL
• A Protocol is one of the components of a data communications system.
Without protocol communication cannot occur.
• The sending device cannot just send the data and expect the receiving device
to receive and further interpret it correctly.
• When the sender sends a message it may consist of text, number, images, etc.
which are converted into bits and grouped into blocks to be transmitted and
often certain additional information called control information is also added
to help the receiver interpret the data.

PROTOCOL
• A Protocol is one of the components of a data communications system.
Without protocol communication cannot occur.
• The sending device cannot just send the data and expect the receiving device
to receive and further interpret it correctly.
• When the sender sends a message it may consist of text, number, images, etc.
which are converted into bits and grouped into blocks(packets/frames) to be
transmitted

1.35
PROTOCOL
• Certain additional information called control information is also added to
help the receiver interpret the data.
• For successful communication to occur, the sender and receiver must agree
upon certain rules called protocol.
• A Protocol is defined as a set of rules that governs data communications.
• A protocol defines what is to be communicated, how it is to be
communicated and when it is to be communicated.

1.36
PROTOCOL

1.37
TCP/IP PROTOCOL

1.38
TCP/IP PROTOCOL

Elements of a Protocol
There are three key elements of a protocol:
A. Syntax:
• It makes the structure or format of the data.
• It arranges the data frames in a particular order.
B. Semantics:
• It tells the meaning of each section of bits and indicates the
interpretation of each section.
• It also tells what action/decision is to be taken based on the
interpretation.
• Error Handling.
C. Timing:
• It tells the sender about the readiness of the receiver to receive the
data.
• It tells the sender at what rate the data should be sent to the
receiver to avoid overwhelming the receiver.

STANDARDS IN NETWORKING
• Standards are necessary in networking to ensure interconnectivity and
interoperability between various networking hardware and software
components.
• Without standards we would have proprietary products creating
isolated islands of users which cannot interconnect.

Concept of Standard
• Standards provide guidelines to product manufacturers and vendors to
ensure national and international interconnectivity.
• Data communications standards are classified into two categories:
1. De facto Standard- designed by facts in communication
• These are the standards that have been traditionally used
and mean by fact or by convention
• These standards are not approved by any organized body
but are adopted by widespread use.
2. De jure standard designed by law in communication
• It means by law or by regulation.
• These standards are legislated and approved by an body
that is officially recognized.

De Facto De Jure
Factual Recognition is known as De Facto Legal Recognition is known as De Jure
De Facto is temporary. It is not permanent
like De Jure.
De Jure which is a legal recognition is a
permanent recognition
It is a temporary and provisional recognition
which can be withdrawn.
it cannot be withdrawn.
The recognition by De Facto is based on a
factual situation and is not a process of law.
De Jure is a recognition given after following due
procedure of law.
State Succession rules do not apply in de
facto
Under De Jure, rules of state succession are
applied.
De Facto Government cannot recover a state
asset or public debt
Only a de jure government can recover state
assets or public debt.
Membership to the United Nations is not
possible even if there is a de facto
recognition by the majority of states.
A state can get United Nations membership if the
majority of nations bestows de jure recognition.
The State which receives De facto
recognition will have 2 rival governments
The State which receives De Jure recognition
has only 1 Government.

Standard Organizations in field of Networking
Standards are created by standards creation committees, forums, and
government regulatory agencies.
• Examples of Standard Creation Committees :
i. International Organization for Standardization (ISO)
ii. International Telecommunications Union – Telecommunications
Standard (ITU-T)
iii. American National Standards Institute (ANSI)
iv. Institute of Electrical & Electronics Engineers (IEEE)
v. Electronic Industries Associates (EIA)
• Examples of Forums
i. ATM Forum - Asynchronous Transfer Mode
ii. MPLS Forum - Multiprotocol Label Switching
iii. Frame Relay Forum
• Examples of Regulatory Agencies:
i. Federal Communications Committee (FCC)

DATA & SIGNALS
To transmit, data over medium, it must be transformed to electromagnetic
signals. • Data can be Analog or Digital:

ANOLOG DATA & SIGNALS
• Analog data refers to information that is continuous; ex. sounds made by
a human voice
• Analog Signal: They have infinite values in a range.
• Signals which repeat itself after a fixed time period are called Periodic
Signals.
• In data communications, we commonly use periodic analog signals and
non-periodic digital signals.

DIGITAL DATA & SIGNALS
• Digital data refers to information that has discrete states. Digital data take
on discrete values.
• For example, data are stored in computer memory in the form of Os and
1s.
• Digital Signal: They have limited number of defined values
• Signals which do not repeat itself after a fixed time period are called Non-
Periodic Signals.
• In data communications, we commonly use periodic analog signals and
non-periodic digital signals.

DATA & SIGNALS
Analog signals Digital signals
There is a continuous
representation of signals in analog
signals.
There is a discontinuous
representation of signals in digital
signals.
Analog signals are difficult to get
analyzed at first.
Digital signals are easy to analyze.
Analog signals are more accurate
than digital signals.
Digital signals are less accurate.
Analog signals take time to be
stored. It has infinite memory.
Digital signals can be easily stored.
To record an analog signal, the
technique used, preserves the
original signals.
In recording digital signal, the sample
signals are taken and preserved.

DATA & SIGNALS
Analog signals. Digital signals
Analog signals produce too much
noise.
Digital signals do not produce noise.
Applications of analog signals are
Human voice, Thermometer, Analog
phones etc.
Examples of digital signals are
Computers, Digital Phones, Digital
pens, etc.
Represented by sine waves Represented by square waves
Records sound waves as they are Converts into a binary waveform.
Only be used in analog devices.
Suited for digital electronics like
computers, mobiles and more.

DATA & SIGNALS
• BIT LENGTH or Bit Interval (Tb)
• It is the time required to send one bit.
• It is measured in seconds.
• BIT RATE / bits per second
• It is the number of bits transmitted in one second. It is expressed as
bits per second (bps).
• Relation between bit rate and bit interval can be as follows Bit rate =
1 / Bit interval

DATA & SIGNALS
• Baud Rate
• It is the rate of Signal Speed, i.e the rate at which the signal
changes.
• A digital signal with two levels ‗0‘ & ‗1‘ will have the same baud rate
and bit rate & bit rate.
• The diagram below shows three signal of period (T) 1 second
a) Signal with a bit rate of 8 bits/ sec and baud rate of 8 baud/sec
b) Signal with a bit rate of 16 bits/ sec and baud rate of 8 baud/sec
c) Signal with a bit rate of 16 bits/ sec and baud rate of 4 baud/sec

Conversion of Analog signals to Digital signals
• Most of the image / audio sensors are in the analog signal, and digital
processing cannot be applied on it, as it requires infinite memory to
store because signals have an infinite value that is why we cannot
store it.
• A digital signal is superior to an analog signal because it is more
robust to noise and can easily be recovered, corrected and amplified.
• For this reason, the tendency today is to change an analog signal to
digital data. In this section we describe two techniques, pulse code
modulation and delta modulation.
• To create a digital image we can convert data into digital form.
• For the conversion there are three steps:
1. Sampling
2. Quantization
3. Encoding

4.53
Figure 4.21 Components of PCM encoder

i) Sampling
• In analog signals, there are continuous electrical signals
that vary with time. With the help of subsystem, a sampler
extracts continuous signals for the sampling of signals.
• Sampling is done along the x-axis of signals that continuously differs
with time. It is divided into two category one is sampling and other is
down-sampling.
• In down-sampling, the range of values on the x-axis is always less.

i) Sampling
 Analog signal is sampled every TS secs.
 Ts is referred to as the sampling interval.
 fs = 1/Ts is called the sampling rate or sampling
frequency.
 There are 3 sampling methods:
 Ideal - an impulse at each sampling instant
 Natural - a pulse of short width with varying
amplitude.
 Flattop - sample and hold, like natural but
with single amplitude value
 The process is referred to as pulse amplitude
modulation PAM and the outcome is a signal with
analog (non integer) values

4.56
Figure 4.22 Three different sampling methods for PCM

Quantization
• It is a process of image processing, in which continuous and
time-varying values of analog signals are divided into non-
overlapping discrete and unique values assigned to each
subrange.
• Sampling and quantization are opposite to each other.
Sampling is done along the x-axis but quantization is done
along the y-axis.
• In the image processing, the sampled image is considered as a
digital value. When there is a transition of states between
time-varying values of image function and its digital equivalent
signifies quantization.

Quantization

ii) Quantization
 Sampling results in a series of pulses of
varying amplitude values ranging between
two limits: a min and a max.
 The amplitude values are infinite between
the two limits.
 We need to map the infinite amplitude
values onto a finite set of known values.
 This is achieved by dividing the distance
between min and max into L zones, each of
height 
 = (max - min)/L

Quantization Levels
 The midpoint of each zone is assigned a value
from 0 to L-1 (resulting in L values).
 Each sample falling in a zone is then
approximated to the value of the midpoint.
Quantization Zones
 Assume we have a voltage signal with amplitutes
Vmin=-20V and Vmax=+20V.
 We want to use L=8 quantization levels.
 Zone width = (20 - -20)/8 = 5
 The 8 zones are: -20 to -15, -15 to -10, -10 to -5, -5
to 0, 0 to +5, +5 to +10, +10 to +15, +15 to +20
 The midpoints are: -17.5, -12.5, -7.5, -2.5, 2.5, 7.5,
12.5, 17.5

Assigning Codes to Zones
 Each zone is then assigned a binary code.
 The number of bits required to encode the zones, or
the number of bits per sample as it is commonly
referred to, is obtained as follows:
nb = log2 L
 Given our example, nb = 3
 The 8 zone (or level) codes are therefore: 000, 001,
010, 011, 100, 101, 110, and 111
 Assigning codes to zones:
 000 will refer to zone -20 to -15
 001 to zone -15 to -10, etc.

Figure 4.26 Quantization and encoding of a sampled signal

PCM Decoder
 To recover an analog signal from a digitized signal
we follow the following steps:
 We use a hold circuit that holds the amplitude
value of a pulse till the next pulse arrives.
 We pass this signal through a low pass filter with
a cutoff frequency that is equal to the highest
frequency in the pre-sampled signal.
 The higher the value of L, the less distorted a signal
is recovered.
Conversion of Digital signals to Analog signals

Figure 4.27 Components of a PCM decoder

Figure 4.31 Data transmission methods

Figure 4.32 Parallel transmission

Figure 4.33 Serial transmission

In asynchronous transmission, we send
1 start bit (0) at the beginning and 1 or
more stop bits (1s) at the end of each
byte. There may be a gap between
each byte.
Note

Asynchronous here means
“asynchronous at the byte level,”
but the bits are still synchronized;
their durations are the same.
Note

Figure 4.34 Asynchronous transmission

In synchronous transmission, we send
bits one after another without start or
stop bits or gaps. It is the responsibility
of the receiver to group the bits. The bits
are usually sent as bytes and many
bytes are grouped in a frame. A frame is
identified with a start and an end byte.
Note

Figure 4.35 Synchronous transmission

Isochronous
 In isochronous transmission we cannot
have uneven gaps between frames.
 Transmission of bits is fixed with equal
gaps.

Fundamentals of Computer Networks
 Definition of Computer Networks
A computer network is a group of computers linked
to each other that enables the computer to
communicate with another computer and share
their resources, data, and applications.

 Need of Computer Networks
 High Communication speed
 File sharing
 Back up and Roll back is of data is easy
 Software and Hardware sharing
 Security
 Scalability
 Reliability
 Email
 Internet access
 eCommerce
 Resource sharing

 Applications of Computer Networks
 Email- e.g. gmail, rocketmail, rediffmail etc.
 File Transfer Protocol (FTP)- playstore, youtube etc.
 Terminal Emulation (TELNET)- playstore
 eCommerce- amazon, flipcart, banking etc.
 video conferencing and chatting-zoom, googlemeet
whatsapp etc.
 Online gaming
 File sharing- Google drive etc.
 Sharing resources- anydesk etc.

 Computer Network Architecture
 Computer Network Architecture is defined as the
physical and logical design of the software,
hardware, protocols, and media of the transmission
of data.
 Simply we can say that how computers are
organized and how tasks are allocated to the
computer.
 The two types Computer Network Architectures are:
 Peer-To-Peer network
 Client/Server network

 Peer-To-Peer Network Architecture

 Peer-To-Peer Network Architecture
 Peer-To-Peer network is a network in which all the computers
are linked together with equal privilege and responsibilities for
processing the data.
 Peer-To-Peer network is useful for small environments,
usually up to 10 computers.
 Peer-To-Peer network has no dedicated server.
 Special permissions are assigned to each computer for
sharing the resources, but this can lead to a problem if the
computer with the resource is down.
 Peer is the computer that works as client as well as server
with limited access to its resources.

 Advantages Of Peer-To-Peer Network:
 It is less costly as it does not contain any dedicated server.
 If one computer stops working but, other computers will not
stop working.
 It is easy to set up and maintain as each computer manages
itself.
 Disadvantages Of Peer-To-Peer Network:
 In the case of Peer-To-Peer network, it does not contain the
centralized system. Therefore, it cannot back up the data as
the data is different in different locations.
 It has a security issue as the device is managed itself.
 Difficult to avoid data replication.
 Difficult to maintain version control of data.

 Client/Server Network Architecture

 Client/Server Network Architecture
 Server is the computer that provides different services to all
other computers in network.
 Client is the computer that accepts services from server
machines.
 Client/Server network is a network model designed for the end
users called clients, to access the resources such as songs,
video, etc. from a central computer known as Server.
 The central controller is known as a server while all other
computers in the network are called clients.
 A server performs all the major operations such as security
and network management.
 A server is responsible for managing all the resources such as
files, directories, printer, etc.
 All the clients communicate with each other through a server.
For example, if client1 wants to send some data to client 2,
then it first sends the request to the server for the permission.
The server sends the response to the client 1 to initiate its
communication with the client 2.

 Advantages Of Client/Server Network:
 A Client/Server network contains the centralized system.
Therefore we can back up the data easily.
 A Client/Server network has a dedicated server that improves
the overall performance of the whole system.
 Security is better in Client/Server network as a single server
administers the shared resources.
 It also increases the speed of the sharing resources.
 Avoid duplication of data on all computers
 Version control as no duplication of data on other computers
only single and final copy of data is maintained centrally.

 Disadvantages Of Client/Server Network:
 Client/Server network is expensive as it requires the server
with large memory.
 A server has a Network Operating System(NOS) to provide the
resources to the clients, but the cost of NOS is very high.
 It requires a dedicated network administrator to manage all
the resources.
 Requires backup of data at serverside.

Classification of Computer Networks
 A computer network can be categorized by their
size. A computer network is mainly of four types:
i. LAN(Local Area Network)
ii. PAN(Personal Area Network)
iii. MAN(Metropolitan Area Network)
iv. WAN(Wide Area Network)

 PAN (Personal Area Network):
 Personal Area Network is a network arranged within an
individual person, typically within a range of 10 meters.
 Personal Area Network is used for connecting the computer
devices of personal use is known as Personal Area Network.
 Thomas Zimmerman was the first research scientist to bring
the idea of the Personal Area Network.
 Personal Area Network covers an area of 30 feet.
 Personal computer devices that are used to develop the
personal area network are the laptop, mobile phones, media
player and play stations.
 Connection can be made available for Bluetooth with infrared
signals.

 There are two types of Personal Area Network:
 Wired Personal Area Network
 Wireless Personal Area Network
 Wireless Personal Area Network: Wireless Personal Area
Network is developed by simply using wireless technologies
such as WiFi, Bluetooth. It is a low range network.
 Wired Personal Area Network: Wired Personal Area Network
is created by using the USB.

Advantages Of PAN Network:
 Wire Requirement
 Device Connectivity
 Portability
 Reliable
Disadvantages Of Peer-To-Peer Network:
 Area Coverage
 Signal Interference
 Data Transfer Rate
 Cost

 LAN (Local Area Network):
 Local Area Network is a group of computers connected to each
other in a small area such as building, office.
 LAN is used for connecting two or more personal computers
through a communication medium such as twisted pair,
coaxial cable, etc.
 It is less costly as it is built with inexpensive hardware such
as hubs, network adapters, and ethernet cables.
 The data is transferred at an extremely faster rate in Local
Area Network.
 Local Area Network provides higher security.

 LAN (Local Area Network):

Advantages Of LAN Network:
 Resource Sharing
 Software Applications Sharing
 Easy and Cheap Communication
 Centralized Data
 Data Security
 Internet Sharing
 LAN (Personal Area Network):

Disadvantages Of LAN Network:
 High Setup Cost
 Privacy Violations
 Data Security Threat
 LAN Maintenance Job
 Covers Limited Area
 Connects Limited users
 LAN (Personal Area Network):

 MAN (Metropolitan Area Network):
 A metropolitan area network is a network that covers a larger
geographic area by interconnecting a different LAN to form a
larger network.
 Government agencies use MAN to connect to the citizens and
private industries.
 In MAN, various LANs are connected to each other through a
telephone exchange line.
 The most widely used protocols in MAN are RS-232, Frame
Relay, ATM, ISDN, OC-3, ADSL, etc.
 It has a higher range than Local Area Network(LAN).

 MAN is used in communication between the banks in a
city.
 It can be used in an Airline Reservation.
 It can be used in a college within a city.
 It can also be used for communication in the military.
 Uses/Applications Of Metropolitan Area Network:
 Examples of metropolitan area network (MAN):
• Digital cable television
• Used in government agencies
• University campuses
• Cable broadband
• Used to connect several branches of the local school
• In hospital (for communication between doctors, research offices, labs)
• A network of fire stations
• In airports
• Networking between community colleges within the country
• Used in public libraries

Advantages Of Metropolitan Area Network:
 Less expensive: It is less expensive to attach MAN with
WAN.
 Sending local emails
 High speed than WAN
 Sharing of the internet
 Conversion from LAN to MAN is easy
 High Security

disadvantages Of Metropolitan Area Network:
 Difficult to manage.
 Internet speed difference
 Hackers attack
 Technical people required to set up
 Conversion from LAN to MAN is easy
 More wires required

Disadvantages Of Metropolitan Area Network:
 Security issue: A WAN network has more security issues as
compared to LAN and MAN network as all the technologies are
combined together that creates the security problem.
 Needs Firewall & antivirus software: The data is transferred
on the internet which can be changed or hacked by the
hackers, so the firewall needs to be used. Some people can
inject the virus in our system so antivirus is needed to protect
from such a virus.
 High Setup cost: An installation cost of the WAN network is
high as it involves the purchasing of routers, switches.
 Troubleshooting problems: It covers a large area so fixing the
problem is difficult.

 WAN (Wide Area Network):
 A Wide Area Network is a network that extends over a large
geographical area such as states or countries.
 A Wide Area Network is quite bigger network than the LAN and MAN.
 A Wide Area Network is not limited to a single location, but it spans
over a large geographical area through a telephone line, fibre optic
cable or satellite links.
 wide area networks are a form of telecommunication networks that
can connect devices from multiple locations and across the globe.
 WANs are the largest and most expansive forms of computer
networks available to date.The internet is one of the biggest WAN in
the world.
 A Wide Area Network is widely used in the field of Business,
government, and education.
 These networks are often established by service providers that then
lease their WAN to businesses, schools, governments or the public.

 WAN(Wide Area Network):

 Internet
 US defense department
 Stock exchanges network
 Railway reservation system
 Big Banks' cash dispensers' network
 Satellite systems
 Uses/Applications Of Wide Area Network:
 Examples Of Wide Area Network:
• Mobile Broadband
• Private network
• Government network
• Last mile: A telecom company
• Internet Banking

Advantages Of Wide Area Network:
 Geographical area: A Wide Area Network provides a large
geographical area. Suppose if the branch of our office is in a
different city then we can connect with them through WAN.
The internet provides a leased line through which we can
connect with another branch.
 Centralized data: In case of WAN network, data is
centralized. Therefore, we do not need to buy the emails, files
or back up servers.
 Get updated files: Software companies work on the live
server. Therefore, the programmers get the updated files
within seconds.

Advantages Of Wide Area Network:
 Exchange messages: In a WAN network, messages are
transmitted fast. The web application like Facebook,
Whatsapp, Skype allows you to communicate with friends.
 Sharing of software and resources: In WAN network, we can
share the software and other resources like a hard drive,
RAM.
 Global business: We can do the business over the internet
globally.
 High bandwidth: If we use the leased lines for our company
then this gives the high bandwidth. The high bandwidth
increases the data transfer rate which in turn increases the
productivity of our company.

 Difference between LAN and WAN:
S.
NO
LAN WAN
1.
LAN stands for Local Area
Network.
Whereas WAN stands for Wide
Area Network.
2. LAN’s ownership is private.
But WAN’s ownership can be
private or public.
3.
The speed of LAN is high(more
than WAN).
While the speed of WAN is
slower than LAN.
4.
The propagation delay is short
in LAN.
Whereas the propagation delay
in WAN is long(longer than
LAN).
5.
There is less congestion in
LAN(local area network).
While there is more congestion
in WAN(Wide Area Network).

S.
NO
LAN WAN
6.
There is more fault tolerance in
LAN.
While there is less fault
tolerance in WAN.
7.
LAN’s design and maintenance
is easy.
While it’s design and
maintenance is difficult than
LAN.
8.
LAN covers small area i.e. within
the building.
While WAN covers large
geographical area.
9.
LAN operates on the principle of
broadcasting.
While WAN works on the
principle of point to point.
10.
Transmission medium used in
LAN is co-axial or UTP cable.
Whereas WAN uses PSTN or
satellite link as a transmission
or communication medium.
 Difference between LAN and WAN:

 Difference between LAN, MAN and WAN:
LAN MAN WAN
LAN stands for local
area network.
MAN stands for
metropolitan area
network.
WAN stands for wide
area network.
LAN’s ownership is
private.
MAN’s ownership can
be private or public.
While WAN also might
not be owned by one
organization.
The transmission
speed of a LAN is high.
While the transmission
speed of a MAN is
average.
Whereas the
transmission speed of
a WAN is low.
The propagation delay
is short in a LAN.
There is a moderate
propagation delay in a
MAN.
Whereas, there is a
long propagation delay
in a WAN.

 Difference between LAN, MAN and WAN:
LAN MAN WAN
There is less
congestion in LAN.
While there is more
congestion in MAN.
Whereas there is more
congestion than MAN
in WAN.
LAN’s design and
maintenance is easy.
While MAN’s design
and maintenance is
difficult than LAN.
Whereas WAN’s design
and maintenance is
also difficult than LAN
as well MAN.
There is more fault
tolerance in LAN.
While there is less fault
tolerance.
In WAN, there is also
less fault tolerance.

Fundamentals of Data Communication and Computer Networks

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Fundamentals of Data Communication and Computer Networks