PRIYADARSHINI POLYTECHNIC
DEPT OF COMPUTER TECHNOLOGY
BR/SEM: CM4I
SUBJECT:DATA COMMUNICATION AND COMPUTER NETWORK (22414)
UNIT 1 :FUNDAMENTALS OF DATA COMMUNICATION
AND COMPUTER NETWORK
INTRODUCTION
Data communications refers to the transmission of the digital data between two
or more computers and a computer network or data network is a
telecommunications network that allows computers to exchange data. The
physical connection between networked computing devices is established using
either cable media or wireless media. The best-known computer network is the
Internet.
Why to Learn Data Communication & Computer Network?
Network Basic Understanding
A system of interconnected computers and computerized peripherals such as
printers is called computer network. This interconnection among computers
facilitates information sharing among them. Computers may connect to each
other by either wired or wireless media.
Network Engineering
Networking engineering is a complicated task, which involves software, firmware,
chip level engineering, hardware, and electric pulses. To ease network
engineering, the whole networking concept is divided into multiple layers. Each
layer is involved in some particular task and is independent of all other layers.
But as a whole, almost all networking tasks depend on all of these layers. Layers
share data between them and they depend on each other only to take input and
send output.
Internet
A network of networks is called an internetwork, or simply the internet. It is the
largest network in existence on this planet.The internet hugely connects all
WANs and it can have connection to LANs and Home networks. Internet uses
TCP/IP protocol suite and uses IP as its addressing protocol. Present day,
Internet is widely implemented using IPv4. Because of shortage of address
spaces, it is gradually migrating from IPv4 to IPv6.
Internet enables its users to share and access enormous amount of information
worldwide. It uses WWW, FTP, email services, audio and video streaming etc. At
huge level, internet works on Client-Server model.
Internet uses very high speed backbone of fiber optics. To inter-connect various
continents, fibers are laid under sea known to us as submarine communication
cable.
Applications of Communication & Computer Network
Computer systems and peripherals are connected to form a network.They
provide numerous advantages:
● Resource sharing such as printers and storage devices
● Exchange of information by means of e-Mails and FTP
● Information sharing by using Web or Internet
● Interaction with other users using dynamic web pages
● IP phones
● Video conferences
● Parallel computing
● Instant messaging
DATA & INFORMATION
Data refers to the raw facts that are collected while information refers to
processed data that enables us to take decisions.
Ex. When result of a particular test is declared it contains data of all
students, when you find the marks you have scored you have the
information that lets you know whether you have passed or failed.
The word data refers to any information which is presented in a form
that is agreed and accepted upon by is creators and users.
1.3 DATA COMMUNICATION
Data Communication is a process of exchanging data or information
In case of computer networks this exchange is done between two
devices over a transmission medium.This process involves a
communication system which is made up of hardware and software.
The hardware part involves the sender and receiver devices and the
intermediate devices through which the data passes. The software part
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.
The following sections describes the fundamental characteristics that
are important for the effective working of data communication process
and is followed by the components that make up a data communications
system.
1.3.1 Characteristics of Data Communication
The effectiveness of any data communications system depends upon
the following four fundamental characteristics:
1.Delivery: The data should be delivered to the correct
destination and correct user.
2.Accuracy: 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.
1.3.2 Components of Data Communication
A Data Communication system has five components as shown in
the diagram below:
A Data Communication system has five components as shown in the
diagram below:Fig. Components of a Data Communication System
1. Message Message is the information to be communicated by
the sender to the receiver.
2. Sender The sender is any device that is capable of sending
the data (message).
3. Receiver The receiver is a device that the sender wants to
communicate the data (message).
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.
5. Protocol It is an agreed upon set or rules used by the sender and
receiver to communicate data.A protocol is a set of rules that governs
data communication. AProtocol 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.
Elements of a Protocol
There are three key elements of a protocol:
A.Syntax It means the structure or format of the data.
It is the arrangement of data 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.
C.Timing It tells the sender about the readiness of the receiver to
receive the dataIt 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.
1.7.1 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 Standards These are the standards that have been
traditionally used and mean by factor by convention oThese standards
are not approved by any organized body but are adopted by widespread
use.
2. De jure standard It means by law or by regulation.oThese
standards are legislated and approved by an body that is officially
recognized
Standard Organizations in field of Networking
Standards are created by standards creation committees, forums, and
government regulatory agencies.
Examples of Standard Creation Committees:
1. International Organization for Standardization(ISO)
2.International Telecommunications Union –Telecommunications
Standard (ITU-T)
3. American National Standards Institute (ANSI)
4. Institute of Electrical & Electronics Engineers (IEEE)
5. Electronic Industries Associates (EIA)
1.4 DATA REPRESENTATION Data is collection of raw facts which
is processed to deduce information.There may be different forms in
which data may be represented.Some of the forms of data used in
communications are as follows:
1. Text Text includes combination of alphabets in small case
as well as upper case. It is stored as a pattern of bits. Prevalent
encoding system : ASCII, Unicode
2. Numbers Numbers include combination of digits from 0 to 9. It
is stored as a pattern of bits. Prevalent encoding system : ASCII,
Unicode
3. Images― An image is worth a thousand words‖ is a very
famous saying. In computers images are digitally stored. A Pixel is the
smallest element of an image.
Commonly used Image formats : jpg, png, bmp, etc
4. Audio Data can also be in the form of sound which can be
recorded and broadcasted.
Example: What we hear on the radio is a source of data or
information.Audio data is continuous, not discrete.
5. Video Video refers to broadcasting of data in form of picture or
movie
1.5 DATA FLOW Two devices communicate with each other by sending and
receiving data. The data can flow between the two devices in the following
ways.
Mode of Communication
1. Simplex
2. Half Duplex
3. Full Duplex
1.5.1 Simplex
In Simplex, communication is unidirectionalOnly one of the devices
sends the data and the other one only receives the data.
DIAGRAM
Example: in the above diagram: a cpu send data while a monitor only receives
data.
.5.2 Half Duplex
In half duplex both the stations can transmit as well as receive but not at the
same time.When one device is sending other can only receive and vice-versa
(as shown in figure above.)
Example: A walkie-talkie.
DIAGRAM
Full Duplex n Full duplex mode, both stations can transmit and receive
at the same time.
Example: mobile phones
DIAGRAM
1.5 FUNDAMENTALS OF COMPUTER NETWORK
Defination: A computer network is a set of devices connected through links. A node can
be computer, printer, or any other device capable of sending or receiving the data.
A system of interconnected computers and computerized peripherals such as
printers is called computer network. This interconnection among computers
facilitates information sharing among them.
Computers may connect to each other by either wired or wireless media.
Generally, networks are distinguished based on their geographical span. A
network can be as small as distance between your mobile phone and its
Bluetooth headphone and as large as the internet itself, covering the whole
geographical world,
Classification of computer network
1.Classification of computer network BY THEIR GEOGRAPHY
2.Classification of computer network BY THEIR COMPONENT ROLE
1)Classification of computer network BY THEIR GEOGRAPHY AREA
A)Personal Area Network
A Personal Area Network (PAN) is smallest network which is very personal to a user. This may
include Bluetooth enabled devices or infra-red enabled devices. PAN has connectivity range up
to 10 meters. PAN may include wireless computer keyboard and mouse, Bluetooth enabled
headphones, wireless printers and TV remotes.
For example, Piconet is Bluetooth-enabled Personal Area Network which may contain up to 8
devices connected together in a master-slave fashion.
Local Area Network
A computer network spanned inside a building and operated under single administrative system
is generally termed as Local Area Network (LAN). Usually,LAN covers an organization’ offices,
schools, colleges or universities. Number of systems connected in LAN may vary from as least
as two to as much as 16 million.
LAN provides a useful way of sharing the resources between end users.The resources such as
printers, file servers, scanners, and internet are easily sharable among computers.
LANs are composed of inexpensive networking and routing equipment. It may contains local
servers serving file storage and other locally shared applications. It mostly operates on private
IP addresses and does not involve heavy routing. LAN works under its own local domain and
controlled centrally.
LAN uses either Ethernet or Token-ring technology. Ethernet is most widely employed LAN
technology and uses Star topology, while Token-ring is rarely seen.
LAN can be wired,wireless, or in both forms at once.
Metropolitan Area Network
The Metropolitan Area Network (MAN) generally expands throughout a city such as cable TV
network. It can be in the form of Ethernet,Token-ring, ATM, or Fiber Distributed Data Interface
(FDDI).
Metro Ethernet is a service which is provided by ISPs. This service enables its users to expand
their Local Area Networks. For example, MAN can help an organization to connect all of its
offices in a city.
Backbone of MAN is high-capacity and high-speed fiber optics. MAN works in between Local
Area Network and Wide Area Network. MAN provides uplink for LANs to WANs or internet.
Wide Area Network
As the name suggests,the Wide Area Network (WAN) covers a wide area which may span
across provinces and even a whole country. Generally, telecommunication networks are Wide
Area Network. These networks provide connectivity to MANs and LANs. Since they are
equipped with very high speed backbone, WANs use very expensive network equipment.
WAN may use advanced technologies such as Asynchronous Transfer Mode (ATM), Frame
Relay, and Synchronous Optical Network (SONET). WAN may be managed by multiple
administration.
NOTES IN PDF
LINK:http://archive.mu.ac.in/myweb_test/syllFybscit/dcn.pdf
2.Classification of computer network BY THEIR COMPONENT ROLE
Peer-To-Peer network
● 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.
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.
Client/Server Network
● 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.
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.
ANALOG SIGNAL AND DIGITAL SIGNAL
Analog and digital signals are the types of signals carrying information. The major difference
between both signals is that the analog signals that have continuous electrical signals, while digital
signals have non-continuous electrical signals. The difference between analog and digital signal can
be observed with the various examples of different types of waves.
Analog Signals
The analog signals were used in many systems to produce signals to carry information. These
signals are continuous in both values and time. The use of analog signals has been declined with the
arrival of digital signals. In short, to understand the analog signals – all signals that are natural or
come naturally are analog signals.
Digital Signals
Unlike analog signals, digital signals are not continuous, but signals are discrete in value and time.
These signals are represented by binary numbers and consist of different voltage values.
Difference Between Analog And Digital Signal
Analog Signals Digital Signals
Continuous signals Discrete signals
Represented by sine waves Represented by square waves
Human voice, natural sound, analog Computers, optical drives, and other
electronic devices are few examples electronic devices
Continuous range of values Discontinuous values
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.
BIT LENGTH or Bit Interval (Tb) It is the time required to send one bit. It is measured
in seconds.
BIT RATE 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
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 .
