CND_22634_UNIT1_MSBTE_Computer network and Data Communication

Computer Networking
and Data
Communication
Presented by
Prof. Pranoti R. Doke
Lecturer Electronics

Fundamentals of
Data
Communication
and Network
Topology
Unit 1

CONTENTS
 Introduction to data communication.
 Components of data communication
 Data flow:- Simplex, Half duplex, Full deplex
 Signals:- Analog and Digital signals.
 Transmission media:- Guided and Unguided media
 Networking devices

DATA COMMUNICATIONS
• The term telecommunication means communication at a distance. The
word data refers to information presented in whatever form is agreed
upon by the parties creating and using the data. Data communications
are the exchange of data between two devices via some form of
transmission medium such as a wire cable.
• Exchange of data between two devices via some forms of transmission
medium(such as wire cable) is Data Communications.
• For data communications to occur, the communicating devices must be
part of a communication system made of a combination of hardware
and software.
• The effectiveness of a data communication system depends on four
fundamental characteristics:- delivery, accuracy, timeliness and jitter.

Components of Data Communication
1. Sender
2. Receiver
3. Message
4. Tramsmission Medium
5. Protocol

Block diagram of Data communication System
1. Sender
2. Receiver
3. Message
4. Tramsmission Medium
5. Protocol

The five components of data communicationare:
1. Message - It is the information to be communicated. Popular forms of
information include text, pictures, audio, video etc.
2.Sender - It is the device which sends the data messages. It can
be a computer, workstation, telephone handset etc.
3.Receiver - It is the device which receives the data messages. It can be a
computer, workstation, telephone handset etc.
4.Transmission Medium - It is the physical path by which a message
travels from sender to receiver. Some examples include twisted-pair
wire, coaxial cable, radio waves etc.
5.Protocol - It is a set of rules that governs the data communications. It
represents an agreement between the communicating devices. Without a
protocol, two devices may be connected but not communicating.

Signals
 There are two types of signals to transfer data.
Signals
Analog signal Digital signal

Analog Signals
An analog signal are continuous and passes through or includes an
infinite number of continuous values along its path. The curve
representing the analog signal passes through an infinite number of
points.

Digital Signals:
A digital signal can have only a limited number of defined values.
Although each value can be any number,it is as simple as 1 and 0.

MODES OF DATA
TRANSFER IN
COMPUTER

DATA TRANSMISSION
Data transmission refers to the movement of
data in form of bits between two or more digital
devices.
This transfer of data takes place and some form
of transmission media.

DATA TRANSMISSION TYPES
1. Parallel
2. Serial
(i) Synchronous
(ii) Asynchronous

PARALLEL TRANSMISSION
 In parallel transmission, all the bits of data are
transmitted simultaneously on separate
communication lines.
 Parallel transmission is used for short distance
communication.
 In order to transmit n bit , n wires or lines are used.
 More costly.
 Faster than serial transmission.
 Data can be transmitted in less time.

SERIAL TRANSMISSION
In serial transmission , the various bits of data are
transmitted serially one after the other.
It requires only one communication line rather than n
lines to transmit data from sender to receiver.
Thus all the bits of data are transmitted
on single lines in serial fashion.
Less costly.
Long distance transmission.

SYNCHRONOUS
TRANSMISSION
 Data sent at one time multiple bytes.
 Start and stop bit not used.
 Gap between data units not present.
 Data transmission speed fast.
 Cost high.
 Transfer of data between two computer.
 Synchronization between sender and
receiver required.

ASYNCHORONOUS
TRANSMISSION
 Sends only one character at a time (one byte
of data at a time)
 Synchronize two devices using Start Bit and Stop
Bit.
 Start bit refers to the start of the data.
Usually 0 is used for start bit.
 Stop bit indicates the end of data.more than one
bit can be used for end.

TRANSMISSION MODE
 The term transmission mode defines the
direction of the flow of information between
two communication devices i .e
 It tells the direction of signal flow between the
two devices.

TYPES OF TRANSMISSION
MODE
1. Simplex Transmission Mode.
2. Half Duplex Transmission Mode
3. Full Duplex Transmission Mode.

Figure 1.2 Data flow (simplex, half-duplex, and full-duplex)

Data flow can occur in three ways:
1. Simplex: In simplex mode,the communication is unidirectional.only one
of the devices on a link can transmit, the other can only receive. e.g.
keyboards,monitors,etc.
2. Half-duplex: In this mode,each station can both transmit and receive,but
not at the same time.When one device is sending,the other can only
receive,and vice-versa. e.g. walkie-talkies,CB(citizens band) etc.
3. Full Duplex: In full duplex mode, both stations can transmit and receive
simultaneously. One common example of full duplex is the Telephone
network. When two people are communicating by a telephone line, both
can talk and listen at the same time. The full-duplex mode is used when
communication in both directions is required all the time.

SIMPLEX MODE
In simplex mode transmission information
sent in only one direction.
Device connected in simplex mode is either
sent only or received only that is one device
can only send, other device can only
receive.
Communication is unidirectional.

HALF DUPLEX
In half duplex transmission data can be
sent in both the directions, but only in one
direction at a time.
Both the connected device can transmit and
receive but not simultaneously.
When one device is sending the other can
only receive and vice-versa.

FULL DUPLEX
In full duplex transmission, data can be sent in both
the directions simultaneously.
Both the connected devices can transmit and
receive at the same time.
Therefore it represents truly bi-directional system.
In full duplex mode, signals going in either
Direction share the full capacity of link.

Bit rate N, is the number of bits per second (bps).
Baud rate is the number of signal elements per second
(bauds).
In the analog transmission of digital data, the signal or baud
rate is less than or equal to the bit rate.
S=Nx1/r bauds
Where r is the number of data bits per signal element.
Transmission Characteristics

• Data Rate is defined as the amount of data transmitted during a
specified time period over a network. It is the speed at
which data is transferred from one device to another or between a
peripheral device and the computer. It is generally measured in
Mega bits per second(Mbps) or (MBps)
• Signaling rate (SR), also known as gross bit rate, is the
aggregate rate at which data pass a point in the transmission path
of a data transmission system
Transmission Characteristics

An analog signal carries 4 bits per signal element. If 1000
signal elements are sent per second, find the bit rate.
Solution
In this case, r = 4, S = 1000, and N is unknown. We can find the
value of N from
Example: 1

An analog signal has a bit rate of 8000 bps and a baud rate of
1000 baud. How many data elements are carried by each
signal element? How many signal elements do we need?
Solution
In this example, S = 1000, N = 8000, and r and L are unknown.
We find first the value of r and then the value of L.
Example: 2

ADVANTAGES OF NETWORKING
• Connectivity andCommunication
• Data Sharing
• Hardware Sharing
• InternetAccess
• InternetAccessSharing
• Data Security andManagement
• Entertainment

THE DISADVANTAGES OF
NETWORKING
• Network Hardware, Software and Setup Costs
• Hardware and Software Management and
Administration Costs
• Undesirable Sharing
• Illegal or Undesirable Behavior
• Data Security Concerns

NETWORK CRITERIA
A network must be able to meet certain criteria, these are mentioned below:
Performance Reliability Scalability
Performance :
It can be measured in following ways : Transit time : It is the time taken
to travel a message from one device to another.
Response time : It is defined as the time elapsed between enquiry and
response.
Efficiency of software Number of users
Capability of connected hardware

NETWORK CRITERIA
Reliability
• It decides the frequency at which network failure take place.
More the failures are, less is the network's reliability.
Security
• It refers to the protection of data unauthorized user or access.
While through network, data passes many network, and data
can be traced if attempted. Hence security is also a very
important characteristic for Networks.

Five components of data communication

Types of connections: point-to-point and multipoint

Based on Transmission Technology
• Broadcast Networks: All stations share a single communication channel
• Point-to-Point Networks: Pairs of hosts (or routers) are directly connected
• Typically, local area networks (LANs) are broadcast and wide area networks (WANs)
are point-to-point
Broadcast Network Point-to-Point Network

Links
(a)
(b)
point-to-point
multiple-access
Geographical coverage and scalability are limited.
Each node needs one interface for each link.
5

Broadcast Networks
• A Single communication link is shared by all the machines on that network
• When a message is transmitted, it can be received &
processed by every machine on that network. This is called broadcasting
• The address field within the message specifies the intended recipient. Only if
its for the host, it process the message or it ignores it.
• Two popular topologies of broadcast LAN are Bus and Ring
6

A variant of broadcasting called multicasting in which transmission is
done to a subset of machines.
Advantages
• Network is easy to build- Only one cable is needed
• Cost of construction is cheaper when compared to other
networks
Disadvantages
• Not very scalable and flexible
• An Arbitration mechanism is needed to resolve conflicts
Broadcast Networks
7

Point-to-Point Networks
• Consists of many connections between individual pair of nodes.
• Often multiple routes of different lengths are possible
• Point-to-point transmission with one sender and one receiver is sometimes
called unicasting
• End devices that wish to communicate are called stations and the switching
devices are called nodes.

Advantages
• Greater aggregate bandwidth- can have more than one sender
• Can add capacity incrementally- add more links/switches
• Better fault tolerance
• Lower Latency- No arbitration needed to send
Disadvantages
• More expensive as it requires lots of transmission lines and switching
elements to connect remote hosts
Point-to-Point Networks
4
1

Networks Based on Scale
Classification
of network
LocalArea
Network
(LAN)
Metropolitan
Area Network
(MAN)
WideArea
Network
(WAN)
The main differentiation among these classifications is their area
of coverage.
LAN, MAN and WAN compared
12

LOCAL AREA NETWORK {LAN}
A LAN is a private network that connects computers and devices in a limited
geographically area such as a home, school computer laboratory, office building.
LAN’s are used to share resources and to exchange information.
LAN’s are restricted in size having a bounded worst-case transmission time, which
simplifies networks management
Traditional LAN’s run
at 10-100Mbps
Common Topologies
used are bus, ring and
star
High data rates with

Headphone
PDA
Printer
Mouse
Laptop
Smartphone
LOCAL AREA NETWORK {LAN}
Types
of
LAN
PersonalArea
Network
(PAN)
HouseArea
Network
(HAN)
A Personal area network (PAN) is a computer network used for communication
among computer and different information technological devices close to one
person. Common Technologies used are Bluetooth and Infrared. Range is ~10m
A House area network (HAN) is a type of local area network that develops from
the need to facilitate communication and interoperability among digital devices
present inside or within the close vicinity of a home.
14

Covers a larger geographical area than is a LAN, ranging from
several blocks of buildings to entire cities.
It may be a single network as a cable TV network or it may be means
of connecting a number of LANs into a larger network so that
resources may be shared.
MAN is wholly owned and operated by a private company or may be
a service provided by a public company
A metropolitan area network based on cable TV
METROPOLITAN AREA NETWORK {MAN}
15

The main reason for distinguishing MANs as a special category is
that a standard has been adopted for them. It is DQDB
(Distributed Queue Dual Bus) or IEEE 802.6.
METROPOLITAN AREA NETWORK {MAN}
Using DQDB, networks can be up to 20 miles (30 km) long and operate at speeds of 34
to 155 Mbits/s.
It consists of two unidirectional buses (cables) to which all the computers are
connected. Each bus has a head-end, which initiates transmission activity. Traffic destined
for a computer to the right of the sender uses the upper bus
16and to the left uses the lower one.

Wide area networks are the oldest type of data communications
network that provide relatively slow-speed, long-distance transmission
of data, voice and video information over relatively large and widely
dispersed geographical areas, such as country or entire continent.
WAN spans a large geographical area: a country or a continent
It contains a collection of machines intended for running user
programs called hosts. The hosts are connected by a communication
subnet, or just subnet for short.
In most WAN’s, the subnet consists of two distinct components:
transmission lines and switching elements. Transmission lines move
bits between machines. Switching elements (Routers) are specialized
computers that connect three or more transmission lines. When data
arrive on an incoming line, the switching element must choose an
outgoing line on which to forward them.
WIDE AREA NETWORK {WAN}
47

WIDE AREA NETWORK {WAN}
When a packet is sent from one router to another via one or more intermediate
routers, the packet is received at each intermediate router in its entirety, stored there
until the required output line is free, and then forwarded. A subnet organized
according to this principle is called a store-and-forward or packet-switched
subnet. Routing decisions are made locally according to a routing
algorithm.
48

Internetwork {Internet}
It is a Global network of computers which may be server or client that exchanges information.
It can be defined as a "network of networks" which can be linked
through copper wires, wireless connections, and other technologies.
This is the world-wide network of computers accessible to anyone who knows their Internet
Protocol (IP) address
Such interconnection of networks requires that different, and frequently incompatible networks,
be connected, sometimes by means of machines called gateways to make the connection and
provide the necessary translation, both in terms of hardware and software.

TransmissionMedia
• The means through which data is transformed from one place to
another is called transmission or communication media. There are two
categories of transmission media used in computer communications.
• Electromagnetic radiation can be transmitted through an optical media,
such as optical fiber, or through twisted pair wires, coaxial cable, or
dielectric-slab waveguides.
• It may also pass through any physical material that is transparent to
the specificwavelength, such as water, air, glass, or concrete.
• Sound is, by definition, the vibration of matter, so it requires a physical
medium for transmission, as does other kinds of mechanical waves
• and heat energy.

Typesof TransmissionMedia
Transmission Media
Guided Media Unguided Media

Guided Media
 Guided media are the physical links through which signals are confined to
narrow path. These are also called guide media. Bounded media are made
up o a external conductor (Usually Copper) bounded by jacket material.
Bounded media are great for LABS because they offer high speed, good
security and low cast. However, some time they cannot be used due
distance communication. Three common types of bounded media are used
of the data transmission. These are
 Coaxial Cable
 Twisted Pairs Cable
 Fiber Optics Cable

Coaxial cable
 Coaxial cable is very common & widely used commutation media. For
example TV wire is usually coaxial. Coaxial cable gets its name because
it contains two conductors that are parallel to each other. The center
conductor in the cable is usually copper. The copper can be either a solid
wire or stranded martial.
 Outside this central Conductor is a non-conductive material. It is
usually white, plastic material used to separate the inner Conductor
form the outer Conductor. The other Conductor is a fine mesh made
from Copper.

Fiber opticcable
 Fiber optic cable uses electrical signals to transmit
data. It uses light. In fiber optic cable light only
moves in one direction for two way communication
to take place a second connection must be made
between the two devices. It is actually two stands of
cable. Each stand is responsible for one direction of
communication. A laser at one device sends pulse of
light through this cable to other device. These pulses
translated into “1’s” and “0’s” at the other end.
 In the center of fiber cable is a glass stand or core.
The light from the laser moves through this glass to
the other device around the internal core is a
reflective material known asCLADDING. No light
escapes the glass core because of this reflective
cladding.

Twisted Pair Cable
 The most popular network cabling is Twisted pair. It is light weight, easy
to install, inexpensive and support many different types of network. It
also supports the speed of 100 mps.Twisted pair cabling is made of pairs
of solid or stranded copper twisted along each other. The twists are done
to reduce vulnerably to EMI and cross talk. The number of pairs in the
cable depends on the type. The copper core is usually 22- AWG or 24-
AWG, asmeasured on the American wire gauge standard. There are two
types of twisted pairs cabling
 1. Unshielded twisted pair (UTP)
 2. Shielded twisted pair (STP)

Unshielded twisted pair (UTP)
UTP is more common. It can be either voice grade
or data grade depending on the condition. UTP
cable normally has an impedance of 100 ohm.
UTP cost less than STP and easily available due to
its many use. There are five levels of data cabling
.

Shielded twisted pair (STP)
 It is similar to UTP but has a mesh
shielding that’s protects it from EMI
which allows for higher transmission
rate.

UnguidedMedia
• Unguided media or wireless media doesn't use any physical connectors
between the two devices communicating. Usually the transmission is
send through the atmosphere but, sometime it can be just across the
rule. Wireless media is used when a physical obstruction or distance
blocks are used with normal cable media. The three types of wireless
media are:
 Radio waves
 Micro waves
 Infrared waves

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