Data

Communication – What is Data

Communication?
Data communication refers to the exchange of data between a source
and a receiver via form of transmission media such as a wire cable.
Data communications to occur, the communicating devices must be part
of a communication system made up of a combination of hardware
(physical equipment) and software (programs).

Components of data communication system:-

1. Sender: It is the device/computer that generates and sends that
message.
2. Message: It is the information or data to be communicated. It can
consist of text, numbers, pictures, sound or video or any
combination of these.
3. Medium: It is the channel or physical path through which the
message is carried from sender to the receiver. The medium can be
wired like twisted pair wire,
 coaxial cable, fiber-optic cable or wireless like laser, radio
waves, and microwaves.
4. Protocol: It is a set of rules that govern the communication
between the devices. Both sender and receiver follow same
protocols to communicate with each other.
5. Receiver: It is the device or computer that receives the message.
The location of receiver computer is generally different from the
sender computer.
6. The distance between sender and receiver depends upon the types
of network used in between.

What Is a Computer Network?

A computer network is defined as a system that connects two or more
computing devices for transmitting and sharing information
The advantages of computer network are
 Allows sharing of data, programs and software. processing is also
cheaper.
 Better Communication facilities.
 allows sharing of hardware components and saves money for
buying extra devices
The disadvantages of computer network are
 Problems of software privacy.
 Initial expensive setups.
 Cybercrimes are originated.
 It depends on the server.

Computer Network Types

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.
A computer network can be categorized by their size. A computer
network is mainly of four types:

LAN(Local Area Network)

o Local Area Network is a group of computers connected to each

other in a small area such as building, office.
o LAN is used for connecting two or more personal computers
through a communication medium such as twisted pair, coaxial
cable, etc.
o It is less costly as it is built with inexpensive hardware such as
hubs, network adapters, and ethernet cables.
o The data is transferred at an extremely faster rate in Local Area
Network.
o Local Area Network provides higher security.
MAN(Metropolitan Area Network)
o A metropolitan area network is a network that covers a larger
geographic area by interconnecting a different LAN to form a
larger network.
o Government agencies use MAN to connect to the citizens and
private industries.
o In MAN, various LANs are connected to each other through a
telephone exchange line.
o It has a higher range than Local Area Network(LAN)

Uses Of Metropolitan Area Network:

o MAN is used in communication between the banks in a city.
o It can be used in an Airline Reservation.
o It can be used in a college within a city.
o It can also be used for communication in the military.

WAN(Wide Area Network)

o A Wide Area Network is a network that extends over a large
geographical area such as states or countries.
o A Wide Area Network is quite bigger network than the LAN.
 o 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.
o The internet is one of the biggest WAN in the world.
o A Wide Area Network is widely used in the field of Business,
government, and education.

Examples Of Wide Area Network:

o Mobile Broadband: A 4G network is widely used across a region
or country.
o Last mile: A telecom company is used to provide the internet
services to the customers in hundreds of cities by connecting their
home with fiber.
 o Private network: A bank provides a private network that connects
the 44 offices. This network is made by using the telephone leased
line provided by the telecom company.
o

What is the data transmission mode?

A data transmission mode describes how two devices in a network
communicate or exchange data. It specifics the direction in which
signals travel over the media and the number of signals that can traverse
the media at any given time.
Simplex
Simplex is also called one-way or unidirectional. It allows
communication in one direction only. Since signals travel in only one
direction, the sender device uses the entire communication channel or all
available bandwidth. The receiver device only receives signals. The
receiver can't reply to the sender by using the same communication
channel. TV remotes, garage door openers, and smart speakers are some
examples of Simplex.
Half-duplex
Half-duplex allows communication in both directions but not at the same
time. Signals travel in both directions over a medium but in one
direction only at a time. Since signals travel in only one direction, a
device can either send or receive data at a given time. A network card set
to Half-duplex cannot receive data when it is sending data. To receive
data, it needs to change the direction of data flow.
Railway tracks and walkie-talkies are examples of half-duplex.
Full-duplex
Full-duplex is also called two-way or bidirectional. It allows
communication in both directions simultaneously. It divides the
available channel into two parts and uses one part to send data and the
other part to receive data. Since there is a separate path for sending and
receiving data, a device can simultaneously perform both tasks at a
given time.
A two-lane highway is an example of a full-duplex. A two-lane highway
uses dedicated lanes for incoming and outgoing traffic.

What is Transmission media?

Transmission media is a communication channel that carries the
information from the sender to the receiver. Data is transmitted
through the electromagnetic signals.
The main functionality of the transmission media is to carry the
information in the form of bits through LAN(Local Area Network).
It is a physical path between
 transmitter and receiver in data communication. Transmission
media is of two types are wired media and wireless media. In
wired media, medium characteristics
are more important whereas, in wireless media, signal
characteristics are more important.
These transmission media may be of two types –
Guided − In guided media, transmitted data travels through
cabling system that has a fixed path. For example, copper wires,
fibre optic wires, etc.
Unguided − In unguided media, transmitted data travels through
free space in form of electromagnetic signal. For example, radio
waves, lasers, etc.

Guided −:-
Twisted Pair Cable
Copper wires are the most common wires used for transmitting
signals because of good performance at low costs. They are most
commonly used in telephone lines.
Such twisted copper wires are called twisted pair. To reduce
interference between nearby twisted pairs, the twist rates are
different for each pair. Up to 25 twisted
pair are put together in a protective covering to form twisted pair
cables that are the backbone of telephone systems and Ethernet
networks.
STP AND UTP …covered the topic in book…

Advantages of twisted pair cable

 Trained personnel easily available due to shallow learning curve
 Can be used for both analog and digital transmissions
 Least expensive for short distances
 Entire network does not go down if a part of network is damaged
Disadvantages of twisted pair cable
Signal cannot travel long distances without repeaters
High error rate for distances greater than 100m
Very thin and hence breaks easily
Not suitable for broadband connections

Coaxial Cable
Coaxial cables are copper cables with better shielding than twisted pair
cables, so that transmitted signals may travel longer distances at higher
speeds. A coaxial cable
consists of these layers, starting from the innermost −
Stiff copper wire as core
Insulating material surrounding the core
Closely woven braided mesh of conducting material surrounding
the insulator
Protective plastic sheath encasing the wire
Coaxial cables are widely used for cable TV connections and LANs.

Advantages of Coaxial Cables

These are the advantages of coaxial cables −
 Excellent noise immunity
 Signals can travel longer distances at higher speeds, e.g. 1 to 2
Gbps for 1 Km cable
 Can be used for both analog and digital signals
 Inexpensive as compared to fibre optic cables
 Easy to install and maintain

Disadvantages of Coaxial Cables
These are some of the disadvantages of coaxial cables −
 Expensive as compared to twisted pair cables
 Not compatible with twisted pair cables
Optical Fiber
Thin glass or plastic threads used to transmit data using light waves are
called optical fibre. Light Emitting Diodes (LEDs) or Laser Diodes
(LDs) emit light waves at the source,
which is read by a detector at the other end. Optical fiber cable has a
bundle of such threads or fibres bundled together in a protective
covering. Each fiber is made up of
these three layers, starting with the innermost layer –

 Core made of high quality silica glass or plastic

 Cladding made of high quality silica glass or plastic, with a lower
refractive index than the core
 Protective outer covering called buffer

Advantages of Optical Fiber
Optical fiber is fast replacing copper wires because of these advantages
that it offers −
 High bandwidth
 Immune to electromagnetic interference
 Suitable for industrial and noisy areas
 Signals carrying data can travel long distances without weakening
Disadvantages of Optical Fiber
Despite long segment lengths and high bandwidth, using optical fiber
may not be a viable option for every one due to these disadvantages −
 Optical fiber cables are expensive
 Sophisticated technology required for manufacturing, installing and
maintaining optical fiber cables
 Light waves are unidirectional, so two frequencies are required for
full duplex transmission

Unguided
Infrared
 Low frequency infrared waves are used for very short distance
communication like TV remote, wireless speakers, automatic
doors, hand held devices etc.
Infrared signals can propagate within a room but cannot penetrate
walls. However, due to such short range, it is considered to be one
of the most secure transmission modes.

Radio Wave
Radio waves are the electromagnetic waves that are transmitted in
all the directions of free space. Radio waves are omnidirectional,
i.e.,
the signals are propagated in all the directions. The range in
frequencies of radio waves is from 3Khz to 1 khz .In the case of
radio waves,
the sending and receiving antenna are not aligned, i.e., the wave
sent by the sending antenna can be received by any receiving
antenna.
An example of the radio wave is FM radio
.

Advantages of Radio Wave

These are some of the advantages of radio wave transmissions −
 Inexpensive mode of information exchange
 No land needs to be acquired for laying cables
 Installation and maintenance of devices is cheap

Disadvantages of Radio Wave
These are some of the disadvantages of radio wave transmissions −
 Insecure communication medium
 Prone to weather changes like rain, thunderstorms, etc.
Microwaves
o Microwaves are the electromagnetic waves having the frequency in
the range from 1GHz to 1000 GHz.
o Microwaves are unidirectional as the sending and receiving
antenna is to be aligned, i.e., the waves sent by the sending antenna
are narrowly focussed.
o In this case, antennas are mounted on the towers to send a beam to
another antenna which is km away.
o It works on the line of sight transmission, i.e., the antennas
mounted on the towers are the direct sight of each other.
Characteristics of Microwave:
o Frequency range: The frequency range of terrestrial microwave is
from 4-6 GHz to 21-23 GHz.
o Bandwidth: It supports the bandwidth from 1 to 10 Mbps.

o Short distance: It is inexpensive for short distance.

o Long distance: It is expensive as it requires a higher tower for a

longer distance.
o Attenuation: Attenuation means loss of signal. It is affected by
environmental conditions and antenna size
Advantages Of Microwave:
o Microwave transmission is cheaper than using cables.

o It is free from land acquisition as it does not require any land for
the installation of cables.
Disadvantages of Microwave transmission:
o Eavesdropping: An eavesdropping creates insecure
communication. Any malicious user can catch the signal in the air
by using its own antenna.
o Out of phase signal: A signal can be moved out of phase by using
microwave transmission.
What is network topology explain?
A network topology is the physical and logical arrangement of nodes
and connections in a network. Nodes usually include devices such as
switches, routers and software with switch and router features. Network
topologies are often represented as a graph
Bus Topology

bus topology there is a main cable and all the devices are connected to
this main cable through drop lines. There is a device called tap that
connects the drop line to the main cable.
Since all the data is transmitted over the main cable, there is a limit of
drop lines and the distance a main cable can have
Advantages of bus topology

1. Easy installation, each cable needs to be connected with backbone

cable.
2. Less cables required than Mesh and star topology

Disadvantages of bus topology

1. Difficultly
in fault detection.
2. Not scalable as there is a limit of how many nodes you can connect
with backbone cable.
Ring Topology

In ring topology each device is connected with the two devices on either
side of it. There are two dedicated point to point links a device has with
the
devices on the either side of it. This structure forms a ring thus it is
known as ring topology. If a device wants to send data to another device
then
it sends the data in one direction, each device in ring topology has a
repeater, if the received data is intended for other device then repeater
forwards
this data until the intended device receives it.
Advantages of Ring Topology

1. Easy to install.
2. Managing is easier as to add or remove a device from the topology
only two links are required to be changed.

Disadvantages of Ring Topology

1. A link failure can fail the entire network as the signal will not travel
forward due to failure.
2. Data traffic issues, since all the data is circulating in a ring.

Star Topology

In star topology each device in the network is connected to a central

device called hub. Unlike Mesh topology, star topology doesn’t allow
direct communication
between devices, a device must have to communicate through hub. If
one device wants to send data to other device, it has to first send the data
to hub and then
the hub transmit that data to the designated device.

Advantages of Star topology

1. Less expensive because each device only need one I/O port and needs
to be connected with hub with one link.
2. Easier to install
3. Less amount of cables required because each device needs to be
connected with the hub only.
4. Robust, if one link fails, other links will work just fine.
5. Easy fault detection because the link can be easily identified.

Disadvantages of Star topology

1. If hub goes down everything goes down, none of the devices can work
without hub.
2. Hub requires more resources and regular maintenance because it is the
central system of star topology.
Mesh Topology

In mesh topology each device is connected to every other device on the

network through a dedicated point-to-point link. When we say dedicated
it means that the link only carries data for the two connected devices only.

Advantages of Mesh topology

No data traffic issues as there is a dedicated link between two devices

which means the link is only available for those two devices.
Mesh topology is secure because there is a point to point link thus
unauthorized access is not possible.
Fault detection is easy.
Disadvantages of Mesh topology

Amount of wires required to connected each system is tedious and

headache.
 Each device needs to be connected with other devices, number of I/O
ports required must be huge.
o