UNIT 3
Internet
• Internet refers to network of networks.
• Internet is a world-wide global system of interconnected computer networks.
• Internet uses the standard Internet Protocol (TCP/IP).
• Every computer in internet is identified by a unique IP address.
• IP Address is a unique set of numbers (such as 110.22.33.114) which identifies a
computer location.
• A special computer DNS (Domain Name Server) is used to give name to the IP
Address so that user can locate a computer by a name.
• For example, a DNS server will resolve a name http://www.tutorialspoint.com to a
particular IP address to uniquely identify the computer on which this website is
hosted.
• Internet is accessible to every user all over the world.
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 of network architectures are used:
o Peer-To-Peer network
o Client/Server network
Peer-To-Peer network
o Peer-To-Peer network is a network in which all the computers are linked together
with equal privilege and responsibilities for processing the data.
o Peer-To-Peer network is useful for small environments, usually up to 10 computers.
o Peer-To-Peer network has no dedicated server.
o 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.
Client/Server Network
o 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.
o The central controller is known as a server while all other computers in the network
are called clients.
o A server performs all the major operations such as security and network management.
o A server is responsible for managing all the resources such as files, directories,
printer, etc.
o 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.
What is World Wide Web?
➢ World Wide Web, which is also known as a Web, is a collection of websites or web
pages stored in web servers and connected to local computers through the internet.
➢ These websites contain text pages, digital images, audios, videos, etc.
➢ Users can access the content of these sites from any part of the world over the internet
using their devices such as computers, laptops, cell phones, etc.
➢ The WWW, along with internet, enables the retrieval and display of text and media to
your device.
➢ The building blocks of the Web are web pages which are formatted in HTML and
connected by links called "hypertext" or hyperlinks and accessed by HTTP.
➢ These links are electronic connections that link related pieces of information so that
users can access the desired information quickly.
➢ Hypertext offers the advantage to select a word or phrase from text and thus to access
other pages that provide additional information related to that word or phrase.
FTP
o FTP stands for File transfer protocol.
o FTP is a standard internet protocol provided by TCP/IP used for transmitting the files
from one host to another.
o It is mainly used for transferring the web page files from their creator to the computer
that acts as a server for other computers on the internet.
o It is also used for downloading the files to computer from other servers.
Objectives of FTP
o It provides the sharing of files.
o It is used to encourage the use of remote computers.
o It transfers the data more reliably and efficiently.
Why FTP?
o Although transferring files from one system to another is very simple and
straightforward, but sometimes it can cause problems.
o For example, two systems may have different file conventions. Two systems may
have different ways to represent text and data.
o Two systems may have different directory structures. FTP protocol overcomes these
problems by establishing two connections between hosts.
o One connection is used for data transfer, and another connection is used for the
control connection.
Mechanism of FTP
o The above figure shows the basic model of the FTP.
o The FTP client has three components: the user interface, control process, and data
transfer process.
o The server has two components: the server control process and the server data transfer
process.
There are two types of connections in FTP:
o Control Connection: The control connection uses very simple rules for
communication. Through control connection, we can transfer a line of command or
line of response at a time. The control connection is made between the control
processes. The control connection remains connected during the entire interactive
FTP session.
o Data Connection: The Data Connection uses very complex rules as data types may
vary. The data connection is made between data transfer processes. The data
connection opens when a command comes for transferring the files and closes when
the file is transferred.
Advantages of FTP:
o Speed: One of the biggest advantages of FTP is speed. The FTP is one of the fastest
way to transfer the files from one computer to another computer.
o Efficient: It is more efficient as we do not need to complete all the operations to get
the entire file.
o Security: To access the FTP server, we need to login with the username and
password. Therefore, we can say that FTP is more secure.
o Back & forth movement: FTP allows us to transfer the files back and forth. Suppose
you are a manager of the company, you send some information to all the employees,
and they all send information back on the same server.
Disadvantages of FTP:
o The standard requirement of the industry is that all the FTP transmissions should be
encrypted. However, not all the FTP providers are equal and not all the providers
offer encryption. So, we will have to look out for the FTP providers that provides
encryption.
o FTP serves two operations, i.e., to send and receive large files on a network.
However, the size limit of the file is 2GB that can be sent. It also doesn't allow you to
run simultaneous transfers to multiple receivers.
o Passwords and file contents are sent in clear text that allows unwanted eavesdropping.
So, it is quite possible that attackers can carry out the brute force attack by trying to
guess the FTP password.
o It is not compatible with every system.
TELNET
➢ TELNET stands for TErminaL NETwork. It is a type of protocol that enables one
computer to connect to local computer.
➢ It is a used as a standard TCP/IP protocol for virtual terminal service which is
given by ISO. Computer which starts connection known as the local computer.
➢ Computer which is being connected to i.e. which accepts the connection known
as remote computer. When the connection is established between local and remote
computer.
➢ During telnet operation whatever that is being performed on the remote computer
will be displayed by local computer. Telnet operates on client/server principle.
Local computer uses telnet client program and the remote computers uses telnet
server program.
➢ Following are some basic differences between both TELNET and FTP.
Sr. Key TELNET FTP
No.
Definition TELNET is an abbreviation On other hand FTP
Telecommunication Network and is stands for File Transfer
simply a connection protocol that Protocol and its
allows a user to connect to a remote primarily concern is to
server that is listening for facilitate the transfer of
1 commands. Once the connection is files from one point to
established, the user can then issue another, along with a
commands to the server computer, few management
and examine the responses that are capabilities like making
sent back. and deleting directories.
Port In general TELNET uses 23 port for While in case of FTP
Number its command operations. port numbers 20 and 21
2 Used can be used to establish
connection and perform
file transfer operations.
Number of Due to single operated port TELNET On other hand as FTP
connections can establish only one connection. has two ports available
so FTP establish two
3 connections, one is for
control command and
another is for data
transfer.
Sr. Key TELNET FTP
No.
Remote In case of TELNET remote login is On other hand remote
4 Login mandatory as issue commands could login is not mandatory
be run only after login. in case of FTP.
Search Engines
➢ A search engine is an online answering machine, which is used to search,
understand, and organize content's result in its database based on the search query
(keywords) inserted by the end-users (internet user).
➢ To display search results, all search engines first find the valuable result from their
database, sort them to make an ordered list based on the search algorithm, and display
in front of end-users.
➢ The process of organizing content in the form of a list is commonly known as
a Search Engine Results Page (SERP).
Google, Yahoo!, Bing, YouTube, and DuckDuckGo are some popular examples of search
engines.
Web Browser
A web browser, or simply "browser," is an application used to access and view websites.
Common web browsers include Microsoft Internet Explorer, Google Chrome, Mozilla
Firefox, and Apple Safari.
Web Browser Definition: A software application used to access information on the World
Wide Web is called a Web Browser. When a user requests some information, the web
browser fetches the data from a web server and then displays the webpage on the user’s
screen.
• The main function is to retrieve information from the World Wide Web and making it
available for users.
E-Mail
o E-mail is defined as the transmission of messages on the Internet. Electronic
Mail (e-mail) is one of most widely used services of Internet.
o This service allows an Internet user to send a message in formatted manner
(mail) to the other Internet user in any part of world.
o Message in mail not only contain text, but it also contains images, audio and videos
data.
o The person who is sending mail is called sender and person who receives mail is
called recipient. It is just like postal mail service.
o It is one of the most commonly used features over communications networks that may
contain text, files, images, or other attachments. Generally, it is information that is
stored on a computer sent through a network to a specified individual or group of
individuals.
o Email messages are conveyed through email servers; it uses multiple protocols within
the suite.
o For example, SMTP is a protocol stands for simple mail transfer protocol and used to
send messages whereas other protocols IMAP or POP are used to retrieve messages
from a mail server. If you want to login to your mail account, you just need to enter a
valid email address, password, and the mail servers used to send and receive
messages.
Components of E-Mail System :
E-mail message comprises of different components: E-mail Header, Greeting, Text, and
Signature. These components are described in the following diagram:
Advantages of E-Mail
1. Reliable
Many of the mail systems notify the sender if e-mail message was undeliverable.
2. Convenience
There is no requirement of stationary and stamps. One does not have to go to post office.
But all these things are not required for sending or receiving an mail.
3. Speed
E-mail is very fast. However, the speed also depends upon the underlying network.
4. Inexpensive
The cost of sending e-mail is very low.
5. Printable
It is easy to obtain a hardcopy of an e-mail. Also an electronic copy of an e-mail can also be
saved for records.
6. Global
E-mail can be sent and received by a person sitting across the globe.
7. Generality
It is also possible to send graphics, programs and sounds with an e-mail.
Disadvantages of E-Mail
Apart from several benefits of E-mail, there also exists some disadvantages as discussed
below:
• Forgery
• Overload
• Misdirection
• Junk
• No response
1. Forgery
E-mail doesn’t prevent from forgery, that is, someone impersonating the sender, since
sender is usually not authenticated in any way.
2. Overload
Convenience of E-mail may result in a flood of mail.
3. Misdirection
It is possible that you may send e-mail to an unintended recipient.
4. Junk
Junk emails are undesirable and inappropriate emails. Junk emails are sometimes referred to
as spam.
IoT (Internet of Things)
o Connecting everyday things embedded with electronics, software, and sensors to
internet enabling to collect and exchange data without human interaction called as the
Internet of Things (IoT).
o The term "Things" in the Internet of Things refers to anything and everything in day
to day life which is accessed or connected through the internet.
What is a Sensor?
o A sensor is defined as a device or a module that helps to detect any changes in
physical quantity like pressure, force or electrical quantity like current or any
other form of energy.
o After observing the changes, sensor sends the detected input to a microcontroller or
microprocessor.
Different Types of Sensors
There are different types of sensors used to measure the physical properties like heartbeat &
pules, Speed, Heat transfer, temperature etc
1. Temperature sensors
Temperature sensors detect the temperature of the air or a physical object and concert that
temperature level into an electrical signal that can be calibrated accurately reflect the
measured temperature. These sensors could monitor the temperature of the soil to help with
agricultural output or the temperature of a bearing operating in a critical piece of equipment
to sense when it might be overheating or nearing the point of failure.
2. Pressure sensors
Pressure sensors measure the pressure or force per unit area applied to the sensor and can
detect things such as atmospheric pressure, the pressure of a stored gas or liquid in a sealed
system such as tank or pressure vessel, or the weight of an object.
3. Motion sensors
Motion sensors or detectors can sense the movement of a physical object by using any one of
several technologies, including passive infrared (PIR), microwave detection, or ultrasonic,
which uses sound to detect objects. These sensors can be used in security and intrusion
detection systems, but can also be used to automate the control of doors, sinks, air
conditioning and heating, or other systems.
4. Level sensors
Level sensors translate the level of a liquid relative to a benchmark normal value into a
signal. Fuel gauges display the level of fuel in a vehicle’s tank, as an example, which
provides a continuous level reading. There are also point level sensors, which are a go-no/go
or digital representation of the level of the liquid. Some automobiles have a light that
illuminates when the fuel level tank is very close to empty, acting as an alarm that warns the
driver that fuel is about to run out completely.
5. Smoke sensors
Smoke sensors or detectors pick up the presence of smoke conditions which could be an
indication of a fire typically using optical sensors (photoelectric detection) or ionization
detection.
6. Infrared (IR) sensors
Infrared sensor technologies detect infrared radiation that is emitted by objects. Non-contact
thermometers make use of these types of sensors as a way of measuring the temperature of an
object without having to directly place a probe or sensor on that object. They find use in
analyzing the heat signature of electronics and detecting blood flow or blood pressure in
patients.
Features of IOT
The most important features of IoT on which it works are connectivity, analyzing,
integrating, active engagement, and many more. Some of them are listed below:
1. Connectivity: Connectivity refers to establish a proper connection between all the things
of IoT to IoT platform it may be server or cloud. After connecting the IoT devices, it needs a
high speed messaging between the devices and cloud to enable reliable, secure and bi-
directional communication.
2. Analyzing: After connecting all the relevant things, it comes to real-time analyzing the
data collected and use them to build effective business intelligence. If we have a good insight
into data gathered from all these things, then we call our system has a smart system.
3. Integrating: IoT integrating the various models to improve the user experience as well.
4. Artificial Intelligence: IoT makes things smart and enhances life through the use of data.
For example, if we have a coffee machine whose beans have going to end, then the coffee
machine itself order the coffee beans of your choice from the retailer.
5. Sensing: The sensor devices used in IoT technologies detect and measure any change in
the environment and report on their status. IoT technology brings passive networks to active
networks. Without sensors, there could not hold an effective or true IoT environment.
Smart City
o In general, a smart city is a city that uses technology to provide services and solve
city problems. A smart city does things like improve transportation and accessibility,
improve social services, promote sustainability, and give its citizens a voice.
o The main goal of a smart city is to optimise city functions and promote economic
growth while also improving the quality of life for citizens by using smart
technologies and data analysis.
Industrial Internet of Things (IIoT)
➢ The industrial internet of things (IIoT) refers to the extension and use of the internet
of things (IoT) in industrial sectors and applications.
➢ The industrial internet of things (IIoT) is the use of smart sensors and actuators to
enhance manufacturing and industrial processes.
➢ IIoT uses the power of smart machines and real-time analytics to take advantage of
the data that "dumb machines" have produced in industrial settings for years.
