Notes And Questions NCERT Class 12 Computer Science Chapter 6 Network and network types

Notes for Class 12

Please refer to Network and network types Class 12 Computer Science Notes and important questions below. The Class 12 Computer Science Chapter wise notes have been prepared based on the latest syllabus issued for the current academic year by CBSE. Students should revise these notes and go through important Class 12 Computer Science examination questions given below to obtain better marks in exams

Network and network types Class 12 Computer Science Notes and Questions

The below Class 12 Network and network types notes have been designed by expert Computer Science teachers. These will help you a lot to understand all the important topics given in your NCERT Class 12 Computer Science textbook. Refer to Chapter 6 Network and network types Notes below which have been designed as per the latest syllabus issued by CBSE and will be very useful for upcoming examinations to help clear your concepts and get better marks in examinations.

1. Learning Outcome as per cbse
Get a basic understanding of computer networks: network stack, basic network hardware, basic protocols, and basic tools
• Network
A Network is a collection of interconnected autonomous computers. A computer which is a part of a network is known as Node or Workstation. The benefits of a network are resource sharing, increased reliability, cost reduction and effective communication.

Structure of a network
• Topology
It is termed as the physical arrangement of computers in a network. There are different types of network topologies such as Bus topology, Ring topology, Star topology, Tree topology, Mesh topology.

Notes And Questions NCERT Class 12 Computer Science Chapter 6 Network and network types

• Types of Network
LAN (Local Area Network) 2. MAN (Metropolitan Area Network 3. WAN(Wide Area Network)
4. PAN (Personal Area Network)

It spread over a small areaIt spread over a very large area
Less cost to set upHigher cost to set up
It is usually a single networkIt is usually a network of many networks

New Technologies

• Cloud computing
It is internet-based computing, where shared resources, software and information are provided to computers and other devices on demand

Type of cloudDescription
Private cloud• A private cloud consists of computing resources used exclusively owned by one business or organization.
• It is not publicly accessible and is owned by a single organization and its authorized external partners.
Public cloud• It refers to the common cloud service made available to multiple subscribers.
• The cloud resources are owned and operated by a third-party cloud service provider and delivered over

• Internet of things (IoT)
It is a phenomenon that connects the things to the Internet over wired or wireless connection.
Eg: IoT devics: Home appliances (Refrigerator, water heater), smart homes (smart door locks, smart bulbs) etc

Wired and wireless networks

Notes And Questions NCERT Class 12 Computer Science Chapter 6 Network and network types

Concept of a client and server

Notes And Questions NCERT Class 12 Computer Science Chapter 6 Network and network types

Networks in which certain computers have special dedicated tasks, providing services to other computers (in the network) are called client server networks. The computer(s)
which provide services are called servers and the ones that use these services are called clients.

Network devices

• NIC: An NIC (network interface card) is a computer hardware designed to allow computers to communicate over a network.
Each NIC card has assigned a unique physical address known as MAC address.
Eg: MAC address: 10:B5:03:63:2E:FC
• Hub: It is a hardware device used to connect several computers together. A hub contains multiple ports. When a packet arrives at one port, it is copied to all the ports of the hub (i.e. in broadcast manner).
• Switch: It is a device used to segment network into different sub networks called subnets or LAN segments. The main advantage is it prevents traffic overloading in a network. It is distinct from a hub that it only forwards the data to the ports involved in the communications rather than all ports.
• Access point (Wireless access point): It is a hardware device that establishes connection of computing devices on wireless LAN with a fixed wire network.

Similar topology and
similar protocol
Similar topology and different
Different topology and different

Network stack

Notes And Questions NCERT Class 12 Computer Science Chapter 6 Network and network types

Amplitude and frequency modulation
• Modulation: It is a process of changing the characteristics of the carrier wave by super imposing the message signal on a high frequency signal.
• Amplitude: The amplitude of the wave is the maximum distance from mean position.
• Frequency: It is the number of waves produced by the source per second.

Notes And Questions NCERT Class 12 Computer Science Chapter 6 Network and network types

Collision in wireless networks
Collisions occur on a network when two or more networked devices transmit data at the same time. The result is that the data collides, becomes corrupted, and needs to be re-sent. CSMA/CA is the protocol used for handling collision in wireless network.

• Working

With CSMA/CA, a device listens for an opportunity to transmit the data. If the carrier is free, the sending device does not immediately transmit data. Rather, it first transmits a signal notifying other devices that it is transmitting for so much time before actually sending the data. The other device refrains from transmitting data for the specified time limit. This means data packets will never collide, although warning packets might.

Error checking

While transmitting data over networks, errors may occur and data may get corrupted. For reliable communication, errors must be detected and corrected. For example if the sender is sending the data in binary form as 10110111 and the data received by the receiver is 10110101. Here the 2nd bit from the right is changed. To avoid such errors in transmission, error detection methods are used.

Notes And Questions NCERT Class 12 Computer Science Chapter 6 Network and network types
Notes And Questions NCERT Class 12 Computer Science Chapter 6 Network and network types

Error checking methods

Notes And Questions NCERT Class 12 Computer Science Chapter 6 Network and network types
Notes And Questions NCERT Class 12 Computer Science Chapter 6 Network and network types

The notion of a MAC address
MAC Address: A MAC address is the unique identifier that is assigned by the manufacturer to a piece of network hardware (like a wireless card or an Ethernet card). A MAC address is made up of six two-digit hexadecimal number, each separated by a colon.
Eg: MAC address 00:1B:f4:11:fA:B7
First three bytes represent the manufacturer- id and last three bytes represents the card-no.

Main idea of routing

• Routing:
Routing is a process which is used to deliver the packet by choosing an optimal path from one network to another.
• Router: It is a network device that forwards data from one network to another.

• Routing table:
It is a table maintained by each router that maintains routing information based on which router determines best path to reach the destination. The information stored in routing table are destination network, next hop, metric such as cost etc.

• Working:
When a packet reaches a router, the router selects the best route to the destination network from its routing tableand forwards the data packets to the neighboring router based on selected best route. This way each router keeps passing the data packets to its neighboring router on best route to the destination and finally the data packet reaches its destination.

IP addresses

It is a unique address used to identify a device on the internet. It is written in dotted decimal form.
Two versions of internet protocol are IPv4 and IPv6.

Notes And Questions NCERT Class 12 Computer Science Chapter 6 Network and network types

DNS(Domain name system)
The URL of a website is also known as domain name. It is the unique name of a website. A domain name mainly consist of www, name describing the website’s purpose, and top level domain such as .com, .net, .org etc Eg:,

• Use of DNS

The websites are mostly accessed through their domain names, because the domain name is much easier to memorise and recognize. But to reach a website, corresponding IP address is needed. So to convert the domain name to its corresponding IP address, DNS is used.
Domain Name Resolution: It refers to the process of obtaining corresponding IP address from a domain name.

Web URLs

A Uniform Resource Locator, also known as web address, is a reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it.

• Elements of URL:

The type of server or protocol: eg: http
The name/address of the server on the internet (domain name): eg:
The location of the file on the server (path): eg: newsite/index.html

TCP (Transmission control protocol)

Notes And Questions NCERT Class 12 Computer Science Chapter 6 Network and network types

It is connection oriented protocol. In TCP, a connection is established before information is send or received.

It is a process of retransmitting a TCP segment. TCP retransmission occurs when time out timer expires before receiving the acknowledgement or 3 duplicate acknowledgements are received from the receiver for the same segment.

• Rate modulation: It is the number of symbol / signaling changes during transmission per time unit. It is measured in baud (Bd)/symbol per second.

• Rate modulation in congestion:

Congestion occurs when the number of packets being transmitted through the network approaches the packet handling capacity of the network. Whenever there is a timeout, TCP assumes congestion in the network and starts to reduce its sending rate. If the sending rate is G at a wireless link with packet loss rate p, the throughput of this link is S = G (1 − p). TCP should increase its sending rate G to get a large throughput if there is no congestion, rather than decreasing its rate.


2GIt allowed some data along with calls in the form of text messages.
Data speeds up to 250Kbps
Transmitted at frequencies between 900Mhz and 1800Mhz
3GIt can handle data in the form of text messages and multimedia such as audio/video
messages along with voice calls.
Data speed upto 20 Mbps
Frequency 2100Mhz
4GData speeds upto 50Mbps
Frequency range is 1800Hz to 2300Hz


It refers to the transmission capacity of a computer or a communications channel. Higher frequencies offer higher bandwidth. It means they can handle more users, more data at the same time.

It governs the rules to connect internet without a direct line from PC to the ISP. A Wi-Fi hotspot is a venue that offers Wi-Fi access.

Basic network tools

Notes And Questions NCERT Class 12 Computer Science Chapter 6 Network and network types

Netstat: It stands for Network Statistics. This command displays incoming and outgoing network connections as well as other network information.

Application Layer

The application layer is at the topmost position of the protocol hierarchy. It is the layer where actual communication is initiated. Eg for some application layer protocols are HTTP, FTP etc.

HTTP stands for hypertext transfer protocol and is used to transfer data across the Web. It allows users of the World Wide Web to exchange information found on web pages. When accessing any web page entering http:// in front of the address tells the browser to communicate over HTTP.


Notes And Questions NCERT Class 12 Computer Science Chapter 6 Network and network types

It is a connectionless text based protocol. Clients (web browsers) send requests through request object of http to web servers for web pages / images etc.
Web server respond accordingly through response object of http. After this cycle (request – response), the connection between client and server across the Internet is disconnected. A new connection must be made for each request (means for each web page).

Working of email

Email – Electronic mail is a facility that allows users to transmit messages across the internet in fast and secure manner.

Notes And Questions NCERT Class 12 Computer Science Chapter 6 Network and network types

Email created using email client program->on press of send button, it is delivered to sender’s mail server through SMTP (Simple mail transfer protocol) ->which further transmit the same through internet to recipient’s mail server->whenever recipient’s email client program’s inbox is opened, that email is delivered to inbox through POP3 (post office protocols 3rd version) ->which user will read in email client program.

Secure communication

Secure communication is when sender and receiver are communicating and do not want a third party to listen it. One method used for secure communication is encryption.
Encryption: It is a technique used to translate the original message into another form.
Decryption: It is a technique of converting encrypted message back to original message.

Notes And Questions NCERT Class 12 Computer Science Chapter 6 Network and network types

HTTPS stands for Hypertext Transfer Protocol Secure and it is a combination of HTTP and SSL/TLS protocols. HTTPS provides encrypted communication. HTTPS encrypts the data and establishes a secure channel over a non-secure network to ensure protected data transfer. Thus data is protected from hackers and eavesdroppers.
SSL stands for secure socket layer protocol. The working of SSL requires that the website has SSL certificate installed which ensure its authenticity. Once installed, the sensitive information obtained from the user through a secure connection over internet.

Network Applications

Remote desktop – It is a type of network application through which a person can work on the desktop of another computer in the same manner as if that computer is in front of the person. 
Remote login- This facility permits a user to work on a program on a distinct computer based on valid login credentials.

Notes And Questions NCERT Class 12 Computer Science Chapter 6 Network and network types
Notes And Questions NCERT Class 12 Computer Science Chapter 6 Network and network types

Evolution of Networking:
ARPANET: The Advanced Research Projects Agency Network (ARPANET) was an early packet switching network and the first network to implement the protocol suite TCP/IP. Both
technologies became the technical foundation of the Internet.
Internet: A network of networks.
WWW: World Wide Web started on 6th August 1991, started by ‘ Berners Lee’ .
Interspace: Interspace is a client/server software program that allows multiple users to communicate online with real-time audio, video and text chat in dynamic 3D environments.
Interspace provides the most advanced form of communication available on the Internet today.

Switching Techniques:
It is a way to send a message from sender to receiver. Information may be switched as it travels through various communication channels. There are three typical switching techniques available for digital traffic.
• Circuit Switching
• Packet Switching
• Message Switching   

Data Communication Terminologies:
Channel: A channel is a separate path through which signals can flow. A channel has a certain capacity for transmitting information, often measured by its bandwidth in Hz or its data rate in bits per second.
Bandwidth: Bandwidth refers to the amount of information that can be transmitted over a network in a given amount of time, usually expressed in bits per second or bps.
Data Transfer Rate: The data transfer rate of a computer network connection is normally measured in units of bits per second (bps).
Larger units are Kbps, Mbps and Gbps, KBps, MBps,GBps
bps means bit per second.
Bps means Byte per second
1 kilobit per second (Kbps) = 1000 bits per second (bps).

1 megabit per second (Mbps) = 1000 Kbps or 10002 bps.
1 gigabit per second (Gbps) = 1000 Mbps
1 Terabit per second (Tbps) = 1000 Gbps

Networking Concepts:  
Network:- To connect the more than one devices via a medium, is called network. 

Why do we need network?
1. Communication
2. Resource sharing
3. Reduce Cost

Types of Network:
1. Local Area Network (LAN)
2. Metropolitan Area Network (MAN)
3. Wide Area Network (WAN)
4. Personal Area Network (PAN)

1. LAN:
Use in small local area, like in an institute or an organization.
* Devices are connected via physical medium.
* Limited distance, up to 150 Meter.
* Example – Intranet

2. MAN:
* Larger than LAN.
* Used in Metropolitan cities.
Range up to 50 KM.

3. WAN:
* Large network
* Public
* Example – Internet

4. PAN:
* For very small distance
* Private Communication
* Example: Bluetooth

Transmission Medium:
A medium which is used to connect the devices and transfers the data from one device to another device.   

Network Devices:
1. Modem
2. Hub
3. Switch
4. Gateway
5. Bridge
6. Router
7. Repeater
8. NIC (Network Interface Card)
9. RJ45 Connector

1. Modem:
♦ The full form of modem is Modulator and demodulator.
♦ A modem is a device or program that enables a computer to transmit data over telephone or cable lines.
♦ A modem converts analog signal to digital signal and vice- versa.
♦ Modem connects computer to internet.
♦ There are two types of modem:
a. Internal Modem
b. External Modem 

2. Hub:
♦ A network device that contains multiple ports.
♦ Provides multiple connections.
♦ When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.
♦ Two types of hub :
a. Active Hub
b. Passive Hub 

3. Switch:
♦ A switch is called smart hub.
♦ Provides multiple connections
♦ A device that filters and forwards packets between LAN segments.   

4. Gateway:
♦ A gateway is a network point that acts as an entrance to another network.
♦ Used to connect two dissimilar networks. 

5. Bridge:
A device that connects two local-area networks (LANs), or two segments of the same LAN that use the same protocol, such as Ethernet. 

6. Router:
A router is a device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs. Routers are located at gateways, the places where two or more networks connect.
A router acts as a dispatcher, choosing the best path for information to travel so it’s received quickly. 

7. Repeater:
Network repeaters regenerate and amplify the weak signals to transmit the information for long distance.

8. NIC (Network Interface Card): NIC card has a physical address of a system; this physical address known as MAC address.
A MAC address is a 6- byte address with each byte separated by a colon. First 3-bytes have Manufacturer id and last 3-bytes represent Card id.   

9. RJ45 Connector: It is used for connecting computers onto Ethernet-based local area networks (LAN). RJ stands for Registered Jack. It is a standardize networking interface. 45
is the number of the interface standard. It has 8-pins.   

Network Topology:
The term Topology refers to the way/layout in which the various nodes or computers of a network are linked together.
The following factors are considered while selecting a topology:
1. Cost
2. Reliability
3. Scalability
4. Bandwidth capacity
5. Ease of installation
6. Ease of troubleshooting
7. Delay involved in routing information from one node to another.

Types of Topologies   

1. Bus Topology
It consists of one continuous length of cable (trunk) that is shared by all the nodes in the network and a terminating resistor (terminator) at each end that absorbs the signal when it reaches the end of line. Without a terminator the electrical signal would reach the end of copper wire and bounce back, causing errors on the network.
Data communication message travels along the bus in both directions until it is picked up by a workstation or server NIC. If the message is missed or not recognized, it reaches the end of the cabling and dissipates at the terminator. Bus Network Topology requires a multipoint connection. 

2. Ring Topology
The physical ring Topology is a circular loop of point-topoint links. Message travel around the ring from node to node in a very organized manner. Each workstation checks the message for a matching destination address. If the address doesn’t match the node simply regenerates the message and sends it on its way. If the address matches, the node accepts the message and sends a reply to the originating sender. 

3. Star Topology
The physical star Topology uses a central controlling hub with dedicated legs pointing in all directions – like points of a star. Each network device has a dedicated point-to-point link to the central hub. There is no direct link between these computers and the computers can communicate via central controller only. 

4. Mesh Topology
In mesh topology, each node is connected to every other node in the network i.e. each node has a dedicated point to point link to every other node as shown. Dedicated
means that the link carries the traffic only between two devices it connects.
In this way there exist multiple paths between two nodes of the network. In case of failure of one path, the other one can be used. 

5. Tree Topology
This topology has Hierarchical structure. This topology connects the node via hubs. Hub, which is present at top level, is called root hub or active hub. Another hub is called secondary hub or passive hub. 

6. Hybrid Topology:
It is a composition of more than one topology. 

8.8 Network Protocol:
1. TCP: Transmission Control Protocol – 4 layers
Application Layer
Transport Layer
Network Interface

2. IP: Internet Protocol
Each computer has unique address over internet, is called IP address. An IP address is an identifier for a computer or device on a TCP/IP network. 

Two types:
I. IPv4 (32-bits or 4-bytes) : IPv4 addresses are canonically represented in dotdecimal notation, which consists of four decimal numbers, each ranging from 0 to 255, separated by dots, e.g.,
II. IPv6 (128-bits or 16-bytes)

3. FTP (File Transfer Protocol): use to transfer files from one computer to another computer.

4. PPP (Point to Point Protocol)

5. HTTP( HyperText Transfer Protocol): To transfer the hypertext pages over internet.

6. Telnet (TELecommunication NETwork) : A network protocol that allows a user on one computer to log into another computer(remote) that is part of the same network or on the internet.

7. GSM: GSM (Global System for Mobile communication) is a digital mobile telephony system that digitizes and compresses data, then sends it down a channel with two other streams of user data, each in its own time slot.

8. CDMA: Code Division Multiple Access (CDMA) is a digital air interface standard, claiming eight to fifteen times the capacity of traditional analog cellular systems.
Each user is separated by a unique code; all users can share the same frequency band.
CDMA is a spread spectrum technology, which means that it spreads the information contained in a particular signal of interest over a much greater bandwidth than the original

9. GPRS: General Packet Radio Service is a packet-switching technology that enables data transfers through cellular networks (wireless). It is used for mobile internet, MMS and other
data communications. In theory the speed limit of GPRS is 115 kbps, but in most networks it is around 35 kbps.

10. WLL: Wireless Local Loop is a system that connects subscribers to the local telephone station irelessly.

Mobile Telecommunication Technologies:
Firstly, when wireless generation started, it was analog communication. That generation is 1G. They used various analog modulation for data transfer. Now when the communication migrated from analog to digital, the foundation of latest communication were led. Hence came 2G. 

1G Technology:
♦ 1G refers to the first generation of wireless telephone technology, mobile telecommunications which was first introduced in 1980s and completed in early 1990s.
♦ It’s Speed was upto 2.4kbps, allowed the voice calls in one country.
♦ It used Analog Signal and AMPS was first launched in USA in 1G mobile systems 

♦ Poor Voice Quality
♦ Poor Battery Life
♦ Large Phone Size
♦ No Security
♦ Limited Capacity
♦ Poor Handoff Reliability

2G Technology:
♦ 2G technology refers to the 2nd generation which is based on GSM.
♦ It was launched in Finland in the year 1991 and used digital signals.
♦ It’s data speed was upto 64kbps.   

Features include:
♦ It enables services such as text messages, picture messages and MMS (multi media message).
♦ It provides better quality and capacity.

♦ 2G requires strong digital signals to help mobile phones work. If there is no network coverage in any specific area, digital signals would weak.
♦ These systems are unable to handle complex data such as Videos.

3G Technology:
♦ 3G technology refer to third generation which was introduced in year 2000s.
♦ Data Transmission speed increased from 144kbps- 2Mbps.
♦ Typically called Smart Phones and features increased its bandwidth and data transfer rates to accommodate web-based applications and audio and video files. 

Features Include:
♦ Providing Faster Communication
♦ Send/Receive Large Email Messages
♦ High Speed Web / More Security
♦ Video Conferencing / 3D Gaming
♦ TV Streaming/ Mobile TV/ Phone Calls
♦ Large Capacities and Broadband Capabilities
♦ 11 sec – 1.5 min. time to download a 3 min Mp3 song.

♦ Expensive fees for 3G Licenses Services
♦ It was challenge to build the infrastructure for 3G
♦ High Bandwidth Requirement
♦ Expensive 3G Phones.
♦ Large Cell Phones

4G Technology:
♦ 4G technology refer to or short name of fourth Generation which was started from late 2000s.
♦ Capable of providing 100Mbps – 1Gbps speed.
♦ One of the basic term used to describe 4G is MAGIC. 

Features Include:
♦ Mobile Multimedia
♦ Global Mobility Support
♦ Integrated Wireless Solution
♦ Customized Personal Services
♦ Also known as Mobile Broadband Everywhere
♦ The next generations of wireless technology that promises higher data rates and expanded multimedia services.
♦ Capable to provide speed 100Mbps-1Gbps.
♦ High QOS and High Security
♦ Provide any kind of service at any time as per user requirements, anywhere.
♦ More Security
♦ High Speed
♦ High Capacity
♦ Low Cost Per-bit

♦ Battery uses is more
♦ Hard to implement
♦ Need complicated hardware
♦ Expensive equipment required to implement next generation network.   

E-Mail (Electronic Mail):
E-Mail is a method to send the messages in digital form. E-mail is a message that may contain text, files, images, or other attachments sent through a network to a specified individual or group of individuals.   

SMTP (Simple Mail Transfer Protocol) is a protocol which is used to transfer the e-mail from sender side. This protocol is known as push protocol.
POP3 (Post Office Protocol version 3): This protocol is used to access e-mail from the server to receiver. This protocol is known as pull protocol.

IMAP(Internet Mail Access Protocol) : Internet Message Access Protocol (IMAP) is an Internet standard protocol used by e-mail clients to retrieve e-mail messages from a mail server over a TCP/IP connection.

Protocols for Chat and Video Conferencing:
VoIP :
VoIP (voice over IP) is the transmission of voice and multimedia content over Internet Protocol (IP) networks. This protocol is used for chat and video conferencing over internet.
Wi-Fi : Wi-Fi (Wireless Fidelity) is the name of a popular wireless networking technology that uses radio waves to provide wireless high-speed Internet and network connections.
WiMax : WiMAX technology is a broadband wireless data communications technology based around the IEE 802.16 standard providing high speed data over a wide area. The letters of WiMAX stand for Worldwide Interoperability for Microwave Access (AXess), and it is a technology for point to multipoint wireless networking.

Network threats (Malware):
Malware is an abbreviated term meaning “malicious software.” This is software that is specifically designed to gain access or damage a computer without the knowledge of the owner.
1. Virus
2. Worms
3. Trojan Horse
4. Cookies
5. Spams
6. Spyware
7. Adware

1. Virus: A virus is a piece of program code that attaches itself to legitimate program code, and runs when the legitimate program runs. It can then infect other programs in that computer or network.
A virus can be repaired, and its damage can be controlled by using good backup procedure.

2. Worms: A worm does not perform any destructive actions, and instead, only consumes system resources to bring it down. A virus modifies a program; a worm however does not
modify a program. Instead it replicates itself again and again.

3. Trojan horse: A Trojan horse is a hidden piece of code, like a virus. A virus modifies information whereas A Trojan horse attempts to reveal confidential information to an attacker.

4. Cookies: A cookie is just one or more pieces of information stored as text strings in a text file on the disk of the client computer (i.e. the web browser).

5. Spam: irrelevant or unsolicited messages sent over the Internet, typically to large numbers of users, for the purposes of advertising, phishing, spreading malware, etc.

6. Spyware – Software that may be installed as part of another program. It may also be installed when a user visits a website with malicious code or when an already running process loads and installs it. This program is designed to report on what the user does to the program creator.

7. Adware: software that automatically displays or downloads advertising material such as banners or pop-ups when a user is online.

Prevention from threats:
♦ Use Genuine and licensed softwares. Avoid pirated softwares.
♦ Visit authentic and official websites.
♦ Never download the contents or files from suspicious websites.
♦ Never share your password or account number over email or message.
♦ Do not follow links from e-mails when performing financial transaction.
♦ Be aware of callers, pop-ups, websites or emails asking for personal information.
♦ Use firewall and reliable anti-virus software.
♦ Never share your personal information in public domain.
♦ Regularly change the passwords of your account.

A firewall is a device (or software feature) designed to control the flow of traffic into and out-of a network. In general, firewalls are installed to prevent attacks.

Hardware Firewall vs Software Firewall:
Hardware Firewall:
♦ Protect an entire network
♦ Implemented on router level
♦ Usually more expensive, harder to configure

Software Firewall:
♦ Protect a single computer
♦ Usually less expensive, easier to configure 

How does a software firewall works:
♦ Inspects each individual “packet” of data as it arrives at either side of the firewall.
♦ Determines whether it should be allowed to pass through or if it should be blocked.

Types of Firewall:
1. Packet filtering firewall
2. Application level gateway
3. Circuit level gateway

HTTPS stands for Hypertext Transfer Protocol Secure. It is the protocol where encrypted HTTP data is transferred over a secure connection. HTTPS does encryption of data between
a client and a server, which protects against eavesdropping, forging of information and tampering of data. 

Information Technology Act, 2000
The Information Technology Act, 2000 (also known as ITA-2000, or the IT Act) is an Act of the Indian Parliament notified on 17 October 2000. It is the primary law in India dealing with cybercrime and electronic commerce.

The original Act contained 94 sections, divided in 19 chapters and 4 schedules. The laws apply to the whole of India. Persons of other nationalities can also be indicted under the law, if the crime involves a computer or network located in India.

The Act provides legal framework for electronic governance by giving recognition to electronic records and digital signatures.

Commission of cybercrime may be divided into three basic groups:
♦ Individual
♦ Organisation
♦ Society at Large
Against Individual
♦ Harassment via Emails
♦ Cyber Stalking
♦ Dissemination of obscene material
♦ Defamation
♦ Hacking/Cracking Indecent Exposure
♦ Computer Vandalism
♦ Transmitting a Virus
♦ Network Trespassing
♦ Unauthorized Control over Computer System
♦ Hacking/Cracking

Against Organisation
♦ Hacking & Cracking
♦ Possession of unauthorized Information
♦ Cyber- Terrorism against Government Organization
♦ Distribution of Pirated Software Etc

Against Society at Large
♦ Pornography
♦ Polluting the youth through indecent exposure
♦ Trafficking

Cyber Law: Cyber law or Internet law is a term that encapsulates the legal issues related to use of the Internet. It is less a distinct field of law than intellectual property or contract law, as it is a domain covering many areas of law and regulation.

Cyber Crime: Criminal activities carried out by means of computers or the Internet.

Hacking: gain unauthorized access to data in a system or computer.

IPR (Intellectual Property Rights) Issues:
Intellectual Property Rights: Intellectual property rights (IPR) is the term applied to the legal protection afforded to innovative and creative materials. It allows owner of IPR to gain from the use of the material and thereby to encourage innovation and creativity.

IPR Issues:
o Copyright law
o The law of confidence
o Patent law
o Design law
o Trademarks
o Copyright and computer programs
o Database copyright and the database right
o Criminal offences

Introduction to web services:
WWW: World Wide Web is an information system where websites and webpages are interconnected and accessible through URL. It is also known as Web.

HTML: HTML is the standard markup language for creating Web pages.
♦ HTML stands for Hyper Text Markup Language
♦ HTML describes the structure and design of Web pages using markup
♦ HTML elements are represented by tags
♦ Browsers do not display the HTML tags, but use them to render the content of the page
♦ The current version of HTML is HTML 5.0   

♦ XML stands for EXtensible Markup Language
♦ XML is a markup language much like HTML
♦ XML was designed to store and transport data
♦ XML was designed to be self-descriptive
♦ XML is a W3C Recommendation     

Domain Name:
Domain names are used to identify one or more IP addresses. Domain names are used in URLs to identify particular web page.

For example,   

Every domain name has a suffix that indicates which top level domain (TLD) it belongs to.
There are only a limited number of such domains. For example:
♦ gov – Government agencies
♦ edu – Educational institutions
♦ org – Organizations (nonprofit)
♦ mil – Military
♦ com – commercial business
♦ net – Network organizations
♦ in – India
♦ th – Thailand

Because the Internet is based on IP addresses, not domain names, every Web server require a Domain Name System (DNS) server to translate domain names into IP addresses.

URL: Uniform Resource Locator. It is the global address of documents and other resources on the World Wide Web.

Website: Collection of web pages which are interlinked to one another. These pages are hypertext pages and link between pages is known as hyperlink.

Web browser: It is application software though which user can access internet.
Example: internet explorer, Google chrome, Mozilla Firefox, opera, UC browser

Web Server: A web server is a system that uses HTTP to accept request and serve the web pages as response to users. Every web server has IP address.

Example: Apache web server, Microsoft’s Internet Information Server (IIS) and nginx (pronounced engine X) from NGNIX.

Web Hosting: Web hosting is a service that allows organizations and individuals to post a website on to the Internet.
A web host, or web hosting service provider, is a business that provides the technologies and services needed for the website or webpage to be viewed in the Internet. Websites are hosted, or stored, on special computers called servers.

Web Scripting: Programming languages which are used to design dynamic web pages, are known as web scripting languages. There are two types of web scripting languages:
1. Client Side Scripting
2. Server Side Scripting

1. Client Side Scripting: The programming language which executes on client side is known as client side scripting.

There are many client-side scripting languages:
♦ JavaScript
♦ VBScript
♦ HTML (Structure)
♦ jQuery etc.

2. Server Side Scripting: program that runs directly on the server.
There are several languages that can be used for server-side programming:
♦ PHP (Hypertext Preprocessor )
♦ ASP (Active Server Pages)
♦ Java and JSP( Java Server Pages)
♦ Python

Cloud Computing: Sharing the resources over internet. A user can access hardware and software remotely on a network or internet by paying some money or free.
Example: Google drive, One drive etc.

Web 2.0 : The second stage of development of the Internet, characterized especially by the change from static web pages to dynamic web pages and the growth of social media.

VoLTE: Voice over Long-Term Evolution (VoLTE) is a standard for high-speed wireless communication for mobile phones and data terminals.

E-Commerce stands for electronic commerce. E-commerce means buying and selling of goods, products and services over the internet. Transactions through internet or electronic
media is also a part of e-commerce.
There are four types of transactions in e-commerce:
i. Business to Business (B2B)
ii. Business to Customer(B2C)
iii. Customer to Business(C2B)
iv. Customer to Customer(C2C)

The money/payment can be transferred using different ways, which are:
A. Online Banking
B. Mobile Banking
C. Payment Apps and services (e-Wallet, UPI)

A. Online Banking: Online Banking used different types of methods to make the payment.
It includes Internet Banking and payment using Debit/Credit Cards.

Internet Banking: It is a simple way of paying for online purchases directly from the customer’s bank. Net banking does not require the user to have a card for payment purposes
but the user needs to register with his/her bank for the net banking facility. While completing the purchase the customer just needs to put in their net banking userid and password.

Payment using Debit/Credit Card: It is similar to internet banking. To make the transaction using debit/credit card, a user should know the card number, name on the card, CVV/CVN number, Valid through etc.

CVV: Card Verification Value
CVN: Card Verification Number

B. Mobile Banking: Mobile banking is a service provided by a bank or other financial institution that allows its customers to conduct financial transactions remotely using a mobile device such as a smartphone or tablet.

C. Payment Apps and Services: A user has to create an account with these apps. It is a prepaid account that allows a customer to store multiple credit cards, debit card and bank account numbers in a secure environment. This eliminates the need to key in account information every time while making payments. Once the customer has registered and created E-Wallet profile, he/she can make payments faster.
Example: BHIM, Paytm, PhonePe etc.