Basics of Networking Notes – Class 11 Web Application (803)

What is Networking?

• Networking is the process of connecting two or more devices so they can communicate and share data with each other.
• A computer network is a group of devices connected through different transmission media such as cables, radio waves, or satellites.
• The devices connected in a network can include computers, printers, scanners, plotters, mobile phones, and other digital devices.
• The main purpose of a computer network is to send, receive, and share data and resources between connected devices.
• Each device connected to a network is called a node.

Concept of Communication

• Data communication is the transmission of digital data between different devices through a telecommunication network.
• A telecommunication network allows computers and other digital devices to communicate and exchange different types of data, such as text, numbers, pictures, audio, and video, using wired (cable) or wireless media.
• When computers and other digital devices are connected to form a network, they can communicate and provide several advantages, such as:
  • Resource sharing (printers and storage devices)
  • Information sharing using the Web or the Internet
  • Video conferencing and instant messaging
  • Parallel computing

Components of Data Communication

• Data communication involves five main components that help in exchanging information over a network.
• Message: The information or data being communicated, such as text, numbers, pictures, audio, or video.
• Sender: The device that sends the message, such as a computer, workstation, mobile phone, or camera.
• Receiver: The device that receives the message, such as a computer, workstation, mobile phone, or television.
• Transmission Medium: The path through which the message travels from the sender to the receiver. It can be twisted-pair cable, coaxial cable, optical fiber, radio waves, microwaves, or satellites, and is often a combination of different media.
• Protocol: A set of rules that governs data communication and ensures proper communication between devices. Common protocols include TCP/IP, HTTPS, SMTP, IMAP, and POP3.

Internet

• The Internet originated from the term “internetwork” and has evolved into a globally connected network that enables devices to transmit and receive information in real time.
• The Internet has a wide range of applications, including:
  • Email and instant messaging
  • File sharing and data transfer
  • Movies, music, and gaming
  • Online shopping
  • Online banking, cryptocurrency, and other financial services

Advantages of Computer Networking

• Data and Resource Sharing: A network allows users to share files, printers, scanners, and other resources among multiple devices.
• Cost Saving: Sharing devices such as printers and scanners reduces the need to purchase separate equipment for each computer.
• Data Backup and Increased Storage: Important data can be backed up on servers or cloud storage services like Google Drive, OneDrive, and Dropbox, reducing the storage requirements of individual computers.
• Improved Security: A network can protect connected devices using a firewall, helping to secure them against virus attacks.

Disadvantages of Computer Networking

• High Setup Cost: Installing a network can be expensive due to the cost of cables, networking equipment, and installation.
• Difficult Network Management: Large networks require skilled professionals to manage and maintain them, making administration more complex.
• Security Risks: Networks, especially Wide Area Networks (WANs), are vulnerable to hacking and virus attacks, and malware can spread quickly between connected computers.
• Risk of Data Loss: If the network crashes, users may temporarily lose access to information or, in some cases, important data may be lost.

Data Communication Terminology

Communication Channel

• A communication channel is the path used to transfer information from one or more senders (transmitters) to one or more receivers.
• The capacity of a communication channel to transmit information is measured by its bandwidth (in Hertz) or data rate (in bits per second).
• Communication channels use two types of transmission media:
  • Physical transmission media: Twisted-pair cable, coaxial cable, and optical fiber.
  • Logical or wireless transmission media: Microwave, satellite, radio, and infrared communication.

Bandwidth

• Bandwidth is the amount of data that can be transferred over a network in a specific amount of time.
• It is measured as a bitrate in bits per second (bps), Megabits per second (Mbps), or Gigabits per second (Gbps).

Data Transfer Rate (DTR)

• Data Transfer Rate (DTR) is the amount of digital data transferred from one place to another in a given time. It represents the speed at which data travels over a network.
• The data transfer rate is measured in bits per second (bps). Network devices use units such as Kbps, Mbps, Gbps, and Tbps to indicate the maximum data transfer speed they support.
• Common data transfer rate units are:
  • 1 Kbps = 10³ bps
  • 1 Mbps = 10³ Kbps = 10⁶ bps
  • 1 Gbps = 10³ Mbps = 10⁹ bps
  • 1 Tbps = 10³ Gbps = 10¹² bps
• To avoid confusion between bits and bytes, network speeds are always expressed in bps (bits per second), whereas Bps (Bytes per second) is used for data storage and file transfer.
• The relationship between bytes and bits is:
  • 1 KBps = 8 Kbps
  • 1 MBps = 8 Mbps
  • 1 GBps = 8 Gbps

IP Address

• An IP (Internet Protocol) address is a unique numerical address that identifies a specific device or interface on a network.
• An IP address is generally represented as four octets (numbers) separated by dots, with each octet ranging from 0 to 255.
  Example: 222.145.142.231
• An IP address consists of two parts:
  • Network Part: Identifies the network or subnet where the device is located.
  • Host Part: Identifies the specific device within that network.

Network Devices

Modem

• A modem (Modulator-Demodulator) is a hardware device that connects a computer or router to the Internet by converting analog signals into digital signals and digital signals into analog signals.
• Fiber optic connections do not require a modem because the signals remain digital throughout the transmission.

Router

• A router connects multiple devices and networks, such as LANs and WANs, and directs data packets to their correct destination using a routing table.
• Routers analyze network traffic and forward data packets efficiently, helping create multiple interconnected networks instead of one large network.

Difference between Modem and Router

Modem	Router
Connects a home network to the Internet.	Connects multiple devices and routes network traffic.
Converts analog signals into digital signals and vice versa.	Creates and manages a Local Area Network (LAN).

Gateway

• A gateway is a network device that connects two different networks that may use different networking models or protocols.
• A gateway can operate at any network layer and is generally more complex than a router or switch.

Repeater

• A repeater is a hardware device that regenerates weak or corrupted signals to their original strength, helping extend the transmission distance of a network.

Hub

• A hub is a multiport repeater that connects multiple devices in a network.
• It cannot filter data and sends every data packet to all connected devices, making it less efficient because it cannot determine the correct destination.

Switch

• A switch is an intelligent hub that performs error checking before forwarding data.
• It forwards data only to the correct destination port, improving the efficiency and performance of the network.

Difference between Hub and Switch

Hub	Switch
A hub is a repeater with multiple ports.	A switch is a smart version of a hub.
It cannot filter data.	It performs error checking before forwarding data.

Wi-Fi Card

• A Wi-Fi card is a hardware device that enables a computer or other device to connect to a wireless network (Wi-Fi) without using physical cables. Most modern devices have built-in Wi-Fi cards, while external cards can also be installed if required.
• Wireless signals generally cover a distance of 23 to 46 metres

Leased Line

• A leased line is a dedicated, fixed-bandwidth Internet connection mainly used by businesses that require high-speed, reliable, and uninterrupted data communication.
• A leased line is more stable and reliable than a normal broadband connection but is also more expensive.

Types of Networks

• Computer networks can be classified based on their size and purpose, ranging from a network within a single home to millions of connected devices across the world.
• The main types of computer networks are:
  • PAN (Personal Area Network)
  • LAN (Local Area Network)
  • MAN (Metropolitan Area Network)
  • WAN (Wide Area Network)
  • VPN (Virtual Private Network)

PAN (Personal Area Network)

• PAN (Personal Area Network) is a computer network formed in a small area, such as a room or a house, with a range of up to 10 metres.
• It generally consists of computers, laptops, mobile phones, tablets, and other personal devices, which can communicate with each other or connect to the Internet.

Advantages of PAN

• It is a relatively safe and secure network.
• It is a short-range solution for communication up to 10 metres.

Disadvantages of PAN

• It is limited by distance.
• It may experience interference from networks using the same radio bands.

LAN (Local Area Network)

• LAN (Local Area Network) is a group of computers and peripheral devices connected within a radius of up to 10 km. It is commonly used in a small campus or different blocks of an organization.

Advantages of LAN

• Reduces the cost of equipment and software by allowing them to be shared over the network.
• Helps reduce data redundancy by storing data on a single device with a backup on the cloud.

Disadvantages of LAN

• Installing a LAN can be expensive and time-consuming.
• Since a LAN is managed by an administrator, privacy can be an issue.

MAN (Metropolitan Area Network)

• MAN (Metropolitan Area Network) is a large LAN that covers a city or region with a radius of up to 50 km, usually using optical fiber. Broadband networks provided by companies such as Airtel, Jio, and BSNL within a city are examples of MAN.

Advantages of MAN

• Provides high-speed communication because it uses optical fiber cables.
• Can be used to cover an entire city.

Disadvantages of MAN

WAN (Wide Area Network)

• WAN (Wide Area Network) is a network spread across a large geographical area, such as cities, countries, and continents. The Internet and mobile phone networks are examples of WAN.

Advantages of WAN

• Its wide coverage helps businesses communicate easily.
• Supports the connection of mobile phones, laptops, tablets, gaming consoles, and other devices.
• Can be used to connect remote and hazardous locations.

Disadvantages of WAN

• Setting up web servers and cloud storage devices is expensive.
• It is difficult to maintain.
• It is vulnerable to viruses, worms, trojans, and hackers.

Other Types of Networks

• VPN (Virtual Private Network)
• WLAN (Wireless Local Area Network)
• EPN (Enterprise Private Network)
• CAN (Campus Area Network)

Comparison of PAN, LAN, MAN, and WAN

Parameter	PAN	LAN	MAN	WAN
Area Covered	Up to 10 m radius	5–10 km radius	Covers a city (up to 100 km radius)	Covers cities, countries, and continents
Cost	Cheap	Inexpensive	Cost-effective	Expensive
Communication Medium	Wireless or Wired	Coaxial cable and Ethernet	Optical fiber, radio waves, and microwaves	Optical fiber, radio waves, satellites, and microwaves
Devices Used	Wi-Fi, Infrared, Bluetooth	Router, Modem, Hub, Switch, Repeaters	Router, Gateway, Repeaters	Satellite receivers, Routers, Gateways, Radio wave and Microwave towers

Web Architecture

• Web Architecture is the conceptual structure of a network. The World Wide Web (WWW) or Internet is a constantly changing system that enables communication between users and interaction between different systems and subsystems.
• The main components of Web Architecture are:
  • Client: The web browser or any application used by the user to interact with a server. It sends requests to the server and receives responses.
  • Server: The computer or group of computers that hosts a website or web application. It processes client requests and sends the appropriate response.
  • Network: The infrastructure that connects the client and the server and enables communication between them.
  • Database: Stores the data that is retrieved and used by the website or web application.
  • Website or Web Application Structure: Refers to the organization and structure of a website or web application, including its layout, navigation, and overall appearance.

Types of Web Architecture

• Peer-to-Peer (P2P) Architecture: In a Peer-to-Peer (P2P) architecture, two or more devices are connected directly and share resources without using a separate server.
• Client-Server Architecture: In a Client-Server architecture, the server hosts, manages, and delivers resources and services requested by the client. It consists of one or more client devices connected to a central server through a network or the Internet.

Network Threats and Security Measures

• As the use of computer networks for data access and resource sharing increases, network security has become a major concern.
• The Internet is an insecure communication channel, making it vulnerable to threats such as phishing, viruses, trojans, worms, and other cyber-attacks.
• To stay safe on a network, it is important to understand the possible security risks and follow appropriate security measures.

Virus

• A virus is a software program that can harm a computer by overwriting or corrupting system files. It can self-replicate by copying itself to other programs, executable files, or documents.
• The main purpose of a virus is to infect vulnerable systems, gain administrative control, and steal sensitive user data.
• Based on the method of infection, viruses are classified into:
  • File Viruses
  • Boot Sector Viruses
  • Macro Viruses
  • Script Viruses

Malware

• Malware (Malicious Software) is software designed to compromise computer functions, steal data, bypass access controls, or cause harm to a computer system. It is a broad term that includes different types of malicious programs.
• Common types of malwate include:
  • Adware
  • Bots
  • Spyware
  • Ransomware
  • Viruses
  • Trojan Horses
  • Worms
• A malware-infected device may show the following symptoms:
  • The device becomes very slow.
  • The web browser takes longer to load websites.
  • There are network connection problems.
  • The system crashes or hangs frequently.

Phishing

• Phishing is a cybercrime in which a person is contacted through phone calls, emails, or text messages by someone pretending to be a legitimate organization to steal sensitive information such as bank account details, credit card details, date of birth, PIN, Aadhaar number, and passwords.
• Common types of phishing include:
  • Vishing: Voice Phishing
  • Smishing: SMS Phishing
• Common phishing scams include:
  • Big prizes and lucrative offers that encourage users to click on links.
  • Limited-time offers that create a sense of urgency.
  • Misspelt popular websites that look similar to genuine websites.
  • Unknown email attachments that may contain ransomware or viruses.

Protection Against Phishing

• Use spam filters to block spam and fraudulent emails.
• Hover over links before clicking and ensure the website uses HTTPS with a valid SSL certificate.
• Never share personal or banking information through email, as banks do not ask for such information via email.

Spam

• Spam is the practice of sending unsolicited messages or emails to a large number of recipients, mainly for commercial advertising or other promotional purposes.
• Common spam email subjects include:
  • Online Gambling and Games
  • Adult Content
  • Financial Services and Loans
  • Online Courses and Degrees

Denial of Service (DoS)

• A Denial of Service (DoS) attack is a cyber-attack in which an attacker tries to make a computer, server, or network resource unavailable to its intended users by temporarily or permanently disrupting its services.
• Some major DoS attacks include:
  • February 2020: Amazon Web Services experienced a 2.3 Tb/s attack.
  • February 2023: Cloudflare faced a 71 million requests per second DoS attack.

Security Tools

Antivirus

• Antivirus is software that protects a computer from malicious and unwanted programs by detecting, disabling, and removing them.
• It works by maintaining a database of malware definitions, which is updated automatically. The antivirus scans files and compares them with this database to identify and remove harmful programs.

Firewall

• A firewall protects the internal network of an organization, home, or individual from malicious traffic coming from external networks.
• It inspects network traffic and allows only the data that meets the security rules to pass through the network.

Password Manager

• A password manager is a software application that helps users store and organize passwords securely.
• Passwords are usually stored in encrypted form and can be accessed using a master password, which should be strong and secure.