Internet and Networking Notes for Competitive Exams

The internet has changed the way we study, work, shop, bank and talk to each other. Questions on the internet and computer networks are asked in banking, SSC, railways, insurance, defence and many other examinations, usually as direct questions on terms, full forms, protocols and devices. This note explains the history of the internet, how it works, the main internet terms and protocols, types of networks, topologies, networking devices, the OSI model, cloud computing and India's internet milestones, with tables and examples, in simple language.

What Is the Internet?

The internet is a global network of computer networks that use a common set of rules (protocols) to share information. It began as ARPANET, a project of the US Department of Defense, in 1969. The World Wide Web (WWW), a system of linked web pages, was invented by Tim Berners-Lee at CERN around 1989 to 1991. The internet and the web are not the same: the internet is the vast network, while the web is a service that runs over it, along with email, file transfer and others. Email was introduced by Ray Tomlinson in 1971, who also chose the "@" symbol. In India, public internet service began on 15 August 1995, offered by Videsh Sanchar Nigam Limited (VSNL).

How the Internet Works

Every device connected to the internet has an IP (Internet Protocol) address, a unique number such as 192.168.1.1. IPv4 uses 32 bits and is written as four numbers from 0 to 255; IPv6 uses 128 bits and was created because IPv4 addresses are running out. People remember names, not numbers, so the Domain Name System (DNS) converts a name like www.example.com into its IP address, like a phone book. When you type a web address (URL) in a browser (Chrome, Firefox, Edge, Safari), a request goes through your Internet Service Provider (ISP) to the web server, which sends back the page. Data travels in small units called packets, which are put together at the destination. The set of rules for this is TCP/IP (Transmission Control Protocol/Internet Protocol).

Important Protocols

URL, Domain and Email Terms

A URL (Uniform Resource Locator) is the address of a web page: it has the protocol (https), the domain name (www.example.in) and the path (/page). Domain extensions show the type of site: .com (commercial), .org (organisation), .edu (education), .gov (government), .net (network) and .in (India). In email, To is the main recipient, Cc (carbon copy) sends a visible copy, and Bcc (blind carbon copy) sends a hidden copy. Spam is unwanted bulk email, and the Inbox stores received mail. A cookie is a small file stored by a website on your device to remember your preferences. A hyperlink is a clickable link to another page, and a bookmark saves a page address for later.

Types of Networks

An intranet is a private network within an organisation that uses internet technology. An extranet allows limited outside access to an intranet for partners or customers. A VPN (Virtual Private Network) creates a secure, encrypted connection over the public internet. A firewall is a security system that filters incoming and outgoing traffic.

Network Topologies

• Bus: all devices share one main cable. Cheap but a break in the cable stops the network.
• Star: all devices connect to a central hub or switch. Easy to manage; the failure of the central device stops all.
• Ring: devices form a closed loop; data travels in one direction.
• Mesh: every device is connected to every other device; very reliable but expensive.
• Tree (hybrid): a mix of star and bus.

Networking Devices

Transmission Media and Speed

Wired media include twisted-pair cable (used in telephone and Ethernet), coaxial cable (cable TV) and optical fibre (light signals; fastest and most secure). Wireless media include radio waves, microwaves, infrared, Bluetooth and Wi-Fi. Wi-Fi follows the IEEE 802.11 standard, and Ethernet follows IEEE 802.3. Speed is measured as bandwidth in bits per second: Kbps, Mbps and Gbps. Remember that 1 byte is 8 bits, so a 100 Mbps connection can download about 12.5 megabytes per second at best. Modes of data transmission are simplex (one way, like a TV broadcast), half duplex (two ways but one at a time, like a walkie-talkie) and full duplex (both ways at the same time, like a phone call).

The OSI Model

The Open Systems Interconnection (OSI) model has seven layers. From bottom to top, they are: 1. Physical, 2. Data Link, 3. Network, 4. Transport, 5. Session, 6. Presentation, 7. Application. A popular memory phrase is "Please Do Not Throw Sausage Pizza Away". The network layer handles IP addresses and routing, the transport layer ensures reliable delivery (TCP), and the application layer is closest to the user (HTTP, SMTP). The TCP/IP model has four layers: Network Access, Internet, Transport and Application.

Cloud Computing and the Web Generations

Cloud computing means using servers on the internet to store data and run programs instead of using a local computer. The service models are IaaS (Infrastructure as a Service), PaaS (Platform as a Service) and SaaS (Software as a Service, like Google Docs). Web 1.0 was read-only, Web 2.0 is interactive and social (blogs, social media), and Web 3.0 aims at a smarter, decentralised web. The Internet of Things (IoT) connects everyday objects to the internet.

Internet in India

India has one of the largest numbers of internet users in the world. Important milestones include the launch of public internet service in 1995, the National Optical Fibre Network (BharatNet) to connect villages, the launch of 5G services in October 2022, and the success of Unified Payments Interface (UPI) for digital payments. The registry for the .in domain is the National Internet Exchange of India (NIXI). The Indian Computer Emergency Response Team (CERT-In) deals with cyber security incidents.

Search Engines, Browsers and Safe Browsing

A browser is the software that lets you open web pages, while a search engine is a website that helps you find pages by keywords. Google, Bing and DuckDuckGo are search engines; Chrome, Firefox, Edge and Safari are browsers. Many students mix up the two. A web page is a single document, a website is a set of pages with a common address, and a web server is the computer that stores and delivers these pages. For safe browsing, look for the padlock sign and the https in the address, avoid clicking on unknown links, do not share passwords, and keep your browser updated. Private or incognito mode does not store your history on the device, but it does not make you invisible on the internet.

Practice Questions on Networking

Try to answer these. Which device connects two different networks and directs packets? Router. Which topology uses a central device to connect all computers? Star topology. Which protocol is used to send emails? SMTP. Which protocol is used for secure web browsing? HTTPS. How many bits are in an IPv6 address? 128. Which layer of the OSI model deals with routing? The network layer. Which medium uses light to carry data? Optical fibre. What is the full form of URL? Uniform Resource Locator. What is the name of the first computer network that led to the internet? ARPANET. Practise these, make your own questions from the tables, and try to explain each term to a friend in your own words.

Quick Revision

• ARPANET 1969; WWW by Tim Berners-Lee; email by Ray Tomlinson; VSNL launched the internet in India in 1995.
• IPv4 is 32-bit; IPv6 is 128-bit; DNS converts names to IP addresses; HTTPS is secure HTTP.
• LAN, MAN, WAN; star topology uses a central hub or switch; router connects networks.
• OSI has seven layers; fibre optic cable is the fastest medium.

Networking terms are easy to learn if you connect them with what you use daily: Wi-Fi at home, email on your phone and websites in your browser. Revise the tables, and test yourself on full forms, and you will find this section easy and scoring.

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Frequently Asked Questions (FAQ)

What is the internet?

The internet is a global network of interconnected computer networks that use common protocols such as TCP/IP to share information.

What is the difference between the internet and the World Wide Web?

The internet is the worldwide network infrastructure, while the World Wide Web is a service on the internet that uses web pages linked by hyperlinks.

Who invented the World Wide Web?

Tim Berners-Lee invented the World Wide Web at CERN around 1989 to 1991.

What is an IP address?

An IP address is a unique number given to each device on a network to identify it, such as 192.168.1.1 in IPv4.

What does DNS do?

The Domain Name System converts domain names like www.example.com into IP addresses that computers use.

What is the difference between HTTP and HTTPS?

HTTPS is the secure version of HTTP. It encrypts the data exchanged between your browser and the website.

What is the difference between a hub and a switch?

A hub sends data to all connected devices, while a switch sends data only to the intended device, which makes it more efficient.

What does a router do?

A router connects different networks and directs data packets to their destination using IP addresses.

What are LAN, MAN and WAN?

LAN covers a small area such as a building, MAN covers a city and WAN covers large areas like countries; the internet is the largest WAN.

How many layers are in the OSI model?

The OSI model has seven layers: Physical, Data Link, Network, Transport, Session, Presentation and Application.

What is cloud computing?

Cloud computing is the use of remote servers on the internet to store data and run programs instead of a local computer.

When did the internet start in India?

Public internet service in India began on 15 August 1995, provided by VSNL.