Chapter 10 - Computer Networks
10.1 Introduction to Computer Networks
What is a Computer Network?
A computer network is a collection of interconnected computers and devices that can:
- Share data
- Share resources (printers, files, internet)
- Communicate with each other
📌 Communication happens through wired or wireless media.
Advantages of Computer Networks
- Resource sharing
- Fast communication
- Centralized data management
- Cost efficiency
- Scalability
Examples of Networks
- School computer lab
- Internet
- Banking networks
- Office LAN
10.2 Evolution of Networking
Early Networking
- Standalone computers
- No data sharing
- Manual data transfer (floppy disks)
Modern Networking
- Interconnected computers
- Internet-based communication
- Cloud computing
- Mobile and wireless networks
Key Milestones
- ARPANET → foundation of Internet
- Client–Server architecture
- Wireless & mobile networks
- IoT (Internet of Things)
📌 Networking evolved to support speed, scalability, and global connectivity.
10.3 Types of Networks
Networks are classified based on geographical coverage.
🔹 1️⃣ LAN (Local Area Network)
- Covers small area (school, office)
- High speed
- Low cost
📌 Example: Computer lab
🔹 2️⃣ MAN (Metropolitan Area Network)
- Covers a city
- Medium speed
📌 Example: Cable TV network
🔹 3️⃣ WAN (Wide Area Network)
- Covers large geographical area
- Slower than LAN
📌 Example: Internet
🔹 4️⃣ PAN (Personal Area Network)
- Very small range
- Used for personal devices
📌 Example: Bluetooth connection
Comparison Table (IMPORTANT)
| Network | Area Covered | Example |
|---|---|---|
| PAN | Few meters | Bluetooth |
| LAN | Building | School |
| MAN | City | Cable network |
| WAN | Country/world | Internet |
10.4 Network Devices
Network devices help in data transmission and control.
🔹 1️⃣ NIC (Network Interface Card)
- Connects computer to network
- Has MAC address
🔹 2️⃣ Hub
- Simple device
- Broadcasts data to all devices
- Less secure
🔹 3️⃣ Switch
- Smarter than hub
- Sends data only to intended device
- More efficient
🔹 4️⃣ Router
- Connects different networks
- Routes data packets
- Used to connect LAN to Internet
🔹 5️⃣ Modem
- Modulates and demodulates signals
- Converts digital ↔ analog
🔹 6️⃣ Repeater
- Regenerates weak signals
- Extends network range
Hub vs Switch (VERY IMPORTANT)
| Hub | Switch |
|---|---|
| Broadcasts data | Sends to specific device |
| Less secure | More secure |
| Slower | Faster |
10.5 Networking Topologies
What is Network Topology?
The physical or logical arrangement of network devices.
🔹 1️⃣ Bus Topology
- Single central cable
- Low cost
- Cable failure breaks network
🔹 2️⃣ Star Topology
- Central hub/switch
- Easy to manage
- Hub failure affects network
🔹 3️⃣ Ring Topology
- Circular connection
- Data flows in one direction
- Failure breaks ring
🔹 4️⃣ Mesh Topology
- Every node connected to every other
- Very reliable
- Very expensive
🔹 5️⃣ Tree Topology
- Hierarchical structure
- Combination of star and bus
Comparison Table (IMPORTANT)
| Topology | Advantage | Disadvantage |
|---|---|---|
| Bus | Cheap | Cable failure |
| Star | Easy management | Hub failure |
| Ring | Equal access | Difficult to troubleshoot |
| Mesh | Highly reliable | Costly |
| Tree | Scalable | Complex |
10.6 Identifying Nodes in a Networked Communication
🔹 MAC Address
- Physical address
- 48-bit unique number
- Assigned by manufacturer
📌 Example:
00:1A:2B:3C:4D:5E
🔹 IP Address
- Logical address
- Identifies device on a network
Types of IP Address
IPv4
- 32-bit address
Example:
192.168.1.1
IPv6
- 128-bit address
Example:
2001:db8::1
MAC vs IP Address (IMPORTANT)
| MAC Address | IP Address |
|---|---|
| Physical | Logical |
| Permanent | Can change |
| Assigned by manufacturer | Assigned by network |
10.7 Internet, Web and the Internet of Things
🔹 Internet
- Global network of networks
- Uses TCP/IP protocol
🔹 World Wide Web (WWW)
- Collection of web pages
- Uses HTTP/HTTPS
- Accessed via browsers
📌 Internet ≠ Web
🔹 Internet of Things (IoT)
- Network of smart devices
- Devices communicate automatically
📌 Examples:
- Smart bulbs
- Smart watches
- Smart homes
- Health monitoring devices
10.8 Domain Name System (DNS)
What is DNS?
DNS converts domain names into IP addresses.
📌 Example:
www.google.com → 142.250.183.14
Why DNS is Needed?
- Humans remember names
- Computers understand IPs
DNS Components
- Domain name
- IP address
- DNS servers
Domain Name Structure
www.school.edu.in
| Part | Meaning |
|---|---|
| in | Country |
| edu | Organization |
| school | Domain |
| www | Host |
📝 NCERT EXAM SUMMARY (MUST MEMORISE)
- Network = interconnected computers
- LAN, MAN, WAN, PAN
- Hub vs Switch vs Router
- Topologies and their pros/cons
- MAC = physical address
- IP = logical address
- Internet ≠ Web
- DNS converts domain → IP
- IoT connects smart devices
📌 COMMON CBSE QUESTION TYPES
✔ Define network / DNS / IoT ✔ Difference between LAN and WAN ✔ Hub vs Switch ✔ Star vs Bus topology ✔ MAC vs IP address ✔ Case-study based networking questions
Short Answer Questions & Answers (25)
SET 1: Simple Definitions & Usage (10 Questions)
Q1. What is a computer network?
Answer: A computer network is a collection of interconnected computers and devices that can communicate with each other. It allows sharing of data, hardware, and software resources. Communication can be wired or wireless.
Q2. What is LAN? Give one example.
Answer: LAN (Local Area Network) is a network that covers a small geographical area such as a room, building, or school. It provides high-speed data transfer. Example: A school computer laboratory.
Q3. What is WAN?
Answer: WAN (Wide Area Network) is a network that covers a large geographical area such as a country or the entire world. It connects multiple LANs together. Example: The Internet.
Q4. What is a network topology?
Answer: Network topology refers to the physical or logical arrangement of computers and cables in a network. It determines how data flows between devices. Common topologies include bus, star, ring, and mesh.
Q5. What is a router?
Answer: A router is a network device that connects two or more networks. It directs data packets to their correct destination using IP addresses. Routers are commonly used to connect a LAN to the Internet.
Q6. What is a switch?
Answer: A switch is a networking device that connects multiple devices within a LAN. It forwards data only to the intended device using MAC addresses. This improves network speed and security.
Q7. What is a MAC address?
Answer: A MAC (Media Access Control) address is a unique physical address assigned to a network interface card. It is permanent and assigned by the manufacturer. MAC addresses are used within local networks.
Q8. What is an IP address?
Answer: An IP address is a logical address assigned to a device on a network. It uniquely identifies the device for communication. IP addresses can change depending on the network.
Q9. What is DNS?
Answer:
DNS (Domain Name System) translates domain names into IP addresses. It allows users to access websites using easy-to-remember names instead of numerical IPs.
Example: www.google.com → IP address.
Q10. What is Internet of Things (IoT)?
Answer: IoT refers to a network of physical devices connected to the Internet. These devices collect and exchange data automatically. Examples include smart watches, smart bulbs, and home automation systems.
SET 2: Comparison & Advantage-Based Questions (10 Questions)
Q11. Differentiate between LAN and WAN.
Answer: LAN covers a small area like a building, whereas WAN covers a large geographical area. LAN offers high speed and low cost, while WAN is slower and more expensive. Internet is an example of WAN.
Q12. Compare hub and switch.
Answer: A hub broadcasts data to all connected devices, whereas a switch sends data only to the intended device. Switches are faster and more secure. Hubs are rarely used today.
Q13. Compare star and bus topology.
Answer: Star topology uses a central hub or switch, making it easy to manage. Bus topology uses a single cable and is cheaper but less reliable. Failure of the main cable disrupts the entire bus network.
Q14. Differentiate between MAC address and IP address.
Answer: MAC address is a physical and permanent address, while IP address is logical and can change. MAC is assigned by the manufacturer, IP by the network. Both are used for identifying devices.
Q15. What are the advantages of computer networks?
Answer: Computer networks allow resource sharing, fast communication, and centralized data management. They reduce costs and improve efficiency. Networks also support collaboration and remote access.
Q16. Why is switch preferred over hub?
Answer: A switch sends data only to the intended device, reducing network traffic. It improves speed and security. A hub sends data to all devices, causing congestion.
Q17. State two advantages of star topology.
Answer: Star topology is easy to install and manage. Failure of one node does not affect others. It also provides better performance compared to bus topology.
Q18. Why is mesh topology rarely used?
Answer: Mesh topology is very expensive due to excessive cabling. It is difficult to install and maintain. Although reliable, it is not cost-effective for normal networks.
Q19. Internet and World Wide Web are not the same. Justify.
Answer: Internet is a global network of networks, while the Web is a service that runs on the Internet. The Web consists of websites accessed using browsers. Internet supports many services like email and FTP.
Q20. What is the advantage of DNS?
Answer: DNS makes the Internet user-friendly by allowing access through domain names. Users do not need to remember complex IP addresses. It ensures fast and accurate website access.
SET 3: Real-Life Scenario Based Questions (5 Questions)
Q21. A school wants to connect computers within a laboratory to share files and printers. Which type of network should be used and why?
Answer: A LAN should be used because it covers a small area like a laboratory. LAN provides high-speed data transfer and is cost-effective. It allows easy sharing of resources like printers and files.
Q22. A company has offices in multiple cities and wants all offices connected. Which network type is suitable?
Answer: A WAN is suitable because it covers large geographical areas. It connects multiple LANs across cities. The Internet or leased lines can be used for connectivity.
Q23. A network administrator wants high reliability even if one connection fails. Which topology is best and why?
Answer: Mesh topology is best because every node is connected to multiple nodes. Failure of one link does not affect communication. It provides maximum reliability and fault tolerance.
Q24. A home user wants Internet access on a laptop, mobile phone, and smart TV. Which devices and technologies are required?
Answer: A router with Wi-Fi capability is required. The router connects the home network to the Internet. Devices use wireless communication to access the Internet simultaneously.
Q25. A user types a website name in a browser and the webpage opens. Explain the role of DNS in this process.
Answer: DNS converts the website name into its corresponding IP address. The browser uses this IP address to locate the server. DNS makes website access fast and user-friendly.