ICT – COMPUTER NETWORKS (For EMRS/NVS/KVS/DSSSB/UGC NET teaching exams)
⭐ 1. What is a Computer Network?
A computer network is a system where two or more devices are connected for communication and resource sharing.
Key functions
Data sharing
File sharing
Hardware sharing (printers, scanners)
Internet sharing
Remote access
Hindi
कंप्यूटर नेटवर्क वह व्यवस्था है जिसमें दो या अधिक डिवाइस आपस में जुड़े होते हैं ताकि डेटा, फाइल, हार्डवेयर और इंटरनेट साझा किया जा सके।
⭐ 2. Types of Networks (Very Important)
1. PAN – Personal Area Network
Very small range (Bluetooth, Hotspot).
Hindi: व्यक्तिगत नेटवर्क (जैसे ब्लूटूथ).
2. LAN – Local Area Network
Small area — office, school, building.
Faster speed, more secure.
Hindi: छोटी सीमित जगह (ऑफिस/स्कूल).
3. MAN – Metropolitan Area Network
City-level network.
Example: Cable TV network.
Hindi: शहर-स्तरीय नेटवर्क.
4. WAN – Wide Area Network
Country level / global level.
Example: Internet.
Hindi: व्यापक क्षेत्र नेटवर्क (इंटरनेट).
5. VPN – Virtual Private Network
Encrypted secure tunnel.
Hindi: सुरक्षित वर्चुअल नेटवर्क (प्राइवेट कनेक्शन).
⭐ 3. Network Topologies (Most Important)
1. Bus Topology
Single backbone cable
Cheap, simple
Entire network fails if backbone breaks
Hindi: एक मुख्य केबल पर सभी सिस्टम जुड़े रहते हैं; केबल टूटने पर नेटवर्क बंद.
2. Star Topology
Most used
Central device = Switch/Hub
Easy to manage
If central device fails → whole network down
Hindi: बीच में एक डिवाइस (Switch) से सब कंप्यूटर जुड़े.
3. Ring Topology
Circular connection
Token passing method
Failure of one system breaks network
Hindi: गोलाकार कनेक्शन; एक कंप्यूटर खराब → नेटवर्क खराब.
4. Mesh Topology
Every device connected to every other
Very reliable
Very expensive
Hindi: हर डिवाइस हर डिवाइस से कनेक्ट — सबसे सुरक्षित, लेकिन महंगा.
5. Hybrid Topology
Combination (e.g., Star + Bus).
⭐ 4. Networking Devices
1. Hub
Broadcast device
No intelligence
Works on Physical layer
Hindi: सबसे सामान्य, डेटा हर कंप्यूटर को भेजता है.
2. Switch
Smart device
Uses MAC address
Works on Data Link layer
Sends data to correct device
Hindi: केवल सही कंप्यूटर को डेटा भेजता है (स्मार्ट हब).
3. Router
Connects different networks
Uses IP address
Works on Network layer
Used to access the internet
Hindi: नेटवर्क को जोड़ने वाला; IP एड्रेस पर काम करता है.
4. Repeater
Boosts weak signals.
Hindi: सिग्नल को दोबारा मजबूत करता है.
5. Bridge
Connects two LAN segments.
Hindi: दो LAN को जोड़ता है.
6. Modem
Modulates + Demodulates signals (Analog ↔ Digital).
Hindi: टीवी केबल/टेलीफोन लाइन द्वारा इंटरनेट देता है.
⭐ 5. IP Addressing (Very Important)
IPv4
32-bit
Example: 192.168.1.1
Total addresses: 4.3 billion
IPv6
128-bit
Example: 2001:0db8:85a3…
Unlimited addresses (~340 undecillion)
Types of IP Address
Public
Private
Static
Dynamic
Private IP Ranges
Class A: 10.0.0.0 – 10.255.255.255
Class B: 172.16.0.0 – 172.31.255.255
Class C: 192.168.0.0 – 192.168.255.255
⭐ 6. Protocols
TCP – Transmission Control Protocol
Connection oriented
Reliable
Slow but accurate
UDP – User Datagram Protocol
Connectionless
Faster
Not guaranteed
Used in live streaming
HTTP / HTTPS
HyperText Transfer Protocol (secure version uses SSL)
FTP
File Transfer Protocol
SMTP / POP3 / IMAP
Email protocols
DNS
Converts Domain → IP
⭐ 7. OSI Model (Very Very Important)
Physical
Data Link
Network
Transport
Session
Presentation
Application
Mnemonic:
Please Do Not Throw Sausage Pizza Away
⭐ 8. Cyber Security Basics
Malware, Virus, Worm, Trojan
Phishing
Firewall
Encryption
Digital Signature
PYQ-Style Questions (EMRS/NVS/KVS)
PYQ 1:
Which of the following is connection-oriented?
A. TCP
B. UDP
C. FTP
D. HTTP
✔ Answer: A – TCP
PYQ 2:
In Ring topology, data travels in—
✔ One direction
PYQ 3:
Which layer is responsible for routing?
✔ Network Layer
PYQ 4:
The device that connects two different networks—
✔ Router
PYQ 5:
Which protocol is used for email sending?
✔ SMTP
11. Which topology has the highest fault tolerance?
A. Bus
B. Ring
C. Star
D. Mesh
✔ Answer: D – Mesh
EN: Every node is connected to every other; no single point failure.
HI: इसमें हर सिस्टम आपस में जुड़ा होता है—एक खराब होने से नेटवर्क नहीं रुकता।
12. Which cable type gives the highest speed?
A. Coaxial
B. Twisted pair
C. Fiber optic
D. Telephone cable
✔ Answer: C – Fiber optic
13. Which device works on the Network layer?
A. Switch
B. Hub
C. Bridge
D. Router
✔ Answer: D – Router
14. MAC address is of how many bits?
A. 16
B. 32
C. 48
D. 64
✔ Answer: C – 48 bits
15. Which protocol is used for secure web browsing?
A. HTTP
B. HTTPS
C. FTP
D. SMTP
✔ Answer: B – HTTPS
16. Which of the following is NOT a network topology?
A. Star
B. Bus
C. Tree
D. Fiber
✔ Answer: D – Fiber (It is a cable type)
17. IP address belongs to which layer?
A. Data Link
B. Network
C. Presentation
D. Application
✔ Answer: B – Network Layer
18. In which topology does token passing occur?
A. Ring
B. Star
C. Mesh
D. Bus
✔ Answer: A – Ring
19. What is the role of a firewall?
A. Store data
B. Detect virus
C. Block unauthorized access
D. Increase speed
✔ Answer: C
20. Which of the following is a wireless technology?
A. Wi-Fi
B. Bluetooth
C. NFC
D. All of the above
✔ Answer: D – All
21. Which IP class supports the highest number of hosts?
A. Class A
B. Class B
C. Class C
D. Class D
✔ Answer: A – Class A
22. The device used to connect LAN and WAN is—
✔ Router
23. SMTP is used for—
A. Sending email
B. Receiving email
C. File transfer
D. Web browsing
✔ Answer: A
24. FTP stands for—
✔ File Transfer Protocol
25. Which network is spread over a city?
✔ MAN
26. Which layer ensures end-to-end communication?
✔ Transport Layer
27. What does DNS do?
A. Converts IP to domain
B. Converts domain to IP
C. Sends emails
D. Encrypts data
✔ Answer: B
28. Which cable is immune to electromagnetic interference?
✔ Fiber optic cable
29. Which is NOT a wireless communication method?
A. Radio waves
B. Infrared
C. Coaxial cable
D. Bluetooth
✔ Answer: C – Coaxial cable
30. Which command is used to check network connectivity?
✔ ping
31. Which of the following provides the fastest data transmission?
A. Radio waves
B. Microwave
C. Fiber optics
D. Coaxial cable
✔ Answer: C
32. Which address is unique for every device?
A. IP
B. MAC
C. Gateway
D. Subnet
✔ Answer: B – MAC Address
33. Which layer performs encryption?
✔ Presentation layer
34. Which protocol is used for voice calls over the internet?
✔ VoIP (Voice over IP)
35. Which device reduces network congestion?
✔ Switch (because it sends data only to correct port)
36. Wi-Fi operates on which standard?
✔ IEEE 802.11
37. Bluetooth operates on—
✔ 2.4 GHz frequency
38. Which device separates a LAN into segments?
✔ Bridge
39. OSI model has how many layers?
✔ 7
40. TCP works at which layer?
✔ Transport layer
41. Which is NOT an email protocol?
A. SMTP
B. POP3
C. IMAP
D. FTP
✔ Answer: D – FTP
42. Which of the following is a private IP?
A. 192.0.2.1
B. 192.168.0.10
C. 11.1.1.1
D. 130.2.3.4
✔ Answer: B
43. Which protocol is used for secure file transfer?
✔ SFTP (Secure FTP)
44. Which of these uses packet switching?
✔ The Internet
45. What is the smallest unit of data?
✔ Bit
46. Which device connects different network architectures?
✔ Gateway
47. IPv6 address size is—
✔ 128 bits
48. Which protocol is used to assign IP automatically?
✔ DHCP
49. Which port does HTTP use?
✔ Port 80
50. Which port does HTTPS use?
✔ Port 443
PYQ 1. The device that connects two different networks is—
A. Hub
B. Switch
C. Router
D. Repeater
✔ Answer: C – Router
EN: Router uses IP addresses to connect networks.
HI: Router अलग-अलग नेटवर्क को IP एड्रेस के आधार पर जोड़ता है।
PYQ 2. Which layer is responsible for routing packets?
A. Data Link
B. Network
C. Transport
D. Application
✔ Answer: B – Network Layer
PYQ 3. Which topology uses a central device like a hub or switch?
✔ Star Topology
PYQ 4. Which protocol is used to send emails?
✔ SMTP
PYQ 5. Which cable has the lowest resistance to electromagnetic interference?
A. Fiber optic
B. Coaxial
C. Twisted pair
D. USB
✔ Answer: A – Fiber optic
PYQ 6. IP address belongs to which layer?
✔ Network Layer
PYQ 7. In Ring topology, data travels—
A. Both directions
B. One direction
C. Randomly
D. Depends on switch
✔ Answer: B – One direction
PYQ 8. Which protocol translates domain names to IP addresses?
✔ DNS
PYQ 9. What is the length of a MAC address?
✔ 48 bits
PYQ 10. Which device reduces network traffic by dividing collision domains?
✔ Switch
PYQ 11. Which protocol ensures reliable communication?
A. UDP
B. TCP
C. FTP
D. DHCP
✔ Answer: B – TCP
EN: TCP provides error checking and reliability.
HI: TCP भरोसेमंद डेटा ट्रांसफर देता है।
PYQ 12. Which network covers a small geographical area?
✔ LAN
PYQ 13. Which address is permanently assigned to the network card?
✔ MAC Address
PYQ 14. Which layer performs encryption?
✔ Presentation Layer
PYQ 15. Which protocol is used for file transfer?
✔ FTP
PYQ 16. Which device boosts weak signals in a network?
✔ Repeater
PYQ 17. IPv4 addresses are of length—
✔ 32 bits
PYQ 18. 192.168.1.1 belongs to which category?
A. Public IP
B. Private IP
C. Loopback
D. Class D
✔ Answer: B – Private IP
PYQ 19. Which topology is used in token ring networks?
✔ Ring
PYQ 20. Which wireless communication technology works at 2.4 GHz?
✔ Bluetooth
PYQ 21. OSI model has how many layers?
✔ Seven layers
PYQ 22. What is the main function of DHCP?
A. Assigning IP address
B. Sending packets
C. Blocking traffic
D. File transfer
✔ Answer: A – Assigning IP
PYQ 23. Which device works on the Data Link Layer?
✔ Switch
PYQ 24. The device that connects two LAN segments is—
✔ Bridge
PYQ 25. What is the default port number of HTTP?
✔ Port 80
PYQ 26. What is the default port number for HTTPS?
✔ Port 443
PYQ 27. A virtual private network (VPN) is used for—
A. Speed
B. Security
C. Bluetooth pairing
D. Bandwidth control
✔ Answer: B – Security
HI: VPN सुरक्षित एन्क्रिप्टेड कनेक्शन देता है।
PYQ 28. Which protocol is used to receive emails?
A. SMTP
B. POP3
C. HTTP
D. DNS
✔ Answer: B – POP3
PYQ 29. A device that converts digital signals into analog and vice versa—
✔ Modem
PYQ 30. Internet is an example of—
✔ WAN – Wide Area Network
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