DCN MCQ QUESTIONS
### ✅ **Unit I: Fundamentals of Data Communication (20 MCQs)**
1. **What is Data Communication?**
A) Storing data
B) Displaying data
C) Transferring data from one device to another
D) Encrypting data
**Answer: C**
2. **Which of the following is NOT a component of data communication?**
A) Message
B) Sender
C) Cable
D) Browser
**Answer: D**
3. **Which data flow mode allows transmission in both directions simultaneously?**
A) Simplex
B) Half Duplex
C) Full Duplex
D) None
**Answer: C**
4. **Which type of network topology connects every device to every other device?**
A) Star
B) Ring
C) Mesh
D) Bus
**Answer: C**
5. **Which is an example of LAN?**
A) Internet
B) Office network
C) Telephone system
D) Satellite system
**Answer: B**
6. **The term 'Throughput' refers to:**
A) Security level
B) Number of bits sent in a second
C) Distance between devices
D) Cable quality
**Answer: B**
7. **Which one is NOT a type of network connection?**
A) Point-to-Point
B) Multipoint
C) Ring
D) Mesh
**Answer: D**
8. **Which topology has a central hub?**
A) Ring
B) Bus
C) Mesh
D) Star
**Answer: D**
9. **Which device is considered as both sender and receiver?**
A) Transceiver
B) Repeater
C) Hub
D) Switch
**Answer: A**
10. **Which is not part of ISO-OSI Model?**
A) Application
B) Transport
C) Firewall
D) Session
**Answer: C**
11. **How many layers are in the OSI model?**
A) 5
B) 6
C) 7
D) 4
**Answer: C**
12. **In the OSI model, routing is done at:**
A) Physical layer
B) Data link layer
C) Network layer
D) Application layer
**Answer: C**
13. **Which model has only 4 layers?**
A) OSI
B) TCP/IP
C) Both A and B
D) None
**Answer: B**
14. **TCP/IP is a \_\_\_\_\_\_ architecture.**
A) Theoretical
B) Practical
C) Experimental
D) Obsolete
**Answer: B**
15. **Which layer is responsible for encryption and decryption in OSI model?**
A) Session
B) Transport
C) Presentation
D) Network
**Answer: C**
16. **LAN stands for:**
A) Long Area Network
B) Local Access Network
C) Local Area Network
D) Large Area Network
**Answer: C**
17. **A network that covers a city is called:**
A) LAN
B) WAN
C) MAN
D) PAN
**Answer: C**
18. **Which of these is a type of data representation?**
A) Distance
B) Image
C) Temperature
D) Speed
**Answer: B**
19. **Which of these is NOT a network topology?**
A) Mesh
B) Tree
C) Chain
D) Bus
**Answer: C**
20. **Full Duplex communication means:**
A) One way only
B) Alternating turns
C) Simultaneous both ways
D) No communication
**Answer: C**
### ✅ **Unit II: PHYSICAL LAYER (20 MCQs)**
1. **What is Multiplexing?**
A) Data storage
B) Combining signals for transmission
C) Breaking messages
D) Encrypting messages
**Answer: B**
2. **FDM stands for:**
A) Frequency Distribution Multiplexing
B) Frequency Domain Management
C) Frequency Division Multiplexing
D) Frame Data Multiplexing
**Answer: C**
3. **Which multiplexing uses different colors of light?**
A) FDM
B) TDM
C) WDM
D) CDMA
**Answer: C**
4. **TDM is based on:**
A) Amplitude
B) Frequency
C) Time slots
D) Distance
**Answer: C**
5. **Which is not a guided media?**
A) Twisted Pair
B) Coaxial Cable
C) Fiber Optic
D) Microwave
**Answer: D**
6. **RJ-45 is commonly used with:**
A) Coaxial cables
B) Fiber cables
C) UTP cables
D) Optical switches
**Answer: C**
7. **Which cable has BNC connectors?**
A) Fiber-optic
B) UTP
C) STP
D) Coaxial
**Answer: D**
8. **Which cable offers highest bandwidth?**
A) Twisted pair
B) Coaxial
C) Fiber-optic
D) Parallel cable
**Answer: C**
9. **Which connector is used in fiber-optic cables?**
A) RJ-11
B) SC
C) BNC
D) D-Sub
**Answer: B**
10. **Which is NOT a fiber-optic connector?**
A) SC
B) ST
C) RJ-45
D) LC
**Answer: C**
11. **Microwaves are:**
A) Used for underwater communication
B) A type of guided media
C) A type of wireless media
D) Always used in LAN
**Answer: C**
12. **Infrared is used in:**
A) Underwater cables
B) TV remotes
C) Fiber cables
D) LAN cables
**Answer: B**
13. **Which media is used in satellites?**
A) Twisted pair
B) Fiber
C) Microwave
D) Coaxial
**Answer: C**
14. **Which media is immune to electromagnetic interference?**
A) Coaxial
B) Fiber-optic
C) UTP
D) STP
**Answer: B**
15. **Which media is most cost-effective?**
A) Fiber-optic
B) Microwave
C) Coaxial
D) UTP
**Answer: D**
16. **Circuit switching is used in:**
A) Internet
B) Email
C) Telephone networks
D) VoIP
**Answer: C**
17. **In packet-switched networks, data is sent in:**
A) Circuits
B) Streams
C) Packets
D) Cables
**Answer: C**
18. **Datagram approach is associated with:**
A) Circuit switching
B) TDM
C) Packet switching
D) FDM
**Answer: C**
19. **Virtual circuit networks are a feature of:**
A) Circuit switching
B) Packet switching
C) Hybrid networks
D) Bus networks
**Answer: B**
20. **Unguided media includes all except:**
A) Radio wave
B) Microwave
C) Twisted pair
D) Infrared
**Answer: C**
---
### ✅ **Unit III: DATA LINK LAYER (20 MCQs)**
1. **What is framing in data link layer?**
A) Breaking the cable
B) Arranging devices
C) Dividing stream into frames
D) Encrypting data
**Answer: C**
2. **Which is not a type of framing?**
A) Fixed size
B) Variable size
C) Dynamic size
D) Byte stuffing
**Answer: C**
3. **What is the purpose of flow control?**
A) Increase errors
B) Improve security
C) Match sender and receiver speeds
D) Break transmission
**Answer: C**
4. **Stop-and-wait protocol is used for:**
A) Circuit switching
B) Flow control
C) Frequency control
D) Multiplexing
**Answer: B**
5. **Which protocol handles noisy channels with retransmission?**
A) Stop-and-Wait ARQ
B) Go-Back-N
C) Selective Repeat
D) All of the above
**Answer: D**
6. **In Go-Back-N ARQ, if error is found:**
A) Only that frame is resent
B) All frames from error are resent
C) All previous frames are resent
D) No frame is resent
**Answer: B**
7. **Which ARQ protocol is most efficient?**
A) Stop-and-Wait ARQ
B) Go-Back-N
C) Selective Repeat
D) FDM
**Answer: C**
8. **Which is an error-detection technique?**
A) Parity check
B) CRC
C) Checksum
D) All
**Answer: D**
9. **Which of these is an error-correcting code?**
A) Hamming code
B) CRC
C) Parity
D) Bit stuffing
**Answer: A**
10. **Which protocol sends multiple frames before waiting for ACK?**
A) Stop-and-Wait
B) Go-Back-N
C) TDM
D) CRC
**Answer: B**
11. **Which protocol handles lost or corrupted frames efficiently?**
A) Selective Repeat
B) Go-Back-N
C) Stop-and-Wait
D) FDM
**Answer: A**
12. **ARQ stands for:**
A) Automatic Response Query
B) Automatic Repeat Query
C) Analog Repeat Query
D) Advanced Repeat Quality
**Answer: B**
13. **Which layer is responsible for error detection?**
A) Transport
B) Network
C) Data Link
D) Application
**Answer: C**
14. **Bit stuffing is used in:**
A) Framing
B) Flow control
C) Error detection
D) Transmission media
**Answer: A**
15. **Framing helps in:**
A) Addressing
B) Identifying message boundaries
C) Security
D) DNS resolution
**Answer: B**
16. **Fixed-size frames are easier to:**
A) Process
B) Encrypt
C) Route
D) Compress
**Answer: A**
17. **Which protocol uses a sliding window concept?**
A) Go-Back-N
B) Selective Repeat
C) Both A & B
D) Stop-and-Wait
**Answer: C**
18. **In which protocol is ACK required for every frame?**
A) Go-Back-N
B) Selective Repeat
C) Stop-and-Wait
D) TDM
**Answer: C**
19. **Which error occurs due to extra or missing bits?**
A) Burst error
B) Single-bit error
C) Redundancy
D) Hamming
**Answer: A**
20. **Which of these is NOT used for error detection?**
A) CRC
B) Parity
C) Hamming
D) Checksum
**Answer: C**
### ✅ **Unit IV: NETWORK LAYER (20 MCQs)**
1. **Which device operates at the network layer?**
A) Hub
B) Switch
C) Router
D) Repeater
**Answer: C**
2. **Which device is used to connect different networks with different protocols?**
A) Switch
B) Hub
C) Bridge
D) Gateway
**Answer: D**
3. **Which addressing format is used in IPv4?**
A) Hexadecimal
B) Octal
C) Dot-decimal
D) Binary
**Answer: C**
4. **Which class of IP address has a default subnet mask of 255.255.255.0?**
A) Class A
B) Class B
C) Class C
D) Class D
**Answer: C**
5. **What is the main reason for moving to IPv6?**
A) Faster speeds
B) Security
C) More address space
D) Simpler headers
**Answer: C**
6. **IPv6 uses how many bits for addressing?**
A) 32
B) 64
C) 128
D) 256
**Answer: C**
7. **Which of the following is NOT an IPv4 class?**
A) Class A
B) Class B
C) Class D
D) Class F
**Answer: D**
8. **Which protocol resolves IP address to MAC address?**
A) ICMP
B) ARP
C) RARP
D) DNS
**Answer: B**
9. **Which protocol helps assign IP addresses to devices without manual configuration?**
A) ARP
B) ICMP
C) DHCP
D) FTP
**Answer: C**
10. **What is IGMP used for?**
A) Address translation
B) Email transfer
C) Managing group memberships
D) File transfer
**Answer: C**
11. **ICMP is used for:**
A) Sending files
B) Error reporting and diagnostics
C) Encrypting data
D) Domain name resolution
**Answer: B**
12. **What is the function of a bridge?**
A) Connects different networks
B) Connects similar networks
C) Converts analog to digital
D) Encrypts messages
**Answer: B**
13. **A switch operates at which OSI layer?**
A) Network
B) Data Link
C) Physical
D) Transport
**Answer: B**
14. **Which IP address class supports 16 million hosts?**
A) Class A
B) Class B
C) Class C
D) Class D
**Answer: A**
15. **A static IP address is:**
A) Changed frequently
B) Assigned temporarily
C) Fixed and manually configured
D) Invalid
**Answer: C**
16. **RARP is used to:**
A) Translate MAC to IP
B) Translate IP to MAC
C) Encrypt data
D) Route data
**Answer: A**
17. **Subnetting helps to:**
A) Combine networks
B) Divide large networks into smaller ones
C) Encrypt data
D) Convert analog to digital
**Answer: B**
18. **Which address is assigned dynamically?**
A) Static IP
B) Loopback IP
C) Dynamic IP
D) Broadcast IP
**Answer: C**
19. **Which protocol is used to find MAC address from IP?**
A) ICMP
B) RARP
C) ARP
D) DNS
**Answer: C**
20. **A router uses which addressing scheme?**
A) Physical
B) Logical
C) Symbolic
D) Manual
**Answer: B**
---
### ✅ **Unit V: TRANSPORT LAYER, APPLICATION LAYER & NETWORK SECURITY (20 MCQs)**
1. **Which protocol provides reliable connection-oriented service?**
A) UDP
B) IP
C) TCP
D) FTP
**Answer: C**
2. **Which protocol is used for fast, connectionless communication?**
A) FTP
B) TCP
C) UDP
D) ICMP
**Answer: C**
3. **The TCP segment header includes:**
A) Source & destination ports
B) MAC address
C) IP address
D) URL
**Answer: A**
4. **Which transport protocol is best for video streaming?**
A) TCP
B) UDP
C) FTP
D) ICMP
**Answer: B**
5. **Which of the following uses port 80?**
A) FTP
B) DNS
C) HTTP
D) SMTP
**Answer: C**
6. **Which protocol is used to send emails?**
A) SMTP
B) FTP
C) HTTP
D) DHCP
**Answer: A**
7. **Which protocol helps in file transfer?**
A) FTP
B) HTTP
C) SMTP
D) ICMP
**Answer: A**
8. **DNS is used for:**
A) Encrypting data
B) Converting IP to hostname
C) Mapping domain names to IP
D) Managing FTP connections
**Answer: C**
9. **WWW stands for:**
A) Wide World Web
B) Web With Wire
C) World Wide Web
D) Web World Work
**Answer: C**
10. **Which layer is responsible for end-to-end delivery?**
A) Network
B) Data Link
C) Application
D) Transport
**Answer: D**
11. **TCP provides:**
A) No guarantee of delivery
B) Only encryption
C) Reliable byte stream
D) Broadcast only
**Answer: C**
12. **UDP is mainly used in:**
A) File Transfer
B) Email
C) Streaming
D) Database
**Answer: C**
13. **What is the primary goal of network security?**
A) Increase bandwidth
B) Reduce latency
C) Protect data
D) Build cables
**Answer: C**
14. **Which of the following is used for encryption?**
A) ICMP
B) FTP
C) DNS
D) AES
**Answer: D**
15. **Decryption is the process of:**
A) Encrypting again
B) Encoding data
C) Converting ciphertext to plaintext
D) Sending mail
**Answer: C**
16. **Which of these is NOT an application layer protocol?**
A) HTTP
B) SMTP
C) DNS
D) TCP
**Answer: D**
17. **Which one is NOT a transport layer protocol?**
A) TCP
B) UDP
C) IP
D) SCTP
**Answer: C**
18. **Which is a feature of TCP but not of UDP?**
A) Speed
B) Reliability
C) Connectionless
D) Broadcast
**Answer: B**
19. **Which protocol uses 3-way handshake?**
A) UDP
B) ICMP
C) TCP
D) FTP
**Answer: C**
20. **Application layer works closest to the:**
A) Hardware
B) Operating system
C) User
D) Transport layer
**Answer: C**
Data Communication and Networking
Unit I FUNDAMENTALS OF DATA COMMUNICATION
Data Communication: Definition of Data and Data communication, Components of Data Communication, Data Representation (Text, Image, Numbers, Audio, Video), Data Flow (Simplex, Half Duplex, Full Duplex)
Network: Network Criteria: Performance (Throughput and Delay), Reliability, Security -Types of Network Connections (Point-to-Point and Multipoint) - Network Topologies: Star, Bus, Ring, Mesh - Network Categories (LAN, MAN, WAN) and Interconnection of networks
Network Architecture: Layered Approach : ISO-OSI Model & TCP/IP Model – functions of each layer
Unit II PHYSICAL LAYER
Multiplexing: Definition of Mulitplexing - Frequency Division Multiplexing (FDM),Wavelength Division Multiplexing (WDM), Synchronous Time-Division Multiplexing (TDM)
Transmission media: Guided Media: Twisted pair – UTP and connectors (RJ-45 Male and Female connectors), STP cables, Coaxial cable and connectors (BNC connector), Fiber-optic cables, cable sizes and connectors (SC, MT-RJ, ST, LC, FC) - Performance, and applications of UTP, Coaxial and Fiber-Optic cables - Unguided Media (Wireless Media): Radio waves, Microwaves, Infrared and their applications
Switching: Circuit-Switched Network, Packet Switched Network (Datagram approach), Virtual Circuit network
Unit III DATA LINK LAYER
Framing of data: Definition, Types: Fixed Size and Variable Size framing– Flow and Error control
Flow Control: Noiseless Channel: Definition, Stop and Wait protocol – Concepts and Flow Diagram - Noisy Channel: Definition, Stop-and-Wait ARQ protocol, Go-Back–N ARQ Protocol, Selective Repeat ARQ Protocol - Concepts and Flow Diagram only
Error Control: Concepts of Error Detection and Error Correction – types of error detecting and error correcting codes (definition only)
Unit IV NETWORK LAYER
Network Devices: Hub, Switch, Router, Bridge, Gateway (definition only)
Logical addressing: IP Addressing: Dot-Decimal Notation of IPv4 – Classful and Classless addressing – IPv4 datagram format - Basics of IPv6 - Need for transition from IPv4 to IPv6 – IPv6 datagram format - Subnetting (only definition and subnet masks for each IP class) – Static IP and Dynamic IP: Definition and applications
Network Layer Protocols: IGMP, ICMP, ARP, RARP (definitions and functions only)
Unit V TRANSPORT LAYER, APPLICATION LAYER AND NETWORK SECURITY
Transport Layer: Connection-oriented and Connectionless Services - TCP Features - TCP segment format - User datagram format (UDP packet)
Application Layer: Concepts of DNS – SMTP – FTP - HTTP – WWW (World Wide Web)
Network Security: Data Encryption and Decryption
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