Computer Networks Previous Year Questions: Most Repeated Topics & Semester Exam Preparation Strategy
Previous year questions are useful in Computer Networks because the same core concepts often return in different forms. One paper may ask you to “Explain the OSI model”, another may ask “Write the functions of each OSI layer”, while another may ask you to compare OSI with TCP/IP. The wording changes, but the concept you need to prepare remains almost the same.
This page helps you study those recurring question patterns unit by unit. Instead of memorising one fixed answer, you will learn what the examiner can ask, what should be included in the answer, which diagrams or comparisons are useful, and which detailed chapter to revise if the topic is still weak.
Computer Networks Topics You Should Prepare First From Previous-Year Patterns
These are the concepts that deserve special attention during semester revision because they naturally generate definitions, differences, diagrams, working-based questions and long descriptive answers.
OSI Model
Seven layers, functions, services, encapsulation idea and comparison with TCP/IP.
Network Topologies
Bus, Star, Ring, Mesh, Tree and Hybrid with advantages and disadvantages.
Transmission Media
Guided vs Unguided media and Twisted Pair, Coaxial, Fibre, Radio and Microwave.
Switching
Circuit, Message and Packet Switching with comparisons.
ALOHA & MAC
Channel allocation, MAC functions, Pure ALOHA and Slotted ALOHA.
Sliding Window
Stop-and-Wait, Go-Back-N and Selective Repeat with window conditions.
Error Control
Parity, Checksum, CRC and Hamming Code theory and numericals.
Routing
Distance Vector, Link State and shortest-path concepts.
Congestion
Causes, effects, flow control difference and control techniques.
IPv4 & Subnetting
Packet format, classes, subnet masks, CIDR and fragmentation.
TCP
Segment format, handshake, termination, flow control and congestion window.
Cryptography
Symmetric, Asymmetric, Hashing and Digital Signatures.
Complete Computer Networks 37-Chapter Revision Map
Use these detailed chapters whenever a PYQ answer needs deeper revision.
Network Fundamentals, Architecture, OSI Model & Topology
1. Define a computer network and explain its goals and applications.
A computer network is a collection of interconnected computers and communication devices that can exchange data and share resources through communication links and protocols.
Main Goals
- Resource sharing: Sharing printers, storage, Internet connections and software.
- Communication: Email, messaging, voice communication and video meetings.
- Information sharing: Users can exchange files and access common information.
- Reliability: Alternative systems or paths can improve service availability.
- Remote access: Users can access resources from distant locations.
- Distributed processing: Work can be divided among different computers.
2. Explain network architecture and its importance.
Network architecture describes the overall structure of a computer network. It defines how hardware, software, protocols, communication layers and services work together.
Importance
- Provides organised communication.
- Separates networking functions.
- Improves scalability.
- Makes troubleshooting easier.
- Allows different protocols and devices to work together.
3. Explain the OSI model with a neat diagram and functions of all seven layers.
The OSI model divides network communication into seven logical layers. Each layer performs a specific set of functions and provides services to the layer above it.
Physical Layer
Transmits raw bits using electrical, optical or radio signals.
Data Link Layer
Performs framing, physical addressing, flow control and error control.
Network Layer
Provides logical addressing, routing and packet forwarding.
Transport Layer
Provides process-to-process delivery, segmentation, ports and connection management.
Session Layer
Establishes, manages and terminates communication sessions.
Presentation Layer
Handles data representation, translation and compression.
Application Layer
Provides network services to applications such as file transfer and email.
4. Explain Bus, Star, Ring, Mesh, Tree and Hybrid topology.
Network topology describes how devices and communication links are arranged.
- Bus: All devices share one backbone cable.
- Star: All devices connect to a central device.
- Ring: Devices form a circular communication path.
- Mesh: Devices have multiple direct links.
- Tree: Hierarchical combination of network branches.
- Hybrid: Combination of two or more topologies.
| Topology | Main Advantage | Main Limitation |
|---|---|---|
| Bus | Low cost | Backbone failure is critical |
| Star | Easy management | Central-device dependence |
| Ring | Organised access | Simple ring failure can disrupt network |
| Mesh | High reliability | High cost |
| Tree | Scalable hierarchy | Backbone dependencies |
| Hybrid | Flexible | Complex design |
5. Discuss important factors used in network topology design.
- Cost of links and devices.
- Reliability.
- Network delay.
- Expected traffic load.
- Scalability.
- Backbone capacity.
- Local access requirements.
- Fault tolerance.
A good topology design balances performance and reliability with practical cost.
Transmission Media, Switching, ISDN & Terminal Handling
6. Explain guided and unguided transmission media with examples.
Guided Media
Signals travel through a physical path.
- Twisted-pair cable.
- Coaxial cable.
- Optical fibre.
Unguided Media
Signals travel through free space.
- Radio waves.
- Microwave.
- Satellite communication.
| Point | Guided | Unguided |
|---|---|---|
| Path | Physical conductor | Free space |
| Mobility | Lower | Higher |
| Examples | Fibre, coaxial, twisted pair | Radio, microwave, satellite |
7. Compare Circuit Switching, Message Switching and Packet Switching.
Circuit Switching
A dedicated path is created before communication.
Message Switching
The complete message is stored and forwarded by intermediate nodes.
Packet Switching
The message is divided into smaller packets that share network links.
8. Explain ISDN architecture, channels and services.
ISDN stands for Integrated Services Digital Network and was designed to carry voice and data using digital communication.
- B Channel: Carries user voice or data.
- D Channel: Mainly carries signalling information.
- H Channel: Provides higher-capacity services.
9. Write a note on terminal handling and its functions.
- Input handling.
- Buffering.
- Echoing.
- Flow control.
- Polling.
- Selection.
- Terminal emulation.
MAC Sublayer, Channel Allocation, ALOHA, LAN & IEEE Standards
10. Explain the functions of the MAC sublayer and multiple-access control.
- Controls access to a shared medium.
- Uses MAC addresses.
- Supports local frame transmission.
- Coordinates devices competing for the same channel.
- Supports medium-specific collision or access mechanisms.
11. Differentiate between static and dynamic channel allocation.
Static allocation divides channel capacity in advance, while dynamic allocation assigns access according to current traffic demand.
Dynamic allocation is more flexible for bursty computer traffic because capacity does not need to remain permanently assigned to an inactive user.
12. Explain important LAN protocols and their role.
LAN protocols define how devices communicate over a local network. They deal with frame transmission, addressing and access to the communication medium.
A good answer should connect LAN protocols with Ethernet, wireless LAN technologies and MAC-layer operation.
13. Explain Pure ALOHA and Slotted ALOHA. Compare their operation.
Pure ALOHA
- A station transmits whenever data becomes available.
- Frames can overlap and collide.
- After collision, retransmission occurs after a random delay.
Slotted ALOHA
- Time is divided into fixed slots.
- Transmission begins only at a slot boundary.
- Collision opportunity is reduced.
- Efficiency is better than Pure ALOHA.
14. Explain IEEE 802.3 and IEEE 802.11.
IEEE 802.3 is associated with Ethernet and wired LAN technologies.
IEEE 802.11 defines wireless LAN technologies commonly known as Wi-Fi.
A good semester answer should mention communication medium, network type and basic use of each standard.
15. Explain FDDI architecture and working.
FDDI stands for Fiber Distributed Data Interface. It traditionally uses optical fibre and a dual-ring structure.
- Token-based access.
- Primary and secondary ring.
- High reliability.
- Secondary ring can improve fault tolerance.
Data Link Layer, Sliding Window & Error Control
16. Explain the functions of the Data Link Layer.
- Framing.
- Physical addressing.
- Flow control.
- Error control.
- Medium-access control.
- Node-to-node delivery.
17. Explain elementary Data Link protocols and Stop-and-Wait communication.
Elementary Data Link protocols are simplified models used to understand reliable communication.
- Simplex unrestricted protocol.
- Simplex Stop-and-Wait.
- Noisy-channel communication with acknowledgement and retransmission.
18. Compare Stop-and-Wait ARQ, Go-Back-N and Selective Repeat.
Stop-and-Wait
Only one frame is sent before waiting for acknowledgement.
Go-Back-N
Several frames can remain outstanding. If a frame is missing, that frame and later outstanding frames may be retransmitted.
Selective Repeat
Only missing or damaged frames are retransmitted. The receiver can buffer out-of-order frames.
Classical Go-Back-N sender window: W ≤ 2m - 1
Common Selective Repeat window: W ≤ 2(m-1)
19. Explain Parity, Checksum, CRC and Hamming Code.
- Parity: Adds one parity bit for simple error detection.
- Checksum: Calculates a value from groups of data words.
- CRC: Uses modulo-2 division and a generator polynomial.
- Hamming Code: Uses redundant parity bits and can correct a single-bit error in its basic form.
For Hamming Code: 2r ≥ m + r + 1
Network Layer, Routing, Congestion, IPv4, IPv6 & Internetworking
20. Explain the functions and design issues of the Network Layer.
- Logical addressing.
- Routing.
- Packet forwarding.
- Internetworking.
- Handling packet-size limitations.
- Traffic and congestion considerations.
21. Explain PPP and Point-to-Point communication.
PPP stands for Point-to-Point Protocol. It supports direct communication between two nodes.
- Link establishment.
- Frame encapsulation.
- Error detection.
- Authentication support.
- Support for multiple Network Layer protocols.
22. Compare Distance Vector and Link State routing algorithms.
| Point | Distance Vector | Link State |
|---|---|---|
| Network knowledge | Distance and next-hop information | Topology database |
| Information exchange | Mainly neighbouring routers | Link-state information distributed |
| Complexity | Lower | Higher |
| Convergence | Can be slower | Often faster |
| Common issue | Routing loops/count-to-infinity in basic forms | Higher processing and memory requirements |
23. What is congestion? Explain its causes, effects and control methods.
Congestion occurs when offered network traffic becomes greater than the resources available to handle that traffic.
Causes
- Traffic bursts.
- Limited bandwidth.
- Router-buffer limitations.
- Slow packet processing.
- Excessive retransmissions.
Effects
- High delay.
- Packet loss.
- Lower useful throughput.
- More retransmissions.
Control
- Traffic shaping.
- Admission control.
- Queue management.
- Feedback mechanisms.
- Sender-rate control.
24. Explain routers, gateways, tunneling and fragmentation in internetworking.
Internetworking connects separate networks so that devices can communicate across network boundaries.
- Router: Forwards packets between IP networks.
- Gateway: Can connect dissimilar systems and perform translation.
- Tunneling: Encapsulates one packet inside another protocol.
- Fragmentation: Divides an oversized datagram into smaller fragments.
25. Explain the TCP/IP model and compare it with the OSI model.
The TCP/IP model is commonly represented with four layers:
- Application.
- Transport.
- Internet.
- Network Access.
26. Draw and explain the IPv4 datagram header.
Important fields include Version, Header Length, Total Length, Identification, Flags, Fragment Offset, TTL, Protocol, Checksum, Source Address and Destination Address.
27. Explain subnetting and CIDR with a suitable example.
Subnetting divides a large IP network into smaller logical subnetworks.
Consider: 192.168.10.0/24
Using a /26 prefix creates four blocks:
- 192.168.10.0/26
- 192.168.10.64/26
- 192.168.10.128/26
- 192.168.10.192/26
Each block contains 64 total addresses and traditionally 62 normal usable host addresses.
CIDR uses prefix lengths such as /24 or /26 instead of depending only on fixed address classes.
28. Explain IPv6 and differentiate IPv4 and IPv6.
- IPv4 address size: 32 bits.
- IPv6 address size: 128 bits.
- IPv4 uses dotted decimal notation.
- IPv6 uses hexadecimal groups.
- IPv6 provides a much larger address space.
- IPv6 uses a simplified base header.
- IPv6 does not use traditional IPv4-style broadcast.
Transport Layer, TCP, UDP & Window Management
29. Explain the functions and design issues of the Transport Layer.
- Process-to-process delivery.
- Port addressing.
- Segmentation and reassembly.
- Multiplexing and demultiplexing.
- Connection management.
- Flow control.
- Error recovery in reliable transport.
30. Explain TCP segment format and three-way handshake.
Important TCP header fields include Source Port, Destination Port, Sequence Number, Acknowledgement Number, Flags, Window Size and Checksum.
The handshake confirms that both endpoints are ready and synchronizes connection information.
31. Explain TCP flow control, sliding window and congestion window.
TCP controls how much data can remain in transit before acknowledgement.
- Receiver Window: Reflects available receiver-buffer space and supports flow control.
- Congestion Window: Reflects network congestion conditions.
- Sliding Window: Allows multiple bytes to remain unacknowledged while controlling the sending range.
Session Layer, RPC, Presentation Layer & Cryptography
32. Explain Session Layer functions and synchronization.
- Session establishment.
- Session maintenance.
- Session termination.
- Dialogue control.
- Synchronization.
- Checkpoint management.
Checkpoints can allow a long operation to restart from a suitable point instead of beginning again from the start.
33. Explain Remote Procedure Call architecture and working.
- Client calls a local stub.
- Arguments are packaged.
- Request travels to the server.
- Server stub receives the request.
- Remote procedure executes.
- Result returns to the client.
34. Explain Presentation Layer functions and data compression.
- Data representation.
- Format translation.
- Character-code conversion.
- Compression.
- Other presentation-related transformations.
Compression reduces the amount of data that must be stored or transmitted.
35. Explain symmetric encryption, asymmetric encryption, hashing and digital signatures.
Symmetric Encryption
Uses the same secret key for encryption and decryption.
Asymmetric Encryption
Uses a public and private key pair.
Hashing
Converts data into a fixed-size digest using a one-way function.
Digital Signature
Uses asymmetric cryptographic mechanisms to support authenticity, integrity and non-repudiation-related security goals.
Application Layer, FTP, Email & Internet
36. Explain Application Layer services such as FTP, Email and Virtual Terminal.
The Application Layer provides network services directly to user applications.
FTP
File Transfer Protocol supports file-transfer operations between network systems.
Email systems use application protocols for sending, relaying and retrieving electronic messages.
Virtual Terminal
Virtual-terminal services allow users to interact with remote systems through a network.
Other Services
- Web access.
- Naming services.
- Directory services.
- Remote communication.
37. Explain the architecture and working of the Internet and public networks.
The Internet is a global internetwork created by connecting a very large number of independently managed networks.
Main Components
- Hosts.
- Routers.
- Communication links.
- Internet service providers.
- Servers.
- IP addressing.
- Routing protocols.
- Application services.
Basic Working
- An application generates data.
- Transport Layer prepares process-to-process communication.
- IP provides logical addressing.
- Routers forward packets through different networks.
- The destination system receives the packets.
- The destination application processes the information.
Extra Previous-Year Question Variations You Should Practise
Examiners often change the wording of a familiar topic. Practising these variations prevents you from depending on one memorised question.
38. Differentiate between flow control and congestion control.
| Flow Control | Congestion Control |
|---|---|
| Protects receiver | Protects network |
| Matches sender rate with receiver capacity | Matches traffic with network capacity |
| Receiver window is important in TCP | Congestion window is important in TCP |
39. Differentiate between TCP and UDP.
| TCP | UDP |
|---|---|
| Connection-oriented | Connectionless |
| Reliable delivery mechanisms | No built-in reliable delivery |
| Ordered byte stream | Datagram based |
| Higher overhead | Lower overhead |
40. Differentiate between IPv4 and IPv6.
| IPv4 | IPv6 |
|---|---|
| 32-bit address | 128-bit address |
| Dotted decimal notation | Hexadecimal notation |
| Smaller address space | Extremely large address space |
| Supports broadcast | No traditional IPv4-style broadcast |
| More variable base header | Simplified fixed-size base header |
41. Differentiate between symmetric and asymmetric cryptography.
| Symmetric | Asymmetric |
|---|---|
| Shared secret key | Public/private key pair |
| Generally faster for bulk encryption | Generally more computationally intensive |
| Secure key sharing is an important challenge | Public key can be distributed openly |
42. Why is the OSI model still important when the Internet uses TCP/IP?
The OSI model is useful as a conceptual reference. It clearly separates networking responsibilities into seven layers, making learning, protocol comparison and troubleshooting easier.
TCP/IP, on the other hand, represents the practical protocol architecture used by the Internet.
43. Why is packet switching suitable for computer networks?
- Communication links can be shared.
- Resources do not need to remain reserved when users are idle.
- It handles bursty traffic efficiently.
- Packets can be independently forwarded.
- It supports large numbers of communicating users.
44. Why is Selective Repeat more efficient than Go-Back-N in some situations?
Selective Repeat retransmits only missing or damaged frames, while Go-Back-N may retransmit multiple later frames even if some were originally transmitted correctly.
The improvement comes at the cost of more receiver buffering and control complexity.
45. Why is IPv6 needed?
The main motivation for IPv6 is the limited IPv4 address space.
IPv6 provides 128-bit addresses, giving a vastly larger addressing capacity and supporting continued Internet growth.
46. Explain the difference between a router and a gateway.
A router primarily forwards packets between IP networks using routing information.
A gateway is a broader term and may connect systems that require protocol, format or application-level translation.
47. Explain the difference between error detection and error correction.
Error detection identifies whether transmitted data has been corrupted.
Error correction provides enough information to locate and repair an error without necessarily retransmitting the original data.
CRC is mainly an error-detection method, while basic Hamming Code can perform single-bit error correction.
48. What is the role of sequence numbers and acknowledgements in TCP?
Sequence numbers identify positions of bytes in the TCP stream.
Acknowledgement numbers tell the sender which byte the receiver expects next.
Together they help TCP provide ordered and reliable data delivery.
49. Explain fragmentation and MTU.
MTU stands for Maximum Transmission Unit and represents the largest packet size that a network link can carry without fragmentation.
When an IPv4 datagram is larger than the permitted MTU and fragmentation is allowed, the datagram can be divided into smaller fragments.
50. Explain encapsulation in layered network communication.
During encapsulation, every networking layer adds its own control information to the data received from the layer above.
At the destination, the headers are processed in reverse order. This process is called decapsulation.
Computer Networks Semester Exam Preparation Strategy Using PYQs
Previous-year questions work best when you use them to find weak concepts instead of memorising only one fixed answer.
Build the Base
First revise OSI, topology, transmission media, Data Link Layer, Network Layer and Transport Layer. These topics connect with most of the remaining syllabus.
Practise Differences
Prepare OSI vs TCP/IP, IPv4 vs IPv6, TCP vs UDP, Guided vs Unguided, Go-Back-N vs Selective Repeat and Symmetric vs Asymmetric.
Practise Diagrams
Draw OSI layers, IPv4 header, TCP handshake, RPC flow and basic network-topology diagrams without looking at notes.
Do Numericals
Practise subnetting, Hamming Code, CRC and sliding-window numerical relationships separately from theory answers.
How to Write Previous-Year Answers According to Marks
2 Marks
Write a direct definition and one key feature, purpose or example. Usually 3–5 meaningful lines are enough.
5 Marks
Start with the definition and explain around 4–6 strong points. Add a small comparison or diagram if the question requires it.
10 Marks
Use introduction, headings, working, diagram, important points, advantages or limitations, comparison where useful and a short conclusion.
Final PYQ Revision Checklist
Before the exam, you should be able to explain the OSI model, draw major network diagrams, compare important protocols, solve basic error-control and subnetting questions, explain routing and congestion, draw the TCP handshake and describe major security and Application Layer concepts without opening your notes.
Do not memorise one previous-year answer word for word. Universities often ask the same concept with a different command such as define, explain, compare, discuss, draw or analyse. Understanding the complete concept allows you to answer all of these variations.
Whenever a PYQ topic still feels weak, use the linked detailed chapter above. This keeps your revision focused instead of reading all 37 chapters again before every exam.
