Computer Networks: Concepts, Topologies, Signals and Media

Posted on Feb 10, 2026 in Computer Engineering

1. Introduction to Computer Networks (16 Marks)

Meaning of Computer Network

A computer network is a collection of two or more computers and devices connected together to share data, resources, and information using communication links.

Definition

A computer network is an arrangement of hardware and software that allows devices to communicate and exchange data.

Components of a Network

  1. Sender – Device that sends data
  2. Receiver – Device that receives data
  3. Transmission medium – Path for data (cable, air)
  4. Protocol – Set of communication rules
  5. Network devices – Router, switch, hub, modem

Objectives of Computer Network

  • Resource sharing
  • Fast communication
  • Cost reduction
  • Reliability
  • Scalability

Functions of a Network

  • Data sharing
  • File transfer
  • Internet access
  • Email communication
  • Online collaboration

Examples

  • Internet
  • Banking network
  • College computer lab
  • Mobile networks

2. Advantages and Disadvantages of Computer Network (16 Marks)

Advantages of Computer Network

  1. Resource Sharing – Printers, scanners, internet
  2. Data Sharing – Files can be shared easily
  3. Fast Communication – Email, chat, video calls
  4. Cost Saving – Hardware and software sharing
  5. Centralized data storage
  6. Remote access – work from anywhere
  7. Better security – central control
  8. Reliability – backup systems available
  9. Scalability – easy to expand network

Disadvantages of Computer Network

  1. High initial cost
  2. Virus and malware attacks
  3. Data theft and hacking
  4. Network failure issues
  5. Maintenance cost
  6. Dependency on server
  7. Complex network setup
  8. Privacy problems

3. Network Topologies (16 Marks)

Meaning

Network topology refers to the physical or logical structure of a network.

Types of Network Topologies

1. Bus Topology

All computers are connected to a single cable.

Advantages:

  • Simple structure
  • Low cost
  • Easy installation

Disadvantages:

  • Cable failure stops the whole network
  • Slow data transfer
  • Difficult troubleshooting

2. Star Topology

All computers are connected to a central hub or switch.

Advantages:

  • Easy to manage
  • High speed
  • Fault isolation is easy

Disadvantages:

  • Hub failure stops the network
  • More expensive

3. Ring Topology

Computers are connected in a circular manner.

Advantages:

  • No data collision
  • Equal access to all nodes

Disadvantages:

  • One system failure affects all
  • Difficult to reconfigure

4. Mesh Topology

Each computer is connected to every other computer.

Advantages:

  • Highly reliable
  • No data loss
  • High security

Disadvantages:

  • Very expensive
  • Difficult installation

5. Tree Topology

Combination of star and bus topology.

Advantages:

  • Easy expansion
  • Good management

Disadvantages:

  • Backbone failure affects entire network

4. Analog and Digital Signal (16 Marks)

Analog Signal

An analog signal is a continuous signal that varies smoothly over time.

Examples

  • Human voice
  • Radio signals
  • Temperature measurement

Characteristics

  • Continuous wave
  • Affected by noise
  • Less accurate

Digital Signal

A digital signal represents data using binary form (0 and 1).

Examples

  • Computer data
  • Mobile signals
  • Internet data

Characteristics

  • Discrete signal
  • Noise resistant
  • High accuracy

Difference Between Analog and Digital Signal

Analog SignalDigital Signal
ContinuousDiscrete
Affected by noiseLess noise
Less secureHighly secure
Low accuracyHigh accuracy

5. Analog and Digital Transmission (16 Marks)

Analog Transmission

Data is sent in the form of analog signals.

Characteristics

  • Continuous waveform
  • Used in radio and telephone
  • Noise affected

Digital Transmission

Data is sent in binary form (0 and 1).

Characteristics

  • High speed
  • Secure
  • Used in computers and the internet

Difference Between Analog and Digital Transmission

Analog TransmissionDigital Transmission
Uses analog signalsUses digital signals
Low securityHigh security
More noiseLess noise
Less reliableHighly reliable

6. Transmission Media (16 Marks)

Meaning

Transmission media is the communication path used to transfer data from the sender to the receiver.

Types of Transmission Media

A. Guided Media (Wired)

  1. Twisted Pair Cable
    • Used in LAN
    • Cheap and easy
    • Low speed
  2. Coaxial Cable
    • Used in cable TV
    • High bandwidth
  3. Optical Fiber Cable
    • Very high speed
    • Long distance
    • Expensive

B. Unguided Media (Wireless)

  • Radio waves
  • Microwaves
  • Infrared
  • Satellite

7. Network Categories (16 Marks)

Based on Area Coverage

  1. PAN (Personal Area Network)
    • Small area
    • Example: Bluetooth
  2. LAN (Local Area Network)
    • Small geographic area
    • Example: School, office
  3. MAN (Metropolitan Area Network)
    • City-level network
    • Example: Cable TV network
  4. WAN (Wide Area Network)
    • Covers large area
    • Example: Internet

8. Wireless Networks (16 Marks)

Meaning

A wireless network allows communication without physical cables.

Types of Wireless Networks

  1. Wi-Fi – Local wireless internet
  2. Bluetooth – Short-range data transfer
  3. Mobile Networks – 3G/4G/5G
  4. Satellite Networks

Advantages of Wireless Networks

  • Mobility
  • Easy installation
  • No wiring
  • Cost effective
  • Remote access

Disadvantages of Wireless Networks

  • Low security
  • Signal interference
  • Limited range
  • Speed fluctuations

Applications of Wireless Network

  • Smartphones
  • Laptops
  • Smart TVs
  • Online classes
  • Online banking