Computer Networks – Basic 6 Basic Technology Lesson Note (Second Term)

Learning Objectives

By the end of the lesson, pupils should be able to:

1. Define LAN and WAN
2. Define network technology
3. Outline types of network topology

Content

What is a Computer Network?

Definition: A computer network is a group of two or more computers and devices connected together to share resources, exchange data, and communicate.

Purpose of Networks:

• Share files and data
• Share hardware (printers, scanners)
• Communicate (email, messaging)
• Share internet connection
• Centralize data storage
• Collaborate on projects
• Access remote resources

Types of Networks by Size/Scope

1. LAN (Local Area Network)

Definition: A network that connects computers and devices within a limited area such as a home, school, office building, or small group of buildings.

Characteristics:

• Coverage: Small geographic area (single building or campus)
• Ownership: Usually owned by one organization
• Speed: High data transfer rates (100 Mbps – 10 Gbps)
• Cost: Relatively low setup and maintenance
• Connection: Ethernet cables or Wi-Fi
• Examples: School computer lab, home network, office network

Advantages of LAN:

• Fast data transfer
• Easy resource sharing
• Low cost
• Easy to manage
• High security control
• Reliable

Disadvantages of LAN:

• Limited geographic coverage
• Limited number of users
• Requires maintenance
• Initial setup cost

Components of LAN:

1. Computers/Workstations
2. Network Interface Cards (NICs)
3. Cables (Ethernet) or Wireless Access Points
4. Switch/Hub (connects devices)
5. Router (connects to internet)
6. Server (optional – for file/print sharing)

2. WAN (Wide Area Network)

Definition: A network that covers a large geographic area, often spanning cities, countries, or even continents, connecting multiple LANs together.

Characteristics:

• Coverage: Large geographic area (cities, countries, world)
• Ownership: Often uses third-party telecommunications
• Speed: Variable (slower than LAN generally)
• Cost: Expensive to setup and maintain
• Connection: Telephone lines, fiber optics, satellites, microwave
• Examples: Internet, corporate networks, banking networks

Advantages of WAN:

• Covers large distances
• Connects multiple locations
• Centralized data access
• Enables remote work
• Shares resources globally
• Facilitates communication

Disadvantages of WAN:

• Expensive
• Complex to manage
• Security risks
• Slower than LAN
• Dependent on service providers
• Requires skilled technicians

Comparison: LAN vs WAN

Other Network Types (Brief Overview)

MAN (Metropolitan Area Network):

• Covers a city or large campus
• Between LAN and WAN in size
• Example: City-wide Wi-Fi, cable TV network

PAN (Personal Area Network):

• Very small range (few meters)
• Personal devices
• Example: Bluetooth connections, smartphone to laptop

Network Topology

Definition: Network topology refers to the physical or logical arrangement of devices (nodes) and connections in a network.

Types of Network Topology:

1. Bus topology

Description:

• All devices connected to a single central cable (backbone/bus)
• Data travels in both directions along the bus
• Each end has a terminator to prevent signal bounce

Structure:

[Computer] — [Computer] — [Computer] — [Computer]

              Single Cable (Bus)

Advantages:

• Easy to install
• Requires less cable
• Low cost
• Easy to extend
• Good for small networks

Disadvantages:

• If main cable fails, entire network fails
• Heavy traffic slows network
• Difficult to troubleshoot
• Limited cable length
• Security issues (all data visible)

Best for: Small networks, temporary setups

2. Ring topology

Description:

• Devices connected in a closed loop/circle
• Data travels in one direction (or both in dual-ring)
• Each device receives and forwards data

Structure:

   [Computer]

   /          \

[Computer]    [Computer]

   \          /

    [Computer]

Advantages:

• Equal access for all devices
• No collisions
• Can handle heavy traffic
• Easy to identify faults
• Orderly data transmission

Disadvantages:

• One broken connection affects entire network
• Adding/removing devices disrupts network
• Slower than star
• Difficult to troubleshoot
• More expensive than bus

Best for: Networks requiring equal access

3. Star topology

Description:

• All devices connect to a central hub/switch
• Most common topology
• Data passes through central device

Structure:

      [Computer]

            |

[Computer]-[Hub]-[Computer]

            |

       [Computer]

Advantages:

• Easy to install and manage
• Failure of one device doesn’t affect others
• Easy to detect faults
• Easy to add/remove devices
• Good performance
• Centralized control

Disadvantages:

• If central hub fails, entire network fails
• Requires more cable than bus
• Cost of hub/switch
• Hub can be bottleneck

Best for: Most modern networks, schools, offices

4. Mesh topology

Description:

• Every device connects to every other device
• Multiple paths for data
• Most reliable but complex

Structure:

[Computer]—–[Computer]

  |    \    /    |

  |     \/\/     |

  |    /    \    |

[Computer]—–[Computer]

Advantages:

• Highly reliable
• Multiple data paths
• No traffic problems
• Failure doesn’t affect network
• Secure

Disadvantages:

• Very expensive
• Complex installation
• Requires lots of cable
• Difficult to manage
• Hard to troubleshoot

Best for: Critical systems, backbone networks

5. Tree/hierarchical topology

Description:

• Combination of star topologies
• Hierarchical structure
• Root node connects to multiple star networks

Structure:

        [Main Hub]

        /          \

    [Hub]          [Hub]

   /  |  \        /  |  \

 [C] [C] [C]    [C] [C] [C]

Advantages:

• Scalable
• Easy to expand
• Fault isolation
• Point-to-point wiring

Disadvantages:

• If backbone fails, segment goes down
• More cable required
• Complex configuration

Best for: Large organizations, campus networks

6. Hybrid topology

Description:

• Combination of two or more topologies
• Flexible design
• Custom to organization needs

Advantages:

• Very flexible
• Scalable
• Reliable
• Effective

Disadvantages:

• Complex design
• Expensive
• Difficult to manage

Network Components (Brief)

1. Node: Any device on network (computer, printer, etc.)
2. Hub: Connects devices, broadcasts to all
3. Switch: Intelligent hub, sends data only to destination
4. Router: Connects networks, directs traffic
5. Modem: Converts digital to analog signals
6. NIC (Network Interface Card): Enables computer to connect
7. Cables: Ethernet (Cat5e, Cat6), Fiber optic

Wireless Access Point: Enables Wi-Fi connectivity