Computer Studies

12. Computer Networks

Introduction to Computer Networks

A computer network is a system in which two or more computers and other devices are connected together so they can communicate, share resources, and exchange data.

Networks allow computers to share files, printers, internet connections, and software. In modern society, computer networks are essential for communication, business operations, education, banking, and many other activities.

Examples of networks include office networks, school computer labs, and the global internet.

Definition of Network

A computer network is a collection of interconnected computers and devices that communicate with each other through communication channels in order to share resources and information.

A network typically consists of the following elements:

• Computers (nodes)
• Communication links (wired or wireless connections)
• Network devices (router, switch, hub)
• Network protocols (rules for communication)

Example:

In a school computer lab, multiple computers connected to the same system and internet connection form a network.

Benefits of computer networks include:

• Resource sharing (printers, storage, internet)
• Fast communication
• Centralized data management
• Cost reduction
• Collaboration among users

Types of Networks (LAN, MAN, WAN)

Computer networks can be classified based on their geographical coverage area.

Local Area Network (LAN)

A Local Area Network (LAN) is a network that connects computers within a small geographical area such as a room, building, school, or office.

Characteristics of LAN:

• Covers a small area
• High data transfer speed
• Usually privately owned
• Uses Ethernet cables or Wi-Fi

Examples:

• School computer laboratory
• Office network
• Home Wi-Fi network

Advantages of LAN:

• Fast communication
• Easy resource sharing
• Lower cost of setup

Metropolitan Area Network (MAN)

A Metropolitan Area Network (MAN) covers a larger geographical area than a LAN, typically a city or metropolitan region.

It connects multiple LANs within a city.

Characteristics of MAN:

• Covers a city or large campus
• Higher capacity than LAN
• Often managed by service providers

Examples:

• City-wide cable television network
• Large university campus network
• Government communication systems

Wide Area Network (WAN)

A Wide Area Network (WAN) covers a very large geographical area such as a country or even the entire world.

WAN connects multiple LANs and MANs together.

Characteristics of WAN:

• Very large coverage area
• Uses public communication infrastructure
• Slower than LAN due to long-distance communication

The most common example of WAN is the Internet, which connects millions of networks worldwide.

Other examples:

• International banking networks
• Airline reservation systems
• Global company networks

Network Topologies

A network topology refers to the physical or logical arrangement of computers and network devices in a network.

It describes how devices are connected and how data flows between them.

Common network topologies include:

• Bus topology
• Star topology
• Ring topology
• Mesh topology

Bus Topology

In a bus topology, all computers are connected to a single main communication cable called the bus.

Characteristics:

• Simple and inexpensive
• Easy to install
• Data travels along a single cable

Disadvantages:

• If the main cable fails, the entire network stops working
• Performance decreases with more devices

Star Topology

In a star topology, all devices are connected to a central device such as a switch or hub.

Characteristics:

• Easy to manage and maintain
• Failure of one device does not affect others
• Centralized control

Disadvantages:

• If the central device fails, the entire network stops

Star topology is the most commonly used topology in modern networks.

Ring Topology

In a ring topology, each computer is connected to exactly two other computers, forming a circular structure.

Characteristics:

• Data travels in one direction around the ring
• Each device acts as a repeater

Disadvantages:

• Failure of one node may disrupt the entire network
• Difficult to troubleshoot

Mesh Topology

In a mesh topology, every device is connected to multiple other devices.

Characteristics:

• Highly reliable
• Multiple paths for data transmission

Disadvantages:

• Very expensive
• Complex to install

Mesh topology is commonly used in large or critical networks where reliability is important.

Network Devices (Router, Switch, Hub)

Network devices are hardware components that connect computers and control how data moves within a network.

Router

A router is a network device that connects different networks and directs data between them.

Routers determine the best path for data to travel across networks.

Functions of a router:

• Connects multiple networks
• Directs internet traffic
• Assigns IP addresses
• Protects networks with basic security features

Example:

Home internet routers connect local devices (phones, laptops, computers) to the internet.

Switch

A switch is a network device that connects multiple devices within the same network and efficiently directs data to the correct device.

Unlike a hub, a switch sends data only to the intended recipient.

Characteristics:

• Improves network performance
• Reduces data collisions
• Used in modern LAN networks

Example:

Office networks often use switches to connect multiple computers.

Hub

A hub is a basic networking device that connects multiple computers in a network.

When a hub receives data from one computer, it broadcasts the data to all connected devices.

Characteristics:

• Simple and inexpensive
• No data filtering
• Less efficient than switches

Because hubs send data to every device, they can cause network congestion.

Modern networks rarely use hubs and prefer switches.

Conclusion

Computer networks enable computers and devices to communicate and share resources efficiently. Networks may vary in size, from small local networks to global systems such as the internet. Understanding different network types, topologies, and devices helps in designing efficient communication systems. Devices like routers, switches, and hubs play a vital role in connecting computers and managing data transmission within networks. Computer networking has become a fundamental component of modern information technology infrastructure.