Learning Objectives

By the end of this chapter, you will be able to:

  • Define a computer network.
  • Differentiate between a Local Area Network (LAN) and a Wide Area Network (WAN).
  • Describe the common network topologies: Bus, Star, and Ring.

What is a Computer Network?

A computer network is a collection of two or more computers and other hardware devices connected together to share resources and exchange data.

Network Types

Networks are often classified by their geographical scope.

  • Local Area Network (LAN): A network that connects computers within a limited geographical area, such as a single building or a school campus. Most LANs are used to share resources like printers and files.

  • Wide Area Network (WAN): A network that covers a broad geographical area, such as a city, country, or even the entire globe. A WAN is often a collection of interconnected LANs. The most well-known example of a WAN is the Internet.

flowchart LR
    subgraph LAN["LAN - Local Area"]
        B1[Building A]
        B2[Building B]
    end
    subgraph WAN["WAN - Wide Area"]
        CITY[City Network]
        GLOBAL[Internet]
    end
    LAN --> WAN

Figure 1: LAN vs WAN Scope

Network Topologies

Network topology refers to the physical layout or arrangement of the devices on a network. The most common topologies are:

  • Bus Topology: All devices are connected to a single central cable, called the bus or backbone.
    • Disadvantage: If the main cable fails, the entire network goes down.
  • Star Topology: All devices are connected to a central hub or switch. This is the most common topology used in modern LANs.
    • Advantage: If one cable fails, only that single device is affected. The rest of the network continues to function.
  • Ring Topology: All devices are connected in a closed loop or ring. Data travels around the ring in one direction.
    • Disadvantage: If one device or cable fails, it can break the ring and take down the entire network.
flowchart TB
    subgraph STAR["Star Topology"]
        SH[Hub/Switch]
        SD1[Device] --- SH
        SD2[Device] --- SH
        SD3[Device] --- SH
    end
    subgraph BUS["Bus Topology"]
        BC[Backbone Cable]
        BD1[Device] --- BC
        BD2[Device] --- BC
        BD3[Device] --- BC
    end
    subgraph RING["Ring Topology"]
        RD1[Device 1] --> RD2[Device 2] --> RD3[Device 3] --> RD1
    end

Figure 2: Bus, Star, and Ring Topologies

Summary

A computer network is a group of connected computers that can share resources. Networks are classified by size, with LANs covering a small area and WANs covering a large area. The physical layout of a network is its topology. While older networks used Bus and Ring topologies, the modern standard for LANs is the more robust and reliable Star topology.

Key Takeaways

  • A network is a collection of connected computers.
  • LANs are local; WANs are wide-area. The Internet is a WAN.
  • Network topology is the physical layout of the network.
  • Star topology is the most common modern LAN topology.

Discussion Questions

  1. What type of network do you have in your home or school (LAN or WAN)?
  2. Why is the Star topology more reliable than the Bus or Ring topology?
  3. Can you think of a situation where a Bus topology might still be useful?