Computer Networks Overview

Computer Networks

• A computer network is a collection of interconnected computers and other devices that allow communication between them.
• Devices on a network are connected using communication links, also known as a communication pathway, transferring data between each other.
• Resources on a network include: PCs, laptops, servers, mainframes, printers, file servers, and more.

Network Usages

• Data sharing
• Software sharing
• Hardware sharing
• Personal information sharing
• E-commerce
• Person-to-person communication
• Entertainment
• Game playing
• Client-server applications
• Remote communications
• Other usages

Advantages of Computer Networks

• Enables users to share hardware resources (scanners, printers), reducing costs.
• Allows users to access data stored on other computers, keeping everyone updated with the latest data.
• Enables shared access to the internet.
• Users can run software not installed on their own computers but available on the network.

Bandwidth in Networking

• Network bandwidth measures how much data can be sent and received at one time. Measured in bits, megabits, or gigabits per second.

Physical Topology

• The physical layout of a network.
• Types of topologies include: Mesh, Star, Bus, Ring.

Bus Topology

• A multipoint connection where all devices are connected to a single cable (backbone).

• Each computer and network device is connected to this single cable.

• Communication flows in both directions along the cable.

• Devices can communicate directly with each other, without going through intermediary devices.

• Has drawbacks such as limited number of taps, distance limitations and collision issues when many devices are transmitting simultaneously.

• Advantages of Bus Topology*

• Easy installation

• Use less cabling than mesh or star

• Works well with smaller networks

• Disadvantages of Bus Topology*

• Fault in a cable disrupts all transmissions.

• Adding or removing devices can be complex, requiring modification or replacement.

• Troubleshooting device issues can be difficult.

• Not suitable for large networks due to transmission limitations.

Star Topology

• Each device has a dedicated point-to-point link to a central controller (hub or switch).

• Communication between devices goes through the central controller.

• Easy installation, reconfiguration and cheaper.

• Advantages of Star Topology*

• Easy to install and reconfigure.

• Relatively inexpensive.

• Robustness: if one link fails, only that link is affected, leaving other links functional.

• Easy identification and isolation of fault.

• Disadvantages of Star Topology*

• Dependent on the central hub. If the hub fails, the entire network is down.

Tree Topology

• A variation of the star topology where secondary hubs are connected to a central hub.
• Advantages and disadvantages are similar to the star topology but with increased flexibility in connecting a larger number of devices.

Ring Topology

• Each device is connected to two other devices, forming a closed loop.
• Communication flows in one direction around the ring.
• Each device acts as a repeater, regenerating the signal to maintain quality and strength.
• Easy to install and reconfigure as devices only require two connections.
• Has simplified fault isolation due to a circulating signal.
• Unidirectional traffic is a significant disadvantage when a device fails it disrupts the entire network; to address this a dual ring can be implemented.