Networks Revision Notes

Units of Network Speed

Network speed measures how much data can pass through a connection per second. It is typically measured in bits per second (bps). Larger units are commonly used for practical measurements:

• Kilobits per second (Kbps): 1 Kbps = 1,000 bps
• Megabits per second (Mbps): 1 Mbps = 1,000,000 bps
• Gigabits per second (Gbps): 1 Gbps = 1,000,000,000 bps

It's important to remember that these are 'bits', not 'bytes'.

File Size vs. Transmission Rate

File sizes are usually expressed in bytes (B), kilobytes (KB), megabytes (MB), or gigabytes (GB). One byte consists of 8 bits. When calculating data transmission times, ensure both the file size and the transmission rate are in compatible units (e.g., both in bits or both in bytes, although converting file size to bits is standard).

Formula for Transmission Time: Time (seconds) = Total File Size (bits) / Transmission Rate (bits per second)

Key conversions:

• 1 Byte = 8 bits
• 1 KB (Kilobyte) = 1,024 Bytes
• 1 MB (Megabyte) = 1,024 KB
• 1 GB (Gigabyte) = 1,024 MB

Bus Topology Features

A bus topology uses a single backbone cable to which all devices are attached. Signals travel in both directions along the cable and are absorbed by terminators at each end. This setup is cost-effective for small networks due to minimal cabling needs. However, if the main cable fails or has a fault, the entire network can go down, and finding faults can be difficult. Performance issues may also occur due to signal collisions as devices share the same communication channel.

Star Topology Features

In star topology, each device connects to a central hub or switch that controls all data flow in the network. If a device or its connection fails, only that part is affected; the rest continue to communicate. This makes troubleshooting easier and the network more reliable than bus topology. However, if the central device fails, the entire network stops working, and more cabling is usually needed than with a bus.

Mesh Topology Features

A mesh topology enables devices to be directly linked to a number of others, and a full mesh connects every device directly to every other device. This high level of redundancy improves reliability—if one link fails, alternative paths allow data to continue. It is very robust but can be costly and complex to install and maintain, especially in large networks. Partial mesh is more common, used to balance redundancy and practicality.

Core Benefits of Networking Computers

Connecting computers in a network facilitates several key advantages. It enables efficient resource sharing, allowing multiple users to access shared printers, scanners, or software licenses. Data can be centralised and managed more easily, improving data consistency, security through controlled access, and simplified backup procedures. Networks are also crucial for enhanced communication among users, providing platforms for messaging, email, and collaborative document editing. Furthermore, networked systems can offer better performance by distributing computational tasks and providing access to powerful central servers.

Impact on Communication and Collaboration

Networks fundamentally transform how people communicate and collaborate. Instant messaging, email, and video conferencing tools become readily available, bridging geographical distances and enabling real-time interaction. Collaborative software allows multiple individuals to work on the same document or project simultaneously, streamlining workflows and boosting productivity. This interconnectedness supports flexible working environments, such as remote work, by providing secure access to necessary resources and communication channels from virtually anywhere. The ability to share files instantly removes the need for physical media transfer, making data exchange faster and more efficient.

Resource Sharing and Cost Efficiency

One of the most compelling reasons for networking is resource sharing. Instead of purchasing a printer for every computer, a single network printer can serve an entire office. Similarly, expensive software applications can be installed on a central server and accessed by multiple clients, reducing licensing costs. This sharing extends to storage, allowing centralised file servers to store data for all users, which simplifies backup and maintenance. By leveraging shared resources, organisations can significantly reduce hardware and software expenditures, leading to greater cost efficiency and better utilisation of available infrastructure.

Centralisation of Data and Management

Networks allow for the centralisation of data and system management. Storing data on central servers rather than individual machines simplifies data backup and recovery processes, enhances data security through unified access controls and policies, and ensures data consistency across all users. Network administrators can manage user accounts, update software, and apply security patches from a central location, significantly reducing administrative overhead and improving system reliability. This centralisation makes it easier to monitor network performance and troubleshoot issues effectively.

Wired Connectivity

Wired connections, largely employing Ethernet cables, offer superior performance characteristics.

Speed & Bandwidth: Generally provide higher, more stable speeds and greater bandwidth capacity due to direct signal transmission and less interference. Data transfer rates are typically reliable.

Latency: Exhibit lower latency, resulting in quicker response times, which is critical for real-time applications like online gaming or video conferencing.

Range: Limited by cable length. While extenders can be used, the core characteristic is local and fixed.

Reliability: More reliable due to reduced susceptibility to interference and physical obstructions.

Wireless Connectivity

Wireless connections, using Wi-Fi (radio waves), offer mobility at the cost of some performance aspects.

Speed & Bandwidth: Speeds can be lower and less consistent due to interference, signal degradation over distance, and physical obstructions such as walls. Effective bandwidth is often less than theoretical.

Latency: Generally higher latency compared to wired connections due to overhead in processing wireless signals, retransmissions, and potential congestion.

Range: Provides flexibility over a certain area, but signal strength, and thus speed, decreases with distance from the access point. Can be affected by dead zones.

Interference: Highly susceptible to interference from other wireless devices, electronic appliances, and physical barriers, impacting performance.