Information Technology (9626) | Communications technology

Welcome to Communications Technology (Topic 14)!

Hello there! This chapter is all about how computers talk to each other—the literal highways and rules that make the internet, mobile phones, and even your school network function.
This topic is fundamental to understanding modern IT, and while some concepts like protocols can seem abstract, we will break them down using simple, everyday analogies.
Ready to learn how data travels the world? Let's dive in!

14.1 Networks: The IT Superhighway System

A network is simply a group of interconnected computing devices capable of exchanging data. Knowing the different types helps us understand their uses and limitations.

Types of Networks

• Local Area Network (LAN): Connects devices in a limited geographical area, like an office building or a home. (Think of your home Wi-Fi.)
• Wide Area Network (WAN): Connects devices over a large geographical area, often spanning cities or countries. It often consists of multiple interconnected LANs. (Think of the Internet itself, or a multinational company's network.)
• Client-Server: A central powerful computer (the server) manages resources and provides services to many user computers (the clients).
• Peer-to-Peer (P2P): Devices share resources directly with each other without needing a central server. (Often used for file sharing like BitTorrent.)
• Virtual Private Network (VPN): Creates a secure, encrypted "tunneling" connection over a public network (like the internet). Used for secure access to a remote private network (e.g., accessing your school network from home).
• Mobile Networks: Networks designed for cellular communication (3G, 4G, 5G).

Characteristics of Networks

Networks are defined by their topologies (the physical and logical layout) and their architecture (the design framework, like client-server or P2P). They also require protocols (rules).

Network Uses (Why we need them)

• Sharing Resources: Sharing hardware (printers, scanners) and software licenses.
• Sharing and Storage: Centralised data storage (like a file server).
• Exchange of Data: Email and instant messaging.
• Access to Internet Services: Connecting to the world wide web.
• Content Delivery Services: Streaming videos (Netflix, YouTube) and downloading software.

Key Takeaway (14.1): The main difference between LAN and WAN is size. Client-server offers centralised control and security, while P2P is decentralized. VPNs ensure privacy via tunneling.

14.2 Network Components: The Essential Hardware

These are the devices that physically make communication possible. Each has a specific role in moving and managing data packets.

• Network Interface Card (NIC) / Wireless NIC: Allows a device (computer, phone) to connect to the network. It handles the low-level data transmission details.
• Hubs: Simple devices that broadcast incoming data packets to *all* connected devices. They are inefficient as they create network congestion.
• Switches: Smarter than hubs. They read the destination address (MAC address) of a data packet and only send it to the intended recipient, reducing congestion.
• Repeaters: Boost or regenerate a signal to extend the range of the network.
• Wireless Access Points (WAPs): Allow wireless devices to connect to a wired network infrastructure.
• Bridges: Connect two separate LANs that use the same protocol.
• Routers: Connect different networks together (e.g., your home LAN to the Internet WAN). They use IP addresses to determine the best path for data.
• Gateways: Act as an entry/exit point to a network and often translate data between two networks using different protocols.

Did you know? A switch is like a post office sorter—it knows exactly where to send the letter. A hub is like yelling the message into a crowded room, hoping the right person hears it.

14.3 Network Servers: The Central Providers

Servers are powerful computers that provide resources, services, or data to other computers. Their operation often uses the 'request and response' method.

Types of Network Servers

• File Server: Stores and manages user files and shared resources.
• Web Server: Stores and delivers web pages and content using HTTP/S.
• Mail Server: Manages and stores email messages (using protocols like SMTP, POP3, IMAP).
• Applications Server: Hosts, delivers, and manages high-end or large applications.
• Print Server: Manages print jobs from multiple clients to shared printers.
• FTP Server: Manages the uploading and downloading of files using the File Transfer Protocol.
• Proxy Server: Acts as an intermediary, filtering requests between the client and the main server (improving security and speeding up access to frequently used pages).
• Virtual Server: A server that exists only as software, running on top of physical hardware (allowing better resource utilisation).

A server farm is a large collection of servers usually housed in a single location, working together to handle massive data loads (e.g., Google or Amazon).

14.4 Cloud Computing: Shared Resources

Cloud computing involves accessing computing services (like storage, databases, or software) over the internet ("the cloud") rather than owning the physical infrastructure locally.

Characteristics and Uses

• Sharing Computing Resources: The key characteristic is that massive resources are pooled and shared among many users (multi-tenancy).
• Uses (Individuals): Online email (Gmail), file storage (Dropbox), streaming media (Spotify).
• Uses (Organisations): Hosting websites, managing massive databases, running enterprise software (like CRM).

Advantages: Reduced capital expenditure (no need to buy servers), scalability (easily increase or decrease resources), universal access.
Disadvantages: Reliance on internet connectivity, potential security/privacy concerns (data stored by a third party).

14.5 Data Transmission Across Networks

Speed and Measurement

• Bandwidth: The maximum amount of data that can be transmitted over a communication channel in a given time. (The size of the pipe.)
• Bit Rate: The speed at which data is actually transferred, usually measured in bits per second (bps). (How fast the water flows through the pipe.)
• Bandwidths Available: Transmission media offer vastly different speeds:
  
  • Ethernet: Good for LANs.
  • Fibre Optic: Extremely high bandwidth, used for long distances and internet backbones.
  • Wireless/Mobile: Convenient, but speeds can vary drastically based on signal strength.

Data Streaming

Data streaming is the continuous flow of data, usually audio or video, accessed instantly rather than waiting for the entire file to download.

• Real Time Streams: Live broadcasts (e.g., a football match). Requires very low latency.
• On Demand Streams: Pre-recorded content (e.g., YouTube video).
• Impact of Bit Rate and Bandwidth: Low bandwidth leads to buffering and poor quality, especially for high-resolution content like Ultra-High Definition Television (UHDTV).

Transmission Methods

• Fibre Optic: Data transmitted as light pulses. Characteristics: Extremely fast, immune to electromagnetic interference, very high bandwidth.
• Copper Cables (Coaxial and Twisted Pair): Data transmitted as electrical signals. Characteristics: Slower than fibre, susceptible to interference, cheaper.
• Lasers: Often used for short-range line-of-sight communication or specialised secure links.

The medium significantly affects available bandwidth. Fibre optic allows the highest bandwidth, which is essential for high-quality audio and video streaming services.

14.6 Network Protocols: The Rules of the Road

Protocol Definition and Necessity

A protocol is a set of formal rules or procedures governing how data is formatted, transmitted, received, and managed across a network.
Protocols are necessary because they ensure all devices speak the same "language," enabling communication regardless of hardware or operating system.

Key Protocols and Their Purposes

Don't worry if this list seems long! Focus on knowing the core function of each group (e.g., HTTP for web, SMTP/POP/IMAP for email, TCP/IP for routing and connection).

• Transmission Control Protocol (TCP): Ensures reliable, ordered, and error-checked delivery of data.
• Internet Protocol (IP): Handles addressing and routing of packets so they reach the correct destination (IPv4 and IPv6).
• Hypertext Transfer Protocol (HTTP / HTTPS): Used for web browser communication. HTTPS is the secure version (using TLS/SSL).
• File Transfer Protocol (FTP): Used for the transfer of computer files between a client and server.
• Mail Protocols:
  • Simple Mail Transfer Protocol (SMTP): Used for *sending* email.
  • Post Office Protocol 3 (POP3): Used for *retrieving* email (typically deletes it from the server).
  • Internet Message Access Protocol (IMAP): Used for *retrieving* email (keeps a copy on the server).
• Network Security Protocols:
  • Transport Layer Security (TLS) / Secure Socket Layer (SSL): Used to encrypt communication between a client and a server (e.g., when you see a padlock in your browser).
  • Internet Protocol Security (IPsec): Used to secure internet communication, often in VPNs (tunneling protocols like L2TP).
• Addressing and Configuration:
  • MAC Addressing: Unique hardware address assigned to a NIC.
  • Address Resolution Protocol (ARP): Maps an IP address to a physical MAC address.
  • Dynamic Host Configuration Protocol (DHCP): Automatically assigns IP addresses to devices joining a network.

Methods of Sending Data

How data gets from A to B fundamentally relies on switching methods:

1. Packet Switching:

Data is broken down into small units called packets. Each packet contains the destination address, sequence number, and error-checking information.
Packets travel independently along the fastest available route and are reassembled at the destination.

Modes of Connection:

• Connection Mode (TCP): Requires a formal setup (handshake) before data transfer begins, guaranteeing delivery and order. (e.g., Frame Relay)
• Connectionless Mode (IP, UDP): Sends data without prior arrangement; faster, but delivery and order are not guaranteed. (e.g., Ethernet)

2. Circuit Switching:

A dedicated, continuous communication channel is established between two parties for the entire duration of the communication. (Think of an old landline phone call.)

3. Message Switching:

Uses a store and forward method. The entire message is sent to an intermediate node (router), stored temporarily, and then forwarded when the route is clear. Used mainly for non-real-time data like older forms of email.

Protocol Layering (OSI and TCP/IP)

Protocols are organised into layers, where each layer performs a specific function and relies on the layer below it.
The two main models are the Open Systems Interconnection (OSI) model (7 layers) and the simplified TCP/IP suite (4 or 5 layers).

The Function of Each Layer in TCP/IP:

1. Application Layer: Provides network services to applications (HTTP, FTP, SMTP).
2. Transport Layer: Manages end-to-end communication and error checking (TCP, UDP).
3. Internet Layer: Handles addressing and routing (IP).
4. Network Access Layer: Handles physical transmission of data (Ethernet, Wi-Fi).

Routing

Routers use routing protocols to determine the most efficient path for data packets.
Protocols include Interior Gateway Protocols (used within an autonomous network) and Exterior Gateway Protocols/Border Gateway Protocols (used between different autonomous networks, like connecting to the wider internet).

• Static Routing: Paths are manually configured by an administrator. Used in small, stable networks.
• Dynamic Routing: Routers automatically adjust paths based on real-time network traffic and routing tables. More efficient for large, changing networks.

Key Takeaway (14.6): Protocols are essential rules. TCP/IP is the backbone of the internet, handling both addressing (IP) and reliable delivery (TCP). Data travels primarily via efficient packet switching.

14.7 Wireless Technology

Wireless transmission allows communication without physical wires, using electromagnetic waves.

Methods of Wireless Transmission

• Wi-Fi (Wireless Fidelity): Uses radio waves for high-speed local network access.
• Bluetooth: Short-range radio technology for connecting devices (e.g., headphones, keyboards).
• NFC (Near Field Communication): Very short-range (a few centimetres) for quick data exchange (e.g., contactless payments).
• Infrared (IR): Uses light waves; requires line-of-sight (e.g., TV remote control).
• Microwave / Radio: Used for long-distance communication (including satellite links).

Operation and Uses

• Wireless Protocols: Sets of rules defining how wireless devices communicate (e.g., Wi-Fi uses the 802.11 standards).
• Wireless Power Transfer: The transmission of electrical energy without wires (e.g., induction charging pads).
• Uses: Mobile communications, data exchange (sharing files via Bluetooth), and enabling the Internet of Things (IoT), where everyday objects are networked.

Security Issues in Wireless Transmission

Because signals travel through the air, they are easily intercepted.
Prevention Methods:

• Encryption: Scrambling the data so only the intended recipient can read it.
• Wireless Security Protocols: Using strong protocols like WPA (Wi-Fi Protected Access) or its variants (WPA2, WPA3). (Note: WEP is older and largely insecure.)
• Strong Passwords: Limiting access to the network itself.

14.8 Mobile Communication Systems

Cellular Networks (3G, 4G, 5G)

Mobile networks rely on dividing geographical areas into "cells," each served by a base station (mast).

• Structure: As you move, your device is automatically handed off from one cell to the next, maintaining the connection.
• 3G/4G/5G: Generations of technology offering increasing bandwidth and speed. 5G is designed for ultra-low latency and massive connectivity, crucial for IoT and autonomous systems.

Satellite Communication Systems

Used where terrestrial networks (fibre/copper) are unavailable or impractical (e.g., remote areas, ships).

• Operation: Data is prepared, sent up to an orbiting satellite, and then broadcast down to a receiving station on Earth.
• Global Positioning Systems (GPS): Uses satellites to provide location and time information to a receiver on Earth.
• Uses: Global mapping, long-distance telecommunications (radio/TV broadcasting, telephones), and ultra-high definition television systems.

14.9 Network Security

Protecting network infrastructure and data from unauthorised access and damage is vital.

Network Security Threats

• Malicious Actors (Perpetrators): Individuals or groups carrying out attacks.
• Malware: Includes viruses, worms, and ransomware (covered in section 5.2).
• Denial of Service (DoS): Overwhelming a system with requests to shut it down.
• Brute Force: Automated attempts to guess passwords or encryption keys.
• Botnets: A network of compromised computers (bots) used to carry out attacks (like DoS).
• SQL Injection: Attacker manipulates a website's database by inserting malicious code into input fields.
• (Poor) Network Policies: Weak passwords, lack of training, or outdated security practices.

Impact of Threats

Threats lead to data destruction, theft by unauthorised users, manipulation of data, and identity theft (stealing personal information for fraudulent use).

Prevention Methods

Prevention involves both physical and software methods:

Physical/Procedural Barriers:

• Use of barriers, locks, alarm systems, and security guards.

Software Methods:

• Firewalls (Hardware/Software): Placed between the internal network and the outside world. They examine traffic and block packets based on a configured rule set.
• Encryption: Protecting data in transit or storage.
• Anti-malware: Anti-virus and anti-spyware software to protect data, files, and systems.
• Biometric Methods: Using unique biological characteristics (fingerprints, iris scans) for authentication.
• Access Rights/Permissions: Granting only necessary permissions to users (e.g., Read-only vs. Edit access).

14.10 Disaster Recovery Management

This is the plan for recovering data and systems following a catastrophic event.

Identification of Threats and Risks

Disasters can cause data loss and business disruption. Types include:

• Natural Disasters: Floods, earthquakes.
• Equipment and Power Failures: Hardware breakdown, blackout.
• Cybercrime / Malware / Criminal Activity: Deliberate attack or infection.
• Accidental Disruptive Events: Human error (e.g., mistakenly deleting a key server file).

Risk Analysis: Involves identifying potential threats and assessing their impact.
Perpetrator Analysis: Identifying who might want to cause harm and their methods.
Risk Testing / Quantifying the Risk: Testing recovery procedures and putting a monetary value on the potential loss.

Control of Threats and Minimising Risks

We must plan how to detect and prevent threats, and how to restore after a disaster.

Strategies to Minimise Risks:

• Protection for Power Supplies: Using Uninterruptible Power Supplies (UPS) and surge protectors to guard against power failures.
• Use of Passwords and Access Controls: Limiting who can access which parts of the system and data.
• Protection of Data and Software: Using anti-malware and ensuring no unauthorised access.
• Use of Back-up Strategies: Crucial for restoration. Backups must be tested and stored securely (often off-site).

Key Takeaway (14.10): Disaster recovery isn't just about restoring data; it's a comprehensive strategy covering risk identification, prevention (firewalls, power protection), and restoration (backups).