Welcome to Networking & Internet Basics!

Hey there! Ready to dive into the amazing world of how computers talk to each other? This chapter is all about the magic that connects your phone to social media, your computer to Google, and your game console to your friends online. It's called networking!

Understanding these basics is super important because the internet and networks are everywhere. By the end of this, you'll understand how it all works, from the cables in the wall to the Wi-Fi in the air. Let's get started!


1. What is a Computer Network? (LANs vs. WANs)

A computer network is simply two or more computers connected together so they can share information and resources (like printers or an internet connection). The two main types you need to know are LAN and WAN. Think of it like talking to people: a LAN is a chat in a small room, while a WAN is a phone call to another country!

Local Area Network (LAN)

A LAN connects devices over a small geographical area. It's the network you have at home, in your school's computer lab, or within a single office building.

  • Scope: Small area (e.g., a single building or campus).
  • Speed: Usually very fast because the distances are short.
  • Ownership: Privately owned and managed (e.g., your family owns your home network, your school owns the school network).

Wide Area Network (WAN)

A WAN connects devices over a large geographical area, like across cities, countries, or even continents. A WAN is often a network of many LANs connected together.

  • Scope: Large area (e.g., connecting offices in Hong Kong and London).
  • Speed: Generally slower than a LAN because data has to travel much further.
  • Ownership: Often managed by telecommunication companies and service providers.

The biggest WAN in the world is the Internet!

Key Takeaway: LAN vs. WAN

The easiest way to remember the difference is the geographical span. If it is in one building, it is a LAN. If it connects different locations far apart, it is a WAN.


2. What Can We Do on a Network? (Network Services)

So, why do we connect computers? Because it lets us do cool and useful stuff! These are called network services.

Resource Sharing

Instead of everyone needing their own separate equipment, we can share.

  • File Sharing: You can access files stored on a central computer called a server (e.g., cloud drives or school network drives).
  • Hardware Sharing: An entire office can share one single printer or scanner to save costs.
  • Internet Connection Sharing: Your home router shares one internet connection with your phone, laptop, and smart TV simultaneously.

Internal Communications and Conferencing

  • Communication: Sending emails or instant messages to users across the network.
  • Conferencing: Holding video or audio calls with people in different locations.

3. The Building Blocks: Network Hardware

To build a network, physical transmission media and connecting hardware are required.

Communication Links

  • Unshielded Twisted Pair (UTP) Cable: Standard copper Ethernet cable commonly used for wired LAN connections.
  • Fibre Optic Cable: Uses glass or plastic strands to transmit data as light pulses. It offers very high bandwidth, long transmission distances, and immunity to electrical interference.
  • Wireless (Microwave, Satellite): Uses electromagnetic waves to send data over the air. Microwaves connect line-of-sight locations, while satellites connect long distances across continents or oceans.

Key Network Connecting Devices

  • Network Interface Card (NIC): The hardware component inside a device that allows it to connect to a wired or wireless network.
  • Modem: Short for MOdulator-DEModulator. Converts digital signals from computers into analog signals for transmission lines, and vice versa.
  • Hub: A basic device that connects multiple computers in a LAN. When it receives data, it broadcasts the data to all connected ports, creating unnecessary network traffic and collision risks.
  • Switch: A smarter device used inside a LAN. It inspects incoming data packets and forwards them only to the specific destination port (point-to-point forwarding), reducing traffic and collisions.
  • Router: A device that connects different networks (such as joining a home LAN to the Internet). It determines the best path to route packets between networks using IP addresses.
Quick Review: Hub vs. Switch vs. Router

- A Hub broadcasts data to every device on the same LAN.
- A Switch delivers data directly to the target device on the same LAN.
- A Router moves data between different networks.


4. Going Wireless: Key Wi-Fi Concepts

Wireless Local Area Networks (WLANs) use radio frequency signals.

  • Frequency Bands: Wi-Fi commonly operates on 2.4 GHz (longer range, lower speed, more interference) and 5 GHz (shorter range, faster speed, less congested).
  • Bandwidth: The data transfer capacity of a network channel over a given period of time. Higher bandwidth allows more data to be transmitted simultaneously.
  • Interference: Disruption to wireless signals caused by physical obstacles (concrete walls) or electronic devices (microwaves, cordless phones).
  • Roaming: The seamless handover of a wireless client from one Access Point (AP) to another as the user moves around, maintaining continuous connectivity.

5. How We Connect to the Internet

Comparing Internet Access Methods

Broadband (e.g., Fibre-to-the-Home / FTTH)

  • Speed & Stability: Very high, stable, and low latency.
  • Cost: Fixed monthly subscription fee.
  • Security: High, dedicated wired link to the premises.
  • Availability: Widely available across urban areas.

Mobile Data (4G / 5G)

  • Speed & Stability: Fast speeds (especially 5G), but speed varies based on signal strength and cell congestion.
  • Cost: Tiered monthly pricing based on data usage limits.
  • Security: Secured via cellular encryption standards.
  • Availability: Highly accessible anywhere covered by mobile base stations.

6. Network Protocols, Addressing & Internet Identifiers

A protocol is an agreed set of rules and standards that allows computing devices to communicate with each other.

The TCP/IP Suite

  • TCP (Transmission Control Protocol): Responsible for reliable data delivery. It divides data into packets, sequences them with numbers, checks for lost packets, requests retransmissions if errors occur, and reassembles them at the destination.
  • IP (Internet Protocol): Responsible for addressing and routing individual packets from source to destination across networks.

IP Addresses: Public vs. Private & IPv4 vs. IPv6

Every device communicating over the Internet requires an IP address.

  • IPv4: A 32-bit address represented as four decimal numbers separated by dots (e.g., 192.168.1.1). Because the unallocated global pool of around 4.3 billion IPv4 addresses is largely depleted, IPv6 and NAT are used.
  • IPv6: A 128-bit address written in hexadecimal format separated by colons (e.g., 2001:0db8:85a3::8a2e:0370:7334), providing an enormous address space.
  • Public IP vs. Private IP: A Public IP is unique globally and directly routable on the Internet. A Private IP (e.g., 192.168.x.x, 10.x.x.x) is used only within a local private network (LAN) and cannot be routed across the public Internet directly.

Domain Names and URLs

  • DNS (Domain Name System): Translates human-friendly domain names (e.g., www.edb.gov.hk) into machine-readable numerical IP addresses.
  • URL (Uniform Resource Locator): The full address used to locate a specific resource on the web. A URL consists of:
    - Protocol: e.g., https://
    - Domain / Host Name: e.g., www.example.com
    - Path & Filename: e.g., /ict/notes.html

Common Application Layer Protocols

  • HTTP (HyperText Transfer Protocol) / HTTPS (Secure): Transmits web page content. HTTPS uses encryption (SSL/TLS) for secure data transmission.
  • FTP (File Transfer Protocol): Used for uploading and downloading files between a client and a remote server.
  • SMTP (Simple Mail Transfer Protocol): Used to send email messages between servers or from a client to a mail server.
  • POP3 (Post Office Protocol 3) / IMAP (Internet Message Access Protocol): Used to retrieve / download incoming emails from a mail server.