Unit 10: Internet

I. Foundations — The Internet as a Global Network

The Internet is a worldwide system of interconnected computer networks that developed from earlier research networks such as ARPANET (1969). It uses standard communication rules, especially the Internet Protocol suite, to transfer data among computers, phones, servers, and other devices.

• Defining properties:
  • Network of networks: Home, school, business, and government networks connect through telecommunications infrastructure.
  • Packet switching: Data is divided into small units called packets, transmitted through available routes, and reassembled at the destination.
  • TCP/IP standards: Internet Protocol (IP) addresses and routes packets, while Transmission Control Protocol (TCP) provides reliable, ordered delivery.
  • Distributed structure: No single computer contains or controls the entire Internet; services operate through many interconnected systems.
  • Client-server interaction: A client, such as a browser, requests a resource from a server, which processes the request and returns data.
  • Many services: The World Wide Web, email, messaging, file transfer, Internet telephony, and videoconferencing all use the Internet.
  • Internet versus Web: The Internet is the underlying network; the World Wide Web is one service operating on it.

II. Internet Vocabulary — Essential Concepts

A. Basic Internet terms

Basic Internet terms describe the devices, rules, actions, and data involved in online communication.

• Online and offline: A device is online when connected to a network service and offline when disconnected.
• Upload and download: Uploading sends data from a local device to the Internet; downloading receives data, such as saving a PDF from a website.
• IP address: A numerical identifier locates a device or network interface; an IPv4 example is 192.0.2.10.
• Domain name: A readable name, such as example.com, represents an Internet location and is translated into an IP address by the Domain Name System (DNS).
• Protocol: A protocol is a set of communication rules; examples include HTTP, HTTPS, SMTP, and TCP/IP.
• Bandwidth and latency: Bandwidth is data-carrying capacity, commonly measured in Mbps; latency is transmission delay, usually measured in milliseconds.
• Link: A clickable reference connects one online resource to another.

III. Web Documents — Individual Online Resources

A. Web page

A web page is a single document on the World Wide Web that a browser retrieves and displays.

• Construction: HyperText Markup Language (HTML) defines structure, Cascading Style Sheets (CSS) control presentation, and JavaScript can provide interactive behavior.
• Contents: A page may contain text, images, audio, video, forms, menus, and hyperlinks.
• Address: Each accessible page normally has a URL, such as https://example.com/help/contact.html.
• Types:
  • Static page: Sends largely fixed stored content to every visitor.
  • Dynamic page: Generates or changes content using programs, databases, user input, or account details.
• Retrieval: A browser sends an HTTP or HTTPS request to a web server, which returns the page and its supporting files.
• Example: A school’s “Admission Requirements” page is one web page within the school’s larger website.

IV. Collections of Web Resources — Organized Online Presence

A. Website

A website is an organized collection of related web pages and resources published under a common domain name.

• Organization: Pages are connected through navigation menus and hyperlinks; common sections include “About,” “Services,” and “Contact.”
• Ownership: A person, company, school, government agency, or other organization may maintain a website.
• Hosting: Website files and applications are stored on a web server or distributed through cloud infrastructure.
• Identification: In https://www.example.com/products, example.com identifies the domain, while /products identifies a resource path.
• Purposes: Websites support publishing, education, communication, entertainment, public services, and electronic commerce.
• Website versus web page: A website is the whole collection; a web page is one document within that collection.

V. Website Entry Points — Main Navigation Pages

A. Home page

A home page is the principal or introductory page of a website and usually provides access to its major sections.

• Typical address: Entering a base domain such as https://example.com/ commonly opens the site’s home page.
• Navigation role: Menus, category links, search boxes, and featured content guide visitors to internal pages.
• Identity role: The organization’s name, logo, purpose, and major announcements commonly appear prominently.
• Browser distinction: A website’s home page is not necessarily the same as the page configured to open when a browser starts.
• Design principle: Important links should be clearly labelled and usable on both desktop and mobile screens.
• Example: A university home page may link to admissions, departments, examinations, library services, and student portals.

VI. Web Access Software — Retrieving and Displaying Content

A. Browser

A browser is an application that requests, interprets, and presents resources from the World Wide Web.

• Examples: Google Chrome, Mozilla Firefox, Microsoft Edge, Apple Safari, and Opera are web browsers.
• Core operation: The user enters a URL; the browser contacts the appropriate server, receives files, and renders the page.
• Standards: Browsers interpret HTML, CSS, and JavaScript according to web standards.
• Common functions: Tabs, bookmarks, history, downloads, printing, password storage, and private-browsing modes assist navigation.
• Security indicators: HTTPS and the padlock symbol indicate encrypted communication, but they do not prove that a website is honest.
• Browser versus search engine: Chrome is browser software; Google Search and Bing are search services opened within a browser.

VII. Internet Addressing — Locating Resources

A. URL

A Uniform Resource Locator (URL) is the structured address used to identify and access an Internet resource.

• Example structure:

https://www.example.com:443/docs/page.html?topic=internet#terms

• Components:
  • Scheme: https specifies the access protocol.
  • Host: www.example.com identifies the server’s domain name.
  • Port: 443 identifies the network service; it is normally omitted for standard HTTPS.
  • Path: /docs/page.html locates a resource.
  • Query: ?topic=internet sends parameters.
  • Fragment: #terms points to a section within the resource.
• Safety: Users should inspect spelling and the actual domain before opening links or entering credentials.

VIII. Linked Information — Non-Linear Navigation

A. Hypertext

Hypertext is text containing electronic links that allow users to move directly to related documents or sections.

• Hyperlink function: A highlighted word, image, or button acts as an anchor connected to another resource.
• Non-linear reading: Users can follow links according to need instead of reading material only from beginning to end.
• HTML anchor:

<a href="https://example.com/help">Help</a>

• Element meaning: <a> creates the anchor, href stores the destination, and Help is the clickable text.
• Internal and external links: An internal link opens another location within the same site; an external link leads to a different site.
• Hypermedia: The same linking principle can connect images, sound, animation, and video, not only text.

IX. Internet Connectivity — Access Providers

A. Internet service provider

An Internet service provider (ISP) is an organization that connects customers to the Internet and may supply related services.

• Connection methods: Fibre-optic, cable, DSL, fixed wireless, satellite, and mobile networks such as 4G or 5G provide access.
• Provider equipment: The ISP links a customer’s modem or router to its network and forwards traffic to other Internet networks.
• Service plan: Plans may specify speed, data allowance, price, contract length, and expected availability.
• Performance: A plan advertised as 100 Mbps describes a maximum data rate, not a guarantee that every download will maintain that speed.
• Additional services: ISPs may provide email accounts, DNS resolution, web hosting, security tools, or technical support.
• Limitations: Congestion, distance, equipment quality, weather, and service outages can affect access.

X. Hosting Systems — Serving Internet Resources

A. Web server

A web server is hardware and software that stores, processes, or delivers web resources in response to browser requests.

• Server software: Apache HTTP Server, Nginx, and Microsoft Internet Information Services are common examples.
• Request-response process:
  1. A browser sends an HTTP or HTTPS request.
  2. The server locates or generates the requested resource.
  3. It returns a response containing a status code, headers, and content.
• Status codes: 200 means a request succeeded, 404 means a resource was not found, and 500 indicates a server-side error.
• Dynamic processing: Server programs may query databases to produce account pages, search results, or shopping carts.
• Security: Servers use access controls, updates, backups, firewalls, and TLS certificates to protect services and encrypted connections.

XI. The Global Web — Interlinked Information System

A. World Wide Web

The World Wide Web (WWW) is a global system of interlinked resources accessed over the Internet, proposed by Tim Berners-Lee in 1989.

• Core technologies: HTML structures documents, URLs identify resources, and HTTP or HTTPS transfers them.
• Operating model: Browsers function as clients, web servers supply resources, and hyperlinks connect resources.
• Internet distinction: The Web uses Internet infrastructure but is not the entire Internet; email and Internet calling can operate independently of web pages.
• Open standards: Shared technical standards allow different browsers, devices, and servers to communicate.
• Uses: The Web supports news, digital libraries, online banking, government portals, social platforms, and e-commerce.
• Access requirements: A user normally needs a connected device, Internet service, browser software, and the relevant URL or search facility.

XII. Electronic Mail — Store-and-Forward Communication

A. Email

Email is a system for sending electronic messages and files between addresses over computer networks.

• Address format: In student@example.com, student is the mailbox name and example.com is the domain.
• Message fields: To identifies primary recipients, Cc sends visible copies, Bcc conceals copied recipients, and Subject states the topic.
• Protocols: SMTP sends outgoing mail; IMAP synchronizes server-based mail; POP3 commonly downloads messages to a client.
• Attachments: Documents, images, and other files can accompany a message, subject to provider size limits.
• Advantages: Email is fast, inexpensive, searchable, and suitable for formal or delayed communication.
• Risks: Spam, phishing links, malicious attachments, and accidental “Reply All” messages require careful handling.

XIII. Real-Time Text Communication — Immediate Messaging

A. Instant messaging

Instant messaging (IM) enables near-real-time exchange of text and multimedia between connected users.

• Examples: WhatsApp, Signal, Telegram, Microsoft Teams, and similar services support private or group conversations.
• Features: Presence indicators, typing notices, read receipts, emojis, file sharing, voice notes, and group chats may be available.
• Delivery model: Messages usually pass through service servers and may be stored until the recipient reconnects.
• Comparison with email: IM favors brief, immediate exchanges, whereas email is generally better suited to formal or longer communication.
• Security: End-to-end encryption, where provided, prevents intermediaries from reading message content in transit.
• Responsible use: Users should verify contacts, avoid sharing passwords or sensitive documents, and control notification and privacy settings.

XIV. Voice Communication — Calling over Internet Networks

A. Internet telephony

Internet telephony uses Internet Protocol networks to transmit voice calls, commonly through Voice over Internet Protocol (VoIP).

• Conversion process: A microphone captures speech, software converts it into digital packets, and the receiving device reconstructs the audio.
• Examples: VoIP calling may occur through dedicated IP phones, computer applications, or smartphone calling services.
• Requirements: A device, microphone, speaker or headset, suitable application, and stable Internet connection are needed.
• Advantages: Calls can be inexpensive, portable, and integrated with voicemail, contact lists, and conferencing.
• Quality factors: Low bandwidth, high latency, packet loss, or jitter can cause delay, broken sound, or echoes.
• Limitation: Unlike a traditional powered telephone line, an Internet call may fail during electricity or broadband outages.

XV. Audio-Visual Collaboration — Remote Meetings

A. Videoconferencing

Videoconferencing enables participants in different locations to communicate through live video, audio, and shared digital content.

• Components: A camera, microphone, speakers or headset, display, conferencing software, and broadband connection form the basic setup.
• Examples: Zoom, Google Meet, Microsoft Teams, and Webex provide meeting platforms.
• Collaboration tools: Screen sharing, text chat, virtual backgrounds, recording, captions, and breakout rooms support group work.
• Uses: Schools conduct online classes, businesses hold meetings, and health professionals may provide remote consultations.
• Quality controls: Muting unused microphones, using headphones, improving lighting, and limiting background activity reduce disruption.
• Privacy: Meeting passwords, waiting rooms, controlled screen sharing, and careful handling of recordings protect participants.

XVI. Browser Workspace — User Interface and Controls

A. Web browser and its environment

The web browser environment consists of the visible controls, content area, settings, and stored data through which users interact with the Web.

• Interface components:
  • Address bar: Accepts URLs and often search terms.
  • Navigation buttons: Back, Forward, Reload, and Home control movement.
  • Tabs: Separate several pages within one browser window.
  • Content area: Displays the rendered web page.
  • Menu and toolbar: Provide printing, zoom, downloads, extensions, and settings.
• Stored information: History records visited pages, bookmarks save chosen addresses, cache stores resource copies, and cookies retain site-specific data.
• Management tools: Download managers display file progress; developer tools inspect HTML, CSS, scripts, and network requests.
• Safe operation: Keep the browser updated, restrict unnecessary extensions and permissions, check downloads, and clear sensitive browsing data on shared computers.