Topic 4b – The Internet and the World Wide Web

You use it every day. Now let's understand what it actually is.

Learning Objectives

By the end of this topic, you should be able to:

Learning Activities

To help you meet the learning objectives, we have prepared a combination of readings, activities, and videos.

Course Readings

These reading were designed to introduce the course topics to an audience of educators. They should be considered "required" and read in order.

Supplemental Readings

Some participants find it helpful to read about a topic from a source written for a slightly more technical audience. These supplemental readings cover similar material as the course readings but may not fully align with the course learning objectives. Use them as an optional complement to your study, not a substitute for the course readings.

Lesson Videos

These videos support the readings above and may present the material with some deeper connections and worked examples.

Checking for Understanding, Questions

The Internet and Its Structure

  1. A student says: "I use the Internet to browse the Web, check email, and play online games." Which of those activities use the Internet? Which ones use the Web specifically? How would you clarify the distinction?
  2. Your school's network connects all classrooms, offices, and labs to a central server and to the Internet through a local provider. Which parts of this system are the LAN, the intranet, and the connection to the Internet? Where does the access ISP fit in?
  3. Explain the role of tier-1 ISPs in the Internet's structure. Why does their redundancy matter?
  4. What is an intranet? How is it different from the Internet? Give an example of something that might be accessible on a school intranet but not on the public Internet.

Addressing and DNS

  1. Every device on the Internet has an IP address. What is the purpose of IP addresses, and how does ICANN relate to how they are assigned?
  2. What is a top-level domain? Identify the TLD in each of the following and describe what it tells you about the organization: uni.edu, whitehouse.gov, redcross.org, amazon.com.
  3. Explain what DNS does in plain language. Walk through what happens between the moment you type wikipedia.org into your browser and the moment the page begins to load. Where does DNS fit in that sequence?

The Web and URLs

  1. For the following URL, identify the protocol, domain name, directory path, and document name: https://cs.uni.edu/courses/intro/syllabus.html
  2. What is HTTP? What does HTTPS add, and how do you know when a browser is using it?
  3. What is HTML, and what role does it play in displaying a webpage? What is the relationship between the HTML source code and what you see in the browser?
  4. Explain the roles of the browser and the web server in loading a webpage. Which one is the client and which is the server? What does each one do?

Applications and Servers

  1. Identify three Internet applications other than the Web and briefly explain how each one works and what protocol it uses.
  2. What is the difference between POP3 and IMAP for email retrieval? Which one would be more useful for a teacher who checks email on both a school computer and a personal phone?
  3. Identify three types of Internet servers and explain what each one does. For each server type, give a specific example a K–12 teacher would recognize from daily use.
  4. What is a CDN, and why do streaming services need them? How does a CDN connect to the distributed computing concepts from Topic 4a?

Checking for Understanding, Answers

Compare your answers to the following answer key.

Show Answer Key

The Internet and Its Structure

  1. All three activities use the Internet (the underlying global network of networks). Only browsing the Web uses the Web specifically — the Web is the collection of websites and pages accessible via HTTP/HTTPS through a browser. Email uses the Internet but uses its own protocols (SMTP, IMAP, POP3), not the Web. Online games also use the Internet but communicate via their own protocols, not HTTP. The Internet is the infrastructure; the Web is one application that runs on top of it.
  2. The computers, servers, and devices within the school building form the LAN. The school's internal websites, shared drives, and services accessible only to people on-site form the intranet. The connection from the school to the broader Internet via a local provider is the WAN link. The company providing that connection is the school's access ISP — it connects the school's network to the higher tiers of the Internet hierarchy.
  3. Tier-1 ISPs form the backbone of the Internet — they own and operate the long-haul fiber cables that carry traffic between cities, countries, and continents. They interconnect with each other through peering agreements (exchanging traffic without payment), forming the core mesh that everything else connects to. Their redundancy matters because multiple independent paths exist between any two points on the Internet — if one backbone link or ISP fails, traffic reroutes around it. This is by design; the Internet was originally conceived to survive partial failures.
  4. An intranet is a private network that uses Internet technologies (TCP/IP, web browsers, HTTP) but is accessible only to authorized users within an organization — not the public Internet. It differs from the Internet in that access is restricted and content is internal. Example: a school intranet might host the staff handbook, grade reporting tools, substitute teacher request forms, or an internal calendar — resources that should not be publicly visible.

Addressing and DNS

  1. An IP address is a numerical label assigned to every device on a network to uniquely identify it and enable routing of traffic to it. ICANN (Internet Corporation for Assigned Names and Numbers) is the non-profit organization responsible for coordinating the global allocation of IP address blocks — it delegates large blocks to regional registries (like ARIN for North America), which in turn allocate smaller blocks to ISPs and organizations.
  2. A top-level domain (TLD) is the rightmost segment of a domain name, after the last dot. TLDs in these examples: .edu (educational institutions, predominantly US universities — UNI is a university); .gov (US government agencies — the White House is a government entity); .org (originally non-profit organizations — Red Cross is a humanitarian organization); .com (commercial businesses — Amazon is a commercial company).
  3. DNS (Domain Name System) is essentially the Internet's phone book: it translates human-readable domain names into the numerical IP addresses computers use to route traffic. When you type wikipedia.org: (1) your browser checks its local cache; (2) if not cached, it asks your operating system, which asks your configured DNS resolver (usually provided by your ISP or a service like Google); (3) the resolver queries the DNS hierarchy, starting from root servers, to find the IP address associated with wikipedia.org; (4) the IP address is returned to your browser; (5) your browser then sends an HTTP request to that IP address. DNS happens before any web content is fetched.

The Web and URLs

  1. For https://cs.uni.edu/courses/intro/syllabus.html:
    Protocol: https
    Domain name: cs.uni.edu
    Directory path: /courses/intro/
    Document name: syllabus.html
  2. HTTP (Hypertext Transfer Protocol) is the protocol browsers and web servers use to request and deliver web pages — it defines the format of requests ("GET this page") and responses ("here is the HTML"). HTTPS adds encryption via TLS (Transport Layer Security), so the content of the exchange cannot be read by anyone intercepting the network traffic. You know a browser is using HTTPS when the URL begins with https:// and a padlock icon appears in the browser's address bar.
  3. HTML (Hypertext Markup Language) is the language used to describe the structure and content of a web page — it uses tags like <h1>, <p>, and <a> to mark up text. The browser downloads the HTML source code from the server and renders it: interpreting the tags and producing the visual display the user sees. The same HTML source may look slightly different in different browsers, but the underlying content is the same.
  4. The browser is the client: it sends an HTTP request to a specific IP address (found via DNS) asking for a particular page. The web server is the server: it receives the request, locates the requested file (HTML, images, etc.), and sends them back to the browser. The browser then renders the received files into a visual page. The server does not initiate communication — it only responds to requests.

Applications and Servers

  1. Three Internet applications (many valid answers): Email — uses SMTP to send messages, IMAP or POP3 to retrieve them; messages are relayed through mail servers. VoIP (Voice over IP) — converts audio into digital packets and sends them over the Internet; uses protocols like SIP and RTP; examples include Google Meet and Zoom audio. DNS — uses the DNS protocol (typically over UDP port 53) to translate domain names to IP addresses.
  2. POP3 (Post Office Protocol 3) downloads email from the server to your device and (by default) deletes it from the server. Your messages exist on one device only. IMAP (Internet Message Access Protocol) syncs email between the server and all your devices — messages remain on the server and your read/unread/folder status is synchronized everywhere. A teacher checking email on both a school computer and a personal phone should use IMAP: all messages and actions will appear consistently on both devices.
  3. Three Internet server types: Web server — hosts and delivers web pages via HTTP/HTTPS; example: the server hosting your school district's website. Mail server — sends, receives, and stores email; example: the server handling your school's staff email. DNS server — resolves domain names to IP addresses; example: the DNS resolver your school's network uses every time a browser loads a new website.
  4. A CDN (Content Delivery Network) is a distributed network of servers geographically spread around the world, each caching copies of popular content. When you request a video or webpage, the CDN routes your request to the nearest server, reducing latency. Streaming services need CDNs because sending all video traffic from a single data center would be impossibly slow for users far away and would create a bottleneck. A CDN is an application of the cluster/distributed computing concepts from Topic 4a — multiple coordinated servers work together to serve content, with geographic distribution replacing fault tolerance as the primary design goal.

Extend Your Learning

The following resources go a little deeper on topics we touched on but did not fully explore in the readings. These are entirely optional — none of this material appears on the Competency Demo — but each one is a natural "next question" from something covered this week.

  • IPv6 and the address exhaustion problem
    The original IP addressing system (IPv4) provided about 4.3 billion unique addresses — a number that seemed enormous in the 1970s but has been exhausted by the explosion of connected devices. IPv6 expands the address space to 340 undecillion addresses. This article from ARIN covers why the transition took so long and where it stands today.
    IPv6 Resource Guide — ARIN
  • The Internet of Things (IoT)
    The Internet now connects far more than computers and phones. Smart thermostats, security cameras, medical devices, and vehicles are all becoming Internet-connected end systems. This overview from IBM explains what IoT is, what it enables, and what the security and privacy implications are — increasingly relevant for school environments with connected devices.
    What is the Internet of Things? — IBM
  • Net neutrality
    The Internet's design treats all traffic equally. Net neutrality is the principle that ISPs should maintain this equality rather than creating "fast lanes" for some content. This overview from the Electronic Frontier Foundation explains the debate, what is at stake, and the arguments on each side.
    Net Neutrality — Electronic Frontier Foundation
  • How HTTPS actually works
    HTTPS encrypts the connection between a browser and a web server using TLS. The underlying mechanism involves public-key cryptography — a browser and server agree on an encryption key without ever having communicated before. This article from Cloudflare covers how TLS handshakes work in plain language.
    What Happens in a TLS Handshake? — Cloudflare