The Internet, the World Wide Web, URLs & HTTP(S)

Syllabus & Goals 3 min

Cambridge 5.1 · The internet and the World Wide Web Paper 1 · Computer Systems

By the end of this lesson you can:

1. Explain the differences between the internet and the World Wide Web.
2. Break a URL into its protocol, domain name and file name.
3. Describe the purpose and operation of HTTP and HTTPS.

Textbook: Chapter 5, §5.1.1–5.1.3 (pp. 180–181)

Recap / Warm-Up 5 min

In Unit 2 you split data into packets and sent them across networks. In Unit 3 you met routers and IP addresses. Unit 5 asks what we actually do with all those connected networks.

Quick starter

Sam sends an email, then reads a news page in a browser. Which of the two activities uses the World Wide Web?

Key Concept 14 min

1 · The internet is not the same as the World Wide Web

The word internet comes from INTERconnected NETwork. It is a worldwide collection of networks and devices joined together. It relies on physical infrastructure: cables, routers, satellites and servers. It moves data using the TCP/IP protocols.

The World Wide Web (WWW) is only one part of what runs on the internet. It is a massive collection of web pages and other resources stored on web servers. You reach it with a web browser, using URLs and the HTTP/HTTPS protocols.

2 · Uniform resource locators (URLs)

Every web page has a text address called a URL. You type it into the browser's address bar. Text is easier to remember than a numeric IP address. The format is:

protocol://website address/path/file name

• Protocol — usually http or https.
• Website address — the domain host (www), the domain name (the website's name), the domain type (.com, .org, .net, .gov) and sometimes a country code (.uk, .de).
• Path — the folder or web page on the site. If it is left out, you land in the site's root directory, usually the home page.
• File name — the item on the web page (for example tickets.html).

3 · HTTP and HTTPS

Hypertext transfer protocol (HTTP) is a set of rules that must be obeyed when files are transferred across the internet. A browser and a web server both follow it, so they understand each other.

How it operates, in outline:

1. The browser sends an HTTP request to the web server, asking for a page.
2. The web server finds the files and sends an HTTP response containing them (HTML, images and so on).
3. The browser receives the files and displays the page.

HTTPS is HTTP with security added, using SSL (or its newer version, TLS). The s means secure. Data sent between browser and server is encrypted, and the website is authenticated. Browsers show a padlock next to the address.

Worked Example 12 min

(a) Break down a URL

Question: for the URL https://www.cityfarm.org.uk/visit/opening-times.html, identify the protocol, domain name, domain type, country code and file name.

1. Read up to ://. The protocol is https.everything before "://" is always the protocol.
2. Take the text between :// and the first /: www.cityfarm.org.uk. This is the whole website address.the first single slash marks where the path begins.
3. Split the website address at the dots: www · cityfarm · org · uk.each dot separates one part of the address.
4. Name each part: host www, domain name cityfarm, domain type .org, country code .uk.the name identifies the organisation; .org and .uk describe its type and country.
5. After the address comes the path /visit and the file name opening-times.html.the last item after the final slash is the file requested.

How the marks are earned: one mark per correctly named part. Writing www.cityfarm.org.uk for "domain name" usually gets no mark — the question wants the name part only (cityfarm). Some mark schemes also accept cityfarm.org.uk.

(b) Internet or World Wide Web?

Question: tick whether each feature belongs to the internet or the WWW.

Method: ask "is this about the connections (internet) or about pages and browsers (web)?" One mark per correct row.

(c) Which protocol should the page use?

Question: a library's website has a page where members log in. Explain why it should use HTTPS rather than HTTP. [3]

1. Identify the risk: a login page sends a user name and password. the answer must be about this page, not HTTPS in general.
2. Say what HTTPS adds: SSL/TLS encrypts the data between browser and server. this is the key feature examiners look for.
3. Give the effect: if the data is intercepted it cannot be understood, so the password stays private. "explain" needs the consequence, not just the feature.
4. Add authentication: HTTPS lets the browser check that the site is genuine (padlock shown). a separate, creditable point.

Try It Yourself 12 min

📝 Exam Practice 10 min

Recap & Key Terms 3 min

The internet is the global network of networks. The web is the collection of pages that travels over it. A URL names a page as protocol, website address, path and file name. HTTP sets the rules for transferring pages; HTTPS adds SSL encryption.

Internet

The worldwide interconnection of networks; it uses TCP and IP protocols.

World Wide Web (WWW)

A massive collection of web pages, based on the hypertext transfer protocols (HTTP and HTTPS).

Uniform resource locator (URL)

A text-based address for a web page.

Hypertext transfer protocol (HTTP)

A set of rules that must be obeyed when transferring files across the internet.

HTTPS

HTTP with extra security (such as SSL) applied; data is encrypted.

HTML

The language used to design, display and format web pages.

Homework 1 min

Task (≤ 15 min): a student writes, "The internet and the World Wide Web are the same thing, and HTTPS is just a faster HTTP." Explain the two mistakes in the statement. [4]