The Internet and the WWW
1. Internet vs. World Wide Web (WWW)
Many people use these terms interchangeably, but in Computer Science, they are distinct entities.
The Hardware/Infrastructure. A massive global network of networks connected via copper wires, fiber optics, and satellites.
The Service/Software. A collection of information (webpages) stored on servers, accessed via the internet using the HTTP protocol.
2. Retrieving a Webpage: HTTP, HTTPS, and Security
HTTP (Hypertext Transfer Protocol) is the set of rules used to transfer files (text, images, video) on the web.
| Protocol | Description |
|---|---|
| HTTP | Data is sent in "Plain Text." Anyone intercepting the data can read it. |
| HTTPS | HTTP Secure. Data is encrypted using SSL or TLS. |
The Role of SSL and TLS
SSL (Secure Sockets Layer) and its successor TLS (Transport Layer Security) provide a secure link between the browser and the server.
- They use Encryption to scramble data so hackers cannot understand it.
- They use Certificates to authenticate that the server is who it claims to be (avoiding "spoofing").
3. The Domain Name System (DNS)
Computers communicate using IP Addresses (e.g., 192.0.2.1), but humans prefer words. The DNS acts as the "Phonebook" of the internet.
- You type
www.google.cominto your browser. - The browser sends a request to a DNS Server.
- The DNS looks up the IP Address for that domain.
- The IP address is sent back to your browser, which then contacts the server directly.
4. Anatomy of a URL
A Uniform Resource Locator is the complete web address used to find a specific resource.
- Protocol: How the data is sent (HTTP/HTTPS).
- Domain Name: The name of the server/website.
- Path: The specific folder on the server.
- Filename: The actual web page or image file.
5. Features of a Web Browser
A browser is an application software that renders HTML code into the visual webpage you see.
The browser requests a page using a URL. The DNS finds the IP Address. The server sends HTML files via HTTPS, which uses TLS/SSL for encryption. The browser then renders the code for the user.