Internet Fundamentals/Introduction

The Internet

The Internet is a global Wide Area Network (WAN).
- A Network is a group of interconnected devices.
- A Wide Area Network (WAN) is a network that covers a large area.
- A Local Area Network (LAN) is a network that covers a small area.

Threat to personal information : possible loss of name, address, credit card number,...
Spamming : unwanted Emails that serve no purpose.
Cybercrime : malware, ransomware, stealing of identities,...
Virus attacks : cause a system to crash and may delete important data.

In the 1950s, the United States Defense Department formed the Advanced Research Projects Agency (ARPA) with the purpose of developing technology.
ARPA’s scientists could not easily communicate or share information, so they created a network of computers, which they called ARPAnet.
In the 1970s, the TCP/IP protocol was developed, this protocol allowed the separate networks to communicate with each other.
The joining of these networks created a huge WAN which came to be known as the Internet.

The World Wide Web (WWW) is a collection of different websites that can be accessed through a web browser.
- A website is a group of webpages hosted on one web server.
- A web server is an Internet server that serves webpages to the web browser.
- A web browser is an application that displays webpages.

When a user makes a request over the Internet, the web browser sends this request to a web server, and the web server accepts and responds to it by storing and transferring webpages to the web browser.

Any resource connected to the WWW is identified by its Uniform Resource Locator (URL).
- A Uniform Resource Locator (URL) is the address of a WWW page.
- Example : http://www.example.com/...
When the URL of a web page is identified, a protocol called Hyper Text Transfer Protocol (HTTP) sends a command to the web server.
- Hyper Text Transfer Protocol (HTTP) is a protocol which enables communication between web clients and web servers.
Once the web server has transmitted the requested page, the web page can be displayed with Hyper Text Markup Language (HTML).
- Hypertext Markup Language (HTML) is the standard language for creating and displaying web pages.

In 1990, the WWW was invented by Tim Berners-Lee.
He created three technologies (HTML, URL and HTTP), which allowed to use the Internet to link one document directly to another.

Internet Service Provider (ISP) : a business that provides a connection to the Internet.
Modem : a piece of hardware that allows a device to connect to the Internet over a telephone line.
Router : a piece of hardware that allows several devices to connect to a single Internet connection.

Dial-up : an Internet connection which uses a telephone line and requires a landline.
Digital Subscriber Line (DSL) : an Internet connection which uses a telephone line, but doesn’t require a landline.
Cable TV : a wired Internet connection which uses Cable TV lines.
Wi-Fi : a wireless Internet connection which uses radio waves.
Satellite : a wireless Internet connection which uses satellites orbiting the Earth.
3G, 4G, and 5G : wireless Internet connections which uses cellular networks.

Cloud computing is the process of storing and using services online, rather than storing them locally on a device.