5.1 The Internet & The World Wide Web
The Internet & WWW
The internet is the global network of computers and other electronic devices connected together through a system of routers and servers.
The WWW is a collection of websites and web pages that are accessed using the internet. It was created in 1989 by Tim Berners-Lee. Web pages are accessed using a web browser which communicated with a web server to retrieve and display content.
URL's
The Uniform Resource Locator is a text-based address that identifies the location of a resource on the internet. It can contain 3 main components:
Protocol This is the communication protocol used to transfer data between the client and the server (e.g. HTTP/S, FTP)
Domain name The name of the server where the resource is located (e.g. an IP address)
Web page / file name The location of the file or resource on the server (e.g. the file or directory name)
Protocols
HTTP/S
Stands for HyperText Transfer Protocol (Secure). It is the protocol used to transfer data between a client and a server. It operates on port 80 and is therefore vulnerable to manipulation and interception. The HTTPS is the secure version with encryption. It operates on port 443 and is harder to intercept.
There are a few ways to check if a website is using HTTPS or not. Check the beginning of the URL and if it starts with http:// then it uses HTTP and if it starts with https:// then it uses HTTPS. Alternatively, you can look for the locked padlock icon 🔒 or you can check the digital certificate of the website.
Sample answer:
Secure HTTP (HyperText Transfer Protocol Secure) Encrypts data for transmission It's a set of rules for data transmission Combines HTTP and SSL / TLS to transmit data
SSL & TLS
SSL is a security protocol developed in the 1990s and TLS is its successor. They use a combination of symmetric and asymmetric encryption to secure data.
SSL operates in the transport layer of the OSI model. The TLS model is made up of the and record layers. The method is as follows:
The browser requests a secure connection to the server
The browser requests the server to identify itself
The server provides a digital certificate
The browser validates the certificate
The browser sends a signal back to the server to begin data transmission
The encryption method is agreed
A session key is generated
You need to know the above method well as it frequently comes up in exam questions
Sample answer (Purpose of the handshake layer):
Carries out authentication of server and client Handles encryption algorithms / keys
Web Browser
It's main purpose is to render HTML and display web pages. It can also record user history, store bookmarks and cookies. They also have an address bar which can run active scripts, download files, and request web pages. They can also manage the different protocols.
Web Pages
This method is followed:
User types URL into the web browser
Browser send the URL to the DNS using HTTP
DNS finds the matching IP address and sends it to the browser
Browser sends a request to server for web pages
Web pages are sent to browser
Browser renders HTML to display pages
Security certificates are exchanged
SSL or HTTPS is used to encrypt the data that is sent
Structure
HTML is used to create the structure of a web page. It written in plain text. It's used in the content layer and tells the browser how to display the page (e.g. where the text is placed, margins, padding).
Presentation
CSS is used to format the page. It is used in the presentation layer and produces a consistent format between different web pages (e.g. font size and colour, background colour).
Cookies
There are two types of cookies:
Session cookies These are temporary and only stored during a browser session.
Persistent cookies Stored for a long period and are used to remember preferences and settings
They are used for various functions such as:
Saving personal details
Tracking user preferences
Storing login details
Displaying ads
Tracking visitor stats
Exam Questions
Last updated