The Internet and the World Wide Web

The Internet

• global networks of networks

• the infrastructure used to provide connectivity to the World Wide Web

World Wide Web

• collection of websites and web pages that are accessed using the internet

• created in 1989 by Tim Burners Lee

• consists of interconnected documents and multimedia files that are stored on web servers around the world

• Web pages are accessed using a web browser, which communicates with web servers to retrieve and display the content

HTML

standard mark-up language for documents designed to be displayed in a web browser. Often assisted by technology such as CSS

Web Browser

• application for accessing websites

• When a user requests a webpage from a particular website, the browser retrieves its files from a web server and then displays the page on the users screen.

URL

• Uniform Resource Locater

• an address to a resource on the internet such as a web page.

Network Hardware

• Gateways

• Routers

• Network bridges

• Network switches

• Repeaters

Gateways

connect 2 networks that have different protocols e.g networks within an organisation such as a school

Routers

• forward data between computer networks

• Home routers forward data between the computer and the internet

Repeaters

• Recieve data and retransmit it

Network switches

• forward data only to devices that need to recieve the data

Network bridges

create a single network from multiple networks

Client - Server Model

• whenever you visit a webpage, your computer is acting as a client and is requesting information which is then provided by the server

• Information then displayed to the user in the form as a webpage by the web browser

• too many clients requesting info - server may slow down/crash e.g Ticketmaster

Communications protocol

• Rules/ procedures for network communcation. An agreed way to communicate between 2 devices e.g computers

• Different protocols used in different layers of the internet

• Application layer - HTTP/HTTPS

• Transfer layer - TCP

• Network - IP

• Physical - Wi - Fi

HTTP

• Hypertext Transfer Protocol

• allows a client to issue a request for a resource such as a webpage and then allows the servers to respond with that requested info

• HTTP is a protocol specific to applications including web browsers and server hosting software

HTTPS

• Hypertext transfer protocol secure

• secure version of HTTP

• automatically encrypts data being transmitted meaning hackers attempting to intercept the information can’t decode it

• Standard for most websites, denoted by a lock next to the URL

TCP

• Transmission Control Protocol

• operates at the transfer layer of a network and ensures binary info is reliably transferred between computers

• Breaks up the information into packets to allow for efficient routing

IP

• Internet Protocol

• operates at a network layer

• handles the creation of data packets and then routs them to their destination

• Does this using an IP address - a unique code that identifies a network or a particular device on that network

• ensures the correct address is attached to every coming from the server and reaches the correct client

VoIP

• Voice over Internet Protocol

• not a single protocol but a number of methods to transfer voice data over the internet

Wi - Fi

• radio wave technology that allows electronic devices such as phones and laptops to communicate with each other and access the Internet wirelessly

• Operates at the physical layer and manages the flow of data around Wi-Fi networks