The Internet, DNS, and Hosting

This lesson covers the internet, the Domain Name System (DNS), and web hosting, as required by OCR J277 Section 1.3.2. You need to understand how the internet works and how websites are made accessible to users.

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What Is the Internet?

The internet is a global network of networks — a vast WAN (Wide Area Network) that connects billions of devices worldwide. It uses standardised protocols (agreed rules) to allow different networks and devices to communicate.

Key Points About the Internet

Feature	Detail
Type	The world's largest WAN
Structure	A network of networks — LANs and WANs interconnected via routers
Infrastructure	Fibre optic cables (including undersea), satellites, telephone lines, mobile networks
Protocols	Uses TCP/IP as its fundamental communication protocol
Ownership	No single organisation owns the internet; it is maintained by ISPs and international bodies

The Internet vs The World Wide Web

These terms are often confused but mean different things:

Term	What It Is
The Internet	The physical network infrastructure (cables, routers, servers) that connects devices globally
The World Wide Web (WWW)	A collection of websites and web pages accessed via the internet using web browsers and HTTP/HTTPS

The web is a service that runs on the internet. Other services that use the internet include email (SMTP/IMAP), file transfer (FTP), and video streaming.

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IP Addresses

Every device connected to the internet has an IP (Internet Protocol) address — a unique numerical address that identifies it on the network.

IPv4

Feature	Detail
Format	Four numbers separated by dots (e.g. 192.168.1.1)
Each number	0-255 (8 bits each, 32 bits total)
Total addresses	Approximately 4.3 billion (2^32)
Problem	Running out of addresses due to the number of devices online

IPv6

Feature	Detail
Format	Eight groups of hexadecimal digits (e.g. 2001:0db8:85a3:0000:0000:8a2e:0370:7334)
Total addresses	Approximately 3.4 x 10^38 (2^128) — virtually unlimited
Adoption	Gradually being adopted to replace IPv4

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DNS (Domain Name System)

The DNS is a system that translates domain names (human-readable addresses like www.google.com) into IP addresses (machine-readable addresses like 142.250.187.46).

Why Is DNS Needed?

Humans find it easier to remember domain names (e.g. www.bbc.co.uk) than IP addresses (e.g. 151.101.0.81). DNS acts as the internet's phone book, looking up the IP address associated with a domain name.

How DNS Works

1. A user types a URL (e.g. www.example.com) into their web browser.
2. The browser sends a request to a DNS server asking: "What is the IP address for www.example.com?"
3. The DNS server looks up its records:
   • If it has the record, it returns the IP address directly.
   • If not, it forwards the request to another DNS server (this process may repeat through several servers).
4. The DNS server returns the IP address (e.g. 93.184.216.34) to the browser.
5. The browser uses the IP address to connect to the web server hosting the website.
6. The web server sends the web page back to the browser, which displays it.

sequenceDiagram
  participant U as User Browser
  participant R as DNS Resolver
  participant T as TLD Server (.com)
  participant A as Authoritative DNS
  participant W as Web Server
  U->>R: Lookup www.example.com
  R->>T: Who handles example.com?
  T-->>R: Authoritative server address
  R->>A: IP for www.example.com?
  A-->>R: 93.184.216.34
  R-->>U: 93.184.216.34
  U->>W: HTTP/HTTPS request
  W-->>U: Web page HTML

DNS Hierarchy

Level	Example
Root DNS servers	The top of the DNS hierarchy (13 root server systems worldwide)
Top-Level Domain (TLD) servers	Manage domains like .com, .org, .co.uk
Authoritative DNS servers	Store the actual IP address records for specific domains

OCR Exam Tip: A common exam question asks you to describe how a web page is retrieved. Include DNS (domain name to IP address), the web server, and HTTP/HTTPS in your answer.

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Web Hosting

Web hosting is the service of storing website files on a web server that is connected to the internet, making the website accessible to users 24/7.

How Web Hosting Works

Component	Role
Web server	A powerful computer that stores website files (HTML, CSS, images) and serves them to browsers on request
Domain name	The human-readable address (e.g. www.learningbro.com)
IP address	The numerical address of the web server
DNS	Translates the domain name to the server's IP address
HTTP/HTTPS	The protocol used to transfer web page data between the server and the browser

When a user visits a website:

1. DNS resolves the domain name to an IP address.
2. The browser sends an HTTP/HTTPS request to the web server.
3. The web server processes the request and sends back the web page files.
4. The browser renders (displays) the web page.

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Summary

• The internet is a global network of networks; the web is a service running on the internet (OCR J277 1.3.2).
• IP addresses uniquely identify devices on the internet (IPv4: 32-bit; IPv6: 128-bit).
• DNS translates domain names into IP addresses — the internet's phone book.
• Web hosting stores website files on servers that are always connected to the internet.
• The process: user types URL -> DNS lookup -> IP address returned -> browser connects to web server -> page displayed.

Key Vocabulary: internet, WWW, IP address, IPv4, IPv6, DNS, domain name, web server, web hosting, URL, HTTP, HTTPS.

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Worked Example: From URL to Rendered Web Page

Scenario: A student types https://www.revise-cs.example.org/networks into Chrome and presses Enter. Trace the complete journey from keystroke to fully rendered page, naming every protocol and device involved, and explain what DNS does at each stage. Approximately 350 words.

Model walk-through: