✓ Free · Component 1 · 1.3.4 The Internet
1.3.4a The Internet, World Wide Web and DNS
OCR H446 · A Level Computer Science · ~12 min read
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The Internet vs the World Wide Web

These two terms are often confused but refer to fundamentally different things:

InternetWorld Wide Web (WWW)
DefinitionThe global physical infrastructure — millions of interconnected computers, routers, cables, and wireless links spanning the planet.A service that runs ON the internet — the collection of web pages and websites accessed via HTTP/HTTPS using web browsers.
AnalogyThe road networkThe cars that drive on it
ProtocolTCP/IP (the base protocol)HTTP/HTTPS
Created byARPANET (US DoD, 1969)Tim Berners-Lee (1989)

Other services also run on the Internet but are NOT part of the WWW: email (SMTP/IMAP), file transfer (FTP), VoIP (video calls), streaming, online gaming.

URLs and the Structure of the Web

A URL (Uniform Resource Locator) is the complete address of a resource on the web. Structure:

https://www.cszone.co.uk/ocr-h446/1-3-4a/

  • Protocol: https — how to access the resource
  • Subdomain: www — a subdomain of the domain
  • Domain name: cszone.co.uk — the human-readable address
  • Path: /ocr-h446/1-3-4a/ — the specific resource on the server

A URI (Uniform Resource Identifier) is the broader concept — a URL is a type of URI that also specifies the location and how to retrieve it.

Domain Name System (DNS)

Computers communicate using IP addresses (e.g. 104.21.8.51), but humans use domain names (e.g. cszone.co.uk). DNS is the system that translates domain names into IP addresses — it is often called the "phone book of the internet".

DNS Resolution Process

When you type www.cszone.co.uk into a browser:

  1. Local cache check: the operating system checks its own DNS cache — if it has recently resolved this domain, it uses the cached IP.
  2. Recursive resolver (ISP DNS): if not cached, the query is sent to the ISP's recursive resolver (DNS server). This server does the searching on behalf of your device.
  3. Root name server: the recursive resolver contacts a root name server (there are 13 sets worldwide). The root doesn't know the IP but knows which TLD name servers handle .uk.
  4. TLD name server: the TLD name server for .co.uk knows which authoritative name server holds the record for cszone.co.uk.
  5. Authoritative name server: this server holds the actual DNS record and returns the IP address.
  6. Result returned: the IP is returned to the device; the browser connects to the web server at that IP. The result is also cached locally.

DNS Record Types

Record TypePurposeExample
A recordMaps a domain to an IPv4 addresscszone.co.uk → 104.21.8.51
AAAA recordMaps a domain to an IPv6 addresscszone.co.uk → 2606:4700::...
MX recordMail exchange — specifies mail server for domaincszone.co.uk → mail.cszone.co.uk
CNAME recordAlias — maps one domain name to anotherwww.cszone.co.uk → cszone.co.uk
NS recordSpecifies the authoritative name servers for the domaincszone.co.uk → ns1.cloudflare.com

ISPs and Internet Access

An ISP (Internet Service Provider) provides internet connectivity — typically BT, Virgin Media, Sky (in the UK). Your router connects to the ISP's network, which connects to the wider internet.

ISPs also typically provide DNS resolvers that clients use by default. Alternative public DNS servers: Google (8.8.8.8), Cloudflare (1.1.1.1).

The Role of ICANN

ICANN (Internet Corporation for Assigned Names and Numbers) is the non-profit organisation that manages the global DNS infrastructure — it coordinates IP address allocation and TLD management, ensuring global uniqueness of domain names and IP addresses.

Exam tip: The most tested concept here is the DNS resolution process. Know the order: local cache → recursive resolver → root name server → TLD name server → authoritative name server → IP returned. Be able to explain each step and why caching is used (to reduce traffic and speed up repeated requests).
Exam tip: The Internet ≠ the World Wide Web. The Internet is the physical network infrastructure; the WWW is a service (web pages accessed via HTTP/HTTPS) that runs on top of it. Tim Berners-Lee invented the WWW in 1989, not the Internet.
⚠ Common Mistakes
  • Saying "the internet was invented by Tim Berners-Lee" — Tim Berners-Lee invented the World Wide Web (1989). The internet's origins trace to ARPANET (1969). They are different things.
  • Confusing URL and IP address — a URL is the human-readable address like cszone.co.uk. An IP address is the numeric address like 104.21.8.51. DNS translates between them.
  • Saying DNS checks the root server first — the local cache and recursive resolver are checked BEFORE the root server. Caching means most lookups never reach the root servers.
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Worksheet — 1.3.4a The Internet & DNS

8 questions · 20 marks · instantly marked

Q1Explain the difference between the Internet and the World Wide Web. Why are they often confused?[4 marks]
✓ Mark scheme
Internet: the global physical infrastructure — millions of interconnected computers, routers, cables, and wireless links spanning the planet; uses TCP/IP as its base protocol; its origins trace back to ARPANET (1969) [1]. World Wide Web (WWW): a service that runs ON the internet — the collection of web pages and websites accessed via HTTP/HTTPS using web browsers; invented by Tim Berners-Lee in 1989 [1]. They are often confused because most everyday internet use involves web browsing — but other services (email, FTP, VoIP, streaming) also run on the Internet without being part of the WWW [1]. Analogy: the internet is the road network; the WWW is the cars that drive on it — the roads exist independently of the cars [1].
Q2Describe each component of this URL: https://www.cszone.co.uk/dashboard/[4 marks]
✓ Mark scheme
https — the protocol; HTTPS (Hyper Text Transfer Protocol Secure) specifies how the browser should retrieve the resource; the 'S' means the connection is encrypted using TLS [1]; www — a subdomain of the main domain [1]; cszone.co.uk — the domain name; the human-readable address of the server; DNS will translate this to an IP address [1]; /dashboard/ — the path; specifies the particular resource or page to be retrieved on the web server [1].
Q3Explain the purpose of DNS and why it is necessary for the internet to function.[3 marks]
✓ Mark scheme
DNS (Domain Name System) translates human-readable domain names (e.g. cszone.co.uk) into IP addresses (e.g. 104.21.8.51) that computers use to communicate [1]; it is necessary because computers route packets using IP addresses — they cannot directly interpret domain names — but humans cannot realistically remember numeric IP addresses for every website [1]; DNS provides a distributed, hierarchical lookup system so any domain can be resolved globally without a single centralised database [1].
Q4Describe the DNS resolution process when a user types www.example.com into their browser for the first time.[5 marks]
✓ Mark scheme
1. Local cache checked — not found (first time) [1]; 2. Query sent to ISP's recursive resolver (DNS server) [1]; 3. Recursive resolver queries a root name server — root returns the address of the TLD name server for .com [1]; 4. Recursive resolver queries the TLD name server for .com — TLD returns the address of the authoritative name server for example.com [1]; 5. Recursive resolver queries the authoritative name server — it returns the actual IP address of www.example.com; IP is returned to the browser and cached for future requests [1].
Q5Why is DNS caching important? What would happen if every DNS query had to go through the full resolution process?[2 marks]
✓ Mark scheme
Caching stores recently resolved domain-to-IP mappings locally; subsequent visits to the same site resolve immediately without querying any DNS server [1]; without caching, every single request would require a full resolution chain — enormously increasing traffic to root and TLD servers, slowing down browsing, and potentially overwhelming the root server infrastructure [1].
Q6Explain the difference between an A record and a CNAME record in DNS.[2 marks]
✓ Mark scheme
A record (Address record): directly maps a domain name to an IPv4 address — e.g. cszone.co.uk → 104.21.8.51 [1]. CNAME record (Canonical Name): creates an alias — maps one domain name to another domain name (not directly to an IP) — e.g. www.cszone.co.uk → cszone.co.uk, which is then resolved separately. Useful when multiple domain names should point to the same server [1].
Q7What is an ISP? What role does an ISP play in DNS resolution?[2 marks]
✓ Mark scheme
ISP (Internet Service Provider): provides internet connectivity to households and businesses (e.g. BT, Virgin Media, Sky) [1]. Role in DNS: ISPs typically operate recursive resolver (DNS) servers that clients use by default — when a device makes a DNS query, it is sent to the ISP's DNS server, which then performs the full resolution on the device's behalf [1].
Q8Give ONE other service (besides the World Wide Web) that runs on the Internet and state the protocol it uses.[1 mark]
✓ Mark scheme
Any one from: Email (SMTP for sending, IMAP/POP3 for receiving) [1]; File transfer (FTP — File Transfer Protocol) [1]; VoIP / video calls (uses SIP, RTP) [1]; Streaming (uses RTMP, HLS) [1].
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