Year 7 · Autumn 2

Networks · Lesson 5 of 5

Internet vs web: DNS and browsers

TheoryTopic 15 Networks and the internetTopic 16 The web

Year 7 · Networks · Lesson 5 of 5

You will learn to

  • Explain why the internet and the web are not the same thing.
  • Describe what DNS does, step by step, when you type a web address.
  • Identify the protocol, domain and path in a URL.

Year 7 · Networks · Lesson 5 of 5

Success criteria

You have got it when you can say:

  • I can name one internet service that is not the web, like email.
  • I can put the steps of a web request in the right order.
  • I can take a URL apart and name each part.

Year 7 · Networks · Lesson 5 of 5

Retrieval starter

Questions from before. Write your answers, then show them.

  1. Last lesson

    Which turns www.bbc.co.uk into an IP address?

    A DNSB HTTPC SMTP

    A. DNS

  2. Last unit

    Copyright in the UK…

    A Must be registeredB Is automatic

    B. Is automatic

  3. Earlier this unit

    A microphone hearing your voice is…

    A InputB OutputC Process

    A. Input

Year 7 · Networks · Lesson 5 of 5

Key words (1 of 3)

DNS
Domain Name System: turns website names into IP addresses.
URL
The full web address of something online.
LAN / WAN
Local Area Network: a network over a small area.
Router
Connects different networks and forwards packets.

Year 7 · Networks · Lesson 5 of 5

Key words (2 of 3)

IP address
A device's address on a network. IPv4 = 4 bytes.
MAC address
Fixed unique ID of a network card. 48 bits in hex.
Packet
A small numbered chunk of data sent across a network.
Protocol
A set of agreed rules for communication.

Year 7 · Networks · Lesson 5 of 5

Key words (3 of 3)

Bandwidth / latency
How much data a connection can carry per second.
HTML
Markup language for the content of web pages.
CSS
Language that styles how web pages look.

The explanation · step 1 of 3

DNS: the internet's phone book

  1. You type www.bbc.co.uk.
  2. Your browser asks a DNS server for its IP address.
  3. If it doesn't know, it asks other DNS servers.
  4. The IP address comes back.
  5. Your browser contacts that address directly.

The explanation · step 2 of 3

Internet vs the web

  • Internet = the physical network: cables, routers, satellites.
  • World Wide Web = one service on it: linked pages in a browser. Email and games use the internet but aren't the web.

The explanation · step 3 of 3

Reading a URL

A URL is the full address of one thing on the web: https://www.bbc.co.uk/news/technology?page=2

PartExampleMeaning
Protocolhttps://Which rules. The s means encrypted
Domainwww.bbc.co.ukWhich server. DNS turns it into an IP address
Top-level domain.co.ukCountry or type (.uk, .es, .com)
Path/news/technologyWhich page on the server
Query?page=2Extra information for the page

Year 7 · Networks · Lesson 5 of 5

Try it: Take a URL apart

Year 7 · Networks · Lesson 5 of 5

Quick quiz · 1 of 3

In a star network the central switch breaks. What happens?

  1. A Data finds another route
  2. B Only one device drops off
  3. C Every device loses the network

C. Every device loses the network

The switch is a single point of failure: everything goes through it.

Year 7 · Networks · Lesson 5 of 5

Quick quiz · 2 of 3

Which protocol checks every packet arrived and asks again for missing ones?

  1. A FTP
  2. B TCP
  3. C IP

B. TCP

TCP (transport layer) numbers packets and resends lost ones. IP just addresses and routes them.

Year 7 · Networks · Lesson 5 of 5

Quick quiz · 3 of 3

A game feels laggy, but big downloads are fast. The problem is most likely…

  1. A High latency
  2. B Low bandwidth
  3. C Too many IP addresses

A. High latency

Game moves are tiny, so the waiting time (latency) matters, not the lanes (bandwidth).

Year 7 · Networks · Lesson 5 of 5

Exit ticket

Answer on paper before you go. Then check.

  1. A 400 MB file on a 100 Mbps line takes at best…

    A 32 secondsB 40 secondsC 4 seconds

    A. 32 seconds 400 × 8 = 3,200 megabits. 3,200 ÷ 100 = 32 seconds.

  2. In https://www.bbc.co.uk/news, the path is…

    A /newsB www.bbc.co.ukC https://

    A. /news The path comes after the domain. It says which page on that server.

Year 7 · Networks · Lesson 5 of 5

Homework and the challenge

Homework

Study page 15 to step 8; download-time formula with your own numbers.

End-of-unit challenge

Draw and annotate the journey of a web-page request, then a short quiz.