Stretch tasks The internet and the web

Round 1: Quiz Blitz

1. False The internet is the global network. The web is one service that runs on it, made of linked pages.
2. An email sent from a mail app Email, streaming and online games run on the internet without being web pages.
3. You type the address into a browser → DNS looks up the IP address → Your computer sends a request to that IP address → The server sends the page back in packets → The packets are reassembled and the page is shown Name to number, request, reply in packets, reassemble. It usually takes well under a second.
4. Turns a web address into an IP address Computers route data by number, so a name such as example.com has to be looked up first.
5. The destination address; The sender's address; A packet number Each packet holds part of the data, where it is going, where it came from and its number.
6. So they can be put back in order when they arrive Packets can arrive out of order. The numbers let the receiving computer reassemble them.
7. Only that packet is sent again This is one of the big advantages of packets: a loss costs one small resend.
8. HTTPS The S stands for secure: intercepted data cannot be read.
9. SMTP SMTP sends email; IMAP is used to fetch it from the server.
10. domain name system The Domain Name System: the internet's phone book.
11. True Routers send each packet the best way available at that moment, so routes can differ.
12. A set of rules for how data is sent Protocols are agreed rules, so that different devices can understand each other.

Round 2: Quick Fire

1. • The internet is the global network of connected computers
   • The web is a service on the internet, made of linked web pages
   Model answer

   The internet is the global network of connected computers and the cables between them. The World Wide Web is one service that runs on the internet, made of web pages linked together.

2. • Computers find each other using IP addresses, which are numbers
   • People use names, so DNS translates a name into its IP address
   Model answer

   Computers send data to IP addresses, which are numbers. People find names much easier to remember, so DNS translates a name such as bbc.co.uk into its IP address.

3. • One large file cannot block the network
   • Only lost packets need resending
   • Packets can take the fastest available routes
   Model answer

   Splitting data up means one large file cannot block the network for everyone else, and if a packet is lost only that packet needs to be resent, not the whole file.

4. • HTTPS encrypts the data
   • So if it is intercepted it cannot be read
   Model answer

   HTTPS encrypts the data as it travels, so even if someone intercepts it, the password cannot be read.

Round 3: Big Think

1. • A DNS server looks up the IP address for the name
   • A request is sent to the web server at that address
   • The server sends the page back split into packets
   • Packets may take different routes and arrive out of order
   • The packets are reassembled in order and the browser displays the page
   Model answer

   First the computer asks a DNS server to look up the IP address for bbc.co.uk. It then sends a request to the web server at that IP address. The server sends the page back split into packets, which may take different routes and arrive out of order. The computer reassembles them in order using their packet numbers, and the browser displays the page.

2. • Many devices are sharing the same connection
   • Packets are delayed or lost and have to be resent
   • The Wi-Fi signal is weakened by distance or walls
   • Other networks or devices cause interference
   • Fix: use a wired connection
   • Fix: move closer to the router, or add an access point or booster
   • Fix: pause other downloads and streams
   Model answer

   Video calls need a steady flow of packets. On a crowded network many devices are sharing the same connection, so packets are delayed or lost and have to be resent, and the picture freezes while it waits. The Wi-Fi signal may also be weak because the laptop is far from the router or behind thick walls, and neighbouring networks can cause interference. Fixes include using a wired cable to the router, moving closer to the router or adding an access point or booster, and pausing other downloads and streaming while the call is on.

This or That

1. Data is sent to numbers, not names DNS turns a name such as www.example.com into the IP address that the data is actually sent to.
2. Its IP address An IP address identifies a device. DNS is the service that looks addresses up.
3. HTTPS HTTPS encrypts the data, so an intercepted password cannot be read.
4. IMAP SMTP sends email. IMAP retrieves it.
5. So one large file cannot block the network Small packets share the network fairly, and each one still carries its destination and sender addresses.
6. TCP/IP TCP/IP addresses the packets and checks they all arrive. HTTP transfers web pages on top of it.
7. The page, split into packets DNS gives you the IP address. The web server sends the page itself, in packets.
8. www.example.com IP addresses are numbers. A domain name is the human-friendly name that DNS looks up.

Memory Match

• A 6 DNS: Looks up the IP address for a domain name
• B 4 IP address: A number that identifies a device on a network
• C 5 Packet: A small piece of data with addresses and a number
• D 2 HTTPS: Transfers web pages with encryption
• E 1 SMTP: Sends email
• F 3 IMAP: Retrieves email from the server