Year 10 Digital Technologies · Digital Systems · 12m read

Networks — Protocols, TCP/IP and How the Internet Works

When you load a video, data hops across dozens of networks in milliseconds. Protocols are the shared rules that make it work.

Learning objective: Explain how data travels across networks using protocols and the TCP/IP model.

By the end of this lesson you can:

• I can describe network types and hardware.
• I can explain packets and protocols.
• I can describe the TCP/IP layers.

Packets are postcards. Big files are cut into numbered postcards (packets), each addressed with an IP, sent along different roads (routers) and reassembled in order at the destination.

Networks — Protocols, TCP/IP and How the Internet Works

NETWORK TYPES:
• LAN, WAN, PAN; wired vs wireless.

HARDWARE:
• Router (between networks), switch (within a LAN), wireless access point, modem.

PACKET SWITCHING:
• Data split into packets with headers (source, destination, sequence); reassembled at destination.

PROTOCOLS:
• IP (addressing and routing), TCP (reliable delivery, ordering), UDP (fast, no guarantees — streaming, games), HTTP/HTTPS (web), DNS (domain names to IP addresses), SMTP/IMAP (email).

TCP / IP MODEL LAYERS:
• Application → Transport → Internet → Network access (link).

| Layer (TCP/IP) | Job | Example protocols |
|---|---|---|
| Application | Services for users | HTTP/HTTPS, DNS, SMTP |
| Transport | Reliable delivery, ports | TCP, UDP |
| Internet | Addressing and routing | IP |
| Link | Physical transmission | Ethernet, Wi-Fi |

Key ideas at a glance

• DNS = internet phonebook: Names → IP addresses.
• TCP reliable, UDP fast: Trade-off.
• HTTPS encrypts: TLS.
• Routers forward packets: Best path.

Worked example (Medium)

What happens when you type a website address?

1. DNS. Domain name converted to an IP address.
2. Request. HTTPS request sent in packets via TCP/IP.
3. Response. Server sends packets back; browser reassembles and displays the page.

Answer: DNS lookup, then HTTPS request/response in packets.

Worked example (Hard)

Trace what happens when you type a URL.

1. DNS. Look up IP address.
2. Connection. TCP handshake; TLS for HTTPS.
3. Request. HTTP GET sent in packets.
4. Response. Server sends page; browser renders.

Answer: DNS → TCP/TLS → HTTP request → response → render.

Common mistakes

• Confusing switches and routers Switches connect devices in a LAN; routers connect networks. Fix: Learn each device's role.

Practice questions

1. Which protocol converts domain names to IP addresses?

   1. HTTP
   2. DNS
   3. SMTP
   4. UDP

   (1 marks)

2. Why might a video call use UDP rather than TCP?

   (2 marks)

3. Which protocol suits live video calls?

   1. TCP
   2. UDP
   3. SMTP
   4. FTP

   (1 marks)

4. Explain the role of DNS.

   (2 marks)

Summary

• LAN/WAN and network hardware.
• Packets and protocols.
• TCP/IP layers.
• Packets, layers, protocols.