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Network components and transmission media

Edexcel IAL Computer Science · WCP01 Principles of Computer Science

A network needs hardware to connect devices, move data between them and protect them. Spec point 3.1.1 lists the components and media you need.

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Hardware

Network interface card (NIC): hardware in each device that connects it to a network (wired or wireless). It has a unique MAC address and converts data into signals for the medium.
Switch: connects devices on a local area network (LAN). It learns the MAC address of each device on each port and sends frames only to the intended device, reducing unnecessary traffic.
Router: forwards packets between different networks using IP addresses. A home router usually combines a router, a switch, a wireless access point, a firewall and often a modem in one box, and gives devices local IP addresses (DHCP).
Modem (modulator-demodulator): converts digital data from the computer into signals suitable for the line to the internet service provider (for example telephone or cable) and back again.
Wireless access point (WAP): lets wireless devices join a wired network using radio waves (Wi-Fi).

Firewalls

A firewall monitors incoming and outgoing traffic and blocks or allows it according to rules (for example by IP address, port or protocol).

Hardware firewall: a separate device (or part of the router) protecting every device on the network behind it.
Software firewall: runs on an individual computer, protects only that device and can be set per application.

A firewall cannot stop threats that users let in themselves, such as malware in an email attachment.

Transmission media

Medium	How	Benefits	Drawbacks
Copper (twisted pair, coaxial)	Electrical signals	Cheap, easy to install, reliable	Limited distance (about 100 m for Ethernet), affected by electrical interference
Fibre optic	Pulses of light in glass	Very high bandwidth, long distances, no electrical interference, hard to tap	Expensive, harder to install and join
Wireless (radio waves)	Radio signals, e.g. Wi-Fi	No cables, mobility, easy to add devices	Limited range, walls reduce signal, interference, slower, easier to intercept

Worked example

A small office has 12 wired computers, some laptops and an internet connection. Name the components needed and their purpose.

A NIC in every device.
A switch to connect the wired computers on the LAN.
A WAP so the laptops can connect wirelessly.
A router to forward traffic between the LAN and the internet, with a modem for the line to the ISP.
A firewall to filter traffic between the internet and the LAN.

Answer: NICs, switch, WAP, router plus modem, firewall (often combined in one home or small office router).

Key idea: NIC connects a device (MAC address); switch connects devices on a LAN using MAC addresses; router links networks using IP addresses; modem converts signals; WAP gives wireless access; firewall filters traffic.

Check yourself

Which device sends data only to the intended device on a LAN, using MAC addresses?
- Modem
- Switch
- Wireless access point
- Router
Show answer
Switch. A switch learns which MAC address is on each port.
What is the main job of a router?
- To convert light into electrical signals
- To store web pages
- To give each device a MAC address
- To forward packets between networks using IP addresses
Show answer
To forward packets between networks using IP addresses. Routers join networks, such as a home LAN and the internet.
What does a modem do?
- Blocks unauthorised traffic
- Converts digital data into signals that can travel on the line to the ISP, and back
- Connects wireless devices to a wired network
- Learns MAC addresses
Show answer
Converts digital data into signals that can travel on the line to the ISP, and back. Modulator-demodulator.
Which is a benefit of fibre optic cable over copper?
- It is cheaper to install
- It can be bent sharply without damage
- It is not affected by electrical interference and works over longer distances
- It needs no special equipment to join
Show answer
It is not affected by electrical interference and works over longer distances. Light signals are immune to electrical interference and lose little strength.
Explain one difference between a hardware firewall and a software firewall.
Show answer
A hardware firewall is a separate device that protects every device on the network behind it, whereas a software firewall runs on one computer and protects only that computer.. Compare what each protects.
Which component contains the MAC address of a device?
- Switch
- Firewall
- Network interface card
- Modem
Show answer
Network interface card. The MAC address is given to the NIC when it is made.
Which is a drawback of wireless transmission compared with cable?
- Signals can be intercepted more easily and walls reduce range
- Devices must be fixed to a desk
- It needs cables to every room
- It cannot carry data
Show answer
Signals can be intercepted more easily and walls reduce range. Radio signals spread out, can be picked up by others and are weakened by obstacles.

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Sources

Pearson Edexcel International Advanced Subsidiary/Advanced Level in Computer Science specification (2026)

Last updated 8 November 2026. Spotted a mistake? Tell us.