Computer systems and networks · GCSE Computer Science
Network hardware
GCSE Computer Science network hardware: router, switch, hub, wireless access point, NIC, modem — roles in LAN, WAN and the internet.
Switch connects LAN devices intelligently by MAC. Router joins networks and routes by IP. WAP adds Wi-Fi. Modem modulates for the ISP line.
The important bits
What you need to know
- 1
NIC (network interface card) connects a device to a network — wired Ethernet or wireless, has a MAC address.
- 2
A switch connects devices on a LAN, forwarding frames to the correct MAC address — more efficient than a hub.
- 3
A hub broadcasts all traffic to every port — obsolete but may appear in compare questions; collisions on busy LANs.
- 4
A router forwards packets between networks using IP addresses — home router joins LAN to ISP/internet.
- 5
Wireless access point (WAP) provides Wi-Fi; often built into home router unit (router + switch + WAP combo).
- 6
Modem modulates/demodulates signals on the phone line, cable or fibre to ISP — digital data on analogue/carrier media.
- 7
Firewall may be hardware or software on router — filters traffic by rules. GCSE: block incoming unauthorised.
- 8
Cables: Ethernet twisted pair to switch; fibre for high speed backbone; fibre to premises increasingly common.
Quotations worth analysing
Short evidence. Real method.
“Switch uses MAC addresses on a LAN”
Learns which device is on which port. Hub does not — floods all ports. Exam compare: switch efficient, hub wasteful.
“Router routes between networks using IP”
Default gateway on LAN points to router interface. Confusing router with switch is the classic diagram error.
“Modem connects to ISP infrastructure”
Often separate or combined in “router” box. DSL/cable modem different media — GCSE names the role not every standard.
Go deeper
Home network layout
Devices (phones, PCs) → Wi-Fi to WAP or Ethernet to switch ports on router → router NAT to modem → ISP → internet. Router assigns private IPs DHCP. Public IP on WAN side. Switch in router forwards LAN traffic locally without sending to ISP. Printer on LAN accessed via switch/Wi-Fi. Guest Wi-Fi VLAN — extension. Label diagram: NIC in each device, one router boundary between LAN and WAN.
Go deeper
Switch versus hub
Hub: packet arrives port 1, copied to all ports — half-duplex collisions. Switch: reads dest MAC in frame, forwards only to port where that MAC was seen — dedicated paths, full duplex common. Table of MAC to port built from source addresses in frames. GCSE 4-mark: describe how switch reduces unnecessary traffic compared to hub. Enterprise: managed switch VLANs segment traffic.
Go deeper
Router role in packets
PC 192.168.1.5 sends to 8.8.8.8 — dest not on LAN, packet to default gateway router. Router decrements TTL, forwards to ISP next hop per routing table. Router may run DHCP, DNS relay, firewall. Enterprise multiple routers. GCSE: router connects LAN to WAN, translates between network boundaries, uses IP not MAC for routing decision across networks. MAC still used inside each hop LAN segment.
See the idea in action
School LAN: 30 PCs with NICs, cable to switch, switch to router, router to modem, modem to ISP fibre. PC sends to another PC same LAN: switch delivers by MAC, router not involved. PC sends to website: packet to router default gateway, router forwards to ISP. Laptop on Wi-Fi: WAP in router, then same path. Hub replacement: if hub used, every frame hits all PCs — congestion.
Exam technique
Turn knowledge into marks
Draw LAN on one side of router, internet on other. Switch inside LAN. Label MAC for switch, IP for router across networks.
Common mistakes
Do not give these marks away
- 01
Calling a switch a router — different layer and address type on GCSE papers.
- 02
Saying hub sends only to intended recipient — that is a switch.
- 03
Forgetting NIC is required in every networked device.
Which device forwards data to the correct device on a LAN using MAC addresses?
ARouter
BSwitch
CModem
DFirewall only
Show the answer
Switch. Switch learns MAC-port mapping on LAN. Router uses IP between networks. Modem handles ISP line modulation.
Quick questions
If this is the bit you searched
What is the difference between a switch and a router?
Switch connects devices on one LAN using MAC addresses. Router connects different networks and routes by IP address.
What does a modem do?
Modulates and demodulates signals between digital devices and the ISP line (cable, DSL, fibre interface).
What is a NIC?
Network Interface Card — hardware in a device to connect to wired or wireless network, with a MAC address.
Why is a hub rarely used today?
It broadcasts all traffic to every port causing collisions and wasted bandwidth; switches forward selectively.