Networks are built from physical hardware devices that connect, direct, and transmit data. Understanding each device's role is essential for AQA.
Hardware component installed in every device that connects to a network. Gives the device a unique MAC address. Can be wired (Ethernet port) or wireless (Wi-Fi chip). Modern computers have NICs built into the motherboard.
Connects different networks together (e.g. your home LAN to the internet/WAN). Routes data packets to their destination using IP addresses. Usually assigns IP addresses to devices on the local network (DHCP). Home routers combine router + switch + Wi-Fi access point + modem.
Connects devices within a LAN. Sends data packets only to the intended device using MAC addresses — much more efficient than a hub. Maintains a MAC address table to know which device is on which port. Standard equipment in modern LANs.
Allows wireless devices to connect to a wired network. Extends Wi-Fi coverage in a building. Usually connected to a switch via Ethernet cable. A home router typically has a built-in WAP.
MOdulator-DEModulator — converts digital signals from the computer to analogue signals (for telephone lines) and vice versa. Required for broadband connections over telephone lines (ADSL). Modern home "routers" are usually combined modem + router + switch + WAP units.
Older, simpler device that connects devices in a LAN. Broadcasts ALL incoming data to every connected device, regardless of destination. Inefficient (all devices process all traffic), slow (collisions), and insecure (all devices can see all data). Replaced by switches in modern networks.
| Feature | Hub | Switch |
|---|---|---|
| How data is sent | Broadcasts to ALL devices | Sends only to intended device (by MAC address) |
| Efficiency | Inefficient — wastes bandwidth | Efficient — reduces unnecessary traffic |
| Security | Insecure — all devices see all traffic | More secure — only intended device sees data |
| Collisions | Many collisions (all share same bandwidth) | Rare — each port has dedicated connection |
| Used today? | Rarely — legacy device | Yes — standard in all modern LANs |
Permanent hardware address burned into the NIC. 48 bits (12 hex digits). Unique worldwide. Used within a local network (switches use MAC addresses). Cannot change (in theory — can be spoofed).
Logical address assigned by the network (by a router via DHCP). Can change each time you connect. Used to route data between networks. IPv4 = 32-bit (four groups of 0–255). IPv6 = 128-bit (much larger address space).
Data sent across a network is divided into small chunks called packets. This method of transmission is called packet switching.
Each packet contains:
Packets from the same message may travel by different routes through the internet and arrive out of order. The receiving device reassembles them in the correct order using the packet numbers. This is managed by the TCP protocol.
Advantages of packet switching: if one route is congested or broken, packets can take alternative routes; efficient use of network bandwidth; multiple communications share the same physical lines.
| Type | Description | Speed | Notes |
|---|---|---|---|
| Ethernet (copper) | Twisted-pair copper cable (Cat5/Cat6). Most common LAN cabling. | Up to 10 Gbps | Affected by electrical interference; range limited (~100m) |
| Fibre-optic | Pulses of light through glass/plastic fibre. Used in broadband and WAN backbones. | Hundreds of Gbps | Fastest; immune to electrical interference; expensive; long range |
| Wi-Fi (radio waves) | Radio waves; 2.4 GHz or 5 GHz bands. Standard for wireless LANs. | Up to ~9.6 Gbps (Wi-Fi 6) | Convenient; susceptible to interference; range limited; less secure |
8 questions · 20 marks
| Term | Definition |
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Timed exam conditions.