Which Device, Where?
Nine devices, each with one job. Here they are side by side, the two pairs that exam papers love to set against each other, and the rules for placing them in a campus case study.
1All nine at a glance
| Device | What it does | Remember it by |
|---|---|---|
| Ethernet card (NIC) | Connects a computer to a wired network; has a MAC address | the socket inside the computer |
| RJ45 | 8-pin connector on the ends of an Ethernet cable | the clear plug that clicks |
| Wi-Fi card | Connects a computer to a wireless network by radio waves | a network card with an antenna |
| Repeater | Regenerates a weak signal so it can travel further | cable longer than about 100 m |
| Hub | Connects computers in a LAN; copies data to every port | broadcast — not intelligent |
| Switch | Connects computers in a LAN; sends data only to the right port | unicast — MAC address table |
| Router | Connects different networks with the same protocol; sends data along the best route | picks the next hop |
| Gateway | Entry and exit point of a network; joins networks with different protocols | the gate, often with a firewall |
| Modem | Converts digital signals to analog and back | MOdulator–DEModulator |
2The two pairs that get mixed up
Same: both connect the computers of one LAN.
Different: a hub sends data to every computer; a switch sends it only to the computer it is for, using MAC addresses.
Same: both pass data from one network to another.
Different: a router joins networks that use the same protocols and picks routes; a gateway joins networks that use different protocols and converts between them.
Switch between hub and switch, and send the same messages to both.
3Placing devices in a case study
The long networking question on the paper describes a campus with several blocks and asks where devices should go. Four rules answer almost all of it.
A switch (or hub) in every block, to connect all the computers in that block.
A repeater on any cable between two blocks more than about 100 m apart.
A router (working as the gateway) where the campus connects to the Internet or to a head office in another city.
A modem where a telephone or cable line brings the internet connection in.
4Name the device
Read what the device does and pick it.
5Check yourself
Which of these is a connector rather than a device that handles data?
A company's campus has four blocks; the Admin and Store blocks are 150 m apart. Where should a repeater go?
Which device is needed in every computer that joins a wireless network?