Network Components and Social Media
Senior 2 · ICT
Network Components and Social Media
Lesson 3 of 4
22 min
In most schools, the cables from every computer disappear into a cabinet of boxes with blinking lights, and a small box with antennas is fixed high on a wall. These are network devices. They do not create data; they move it to the right place. When someone says "the internet is down", knowing what each box does lets you find the fault instead of guessing.
A hub connects several devices in a local area network (LAN). Whatever arrives on one port, it copies out of every other port.
Worked example
Eight computers, PC1 to PC8, are plugged into an 8-port hub. PC1 sends a file to PC5. The hub copies the file out of all 7 other ports. PC5 keeps it; the other 6 computers receive it and throw it away. This wastes capacity, and when two computers send at the same moment their signals collide and must be sent again. Hubs are now largely obsolete.
A switch also connects devices in a LAN, but it learns which device is on which port by reading each device's MAC address. It then forwards data only to the port of the destination.
The same example with a switch. PC1 sends a file to PC5. The switch looks up PC5's MAC address in its table, finds port 5, and sends the file out of port 5 only. Meanwhile PC2 and PC3 can exchange data at the same moment without a collision. Switches are faster and more private than hubs, so modern LANs use switches.
A wireless access point (AP) lets Wi-Fi devices join a wired network. A cable connects it to a switch or router, and it turns that wired connection into a Wi-Fi signal. One AP serves only a limited number of devices well; a common guide is roughly 10 to 25 at a time.
Worked example
A school hall will hold 60 students with tablets, and one AP serves 25 devices well. 60 ÷ 25 = 2.4. You cannot install 0.4 of an access point, so round up: the hall needs at least 3 access points.
A router connects two or more different networks and forwards data between them. Data travels in small pieces called packets, each labelled with the address of its destination. A router reads that address and sends each packet on towards its destination. The router at your school joins the school LAN to the network of its internet service provider (ISP); after passing through many more routers, the packets reach the website's server.
The "Wi-Fi router" in many homes is really several devices in one box: a router, a small switch (its LAN ports) and a wireless access point.
| Device | What it connects | How it handles data |
|---|---|---|
| Hub | Devices in one LAN | Copies data out of every port |
| Switch | Devices in one LAN | Sends data only to the destination's port, using MAC addresses |
| Access point | Wireless devices to a wired LAN | Converts between Wi-Fi and the cable |
| Router | Different networks, such as a LAN and the internet | Forwards packets towards their destination network |
A lab needs 20 wired desktops, 1 wired printer, Wi-Fi for teachers' laptops, and a connection to the ISP's fibre line. The plan looks like this:
Count the switch ports needed: 20 desktops + 1 printer + 1 cable to the access point + 1 cable to the router = 23 ports, so a 24-port switch is enough. The router is the only device that touches the outside network.
Tip
Memory hook, a post office: a hub reads every letter aloud to the whole room; a switch puts each letter in the right pigeon-hole; an access point is the counter window for visitors who have no pigeon-hole (wireless users); a router sends letters between towns. In exams, "different networks" or "the internet" points to a router, and "within one LAN" points to a hub or a switch.
Sixteen computers are connected to a 16-port hub. PC3 sends a file to PC9. How many computers receive a copy they do not need?
Solution: The hub copies the file out of the 15 other ports. PC9 needs it, so 15 − 1 = 14 computers receive an unneeded copy.
Answer question 1 again for a 16-port switch.
Solution: 0. The switch sends the file only out of PC9's port.
A conference room will hold 90 laptops, and one access point serves 25 devices well. How many access points are needed?
Solution: 90 ÷ 25 = 3.6. Round up, so 4 access points. Three would serve only 75 devices.
Ishimwe's laptop joins the school Wi-Fi and can open files on the school's own server, but it cannot open any website. Which device is most likely at fault?
Solution: The router (or its link to the ISP). The access point and the switch must be working, because the laptop reaches the server inside the LAN. What fails is the connection to a different network, the internet, which is the router's job.
Name the three devices usually combined inside a home "Wi-Fi router".
Solution: A router, a switch (the LAN ports) and a wireless access point.
Summary
Sources and credits
The worked examples, network plan and practice items were written by Ganzaa.
This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.
Internet (ISP fibre line)
|
[ Router ]
|
[ Switch, 24 ports ]
| | |
20 PCs Printer [ Access point ]
))) Wi-Fi
teachers' laptops