The road of a live report
An analyst opens a live page of sales figures. The numbers live on a computer in another town. The request does not fly. It goes through a cable, a box in the cupboard, a bigger box, a line in the street and many more boxes.
Today you name each box and say what it does.
Key words
| Word | What it means | Example |
|---|---|---|
| Switch | a device that joins devices on one network and sends data only to the right one | |
| Router | a device that joins networks and sends data between them | |
| ISP | internet service provider: the company that gives you internet | a broadband company |
| Backbone | the main high-speed links that carry internet traffic between big networks | |
| Client | a computer that asks for a service | |
| Server | a computer that gives a service | |
| Network | devices joined so they can share things | |
| Packet | a small piece of data sent over a network | |
| IP address | a number that names a device on a network | |
| MAC address | a number built into a network card that names it |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can say what a server, client, switch, router and the internet backbone each do.
Starter
Have a go
Starter
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Servers give, clients ask
A server gives a service: web pages, files, email or logins. It is on all the time. A client is the computer that asks. Your laptop is a client when you open a live report.
One computer can be both. The job decides, not the box.
A switch joins, a router connects
A switch joins the devices in one network. It learns each device's MAC address and sends data only to the port where that device is. This keeps traffic tidy and fast.
A router joins different networks. It reads the IP address on each packet and chooses the next stop. Your home router joins your network to the internet.
Try it: a switch reads a MAC address
ports = ["aa:01", "bb:02", "cc:03"]
def switch(mac):
number = 1
for known in ports:
if known == mac:
return "send out of port " + str(number)
number = number + 1
return "unknown: send to every port"
print(switch("bb:02"))
print(switch("dd:04"))
# Look up "cc:03". Which port is it?Switch compared with router
| Question | Switch | Router |
|---|---|---|
| What does it join? | Devices in the same network | Different networks |
| What address does it use? | MAC address | IP address |
| Where is it? | In the room or the cupboard | At the edge of the network |
| Example job | Sends a file from a PC to the printer | Sends a request out to the internet |
The cells students fill in are left blank in this preview.
Try it: a router picks the next stop
def router(destination):
if destination.startswith("192.168.1."):
return "keep it inside the office network"
return "send it to the ISP"
print(router("192.168.1.20"))
print(router("203.0.113.9"))
# Try "192.168.1.99". What does the router do?