Network Packets – from Computer A to Computer B through Routers
Computer ScienceNetworks & the InternetAges 11–12
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Networks & the Internet
The message is split into numbered packets, and each one finds its own way through the routers to the receiving computer; packets can take different paths, get lost, and be resent. Students click a router to break it and watch packets reroute, change the packet loss rate, and watch computer B reassemble the complete message.
Lesson: The Internet: how information travels (packets, routers, reliability)
What it shows
Data on the Internet is not sent as one continuous stream. A message is split into small packets, each carrying a sequence number and the destination address. Routers forward each packet independently along any working route, so packets of the same message can take different paths and arrive out of order. Some packets are lost on the way and the sender retransmits them; the receiver uses the sequence numbers to reassemble the message. This packet switching makes the network robust: when a router fails, traffic can be sent around it.
How to use
Choose a Message and a Number of packets, then watch the numbered packets travel from Computer A to Computer B. Raise the Packet loss rate per hop and compare how many packets are resent and how long delivery takes. Click a router to break it and see packets switch to the other path; break a router on both paths to show what happens when no route is left. Use Pause to discuss the reassembly order.
Parameters you can change
- Number of routers per path 1–5
- Packet loss rate per hop 0–50 %
- Number of packets 2–8 packets
- Message HELLO EVERYONE, COMPUTING 6, INTERNET
- Speed 1–5
Questions to explore
- Why does Computer B need the sequence number on every packet?
- What happens to the packets when a router on one path breaks down?
- How does a higher packet loss rate affect the number of transmissions and the total delivery time?
