A girl and a robot thinking together

Let’s think it through · Start with a story

After reaching the library building, the robot still needs to find the right service desk. Network data also has to get from “the device” to the right “endpoint.”

Break down the process

Follow the numbered steps, then explain them in your own words
  1. Destination IPWhich host interface to reach
  2. Protocol and portWhich endpoint to find
  3. Operating systemMatch a connection or service
  4. ApplicationHandle the content

IP addresses and ports help deliver data at different layers.

IP handles network addressing, while TCP or UDP ports help distinguish communication endpoints. A connection also involves a source address and source port, so one destination port alone does not describe the whole communication.

This lets many clients communicate with the same website at the same time.

Your turn

If many people visit the same website over HTTPS, must they receive one another’s replies by mistake?

Have an answer? Click to see the explanation

No. The protocol and system use connection information to distinguish communications; they do not rely only on the fact that the server port is the same.

Takeaway

IP addresses and ports help deliver data at different layers.

Try covering the diagram and explaining each step to someone at home. If a step is hard to explain, go back and look at that card again.