Think it through together · A little story
A girl sends two sets of information. The robot reminds her that network routes can change, so packets are not guaranteed to always pass through the same set of forwarding stops.
Lay out the process
- NormallyUse an available path
- A link changesForwarding information is updated
- Later packetsMay take another path
Internet routes can change because of failures, policies, or topology changes, so packets are not guaranteed to always take the same path.
Many networks try to keep packets in the same communication flow on a stable path when possible. That does not mean “every packet picks a random route.”
Different paths may also cause later packets to arrive first. Higher-level protocols need to handle this according to their own rules.
Your turn to try
If two packets arrive in the opposite order, does that prove the sending program got the order wrong?
Have you thought it through? Open for an explanation
No. Routes and queuing can affect arrival order. You need to consider the transport protocol to understand the order the application finally receives.
Take away one discovery
Internet routes can change because of failures, policies, or topology changes, so packets are not guaranteed to always take the same path.
Try covering the diagram above and explaining each step to someone in your family. If one step is hard to explain, go back and look at that card again.