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alphaPlan · Systems facilitator pack

A packet's journey through a changing network

Reference lesson: How Computers & the Internet Work > The internet > How the internet works

Outcomes

  • • Build relationships before memorising terms
  • • Predict packet behavior after a path failure
  • • Revise the model and transfer it to a new case
  • • Teach back the system and one simplification

Exact print plan

  • • 4 learners: 1 learner pack/card set + 1 facilitator pack
  • • 12 learners: 2 learner packs/card sets + 1 facilitator pack
  • • 30 learners: 5 learner packs/card sets + 1 facilitator pack
  • • Pens, scissors and two route markers per team; black-and-white is sufficient

45-minute sequence

  1. 0·6. Draw an initial model before defining packet or router.
  2. 6·12. Assign cognitive roles, inspect payload versus address, and build two distinct routes.
  3. 12·18. Packet 1 uses Route 1. Sender checks split/address; routers announce only forwarding information; destination records the received part.
  4. 18·26. Fail Router A→B. Predict, then send Packet 2 through the distinct Alternate Router.
  5. 26·32. Mark Route 2 congested. Packet 3 still travels, but the observer records delay: busy is not broken.
  6. 32·37. Remove every alternate. Keep destination/address cards visible and reason why delivery cannot continue now.
  7. 37·42. Reconstruct the model; distinguish congestion, routing and possible TCP retransmission in the Korçë case.
  8. 42·45. Structured teach-back and one model boundary.

Grouping

  • • 4 learners: sender also moves packets; Router A; alternate/router B; destination-observer
  • • 12 learners: two teams of six
  • • 30 learners: five teams of six in parallel; each reports only its changed prediction and one boundary
  • • Pairs: mover and route checker; swap after failure

Listen for

  • • Packets retain a destination
  • • Routers choose an available next hop without understanding the whole message
  • • Destination reassembles received data
  • • A failed path is not a vanished destination
  • • Alternate routing is conditional, not guaranteed

Misconceptions and interventions

  • • Router reads the whole message: ask which information is actually needed to choose a next hop.
  • • Every packet always takes a different route: stress that it can, not that it must.
  • • A broken cable erases the IP: remove the route strip but leave the destination card and address visible.
  • • Rerouting is guaranteed: remove the alternate route and ask what the model now predicts.

No-internet, no-projector and inclusion

The complete activity runs from these sheets, role cards, route markers and pens. A learner who cannot move can control routes, record packet order or lead the explanation. Read every diagram as a sequence in words; never depend on colour.

Cut-out cards

Cut on dashed borders. This is a simplified learning card, not a real packet header. Text and symbols, not colour, carry meaning.

✕ ROUTE 1 UNAVAILABLE
! ROUTE 2 CONGESTED · DELAY, NOT FAILURE

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