How the internet works

Prepare

• • 4 learners: print 1 learner/card pack and 1 facilitator pack; 12: 2 learner/card packs and 1 facilitator pack; 30: 5 learner/card packs and 1 facilitator pack
• • Cut one role-and-packet set per team; the facilitator cuts one failure and one congestion card
• • Mark two visibly distinct routes with string, tape or desk spacing; keep the event cards hidden

Materials

• • Learner map and pens
• • Sender, Router A, Router B, alternate-router and server cards
• • Three addressed packet cards
• • Two route strips or lengths of string
• • Route-failure card; projector and internet optional

Facilitate

• • Do not define all terms before the first model and prediction
• • Sender checks payload split and address; Router A and the route routers announce only the forwarding information they use; Destination records received/missing parts; Observer records route and what stayed unchanged
• • Packet 1 uses Route 1; fail that path before Packet 2 uses the distinct alternate
• • Mark the alternate congested before Packet 3: it still travels with recorded delay, showing busy is not broken
• • Then remove every alternate while leaving destination and address visible
• • Let learners revise openly; end with structured teach-back, not a vocabulary quiz

Discussion

• • What information must remain on every packet?
• • What can a router decide without understanding the message?
• • When the path failed, what changed and what stayed the same?
• • What would make rerouting impossible even though the destination still exists?

Suggested introduction

Give the sender a three-part message and ask the group how it could reach a server that has no direct wire to the sender. Collect an initial model before naming packet or router.

Likely misconception

A router does not need to open and understand the whole message, and a failed link does not erase the destination. An alternate route helps only when it exists and has usable capacity.

Expected response

Learners should model sender, addressed packets, next-hop forwarding, destination reassembly and the conditional use of an alternate route, then explain the same relationships in a new case.

Adaptation

A solo learner traces packet cards across the printed map. A learner who cannot move can be route controller, packet recorder or debrief explainer. Never make physical movement the only way to participate.

Extension

Add a capacity limit to one path, delay one packet, or remove every alternate path. Learners must say which parts of the model still hold and which outcome changes.

Shorten it

25-minute route: 0-4 initial model; 4-8 packet/route setup; 8-13 first packet; 13-18 failed-path prediction and alternate route; 18-22 revised model; 22-25 teach-back. Omit the second transfer case and extension.

Debrief

• • Ask one team to explain the journey without the role names visible
• • Ask another team to challenge one oversimplification
• • Finish the sentence: the path changed, but ...
• • Name the condition that makes an alternate route useful

Group adaptations

Pairs

One learner moves packets; the other checks destination, sequence and next hop. Swap after the route failure.

Small groups

Use teams of 4-6: sender, one or two routers, destination, packet mover and observer. Combine packet mover with sender in a team of four.

Whole class

With about 30 learners, make five teams of six and run in parallel. Each team reports only its changed prediction and one model boundary, preventing long waits.