Categories: AP CSP Big Idea 4 May 1, 2026 • Shayan Bhatti, Arnav Pallapotu, Tanay Paranjpe• 1 min read 4.2 - Fault ToleranceA fun interactive lesson about fault tolerance for AP CSP - Big Idea 4 AP CSP · 4.2 FaultTolerance What happens when something breaks? The Big Idea The internet never has a single point of failure Multiple pathsbetween every node One path dies?Data reroutes System keepsworking Class Activity You are the network Everyone stands up. You = a router. You have connections to the people near you. How To Play Pass the message 1Pick two people: Sender & Receiver 2Sender passes a folded note through the "network" (classmates) to Receiver 3Tap someone offline — they sit down & can't pass 4Can the message still get through? Find another path! Go! ▶ Play it 3 rounds Each round, knock out one more router.See when the message can't get through. Debrief What did you notice? Redundancy — extra paths = backup options Failure — the system can absorb it Rerouting — data finds a new way Limit — remove enough nodes and it finally breaks Redundant Routing Many paths, one fails — still works S R Sender Receiver All paths active — 3 routes available Redundant Routing One node dies — data reroutes S R Sender Receiver Middle routers failed — top path still delivers Definitions Key Terms Fault Tolerance The ability of a system to continue operating correctly even when one or more components fail. Redundancy Having duplicate paths or components so that if one fails, another takes over. Router A device that forwards data packets between networks, choosing the best available path. Packet Switching Data is broken into small packets that can each take different routes to reach the destination. ← BACK NEXT →
