Systems / Protocol adaptation
Message-sorting station
Assemble fragments, keep messages in order, and deliver once—even after a restart.
Assemble two messages and deliver A +4, then B +3 exactly once. Then restart, replay a saved receipt, and reject an altered message A that asks for +9.
Each message needs both fragments. B depends on A. Receiver checkpoints save fragments; destination receipts survive independently.
Fragment dock
Durable destination
DESTINATION COUNTER00target 07
ANo receipt
BNo receipt
Restarts0
Safe replays0
Conflict rejectedPending
Explore the controls, then check your result.
Need a hint?
Buffer all four fragments and save a receiver checkpoint. Deliver A and B, restart, then return A’s saved receipt. The receipt prevents a second +4. Reject the changed payload under the same ID.