Virtual Labs

Distributed Consensus - Crash Failures Scenario

Which process must crash in order for consensus to take at least 2 rounds?

a: The process with the highest value/ID Explanation

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b: The process with the lowest value/ID Explanation

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c: A process chosen at random Explanation

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d: All processes except one Explanation

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What happens when no processes crash during the consensus algorithm?

a: Consensus is achieved in exactly f+1 rounds Explanation

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b: Consensus is achieved in 1 round Explanation

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c: Consensus cannot be achieved Explanation

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d: The algorithm runs indefinitely Explanation

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In the fail-stop model, what characterizes a crashed process?

a: It sends incorrect messages to other processes Explanation

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b: It stops executing and never restarts Explanation

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c: It continues running but ignores messages Explanation

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d: It randomly delays its messages Explanation

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When must the lowest value/ID process crash for consensus to take at least 2 rounds?

a: After it has broadcast its value in round 1 Explanation

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b: Before it broadcasts its value to all processes in round 1 Explanation

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c: At any point during the simulation Explanation

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d: Only after all processes reach consensus Explanation

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What determines the final consensus value in the algorithm?

a: The value of the process with the highest ID Explanation

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b: The average of all initial values Explanation

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c: The minimum value among all non-faulty processes Explanation

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d: The value of the last process to broadcast Explanation

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Why does the algorithm guarantee that consensus will be reached in exactly f+1 rounds in the worst case?

a: Because f processes will definitely crash Explanation

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b: Because there must be at least one round where all remaining processes broadcast Explanation

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c: Because the minimum value is always found in the last round Explanation

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d: Because Byzantine processes are eliminated after f rounds Explanation

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Which processes must crash in order for consensus to take at least 3 rounds?

a: Only the process with the highest value Explanation

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b: The process with the lowest value first, and processes with lowest value in next round Explanation

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c: All processes except two Explanation

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d: A random subset of processes Explanation

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What is the theoretical maximum number of rounds needed for consensus with n processes and f failures?

a: f rounds Explanation

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b: f+1 rounds Explanation

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c: n rounds Explanation

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d: n-f rounds Explanation

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When should processes crash in the second round, in order for consensus to take 3 rounds?

a: Processes with the lowest value, before they manage to send to all processes without the lowest value Explanation

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b: Any process can crash at any time to ensure consensus takes 3 rounds Explanation

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c: Processes with the highest value/ID, before they send to all processes Explanation

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d: One of the processes with the lowest value, before it sends to all processes without the lowest value Explanation

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