hw1-sol-sp11 - ECE428/CS425/CSE424: Distributed Systems...

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1. The 5 node topology shown below uses a modified heartbeating protocol for detecting failures, as follows: - All processors maintain a sequence number. - p i sends p (i+1)mod 5 and p (i-1)mod 5 a heartbeating message every T time units (0 <= i <= 4). - If p i has not received a new heartbeat from any of the two neighboring processors for the past 3*T time units, since it received the last heartbeat, then p i detects the corresponding processor as failed and communicates the information to all the other processors. a. Enumerate all possible combinations of simultaneous processor failures (including single processor failures) that can be reliably detected by this protocol. Assume a synchronous system. Single processor failures: p 0 , p 1 , p 2 . p 3 , p 4 2 simultaneous processor failures: p 0 p 1 , p 0 p 2 , p 0 p 3 , p 0 p 4 , p 1 p 2 , p 1 p 3 , p 1 p 4 , p 2 p 3 , p 2 p 4 , p 3 p 4 3 simultaneous processor failures: p 0 p 1 p 3 , p 0 p 2 p 3 , p 0 p 2 p 4 , p 1 p 2 p 4 , p 1 p 3 p 4 b. Explain why this protocol cannot reliably detect all possible 3 simultaneous processor failures. How will you modify the protocol to detect up to 3 simultaneous processor failures reliably? (Use a figure similar to the one shown above.)
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This note was uploaded on 02/08/2012 for the course ECE 428 taught by Professor Hu during the Spring '08 term at University of Illinois, Urbana Champaign.

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hw1-sol-sp11 - ECE428/CS425/CSE424: Distributed Systems...

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