hw3-sol-sp11 - ECE428/CS425/CSE424: Distributed Systems...

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ECE428/CS425/CSE424: Distributed Systems Spring 2011 Homework 3 Due: by 2 pm on 03/15/2011 Total points: 70 1. (20 points) Suggest a message-passing mutual exclusion algorithm in which nodes enter critical section in the happened-before order. That is, if a node A’s entry operation happens-before that of node B, then node A must enter critical section first. Explain why you believe that your algorithm is correct. Assume that the system is asynchronous, but there are no failures. Also assume that all channels are reliable and FIFO. If you believe that such an algorithm does not exist, explain why. We can use the Ricart & Agrawala’s algorithm described in the textbook. The happened-before order is ensured by the Lamport’s logical timestamp. This is because when event a happens-before event b , the logical timestamp( a ) < timestamp( b ). Therefore, if a node A’s entry operation happens-before node B, the timestamp(A) < timestamp(B), implying that A will get access to the critical section before B. 2. (15 points) Consider slide 4 in the set of slides used for Chord (distributed hash tables) in lecture 11. a.
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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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hw3-sol-sp11 - ECE428/CS425/CSE424: Distributed Systems...

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