22C: 166 Distributed Systems and Algorithms
Homework 4
Total points = 60
Assigned 10/31/08, due 11/07/08
Please submit typewritten solutions. You can email it to the TA
([email protected]), or submit a paper copy to me
Question 1. (10+5 = 15 points) Consider a modification of the sliding window
protocol where the receiving process has a buffer of size B (B>1) to hold the
pending messages before delivering it to the application.
(a) Rewrite the program for the receiving process to reflect the change.
(b) What will be effect of increasing B? Explain.
Question 2 (10 points) Explain how software errors can lead to (1) crash failure
(2) omission failure in a process. Provide examples to explain the complete
scenario in each case.
Question 3. (10 points) The byzantine generals algorithm helps reach a
consensus when less than one-third of the processes undergo byzantine failure.
However, it does not suggest how to diagnose such failures. Assuming that at
most one process can be faulty, examine if the faulty process can be identified
without any ambiguity. Investigate all relevant cases.
Question 4 (5 points) Chapter 13, exercise 3
Question 5. (10 points) In a spanning tree of a graph, there is exactly one path
between any pair of nodes. If a spanning tree is used for broadcasting a
message, and a process crashes, some nodes will not be able to receive the
broadcast. Our goal is to improve the connectivity of the subgraph used for
broadcast, so that it can tolerate the crash of one process.
