Week 6 - Consensus

Question 1

What is the difference between stop failure and byzantine failure?

Answer 1

With byzantine only non-fault processes have to agree on different values

Question 2

Describe the coordinated attack problem

Answer 2

A group of general needs to agree on when to attack, the attack only succeeds if they all commit. The generals will be ready to attack at different times. The generals can sends messengers to each other who may get captured or lost.

Question 3

Describe the FloodSet consensus alorgithm

Answer 3

Each process in a complete graph maintains a variable W. It initially only contains the process’ initial value. For each round, each process broadcasts W and adds all elements it has not seen before to its W. At the end if W has one element the process decides on that element, otherwise it picks a value from W.