title: PBFT: Why cant the replicas perform the request after 2/3 have prepared? why do we need commit phase?
body: <p>I know there are some questions on this website that asks the same questions. However the answer is never clear:</p>
  
  <p>In PBFT, why cant the replicas execute the requests after 2/3s have prepared? why is commit phase needed? if 2/3 + 1 replica have agreed to prepared, then I owuld think they can execute the request without broadcasting again?</p>