The specific focus of this book is on mechanisms that affect the VoIP user satisfaction while not explicitly involved in the media session (i.e. the coded speech). This relates to the extra delays introduced by the security and the signaling protocols used to set up an authorized VoIP session and to the disruption caused by the user mobility that may take place during the session. This book thus investigates and proposes techniques for realizing time-efficient control mechanisms for VoIP. One important aspect within this book is the use of correlated error processes or random error processes or both to model the FER in the channel in order to evaluate the delays incurred by control mechanisms in different error situations.