Synchronization issues in distributed applications: definitions, problems, and quality of synchronization

Abstract

In this report synchronization issues arising in distributed applications are discussed. A general and detailed introduction to the field of synchronization is provided. General terms related to synchronization as well as concepts are introduced, defined and discussed in short. The specific problem fields of synchronization in multi-party environments and in presence of control commands are introduced. A discussion of some of the numerous related work dealing with deifferent aspects of synchronization completes this introduction to synchronization. A system model is introduced that describes a communication system infrastructure being able to guarantee for end-to-end Quality of Service. The system model provides a precise description and definition of the environment and allows for the abstraction from technical details. The synchronization study of this report is based on the system model. Intra- as well as inter-stream synchronization is defined in a formal manner and their establishment and maintenance are described. Special attention is paid on distributed applications with multi-party connections as well as on control commands influencing the course of the presentation. Both issues are critical to synchronization and often not treated adequately in published work. A notion of synchronization quality is developed and defined. The notion comprises the maximum remaining asynchrony, delays, error probabilities and buffer requirements. Based on given environment and synchronization method values for the parameters of the synchronization quality are calculated. This report does not serve as a guideline for a new synchronization scheme, but presents relevant topics in the area of synchronization, provides formal definitions of synchronization and investigates, in an optimal and theoretical environment, the criteria for synchronization quality.