First of all I want to express my deepest thanks to Prof. Ulrich Schmid for introducing me to the interesting topics in distributed algorithms and for his excellent guidance, counsel and support throughout my master study and especially during the work on this thesis. I also want to thank the research assistants Kyrill Winkler and Manfred Schwarz for their refreshing support during the work on this thesis and for poking on weak points in my arguments during various interesting and enlightening discussions, which opened my eyes to take alternative ways at some points. My family and friends deserve special thanks for backing me and for adding variety to stressful times. Last but not least I want to thank Manuela Hofer for her inexhaustive love and the patience in stressful times and sleepless nights full of work.