The authors wish to thank the members of the Munich Network Management (MNM) Team for helpful discussions and valuable comments on previous versions of the paper. The MNM Team is a group of researchers at the Leibniz Computing Center Munich and the Munich Universities. It is directed by Prof. Dr. Heinz-Gerd Hegering. We gratefully acknowledge in particular Victor Apostolescu, Thomas Kaiser, Ulrich Katzenschwanz and Bernhard Neumair who provided valuable suggestions and advice.