Our sincere thanks to the following people for their generosity of letting us use their computing resources for conducting our experiments: Ernst Biersack of Eurecom, France; Andreas Festag of TU Berlin, Germany; Aiguo Fei of University of California, Los Angeles; Ralph Keller of ETH Zurich; Manamohan Mysore of University of California, San Diego; Christos Papadopoulos of University of Southern California; Injong Rhee of North Carolina State University; Ellen Zegura and Peter Wan of Georgia Institute of Technology. Without their help, this work would never have been completed.