Emulation is a hybrid experimentation technique intended to bridge the gap between simulation and real-world testing. The key idea of emulation is to reproduce in real time and in a controlled manner the essential functionality of a system, so that it can interact with other real systems that can thus be evaluated. This book describes the technique of network emulation and compares it with the other experimental approaches: the scholarly analytical modeling, the popular network simulation, and the demanding real-world testing. To emphasize the practical aspects related to emulation, this book presents a large number of examples of network emulators on the market, as well as provides an in-depth analysis of a case study, the wireless network emulation testbed called QOMB.