The advent of multimedia technology is creating a number of new problems in the fields of computer and communication systems. Perhaps the most important of these problems in communication, and certainly the most interesting, is that of designing networks to carry multimedia traffic, including digital audio and video, with acceptable quality. The main challenge in integrating the different services needed by the different types of traffic into the same network (an objective that is made worthwhile by its obvious economic advantages) is to satisfy the performance requirements of continuous media applications, as the quality of audio and video streams at the receiver can be guaranteed only if bounds on delay, delay jitters, bandwidth, and reliability are guaranteed by the network. Since such guarantees cannot be provided by traditional packet-switching technology, a number of researchers and research groups during the last several years have tried to meet the challenge by proposing new prools or modifications of old ones, to make packet-switching networks capable of delivering audio and video with good quality while carrying all sorts of other traffic. The focus of this book is on HeiTS (the Heidelberg Transport System), and its contributions to integrated services network design. The HeiTS architecture is based on using the Internet Stream Prool Version 2 (ST-II) at the network layer. The Heidelberg researchers were the first to implement ST-II. The author documents this activity in the book and provides thorough coverage of the improvements made to the prool. The book also includes coverage of HeiTP as used in error handling, error control, congestion control, and the full specification of ST2+, a new version of ST-II. The ideas and techniques implemented by the Heidelberg group and their coverage in this volume apply to many other approaches to multimedia networking.