The evolution of computers and networks leaves no doubt about the important role of interactive multimedia services. The quality of these new services will be a key issue for their wide deployment, and this quality is determined by the opinion of the users. The best Quality of Service (QoS) is not the highest, but the most suitable to the different users' needs. In order to provide a suitable level of QoS, an application needs to know which relevant network parameters have impact on the quality as it is perceived by the users. This paper presents a top-down approach to study the influence of network performance parameters on the user perceived quality, taking conversational speech as an example of a simple, essential and demanding application. Three types of network are considered: IP, ATM and IP over ATM. For each of these cases, the influence of the corresponding network performance parameters is studied. 1

With the prospect of commercializing wireless ATM networks fast becoming a reality, and ATM becoming one of the main network technologies for multimedia computing, the design of ATM connection management solutions has to take into consideration these recent developments. Unfortunately, current ATM signaling solutions standardized by the ATM Forum have to be modified extensively in order to support wireless ATM. Furthermore, these solutions have not delivered a suitable multicast service which can support the communication requirements found in today's computer-based multimedia applications. The work described here therefore addresses these shortcomings by proposing a new multicast connection service architecture and its related algorithms. Some of the important concepts elaborated in the design include the notion of open signaling, the use of logical multicast groups to handle all connections, and seamless support for host mobility. IEEE Communications Magazine . November 1997 53...