Open Access

In 1993 the interconnection of three local ATM-based networks in Berlin was initiated by DeTeBerkom, the Gesellschaft fur Mathematik und Datenverarbeitung (GMD) and the Technical University of Berlin (TUB). This paper describes the goals of this Berlin ATM LAN Interconnection (BALI) and presents first results. It introduces the infrastructure of the BALI network in its current and its accomplished state, and summarizes the technical goals of BALI. These goals include work that will be performed within the German Research Network (DFN) ATM-trial. It also describes the test-configurations for the performance evaluations of the ATM-network, and presents the first results of the evaluations. A summary is included of the work that will be performed in the near future.

From the authors' point of view on the current state of R & D on distributed multimedia in Germany there is a significant effort of some key players preparing mltimedia solutions for different applications and markets. Many of them take use of the current workstation/PC technologies. They include new hardware building blocks and new standards in the area of services, coding, compression and networking. Limitations arise from the current computer architectures and the different layers involved.ATM is considered as a key technology for the future WANs as well as for the LANs. For the development of the European market, technologies and applications the authors hope that the Fourth Framework of scientific research and development (1994-1998) of the European Union and its ACTS program will significantly contribute to the nervous system of the economy, and more generally, to tomorrow's society.

Three emerging technologies are combined in a setup that has been installed and tested at GMD - the German National Research Center for Information Technology: 1. Multimedia Telecooperation Applications; 2. ATM-based high-speed networks; 3. Satellite links. The results are promising: After some initial problems, the complete scenario is up and running, allowing the interconnection of local high-speed infrastructures in rural areas to a core network via satellite. This paper describes the R&D background and state- of-the-art that led us to this approach. It then describes the communication infrastructure and the application infra- structure of the setup, the problems we had and the solu- tions we found. Finally, our experiences are summarized, and an outlook is made for future implementations.

This paper discusses the future trends on teleteaching applications. These include remote access to distributed virtual reality resources, information on demand teleservices and multimedia telecommunication environments across high speed multicast networks for teleteaching scenarios. A teleteaching session held by a lecturer in Berlin is multicasted across the regional metropolitan area network. The lecturer has on-line access to some virtual studio and a CM5 supercomputer in Bonn. He can interactively create virtual environments in real-time and the results are multicasted during the lecture. The students may interact with the lecturer via some Multimedia Collaboration Teleservice. They have access to Information on Demand Teleservice (IoD) which provides them with additional background material. The session is broadcasted via satellite link giving more than hundred million people the opportunity to listen and to view lectures.

This paper describes a solution for an interactive video service in the World Wide Web. It looks at creating an information retrieval system based on television and German video text. The service aims at presentation in the World Wide Web. The paper handles all components of this service beginning with content collection and ending with the presentation at the enduser. It starts with a look at the service as it appears to the client. It next deals with obtaining traditional media and processing them into a format for later usage in a teleservice. Then follow reflections on possible client concepts, especially methods to integrate real time video into Webpages. Video transmission also provides the main issues for the server and communication between client and server. After an explanation of our implementation the paper ends with some conclusions about experiences and future work.

The term "virtual studio" refers to real-time 3D graphics systems used to render a virtual set in sync with live camera motion. As the camera pans and zooms, the virtual set is redrawn from the correct perspective. Using blue room techniques, actors in front of the real camera are then “placed in” the virtual set. Current virtual studio systems are centralized – the blue room, cameras, renderers etc. are located at a single site. However distributed configurations offer significant economies such as the sharing of expensive rendering equipment among many sites. This paper describes early expe- riences of the DVP1 project in the realization of a distributed virtual studio. In particular we de- scribe the first video production using a distributed virtual studio over ATM and make observations concerning network QOS requirements.

The Internet Engineering Task Force (IETF) is currently working on the development of Differentiated Services (DiffServ). DiffServ seems to be a promising technology for next-generation IP networks supporting Quality-of-Services (QoS). Emerging applications such as IP telephony and time-critical business applications can benefit significantly from the DiffServ approach since the current Internet often can not provide the required QoS. This paper describes an implementation of Differentiated Services for Linux routers and end systems. The implementation is based on the Linux traffic control package and is, therefore, very flexible. It can be used in different network environments as first-hop, boundary or interior router for Differentiated Services. In addition to the implementation architecture, the paper describes performance results demonstrating the usefulness of the DiffServ concept in general and the implementation in particular.

Bei der Datenübertragung im Internet ist es wünschenswert, daß unterschiedliche Datenpackete unterschiedlich behandelt werden können, damit für die zeitkritischen Anwendungen wie Internet-Telefonie die größere Priorität gewährleisten könnte. Erst dann kann ein Netzbetreiber seinen Kunden verschiedene Dienstqualitäten anbieten. Zwei grundsätzliche Mechanismen existieren, um dem Netzwerk solche Anforderungen mitzuteilen: explizit, indem vor der eigentlichen Datenübertragung Kotrollnachrichten ausgetauscht werden; implizit, indem jedes Datenpacket eine Kennzeichnung erhält. Der zweite, Differentiated Services(DS), Ansatz ist Thema dieses Referates. Bei DS wird jedem Packet den sogenannten DS-Codepoint (DSCP) im IP-Header zugewiesen, und dementsprechend erfährt ein Datenpaket eine bestimmte Behandlung durch einen DS-fähigen Router. Drei unterschiedliche Dienstklassen wurde bisher spezifiziert: Best-Effort entspricht dem derzeit im Internet verwendeten Mechanismus; Premium-Service entspricht einer virtuellen Mietleitung und soll eine rasche Weiterleitung von Paketen gewährleisten; Datenpakete mit Assured Forwarding Service (AFS) sollen besser behandelt werden als Best-Effort. Bei AFS wurden insgesamt drei Verlustklassen und vier Weiterleitungsklassen definiert. Es wird auch verschiedene Typ von DS-Router vorgestellt und diskutiert. Der praktische Einsatz erfolgte bisher immer in Laborumgebung (Uni Bern, Uni Karlsruhe, EPFL, Forschungszentrum NEC Research), größere Feldversuche stehen noch aus.