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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.
ATM virtual studio services
(1996)
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.
An increasing number of applications include real-time audio streaming over a communication network. Well-known examples are teleconferencing, tele-presentation, Internet Radio live streams and on-demand services. In cooperation with various broadcasters, GMD provides live and on-demand audio services over the Internet. Applications are based on commercial products as well as on own software developments. This paper describes some approaches to provide a real-time audio service over the Internet, discusses problems and experiences and presents an outlook for a streaming service in the future.
Meshed wireless back-haul networks are seen as an affordable technology to bring Internet connectivity into rural and previously unconnected regions. To date, the main focus is to provide access to classical services such as theWWWor email. Access to such services requires the users to use a personal computer or a recent smart phone. Especially in developing regions, the prevailing end user device is a mobile phone. In order to connect mobile phones to an IP-based back-haul network, the network access points must provide a mobile phone air interface which is usually based on GSM or UMTS. In order to avoid dependence on a costly 3GPP infrastructure, we propose to deploy GSM or 3GPP nano cells in order to terminate the mobile phone protocols immediately at the mesh access points. Hence, the voice or data traffic can be carried over IP-based networks using open protocols such as SIP and RTP.
This work describes extensions to the well-known Distributed Coordination Function (DCF) model to account for IEEE802.11n point-to-point links. The developed extensions cover adaptions to the throughput and delay estimation for this type of link as well peculiarities of hardware and implementations within the Linux Kernel. Instead of using simulations, the approach was extensively verified on real-world deployments at various link distances. Additionally, trials were conducted to optimize the CWmin values and the number of retries to maximize throughput and minimize delay. The results of this work can be used to estimate the properties of long-distance 802.11 links beforehand, allowing the network to be planned more accurately.
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.
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.
