Lars C. Wolf

Issues ofReserving Resources in Advance

Resource management offers Quality-of-Service reliability for time-critical continuous-media applications. Currently existing resource management systems provide only means to reserve resources starting with the reservation attempt and lasting for an unspecified duration. However, for several applications such as video conferencing the ability to reserve the required resources in advance is needed. This paper explains a model for resource reservation in advance. We identify and discuss issues which must be resolved in resource reservation in advance systems. Some of the possible scenarios to be considered are described and we show how the resource reservation in advance scheme can be embedded in a general architecture.

HeiRAT—quality-of-service management for distributed multimedia systems

Abstract. Multimedia systems must be able to support a certain quality of service (QoS) to satisfy the stringent real-time performance requirements of their applications. HeiRAT, the Heidelberg Resource Administration Technique, is a comprehensive QoS management system that was designed and implemented in connection with a distributed multimedia platform for networked PCs and workstations. HeiRAT includes techniques for QoS negotiation, QoS calculation, resource reservation, and resource scheduling for local and network resources.

Reservation Protocols for Internetworks: A Comparison of ST-II and RSVP

Although efforts on reservation protocols for internetworks started quite some time ago, the research community is now becoming particularly active in this area, as proved by the high interest generated by protocols such as ST-II and RSVP. These two protocols, starting from different assumptions, have the common goal of providing guaranteed communication by reserving network bandwidth. This paper provides a short comparison of the two protocols. It describes and compares their mechanisms, focusing on the data forwarding, multicast, and quality of service aspects for multimedia communication. Rather than trying to decide which protocol is superior, we have identified the classes of applications which are better supported by one or the other protocol.

Media Scaling in Distributed Multimedia Object Services

Real-time support for multimedia streams in currently installed workstation environments has been based on resource management systems that provide mechanisms for streams with guaranteed or statistical quality of service (QoS) by admission control and resource reservation. In contrast, media scaling is a technique that dynamically adapts the load of media streams to the current availability of resources. Scaling can keep media streams meaningful to the user which would break during overload situations. Instead of interrupting the service for a stream when an overload situation is encountered, the quality of the stream is gracefully degraded when the resource load situation reaches a critical state. Since media scaling is a technique that dynamically takes actual resource load into account it can easily adapt to changing situations and has the potential to keep the system in a range of optimal load. In this article we show how media scaling can be integrated in a general system support for multimedia in order to simplify the implementation of scalable applications and support their concurrent utilization of scarce resources.

The system architecture of the Heidelberg transport system

HeiTS, the Heidelberg Transport System, is designed for communication of continuous-media data. The purpose of HeiTS is the exchange of digital audio and video with quality of service guarantees. The system environment of HeiTS has to coordinate real-time and non-real-time functions. Most parts of HeiTS run in user space; it uses some kernel-based mechanisms such as a real-time CPU scheduler and device drivers. On top of HeiTS exists a control system which allows for the construction of applications controlling continuous-media streams. This paper describes the architecture of HeiTS and the mechanisms of its system environment we have implemented on AIX and OS/2 platforms.

Filtering Multimedia Data in Reservation-Based Internetworks

Multimedia applications with a large number of recipients of a single multimedia stream require support of different quality-of-service levels for different receivers. For hierarchically encoded streams, the filtering of substreams in routers has been proposed as a mechanism to achieve this goal. This paper discusses the effects and mechanisms of filtering in the context of Internet reservation protocols such as ST-II and RSVP. It introduces a new flow specification for hierarchically encoded streams and describes its processing in endsystems and routers.

Evaluation of a CPU scheduling mechanism for multimedia systems

Multimedia applications handling audio and video data have to obey time characteristics of these media types. Besides a basic functionality to express time relations, correctness with respect to time constraints requires mechanisms which lead to favoured processing of multimedia operations. CPU scheduling techniques based on the experience from real-time operating systems offer a solution and provide multimedia applications with the ability to meet time-related quality of service requirements. This paper discusses mechanisms to express time in multimedia systems and describes an implementation of a CPU scheduler designed to run under IBMs UNIX derivate AIX. The evaluation of the implementation based on measurements shows that the scheduler is able to support the time requirements of multimedia applications and that such mechanisms are indeed necessary since otherwise deadline violations occur.

A system software structure for distributed multimedia systems

Digital audio and video data are different from traditional media in their time-criticalness and high bandwidth requirements. These requirements and the fact that typical multimedia applications perform only few operations on the continuous-media data suggest the use of new techniques for data handling in distributed, integrated, digital multimedia systems. This paper proposes a system software structure which encapsulates the processing of continuous-media data into stream handlers of a real-time environment. This environment is controlled by traditional non-real-time functions for resource, buffer and continuous-media data stream management. On top of this system, distributed multimedia applications can be built.

GLASS: A Distributed MHEG-Based Multimedia System

This paper is about GLASS, a distributed multimedia system that is currently under development. The multimedia department of the IBM European Networking Center in Heidelberg, Germany, participates in the project along with other industrial and university partners. GLASS is an acronym for Globally Accessible Services, expressing the systems wide range of possible applications. Interactive TV scenarios can be presented as well as multimedia applications for interactive learning and games for entertainment. Clients for standard telecommunications services like FAX and E-mail can be included as well as presentation components providing access to hypertext-oriented internet services like WWW. The systems components can be highly distributed using networks with TCP/IP. An application is driven by MHEG-encoded presentations that allow for the definition of sophisticated presentations. The system comprises multiple server and client components. All components can be operated on a mix of different platforms. Although running on different operating systems, all clients have the same look and feel which is defined completely by the MHEG presentation.

CPU Utilization of Multimedia Processes: HeiPOET - The Heidelberg Predictor of Execution Times Measurement Tool

Due to the time characteristics of audio and video data, the processing of multimedia applications has to be done using real-time mechanisms. Scheduling algorithms used within such systems require information about the processing time requirements, the CPU utilization of the applications, to perform schedulability tests. Since multimedia applications are often constructed by combining processing modules (often called stream handlers), processing time determination for these modules is required. The multitude of these modules and the large variety of computer systems calls for a measurement tool. In this paper we define the term CPU utilization for multimedia processing and describe the CPU utilization measurement tool HeiPOET. The presented measurements show that the tool provides measurement results with good accuracy.