Ralf Guido Herrtwich

Media scaling for audiovisual communication with the Heidelberg transport system

HeiTS, the Heidelberg Transport System, is a multimedia communication system for real-time delivery of digital audio and video. HeiTS operates on top of guaranteed-performance networks that apply resource reservation techniques. To make HeiTS also work with networks for which no reservation scheme can be realized (for example, Ethernet or existing internetworks), we implement an extension to HeiTS which performs media scaling at the transport level: The media encoding is modified according to the bandwidth available in the underlying networks. Both transparent and non-transparent scaling methods are examined. HeiTS lends itself to implement transparent temporal and spatial scaling of media streams. At the HeiTS interface, functions are provided which report information on the available resource bandwidth to the application so that non-transparent scaling methods may be used, too. Both a continuous and discrete scaling solution for HeiTS are presented. The continuous solution uses feedback messages to adjust the data flow. The discrete solution also exploits the multipoint network connection mechanism of HeiTS. Whereas the first method is more flexible, the second technique is better suited for multicast scenarios. The combination of resource reservation and media scaling seems to be particularly well-suited to meet the varying demands of distributed multimedia applications.

Implementing HeiTS: Architecture and Implementation Strategy of the Heidelberg High-Speed Transport System

The Heidelberg High Speed Transport System (HeiTS) is a new-generation end-to-end communication system currently under development at the IBM European Networking Center (ENC) in Heidelberg. HeiTS is aimed at a heterogeneous environment comprising several computers with different operating systems and a variety of underlying local, metropolitan, and wide-area networks. It incorporates both end-system and gateway communication functions.

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.

HeiRAT: The Heidelberg Resource Administration Technique Design Philosophy and Goals

HeiRAT, the Heidelberg Resource Administration Technique, is a resource management subsystem being developed and implemented as part of a distributed multimedia platform for networked workstations.

Media scaling in a multimedia communication system

HeiTS, the Heidelberg Transport System, is a multimedia communication system for real-time delivery of digital audio and video. HeiTS operates on top of guaranteedperformance networks that apply resource reservation techniques. To make HeiTS also work with networks for which no reservation scheme can be realized (for example, Ethernet or existing internetworks), we implement an extension to HeiTS which performs media scaling at the transport level: The media encoding is modified according to the bandwidth available in the underlying networks. Both transparent and nontransparent scaling methods are examined. HeiTS lends itself to implement transparent temporal and spatial scaling of media streams. At the HeiTS interface, functions are provided which report information on the available resource bandwidth to the application so that nontransparent scaling methods may be used, too. Both a continuous and discrete scaling solution for HeiTS are presented. The continuous solution uses feedback messages to adjust the data flow. The discrete solution also exploits the multipoint network connection mechanism of HeiTS. Whereas the first method is more flexible, the second technique is better suited for multicast scenarios. The combination of resource reservation and media scaling seems to be particularly well suited to meet the varying demands of distributed multimedia applications.

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.

The Role of Performance, Scheduling and Resource Reservation in Multimedia Systems

We have identified the relation between performance, scheduling, and reservation in multimedia systems. At least for some time, performance alone will not be a solution in building multimedia platforms. Regulation of resource usage by careful scheduling helps to make scarce resources useful to bring multimedia to the users today. Whether scheduling is supported by reservation mechanisms is a matter of the quality of service desired. Possible solutions range from pessimistic over optimistic to no reservation at all.

HeiTP-a transport protocol for ST-II

The Heidelberg transport protocol (HeiTP) is a transport layer protocol for multimedia communication in the Internet. HeiTP is designed to run on top of the ST-II protocol and assumes that multimedia data travel along a privileged path in which services can be guaranteed via reservation or preallocation of the resources involved in the communication. How HeiTP supports the negotiation of quality of service (QOS) parameters and multidestination connections, and how error handling is dealt with in a flexible way are addressed. A mapping of the HeiTP interface to an extended version of the X/Open Transport Interface (XTI) that supports multimedia is also presented.<<ETX>>

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.