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Über dieses Buch

The advent of multimedia technology is creating a number of new problems in the fields of computer and communication systems. Perhaps the most important of these problems in communication, and certainly the most interesting, is that of designing networks to carry multimedia traffic, including digital audio and video, with acceptable quality. The main challenge in integrating the different services needed by the different types of traffic into the same network (an objective that is made worthwhile by its obvious economic advantages) is to satisfy the performance requirements of continuous media applications, as the quality of audio and video streams at the receiver can be guaranteed only if bounds on delay, delay jitters, bandwidth, and reliability are guaranteed by the network. Since such guarantees cannot be provided by traditional packet-switching technology, a number of researchers and research groups during the last several years have tried to meet the challenge by proposing new protocols or modifications of old ones, to make packet-switching networks capable of delivering audio and video with good quality while carrying all sorts of other traffic. The focus of this book is on HeiTS (the Heidelberg Transport System), and its contributions to integrated services network design.
The HeiTS architecture is based on using the Internet Stream Protocol Version 2 (ST-II) at the network layer. The Heidelberg researchers were the first to implement ST-II. The author documents this activity in the book and provides thorough coverage of the improvements made to the protocol. The book also includes coverage of HeiTP as used in error handling, error control, congestion control, and the full specification of ST2+, a new version of ST-II. The ideas and techniques implemented by the Heidelberg group and their coverage in this volume apply to many other approaches to multimedia networking.

Inhaltsverzeichnis

Frontmatter

Multimedia Communications

Frontmatter

Chapter 1. Introduction

Abstract
Communication systems of the next decades will need to face a series of new challenges to support newly emerging requirements and to provide increasingly sophisticated services to their users. The proliferation of low-cost personal computers and workstations and the integration of multimedia capabilities into today’s systems call for a wide variety of new distributed applications and services that can fully exploit the potential of digital audio and video in a computer environment.
Luca Delgrossi

Chapter 2. Multimedia Communication Elements

Abstract
In the previous chapter, we have briefly presented a multimedia communication scenario and highlighted the need for new techniques that can accommodate the requirements of distributed multimedia applications. Starting from this point, we now discuss in further details this scenario and the imposed requirements, with the intent to explore the fundamental techniques that can be adopted to facilitate the exchange of multimedia data.
Luca Delgrossi

Chapter 3. The Internet Stream Protocol

Abstract
ST, the Internet Stream Protocol, is perhaps the oldest communication protocol designed for speech communication over packet-switched networks. It has been developed by Danny Cohen, Estil Hoversten, and Jim Forgie of the M.I.T. Lincoln Laboratory. Jim Forgie is the author of the ST protocol specifications completed in September 1979 [Forg79]. In the following sections we refer to this protocol as ST-I, to avoid confusion with its second version, ST-II (see Section 3.2).
Luca Delgrossi

Chapter 4. Implementing the ST-II Protocol

Abstract
Since its design in 1990 ST-II has been implemented by several vendors and research institutes, and versions of the protocol exist that run on the most widespread platforms, operating systems, and subnetworks. Recently, a survey by Chip Elliott [ElLy93] listed at least 13 existing ST-II implementations.
Luca Delgrossi

Network Layer Techniques

Frontmatter

Chapter 5. Receiver-Oriented Communication

Abstract
The ST-II communication philosophy is sender-oriented. Once an application intends to set up a stream, it has to inform the ST agent at the origin. All manipulations of the target set are initiated and controlled by the origin ST agent. For instance, adding a set of targets, removing a set of targets, and changing the FlowSpec can be initiated by the origin only. Targets are allowed to accept or refuse changes or can disconnect themselves from the stream, but they cannot change the stream’s target set. These decisions in the design of ST-II make it a sender-oriented protocol.
Luca Delgrossi

Chapter 6. Filtering Hierarchical Substreams

Abstract
Several distributed multimedia applications such as video conferencing or video lectures must support multiple receivers. For applications with many participating receivers, and for applications that transmit their data across a wide geographical range, there exists a need to support receivers and intermediate transmission paths with different capabilities.
Luca Delgrossi

Chapter 7. Inter-Stream Relationships

Abstract
Distributed multimedia applications exploit continuous data streams to deliver digital audio and video information over the network. In this communication scenario, the transport system has to provide certain real-time guarantees to such streams in order to serve the applications with the required quality of service. There is also a requirement for multicast capabilities, i.e., the streams have to be able to convey the data simultaneously to multiple destinations. In general, the applications need to create and make use of a fairly large number of these multicast real-time streams: in a video conferencing application, for instance, each speaker has to be connected to all the participants.
Luca Delgrossi

Chapter 8. A Comparison with RSVP

Abstract
This chapter provides a short comparison of ST-II with another prominent internetworking reservation protocol: the Resource Reservation Protocol (RSVP) [ZDES93]. The internal details of ST-II and RSVP are analysed, focusing on the data forwarding, multicast, and quality of service aspects of multimedia communication. Rather than trying to decide which protocol is superior, the goal has been to identify the classes of applications that are better supported by one or the other protocol.
Luca Delgrossi

Transport Layer Techniques

Frontmatter

Chapter 9. HeiTP: A Transport Layer over ST-II

Abstract
ST-II offers at the network layer a larger set of functions than other network protocols. Still, some important functions are missing that call for a transport service above it, and the service offered by ST-II needs to be completed by appropriate functions at the transport layer.
Luca Delgrossi

Chapter 10. Reliability and Congestion Control

Abstract
The reliability a multimedia stream needs for transmission depends on the kind of media, the encoding of the media (and perhaps the hardware compressing and decompressing it), and the user requirements on media quality. On a superficial level, it looks as if audiovisual data does not require error handling mechanisms at all: a corrupt audio sample or a wrong video frame portion may not even be noticed because of the high data presentation rate.
Luca Delgrossi

Chapter 11. Conclusion

Summary
The new requirements in terms of real-time services imposed by emerging multimedia applications are the essential motivation behind the design of reservation protocols. These protocols are often called setup protocols because they are used to build real-time channels associated with the subsequent data transmission. Setup protocols are today still experimental, as experimental are many of the techniques that they adopt. We intended to explore these techniques and the way they are embedded in real setup protocols by designing, realizing, and experimenting with innovative mechanisms and functions.
The protocol implementation described in this thesis is relevant because all protocol functions are coupled with appropriate resource management functions. Experimentation with this implementation served to better understand the interactions among these two fundamental components. Here, those that are believed to be the main results of this work are shortly summarized.
Luca Delgrossi

Backmatter

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