Multimedia is the holy grail of networking.
When the word is mentioned,
both the propeller heads and the suits begin salivating as on cue.
The former see immense technical challenges
in providing (interactive) video on demand to every home.
The latter see equally immense profits in it.
--- Andrew S. Tanenbaum, Computer Networks, 1996
During the last years, the ever increasing power of microprocessors and the
integration of sound and video equipment enabled standard personal
computers and workstations to present or even generate digital media in
real-time: multimedia computers were born.
Until recently, multimedia computing was limited to playing back media
clips stored on bulk storage devices such as CD ROMs. However, the number
of computers connected to local networks or the world-wide Internet
increased by orders of magnitude, and this process will probably continue
in the future. The usage of computer networks for
the communication of multimedia data, promises lots of new possibilities of
people-to-people and people-to-machine communication. New kinds of
applications are arising, including remote representation, distributed
multimedia information systems, or video-on-demand services.
From a technical point of view, multimedia networking consists mainly of the transmission of multimedia data streams. Consequently, network systems become subject to the real-time requirements inherent in multimedia data. Hence, standardized mechanisms must be deployed all over a network to ensure the timely delivery of time-based data. Additionally, new transport protocols have to be developed, which support the transmission of time-critical data such as multimedia data streams.
Moreover, appropriate protocol solutions are required by distributed multimedia applications for the exchange of control and management information
Particularly exacting demands must be made on the design of the distributed multimedia applications themselves. Such a design must offer general but powerful abstractions, must be universally applicable, easily expandable, flexible, modular, and must permit efficient implementation. The object-oriented paradigm, incorporating object-oriented analysis, design, and programming methods, facilitates and supports such development goals.
The goals of this thesis are, therefore,
The remainder of this thesis is organized in the following chapters:
In Chapter 
, I will investigate into the general requirements of
distributed multimedia applications and examine multimedia data streams
particularly with respect to their time constraints.
During the course of Chapter , I will present various
techniques and protocols developed by the Internet Engineering Task Force
in connection with the transmission of multimedia data. In particular, I will
discuss the structure and suggested usage of the Internet Integrated
Services Architecture and the Resource ReSerVation Protocol (RSVP) in
Section , and review the Real-Time Transport Protocol (RTP) in
Section . Protocols that complement RSVP and RTP for certain kinds
of applications will be subject of two case studies in Section .
Multimedia data transmission and object-orientation are interconnected in
Chapter . The chapter begins with an overview of the
object-oriented paradigm, and continues with a summary of various
object-oriented approaches to multimedia application design. The
data-stream and the object-stream model are presented in more detail,
paying special attention to the integration of network communication.
Based on the considerations of the Chapters --, I
propose in Chapter an object-oriented design of an
architecture for the transmission of multimedia data streams. The design
aims to integrate the vertical, inter-application data flow into the
horizontal, intra-application data flow in a efficient and homogeneous way.
The mmstream proof-of-concept implementation of this architecture is
described in Chapter . The implementation is written in the Java
programming language and incorporates the Real-Time Transport Protocol.
Finally, Chapter summarises the ideas contained in the
Chapters --. In addition, it provides a performance
analysis of the mmstream implementation as well as a discussion of
topics of further work.